Bifunctional ZnIILnIII dinuclear complexes combining field induced
SMM behaviour and luminescence: Enhanced NIR lanthanide
emission by 9-anthracene carboxylate bridging ligands.
María A. Palacios,a Silvia Titos-Padilla,a José Ruiz,a Juan Manuel Herrera*,a Simon J. Pope,b
Euan K. Brechin,c and Enrique Colacio*,a
a
Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada. Avda.
Fuentenueva s/n, 18071-Granada, Spain.
b
Cardiff School of Chemistry, Cardiff University, Cardiff, CF10 3AT, United Kingdom
c
EaStCHEM School of Chemistry. The University of Edinburgh, West Mains Road, Edinburgh, EH9
3JJ, UK.
Abstract
Thirteen new dinuclear ZnII-LnIII complexes of general formulae [Zn(μ-L)(μOAc)Ln(NO3)2] (LnIII = Tb (1), Dy (2), Er (3) and Yb (4)), [Zn(μ-L)(μ-NO3)Er(NO3)2] (5),
[Zn(H2O)(μ-L)Nd(NO3)3]·2CH3OH (6), [Zn(μ-L)(μ-9-An)Ln(NO3)2]·2CH3CN (LnIII = Tb (7),
Dy (8), Er (9), Yb(10)),
[Zn(μ-L)(μ-9-An)Yb(9-An)(NO3)3]·3CH3CN (11), [Zn(μ-L)(μ-9-
An)Nd(9-An)(NO3)3]·2CH3CN·3H2O
(12)
and
[Zn(μ-L)(μ-9-
An)Nd(CH3OH)2(NO3)]ClO4·2CH3OH (13) were prepared from the reaction of the
compartmental
ligand
N,N’,N’’-trimethyl-N,N’’-bis(2-hydroxy-3-methoxy-5-
methylbenzyl)diethylenetriamine (H2L), with ZnX2·nH2O (X = NO3- or OAc-) salts,
Ln(NO3)3·nH2O and, in some instances, 9-Anthracenecarboxylate anion (9-An). In all these
complexes, the ZnII ions invariably occupy the internal N3O2 site whereas the LnIII ions show
preference for the O4 external site, giving rise to a Zn(-diphenoxo)Ln bridging fragment.
Depending on the ZnII salt and solvent used in the reaction, a third bridge can connect the ZnII
and LnIII metal ions, giving rise to triple-bridged diphenoxoacetate in complexes 1-4,
diphenoxonitrate in complex 5 and diphenoxo(9-anthracenecarboxylate) in complexes 8-13.
DyIII and ErIII complexes 2, 8 and 3, 5 respectively, exhibit field induced single molecule
magnet (SMM) behavior, with Ueff values ranging from 11.7 (3) to 41(2) K. Additionally, the
solid-state photophysical properties of these complexes are presented showing that ligand L2- is
able to sensitize TbIII and DyIII-based luminescence in the visible region through an energy
transfer process (antenna effect). The efficiency of this process is much lower when NIR
emitters such as ErIII, NdIII and YbIII are considered. When the luminophore 9-Anthracene
carboxylate is incorporated into these complexes, the NIR luminescence is enhanced which
probes the efficiency of this bridging ligand to act as antenna group. Complexes 2, 3, 5 and 8
can be considered as dual materials as they combine SMM behavior and luminescent properties
INTRODUCTION
Lanthanide coordination compounds have been the subject of intense research activity,
especially due to their interesting magnetic and photo-physical properties.1, 2 Their magnetic
properties arise from the unpaired electrons in the inner f orbitals, which are very efficiently
shielded by the fully occupied 5s and 5p orbitals and therefore interact very poorly with the
ligand electrons. Because the ligand effects are very weak, most Ln III complexes exhibit large
and unquenched orbital angular momentum and consequently large intrinsic magnetic
anisotropy and large magnetic moments in the ground state. Bearing this in mind, researchers
have focused their attention toward lanthanide (and actinide) containing complexes, which
could eventually behave as single-molecule magnets (SMMs)3 or low temperature molecular
magnetic coolers (MMCs).4 SMMs show slow relaxation of the magnetization and magnetic
hysteresis below the so-called blocking temperature (TB), and have been proposed as potential
nanomagnets for applications in molecular spintronics,5 ultra-high density magnetic
information storage 6 and quantum computing at molecular level.7 The driving force behind the
enormous increase of activity in the field of SMMs is the prospect of integrating them in nanosized devices.8 MMCs show an enhanced magneto-caloric effect (MCE), which is based on the
change of magnetic entropy upon application of a magnetic field and can potentially be used
for cooling applications via adiabatic demagnetisation. Both SMMs and MMCs require a largespin multiplicity of the ground state (ST), because in the former the energy barrier () that
avoids the reversal of the molecular magnetization depends on S2, whereas in the latter the
magnetic entropy is related to the spin by the expression Sm = Rln(2S+1). However, the local
anisotropy of the heavy Ln III ions play opposing roles in SMMs and MMCs. While highly
anisotropic LnIII ions (especially DyIII) favour SMM behaviour, MMCs require isotropic
magnetic ions with weak exchange interactions generating multiple low-lying excited and fieldaccessible states, each of which can contribute to the magnetic entropy of the system, thus
favouring the existence of a large MCE. Therefore, polynuclear (and high magnetic density)
complexes containing the isotropic GdIII ion with weak ferromagnetic interactions between the
metal ions have been shown to be appropriate candidates for MMCs.9
As for photo-physical properties, lanthanides exhibit intense, narrow-line and long-lived (ns
or s) emissions, which cover a spectral range from the near UV to the NIR region. Because f-f
transitions are parity forbidden, the absorption coefficients are normally very low. However,
organic ligands with strongly absorbing chromophores that transfer energy to the lanthanide
can be used to circumvent that drawback (antenna effect).10 For an efficient energy transfer the
excited state of the ligand should be higher in energy than the lowest excited state of the
lanthanide. It should be noted that lanthanide complexes have been applied as luminescent
bioprobes in analyte sensing and tissues and cell imaging, as well as monitoring drug delivery.
In particular, NIR luminescent complexes are of high interest due to their electronic and optical
applications, especially for optical communications, and biological and sensor applications.11
Recently, we have designed a new compartmental ligand (H2L: N,N’,N”-trimethyl-N,N”bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylene triamine, see Figure 1) that presents two
different coordination sites: an inner site of the N3O2 type showing preference for transition
metal ions and the outer site (O4) showing preference for hard, oxophilic metal ions such as
lanthanides.12a The N3O2 pentacoordinated inner site forces metal ions with high preference for
octahedral coordination to saturate their coordination sphere with a donor atom, which can
proceed from a bridging ligand connecting the Ln and the transition metal ions. Following this
strategy, a series of MII-LnIII (MII = Mn, Ni and Co ) complexes were prepared with syn-syn
carboxylate or nitrate bridging groups connecting MII and LnIII ions.12 Moreover, the ligand
does not contain active hydrogen atoms that would promote inter-molecular hydrogen bonds
thus allowing the formation of well isolated molecules in crystal lattice, favouring SMM
behaviour. The existence of phenolic groups in this ligand assures the existence of ligandcentered electronic transitions in the near-UV, which could sensitize and enhance the emissive
properties of LnIII ions.
We,12 and others,13 have experimentally shown that the very weak JM-Ln observed for
3d/4f dinuclear complexes (MII = Cu, Ni and Co) leads to small separations of the low lying
split sublevels and consequently to a smaller energy barrier for the magnetization reversal. In
view of this, a good strategy to enhance the SMM properties of the 3d/4f aggregates would be
that of eliminating the weak MII-LnIII interactions that split the ground sublevels of the LnIII ion
by replacing the paramagnetic MII ions by a diamagnetic ion.12e,13, 14 According to this strategy,
we are now pursuing, in a first step, the synthesis of 3d/4f systems with the H2L ligand, in
which the paramagnetic MII ions have been replaced with diamagnetic ZnII. Moreover, the new
ZnII-LnIII complexes, in a similar manner to their analogous Schiff-base counterparts,15 should
exhibit interesting luminescent properties. Therefore, some of these complexes can behave as
bifunctional materials, combining SMM and luminescent properties. In a second step, we are
trying to improve the efficiency of energy transfer to the excited levels of the lanthanide ions in
these complexes by introducing a good emitting group, such as 9-Anthracene carboxylate (9An), connecting ZnII and LnIII ions.
Herein, we report the synthesis and X-ray structures of a series of ZnIILnIII dinuclear
complexes of formula [Zn(-L)(-X)Ln(NO3)2] ( X = none, NO3-, OAc-, and 9-An; LnIII = Dy,
Tb, Er, Nd, Yb). Ac magnetic susceptibility studies reveal some exhibit slow relaxation of the
magnetization. A study of their solid state photo-physical properties has also been undertaken,
especially of those complexes exhibiting emission in the NIR region (Ln III = Er, Nd, Yb), with
an enhanced NIR luminescence for the complexes containing 9-An bridging ligands discussed.
EXPERIMENTAL SECTION
General Procedures: Unless stated otherwise, all reactions were conducted in oven-dried
glassware in aerobic conditions, with the reagents purchased commercially and used without
further purification. The ligand H2L was prepared as previously described.12a
Preparation of complexes
[Zn(-L)(-OAc)Ln(NO3)2] (LnIII = Tb (1), Dy (2), Er (3), Yb(4)). A general procedure was
used for the preparation of these complexes: To a solution of H2L (56 mg, 0.125 mmol) in 5
mL of MeOH were subsequently added with continuous stirring 27 mg (0.125 mmol) of
Zn(OAc)2·2H2O and 0.125 mmol of Ln(NO3)3·nH2O. The resulting colourless solution was
filtered and allowed to stand at room temperature. After two days, well formed prismatic
colourless crystals of compounds 1 and 2, pink crystals for 3 and yellow crystals for 4, were
obtained with yields in the range 40-55%, based on Zn.
[Zn(-L)(-NO3)Er(NO3)2] (5) and [Zn(H2O)(-L)Nd(NO3)3]·2CH3OH (6). These compounds
were prepared in a 60 % yield as pink and violet crystals, respectively, following the procedure
for 1-4, except that Zn(NO3)2·6H2O (37 mg, 0.125 mmol) was used instead of Zn(OAc)2·2H2O.
[Zn(-L)(-9-An)Ln(NO3)2]·2CH3CN (LnIII = Tb (7), Dy (8), Er (9), Yb(10); 9-An = 9anthracenecarboxylate)
To a solution of H2L (56 mg, 0.125 mmol) in 5 mL de CH3CN were subsequently added
with continuous stirring 37 mg (0.125 mmol) of Zn(NO3)2·6H2O and (0.125 mmol) of
Ln(NO3)3·nH2O. To this solution was added dropwise another solution containing 28 mg of 9anthracene-carboxylic acid (0.125 mmol) and 0.125 mmol of triethylamine. The resulting
solution was filtered and the filtrate allowed to stand at room temperature for two days,
whereupon colourless crystals of compounds 7 and 8, and pink for 9, and yellow for 10 were
obtained with yields in the range 40-50% based on Zn.
[Zn(-L)(-9-An)Yb(9-An)(NO3)2]·3CH3CN (11)
To a solution of H2L (56 mg, 0.125 mmol) in 5 mL of MeOH were subsequently added
with continuous stirring 37 mg (0.125 mmol) of Zn(NO3)2·6H2O and 56 mg (0.125 mmol) of
Yb(NO3)3·5H2O. To this solution was added dropwise another methanolic solution containing
28 mg of 9-anthracene-carboxylic acid (0.125 mmol) and 0.125 mmol of triethylamine and
immediately a yellow precipitate was obtained. The precipitate was dissolved in acetonitrile
and the resulting solution filtered to eliminate any insoluble material. The filtrate was kept at
room temperature for a week affording yellow crystals of compound 11 in 32 % yield based on
Zn.
[Zn(-L)(-9-An)Nd(9-An)(NO3)2]·2CH3CN·3H2O (12). To a solution of H2L (56 mg, 0.125
mmol) in 5 mL de CH3CN were subsequently added with continuous stirring 37 mg (0.125
mmol) of Zn(NO3)2·6H2O and 55 mg (0.125 mmol) of Nd(NO3)3·6H2O. To this solution was
added dropwise another solution containing 28 mg of 9-anthracene-carboxylic acid (0.125
mmol) and 0.125 mmol of triethylamine. The resulting solution was filtered and allowed to
stand at room temperature for two days, whereupon violet crystals of 12 were obtained with a
yield of 41 % based on Zn.
[Zn(-L)(-9-An)Nd(CH3OH)2(NO3)](ClO4)·2CH3OH (13)
To a solution of H2L (56 mg, 0.125 mmol) in 5 mL of MeOH were subsequently added
with continuous stirring 46 mg (0.125 mmol) of Zn(ClO4)2·6H2O and 56 mg (0.125 mmol) of
Nd(NO3)3·5H2O. To this solution was added dropwise another methanolic solution containing
28 mg of 9-anthracene-carboxylic acid (0.125 mmol) and 0.125 mmol of triethylamine. The
resulting solution was filtered and allowed to stand at room temperature. After one week, well
formed prismatic violet crystals of 13, were obtained with a yield of 38% based on Zn.
The purity of the complexes was checked by elemental analysis (see Table S1).
Physical measurements
Elemental analyses were carried out at the “Centro de Instrumentación Científica” (University
of Granada) on a Fisons-Carlo Erba analyser model EA 1108. IR spectra on powdered samples
were recorded with a ThermoNicolet IR200FTIR using KBr pellets. Ac susceptibility
measurements under different applied static fields were performed using an oscillating ac field
of 3.5 Oe and ac frequencies ranging from 1 to 1500 Hz with a Quantum Design SQUID
MPMS XL-5 device. UV-Vis spectra were measured on a UV-1800 Shimadzu
spectrophotometer and the photoluminescence spectra on a Varian Cary Eclipse
spectrofluorometer. Lifetime data were obtained on a 75 JobinYvon-Horiba Fluorolog
spectrometer fitted with a JY TBX picoseconds photodetection module. The pulsed source was
a Nano-LED configured for 372 nm output operating at 500 kHz. Luminescence lifetime
profiles were obtained using the JobinYvon-Horiba FluoroHub single photon counting module
80 and the data fits yielded the lifetime values using the provided DAS6 deconvolution
software.
Single-Crystal Structure Determination
Suitable crystals of 1 and 3-13 were mounted on a glass fibre and used for data collection. Data
for 1 were collected with a dual source Oxford Diffraction SuperNova diffractometer equipped
with an Atlas CCD detector and an Oxford Cryosystems low temperature device operating at
100 K and using Mo-K. Semi-empirical (multi-scan) absorption corrections were applied
using Crysalis Pro. Data for for compounds 3-13 were collected with a Bruker AXS APEX
CCD area detector equipped with graphite monochromated Mo K radiation ( = 0.71073 Å)
by applying the -scan method. Lorentz-polarization and empirical absorption corrections were
applied. The structures were solved by direct methods and refined with full-matrix least-squares
calculations on F2 using the program SHELXS97.16 Anisotropic temperature factors were
assigned to all atoms except for the hydrogens, which are riding their parent atoms with an
isotropic temperature factor arbitrarily chosen as 1.2 times that of the respective parent. The
highly disordered perchlorate counteranion could not be modelled, so that a new set of F2 (hkl)
values with the contribution from the ClO4- anion withdrawn was obtained by the SQUEEZE
procedure implemented in PLATON_94.17
Final R(F), wR(F2) and goodness of fit agreement factors, details on the data collection and
analysis can be found in Tables S2. Selected bond lengths and angles are given in Tables S3.
RESULTS AND DISCUSSION
As expected, the reaction of H2L with Zn(OAc)2·2H2O and subsequently with
Ln(NO3)3·nH2O in MeOH and in 1:1:1 molar ratio led to crystals of the compounds [Zn(L)(-OAc)Ln(NO3)2] (LnIII = Tb (1), Dy (2), Er (3), Yb(4)). The same reaction but using
Zn(NO3)3·6H2O instead of Zn(OAc)2·2H2O and Ln(NO3)3·6H2O (LnIII = Nd, Er) led to two
different
Zn-Ln
dinuclear
complexes
[Zn(H2O)(-L)Nd(NO3)3]· 2CH3OH (6).
[Zn(-L)(-NO3)Er(NO3)2]·2CH3OH
(5)
and
Zn-Ln complexes, bearing an 9-anthracene
carboxylate instead of acetate connecting ZnII and LnIII ions of formula [Zn(-L)(-9An)Ln(NO3)2]·2CH3CN (LnIII = Tb (7), Dy (8), Er (9), Yb(10)) could be prepared by reacting
an acetonitrile solution containing H2L, Zn(NO3)3·6H2O and Ln(NO3)3·nH2O in 1:1:1 molar
ratio with another acetonitrile solution containing 9-anthracene carboxylic acid and Et3N in 1:1
molar ratio. Using the same reaction conditions as for complexes 1-4, YbIII leads to a yellow
powder, which after recrystallization in acetonitrile afforded the compound of formula [Zn(L)(-9-An)Yb(9-An)(NO3)2]·3CH3CN (11) having both bridging and chelating bidentate 9anthracenecarboxylate ligands, the latter coordinated to the YbIII ion. With NdIII , and using the
same reaction conditions as for complexes 7-10, only violet crystals of the compound [Zn(L)(-9-An)Nd(9-An)(NO3)2]·2CH3CN·3H2O (12), whose structure is very similar to 11, were
obtained. However, using methanol as solvent and Zn(ClO4)·6H2O instead of Zn(NO3)2·6H2O,
violet crystals of the complex [Zn(-L)(-9-An)Nd(CH3OH)2(NO3)](ClO4)·2CH3OH (13)
were obtained (see Figure 1).
Crystal Structures
A perspective view of the structures of complexes 1-13 are given in Figure 1, whereas
selected bond lengths and angles are given in Table S3.
Complex 1 is isostructural to those previously reported by us for the Ni-Ln and Co-Ln
analogues and crystallizes in the triclinic P-1 space group.12a-c The structure of 1 consists of
two almost identical dinuclear ZnII-TbIII molecules, in which the TbIII and ZnII ions are bridged
by two phenoxo groups of the L2- ligand and one syn-syn acetate anion. Compounds 3 and 4
crystallize in the monoclinic P21/n space group and its structure is very similar to that of 1 but
having only one crystallographically independent ZnII-LnIII molecule. The structure of 2 was
previously reported by us and is isostructural to that of 1. 12a
Figure 1.- Structure of the ligand H2L (center).
(i) H2L/Zn(OAc)2·2H2O/ Ln(NO3)3·nH2O,
1:1:1, in MeOH (LnIII = Tb (1), Dy (2), Er (3), Yb(4)). (ii) H2L/Zn(NO3)2·6H2O/
Ln(NO3)3·nH2O, 1:1:1, in MeOH (LnIII = Er (5), Nd (6)).
(iii) H2L/Zn(NO3)2·6H2O/
Ln(NO3)3·nH2O /9-An/Et3N. 1:1:1:1:1, in CH3CN (LnIII = Tb (7), Dy (8), Er (9), Yb(10)). (iii)
Using the same conditions as in (i) and recrystallization in CH3CN (Yb (11)). The same
conditions as in (iii) (Nd (12)). (v) H2L/Zn(ClO4)2·6H2O/ Nd(NO3)3·6H2O//9-An/Et3N, 1:1:
1:1:1, in MeOH (13)
The structures of complexes 1-4 are given in Figure 1A. In all these complexes, the ZnII
ion exhibits a slightly trigonally distorted octahedral ZnN3O3 coordination polyhedron, where
the three nitrogen atoms from the amine groups, and consequently the three oxygen atoms,
belonging to the acetate and phenoxo bridging groups, occupy fac positions. The Zn-O and ZnN distances are found in the ranges 2.037(3)Å to 2.189(2) Å and 2.164(2) Å to 2.262(2) Å,
respectively. In all complexes, the corresponding LnIII ion exhibits a LnO9 coordination
sphere, consisting of the two phenoxo bridging oxygen atoms, the two methoxy oxygen atoms,
one oxygen atom from the acetate bridging group and four oxygen atoms belonging to two
bidentate nitrate anions. The LnO9 coordination sphere is rather asymmetric, exhibiting short
Ln-Ophenoxo and Ln-Oacetate bond distances in the range 2.2 Å -2.3 Å and longer Ln-Onitrate and
Ln-Omethoxy bond distances >2.4 Å (one of the methoxy groups is weakly coordinated with LnO bond distances > 2.6 Å). As expected, the average Ln-Ophenoxo bond distances for compounds
1-4, steadily decrease from TbIII to ErIII following the lanthanide contraction, with a
concomitant decrease of the average Zn-Ln and Ln-Oacetate bond distances.
The Zn(di--phenoxo)(-acetate)Ln bridging fragment is rather asymmetric, not only
because the Ln-Ophenoxo and Zn-Ophenoxo bond distances are different, but also because there
exists two different Zn-O-Ln bridging angles with average values of 106.28° and 100.5° for
complexes 1-4.
The bridging acetate group forces the structure to be folded with the average hinge
angle of the M(-O2)Ln bridging fragment ranging from 23.39° for 1 to 22.55º for 3 (the hinge
angle, , is the dihedral angle between the O-Zn-O and O-Ln-O planes in the bridging
fragment). Therefore, the hinge angle increases with the decrease of the LnIII size, as expected.
The structure of [Zn(-L)(-NO3)Er(NO3)2]·2CH3OH (5) is isostructural with two NiLn complexes,12a,b previously reported by us and very similar to that of compounds 1-4 but
having a bridging nitrate anion connecting the ErIII and ZnII metal ions instead of an acetate
anion (see Figure 1B). Compared to complex 3, the most significant effect of the coordination
of the nitrato bridging ligand in 5 is that the Zn(-O2)Er bridging fragment is folded to a lesser
extent. Thus, the hinge angle decreases from 22.6 ° in 3 to a 14.4 ° in 5, with a simultaneous
decrease of Er-O-Zn angles at the bridging region, as well as the out-of-plane displacements of
the O-C bonds belonging to the phenoxo bridging groups from the Zn(O)2Er plane. At variance
with 3, where the acetate and metal ions are almost coplanar, in 5 the plane of the nitrate anion
and the plane containing the ZnII, ErIII and the two oxygen atoms of the nitrato bridging ligands
coordinated to the metal ions, form a dihedral angle of 28.6 °. Zn-O and Er-O bond distances,
involving the oxygen atoms of the nitrate anion in 5, are more than 0.1 Å longer than those
involving the acetate bridging group in 3. The rest of distances and angles in 5 are very close to
that found in 3 and do not deserve any further discussion.
Compound 6 was prepared using the same reaction conditions as for 5, but it does not
contain a nitrate anion connecting the NdIII and ZnII ions. This may be due to the fact that the
large NdIII ion could enforve a significant strain in the weakly bonded nitrate bridging ligand,
so that the di--phenoxo-bridged would be more favourable than the diphenoxonitrate-bridged
one. The structure of 6 is given in Figure 1C and consists of [Zn(H2O)(-L)Nd(NO3)3] neutral
molecules and two methanol molecules of crystallization, both of which are involved in
hydrogen bond interactions. As expected, the absence of a nitrate bridging group in 6 gives rise
to a more planar Zn(-O2)Nd bridging fragment with a hinge angle of 6.6º. Moreover, a water
molecule saturates the octahedral coordination sphere of the ZnII ion and, most importantly, the
coordination of one additional bidentate chelating nitrate ligand to the NdIII ion leads to an
expanded and more symmetrical NdO10 coordination sphere.
Finally, it should be stressed that 6 exhibits both intermolecular and intramolecular
hydrogen bond interactions. The former involve the molecules of methanol, the coordinated
water molecule and one of the nitrate anions belonging to two centrosymmetrically related
ZnII-NdIII molecules with donor-acceptor distances in the range 2.623 Å-2.823 Å. The latter
involve the water molecule and one of the nitrate anions of the same ZnII-NdIII moiety with
O···O distances of 2.920 Å
The structures of complexes 7-10 are shown in Figure 1D and are very similar to that of
complexes 1-4 but having a 9-anthracenecarboxylate bridging ligand instead of an acetate
ligand connecting the ZnII and LnIII ions, and with two acetonitrile molecules of crystallization.
Compared to 1-4, the acetate bridged analogues, compounds 7-10 exhibit a small hinge angle
and smaller and closer Zn-O-Dy bridging angles, resulting in a smaller degree of asymmetry in
the bridging region. One of the Dy-Omethoxy bond distances is significantly shorter than that in
complexes 1-4, leading to a less asymmetry in the DyO9 coordination sphere. The plane of the
anthracene ring is not coplanar with the corresponding plane of carboxylate group, having a
dihedral angle between these planes of ~84°. Bond distances and angles in the rest of the
molecule are very close to those observed in the acetate bridged counterparts.
Compounds 11 and 12 have very similar structures, containing two 9-anthracene
carboxylate bidentate ligands - one acting as a bridge linking the ZnII and LnIII ions and the
other one acting as a chelating ligand coordinated to the LnIII ion (Figure 1E). As with the NiIIDyIII analogue,12b these compounds crystallize in a non-centrosymmetric space group
(orthorhombic, Pca21) and therefore are examples of chiral molecules obtained from achiral
starting materials. The overall ensemble of crystals in a batch of 11 and 12 are expected to
contain crystals of both enantiomeric forms in equal amounts and therefore to be racemic. As
in compounds 7-10, the anthracene rings are not coplanar with the corresponding plane of
carboxylate group, with dihedral angles between these planes of ~89º and ~82°, for the
bridging and chelating 9-anthracene carboxylate ligands (9-An), respectively, whereas the
dihedral angle between the planes of the anthracene rings for the two 9-An ligands is ~55 º.
The Ln-O bond distances involving the oxygen atoms of the chelating 9-anthracene
carboxylato are shorter than the Ln-Onitrate ones (~ 0.1 Å), the Ln-Omethoxy are the longest and
rather different (~ 0.2 Å) and the two Ln-Ophenoxo distances are ~ 0.1 Å shorter than the LnOcarboxylate , so that the LnO9 coordination sphere is rather asymmetric.
The structure of 13 is similar to that of compounds 7-10, but one of the nitrate bidentate
ligands coordinated to the LnIII ion is replaced by two molecules of methanol that adopt a cis
configuration. The structure of 13 (see Figure 1F) consists of positive dinuclear units [Zn(L)(-9-An)Nd(CH3OH)2(NO3)]+, a perchlorate anion and two methanol molecules of
crystallization. Nd-O distances are in the range 2.30-2.69 Å and therefore the LnO9
coordination sphere is the least asymmetric in this series of ZnII-LnIII complexes. Centrosymmetrically related molecules are held in pairs by four complementary hydrogen bonds
involving one of the methanol molecules of crystallization, which forms two bifurcated
hydrogen bonds with the non-coordinated oxygen atom of the bidentate nitrate anion and one of
the coordinated methanol molecules of a neighboring unit with O···O distances of 2.977 Å and
2.651 Å, respectively.
SMM behavior
In order to know if our strategy of replacing the 3d paramagnetic ion by ZnII in
diphenoxo-bridged 3d-4f systems improves the SMM properties of this kind of compound, we
have performed dynamic ac magnetic susceptibility measurements as a function of both
temperature and frequency. Under zero-external field, only compound 8 exhibits a weak
frequency dependence of the out-of-phase signal,"M, below 10 K without a net maximum
above 2 K, even at frequencies as high as 1400 Hz (See Figure S1). This behavior indicates
that either the energy barrier for the flipping of the magnetization is not high enough to trap the
magnetization in one of the equivalent configurations above 2 K or there exists quantum
tunneling of the magnetization (QTM), leading to a flipping rate that is too fast to observe the
maximum in the "M above 2 K. The fact that "M for 8 below 4 K does not go to zero but
increase very sharply is a clear indication of the existence of QTM. This fast relaxation process
can be promoted by transverse anisotropy, dipolar and hyperfine interactions. Nevertheless, for
Kramers ions such as DyIII, the first mechanism would not facilitate the QTM relaxation
process. When the ac measurements were performed in the presence of a small external dc
field of 1000 G to fully or partly suppress the quantum tunneling relaxation of the
magnetization, the Dy compounds 2 and 8 and the Er compounds 3 and 5 showed typical SMM
behavior with maxima in the 6.75 K (1488 Hz)-4.25 K (50 Hz), 6.5 K (900 Hz)-4.25 K (50
Hz), 3 K (1400 Hz)-2.5 K (600 Hz), 2.75 K (1400 Hz)-2.2 K (400 Hz) ranges, respectively
(Figures 2 and 3).
Figure 2.- Temperature dependence of in-phase ′M (top) and out-of-phase "M (bottom)
components of the ac susceptibility for complexes 2 (left) and 8 (right) measured under 1000
Oe applied dc field.
The relaxation times, , for compounds 2, 8 and 5 were extracted from the fit of the
frequency dependence of M" at each temperature to the generalized Debye model (Figures S2S3). In the case of compound 3, that does not exhibit any maximum in the M" vs frequency
plot (the same fit as for compounds 2, 8 and 5 does not lead to reliable values of ), the
temperatures and frequencies of the maxima in the M" vs T plot were used to extract the
relaxation times. The results were then used in constructing the Arrhenius plot,  = 0
exp(/kBT), shown in Figures S2-S3. The fit of the high temperature linear portions of the data
afforded the effective energy barriers for the reversal of the magnetization  and o values
indicated in Table 1. The Arrhenius plots, constructed from the temperatures and frequencies
of the maxima observed for the "M signals in Figures 2 and 3 for compounds 2, 5 and 8 lead
virtually to the same  and  (flipping rate) parameters, as expected. The fact that the out-of-
phase susceptibility for these compounds tends to zero after the maxima is a clear indication
that the QTM is suppressed. Only for compound 3 is the suppression of the QTM incomplete,
which may be due to the existence of significant intermolecular interactions. In some cases, the
effects of these interactions, that favour the fast QTM process, cannot be eliminated by
application of a small magnetic dc field.
The Cole-Cole diagrams for these complexes are shown in Figure S4. The Cole-Cole
plots for complexes 2, 5 and 8 are rather symmetrical and in the high temperature regions
corresponding to the linear portion of the data in the Arrhenius plots they exhibit semicircular
shapes with  values in the ranges 0.02 (8 K)-0.10 (5 K), 0.1(3 K)-0.15 (2.2 K), 0.06 (6.75 K)0.19 (5 K) for 2, 5 and 8, respectively. These low values indicate very narrow distribution of
slow relaxation in these regions, which would be compatible with the existence of only one
relaxation process. In the case of 3 the Cole-Cole diagram is non-symmetrical with  values
are in the range 0.06 (3 K)-0.29 (2.4 K), thus indicating that the crossover from the thermally
activated relaxation process to a quantum regime occurs below ~2.6 K.
Table 1. andvalues for compounds 2, 3, 5 and 8.
Compound
”M signal
at H = 0 Oe
at H = 1000 Oe 0 (s)
2
yes
41(2)
5.6·10-7
3
no
11.7(3)
2.0·10-6
5
no
22(2)
5.3·10-8
8
no
32.1(3)
1.9·10-6
The values of /kB found for 2 and 8 are near the center of the range experimentally
observed for for mono and polynuclear Dy SMMs.1e It should be noted that the
maximum value of  found for MII-DyIII ( MII = Ni and Co) compounds isostructural to
2 and 8 was 19.2 K.12a-c Therefore, these results support the conclusion that replacement
of the paramagnetic MII metal ion by ZnII can be an appropriate strategy to improve the
SMM properties in diphenoxo-bridged 3d-4f systems. Complexes 2 and 8 exhibit very
similar LnO9 coordination spheres with a poorly defined geometry as they are
intermediate between several nine-vertex polyhedra (see ESI). Previous ab initio
calculations on a Dy fragment of a Co-Dy compound isostructural to 2 clearly showed
that the ground Kramers doublet arising from the ligand-field splitting of the 6H15/2
ground atomic term shows strong axial anisotropy with gz =18.9 (gx = 0.06 and gy =
0.09) along the main anisotropy axis, which lies close to the Dy–Co direction.12c The
large axial anisotropy of the DyIII ion in compounds 2 and 8 must therefore be at the
origin of their SMM behavior. Notice that axial ligand fields induce strong easy axis
anisotropy of DyIII because it has an oblate electron density.1a This ligand field
anisotropy is easy to achieve accidentally and this is the reason why a wide variety of
DyIII-containing SMMs have been reported. In this regard, the ligand field created by
the nine oxygen atom of the LnO9 coordination sphere is not axial, however 2 and 8
still present strong axial anisotropy and SMM behavior.
It should be noted that ErIII based SMMs are rare and, as far as we know, only
three such examples have been reported. One of them, Na9[Er(W5O18)2]·xH2O18 (the
ErIII ion is encapsulated between two diamagnetic polyoxometalate cages) exhibits
SMM behavior at zero field with a thermal energy barrier of 55.3 K. The other two are
Zn3Er complexes of very similar hexaimine planar macrocyclic ligands with six oxygen
atoms bridging the ZnII and ErIII ions.19 The former displays a flattened D4d
antiprismatic LnO8 coordination sphere leading to a MJ = ± 13/2 ground state that is
separated from the first excited state by ~30 cm-1, whereas the other two have LnO919a
and suspected LnO1019b coordination spheres that conserve a strong equatorial ligand
field. ErIII has prolate electron density1a and, to generate single-ion anisotropy and SMM
behavior, an equatorial ligand field is, in principle, required. The two Zn3ErIII
complexes are examples of systems having this kind of ligand field, whereas the ErPOM system exhibits a ligand field that can be considered as intermediate between axial
and equatorial. For complexes 3 and 5, with LnO9 coordination spheres very similar to
that of 2 and 8, the absence of a clear axial field can allow an easy-axis anisotropy
leading to the observed SMM behavior.
Figure 3.- Temperature dependence of in-phase ′M (top) and out-of-phase "M (bottom)
components of the ac susceptibility for complexes 3 (left) and 5 (right) measured under 1000
Oe applied dc field.
Photophysical properties.
In the last few years, several examples of lanthanide complexes coordinated by
compartmental Salen-type Schiff-base ligands have been reported to exhibit interesting
photophysical properties. These ligands act as antenna groups, sensitizing LnIII-based
luminescence through an intramolecular energy transfer process.15 Considering the
similarity between ligand H2L and those Salen-derivates, the photophysical properties
of samples 1 – 6 have been studied to determine the ability of ligand L2- to act as
sensitizer. The photophysical properties of complexes 7 – 13, which additionally
contain 9-anthracene carboxylate ligands in their structure, have also been analyzed.
The reflectance spectrum of ligand H2L (Figure S5) shows intense absorption bands in
the UV region located at 240 and 290 nm, which are typical of intraligand π-π*
electronic transitions in the aromatic groups. Excitation at 290 nm resulted in the
appearance of a weak ligand-centered emission (Fig. S5, inset) with a maximum located
at λem = 391 nm and a shoulder located at higher energy (λem = 365 nm).
The 9-Anthracene carboxylate ligand is a well-known luminophore and
anthracene derivates have been previously used as antenna groups to sensitize LnIIIbased luminescence in the NIR region.20 This ligand shows characteristic π-π*
absorption bands that extend well into the visible region and displays an intense and
broad emission band centered at c.a. 500 nm.
In all cases, we examined the emissive properties of the complexes as
microcrystalline powders, their poor solubility preventingdetailed study of their
photophysical properties in solution.
Firstly, we examined the emissive properties of complexes 1 and 2 where the
respective TbIII and DyIII ions are potential emitters in the visible region which can be
sensitized by an energy transfer from the L2- ligand. In both cases, excitation into the
UV π-π* absorption band of ligand L2- at 290 nm resulted in the appearance of the
characteristic TbIII (5D4→7FJ; J = 3, 4, 5, 6) and DyIII (4F9/2→6HJ/2; J = 15/2, 13/2)
emission bands in the visible region respectively (Figure 4). This sensitized LnIII-based
emission can only occur through a L→Ln photoinduced energy transfer process, which
probes the ability of ligand L2- to act as an antenna group. However, a significant
residual ligand-centered emission is still observed which indicates that the energy
transfer process is not complete.
(a)
(b)
Figure 4. (a) Sensitized emission spectra of complexes 1 (green) and 2 (blue) in the
solid state at room temperature. (b) Jablonski’s diagram of complexes 1 and 2;
approximate energy values of S1 and T1 were determined from the UV-Vis absorption
and emission spectra of ligand H2L.
Similarly, the photophysical properties of samples 7 and 8 were studied. Both
complexes contain the bridging ligand 9-anthracene carboxylate directly linked to the
lanthanide ions. In these cases, excitation of the complexes into the UV absorption
manifold of the 9-anthracene carboxylate unit (λex. = 355 nm) did not result in sensitized
LnIII emission in the visible region. In both cases, only the characteristic emission of the
anthracene moiety was observed. This is due to the fact that the energy of the emissive
3
ππ* state is lower than that of the emissive 5D4 and 4F9/2 excited states of ions TbIII and
DyIII respectively.
Regarding the expected sensitized near-infrared emission characteristic of ions
ErIII (4I13/2→4H15/2; λem = 1530 nm) in 3 and 5, YbIII (2F5/2→2F7/2) in 4 and NdIII
[4F3/2→4FJ; J = 11/2 (λem = 1060 nm), 13/2 (λem = 1340nm)] in 6, only the emission
characteristic of YbIII ions in 4 was observed (Figure S6) when the compound was
excited at 290 nm, which indicates the low efficiency of ligand L2- to act as antenna
group for these ions. This is probably due to the poor spectroscopic overlap existing
between the ligand emission and the f-f excited states of ions ErIII, NdIII and YbIII that
could act as energy acceptors. Nevertheless, time-resolved luminescent experiments
performed on these samples using a Nd:YAG excitation source with λex = 355 nm,
allowed us to determine the emission lifetime characteristic of ions Er III, NdIII and YbIII
in these samples. These lifetimes, obtained after fitting the luminescent decay curve
mono-exponentially, are collected in Table 2 and their values are within those
commonly observed for Nd(III), ErIII) and YbIII molecular complexes, typically 2 μs for
ErIII, 1 μs for NdIII and 10 μs for YbIII.21
Table 2. Luminescence Lifetimes of the solid samples 3 – 6 and 9-13.a
complex
τ(μs)
complex
τ(μs)
2.08
2.77
3
9
10.3
6.86
4
10
0.47
11.82
5
11
2.14
0.80
6
12
1.12
13
aMeasured at room temperature using 355 nm excitation.
This demonstrates that ligand L2- sensitizes LnIII-based emission, although the
efficiency of the energy transfer process is rather low. To improve the NIR LnIII-based
emissive properties of this kind of molecule, the organic ligand 9-anthracene
carboxylate was introduced as a bridging ligand in complexes 9 – 13. In addition, for
samples 11 and 12, a second anthracene unit is directly chelated to the lanthanide ion.
As expected, in all these cases, excitation at 355 nm resulted in the appearance of
intense sensitized NIR emission from ions ErIII (9), NdIII (12, 13) and YbIII (10, 11) at
their characteristic wavelengths (Figure 5).
(a)
(b)
Figure 5. (a) NIR sensitized emission spectra of complexes 9 (green) and 10 (blue) and
12 (red) in the solid state at room temperature. (b) Jablonski diagram for these
complexes; approximate energy values of S1 and T1 were determined from the UV-Vis
absorption and emission spectra of ligand 9-Anthracene carboxylic acid.
These results confirm that the use of 9-Anthracene carboxylate ligands as
bridging and/or chelate ligands directly coordinated to the LnIII ions significantly
improves their NIR luminescent properties.
Conclusions.
We have demonstrated that the compartmental ligand H2L (N, N’, N’’-trimethylN,N’’-bis(2-hydroxy-3-methoxy-5-methylbenzyl)-diethylenetriamine)
allows
the
preparation of four series of dinuclear ZnII-LnIII complexes, in which the ZnII ion
occupies the internal N3O2 site and the oxophylic LnIII ion occupies the external O4 site,
leading to diphenoxo-bridged species. The sixth position in the ZnII coordination sphere
is occupied by either a water molecule or the oxygen atom belonging to acetate, nitrate
or 9-anthracenecarboxylate bridging groups, leading to doubly-bridged diphenoxo or
triply
bridged
diphenoxo-acetate,
diphenoxo-nitrate
and
diphenoxo-antracene
carboxylate complexes, respectively. Dynamic ac magnetic susceptibility measurements
as a function of temperature and frequency show that the DyIII complexes 2 and 8 and
the ErIII derivates 3 and 5 exhibit field-induced SMM behavior with effective thermal
energy barriers of 41 K, 32.1 K, 11.7 K and 22 K respectively. These are larger than
those found for isostructural complexes with paramagnetic 3d ions such as NiII, and
CoII, suggesting that the replacement of paramagnetic ions by diamagnetic ions is one
strategy for increasing Ueff in 3d/4f systems. The increase in Ueff appears to due to the
elimination of the weak magnetic exchange coupling between 3d and 4f ions that leads
to a small energy separation between the ground and first excited state. Moreover, we
believe that, as observed in other systems containing diamagnetic ions, the existence of
a diamagnetic ZnII ion linked to the LnIII ions mitigates the intermolecular interactions
between the LnIII, thus diminishing the QTM process and favoring the observation of
slow relaxation of the magnetization. Complexes 3 and 5 are very rare examples of ErIIIcontaining SMMs.
Finally, the photophysical properties of these complexes have been studied and
the ability of the ligand L2- to sensitize TbIII and DyIII-based luminescence in the visible
region has been demonstrated. For complexes 1 and 2, excitation of the ππ* absorption
of the ligand results in concomitant sensitized emission in the visible region from the
TbIII and DyIII units respectively. However, the efficiency of this ligand to sensitize the
characteristic emission from ErIII, NdIII and YbIII ions in the NIR region is rather low
due to the poor spectroscopic overlap existing between the ligand emission and the f-f
excited states of these ligands. NIR emission in this kind of system was enhanced by
introducing 9-Anthracene carboxylate luminophores as bridging and/or chelating
ligands coordinated to the lanthanide ions.
DyIII complexes 2 and 8 and ErIII complexes 3 and 5 combine field-induced
SMM behavior and luminescent properties, and therefore can be considered as examples
of dual magnetic-luminescent materials.
ASSOCIATED CONTENT
Elemental analyses for all the complexes, X-ray crystallographic data for 1, 3-13,
including data collection, refinement and selected bond lengths and angles. Variabletemperature frequency dependence of the ac out-of-phase χM" signal for complexes 2, 5
and 8, Cole-Cole plots for complexes complexes 2, 3, 5 and 8, reflectance spectrum of
the ligand and photoluminisence spectrum of compound 4. This material is available
free of charge via the Internet at http://pubs.asc.org.
AUTHOR INFORMATION
Corresponding Author
*Email: ecolacio@ugr.es
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
Financial support from the Spanish Ministerio de Ciencia e Innovación (MICINN)
(Project CTQ-2011-24478), the Junta de Andalucía (FQM-195, the Project of
excellence P11-FQM-7756), and the University of Granada is acknowledged. S. T.-P.
thanks the Junta de Andalucía for a research grant. EKB thanks the EPSRC for funding.
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Electronic supplementary information
Table S1.- Elemental analyses for complexes 1-13
Compound
Formula
Mw
1
C27 H40 N5 O12 Zn Tb
850.93
2
C27 H40 N5 O12 Zn Dy
854.51
37.95
(37,90)
4.72
(4.67)
8.20
(8.37)
3
C27 H40 N5 O12 Zn Er
859.27
37.74
(37.70)
4.69
(4.61)
8.15
(8.24)
4
C27 H40 N5 O12 Zn Yb
865.05
37.49
(37.55)
4,66
(4.73)
8.10
(8.20)
5
C25 H37 N6 O13 Zn Er
862.24
34.82
(34.90)
4.33
(4.41)
9.75
(9.90)
6
921.32
35.20
(35.31)
5.14
(5.30)
9.12
(9.01)
7
C27 H47 N6 O16 Zn Nd
C44 H52 N7 O12 Zn Tb
48.25
(48.40)
4.78
(4.91)
8.95
(9.07)
8
C44 H52 N7 O12 Zn Dy
1095.22
1098.80
48.10
(48.15)
4.77
(4.83)
8.92
(9.00)
9
C44 H52 N7 O12 Zn Er
1103.56
47.89
(47.80)
4.75
(4.76)
8.88
(8.98)
10
C44 H52 N7 O12 Zn Yb
47.64
(47.53)
4.73
(4.75)
8.84
(8.80)
11
C61 H64 N7 O11 Zn Yb
1109.34
1309.60
55.94
(55.90)
4.93
(5.00)
7.49
(7.44)
12
C59 H67 N6 O14 Zn Nd
C44 H62 N4 O17 Cl Zn
Nd
1293.83
54.77
(54.86)
5.22
(5.30)
6.50
(6.60)
45.40
(45.48)
5.37
(5.45)
4.81
(4.90)
13
1164.07
% Cteor (% Cexp)
38.11
(38.04)
% Hteor (% Hexp) % Nteor (% Nexp)
4.74
(4.65)
8.23
(8.30)
Table S2.- Crystalllographic data for compounds 1-13
3
1
C27H40N5O12Zn
Tb
4
C27H40N5O12Zn C27H40N5O12Zn
Er
Yb
5
C25H37N6O13Zn
Er
6
C27H47N6O16Zn
Nd
7
C44H52N7O12ZnT
b
Mr
Crystal
system
Space group
(no.)
850.93
859.27
865.05
862.24
921.32
1095.22
Triclinic
Monoclinic
Monoclinic
Orthorhombic
Monoclinic
Monoclinic
P-1 (2)
P21/n (14)
P21/n (14)
P212121 (19)
P21/c (14)
P21/n (14)
a (Å)
11.45081(14)
11.345(5)
11.3197(7)
10.7276(5)
10.686(5)
13.546(5)
b (Å)
14.77726(18)
14.542(5)
14.5238(9)
15.8243(7)
17.785(5)
23.332(5)
c (Å)
19.3346(2)
20.078(5)
20.1539(12)
17.8958(8)
20.049(5)
14.885(5)
a (°)
92.6221(10)
90.000(5)
90.00
90.00
90.000(5)
90.000(5)
β (°)
98.4836(10)
101.407(5)
101.7910(10)
90.00
102.148(5)
102.616(5)
γ (°)
90.9880(10)
90.000(5)
90.00
90.00
90.000(5)
90.000(5)
V (Å3)
3231.50(7)
3247(2)
3243.5(3)
3037.9(2)
3725(2)
4591(2)
Z
4
4
4
4
4
4
Dc (g cm )
(MoK)
(mm-1)
1.749
1.758
1.771
1.885
1.639
1.585
3.609
2.098
T (K)
Observed
reflections
100(2)
100(2)
100(2)
100(2)
16275 (13145)
5689 (5178)
5346 (5086)
6560 (5982)
Rint
0.0403
0.0323
0.0256
0.0302
0.0351
0.0268
Parameters
844
423
423
422
471
595
GOF
0.979
1.055
1.109
1.063
0.0310
(0.0281)
0.0700
(0.0683)
1.057
0.0269
(0.0240)
0.0576
(0.0557)
0.823
0.0363
(0.0260)
0.0566
(0.0549)
0.0272
(0.0253)
0.0627
(0.0609)
0.0388
(0.0347)
0.0880
(0.0849)
1.354 and 0.875
2.947 and 1.033
1.394 and 0.522
1.318 and 0.422
1.453 and 0.767
1.198 and -0.328
11
C61H64N7O11Zn
Yb
12
C59H67N6O14Zn
Nd
13
C44H62N4O17ClZn
Nd
1309.60
1293.83
1164.07
Compound
Formula
-3
R1a, b
wR2c
Largest
difference in
peak and
hole (e Å-3)
3.373
2.981
3.673
100(2)
5711 (5254)
2.119
100(2)
8069 (7233)
0.0330 (0.0289)
0.0710 (0.0688)
R1 = ||Fo| - |Fc||/|Fo|.
Values in parentheses for reflections with I >
2(I).
a
b
c
wR2 = {[w(Fo2 - Fc2)2] / [w(Fo2)2]}½
C44H52N7O12Zn
Dy
9
10
C44H52N7O12Zn C44H52N7O12Zn
Er
Yb
Mr
Crystal
system
Space group
(no.)
1098.80
1103.56
1109.34
Monoclinic
Monoclinic
Monoclinic
P21/n (14)
P21/n (14)
P21/n (14)
a (Å)
13.547(5)
13.533(5)
13.542(5)
22.4764(12)
22.664(5)
12.051(5)
b (Å)
23.341(5)
23.340(5)
23.319(5)
12.8315(7)
12.828(5)
12.325(5)
c (Å)
14.882(5)
14.868(5)
14.857(5)
19.7813(10)
19.893(5)
17.328(5)

90.000(5)
90.000(5)
90.000(5)
90.00
90.000(5)
74.587(5)
β (°)
102.621(5)
102.600(5)
102.575(5)
90.00
90.000(5)
86.073(5)
Compound
Formula
8
Orthorhombic
Pca21 (29)
Orthorhombic
Pca21 (29)
Triclinic
P-1 (2)
γ (°)
90.000(5)
90.000(5)
90.000(5)
90.00
90.000(5)
83.022(5)
V (Å3)
4592(2)
4583(2)
4579(2)
5705.0(5)
5784(3)
2461.0(16)
Z
4
4
4
4
4
2
1.589
1.599
1.609
1.525
1.479
1.437
2.206
2.411
1.373
1.593
T (K)
Observed
reflections
100(2)
100(2)
100(2)
100(2)
8081 (7400)
8064 (7374)
Rint
0.0333
0.0399
-3
Dc (g cm )
MoKmm


2.623
100(2)
8003 (7326)
2.117
100(2)
8019 (7335)
9088 (8234)
8641 (6872)
0.0300
0.0711
0.0613
0.0559
595
740
749
589
1.001
Parameters
595
595
GOF
1.066
1.076
0.0280
(0.0251)
0.0618
(0.0601)
0.0293
(0.0262)
0.0650
(0.0634)
1.040
0.0309
(0.0277)
0.0675
(0.0658)
1.037
0.0370
(0.0319)
0.0723
(0.0693)
1.041
0.0467
(0.0409)
0.0965
(0.0914)
1.122 and 0.387
1.387 and 0.391
1.422 and 0.561
1.361 and 0.455
1.700 and 0.536
R1a, b
wR2c
Largest
difference in
peak and
hole (e Å-3)
R1 = ||Fo| - |Fc||/|Fo|.
Values in parentheses for reflections with I >
2(I).
a
b
c
wR2 = {[w(Fo2 - Fc2)2] / [w(Fo2)2]}½
0.0566 (0.0442)
0.0989 (0.0935)
1.238 and -0.451
Table S3.- Selected bond lengths and angles for complexes 1-13
Compound
1
Ln(1)-Zn(1)
1
3.4662(3) 3.4570(3)
3
4
5
6
3.637(1)
3.434(1) 3.4137(4) 3.4538(5)
Ln(1)-O(2A)
2.460(2)
2.479(2)
2.386(3)
2.369(2)
2.416(3) 2.660(3)
Ln(1)-O(5A)
2.329(2)
2.280(2)
2.298(2)
2.280(2)
2.250(3) 2.338(3)
2.240(2)
2.209(2)
2.189(2)
2.195(3) 2.371(2)
2.726(2)
2.721(3)
2.777(2)
2.562(3) 2.654(3)
2.307(2)
2.295(3)
2.268(2)
2.422(3)
Ln(1)-O(1B)nitrate
2.443(3)
2.423(2)
2.412(3 2.537(4)
Ln(1)-O(2B)nitrate
2.433(2)
2.408(2)
2.435(3) 2.554(3)
2.502(2)
2.435(3)
2.408(2)
2.439(3) 2.578(3)
2.447(3)
2.428(2)
2.449(3) 2.578(3)
Ln(1)-O(25A)
2.231(2)
Ln(1)-O(27A)
2.675(1)
Ln(1)-O(2)bridge
2.313(2)
Ln(1)-O(1C)nitrate
2.492(2)
Ln(1)-O(2C)nitrate
2.447(2)
2.483(2)
Ln(1)-O(1D)nitrate
2.471(2)
2.455(2)
2.577(3)
Ln(1)-O(2D)nitrate
2.494(2)
2.478(2)
2.559(1)
Zn(1)-N(12A)
2.180(2)
2.164(2)
2.256(3)
2.262(2)
Zn(1)-N(16A)
2.223(2)
2.240(2)
2.195(4)
2,194(3)
Zn(1)-N(20A)
2.226(2)
2.233(2)
2.256(3)
2.250(3)
Zn(1)-O(5A)
2.189(2)
2.172(2)
2.184(2)
2.177(2)
2.251(4) 2.216(4)
2.161(3) 2.117(2)
Zn(1)-O(25A)
2.071(2)
2.063(2)
2.097(2)
2.106(2)
2.045(3) 2.077(3)
Zn(1)-O(1)bridge
2.075(2)
2.057(1)
2.037(3)
2.041(2)
2.156(3)
2.170(4) 2.164(4)
2.182(4) 2.186(4)
2.219(3)
Zn(1)-O(1W)
Ln(1)-O(5A)-Zn(1)
100.16(6) 101.86(6) 100.00(9)
Ln(1)-O(25A)-Zn(1)
107.30(7) 106.87(7)
99.96(9)
105.7(1) 105.26(9)
103.0(1) 109.4(1)
109.1(1) 109.5(1)
O(5A)-Ln(1)-O(25A)
70.07(6)
69.90(6)
72.02(8)
72.51(8)
70.4(1) 65.87(8)
O(5A)-Ln(1)-O(2)bridge
78.43(6)
78.82(6)
80.88(6)
79.93(6)
78.88(9)
80.86(9)
79.80(8)
O(25A)-Ln(1)-O(2)bridge
81.60(8)
75.7(1)
78.9(1)
O(5A)-Zn(1)-O(25A)
75.83(6)
75.32(6)
76.48(9)
76.23(8)
75.0(1)
O(5A)-Zn(1)-O(1)bridge
93.36(6)
91.15(6)
90.35(9)
90.10(9)
87.3(1)
O(25A)-Zn(1)-O(1)bridge
93.85(6)
95.28(6)
95.76(9)
95.48(9)
90.6(1)
75.2(1)
O(5A)-Zn(1)-O(1W)
84.1(1)
O(25A)-Zn(1)-O(1W)
85.5(1)
8
9
7
10
11
12
13
3.4646(7) 3.4550(7) 3.4346(7) 3.4160(7) 3.4213(8) 3.529(1) 3.556(1)
Compound
Ln(1)-Zn(1)
Ln(1)-O(2A)
2.465(2)
2.453(2)
2.431(2)
2.416(2)
Ln(1)-O(5A)
2.289(2)
2.277(2)
2.259(2)
2.236(2)
Ln(1)-O(25A)
2.230(2)
2.222(2)
2.201(2)
2.181(2)
Ln(1)-O(27A)
2.606(2)
2.598(2)
2.599(2)
2.610(2)
Ln(1)-O(17D)bridge
2.345(2)
2.340(2)
2.311(2)
2.299(2)
Ln(1)-O(1B)nitrate
2.508(2)
2.482(2)
2.485(2)
2.378(2)
2.408(4) 2.530(4) 2.527(3)
2.254(4) 2.379(4) 2.397(2)
2.205(4) 2.318(3) 2.298(3)
2.854(4) 2.738(4) 2.686(2)
2.274(3) 2.412(4) 2.420(3)
2.456(4) 2.586(4) 2.589(4)
2.449(2)
2.443(2)
2.406(2)
2.475(2)
a
2.448(2)
2.438(2)
2.422(2)
2.389(2)
2.403(4) 2.549(4) 2.573(3)
2.382(4) 2.494(4) 2.499(4)
Ln(1)-O(2C)nitrateb
2.498(2)
2.495(2)
2.458(2)
2.443(2)
2.342(4) 2.473(4) 2.495(4)
Zn(1)-N(12A)
2.173(3)
2.175(2)
2.177(2)
2.179(3)
2.186(4) 2.196(4) 2.179(3)
Ln(1)-O(2B)nitrate
Ln(1)-O(1C)nitrate
2.200(5) 2.222(4) 2.226(4)
2.244(5) 2.276(4) 2.258(4)
Zn(1)-N16A)
2.222(3)
2.225(2)
2.224(2)
2.226(3)
Zn(1)-N(20A)
2.283(2)
2.284(2)
2.279(2)
2.275(2)
Zn(1)-O(5A)
2.186(2)
2.187(2)
2.179(2)
2.177(2)
Zn(1)-O(25A)
2.057(2)
2.055(2)
2.055(2)
2.056(2)
2.146(4) 2.183(4) 2.185(3)
2.115(4) 2.090(4) 2.073(2)
Zn(1)-O(16D)bridge
2.099(2)
2.099(2)
2.102(2)
2.102(2)
2.074(4) 2.061(4) 2.069(3)
Ln(1)-O(5A)-Zn(1)
101.43(8) 101.38(7) 101.40(7) 101.43(8)
Ln(1)-O(25A)-Zn(1)
107.76(9) 107.72(8) 107.59(8) 107.45(9)
102.1(2) 101.2(1) 101.7(1)
104.7(2) 106.3(2) 108.7(1)
O(5A)-Ln(1)-O(25A)
70.48(7)
70.69(6)
71.08(7)
71.51(7)
71.7(1)
O(5A)-Ln(1)-O(17D)bridge
77.76(7)
78.11(6)
78.46(7)
78.96(7)
78.9(1)
69.7(1) 67.99(9)
76.1(1) 77.12(9)
O(25A)-Ln(1)-O(17D)bridge
79.84(7)
80.05(6)
80.37(7)
80.63(7)
83.0(1)
78.6(1) 79.47(9)
O(5A)-Zn(1)-O(25A)
75.78(8)
75.64(7)
75.45(7)
75.09(8)
75.6(1)
77.8(1)
76.1(1)
O(5A)-Zn(1)-O(16D)bridge
91.04(7)
90.97(7)
90.83(7)
90.96(8)
91.8(1)
92.1(1)
90.4(1)
O(25A)-Zn(1)-O(16D)bridge
92.48(8)
92.40(7)
92.09(7)
92.01(8)
93.4(1)
93.8(1)
93.4(1)
a
11 y 12, O(16C) anthracene and O(1M )methanol
b
11 y 12, O(17C) anthracene O(1M )methanol
Continuous Shape Measures calculation for 2
MFF-9
HH-9
JTDIC-9
TCTPR-9
JTCTPR-9
CSAPR-9
JCSAPR-9
CCU-9
JCCU-9
JTC-9
HBPY-9
OPY-9
EP-9
13
12
11
10
9
8
7
6
5
4
3
2
1
Cs
C2v
C3v
D3h
D3h
C4v
C4v
C4v
C4v
C3v
D7h
C8v
D9h
Structure [ML9 ]
TCTPR-9
JTCTPR-9
JCCU-9
JTC-9
EC-078
2.799,
8.958,
4.168,
15.920,
Muffin
Hula-hoop
Tridiminished icosahedron J63
Spherical tricapped trigonal prism
Tricapped trigonal prism J51
Spherical capped square antiprism
Capped square antiprism J10
Spherical-relaxed capped cube
Capped cube J8
Johnson triangular cupola J3
Heptagonal bipyramid
Octagonal pyramid
Enneagon
MFF-9
HH-9
JTDIC-9
CSAPR-9
JCSAPR-9
CCU-9
HBPY-9
OPY-9
EP-9
,
2.274,
10.337,
11.809,
2.365,
14.999,
3.521,
23.362,
7.589,
36.124
Continuous Shape Measures calculation for 8
MFF-9
HH-9
JTDIC-9
TCTPR-9
13
12
11
10
Cs
C2v
C3v
D3h
Muffin
Hula-hoop
Tridiminished icosahedron J63
Spherical tricapped trigonal prism
JTCTPR-9
CSAPR-9
JCSAPR-9
CCU-9
JCCU-9
JTC-9
HBPY-9
OPY-9
EP-9
9
8
7
6
5
4
3
2
1
D3h
C4v
C4v
C4v
C4v
C3v
D7h
C8v
D9h
Structure [ML9 ]
TCTPR-9
JTCTPR-9
JCCU-9
JTC-9
mp-1133
,
2.761,
4.689,
9.510,
15.240,
Tricapped trigonal prism J51
Spherical capped square antiprism
Capped square antiprism J10
Spherical-relaxed capped cube
Capped cube J8
Johnson triangular cupola J3
Heptagonal bipyramid
Octagonal pyramid
Enneagon
MFF-9
CSAPR-9
HBPY-9
1.668,
2.000,
16.549,
HH-9
JCSAPR-9
OPY-9
9.091,
2.947,
22.853,
JTDIC-9
CCU-9
EP-9
11.107,
8.196,
35.937
Continuous Shape Measures calculation for 3
MFF-9
HH-9
JTDIC-9
TCTPR-9
JTCTPR-9
CSAPR-9
JCSAPR-9
CCU-9
JCCU-9
JTC-9
HBPY-9
OPY-9
EP-9
13
12
11
10
9
8
7
6
5
4
3
2
1
Cs
C2v
C3v
D3h
D3h
C4v
C4v
C4v
C4v
C3v
D7h
C8v
D9h
Structure [ML9 ]
TCTPR-9
JTCTPR-9
JCCU-9
JTC-9
EC-277
,
2.664,
3.667,
8.316,
15.663,
Muffin
Hula-hoop
Tridiminished icosahedron J63
Spherical tricapped trigonal prism
Tricapped trigonal prism J51
Spherical capped square antiprism
Capped square antiprism J10
Spherical-relaxed capped cube
Capped cube J8
Johnson triangular cupola J3
Heptagonal bipyramid
Octagonal pyramid
Enneagon
MFF-9
CSAPR-9
HBPY-9
2.342,
2.413,
15.296,
HH-9
JCSAPR-9
OPY-9
8.670,
3.606,
23.442,
JTDIC-9
CCU-9
EP-9
11.539,
7.053,
35.508
Continuous Shape Measures calculation for 5
MFF-9
HH-9
JTDIC-9
TCTPR-9
JTCTPR-9
CSAPR-9
JCSAPR-9
CCU-9
JCCU-9
JTC-9
HBPY-9
OPY-9
EP-9
13
12
11
10
9
8
7
6
5
4
3
2
1
Cs
C2v
C3v
D3h
D3h
C4v
C4v
C4v
C4v
C3v
D7h
C8v
D9h
Muffin
Hula-hoop
Tridiminished icosahedron J63
Spherical tricapped trigonal prism
Tricapped trigonal prism J51
Spherical capped square antiprism
Capped square antiprism J10
Spherical-relaxed capped cube
Capped cube J8
Johnson triangular cupola J3
Heptagonal bipyramid
Octagonal pyramid
Enneagon
Structure [ML9 ]
TCTPR-9
JTCTPR-9
JCCU-9
JTC-9
EC-287
,
2.368,
4.456,
9.260,
14.957,
MFF-9
CSAPR-9
HBPY-9
1.607,
1.531,
17.497,
HH-9
JCSAPR-9
OPY-9
11.146,
2.568,
22.261,
JTDIC-9
CCU-9
EP-9
10.742,
7.839,
37.099
Figure S1.- Temperature dependence of in-phase ’M (left) and out-of-phase ”M (right)
components of the ac susceptibility for complex 8 measured under zero applied dc field.
Figure S2.- Variable-temperature frequency dependence of the χM" signal for 5 in a
1000 Oe dc field. Solid lines represent the best fit to the Debye model (left top).
Arrhenius plots for 5 (left down) and for 3 (right, down).
Figure S3.- Variable-temperature frequency dependence of the χM" signal for 2 (left top)
and 8 (right top) in a 1000 Oe dc field. Solid lines represent the best fit to the Debye
model. Arrhenius plots for 2 (left down) and for 8 (right down).
Figure S4.- Cole-cole plots for 3 (left top), 5(left down), 2 (right top) and 8 (right down)
Figure S5.- Reflectance spectrum of the ligand.
Figure S6.- NIR sensitized emission spectra of complex 4.