Michaele Hardie’s Research Group
School of Chemistry, University of Leeds
Postgraduate and Postdoctoral group members past and present:
PhD Students
Postdoctoral Researchers
James Henkelis
Dr Tia Jacobs
Marc Little
Dr Tanya Ronson
Dr Aleema Westcott
Dr Christopher Sumby
Dr Christopher Carruthers
Dr Luis Cunha-Silva
Dr Maria Stephenson
Dr Ruksanna Ahmad
Dr Scott Dalgarno (co-supervised with Prof CL Raston)
Tanya, Michaele, Chris C and Marc after group lunch at No. 3 York Place, Leeds 2009
Keywords
Metallo-supramolecular
chemistry
Crystal Engineering
Host molecules
X-ray crystallography
Overview of Research Interests:
We are a metallo-supramolecular chemistry group with a particular interest in using (a) host receptor
molecules or (b) simple coordination compounds, as components of much more complicated
supramolecular assemblies. We have additional expertise in single crystal X-ray crystallography.
All researchers in the group are involved in organic and coordination synthetic chemistry, use standard
spectroscopic characterisation and learn/use single crystal X-ray crystallography. Some projects also
involve SEM and DSC studies. We collaborate locally with Dr Julie Fisher for advanced NMR studies,
Dr Sarah Harris (Physics) for molecular dynamics simulations and with Prof Malcolm Halcrow for some
coordination chemistry studies.
Our research is currently supported by the EPSRC and the Leverhulme Trust.
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Further details are given below for the following research areas:
(i) Synthesis of new host-type ligands
(ii) “Star-burst” metallo-supramolecular assemblies and topologically complicated assemblies
(iii) Crystal engineering with host molecules
(iv) Organisation of metallo(supramolecular) complexes
(i) Synthesis of new host-type ligands
We have recently developed a series of new molecular hosts based on cyclotriveratrylene (=CTV)
which is a macrocyclic trimer of veratrole (1,2-dimethoxybenzene) with a rigid bowl-shape. CTV has a
molecular cavity capable of binding guest molecules including small organics and fullerene C 60. We
have largely focussed on appending N-donor ligand groups to the CTV framework some of which are
shown below.[1]
OR
RO
RO
OR
RO
O
OR
O
R=
N
1
R = CH3, CTV
OMe
MeO
RO
OR
MeO
N
N
N
2
N
3
N
R=
OR
5
N
O
N
N
O
N
N
6
4
7
N
8
9
O
Me
O
R = H, CTG
R = CH2CHCH2 trisallylCTG
N
N
N 11
10
R R
O HN
NH O
N
N
R
N
13
12
N
HO 2C
R=
O HN
CO 2H CO 2H
N
14
17
16
15
O
N
N
N
19
18
O
O
O
O O
22
N
20
21
Selection of new CTV-type ligands
HO
OMe
OH
OMe
Br MeO
O
OH
Cl
N
N
N
N
N
K2 CO 3
NaH, DMF
MeO
OMe
O
O
acetone
N
N
O
N
[18]crown-6
N
N
NEt3 , THF
0C, rT N
CTG
OMe
N
O
O
HCl. Cl
OMe
N
N
O
O
MeO
O
OMe
O
O
OMe
N
N
O
MeO
OMe
O
Typical synthetic routes to ligands
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These ligands can form clathrate inclusion complexes with organic solvents (Fig 1a); discrete
transition metal complexes (Fig 1b);[2] metallo- or organo-gels (Fig 1c);[3] and are also utilised in
sections (ii) and (iii) below.
(a)
(b)
(c)
Fig. 1 (a) X-ray structure of ligand 14; (b) [Pd3Cl6(1)] acting as a host for DMF; (c) SEM of
metallo-gel formed from ligand 12, CuBr2 and DMF
(ii) “Star-burst” discrete metallo-supramolecular assemblies and topologically complicated
assemblies
Discrete metallo-supramolecular complexes with polyhedral or prismatic shapes, and hence significant
internal space, have been known for a number of years and are being developed as nano-scale
reaction vessels (see work of Makoto Fujita in particular). Using our CTV-based ligands for such selfassembled systems gives complexes with much larger internal space and inherent molecular
recognition sites. It also gives the assemblies and unusual “star-burst” or stellated aspect to their
structures. We recently reported crystal structures of [Ag2(15)2]2+ dimeric capsules (Fig. 2a),
[Ag4(16)4]4+ tetrahedra (Fig. 2b),[4] and the giant [Pd6(9)8]12+ stella octangula (Fig. 2c)
[5]
with the latter
two species also present in solution.
(a)
(c)
(b)
Fig 2 X-ray structures (a) Capsule assembly of [Ag2(CH3CN)2(14)2]2+ (b) a [Ag4(CH3CN)7(15)4]4+ “starburst” tetrahedron. (c) the stella octangula structure of [Pd6(5)8]12+ which is > 3nm in diameter
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We can synthesise a family of [Pd6L8]12+ stella octangulas through variations on the ligand, for instance
the larger ligand 10.[6] In collaboration with Julie Fisher and Sarah Harris we are investigating the
stella octangula as a nano-sized host molecules, with a view to their development as nano-reaction
vessels.
Some discrete metallo-supramolecular assemblies involving these ligands have highly unusual
structures which are topologically complicated – for instance, they form chain-like catenane structures
or are self-threading. For example, [Zn3(12)3(NO3)3]3+ has a capsule-like structure where two
independent capsules inter-lock to form a rare triply interlocked [2]catenane, Fig 3a. [7] The complex
[Pd4(11)4(NO3)4]4+ is shown in Fig. 3b and has a unique chemical topology that can be described as an
interwoven cube, or “Solomon’s cube”, so-called due to analogies with a Solomon’s link.[8]
(b)
(a)
Fig 3 X-ray structures (a) {[Zn3(12)3(NO3)3]}26+ [2]catenane and cartoon showing interlocked motif; (b)
[Pd4(11)4(NO3)4]4+ Solomon’s cube
(iii) Crystal engineering with host molecules
Crystal engineering involves the manipulation of the way that molecules are arranged in a crystal
lattice by utilising supramolecular interactions. We are particularly interested in coordination polymers
which are metal-ligand systems with ordered 1D, 2D or 3D network structures. Using host molecules
as ligands for coordination polymers means that materials that show multiple inclusion modes can be
generated, and simple host-guest interactions can have a large effect on the overall assembly. CTV
itself forms coordination polymers with Group 1 metal cations, for example in complex
[Na(CTV)(H2O)(CB11H6Cl6)] where the carbaborane anion is also a molecular guest (Fig 3a).[9] CTVtype ligands form 1D, 2D or 3D coordination polymers with various transition metals. For example,
[Ag3(CH3CN)3(8)2Cl]+ where capsule-like assemblies are linked through bridging 3-Cl- ligands into a
2D network (Fig. 3b).[10] Interestingly we are seeing examples of “host-guest” control of the overall selfassembly processes. For example, ligand 14 and Ag(I) assemble into the star-burst tetrahedron
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shown in Fig. 3b with CH3CN guest molecules, but assemble into a 2D coordination polymer (Fig 3c)
in the presence of the bulkier guest glutaronitrile.[4b] The complex [Ag2(tris-allylCTG)2]2+ is an
organometallic coordination polymer with a 3D framework structure featuring large unidirectional
channels, Fig. 3d.[11]
(a)
(b)
(c)
(d)
Fig 4 X-ray structures of coordination polymers (a) ID coordinaton polymer
[Na(CTV)(H2O)(CB11H6Cl6)] (b) 2D network of linked capsules of [Ag3(CH3CN)3(8)2Cl]+; (c) 2D
coordination polymer [Ag(14)(NC(CH2)3CN)]+ with NC(CH2)3CN guests in green; (d) 3D
organometallic polymer of [Ag2(tris-allylCTG)2]2+.
(iv) Organisation of metallo(supramolecular) complexes
A developing area for us is organising discrete coordination complexes, or metallo-supramolecular
complexes, in the solid state by imparting them with functionality such as hydrogen-bond donor or acceptor
functionality or additional ligation sites. Initial studies have investigated simple aquo lanthanide metal
complexes with bipyridine hydrogen-bond acceptors,[12] and complexes of phenanthroline-type and 2,2’bipyridine-type ligands. We have recently characterised hydrogen-bonded assemblies which, very unusually,
have layers of hydrogen-bonded networks of organic fragments and coordination complexes with identical
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network topology (Fig. 5a).[13] A new complex [Co(2,2-bipyridine-3,3-diol-H)3] has a simple tris chelate
octahedral structure and the extended structure has significant tube-shaped channels (Fig 5b).[14] This
material is held together by weak C-H…O hydrogen bonding. Very unusually for a molecular complex, it is
perfectly stable when the disordered contents of the channels are evacuated under vacuum or exchanged
for another guest solvent. A trigonal bipyramidal [Pd3L2(OAc)6] metallo-supramolecular assembly shows
similar crystal packing (Fig. 5c) and is also a material that is truly porous, being robust to evacuation of
solvent under vacuum at high temperature.[15]
(c)
(b)
(a)
Fig 5 (a) Layered hydrogen bonded structure of [Cu(1,10-phenanthroline-5,6dione)2(H2tma)2].2(H3tma) (H3tma = trimesic acid); (b) + (c) Porous molecular structures of (a)
[Co(2,2’-bipyridine-3,3’-diol-H)3] and (c) [Pd3L2(OAc)6] where L = tris(6-methyl-2pyridyl)benzene-1,3,5-tricarboxamide
Selected References:
[1] M. J. Hardie, R. M. Mills, C. J. Sumby, Org. Biomol. Chem, 2004, 2, 2958-2964.
[2] C. J. Sumby, K. C. Gordon, T. J. Walsh, M. J. Hardie, Chem. Eur. J., 2008, 14, 4415 - 4425.
[3] A. Westcott, C. J. Sumby, R. D. Walshaw, M. J. Hardie, New J. Chem., 2009, 33, 902.
[4] (a) C. J. Sumby and M. J. Hardie, Angew. Chem. Int. Ed., 2005, 44, 6395 – 6399; (b) C. J. Sumby, J.
Fisher, T. J. Prior and M. J. Hardie, Chem. Eur. J., 2006, 12, 2945-2959
[5] T.K. Ronson, J. Fisher, L. P. Harding and M. J. Hardie, Angew. Chem. Int. Ed. 2007, 46, 9086-9088.
[6] T. K. Ronson, C. Carruthers, J. Fisher, T. Brotin, L. P. Harding, P. J. Rizkallah, M. J. Hardie, Inorg.
Chem., 2010, 49, 675-685
[7] A. Westcott, J. Fisher, L. P. Harding, P. Rizkallah, M. J. Hardie, J. Am. Chem. Soc., 2008, 130, 29502951.
[8] T. K. Ronson, J. Fisher, L.P. Harding, P. J. Rizkallah, J. E. Warren, . M. J. Hardie, Nature Chemistry, 2009,
1, 212-216.
[9] R. Ahmad, A. Franken, J. D. Kennedy, M. J. Hardie, Chem. Eur. J., 2004, 10, 2190-2198.
[10] T. K. Ronson, M. J. Hardie, CrystEngComm, 2008, 10, 1731-1734.
[11] M. A. Little, M. A. Halcrow, L. P. Harding, M. J. Hardie, Inorg. Chem., 2010, 49, 9486-9496
[12] L. Cunha-Silva, A. Westcott, N. Whitford and M. J. Hardie, Cryst. Growth & Des., 2006, 6, 726-735.
[13] M. D. Stephenson and M. J. Hardie, Dalton Trans., 2006, 3407 - 3417
[14] M. D. Stephenson and M. J. Hardie, CrystEngComm, 2007, 496-502
[15] A. Westcott, J. Fisher, L. P. Harding and M. J. Hardie, CrystEngComm, 2008, 276 – 278.
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