Syntheses and properties of complexes with bis(2,2′-bipyridyl) ruthenium(II) moieties coordinated to 4,4′:2′,2′′: 4′′,4′′′-quaterpyridinium ligands

Article abstract of DOI:10.1016/j.poly.2011.04.018

Eleven new complexes of the form cis-[Ru^II(bpy) ₂(L^A)]⁴⁺ (bpy = 2,2′-bipyridyl; L ^A = a pyridinium-substituted bpy derivative) have been prepared and isolated as their PF₆^- salts

Full text of DOI:10.1016/j.poly.2011.04.018

Polyhedron 30 (2011) 1830–1841
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Syntheses and properties of complexes with bis(2,20-bipyridyl)ruthenium(II)
moieties coordinated to 4,40:20,200:400,4000-quaterpyridinium ligands
⇑
Benjamin J. Coe , Elizabeth C. Harper, Madeleine Helliwell, Yien T. Ta
School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK
a r t i c l e i n f o
a b s t r a c t
Eleven new complexes of the form cis-[RuII(bpy)2(LA)]4+ (bpy = 2,20-bipyridyl; LA = a pyridinium-substi-
tuted bpy derivative) have been prepared and isolated as their PF6ꢀ salts. Characterisation involved var-
ious techniques including 1H NMR spectroscopy and MALDI mass spectrometry. The UV–Vis spectra show
Article history:
Received 21 March 2011
Accepted 12 April 2011
Available online 23 April 2011
intense intraligand
p ?
p⁄ absorptions and metal-to-ligand charge-transfer (MLCT) bands with two dis-
tinct maxima in the visible region. Small shifts in the MLCT bands correlate with the electron-withdraw-
ing strength of the ligand LA. Cyclic voltammograms show quasi-reversible or reversible RuIII/II oxidation
waves, and two or more ligand-based reductions with varying degrees of reversibility. The variations in
the redox potentials correlate with changes in the structure of LA, and also with the MLCT energies. Dif-
ferential pulse voltammetry allows the first reduction process for two of the complex salts to be resolved
into two peaks. Single-crystal X-ray structures have been solved for three of the new complex salts and
also for a pro-ligand salt. Two carboxylate-functionalised compounds have been tested as photosensitiz-
ers on TiO2-coated electrodes, but show only negligible efficiencies, in accord with expectations.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Ruthenium complexes
Polypyridyl ligands
1. Introduction
ture is now a very well developed area of coordination chemistry
[4].
Amongst the transition metals, ruthenium displays an espe-
cially diverse coordination and organometallic chemistry, includ-
ing a vast array of stable complexes with every conceivable type
of ligand [1]. An ideal combination of relatively high stability and
synthetic accessibility has underpinned the development of this
field. Of the range of formal oxidation states available to this metal,
the +2 and +3 ions are especially widely studied. In addition to
pure chemical interest and fundamental scientific value, Ru com-
plexes have attracted attention for practical applications in a num-
ber of important areas including catalysis [2], medicine [3], and
technologies that exploit the photophysical/chemical properties
of RuII-based chromophores [4]. The latter encompass fields such
as organic light-emitting diodes [5] and dye-sensitized solar cells
[6]. Such applications based on photoactivity involve complexes
of chelating polypyridyl ligands, of which [RuII(bpy)3]2+ (RuTB;
bpy = 2,20-bipyridyl) is the prototype [7]. The rich electronic
absorption, emission and electron-transfer properties of RuTB
and related complexes arise from the presence of low energy me-
tal-to-ligand charge-transfer (MLCT) excited states. The ability to
tune the properties of such states via modifications in ligand struc-
Another area in which Ru complexes have featured extensively
is that of nonlinear optical (NLO) chromophores and materials [8].
As part of our ongoing studies in this field, we have investigated a
number of complexes of 4,40:20,200:400,4000-quaterpyridinium ligands.
These include V-shaped dipolar structures with electron-rich cis-
{RuII(NH3)4}2+ centres [9], as well as octupolar tris-chelates that
are derivatives of RuTB [10,11]. These complexes show especially
intense, broad MLCT absorption profiles, which in the case of the
tris-chelates feature two well-resolved bands. The MLCT transi-
tions are associated with relatively large second- and third-order
NLO responses [9–11]. The present study involves a series of new
complexes that can be viewed as hybrids of those reported previ-
ously, in that they contain a RuTB core but with only one quaterpy-
ridinium ligand. The optical spectroscopic and electrochemical
properties of the new species are compared with those of the exist-
ing compounds, and several X-ray crystallographic studies are
presented.
2. Experimental
2.1. Materials, procedures and physical measurements
⇑
Corresponding author. Tel.: +44 (0)161 275 4601; fax: +44 (0)161 275 4598.
E-mail addresses: B.Coe@man.ac.uk, b.coe@manchester.ac.uk (B.J. Coe).
All reactions were performed under an Ar atmosphere. The com-
URL:
http://www.chemistry.manchester.ac.uk/aboutus/staff/show.html?ea=
Benjamin.Coe (B.J. Coe).
pounds cis-RuIICl2(bpy)2ꢁ2H2O [12], 4,40-di[(E)-2-(N-methyl-4-pyri-
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.04.018

B.J. Coe et al. / Polyhedron 30 (2011) 1830–1841
1831
dyl)vinyl]-2,20-bipyridyl iodide ([Me2bbpe2+]I2) [13], 4,40-di[(E)-2-
(N-phenyl-4-pyridyl)vinyl]-2,20-bipyridyl chloride ([Ph2bbpe2+]Cl2)
[13], and 4,40-di{(E)-2-[N-(2,4-dinitrophenyl)-4-pyridyl]vinyl}-2,20-
bipyridyl chloride ([(2,4-DNPh)2bbpe2+]Cl2) [13], were prepared
according to published procedures. The compounds N00,N000-diphe-
nyl-4,40:20,200:400,4000-quaterpyridinium chloride ([Ph2qpy2+]Cl2) [9],
N00,N000-di(4-acetylphenyl)-4,40:20,200:400,4000-quaterpyridinium chlo-
ride ([(4-AcPh)2qpy2+]Cl2) [9], N00,N000-di(2-pyrimidyl)-4,40:20,200:400,
4000-quaterpyridinium chloride ([(2-Pym)2qpy2+]Cl2) [9], N00,N000-
di(2,4-dinitrophenyl)-4,40:20,200:400,4000-quaterpyridinium chloride
([(2,4-DNPh)2qpy2+]Cl2) [10] and N00,N000-di(3,5-bismethoxycarbon-
(5 ꢂ 10 mL). The crude yellow solid, [Me2qpy2+]I2, was stirred in
warm ethanol (250 mL), then filtered off. The solid was dissolved
in water (200 mL) and addition of aqueous NH4PF6 afforded a
cream-coloured precipitate, [Me2qpy2+][PF6]2, which was filtered
off, washed with water and dried. The solid was dissolved in ace-
tone (300 mL), the solution filtered, and [NBun4]Cl in acetone was
added to the filtrate. The cream-coloured precipitate was filtered
off, washed with acetone and dried. Yield: 398 mg (54%). dH
(400 MHz, CD3OD) 9.09 (4H, d, J = 6.8 Hz, C5H4N), 9.04 (2H, dd,
J = 1.9, 0.6 Hz, C5H3N), 9.01 (2H, dd, J = 5.0, 0.8 Hz, C5H3N), 8.62
(4H, d, J = 7.1 Hz, C5H4N), 8.07 (2H, dd, J = 5.2, 1.9 Hz, C5H3N),
4.51 (6H, s, 2Me). Anal. Calc. (%) for C22H20Cl2N4ꢁ3.1H2O: C,
56.56; H, 5.65; N, 11.99. Found: C, 56.45; H, 5.27; N, 11.97%. ES-
MS: m/z = 375 ([MꢀCl]+), 170 ([Mꢀ2Cl]2+).
ylphenyl)-4,40:20,200:400,4000-quaterpyridinium
chloride
([(3,5-
MC2Ph)2qpy2+]Cl2) [10] were prepared by modifying published
methodsin whichthese chloride salts were treatedas intermediates,
with no analytical data being obtained. All other reagents were ob-
tained commercially and used as supplied. Products were dried
overnight in a vacuum dessicator (CaSO4) prior to characterisation.
1H NMR spectra were recorded on a Bruker AV-400 spectrome-
ter and all shifts are quoted with respect to TMS. The fine splitting
of pyridyl or phenyl ring AA0BB0 patterns is ignored and the signals
are reported as simple doublets, with J values referring to the two
most intense peaks. In cases where there is any uncertainty about
their assignments, based on splitting patterns and integrals, signals
for pyridyl (C5H3N or C5H4N) ring protons are denoted simply by
‘‘py’’. Elemental analyses were performed by the Microanalytical
Laboratory, University of Manchester. IR spectroscopy was per-
formed on solid samples by using an Excalibur BioRad FT-IR spec-
trometer, and UV–Vis spectra were obtained by using a Shimadzu
UV-2401 PC spectrophotometer. Mass spectra were measured by
using +electrospray on a Micromass Platform II spectrometer or
MALDI on a Micromass Tof Spec 2e with acetonitrile as the solvent.
Cyclic and differential pulse voltammetric measurements were
carried out with an Ivium CompactStat. An EG&G PAR K0264 sin-
gle-compartment microcell was used with a silver/silver chloride
reference electrode (3 M NaCl, saturated AgCl) separated by a salt
bridge from a glassy carbon disc working electrode and Pt wire
auxiliary electrode. Acetonitrile was freshly distilled (from CaH2)
and [NBun4]PF6, as supplied from Fluka, was used as the supporting
electrolyte. Solutions containing ca. 10ꢀ3 M analyte (0.1 M electro-
lyte) were deaerated by purging with N2. All E1/2 values were cal-
2.2.3. N00,N000-Diphenyl-4,40:20,200:400,4000-quaterpyridinium chloride,
[Ph2qpy2+]Cl2
A mixture of qpyꢁ0.5H2O (500 mg, 1.57 mmol) and 2,4-dinitro-
chlorobenzene (3.17 g, 15.7 mmol) in ethanol (40 mL) was heated
at reflux for 72 h. The solution was allowed to cool and chloroform
(30 mL) was added to give a pale brown precipitate, [(2,4-
DNPh)2qpy2+]Cl2, which was filtered off and washed with diethyl
ether. The solid was dissolved in DMSO (30 mL) and aniline
(1.5 mL) was added. The resulting solution was stirred at 70 °C
for 3 h, cooled and then filtered. Acetone (100 mL) was added
and a peach-coloured precipitate, [Ph2qpy2+]Cl2, was filtered off.
The solid was dissolved in water (100 mL) before addition of aque-
ous NH4PF6 to give a beige precipitate, [Ph2qpy2+][PF6]2, which was
filtered off. The solid was dissolved in acetone (50 mL) and
[NBun4]Cl in acetone was added to yield a cream-coloured precip-
itate which was filtered off, washed with acetone and dried. Yield:
488 mg (56%). dH (400 MHz, CD3OD) 9.43 (4H, d, J = 7.1 Hz, C5H4N),
9.17 (2H, dd, J = 1.9, 0.9 Hz, C5H3N), 9.08 (2H, dd, J = 5.0, 0.8 Hz,
C5H3N), 8.81 (4H, d, J = 7.1 Hz, C5H4N), 8.18 (2H, dd, J = 5.2,
1.9 Hz, C5H3N), 7.95–7.91 (4H, Ph), 7.83–7.79 (6H, Ph). Anal. Calc.
(%) for C32H24Cl2N4ꢁH2O: C, 69.44; H, 4.73; N, 10.12. Found: C,
69.14; H, 4.92; N, 10.04%. ES-MS: m/z = 499 ([MꢀCl]+), 232
([Mꢀ2Cl]2+).
2.2.4. N00,N000-Di(4-acetylphenyl)-4,40:20,200:400,4000-quaterpyridinium
chloride, [(4-AcPh)2qpy2+]Cl2
culated from (Epa + Epc)/2 at a scan rate of 200 mV sꢀ1
.
This compound was prepared in
a manner similar to
2.2. Syntheses
[Ph2qpy2+]Cl2 by using 4-aminoacetophenone (4.01 g, 29.6 mmol)
instead of aniline, and the mixture was heated at reflux in ethanol
(50 mL) for 50 h. The resulting brown solution was reduced in vol-
ume and acetone (200 mL) was added to give a brown precipitate,
[(4-AcPh)2qpy2+]Cl2, which was filtered off. The solid was dissolved
in water (100 mL) and extracted with chloroform (3 ꢂ 200 mL).
Aqueous NH4PF6 was added to the aqueous layer yielding a pale
brown precipitate, [(4-AcPh)2qpy2+][PF6]2, which was filtered off
and dried. The solid was dissolved in acetone (70 mL) and filtered.
[NBun4]Cl in acetone was added to the filtrate to afford a pale
brown solid which was filtered off, washed with acetone and dried.
Yield: 448 mg (44%). dH (400 MHz, CD3OD) 9.48 (4H, d, J = 7.1 Hz,
C5H4N), 9.18 (2H, d, J = 1.3 Hz, C5H3N), 9.09 (2H, d, J = 5.3 Hz,
C5H3N), 8.85 (4H, d, J = 7.1 Hz, C5H4N), 8.39 (4H, d, J = 8.8 Hz,
C6H4), 8.19 (2H, dd, J = 5.0, 1.8 Hz, C5H3N), 8.07 (4H, d, J = 8.6 Hz,
2.2.1. 4,40:20,200:400,4000-Quaterpyridyl, qpy
A mixture of 4,40-bipyridyl (10.0 g, 64.0 mmol) and 10% Pd on
charcoal (2.00 g) was heated at ca. 250 °C for 48 h and then cooled
to room temperature. Aqueous HCl (2 M, 250 mL) was added, and
the black suspension was filtered. Aqueous NaOH (8 M, 75 mL)
was added dropwise to the stirred brown filtrate to afford a grey
precipitate which was filtered off, washed with water and dried.
Purification was achieved by using a silica gel column, eluting with
95:5, followed by 90:10 dichloromethane/methanol after removal
of unreacted starting material. The product was obtained as a
cream-coloured solid. Yield: 1.86 g (18%). dH (400 MHz, CDCl3)
8.83 (2H, dd, J = 5.0, 0.8 Hz, C5H3N), 8.79–8.77 (6H,
C5H3N + C5H4N), 7.68 (4H, d, J = 6.0 Hz, C5H4N), 7.61 (2H, dd,
J = 5.0, 1.8 Hz, C5H3N). Anal. Calc. (%) for C20H14N4ꢁ0.5H2O: C,
75.22; H, 4.73; N, 17.54. Found: C, 75.49; H, 4.42; N, 17.44%.
C6H4), 2.74 (6H, s, Me).
m
(C@O) 1682s cmꢀ1. Anal. Calc. (%) for
C
36H28Cl2N4O4ꢁ1.8H2O: C, 66.32; H, 4.89; N, 8.59. Found: C,
66.36; H, 4.92; N, 8.88%. ES-MS: m/z = 583 ([MꢀCl]+), 274
([Mꢀ2Cl]2+).
2.2.2. N00,N000-Dimethyl-4,40:20,200:400,4000-quaterpyridinium chloride,
[Me2qpy2+]Cl2
A solution of qpyꢁ0.5H2O (500 mg, 1.57 mmol) and methyl io-
dide (2 mL) in acetone (50 mL) was heated at reflux for 4 h. The
solution was cooled and a yellow precipitate was filtered off and
washed with acetone (50 mL) followed by chloroform
2.2.5. N00,N000-Di(2-pyrimidyl)-4,40:20,200:400,4000-quaterpyridinium
chloride, [(2-Pym)2qpy2+]Cl2
A mixture of qpyꢁ0.5H2O (500 mg, 1.57 mmol) and 2-chloropyr-
imidine (1.80 g, 15.7 mmol) was heated at 120 °C. Ethanol (15 mL)

1832
B.J. Coe et al. / Polyhedron 30 (2011) 1830–1841
was added to the resulting green solution and the mixture was
heated at reflux for 4 h. The solution was allowed to cool and
diethyl ether (100 mL) was added to give a pale brown precipitate,
[(2-Pym)2qpy2+]Cl2, which was filtered off. The solid was dissolved
in water and aqueous NH4PF6 was added to give a brown precipi-
tate, [(2-Pym)2qpy2+][PF6]2, which was filtered off and dried. The
solid was dissolved in acetone (150 mL) and filtered. [NBun4]Cl in
acetone was added to the filtrate to give a pale brown precipitate
which was filtered off, washed with acetone and dried. Yield:
827 mg (91%). dH (400 MHz, CD3OD) 10.33 (4H, d, J = 7.3 Hz,
C5H4N), 9.22 (4H, d, J = 4.8 Hz, C4H3N2), 9.21 (2H, d, J = 0.8 Hz,
C5H3N), 9.10 (2H, dd, J = 5.3, 0.8 Hz, C5H3N), 8.90 (4H, d,
J = 7.3 Hz, C5H4N), 8.21 (2H, dd, J = 5.2, 1.9 Hz, C5H3N), 7.94 (2H,
t, J = 4.9 Hz, C4H3N2). Anal. Calc. (%) for C28H20Cl2N8ꢁ2.3H2O: C,
57.90; H, 4.27; N, 19.29. Found: C, 57.87; H, 4.05; N, 19.12%. ES-
MS: m/z = 503 ([MꢀCl]+), 234 ([Mꢀ2Cl]2+).
60.40; H, 4.88; N, 7.75%. ES-MS: m/z = 615 ([MꢀCl]+), 290
([Mꢀ2Cl]2+).
2.2.9. cis-[RuII(bpy)2qpy][PF6]2 (1)
A solution of cis-RuIICl2(bpy)2ꢁ2H2O (100 mg, 0.192 mmol) and
qpyꢁ0.5H2O (61 mg, 0.191 mmol) in ethylene glycol (20 mL) was
heated at reflux for 1 h. The dark red/orange solution was allowed
to cool to room temperature and filtered. Aqueous NH4PF6 was
added to the filtrate and a dark red precipitate was filtered off
and washed with water. Purification was achieved by using a silica
gel column, eluting with 0.3 M NH4PF6 in 1:1 acetone/acetonitrile
to remove an initial orange band, then with 0.3 M NH4PF6 in ace-
tone to remove the major red product band. The red fraction was
evaporated to dryness, washed with water and dried to yield a
bright orange solid. Yield: 92 mg (47%). dH (400 MHz, CD3COCD3)
9.43 (2H, d, J = 1.5 Hz, a), 8.85 (4H, d, J = 8.3 Hz, C5H4N), 8.81 (4H,
d, J = 5.6 Hz, b), 8.26–8.21 (6H, py), 8.19–8.17 (2H, m, py), 8.10–
8.08 (2H, m, py), 7.98 (2H, dd, J = 6.1, 2.0 Hz, py), 7.94 (4H, d,
J = 6.3 Hz, C5H4N), 7.63–7.56 (4H, py). Anal. Calc. (%) for
2.2.6. N00,N000-Di(2,4-dinitrophenyl)-4,40:20,200:400,4000-quaterpyridinium
chloride, [(2,4-DNPh)2qpy2+]Cl2
The reaction to prepare [(2,4-DNPh)2qpy2+]Cl2 was exactly as in
the procedure for [Ph2qpy2+]Cl2. The solution was allowed to cool
and chloroform (20 mL) was added to produce a cream-coloured
precipitate which was filtered off and washed with diethyl ether.
Purification was effected by reprecipitation from MeOH/diethyl
ether. Yield: 972 mg (85%). dH (400 MHz, CD3OD) 9.48 (4H, d,
J = 7.3 Hz, C5H4N), 9.33 (2H, d, J = 2.5 Hz, C6H3N2O4), 9.22 (2H, dd,
J = 2.0, 0.8 Hz, C5H3N), 9.11 (2H, dd, J = 5.3, 0.8 Hz, C5H3N), 8.99–
8.94 (6H, C5H4N + C6H3N2O4), 8.40 (2H, d, J = 8.6 Hz, C6H3N2O4),
C
40H30F12N8P2RuꢁH2O: C, 46.56; H, 3.13; N, 10.86. Found: C,
46.70; H, 2.82; N, 10.79%. MALDI-MS: m/z = 870 ([MꢀPF6]+), 725
([Mꢀ2PF6]+).
2.2.10. cis-[RuII(bpy)2(Me2qpy2+)][PF6]4 (2)
This compound was prepared and purified in a manner similar
to 1 by using [Me2qpy2+]Cl2ꢁ3.1H2O (79 mg, 0.169 mmol) instead of
qpyꢁ0.5H2O and ethanol (50 mL) instead of ethylene glycol, with a
reflux time of 2 h. The column was eluted with 0.1 M NH4PF6 in
acetonitrile, and the first red band afforded a dark red solid. Yield:
114 mg (49%). dH (400 MHz, CD3COCD3) 9.48 (2H, d, J = 1.8 Hz, a),
9.21 (4H, d, J = 7.1 Hz, b), 8.85 (4H, d, J = 8.3 Hz, C5H4N), 8.71 (4H,
d, J = 6.8 Hz, C5H4N), 8.40 (2H, d, J = 6.1 Hz, py), 8.28–8.22 (4H, m,
C5H4N), 8.15–8.13 (4H, py), 8.07 (2H, dd, J = 5.6, 0.8 Hz, py),
7.64–7.60 (2H, m, py), 7.57–7.54 (2H, m, py), 4.69 (6H, s, Me). Anal.
Calc. (%) for C42H36F24N8P4Ruꢁ3H2O: C, 36.35; H, 3.05; N, 8.07.
Found: C, 36.39; H, 2.59; N, 8.02%. MALDI-MS: m/z = 1184
([MꢀPF6]+), 1039 ([Mꢀ2PF6]+), 896 ([Mꢀ3PF6]+), 751 ([Mꢀ4PF6]+).
8.23 (2H, dd, J = 5.2, 1.9 Hz, C5H3N).
mas(NO2) 1535vs, ms(NO2)
1342vs cmꢀ1. Anal. Calc. (%) for C32H20Cl2N8O8ꢁ0.5H2O: C, 53.05;
H, 2.92; N, 15.47. Found: C, 53.24; H, 2.67; N, 15.01%. ES-MS: m/
z = 679 ([MꢀCl]+), 322 ([Mꢀ2Cl]2+).
2.2.7. N00,N000-Di(3,5-bismethoxycarbonylphenyl)-4,40:20,200:400,4000-
quaterpyridinium chloride, [(3,5-MC2Ph)2qpy2+]Cl2
This compound was prepared in a manner similar to [(4-AcPh)2q-
py2+]Cl2 by using dimethoxy-5-aminoisophthalate (3.27 g,
15.6 mmol) instead of 4-aminoacetophenone. The red/orange solu-
tion was evaporated to dryness and the solid was washed with ace-
tone (150 mL) under filtration. The resulting yellow solid was
dissolved in water (200 mL) and extracted with chloroform
(3 ꢂ 200 mL). The aqueous layer was concentrated under vacuum.
Acetone was added to the pale green solution, affording a cream-col-
oured precipitate which was filtered off, washed with acetone and
dried. Yield: 876 mg (69%). dH (400 MHz, CD3OD) 9.51 (4H, d,
J = 7.1 Hz, C5H4N), 9.20 (2H, d, J = 1.3 Hz, C5H3N), 9.09 (2H, d,
J = 5.3 Hz, C5H3N), 8.95 (2H, t, J = 1.5 Hz, C6H3), 8.86 (4H, d,
J = 7.1 Hz, C5H4N), 8.78 (4H, d, J = 1.5 Hz, C6H3), 8.20 (2H, dd,
2.2.11. cis-[RuII(bpy)2(Ph2qpy2+)][PF6]4 (3)
This compound was prepared and purified in a manner similar
to 2 by using cis-RuIICl2(bpy)2ꢁ2H2O (93 mg, 0.179 mmol) and
[Ph2qpy2+]Cl2ꢁH2O (96 mg, 0.173 mmol) instead of [Me2q-
py2+]Cl2ꢁ3.1H2O to afford a dark red solid. Yield: 106 mg (41%). dH
(400 MHz, CD3COCD3) 9.57 (2H, d, J = 1.8 Hz, a), 9.53 (4H, d,
J = 7.1 Hz, b), 8.87 (8H, d, J = 7.1 Hz, C5H4N), 8.46 (2H, d,
J = 6.1 Hz, py), 8.29–8.24 (4H, m, C5H4N), 8.22 (2H, dd, J = 6.0,
2.0 Hz, py), 8.17 (2H, dd, J = 5.6, 0.8 Hz, py), 8.09 (2H, dd, J = 5.7,
0.6 Hz, py), 8.00–7.98 (4H, Ph), 7.84–7.80 (6H, Ph), 7.66–7.62
(2H, m, py), 7.60–7.56 (2H, m, py). Anal. Calc. (%) for
J = 5.2, 1.9 Hz, C5H3N), 4.05 (12H, s, Me). m
(C@O) 1721s cmꢀ1. Anal.
Calc. (%) for C40H32Cl2N4O8ꢁ2H2O: C, 59.78; H, 4.52; N, 6.97. Found:
C, 59.60; H, 4.31; N, 6.99%. ES-MS: m/z = 731 ([MꢀCl]+), 348
([Mꢀ2Cl]2+).
C
52H40F24N8P4Ruꢁ2H2O: C, 41.81; H, 2.97; N, 7.50. Found: C,
41.81; H, 2.69; N, 7.37%. MALDI-MS: m/z = 1309 ([MꢀPF6]+), 1165
([Mꢀ2PF6]+), 1021 ([Mꢀ3PF6]+), 878 ([Mꢀ4PF6]+).
All of the compounds 4–11 were prepared and purified in a
manner similar to 2 by using the appropriate pro-ligand salt, giving
dark red solids.
2.2.8. N00,N000-Di(4-methoxycarbonylphenyl)-4,40:20,200:400,4000-
quaterpyridinium chloride, [(4-MCPh)2qpy2+]Cl2
This compound was prepared in a manner similar to [(3,5-
MC2Ph)2qpy2+]Cl2 by using methyl-4-aminobenzoate (2.37 g,
15.7 mmol) instead of dimethoxy-5-aminoisophthalate, and a re-
flux time of 72 h. Reprecipitation from methanol/diethyl ether
gave the pure product as a pale brown solid. Yield: 326 mg
(29%). dH (400 MHz, CD3OD) 9.48 (4H, d, J = 7.1 Hz, C5H4N), 9.18
(2H, d, J = 1.3 Hz, C5H3N), 9.09 (2H, dd, J = 5.2, 0.6 Hz, C5H3N),
8.85 (4H, d, J = 7.1 Hz, C5H4N), 8.41 (4H, d, J = 8.8 Hz, C6H4), 8.19
(2H, dd, J = 5.0, 2.0 Hz, C5H3N), 8.07 (4H, d, J = 8.8 Hz, C6H4), 4.01
2.2.12. cis-[RuII(bpy)2{(4-AcPh)2qpy2+}][PF6]4 (4)
Used [(4-AcPh)2qpy2+]Cl2ꢁ1.8H2O (119 mg, 0.183 mmol). Yield:
109 mg (38%). dH (400 MHz, CD3COCD3) 9.59 (4H, d, J = 7.1 Hz, b),
9.55 (2H, d, J = 1.8 Hz, a), 8.90–8.86 (8H, py), 8.46 (2H, d,
J = 6.1 Hz, py), 8.37 (4H, d, J = 9.1 Hz, C6H4), 8.29–8.24 (4H, m,
C5H4N), 8.22 (2H, dd, J = 6.0, 2.0 Hz, py), 8.18–8.14 (6H, py + C6H4),
8.09 (2H, dd, J = 5.6, 0.8 Hz, py), 7.66–7.62 (2H, m, py), 7.60–7.56
(6H, s, Me).
m
(C@O) 1720s cmꢀ1
.
Anal. Calc. (%) for
(2H, m, py), 2.72 (6H, s, Me).
for C56H44F24N8O2P4Ruꢁ2H2O: C, 42.62; H, 3.07; N, 7.10. Found: C,
m
(C@O) 1680s cmꢀ1. Anal. Calc. (%)
C36H28Cl2N4O4ꢁ3.5H2O: C, 60.51; H, 4.94; N, 7.84. Found: C,

B.J. Coe et al. / Polyhedron 30 (2011) 1830–1841
1833
42.52; H, 2.76; N, 7.07%. MALDI-MS: m/z = 1393 ([MꢀPF6]+), 1249
[Mꢀ2PF6]+), 1104 ([Mꢀ3PF6]+), 960 [Mꢀ4PF6]+).
2.2.18. cis-[RuII(bpy)2(Ph2bbpe2+)][PF6]4 (10)
Used [Ph2bbpe2+]Cl2ꢁ4.5H2O (113 mg, 0.169 mmol). Yield:
143 mg (54%). dH (400 MHz, CD3COCD3) 9.38 (4H, d, J = 7.1 Hz, b),
9.12 (2H, d, J = 1.5 Hz, a), 8.85 (4H, d, J = 8.2 Hz, C5H4N), 8.54 (4H,
d, J = 7.1 Hz, C5H4N), 8.29–8.20 (10H, py + CH), 8.12 (2H, d,
J = 16.4 Hz, CH), 8.07 (2H, dd, J = 5.6, 0.8 Hz, py), 8.03–8.01 (4H,
Ph), 7.87 (2H, dd, J = 6.1, 1.8 Hz, py), 7.83–7.79 (6H, Ph), 7.63–
7.58 (4H, py). Anal. Calc. (%) for C56H44F24N8P4Ruꢁ3H2O: C, 43.01;
H, 3.22; N, 7.16. Found: C, 43.08; H, 2.83; N, 7.00%. MALDI-MS:
m/z = 1365 ([MꢀPF6]+), 1220 ([Mꢀ2PF6]+), 1075 ([Mꢀ3PF6]+), 931
([Mꢀ4PF6]+).
2.2.13. cis-[RuII(bpy)2{(2-Pym)2qpy2+}][PF6]4 (5)
Used [(2-Pym)2qpy2+]Cl2ꢁ2.3H2O (104 mg, 0.179 mmol). Yield:
122 mg (46%). dH (400 MHz, CD3COCD3) 10.36 (4H, d, J = 7.6 Hz,
b), 9.61 (2H, d, J = 1.5 Hz, a), 9.29 (4H, d, J = 4.8 Hz, C4H3N2), 9.00
(4H, d, J = 7.6 Hz, C5H4N), 8.88 (4H, d, J = 8.3 Hz, C5H4N), 8.52 (2H,
d, J = 6.1 Hz, py), 8.31–8.24 (6H, py), 8.19 (2H, dd, J = 5.8, 0.8 Hz,
py), 8.10 (2H, dd, J = 5.8, 0.8 Hz, py), 8.05 (2H, t, J = 4.8 Hz,
C4H3N2), 7.67–7.63 (2H, m, py), 7.60–7.56 (2H, m, py). Anal. Calc.
(%) for C48H36F24N12P4Ruꢁ2H2O: C, 38.49; H, 2.69; N, 11.22. Found:
C, 38.41; H, 2.46; N, 10.89%. MALDI-MS: m/z = 1319 ([MꢀPF6]+),
1173 ([Mꢀ2PF6]+), 1029 ([Mꢀ3PF6]+), 884 ([Mꢀ4PF6]+).
2.2.19. cis-[RuII(bpy)2{(2,4-DNPh)2bbpe2+}][PF6]4 (11)
Used [(2,4-DNPh)2bbpe2+]Cl2ꢁ3.8H2O (148 mg, 0.177 mmol).
Yield: 106 mg (35%). dH (400 MHz, CD3COCD3) 9.40 (4H, d,
J = 7.1 Hz, b), 9.27 (2H, d, J = 2.5 Hz, C6H3), 9.13 (2H, d, J = 1.3 Hz,
a), 9.04 (2H, dd, J = 8.6, 2.5 Hz, C6H3), 8.85 (4H, d, J = 7.8 Hz,
C5H4N), 8.65–8.63 (6H, py + C6H3), 8.35 (2H, d, J = 16.4 Hz, CH),
8.27–8.20 (8H, py), 8.16 (2H, d, J = 16.4 Hz, CH), 8.08 (2H, dd,
J = 5.6, 0.8 Hz, py), 7.88 (2H, dd, J = 6.1, 1.8 Hz, py), 7.63–7.58
2.2.14. cis-[RuII(bpy)2{(2,4-DNPh)2qpy2+}][PF6]4 (6)
Used [(2,4-DNPh)2qpy2+]Cl2ꢁ0.5H2O (138 mg, 0.190 mmol).
Yield: 110 mg (34%). dH (400 MHz, CD3COCD3) 9.63 (2H, d,
J = 1.8 Hz, a), 9.58 (4H, d, J = 7.1 Hz, b), 9.28 (2H, d, J = 2.5 Hz,
C6H3), 9.05 (2H, dd, J = 8.6, 2.5 Hz, C6H3), 9.01 (4H, d, J = 7.1 Hz,
C5H4N), 8.88 (4H, d, J = 8.1 Hz, C5H4N), 8.57 (2H, d, J = 8.6 Hz,
C6H3), 8.53 (2H, d, J = 6.0 Hz, py), 8.30–8.25 (6H, py), 8.18 (2H, d,
J = 5.6 Hz, py), 8.10 (2H, d, J = 5.3 Hz, py), 7.67–7.63 (2H, m, py),
(4H, py). mas(NO2) 1545s, m
s(NO2) 1344s cmꢀ1. Anal. Calc. (%) for
C
56H40F24N12O8P4Ruꢁ2H2O: C, 38.97; H, 2.57; N, 9.74. Found: C,
38.84; H, 2.41; N, 9.50%. MALDI-MS: m/z = 1546 ([MꢀPF6]+), 1401
([Mꢀ2PF6]+).
7.61–7.58 (2H, m, py). mas(NO2) 1543s, m
s(NO2) 1344s cmꢀ1. Anal.
Calc. (%) for C52H36F24N12O8P4Ruꢁ3H2O: C, 36.91; H, 2.50; N, 9.93.
Found: C, 36.85; H, 2.12; N, 9.69%. MALDI-MS: m/z = 1487
([MꢀPF6]+), 1342 ([Mꢀ2PF6]+), 1200 ([Mꢀ3PF6]+).
2.2.20. cis-[RuII(bpy)2{[3,5-(CO2H)2Ph]2qpy2+}][PF6]4 (12)
7Å2H2O (159 mg, 0.092 mmol) was dissolved in acetone (15 mL)
and [NBun4]Cl in acetone was added to give cis-[RuII(bpy)2{(3,5-
MC2Ph)2qpy2+}]Cl4 (141 mg), which was filtered off. 100 mg of
the latter material was added to tert-butanol (25 mL), followed
by concentrated H2SO4 (1 mL), and the mixture was heated at re-
flux for 24 h. After cooling, aqueous NH4PF6 was added to afford
a dark red solid which was filtered off, washed with water and
dried. Yield: 86 mg (80%). dH (400 MHz, CD3COCD3) 9.72 (4H, d,
J = 7.1 Hz, b), 9.61 (2H, d, J = 1.8 Hz, a), 8.96 (4H, d, J = 7.1 Hz,
C5H4N), 8.92 (2H, t, J = 1.4 Hz, C6H3), 8.88 (4H, d, J = 8.3 Hz,
C5H4N), 8.79 (4H, d, J = 1.5 Hz, C6H3), 8.48 (2H, d, J = 6.1 Hz, py),
8.30–8.25 (6H, py), 8.18 (2H, d, J = 5.6 Hz, py), 8.09 (2H, dd,
J = 5.7, 0.9 Hz, py), 7.67–7.63 (2H, m, py), 7.61–7.57 (2H, m, py).
2.2.15. cis-[RuII(bpy)2{(3,5-MC2Ph)2qpy2+}][PF6]4 (7)
Used [(3,5-MC2Ph)2qpy2+]Cl2ꢁ2H2O (148 mg, 0.184 mmol).
Yield: 159 mg (50%). dH (400 MHz, CD3COCD3) 9.68 (4H, d,
J = 7.1 Hz, b), 9.55 (2H, d, J = 1.5 Hz, a), 8.94 (4H, d, J = 7.1 Hz,
C5H4N), 8.88–8.85 (6H, C5H4N + C6H3), 8.80 (4H, d, J = 1.3 Hz,
C6H3), 8.47 (2H, d, J = 6.1 Hz, py), 8.30–8.23 (6H, py), 8.18 (2H,
dd, J = 5.8, 0.8 Hz, py), 8.09 (2H, dd, J = 5.8, 0.8 Hz, py), 7.66–7.63
(2H, m, py), 7.61–7.57 (2H, m, py), 4.00 (12H, s, Me).
m(C@O)
1717s cmꢀ1
.
Anal. Calc. (%) for C60H48F24N8O8P4Ruꢁ2H2O: C,
m
(C@O) 1713s cmꢀ1. Anal. Calc. (%) for C56H40F24N8O8P4Ru: C,
41.75; H, 3.04; N, 6.49. Found: C, 41.97; H, 2.81; N, 6.42%. MAL-
DI-MS: m/z = 1542 ([MꢀPF6]+), 1397 ([Mꢀ2PF6]+), 1253
([Mꢀ3PF6]+), 1108 ([Mꢀ4PF6]+).
41.16; H, 2.47; N, 6.86. Found: C, 41.40; H, 2.70; N, 6.48%. MAL-
DI-MS: m/z = 1344 ([Mꢀ2PF6]+), 1199 ([Mꢀ3PF6]+), 1055
([Mꢀ4PF6]+).
2.2.16. cis-[RuII(bpy)2{(4-MCPh)2qpy2+}][PF6]4 (8)
2.2.21. cis-[RuII(bpy)2{[4-(CO2H)Ph]2qpy2+}][PF6]4 (13)
Used [(4-MCPh)2qpy2+]Cl2ꢁ3.5H2O (125 mg, 0.175 mmol). Yield:
154 mg (53%). dH (400 MHz, CD3COCD3) 9.59 (4H, d, J = 7.3 Hz, b),
9.55 (2H, d, J = 1.8 Hz, a), 8.90–8.86 (8H, C5H4N), 8.46 (2H, d,
J = 6.1 Hz, py), 8.38 (4H, d, J = 8.8 Hz, C6H4), 8.29–8.24 (4H, m,
C5H4N), 8.22 (2H, dd, J = 6.0, 2.0 Hz, py), 8.17–8.14 (6H, py + C6H4),
8.09 (2H, dd, J = 5.6, 0.8 Hz, py), 7.66–7.62 (2H, m, py), 7.60–7.57
This compound was prepared in a manner similar to 12 by con-
verting 8Å4H2O (154 mg, 0.094 mmol) into cis-[RuII(bpy)2{(4-
MCPh)2qpy2+}]Cl4 (118 mg), and hydrolysing 100 mg of this mate-
rial. The resulting dark red solid was purified by reprecipitation
from acetone/diethyl ether. Yield: 85 mg (69%). dH (400 MHz,
CD3COCD3) 9.64 (2H, s, a), 9.60 (4H, d, J = 6.8 Hz, b), 8.95 (4H, d,
J = 6.8 Hz, C5H4N), 8.88 (4H, d, J = 8.3 Hz, C5H4N), 8.47 (2H, d,
J = 6.3 Hz, py), 8.39 (4H, d, J = 8.6 Hz, C6H4), 8.30–8.24 (6H, py),
8.19–8.14 (6H, py + C6H4), 8.09 (2H, d, J = 5.0 Hz, py), 7.66–7.63
(2H, m, py), 3.98 (6H, s, Me). m
(C@O) 1709s cmꢀ1. Anal. Calc. (%)
for C56H44F24N8O4P4Ruꢁ4H2O: C, 40.86; H, 3.18; N, 6.81. Found: C,
41.00; H, 2.76; N, 6.79%. MALDI-MS: m/z = 1427 ([MꢀPF6]+), 1284
([Mꢀ2PF6]+), 1140 ([Mꢀ3PF6]+), 996 ([Mꢀ4PF6]+).
(2H, m, py), 7.60–7.57 (2H, m, py). m
(C@O) 1703s cmꢀ1. Anal. Calc.
(%) for C54H40F24N8O4P4Ru: C, 41.95; H, 2.61; N, 7.25. Found: C,
42.32; H, 2.45; N, 7.24%. MALDI-MS: m/z = 1401 ([MꢀPF6]+), 1256
([Mꢀ2PF6]+), 1112 ([Mꢀ3PF6]+), 967 ([Mꢀ4PF6]+).
2.2.17. cis-[RuII(bpy)2(Me2bbpe2+)][PF6]4 (9)
Used [Me2bbpe2+]I2ꢁ0.7H2O (124 mg, 0.188 mmol). Yield: 62 mg
(23%). dH (400 MHz, CD3COCD3) 9.06–9.05 (6H, py), 8.83 (4H, d,
J = 8.1 Hz, C5H4N), 8.37 (4H, d, J = 6.8 Hz, C5H4N), 8.25–8.20 (4H,
m, C5H4N), 8.18–8.16 (4H, py), 8.13 (2H, d, J = 16.4 Hz, CH), 8.06
(2H, dd, J = 5.8, 0.8 Hz, py), 8.00 (2H, d, J = 16.7 Hz, CH), 7.81 (2H,
dd, J = 6.1, 1.8 Hz, py), 7.61–7.56 (4H, py), 4.60 (6H, s, Me). Anal.
Calc. (%) for C46H40F24N8P4Ruꢁ2H2O: C, 38.86; H, 3.12; N, 7.88.
Found: C, 39.00; H, 2.86; N, 7.80%. MALDI-MS: m/z = 1242
([MꢀPF6]+), 1097 ([Mꢀ2PF6]+), 952 ([Mꢀ3PF6]+), 807 ([Mꢀ4PF6]+).
2.3. X-ray crystallography
Crystals of [(3,5-MC2Ph)2qpy2+]Cl2ꢁ5CD3OD were grown by slow
evaporation of a CD3ODsolutionin an NMRtube, whilethose ofcom-
plex salts 5ꢁ2.75MeCN, 7ꢁ2.5MeCN and 10ꢁ2MeCN were obtained by
vapour diffusion of diethyl ether into acetonitrile solutions. Data
were collected on a Bruker APEX CCD X-ray diffractometer by using

1834
B.J. Coe et al. / Polyhedron 30 (2011) 1830–1841
Mo K
a
radiation (k = 0.71073 Å), and the data were processed by
pyridinium substituents, primarily for their interesting NLO prop-
erties [9–11,13]. The complex salts cis-[RuII(bpy)2qpy][PF6]2 (1)
[19] and cis-[RuII(bpy)2(Me2qpy2+)][PF6]4 (2) [19a,b] (Fig. 1) have
been reported previously, but were obtained in this study via
slightly modified methods. The new asymmetric complexes in salts
3–11 (Fig. 1) were prepared in part to allow comparisons of optical
and redox properties with the symmetric tris-chelates, but also in
order to access the potential photosensitizers 12 and 13.
using the Bruker SAINT [14] and SADABS [15] software packages. The
structures were solved by direct methods using SHELXS-97 [16], and
refined by full-matrix least-squares on all F0 data using SHELXL-97
2
[17]. All non-hydrogen atoms were refined anisotropically and
hydrogen atoms were included in idealised positions using the rid-
ing model, with thermal parameters of 1.2 times those of aromatic
parent carbon atoms, and 1.5 times those of methyl parent carbons.
The asymmetric unit of [(3,5-MC2Ph)2qpy2+]Cl2ꢁ5CD3OD con-
tains half the cation and one Clꢀ anion, together with one ordered
and 3 disordered CD3OD molecules, the latter at 0.5 occupancy.
The asymmetric unit of 5ꢁ2.75MeCN contains one cation and three
whole and two half PF6ꢀ anions, with several MeCN molecules, one
of which is at 0.75 occupancy. In one of the half PF6ꢀ anions, the P
atom lies on a centre of symmetry and in the other, the F atoms are
disordered over two sites each. Restraints were applied to the geom-
etry and atomic displacement parameters (adps) of the disordered
The compound 4,40:20,200:400,4000-quaterpyridyl (qpy) was syn-
thesised by combining a previously reported method [9], with
the chromatographic purification described in another report
[20], avoiding a prolonged Soxhlet extraction. Although this meth-
od is relatively convenient, a much higher yield (79%) of qpy has
been obtained by Ni0-mediated reductive coupling of 4-
(2-chloropyridin-4-yl)pyridine [20]. While the N00,N000-dimethyl-
4,40:20,200:400,4000-quaterpyridinium (Me2qpy2+) dication has been
reported as its iodide and hexafluorophosphate salts [21], the chlo-
ride salt [Me2qpy2+]Cl2 is to our knowledge a new compound.
Because the salts [Ph2qpy2+]Cl2, [(4-AcPh)2qpy2+]Cl2, [(2-Pym)2q-
py2+]Cl2, [(3,5-MC2Ph)2qpy2+]Cl2 and [(2,4-DNPh)2qpy2+]Cl2 were
treated as intermediates in previous work [9,10], no analytical data
were obtained. Such data together with modified synthetic
methods for these compounds are hence included here. The new
pro-ligand salt [(4-MCPh)2qpy2+]Cl2 was synthesised in a manner
similar to that used for its close relatives, via a Zincke-type reaction
between [(2,4-DNPh)2qpy2+]Cl2 and methyl-4-aminobenzoate.
The new complexes in 2–11 were prepared by reacting cis-
RuIICl2(bpy)2ꢁ2H2O with a little less than one equivalent of the
appropriate pro-ligand chloride salt (except for Me2bbpe2+ where
the iodide salt was used) in ethanol under reflux. Yields in the
range ca. 30–55% were obtained after purification on silica gel col-
umns eluting with 0.1 M NH4PF6 in acetonitrile. It is perhaps signif-
icant that a relatively low yield (23%) was obtained when using the
pro-ligand iodide salt to prepare the complex salt 9. The carboxyl-
ate-substituted complex salts 12 and 13 were prepared in good
yields simply via acid-catalysed hydrolysis of the methyl ester
groups in 7 and 8, respectively.
ꢀ
PF6 and some of the MeCN molecules. The asymmetric unit of
7ꢁ2.5MeCN contains one cation, four PF6ꢀ anions and 2.5 MeCN mol-
ecules. Restraints were applied to the anisotropic adps and to the
geometry of three of the PF6ꢀ ions and two of the MeCN molecules.
The crystal diffracted very weakly so the data were cut at 1.1 Å res-
olution. For 10ꢁ2MeCN, there are two cations in the asymmetric unit,
and seven whole (one of which is disordered over two sites) and two
half PF6ꢀ anions (the latter with the P atoms on 2-fold axes), as well
as a number of MeCN molecules, some at 0.5 occupancy. Restraints
were applied to the geometry of the disordered PF6ꢀ and to the par-
tially occupied MeCN molecules, as well as the anisotropic adps. The
data were cut at 1.05 Å because the crystal did not diffract beyond
this resolution. All other calculations were carried out by using the
SHELXTL package [18]. Crystallographic data and refinement details
are presented in Table 1.
3. Results and discussion
3.1. Synthesis and characterisation
The identities and purities of all the products are confirmed by
clean 1H NMR spectra, together with +electrospray or MALDI mass
spectra, CHN elemental analyses and IR spectra in cases where es-
We have studied previously a number of salts of RuII complexes
containing three bpy-based ligands bearing two electron-accepting
Table 1
Crystallographic data and refinement details for the pro-ligand salt [(3,5-MC2Ph)2qpy2+]Cl2ꢁ5CD3OD and the complex salts 5ꢁ2.75MeCN, 7ꢁ2.5MeCN and 10ꢁ2MeCN.
[(3,5-MC2Ph)2qpy2+]Cl2ꢁ5CD3OD
5ꢁ2.75MeCN
7ꢁ2.5MeCN
10ꢁ2MeCN
Formula
C
45H32Cl2D20N4O13
C53.5H44.25F24N14.75P4Ru
1574.74
C65H55.5F24N10.5O8P4Ru
1792.65
monoclinic
P21/c
12.0679(17)
13.4767(19)
44.274(6)
90
90.886(3)
90
7199.7(17)
4
1.654
100(2)
0.431
C60H50F24N10P4Ru
1592.05
monoclinic
C2/c
27.702(8)
36.615(10)
26.253(8)
90
90.356(6)
90
26628(13)
16
1.588
100(2)
0.447
Molecular weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
947.85
monoclinic
P21/c
8.6247(19)
24.445(5)
10.939(2)
90
91.712(4)
90
2305.3(9)
2
1.365
100(2)
0.209
triclinic
ꢀ
P1
13.947(2)
14.698(2)
18.064(2)
90.699(3)
106.388(3)
117.404(2)
3100.1(8)
2
a
(°)
b (°)
c
(°)
U (Å3)
Z
Dcalc (mg mꢀ3
T (K)
)
1.687
100(2)
0.481
l
(mmꢀ1
)
Crystal size (mm)
Crystal appearance
Reflections collected
Independent reflections (Rint
hmax/° (completeness)
0.30 ꢂ 0.20 ꢂ 0.10
pale yellow block
12987
4711 (0.0601)
26.43 (99.2%)
2516
0.30 ꢂ 0.20 ꢂ 0.20
red block
19351
8889 (0.0667)
23.26 (99.7%)
6547
0.40 ꢂ 0.30 ꢂ 0.05
red block
27875
5648 (0.1160)
18.85 (99.9%)
4401
0.65 ꢂ 0.30 ꢂ 0.05
red plate
57217
12038 (0.1644)
19.78 (99.9%)
8044
)
Reflections with I > 2
r(I)
Goodness-of-fit on F2
0.726
1.089
1.725
1.120
Final R1, wR2 [I > 2
r
(I)] (all data)
0.0494, 0.1073
0.1027, 0.1237
0.301, ꢀ0.269
0.0930, 0.2274
0.1251, 0.2471
1.640, ꢀ0.747
0.1634, 0.4085
0.1865, 0.4231
1.179, ꢀ1.466
0.1100, 0.2335
0.1568, 0.2570
1.030, ꢀ0.615
Peak and hole (eÅꢀ3
)

B.J. Coe et al. / Polyhedron 30 (2011) 1830–1841
1835
b
–
2+ [PF6
]
2
N
N
b
N
N
a
a
N
N
b
b
–
Ru
N
+
4+ [PF6
]
4
R
R
N
b
N
b
N
N
N
N
N
a
a
Ru
N
b
b
1
b
+
N
–
+
N
4+ [PF6
]
4
R
R
N
b
R = Me (9), Ph (10), 2,4-DNPh (11)
N
N
N
N
a
a
Ru
N
R1
b
+
–
4+ [PF6
]
4
R
N
b
+
b
N
R1
N
b
O
N
N
N
N
N
a
a
R = Me (2), Ph (3),
(5),
(4),
Ru
N
N
b
+
(4-AcPh)
O
(2-Pym)
R1
R
N
b
O2N
OMe
R1
OMe
(6),
(7),
(8)
NO2
R = H, R1 = CO2H (12); R = CO2H, R1 = H (13)
O
OMe
(2,4-DNPh)
(4-MCPh)
O
(3,5-MC2Ph)
Fig. 1. Chemical structures of the RuII complex salts investigated, including the labelling for selected protons for which the signals are assigned in the 1H NMR spectra.
ter, carboxylate or nitro functional groups are present. As is com-
monly the case for organic salts, all of the products contain residual
water that is not removed by drying under vacuum at room tem-
perature (the samples were not heated in order to avoid any pos-
sible decomposition).
3.2. 1H NMR spectroscopy studies
While the relative complexity of the 1H spectra precludes defin-
itive assignment of many of the signals due to pyridyl ring protons
(with a total of 30 in each compound), some of these signals can be
attributed unambiguously to certain environments. In particular, a
finely split doublet (J = 1.5 Hz, in all cases expect 13 for which the
splitting is not resolved) to relatively low field and integrating for
two protons must arise from the 3,30-positions on the substituted
bpy ligand (denoted a, Fig. 1). The position of this signal is logically
sensitive to the adjacent substituents, and shows a downfield shift
Fig. 2. Aromatic regions of the 1H NMR spectra of the complex salts 1 (top) and 6
of 0.2 ppm on moving from 1 to 6 (Fig. 2), reflecting a substantial
(bottom) recorded at 400 MHz in CD3COCD3 at 293 K. The arrows indicate the large
deshielding effect of the R substituent. Based on the chemical shift
downfield shifts observed for the a and b proton signals on quaternisation of the N
atoms.
of this signal, the electron-withdrawing strength of R in the qpy-
based complexes appears to be Me < 4-AcPh = 4-MCPh = 3,5-
MC2Ph < Ph < 2-Pym < 2,4-DNPh. This ordering correlates some-
identical d values in 10 and 11 shows that extending the conju-
gated systems lessens the influence of the pyridinium groups.
Any signal that shows a clear multiplet splitting and integrates
for four protons can not be due to the C5H3N units, but rather must
arise from the C5H4N groups. Although ‘‘C5H4N’’ can relate to the
protons of the unsubstituted bpy ligands or the pendent/quatern-
ised pyridyl rings, the lowest field four proton doublet (denoted
b, Fig. 1) signals are almost certainly due to the protons adjacent
to the deshielding quaternised N atoms. In 1, this signal occurs to
slightly higher field when compared with another four proton dou-
what with that inferred previously from the MLCT absorption ener-
gies for the symmetric complexes [RuII(R2qpy2+)3]8+, that show a
significant difference between R = Me and Ph, but then little fur-
ther change on moving to R = 4-AcPh or 3,5-MC2Ph [10]. While
the a proton signal is not resolved in the spectrum of 9 in
CD3COCD3, for 10 and 11 it appears to high field by ca. 0.3 ppm
when compared with 1. This observation shows that the elec-
tron-donating (thus shielding) influence of the ethenylene units
in 10 and 11 offsets considerably the deshielding effect of the pyr-
idyl groups. Also, the fact that the a proton signal occurs at almost

1836
B.J. Coe et al. / Polyhedron 30 (2011) 1830–1841
Table 2
UV–Vis absorption and electrochemical data for complex salts 1–13 in acetonitrile.
a
Salt
kmax, nm (
e
, 103 Mꢀ1 cmꢀ1
)
Emax (eV)
Assignment
E1/2 or E, V versus Ag–AgCl (
D
Ep, mV)b
[E1/2]RuIII/II
Reductions
1
463 (13.4)
358 (9.9)
2.68
3.46
4.31
5.02
2.48
2.90
3.82
4.37
4.86
2.45
2.86
3.71
4.35
4.84
d ? p⁄
d ? p⁄
1.36 (90)
ꢀ1.11 (70)
ꢀ1.43 (80)
ꢀ1.64 (80)
288 (58.5)
247 (46.2)
500 (20.9)
428 (24.1)
325 (27.5)
284 (84.6)
255 (72.6)
507 (19.8)
433 (21.6)
334 (27.0)
285 (87.9)
256 (54.2)
p
p
?
?
p⁄
p⁄
2c
d ? p⁄
1.41 (80)
1.43 (80)
ꢀ0.70 (180)d
ꢀ1.19 (80)
ꢀ1.42 (90)
ꢀ1.59 (95)
d ? p⁄
p
p
p
?
?
?
p⁄
p⁄
p⁄
3e
d ? p⁄
ꢀ0.54 (150)d
ꢀ0.98f
d ? p⁄
p
p
p
?
?
?
p⁄
p⁄
p⁄
ꢀ1.06g
ꢀ1.14f
ꢀ1.24g
ꢀ1.68g
ꢀ0.54g
4
5
507 (18.8)
436 (19.4)
337 (22.8)
285 (84.6)
256 (50.1)
512 (26.9)
439 (24.4)
341 (21.1)
285 (129.0)
260 (61.6)
2.45
2.84
3.68
4.35
4.84
2.42
2.82
3.64
4.35
4.77
d ? p⁄
d ? p⁄
1.43 (75)
1.43 (80)
ꢀ0.79g
p
p
p
?
?
?
p⁄
p⁄
p⁄
d ? p⁄
ꢀ0.26f
ꢀ0.36g
ꢀ0.80 (80)
ꢀ1.02f
ꢀ1.04g
ꢀ1.26f
ꢀ1.44g
ꢀ0.66g
ꢀ0.92g
ꢀ1.25g
d ? p⁄
p
p
p
?
?
?
p⁄
p⁄
p⁄
6
7
512 (18.9)
438 (17.6)
340 (15.8)
283 (86.7)
258 (69.0)
509 (27.5)
435 (28.5)
335 (28.3)
285 (123.0)
257 (74.6)
2.42
2.83
3.65
4.38
4.81
2.44
2.85
3.70
4.35
4.82
d ? p⁄
d ? p⁄
1.44 (80)
1.44 (70)
p
p
p
?
?
?
p⁄
p⁄
p⁄
d ? p⁄
ꢀ0.42f
ꢀ0.53g
ꢀ0.86f
ꢀ0.82g
ꢀ1.28f
ꢀ1.42f
ꢀ1.55g
ꢀ1.68f
ꢀ1.75g
ꢀ1.91g
ꢀ0.45f
ꢀ0.53g
ꢀ0.86f
ꢀ0.94g
ꢀ1.36f
ꢀ1.48g
ꢀ1.58g
ꢀ1.64f
ꢀ1.72g
ꢀ0.68g
ꢀ0.99g
ꢀ1.29f
ꢀ1.34g
ꢀ1.63g
ꢀ0.53g
ꢀ1.17g
ꢀ1.25f
ꢀ1.31g
ꢀ0.52g
ꢀ1.35g
d ? p⁄
p
p
p
?
?
?
p⁄
p⁄
p⁄
8
509 (23.0)
436 (23.8)
338 (26.1)
285 (117.0)
258 (63.8)
2.44
2.84
3.67
4.35
4.81
d ? p⁄
d ? p⁄
1.43 (70)
p
p
p
?
?
?
p⁄
p⁄
p⁄
9
497 (19.5)
439 (20.7)
342 (31.1)
288 (76.1)
2.49
2.82
3.63
4.31
d ? p⁄
d ? p⁄
1.34 (60)
p
p
?
?
p⁄
p⁄
10
11
12
502 (25.4)
445 (25.2)
324 (64.9)
289 (74.0)
509 (29.4)
450 (25.8)
321 (75.8)
288 (87.7)
511 (19.0)
438 (18.1)
335 (20.7)
286 (74.1)
256 (46.1)
2.47
2.79
3.83
4.29
2.44
2.76
3.86
4.31
2.43
2.83
3.70
4.33
4.84
d ? p⁄
d ? p⁄
1.36 (85)
1.36 (75)
1.44 (80)
p
p
?
?
p⁄
p⁄
d ? p⁄
d ? p⁄
p
p
?
?
p⁄
p⁄
d ? p⁄
ꢀ0.52g
ꢀ0.61f
ꢀ1.01g
ꢀ1.04f
ꢀ1.45f
ꢀ1.61g
ꢀ0.53g
ꢀ0.57f
ꢀ0.89g
d ? p⁄
p
p
p
?
?
?
p⁄
p⁄
p⁄
13
509 (20.9)
435 (21.7)
335 (25.1)
2.44
2.85
3.70
d ? p⁄
d ? p⁄
1.44 (90)
p
?
p⁄

B.J. Coe et al. / Polyhedron 30 (2011) 1830–1841
1837
Table 2 (continued)
a
Salt
kmax, nm (
e
, 103 Mꢀ1 cmꢀ1
)
Emax (eV)
Assignment
E1/2 or E, V versus Ag–AgCl (
D
Ep, mV)b
[E1/2]RuIII/II
Reductions
285 (91.8)
256 (52.3)
4.35
4.84
p
p
?
?
p⁄
p⁄
ꢀ1.00f
ꢀ1.04g
ꢀ1.45f
ꢀ1.62g
a
Solutions ca. 3–5 ꢂ 10ꢀ5 M.
b
Measured in solutions ca. 10ꢀ3 M in analyte and 0.1 M in [NBun4]PF6 at a 2 mm disc glassy carbon working electrode with a scan rate of 200 mV sꢀ1. Ferrocene internal
reference E1/2 = 0.44 V,
DEp = 70–90 mV.
c
Differential pulse voltammetry data, V versus Ag–AgCl (potential increment = 4 mV; amplitude = 50 mV; pulse width = 0.01 s): ꢀ0.62, ꢀ0.73, ꢀ1.17, ꢀ1.39, ꢀ1.58.
d
e
f
Two strongly overlapped waves.
Differential pulse voltammetry data, V versus Ag–AgCl (parameters as for 2): ꢀ0.49, ꢀ0.56, ꢀ1.00, ꢀ1.18, ꢀ1.61.
Epa for an irreversible reduction process.
g
Epc for an irreversible reduction process.
clearly similar to, but not the same as, that indicated by the a pro-
ton signal (see above). Other 1H NMR studies with {RuII(NH3)5}2+ or
trans-{RuIICl(pdma)2}+ [pdma = 1,2-phenylenebis(dimethylarsine)]
complexes of related monodentate 4,40-bipyridinium ligands indi-
cate the same (albeit incomplete) electron-withdrawing order
R = Me < Ph < 2,4-DNPh < 4-AcPh < 2-Pym, based on the chemical
shift of the b proton signal [22,23].
Where resolved, the 1H signals observed for the phenyl/2-
pyrimidyl rings or ethenylene groups can be assigned based on
their coupling constants and multiplicities. The J values of ca.
16.5 Hz for the ethenylene signals in 9–11 confirm the presence
of only the expected E-configurations in all cases.
3.3. Electronic spectroscopy studies
The UV–Vis absorption spectra of complex salts 1–13 have been
measured in acetonitrile and the results are presented in Table 2.
Representative spectra are shown in Figs. 3 and 4.
Fig. 3. UV–Vis absorption spectra of the complex salts 1 (blue), 2 (gold), 5 (red) and
7 (green) in acetonitrile at 293 K (Colour online).
The spectra of complex salts 2–13 feature intense intraligand
p
?
p⁄ absorptions in the UV region and also visible MLCT bands
with two distinct maxima. A simplistic view might suggest that
the high energy band corresponds with Ru ? bpy MLCT, while
the low energy band arises from Ru ? LA (LA = a pyridinium-substi-
tuted bpy derivative) MLCT. However, the previously studied com-
plexes [RuII(LA)3]8+ also show two resolved bands [10,13] and both
empirical trends and density functional theoretical calculations
indicate that these derive from MLCT to the bpy and pyridinium
units, with the latter transitions correlating with the higher energy
(HE) bands [10]. Given that the Emax value for the HE band in 2–13
changes by only 0.07 eV when R is changed, while the lower energy
(LE) band Emax varies more (by 0.14 eV), it seems likely that the lat-
ter still involves MLCT transitions to the pyridinium units. How-
ever, lowering the symmetry of the complexes complicates their
electronic structures, so the observed bands may correspond with
more than two transitions. In contrast, the spectrum of 1 shows
only one visible maximum (with a poorly defined shoulder to high
energy) which is markedly less intense than those of 2–13 (Figs. 3
and 4).
Fig. 4. UV–Vis absorption spectra of the complex salts 1 (blue), 9 (brown), 10
(orange) and 11 (purple) in acetonitrile at 293 K (Colour online).
The visible Emax data obtained for 1 and 2 (Table 2) are very sim-
ilar to those reported previously [19b], although the LE MLCT
bands do show small solvatochromic shifts when measured in
methanol [19a]. In contrast, the relative band intensities that we
have measured differ from those published; Bierig et al. claimed
that the MLCT band for 1 is more intense when compared with that
blet that is attributable, based on its generally relatively large J va-
lue and near constancy in all of the spectra, to the bpy ligands.
COSY experiments provide further confirmation of these assign-
ments. As expected, the b proton signal shows pronounced sensi-
tivity to the R group, with downfield shifts of ca. 0.8 ppm on
moving from 1 to 6 (Fig. 2), and ca. 1.5 ppm on moving from 1 to
5. Based on the d value of this signal, the electron-withdrawing
ordering for the qpy-based complexes is R = Me < Ph < 2,4-
DNPh ꢃ 4-AcPh = 4-MCPh < 3,5-MC2Ph < 2-Pym. This ordering is
for 2 [19a], while Hayes et al. reported very similar
e values for
both compounds [19b]. The Emax value of the LE MLCT band in 2–
13 is decreased by as much as ca. 0.26 eV when compared with
that of 1. Hence, it is clear that incorporating electron-accepting

1838
B.J. Coe et al. / Polyhedron 30 (2011) 1830–1841
Table 3
Low energy MLCT absorption and electrochemical data for tris-chelates [RuII(R2qpy2+)3][PF6]8 in acetonitrile.a
b
Salt
kmax, nm (
e
, 103 Mꢀ1 cmꢀ1
)
Emax (eV)
E1/2 or E, V versus Ag–AgCl (
D
Ep, mV)c
Reduction
[E1/2]RuIII/II
[RuII(Me2qpy2+)3][PF6]8
486 (37.3)
394 (26.4)
496 (37.3)
410 (26.1)
498 (49.5)
416 (33.5)
498 (53.8)
416 (35.2)
2.55
3.15
2.50
3.02
2.49
2.98
2.49
2.98
1.61 (110)
ꢀ0.69 (140)
ꢀ0.52 (90)
ꢀ0.44e
[RuII(Ph2qpy2+)3][PF6]8
1.62 (110)
1.64 (180)d
1.65f
[RuII{(4-AcPh)2qpy2+}3][PF6]8
[RuII{(3,5-MC2Ph)2qpy2+}3][PF6]8
ꢀ0.43e
a
b
c
Data taken from Ref. [10].
Solutions ca. 3–8 ꢂ 10ꢀ5 M.
Measured in solutions ca. 10ꢀ3 M in analyte and 0.1 M in [NBun4]PF6 at a 2 mm disc glassy carbon working electrode with a scan rate of 200 mV sꢀ1. Ferrocene internal
reference E1/2 = 0.44 V,
DEp = 90 mV.
.
d
Irreversible, ipa > ipc
e
f
Epc for an irreversible reduction process.
Epa for an irreversible oxidation process.
Fig. 5. (a) Cyclic voltammograms for the complex salts 1 (green), 2 (red) and 3
(blue) recorded at 200 mV sꢀ1 in acetonitrile with
glassy carbon working
electrode. The arrow indicates the direction of the initial scans. (b) Differential
pulse voltammograms for the complex salts 2 (red) and 3 (blue) recorded under the
same conditions (potential increment = 4 mV; amplitude = 50 mV; pulse
width = 0.01 s) (Colour online).
Fig. 7. Representation of the molecular structure of the complex cation in the salt
5ꢁ2.75MeCN, with the H atoms removed for clarity (30% probability ellipsoids).
a
AcPh, 3,5-MC2Ph or 4-MCPh are minimal. Similar behaviour is also
observed for the tris-chelates, [RuII(R2qpy2+)3]8+ (R = Me, Ph, 4-
AcPh or 3,5-MC2Ph) [10]. The complexes with the most strongly
electron-withdrawing substituents, 2-Pym and 2,4-DNPh, logically
exhibit the most red-shifted MLCT bands. However, the total shifts
in Emax are relatively small; on moving from 2 to 5, ꢀ0.06 eV for the
LE band and ꢀ0.08 eV for the HE band (Fig. 3). The same general
pyridinium substituents both red shifts and enhances the intensi-
ties of the MLCT absorptions.
For the qpy-based complexes, the energies of both MLCT bands
decrease slightly on moving from R = Me to Ph (2 ? 3), but the dif-
ferences between the Emax values for the complexes with R = Ph, 4-
Fig. 6. Representation of the molecular structure of the cation in the salt [(3,5-MC2Ph)2qpy2+]Cl2ꢁ5CD3OD, with the H atoms removed for clarity (50% probability ellipsoids).

B.J. Coe et al. / Polyhedron 30 (2011) 1830–1841
1839
Table 4
Selected interatomic distances (Å) and angles (°) for the complex salts 5ꢁ2.75MeCN,
7ꢁ2.5MeCN and 10ꢁ2MeCN.
5ꢁ2.75MeCN
7ꢁ2.5MeCN
10ꢁ2MeCN
2.046(12)
2.034(12)
2.043(12)
2.061(12)
2.056(12)
2.077(12)
79.5(5)
Ru–N(LA)
2.044(7)
2.047(7)
2.064(7)
2.067(7)
2.051(8)
2.077(7)
78.9(3)
2.035(17)
2.053(17)
2.038(17)
2.036(18)
2.065(18)
2.078(18)
78.7(7)
Ru–N(LA)
Ru–N(bpy, trans-LA)
Ru–N(bpy, trans-LA)
Ru–N(bpy, trans-bpy)
Ru–N(bpy, trans-bpy)
N(LA)–Ru–N(LA)
N(bpy)–Ru–N(bpy)
N(bpy)–Ru–N(bpy)
Dihedral angles 1a
Dihedral angles 2b
79.0(3)
78.4(3)
21.0, 21.0
5.9, 20.0
79.3(7)
79.6(8)
26.3, 39.0
64.9, 45.9
79.2(5)
79.6(5)
6.1, 4.0/17.5, 18.6c
54.4, 45.9/46.5, 35.8c
LA = (2-Pym)2qpy2+ (in 5), (3,5-MC2Ph)2qpy2+ (in 7) or Ph2bbpe2+ (in 10).
a
Between the planes of the two pyridyl rings within the two halves of the LA
ligands.
b
Between the planes of the quaternised pyridyl and N-aryl substituent within
the two halves of the LA ligands.
c
For the two independent cations in the asymmetric unit.
ence of ethenylene units when this orbital is located primarily on
the bpy groups (for the LE transition).
The new UV–Vis data also merit quantitative comparisons with
those obtained previously for the complexes [RuII(R2qpy2+)3]8+ (Ta-
ble 3). When compared with these tris-chelates, the MLCT bands of
the cis-[RuII(bpy)2(R2qpy2+)]4+ complexes are always red shifted
but less intense. On moving from a mono-R2qpy2+ complex to its
tris-R2qpy2+ counterpart, the Emax value of the LE MLCT band in-
creases by 0.04–0.07 eV, while that of the HE MLCT band increases
by 0.13–0.25 eV. These energy changes become smaller on moving
along the series R = Me > Ph > 4-AcPh ꢃ 3,5MC2Ph. The observation
of larger relative changes for the HE band is consistent with the
assignment of this absorption as being more strongly associated
with the presence of pyridinium substituents (see above). Given
that the ligand structure remains constant, the blue shifts in the
MLCT bands on increasing the number of pyridinium groups imply
stabilisation of the Ru-based HOMO (see below).
Fig. 8. Representation of the molecular structure of the complex cation in the salt
7ꢁ2.5MeCN, with the H atoms removed for clarity (30% probability ellipsoids).
3.4. Electrochemical studies
The complex salts 1–13 were studied by cyclic voltammetry in
acetonitrile and the results are presented in Table 2. When using a
glassy carbon working electrode, all of the complexes show quasi-
reversible or reversible RuIII/II oxidation waves, together with two
or more ligand-based reduction processes that range in character
from reversible to irreversible. E1/2 values are reported for the lat-
ter waves only in cases where the ipa and ipc values are equivalent,
while Epa and Epc values are quoted otherwise.
Fig. 9. Representation of the molecular structure of the complex cation in the salt
10ꢁ2MeCN, with the H atoms removed for clarity (30% probability ellipsoids).
The [E1/2]RuIII/II value increases by 50–80 mV on moving from 1 to
its quaternisedderivatives (Table 2, Fig. 5), indicating stabilisation of
the Ru-based HOMO due to the electron-withdrawing influence of
the pyridinium groups. Clearly, significant electronic coupling oc-
curs between the RuII centre and pyridinium moieties. The differ-
ences in [E1/2]RuIII/II between 2 and the N-aryl derivatives are small
but consistent at ca. 20–30 mV. For the series 9–11, the mildly elec-
tron-donating influence of the ethenylene units offsets the with-
drawing effect of the quaternised groups, giving [E1/2]RuIII/II values
indistinguishable from that of 1.
The potentials for ligand-based reduction increase on moving
from 1 to its quaternised derivatives (Fig. 5), indicating stabilisa-
tion of the LUMOs. These energy changes are more pronounced
than those for the HOMO, consistent with the observed red-shifts
in the MLCT bands (see above). Moving along the series 2 to 5,
the potential of the first reduction process increases by a total of
ca. 400 mV, and the overall trend observed with respect to the
trend is also observed for the complexes [RuII(NH3)4(R2qpy2+)]4+
(R = Me, Ph, 4-AcPh or 2-Pym) [9], although these ammine chro-
mophores show only one visible maximum that shifts to a much
greater extent; ꢀ0.25 eV on replacing Me with 2-Pym.
For the new bbpe-based series, the energies of both MLCT bands
decrease slightly on moving from 9 to 11 (Fig. 4), with differences
of 0.05 and 0.06 eV between the extreme Emax values. The HE MLCT
band red shifts by 0.07–0.08 eV on moving from a qpy-based com-
plex to its bbpe analogue, but the LE MLCT band shows very slight
accompanying blue shifts of 0.01–0.02 eV. These observations are
consistent with stabilisation of the acceptor MO by increased delo-
calisation when this orbital is located primarily on the outer parts
of the quaternised ligands (for the HE transition), but destabilisa-
tion of the acceptor MO due to the mild electron-donating influ-

1840
B.J. Coe et al. / Polyhedron 30 (2011) 1830–1841
increasing electron-withdrawing strength of the pyridinium moie-
ties is reminiscent of that found in other RuII complexes of mono-
dentate 4,40-bipyridinium ligands [9,22,23]. The first reduction
process for complex salts 2 and 3 is actually two strongly over-
lapped waves which can be resolved by using differential pulse
voltammetry (Fig. 5). This behaviour shows that the initial reduc-
tion of one of the pyridinium groups affects the potential for the
other one, due to significant electronic coupling within the coordi-
nated qpy unit. Similar effects are observed for the related species
[RuII(NH3)4(R2qpy2+)][PF6]4 (R = Me or Ph) [9], although the poten-
tials for the latter are cathodically shifted by 60–120 mV when
compared with those of 2 and 3. These differences are due to the
higher electron-donating ability of the ammine ligands with re-
spect to bpy that is transmitted to the R2qpy2+ ligands via the RuII
centre. The presence of the ethenylene groups causes the reductive
chemistry of 9–11 to be completely irreversible because the radical
anions generated are prone to undergo rapid chemical reactions.
The RuIII/II waves for 2–4 and 7 are found at lower potentials by
ca. 200 mV when compared with the analogous [RuII(R2qpy2+)3]8+
complexes (Tables 2 and 3). This difference is attributable to the
presence of only two as opposed to six pyridinium substituents
that renders the Ru centres more electron rich in the new com-
plexes. Hence, the blue shifts in the MLCT bands on increasing
the number of pyridinium groups are indeed due to stabilisation
of the Ru-based HOMO (see above). In contrast, the first ligand-
based reductions occur at generally similar potentials in 2–4 and
7 when compared with their [RuII(R2qpy2+)3]8+ analogues, indicat-
ing that electronic coupling between the three bpy-based ligands is
weak.
packing structures, they are not expected to show significant bulk
second-order NLO effects.
4. Conclusion
A large series of new complexes of the form cis-[RuII(bpy)2
(LA)]4+ (LA = a pyridinium-substituted bpy derivative) has been pre-
pared and fully characterised. These asymmetric species are inter-
mediates between the archetypal MLCT chromophore RuTB and
recently reported extended tris-chelates [RuII(LA)3]8+ that show
marked NLO properties. The UV–Vis spectra of the new complex
salts feature intense intraligand
p ?
p⁄ absorptions and also MLCT
bands with two distinct visible maxima. Small shifts in these bands
correlate with the relative electron-withdrawing strength
of LA. Cyclic voltammograms show quasi-reversible or reversible
RuIII/II oxidation waves, together with two or more ligand-based
reduction processes that range in character from reversible to irre-
versible. The variations in the redox potentials correlate with
changes in the structure of LA, and also with the MLCT energies.
Differential pulse voltammetry allows the first reduction process
for complex salts 2 and 3 to be resolved into two peaks. Single-
crystal X-ray structures have been solved for a pro-ligand salt
and for three of the new complex salts, affording rare examples
of crystallographically-characterised RuII(qpy) motifs. The carbox-
ylate-functionalised compounds 12 and 13 have been tested as
photosensitizers on TiO2-coated electrodes, but show only negligi-
ble efficiencies, so further details will not be discussed here. How-
ever, these observations are consistent with previous reports in
that RuTB derivatives do not make especially good sensitizers
[26]; this field is dominated by RuII bis-bpy complexes with thiocy-
anate coligands [6]. In addition to containing RuTB cores, 12 and 13
have relatively long bridges between the RuII centre and carboxyl-
ate groups. This factor together with interannular twisting within
these bridges can be expected to hinder electron injection into a
semiconductor surface.
3.5. Crystallographic studies
Single-crystal X-ray structures have been obtained for the com-
plex salts 5ꢁ2.75MeCN, 7ꢁ2.5MeCN and 10ꢁ2MeCN, and also for the
pro-ligand salt [(3,5-MC2Ph)2qpy2+]Cl2ꢁ5CD3OD. Representations of
the molecular structures are shown in Figs. 6–9, and selected inter-
atomic distances and angles for the complex salts are presented in
Table 4.
Acknowledgement
The structure of [(3,5-MC2Ph)2qpy2+]Cl2ꢁ5CD3OD resembles that
we have determined previously for the related compound
[Ph2qpy2+][PF6]2ꢁMe2CO [9], with a planar, transoid bpy unit with
a crystallographic centre of symmetry in the middle of the C–C
bond between the pyridyl rings. As for Ph2qpy2+, the rest of the
(3,5-MC2Ph)2qpy2+ molecule is strongly twisted, with dihedral an-
gles of 32.9° within the 4,4-bipyridyl fragments and 41.4° between
the pyridyl and attached phenyl rings. All other geometric param-
eters for these two qpy-based dications are very similar.
We thank the EPSRC for support in the form of PhD student-
ships (ECH and YTT), and Dr Hongxia Wang (Bath University) for
carrying out TiO2 photosensitization studies with 12 and 13.
Appendix A. Supplementary data
CCDC 810529, 810530, 810531 and 810532 contains the sup-
plementary crystallographic data for ([(3,5-MC2Ph)2qpy2+]Cl2ꢁ5C-
D3OD), (5ꢁ2.75MeCN), (7ꢁ2.5MeCN) and (10ꢁ2MeCN). These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/con-
ts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Although the uncertainties on the data for 5ꢁ2.75MeCN,
7ꢁ2.5MeCN and 10ꢁ2MeCN are quite large, the average Ru–N dis-
tance to the LA ligands (ca. 2.04 Å) does seem to be a little smaller
than the Ru–N(bpy) distances (average ca. 2.06 Å); if truly signifi-
cant then this observation is consistent with a slight increase in
p
-back-bonding to the more strongly electron-withdrawing LA li-
References
gands. These ligands adopt fairly twisted conformations, with the
dihedral angles between the pyridyl rings being generally smaller
than those between the pyridyl and attached aryl rings, except
for the (2-Pym)2qpy2+ in 5ꢁ2.75MeCN (Table 4). Other structures
of N-(2-Pym)pyridyl derivatives have also revealed relatively small
twists within these moieties [23,24]. To our knowledge, the only
other reported structure containing a RuII(qpy) motif is a metallo-
macrocycle with two cis-[RuII(bpy)2qpy]2+ units and two fac-{Re-
ICl(CO)3} moieties [25]. While the level of precision of that
structure is similar to those for our new ones, average relative
shortenings of the Ru–N(qpy) with respect to the Ru–N(bpy) dis-
tances of ca. 0.02–0.03 Å are again observed. Incidentally, because
all three of the new complex salts adopt centrosymmetric crystal
[1] (a) M.A. Bennett, M.I. Bruce, T.W. Matheson, in: G. Wilkinson, F.G.A. Stone,
E.W. Abel (Eds.), Comprehensive Organometallic Chemistry, vol. 4, Pergamon
Press, Oxford, 1982, pp. 651–965;
(b) M. Schröder, T.A. Stephenson, in: G. Wilkinson, R.D. Gillard, J.A.
McCleverty (Eds.), Comprehensive Coordination Chemistry, vol. 4, Pergamon
Press, Oxford, 1987, pp. 277–518;
(c) M.A. Bennett, M.I. Bruce, M.P. Cifuentes, A.J. Deeming, R.J. Haines, A.F. Hill,
M.G. Humphrey, K. Khan, R.K. Pomeroy, E. Sappa, A.K. Smith, E. Wenger, in:
E.W. Abel, F.G.A. Stone, G. Wilkinson (Eds.), Comprehensive Organometallic
Chemistry II, vol. 7, Pergamon Press, Oxford, 1995, pp. 291–960;
(d) C.-M. Che, C.E. Housecroft, T.-C. Lau, in: J.A. McCleverty, T.J. Meyer (Eds.),
Comprehensive Coordination Chemistry II, vol. 5, Pergamon Press, Oxford,
2004, pp. 555–847;
(e) I.R. Butler, V. Cadierno, M.P. Cifuentes, P. Crochet, P.J. Dyson, J. Gimeno,
M.G. Humphrey, A.L. Johnson, B.K.L. Leong, J.S. McIndoe, R.K. Pomeroy, P.R.

B.J. Coe et al. / Polyhedron 30 (2011) 1830–1841
1841
Raithby, E. Sappa, H. Suzuki, T. Takao, D. Thomas, M.K. Whittlesey, J.D. Wilton-
Ely, W.-T. Wong, in: R.H. Crabtree, D.M.P. Mingos (Eds.), Comprehensive
Organometallic Chemistry III, vol. 6, Pergamon Press, Oxford, 2007, pp. 353–
1116.
[8] B.J. Coe, in: M.G. Papadopoulos, J. Leszczynski, A.J. Sadlej (Eds.), Nonlinear
Optical Properties of Matter: From Molecules to Condensed Phases, Springer,
Dordrecht, 2006, pp. 571–608.
[9] B.J. Coe, J.A. Harris, L.A. Jones, B.S. Brunschwig, K. Song, K. Clays, J. Garín, J.
Orduna, S.J. Coles, M.B. Hursthouse, J. Am. Chem. Soc. 127 (2005) 4845.
[10] B.J. Coe, J.A. Harris, B.S. Brunschwig, I. Asselberghs, K. Clays, J. Garín, J. Orduna,
J. Am. Chem. Soc. 127 (2005) 13399.
[11] B.J. Coe, M. Samoc, A. Samoc, L.-Y. Zhu, Y.-P. Yi, Z.-G. Shuai, J. Phys. Chem. A 111
(2007) 472.
[12] B.P. Sullivan, D.J. Salmon, T.J. Meyer, Inorg. Chem. 17 (1978) 3334.
[13] B.J. Coe, J. Fielden, S.P. Foxon, B.S. Brunschwig, I. Asselberghs, K. Clays, A.
Samoc, M. Samoc, J. Am. Chem. Soc. 132 (2010) 3496.
[14] SAINT (Version 6.45), Bruker AXS Inc., Madison, Wisconsin, USA, 2003.
[15] SADABS (Version 2.10), Bruker AXS Inc., Madison, Wisconsin, USA, 2003.
[16] G.M. Sheldrick, Acta Crystallogr., Sect. A 46 (1990) 467.
[17] G.M. Sheldrick, SHELXS 97, Programs for Crystal Structure Analysis (Release 97–
2), University of Göttingen, Göttingen, Germany, 1997.
[2] (a) Selected recent reviews: C. Samojłowicz, M. Bieniek, K. Grela, Chem. Rev.
109 (2009) 3708;
(b) J.J. Concepcion, J.W. Jurss, M.K. Brennaman, P.G. Hoertz, A.O.T. Patrocinio,
N.Y. Murakami Iha, J.L. Templeton, T.J. Meyer, Acc. Chem. Res. 42 (2009) 1954;
(c) S.P. Nolan, H. Clavier, Chem. Soc. Rev. 39 (2010) 3305;
(d) W.P. Griffith, Ruthenium Oxidation Complexes: Their Uses as Homogenous
Organic Catalysts (Catalysis by Metal Complexes), Springer, Dordrecht, 2010.
[3] (a) Selected reviews: M.J. Clarke, Coord. Chem. Rev. 236 (2003) 209;
(b) I. Kostova, Curr. Med. Chem. 13 (2006) 1085;
(c) W.H. Ang, P.J. Dyson, Eur. J. Inorg. Chem. (2006) 4003;
(d) P.C.A. Bruijnincx, P.J. Sadler, Adv. Inorg. Chem. 61 (2009) 1.
[4] (a) Selected reviews: A. Juris, V. Balzani, F. Barigelletti, S. Campagna, P. Belser,
A. von Zelewsky, Coord. Chem. Rev. 84 (1988) 85;
(b) V. Balzani, A. Juris, Coord. Chem. Rev. 211 (2001) 97;
(c) J.G. Vos, J.M. Kelly, Dalton Trans. (2006) 4869;
(d) S. Campagna, F. Puntoriero, F. Nastasi, G. Bergamini, V. Balzani, Top. Curr.
Chem. 280 (2007) 117;
(e) L. Herman, S. Ghosh, E. Defrancq, A. Kirsch-De Mesmaeker, J. Phys. Org.
Chem. 21 (2008) 670;
[18] SHELXTL (Version 6.10), Bruker AXS Inc., Madison, Wisconsin, USA, 2000.
[19] (a) See for examples: K. Bierig, R.J. Morgan, S. Tysoe, H.D. Gafney, T.C. Strekas,
A.D. Baker, Inorg. Chem. 30 (1991) 4898;
(b) M.A. Hayes, C. Meckel, E. Schatz, M.D. Ward, J. Chem. Soc., Dalton Trans.
(1992) 703;
(c) R.J. Forster, T.E. Keyes, J. Phys. Chem. B 102 (1998) 10004.
[20] A. Shi, M.R. Pokhrel, S.H. Bossmann, Synthesis 4 (2007) 505.
[21] R.J. Morgan, A.D. Baker, J. Org. Chem. 55 (1990) 1986.
[22] (a) B.J. Coe, J.A. Harris, L.J. Harrington, J.C. Jeffery, L.H. Rees, S. Houbrechts, A.
Persoons, Inorg. Chem. 37 (1998) 3391;
(b) B.J. Coe, J.A. Harris, I. Asselberghs, A. Persoons, J.C. Jeffery, L.H. Rees, T.
Gelbrich, M.B. Hursthouse, J. Chem. Soc., Dalton Trans. (1999) 3617.
[23] B.J. Coe, T. Beyer, J.C. Jeffery, S.J. Coles, T. Gelbrich, M.B. Hursthouse, M.E. Light,
J. Chem. Soc., Dalton Trans. (2000) 797.
(f) S. Bonnet, J.-P. Collin, Chem. Soc. Rev. 37 (2008) 1207.
[5] (a) Selected examples: M. Buda, G. Kalyuzhny, A.J. Bard, J. Am. Chem. Soc. 124
(2002) 6090;
(b) S. Welter, K. Brunner, J.W. Hofstraat, L. De Cola, Nature 421 (2003) 54;
(c) Y.-L. Tung, L.-S. Chen, Y. Chi, P.-T. Chou, Y.-M. Cheng, E.Y. Li, G.-H. Lee, C.-F.
Shu, F.-I. Wu, A.J. Carty, Adv. Funct. Mater. 16 (2006) 1615;
(d) J.D. Slinker, J. Rivnay, J.S. Moskowitz, J.B. Parker, S. Bernhard, H.D. Abruña,
G.G. Malliaras, J. Mater. Chem. 17 (2007) 2976.
[6] (a) M.K. Nazeeruddin, M. Grätzel, in: J.A. McCleverty, T.J. Meyer (Eds.),
Comprehensive Coordination Chemistry II, vol. 9, Pergamon Press, Oxford,
UK, 2004, pp. 719–758;
[24] (a) B.J. Coe, J.A. Harris, I. Asselberghs, K. Wostyn, K. Clays, A. Persoons, B.S.
Brunschwig, S.J. Coles, T. Gelbrich, M.E. Light, M.B. Hursthouse, K. Nakatani,
Adv. Funct. Mater. 13 (2003) 347;
(b) N. Robertson, Angew. Chem., Int. Ed. 45 (2006) 2338;
(c) J.R. Durrant, S.A. Haque, E. Palomares, Chem. Commun. (2006) 3279;
(d) S. Ardo, G.J. Meyer, Chem. Soc. Rev. 38 (2009) 115;
(e) A. Hagfeldt, G. Boschloo, L.-C. Sun, L. Kloo, H. Pettersson, Chem. Rev. 110
(2010) 6595.
(b) B.J. Coe, S.P. Foxon, E.C. Harper, J.A. Harris, M. Helliwell, J. Raftery, I.
Asselberghs, K. Clays, E. Franz, B.S. Brunschwig, A.G. Fitch, Dyes Pigments 81
(2009) 171;
(c) B.J. Coe, R.J. Docherty, S.P. Foxon, E.C. Harper, M. Helliwell, J. Raftery, K.
Clays, E. Franz, B.S. Brunschwig, Organometallics 28 (2009) 6880.
[25] P. de Wolf, P. Waywell, M. Hanson, S.L. Heath, A.J.H.M. Meijer, S.J. Teat, J.A.
Thomas, Chem. Eur. J. 12 (2006) 2188.
[26] (a) K. Kalyanasundaram, Md.K. Nazeeruddin, M. Grätzel, G. Viscardi, P.
Savarino, E. Barni, Inorg. Chim. Acta 198-200 (1992) 831;
[7] (a) Selected examples: F.H. Burstall, J. Chem. Soc. (1936) 173;
(b) D.P. Rillema, D.S. Jones, H.A. Levy, J. Chem. Soc., Chem. Commun. (1979)
849;
(c) A. Juris, V. Balzani, P. Belser, A. von Zelewsky, Helv. Chim. Acta 64 (1981)
2175.
(b) V. Aranyos, J. Hjelm, A. Hagfeldt, H. Grennberg, Dalton Trans. (2003) 1280.