List of Abbreviations
bpy
dppz
phen-allox
phen-dap
phen-dione
phen-dma
phen-pterin
L
2,2’-bipyridine
dipyrido[3,2-a:2’,3’-c]phenazine
phenanthroline-alloxazine
phenanthroline-diaminopyrimidine
1,10-phenanthroline-5,6-dione
phenanthroline-dimethylalloxazine
phenanthroline-pterin
phen-allox, phen-dap, phen-dma, and/or phenpterin
1
Abstract: A selection of [(bpy)2RuII(L)](PF6)2, [MII(L)3]Cl2 (M =
RuII or FeII), and [CuII(L)2](NO3)2 compounds were synthesized.
Their characterizations by 1H NMR, infrared, UV/vis, and
electrochemical spectroscopy are reported. Extinction coefficients
were estimated from UV/vis data, and E and E1/2 values were
calculated for electrochemical data. For the purpose of determining
the role of hydrogen bonding in [MII(L)3] and [CuII(L)2] crystals
crystallization is desired. Methods are discussed and results seem
promising, but x-ray diffraction studies have yet to be completed.
The [(bpy)2RuII(L)] complexes are being investigated as possible
DNA intercalators. Additionally, charge transfer reactivity between
RuII and ligands and other redox activity of ligands suggest that the
complexes synthesized here in could participate in electron
transportation reactions.
2
Introduction
Molecules capable of intercalating DNA are greatly sought after for
numerous biomedical and biochemical applications. Duanomycin and
Adriamycin are two drugs currently on the market that utilize DNA intercalation
for the treatment of cancers. Extended planar aromatic ring structures are able
to intercalate DNA by inserting themselves between base pairs.
[(bpy)2RuII(dppz)] has been extensively studied for its intercalation capability.
To investigate the effect that substitution of dppz has on intercalation four
[(bpy)2RuII(L)] compounds whose ligand structures are a composite of dppz and
various pyrimidines were designed and synthesized. The general structure of
[(bpy)2RuII(L)], dppz, and the ligand structures are shown in Figure 1. It is yet
uncertain as to which, if any, of the new [(bpy)2RuII(L)]
N
N
N
N
Ru
+2
N
N
N'
General ligand L.
N
[RuII(bpy)2(L)]
O
N
N
N
O
N
N
N
N
N
N
N
N
Dppz
N
NH
O
N
NH2
N
N
N
NH
N
N
N
H
Phen-allox
Phen-dma
O
N
N
N
N
NH2
N
Phen-pterin
N
N
NH2
Phen-dap
FIGURE 1. A general representation of the ligands inv0lved in
syntheses to be discussed is given along with the actual
structures of the ligands. Dppz is shown to illustrate the
inspiration for the ligands’ design and the [(bpy)2RuII(L)]
drawing demonstrates the form of these possible intercalators.
3
O
complexes can intercalate DNA. The substitutions made to dppz to give the new
ligands may prevent intercalation by creating too much steric bulk to slide
between base pairs. Other possible interactions between the [(bpy)2RuII(L)]
complexes and a DNA double helix, including hydrogen bonding with a base,
groove binding, and electrostatic surface binding with the anionic phosphate
backbone of DNA, Figure 2, may be preferred. Intercalation of a DNA strand
QuickTi me™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
FIGURE 2. From left to right: an image of a ligand chelated to a metal, M, and
intercalating DNA, an example of a molecule groove binding with DNA, and a
suggestion of how [(bpy)2RuII(phen-allox)] could hydrogen bong to guanine in
DNA (only a small portion of a DNA strand is shown to clearly demonstrate
hydrogen bonds).
causes the double helix to lengthen, unwind, and stiffen. There are a number of
experimental methods for detecting whether these changes in DNA occur upon
[(bpy)2RuII(L)] addition. Fluorescence titrations, melting temperature curves, gel
electrophoresis, and viscocity titrations are being carried out to examine the
interactions between [(bpy)2RuII(L)] and DNA. Justification of the synthetic
pathways for the [(bpy)2RuII(L)] complexes and their characterization data are
included in the Results and Discussion section.
Like their model [(bpy)2RuII(dppz)], [(bpy)2RuII(L)] undergo metal-toligand charge transfer (MLCT) upon photo excitation. The MLCT of
[(bpy)2RuII(dppz)] is believed to involve the excitation of a 4d electron on RuII to
a low lying * molecular orbital localized on the bpy-like portion of dppz1.
Furthermore, pteridines like those incorporated into the ligands (especially phenpterin) are known to undergo proton transfer/reduction reactions greatly
localized on the pyrazine ring2. It is of interest as to whether the MLCT reactions
4
of [(bpy)2RuII(L)] complexes can correspond with coupled proton/electron
transfer reactions of ligands to create electron transfer pathways. Absorption
bands in UV/vis measurements may be assigned to MLCT excitations for a
complex by comparison with [RuII(bpy)3] data and trends for excitation
wavelengths. Trends in E1/2 values for RuIIRuIII oxidation suggest relative
stabilizing effects of the various substituents on ligands. Describing light
absorbance and redox mechanisms for the ligands requires a much more involved
study of the complexes, including molecular orbital modeling and determination
of relative energies of available spin states. Thus, the entire set of UV/vis and
electrochemical data will not be resolved in this paper.
The synthesis and characterization studies of [(bpy)2RuII(L)] complexes
branched into a separate synthetic study where the ligands are chelated with RuII,
FeII, and CuII to make [MII(L)3] (MII= RuII or FeII) and [CuII(L)2] complexes.
MLCT peak assignments in UV/vis spectra and MIII/MII E1/2 values for
electrochemical spectra were made by comparison with [RuII(bpy)3] and
[FeII(bpy)3] spectra. There is the possibility that replacing bpy ligands with larger
planar ring structures could negatively effect the molecules’ potential electron
transfer activity. However, these [MII(L)3] and [MII(L)2] complexes are of interest
for another reason. Through x-ray diffraction analysis of the crystalline
complexes it can be determined whether they are polymeric crystals held together
by hydrogen bonds between ligands. Shown in Figure 3 are several ways in which
these ligands can hydrogen bond to each other and a computer simulation of a
possible extended hydrogen-bonded array of molecules.
5
(a)
i.
ii.
H
H
O
N
N
N
N
O
N
N
N
H
H
O
N
N
O
N
N
N
N
N
N
N
N
N
N
N
N
N
N
O
H
N
H
N
N
N
N
N
N
H
N
H
N
N
N
O
H
H
iii.
N
N
N
N
H
iv.
H
N
H
N
H
N
N
O
N
H
N
H
N
N
N
H
H
N
N
N
N
N
O
N
H
N
N
H
N
H
N
H
N
N
N
H
v.
H
H
N
N
O
N
N
N
vi.
O
N
H
N
N
H
O
H
N
N
N
N
N
N
N
O
N
H
N
H
N
H
N
H
N
H
N
N
N
N
H
(b)
FIGURE 3. (a) Hydrogen bonding interactions between various ligands: i) phen-pterin
bonding to phen-pterin; ii) phen-allox bonding to phen-allox; iii) phen-dap bonding to phen-dap;
iv) phen-dap bonding to phen-allox; v) phen-pterin bonding to phen-dap; vi) phen-pterin
bonding to phen- allox. (b) A simulated extended structure of hydrogen-bound [RuII(phenpterin)3] molecules.
6
An actual crystal structure for a [MII(L)3] or [MII(L)2] compound, or a mixture of
the compounds has not yet been obtained though crystal growing methods have
been explored and are reported. The crystal design proposed in Figure 3 may not
be reasonable to expect because it is built with an enantiomerically pure set of
molecules and the large gaps that would result in the structure are unlikely to
exist without a sizable support to fill them, so the molecules may resort to pistacking interactions for crystallization. If the complexes do form hydrogen
bound crystal lattices, they may have zeolite-like material sciences applications.
Experimental Section
Materials. Cis-dichloro-bis(bpy)ruthenium (II)  2 H2O was obtained from
Alfa Aesar. All other reagents were purchased from Aldrich. Ultra high purity
acetonitrile/dimethylformamide was purchased from Burdick & Jackson for use
in electrochemical measurements. Synthesis of phen-dione followed the
procedure according to Yamada et al.3 and synthesis of phen-dma and
[(bpy)2RuII(phen-dma)] followed procedures 0f Black et al.4
Methods. 1H NMR spectra were run on a Bruker 300 MHz Fourier
Transform NMR in d6-DMSO (Aldrich). KBr (Aldrich) pellets were made for IR
spectra run on a Perkin-Elmer Infrared Spectrophotometer 283. All UV/Vis
absorption spectra were taken in a quartz crystal cuvett with a Aligent
Technologies UV/Vis Diode Array Spectrophotometer. ESI-MS analyses were
done at the university of Arizona. A Bioanalytical Systems, Inc. CV-50W
Voltammetric Analyzer was used to make electrochemical measurements.
Measurements were taken in a single compartment (5-10 mL samples) cell with a
platinum working electrode, a platinum auxiliary electrode, and a silver chloride
saturated silver reference electrode. Due to solubility difficulties, a complete set
of data for could not be collected for [RuII(phen-pterin)3] and [RuII(phen-dap)3].
Phen-dione. IR (KBr): vC=O 1718, 1687 cm 1 . 1H-NMR (DMSO), ppm (TMS):
7.67 (m, 2H), 8.39 (d, 2H), 8.99 (d, 2H).
7
Phen-allox. 1,10-phenanthroline-5,6-dione (0.8330 g, 4.001 mmol) was added
to 5,6-diamino-2,4-dihydroxypyrimidine sulfate (0.6544 g, 4.605 mmol) in 95
mL methanol and heated under reflux for 2 h. The reaction solution was cooled
then vacuum filtered using a Buchner funnel. The crude product was
recrystallized from 0.5 M HCl (75 mL). Yield 0.8402 g light yellow powder
(66.40%). IR (KBr): vC=O 1718, 1703 cm-1. 1H-NMR (DMSO), ppm (TMS): 8.15
(m, 2H), 9.3 (d, 2H), 9.46 (d, 2H), 11.96 (s, 1H), 12.42 (s, 1H).
Phen-dma. 1H-NMR (DMSO), ppm (TMS): 3.68 (s, 3H), 3.91 (s, 3H), 7.85 (m,
2H), 9.34 (d, 2H), 9.3 (d, 2H).
Phen-pterin. This ligand was prepared by dissolving 1,10-phenanthroline-5,6dione (0.831 g, 3.9901 mmol) and 6-hydroxy-2,4,5-triaminopyrimidine sulfate
(0.823 g, 3.440 mmol) in ethanol (25 mL), adding sodium acetate (1.502 g) in
water (50 mL) and refluxed for 2 h. The reaction solution was cooled then
vacuum filtered. The crude product was recrystallized from 2 M HCl (100 mL).
Yield 0.7599 g yellow-orange sliver crystals (70.08%). IR (KBr): vC=O 1596 cm-1.
1H-NMR
(DMSO), ppm (TMS): 8.12 (m, 2H), 9.02 (d, 2H), 9.11 (d, 2H), 10.47 (s,
1H).
Phen-dap. This ligand was prepared similarly to phen-pterin. The crude
product was purified by suspension in hot water with addition of NaOH drop
wise to promote dissolution. Slow cooling produced a marigold colored product.
Yield 0.7826 g marigold colored powder (59.18%). 1H-NMR (DMSO), ppm
(TMS): 7.03 (s, 2H), 7.89 (m, 2H), 8.07 (s, 1H), 8.54 (s, 1H), 9.15 (d, 2H), 9.55 (d,
2H).
[(bpy)2RuII(phen-dma)](PF6)2.
1H-NMR
(DMSO), ppm (TMS): 3.48 (s,
3H), 4.05 (s, 3H), 7.37 (m, 2H), 7.60 (t, 2H), 7.72 (d, 2H), 7.83 (d, 2H), 8.03 (m,
2H), 8.13 (t, 2H), 8.26 (d, 2H), 8.87 (t, 4H), 9.44 (d, 1H), 9.60 (d, 1H).
8
[(bpy)2RuII(phen-allox)](PF6)2. Ru(bpy)2Cl2 (0.0998 g , 0.1921 mmol) and
phenanthroline-alloxazine (0.0429 g, 0.1356 mmol) were combined in ethylene
glycol (60 mL) and refluxed for 2 h. The solution was cooled and 60 ml water
were added then filtered to remove insoluble impurities. To the orange filtrate
was added NH4PF6 until precipitation was complete. Filtration produced a bright
orange-red solid. Yield 0.0841 g red-orange powder (70.89%). 1H-NMR (DMSO),
ppm (TMS): 7.37 (m, 2H), 7.59 (t, 2H), 7.71 (d, 2H), 7.82 (d, 2H), 8.01 (m, 2H),
8.13 (t, 2H), 8.25 (d, 2H), 8.86 (t, 4H), 9.31 (d, 1H), 9.41 (d, 1H), 12.06 (s, 1H),
12.55 (s, 1H).
[(bpy)2RuII(phen-dap)](PF6)2. Prepared similarly to Ru(bpy) 2(phen-allox).
0.1002 g (0.1929 mmol) Ru(bpy)2Cl2 and 0.049 g (0.1428 mmol) phen-diamino.
Yield 0.0631 g brown powder (50.61%). 1H-NMR (DMSO), ppm (TMS): 7.42 (t,
2H), 7.65 (t, 2H), 8.00 (t, 2H), 8.18 (d, 2H), 8.27 (m, 2H), 8.34 (t, 2H), 8.51 (m,
3H), 8.85 (t, 4H), 9.39 (d, 1H), 9.81 (d, 1H).
[(bpy)2RuII(phen-pterin)](PF6)2. Prepared according to above preparation
for Ru(bpy) 2(phen-allox) with 0.110 g (0.2118 mmol) Ru(bpy)2Cl2 and 0.0448 g
(0.1428 mmol) phen-pterin. Yield 0.0092 g olive-brown powder (7.41%). 1HNMR (DMSO), ppm (TMS): 7.58 (t, 4H), 7.73 (m, 6H), 7.95 (d, 2H), 8.20 (t, 4H),
8.54 (d, 2H), 8.85 (d, 4H), 10.32 (s, 2H).
[RuII(phen-allox)3]Cl2. Phen-allox (0.3560 g, 1.125 mmol) and RuIIICl3
(0.0620 g, 0.2989 mmol) were added to ethylene glycol (20 mL), refluxed at
215C for 2 h., and cooled to room temperature. Precipitate was filtered and
discarded. Acetone (150 mL) was added drop wise to the filtrate. Precipitate was
filtered and washed with 10 mL cold water, 10 mL cold ethanol, 30 mL
chloroform, and excess diethyl ether. Yield 0.2461 g orange-red powder (73.45%).
1H-NMR
(DMSO), ppm (TMS): 7.93 (m, 2H), 8.31 (d, 2H), 9.33 (d, 2H), 12.02 (s,
1H), 12.55 (broad s, 1H).
9
[RuII(phen-dap)3]Cl2. Prepared similarly to [Ru(phen-allox)3]Cl2 with phendiamino (0.3610 g, 1.148 mmol) and Ru IIICl2 (0.0633 g, 0.3052 mmol). Yield
0.2780 g orange-brown powder (81.70%).
[RuII(phen-pterin)3]Cl2. Phen-pterin (0.3564 g, 1.130 mmol) and RuIIICl2
(0.0608 g, 0.2931 mmol) were added to ethylene glycol (20 mL), refluxed at
215C for 2 hr., and cooled to room temperature. Solution was reheated in a r.b.
flask for several hours at 220C and then cooled to room temperature. Precipitate
was filtered and washed with 10 mL cold water, 10 mL cold ethanol, 30 mL
chloroform, and excess diethyl ether. Yield small amount of dark brown powder.
1H-NMR
(DMSO), ppm (TMS): 8.14 (dd, 6H), 9.12 (d, 6H), 9.19 (d, 6H).
[FeII(phen-allox)3]Cl2. Phen-allox (0.1530 g, 0.4837 mmol) was dissolved in
DMF (50 mL) with sonication. FeIICl2 (0.0326 g, 0.1640 mmol) was added to the
solution with stirring and the color changed from orange to red to deep purple.
The solution was filtered and the drop wise addition of ether to the filtrate
precipitated purple solid. Yield 0.1213 g dark purple powder (67.78%). 1H-NMR
(DMSO), ppm (TMS): 7.95 (m), 9.30 (m, 6H), 9.43 (m, 6H).
[FeII(phen-pterin)3]Cl2. Prepared by the above method for Fe(phen-allox)3
with phen-pterin (0.1763 g, 0.5591 mmol) and FeIICl2 (0.0420 g, 0.2112 mmol).
Yield 0.1588 g rosy red powder (80.47%). 1H-NMR (DMSO), ppm (TMS): 7.47 (d,
6H), 7.63 (m, 6H), 8.73 (d, 6H), 10.45 (s, 3H).
[FeII(phen-dap)3]Cl2. Prepared by the above method for Fe(phen-allox)3 with
phen-diamino (0.1563 g, 0.4972 mmol) and FeIICl2 (0.0331 g, 0.1665 mmol).
Yield 0.1185 g cherry red powder (66.83%).
[CuII(phen-pterin)2](NO3)2. Prepared by the above method for Fe(phenallox)3 with phen-pterin (0.1513 g, 0.4798 mmol) and CuII(NO3)22H2O (0.0777 g,
0.3475 mmol). Yield: 0.0651 g bright green powder (33.16%).
10
Results and Discussion
Syntheses. Phen-dione was synthesized for the purpose of making the ligands.
Previous synthetic pathways for phen-dione included a several step catalysis
reaction of 1,10-phenanthroline with Pd. A much shorter synthesis was
eventually adopted where in concentrated acid is added to 1,10-phenathroline
and NaBr. Further improvements were made to this reaction by Yamada et al.
that simplified the process of extracting product such that yield was increased
from 60% to 90% and the purity was enhanced, Scheme 1. Best results were
N
1) con. H 2SO4, con. HNO 3,
NaBr; 90 C for 2 h
N
O
N
O
2) neutralize w/H 2O, NaHCO3
N
SCHEME 1. Synthesis of phen-dione from 1,10-phenanthroline.
obtained the reaction was performed over a single day. The ligands were
synthesized by a condensation reaction of the phen-dione and a 5,6diaminopyridine, Scheme 2.
11
O
O
H2 N
N
NH
O
H2N
N
N
NH2
, NaCOOCH3
N
NH
H2O/EthOH (2:1) solvent,
reflux 2 hr
O
N
N
N
N
NH2
NH2
H2 N
H 2N
NH2
N
N
NH2
, NaCOOCH3
N
N
N
H2O/EthOH (2:1) solvent,
reflux 2 hr
N
N
N
N
N
NH2
O
H2N
H2N
N
N
O
O
N
MeOH solvent,
reflux 2 hr
N
N
N
O
O
H2 N
O
NH
O
N
MeOH solvent,
reflux 2 hr
N
H2N
N
H
N
NH
N
N
H
O
SCHEME 2. Ligand syntheses from the top down: phen-pterin,
phen-dap, phen-dma, and phen-allox.
The [(bpy)2RuII(L)] complexes needed to be synthesized in high purity for
the low concentration DNA intercalation studies. The previous method of
synthesis produced compounds that were pure by standards of an old
fluorescence spectrometer that has been replaced since the last student worked
on this project in 1995. The similar solubilities of each ligand and its
[(bpy)2RuII(L)] complex made purification of the product unachievable by most
methods other an inefficient crystallization. Rather, the approach was to
synthesize [(bpy)2RuII(L)] with an excess of Ru(bpy)2Cl2, Scheme 3. Hence, cost
efficiency
12
N
N
+
1.4 eqiv RuII(bpy)2Cl2
N'
1) ethylene glycol, solvent
220 C, 2 h
N
2) H2O, excess NH4PF6
N
N
Ru
+2
N
N
SCHEME 3. Synthesis of [(bpy)2RuII(L)](PF6)2.
was sacrificed for the sake of time because only a small amount of product
needed to be synthesized for the DNA intercalation studies. The use of a
stoichiometric excess worked to minimize the amount of unreacted ligand to
undetectable by the standards of the fluorimeter. The difficulty in chelating the
ligands to RuII may be due to the strength of the Ru-Cl bonds that must be broken
in Ru(bpy)2Cl2 before ligand chelation can occur. This reaction takes place in a
viscous solvent capable of refluxing at about 214C, providing enough heat to
break the Ru-Cl bonds. The resulting [(bpy)2RuII(L)] products appear to be
stable at these temperatures for the two hours. The driving force of the reaction
that partly explains such stability is illustrated in Figure 4 with ligand field theory.
Ru II
[(bpy) 2Ru IIL]
[Ru IIL3]
eg
eg
delta o'
delta o
4d6
t2g
t2g
FIGURE 4. Ligand field theory description of how chelation of
phen-ligands stabilize the 4d electrons of low spin octahedral
RuII more than Cl-1 by causing a greater split in the energy field
(shown as deltao<deltao’), which decreases the chances of
unpairing electrons and reacting.
13
Syntheses of [RuII(L)3] complexes were carried out by much the same
method, Scheme 4, but without a stoichiometric excess of the ruthenium starting
N
+
3 equiv
Ru IIICl 3
ethylene glycol, solvent
220 C, 2 h
N'
N
+2
Ru
'N
N'
N
N'
N
SCHEME 4. Synthesis of [RuII(L)3] complexes.
material. The chemistry of the reactions is different since the [RuII(L)3]
syntheses involve the reduction of RuIII to RuII, as well as breaking Ru-Cl bonds
to chelate ligands. It is uncertain how the bond breaking and making is
orchestrated in relation to the reduction of the RuIII. Again, the overall stability
gained in the product of this reaction can be described by a ligand field theory
analysis of the Ru 4d electrons in Figure 5. Both [RuII(L)3](PF6)2 and
Ru III
[RuIIL3]
III
Ru Cl 3
Ru II
eg
eg
delta o'
delta o
4d5
4d6
t2g
t2g
FIGURE 5. Ligand field theory description of why Ru II chelated to phen-ligands
is more stable than RuIII bound to Cl-1. The unpaired electron of RuIII is more
easily excited than any of the lower energy paired electrons of RuII in [RuII(L)3].
14
[RuII(L)3]Cl2 salts were synthesized. The additional planar ring structures of
[RuII(L)3] decreased solubility as compared to [(bpy)2RuII(L)] such that PF6-1
counterions were unnecessary for product precipitation.
The [CuII(phen-pterin)2](NO3)2 and [FeII(L)3]Cl2 syntheses were much
simpler and faster than aforementioned syntheses in that chelation occurred
immediately upon addition of the CuII or FeII starting material to a ligand
solution. The phen nitrogens chelate to CuII in a square planar arrangement.
Though there are six coordination sites on square planar CuII, Jaun-Teller
distortion of the axial bond lengths allow for chelation of only two phen-pterin
ligands, Figure x, so NO3-1 or H2O probably occupy the axial coordination cites on
the CuII complex. FeII reacts quickly with the phenanthroline nitrogens because
they stabilize the arrangement of FeII 3d electrons, similarly to the way in which
they were shown to stabilize RuII in Figure 4, and prevent oxidation to FeIII under
atmospheric conditions. Despite this prediction, the [FeII(L)3] complexes change
color in DMF solution to yellow given a day or two to let stand. This behavior was
first noticed for [FeII(phen-pterin)3] in DMF under regular atmospheric room
temperature conditions. It was speculated that the enamine proton of phenpterin is deprotonated in solution, since this anion is associated a strong yellow
color. Then [FeII(phen-allox)3] solvated in DMF was found to change color in
DMF, making the previous explanation less likely.
NMR and Mass spec. The 1H NMR spectra of [RuII(phen-allox)3] and
[RuII(phen-pterin)3] each had one clean set of peaks. Difficulty dissolving
[RuII(phen-dap)3] prevented the spectrum from being obtained. A single set of
peaks suggests that the arrangement of three ligands on RuII is facial with a C3
axis of symmetry, Figure 3. The mass spec analyses also imply homoleptic
structures. A meridial arrangement of [RuII(L)3] would have two identical
ligands and a third with a separate set of 1H NMR peaks. The sharpness of the
peaks obtained for [RuII(L)3] compounds indicates that the reduction of RuIII to
RuII did take place, as RuIII with 5 4d electrons is paramagnetic, Figure 5, and
would interfere with the magnetic field of an NMR spectrometer.
15
The [FeII(L)3] compounds also had 1H NMR spectra with single sets of
sharp peaks. To test the whether the color change of [FeII(L)3] solutions was
indicative of oxidization to a Fe+3, which would seem to immediately follow the
dissociation of these ligands from FeII, an NMR sample was set aside in a
dessicator for several days. When the solution finally appeared to change colors
from a pinkish red to a pinkish orange a spectrum for the sample was retaken. A
double set of peaks appeared, but the peaks remained sharp suggesting that FeII
had not been oxidized to FeIII. It remains a mystery as to what exactly is causing
the change in color such that [RuII(phen-pterin)3] and [RuII(phen-allox)3] do not
experience this in DMF.
UV/vis. A chart of absorbance wavelengths and the corresponding estimated
extinction coefficients can be found on pages C13-C14 of the Appendix. Data for
the MLCT absorbances of RuII compounds are marked there in. The absorbance
spectrum for [CuII(phen-pterin)2] serves as a diagnostic tool for symmetry about
CuII since the absorbance wavelength for a CuII d-electron excitation is known to
be indicative of the complex’s geometry. Absorbance around 700 nm implies a
square planar configuration of the ligands about CuII.
Electrochemistry. The electrochemical data, along with the E and the E1/2
values, is presented in Appendix D. This will be considered a preliminary
collection of data because certain sets of data are imperfect, which is apparent by
the looks of their graphs. A few Ru+3/Ru+2 values are highlighted in Table 1.
16
Compound
Ea
Ec
[Ru(bpy)3]
1.2949
1.3839
0.089
1.3394
[Ru(bpy)2(dma)](PF6)2
1.5213
1.5677
0.0464
1.5445
[Ru(bpy)2(pallox)](PF6)2
0.8235
1.355
0.5315
1.08925
[Ru(bpy)2(pptn)](PF6)2
1.3888
1.5139
0.1251
1.45135
[Ru(bpy)2(pdiam)](PF6)2
1.3373
1.4854
0.1481
1.41135
[Ru(pallox)3]Cl2
0.8284
1.1056
0.2772
0.967
delta E
E1/2
TABLE 1. The Ru+3\Ru+2 redox potentials for DMF solutions. E values in Volts.
Notice how [(bpy)2RuII(phen-dma)] and and [(bpy)2RuII(phen-phen-allox)]
appear to be structurally similar, but have such different RuIII/RuII E and  E1/2
values. Hence substitution at the end of a ligand does effect the ability of RuII to
be oxidited. This implies that the MLTC, which is thought to change the formal
oxidation state of Ru from +2 to +3, could be tuned by deliberate ligand
substitutions. As speculation, one might say that the methyl substitution in
phen-dma does not allow for a loss of proton and anionization that might be
possible for phen-allox.
It should be noted in this section that after e-chem experiments had been
run with [RuII(phen-allox)3], the compound was found cling to the Pt wire
electrode. This did not happen for experiments with any of the other compounds
tested. Perhaps this behavior has the potential for materials applications.
Crystallization. Compounds were crystallized by first dissolving them in a
polar solvent, acetonitrile of DMF depending upon the compound’s solubility,
followed by the slow diffusion of a non-polar solvent, ether, into the solution.
The most successful set-up is shown in Figure 6. This slowly allows ether vapor
17
FIGURE 6. Lab set-up for solvent diffusion
recrystallization.
into a vial, in which the compound’s solution is contained, to control the rate at
which ether layers on top of and seeps through the solution.
Conclusion
The explanation of electrochemical and UV/vis data needs to be given to
determine just how promising these complexes are electron transports. A close
look at this data may also shed light on the color change that the [FeII(L)3]
complexes undergo in DMF. It would be beneficial to establish protocalls for
enantiomerically pure syntheses of all complexes5. DNA intercalation and lattice
structure are two examples of enantiomer-sensitive topics that are currently
relevant to this project. The study of metal center effects on the ligands can be
expanded by the synthesis of [CoIII(L)3] complexes6.
Acknowledgments
I’d like to thank my research advisor Dr. Sharon Burgmayer for her
guidance of my developing chemistry understanding and for the freedom to
explore the melding of my newfound knowledge with intuitive thought. I highly
18
value the attention that all of my professors have spent their time giving to me
and I thank them all.
I’d also like to thank my peers for their advice, company, and assistance
throughout our undergraduate careers. A special thanks to Mary Kim, ’06, for
her help with syntheses and to Alanna Albano, ’05, for her correspondence
concerning analytical experiments.
This research was made possible by the generous funding of Bryn Mawr
College, for which I am literally greatly indebted (with no regrets!).
19
Appendices
A. NMR and IR spectra
B. Mass spec
C. UV/vis spectra
D. Electrochemical data
20
Appendix A: NMR and IR spectra
Table of Contents
Phen-dione NMR
A1
Phen-dione IR
A2
Phen-dma NMR
A3
Phen-allox NMR
A4
Phen-allox IR
A5
Phen-pterin NMR
A6
Phen-pterin IR
A7
Phen-dap NMR
A8
[(bpy)2RuII(phen-dma)](PF6)2 NMR
A9-10
[(bpy)2RuII(phen-allox)](PF6)2 NMR
A11-12
[(bpy)2RuII(phen-pterin)](PF6)2 NMR
A13
[(bpy)2RuII(phen-dap)](PF6)2 NMR
A14-15
[RuII(phen-allox)3]Cl2 NMR
A16
[RuII(phen-pterin)3]Cl2 NMR
A17
[FeII(phen-allox)3]Cl2 NMR
A18
[FeII(phen-pterin)3]Cl2 NMR
A19
21
Appendix B: Mass spec
Table of Contents
[(bpy)2RuII(phen-dma)](PF6)2
B1
[(bpy)2RuII(phen-allox)](PF6)2
B2
[(bpy)2RuII(phen-pterin)](PF6)2
B3
[(bpy)2RuII(phen-dap)](PF6)2
B4
[RuII(phen-allox)3]Cl2
B5
[RuII(phen-diamino)3]Cl2
B6
[FeII(phen-allox)3]Cl2
B7
[FeII(phen-pterin)3]Cl2
B8
[CuII(phen-pterin)2](NO3)2
B9
22
Appendix C: UV/vis Spectra
Table of Contents
[RuII(bpy)3]Cl2
C1
[(bpy)2RuII(phen-dma)](PF6)2
C2
[(bpy)2RuII(phen-allox)](PF6)2
C3
[(bpy)2RuII(phen-pterin)](PF6)2
C4
[(bpy)2RuII(phen-dap)](PF6)2
C5
[RuII(phen-allox)3]Cl2 NMR
C6
[RuII(phen-pterin)3]Cl2 NMR
C7
[FeII(phen-allox)3]Cl2 NMR
C8
[FeII(phen-pterin)3]Cl2 NMR
C9
[FeII(phen-dap)3]Cl2 NMR
C10
[CuII(phen-pterin)2](NO3)2
C11-12
Table of data and ext. coeff. for comp.s
C13
23
Appendix D: Electrochemical data
Table of Contents
[RuII(bpy)3]Cl2
D1
[(bpy)2RuII(phen-dma)](PF6)2
D2-3
[(bpy)2RuII(phen-allox)](PF6)2
D4
[(bpy)2RuII(phen-pterin)](PF6)2
D5-6
[(bpy)2RuII(phen-dap)](PF6)2
D7
[RuII(phen-allox)3]Cl2 NMR
D8-9
[FeII(phen-allox)3]Cl2 NMR
D10-11
[FeII(phen-pterin)3]Cl2 NMR
D12-13
[FeII(phen-dap)3]Cl2 NMR
D14-15
Phen-dma
D16
Phen-allox
D17
Phen-pterin
D18
Phen-dap
D19
Table of data, E, and E1/2 for comp.s
D20
24
1
Fees, Jorg, W. Kaim, M. Moscherosch, W. Matheis, J. Klima, M. Krejcik, and S. Zalis.
Inorg. Chem. 1993 (32), 166.
2
Burgmayer, Sharon J. N., D. L. Pearsall, S. M. Blaney, E. M. Moore, C. Sauk-Schubert.
J Biol Inor Chem. 2004 (9), 59.
3
Yamada, Masak, Y. Tanaka, Y. Yoshimoto, S. Kuroda, and I. Shimao. Bull. Chem. Soc.
Jpn. 1992 (65), 1006.
4
Black, Kirk J., H. Huang, L. Starks, M. Olson, and M. McGuire. Inorg. Chem. 1993
(32), 5591.
5
Hiort, Catharina, P. Lincoln, and B. Norden. J. Am. Chem. Soc. 1993 (115), 3448.
6
Szafran, Zvi, R. M. Pike, and M. M. Sing. Microscale Inorganic Chemistry: A
Comprehensive Laboratory Experience. John Wiley & Sons, Inc: New York, 1991.
25