Phosphonate-functionalized heteroleptic ruthenium(II) bis(2,2′: 6′,2″-terpyridine) complexes

Article abstract of DOI:10.1139/cjc-2014-0065

The heteroleptic complexes [Ru(1)(4)][PF₆]₂, [Ru(2)(4)][PF₆]₂, [Ru(Phtpy)(4)][PF₆] ₂, and [Ru(pytpy)(4)][PF₆]₂ (Phtpy = 4′-phenyl-2,2′:6′,2″-terpyridine, pytpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine, 1 and 2 = 4-methyl ester substituted derivatives of Phtpy and pytpy, 4 = ethyl 2,2′:6′,2″-terpyridine-4′-phosphonate) have been prepared. The single crystal structure of ligand 1 (1 = methyl 4-carboxy-4′-phenyl-2,2′:6′,2″-terpyridine) is reported. The introduction of the 4-methyl ester group causes a small red shift in the MLCT band of the ruthenium(II) complexes and a small shift to a more positive potential for the Ru²⁺/Ru³⁺ couple. The new complexes should serve as a useful starting point for development of ruthenium(II) dyes suited for sensitization of p-type semiconductors.

Full text of DOI:10.1139/cjc-2014-0065

724
ARTICLE
Phosphonate-functionalized heteroleptic ruthenium(II)
bis(2,2=:6=,2==-terpyridine) complexes
Edwin C. Constable, Catherine E. Housecroft, Markéta Šmídková, and Jennifer A. Zampese
Abstract: The heteroleptic complexes [Ru(1)(4)][PF6]2, [Ru(2)(4)][PF6]2, [Ru(Phtpy)(4)][PF6]2, and [Ru(pytpy)(4)][PF6]2 (Phtpy = 4=-phenyl-
2,2=:6=,2== -terpyridine, pytpy = 4=-(4-pyridyl)-2,2=:6=,2== -terpyridine, 1 and 2 = 4-methyl ester substituted derivatives of Phtpy and
pytpy, 4 = ethyl 2,2=:6=,2== -terpyridine-4=-phosphonate) have been prepared. The single crystal structure of ligand 1 (1 = methyl
4-carboxy-4=-phenyl-2,2=:6=,2== -terpyridine) is reported. The introduction of the 4-methyl ester group causes a small red shift in
the MLCT band of the ruthenium(II) complexes and a small shift to a more positive potential for the Ru2+/Ru3+ couple. The new
complexes should serve as a useful starting point for development of ruthenium(II) dyes suited for sensitization of p-type
semiconductors.
Key words: ruthenium, phosphonate functionalization, crystal structure, 2,2=:6=,2== -terpyridine, absorption spectroscopy, electro-
chemistry.
Résumé : Les complexes hétéroleptiques [Ru(1)(4)][PF6]2, [Ru(2)(4)][PF6]2, [Ru(Phtpy)(4)][PF6]2 et [Ru(pytpy)(4)][PF6]2 (Phtpy = 4=-
phényl-2,2=:6=,2== -terpyridine, pytpy = 4=-(4-pyridyl)-2,2=:6=,2== -terpyridine, 1 et 2 = dérivés de la Phtpy et de la pytpy substitués par
le 4-méthylester, 4 = éthyl 2,2=:6=,2== -terpyridine-4=-phosphonate) ont été préparés. La structure monocristalline du ligand 1 (1 =
méthyl 4-carboxy-4=-phényl-2,2=:6=,2== -terpyridine) est décrite dans le présent article. L’introduction du groupement 4-méthylester
entraîne un décalage vers le rouge du spectre de transfert de charge du ligand au métal des complexes de ruthenium(II) et un
léger décalage vers des potentiels plus positifs en ce qui concerne le couple Ru2+/Ru3+. Les nouveaux complexes devraient servir
de points de départ au développement de colorants a` base de ruthenium(II) conçus pour la sensibilisation des semicondicteurs
de type p. [Traduit par la Rédaction]
Mots-clés : ruthenium, fonctionnalisation par un phosphonate, structure crystalline, 2,2=:6=,2== -terpyridine, spectroscopie
d’absorption, électrochimie.
dyes suited for interaction with either the photoanode (n-type
semiconductor) or the photocathode (p-type) in a so-called tandem
Introduction
The {Ru(tpy)2} chromophore (tpy = 2,2=:6=,2== -terpyridine) is one
of the most extensively studied domains1 within metal oligopyr-
idine coordination chemistry. Tuning the photophysical and
electrochemical properties of {Ru(tpy)2}-containing complexes
is readily achieved through functionalization of the ligand. In
particular, the Kröhnke methodology2 is a facile means of intro-
ducing a wide variety of substituents into the 4=-position of tpy.
Although at room temperature in solution, [Ru(tpy)2]2+ is essen-
tially nonemissive,3 judicious choice of electron-donating or ac-
cepting substituents can lead to significant enhancement of
emission properties.4
Among the many areas in which ruthenium(II) complexes con-
taining tpy-derived ligands have found a practical niche is that of
the Grätzel solar cell.5 Our own interests in the development of
sensitizers for the photoanode in dye-sensitized solar cells have
moved in the direction of earth-abundant metals, in particular
copper.6 Although photon-to-power conversion efficiencies reaching
3.77%7 have been achieved with a copper(I) sensitizer anchored to
the n-type semiconductor (TiO2) comprising the photoanode, this
is significantly lower than those attained by state-of-the-art ruthe-
nium(II) dyes (>10%).8 One strategy for improving performance is
to harvest photons at both electrodes, but this requires different
cell.9 In a tandem dye-sensitized solar cell, the photocathode func-
tions in an inverse mode with respect to the photoanode, with
excitation of the dye being followed by rapid hole injection into
the p-type semiconductor (e.g., NiO). Organic donor–acceptor mol-
ecules are popular choices for photocathode sensitizers.10 Excita-
tion of the sensitizer leaves a hole in the original HOMO of the dye
into which an electron is transferred from the valence band of the
p-type semiconductor. Thus, the HOMO/LUMO requirements of a
p-type sensitizer are the reverse of those of an n-type dye. It has
been demonstrated that [Ru(bpy)2(N^N)]2+ (bpy = 2,2=-bipyridine,
N^N = bipyridine-based anchoring ligand) complexes sensitize NiO
photocathodes and both CO2H and PO(OH)2 anchors adsorb onto
NiO.11 Ruthenium(II) complexes containing cyclometalated ligands
and related to the archetypal [Ru(bpy)2(ppy)]+12,13 (Hppy = 2-
phenylpyridine) are also promising candidates for NiO sensitiza-
tion.14,15
Low-level MO calculations indicate that the HOMO of [Ru(tpy)(4=-
(HO)2OPtpy)]2+ type complexes (4=-(HO)2OPtpy = 2,2=:6=,2== -terpyridine-
4=-phosphonic acid) may be localized on the phosphonic acid
anchoring unit. We have therefore undertaken a preliminary in-
vestigation of several complexes of this type with the aim of pro-
viding a starting point for the development of dyes for p-type
Received 4 February 2014. Accepted 11 March 2014.
E.C. Constable, C.E. Housecroft, M. Šmídková, and J.A. Zampese. Department of Chemistry, University of Basel, Spitalstrasse 51, CH-4056 Basel,
Switzerland.
Corresponding author: Catherine E. Housecroft (e-mail: catherine.housecroft@unibas.ch).
This article is part of a Special Issue dedicated to Professor Barry Lever in recognition of his contributions to inorganic chemistry across Canada and beyond.
This paper is dedicated to our colleague Barry Lever whose contributions to inorganic chemistry have extended over a long and distinguished career.
Can. J. Chem. 92: 724–730 (2014) dx.doi.org/10.1139/cjc-2014-0065
Published at www.nrcresearchpress.com/cjc on 19 March 2014.

Constable et al.
725
Scheme 1. Structures of ligands 1–4 and of Phtpy and pytpy, with
atom numbering used for NMR spectroscopic assignments; when
R = H, ring A = ring D.
semiconductors. The ancillary ligands 1 and 2 (Scheme 1) contain
an ester functionality that provides a site for variable functional-
ization, for example, through transesterification.
Experimental
General
1H and 13C NMR spectra were recorded at 295 K on Bruker
Avance III-400 or III-500 NMR spectrometers (chemical shifts
with respect to residual solvent peaks and ␦(TMS) = 0 ppm).
Solution electronic absorption and emission spectra were mea-
sured, respectively, using an Agilent 8453 spectrophotometer and
Shimadzu 5301PC spectrofluorophotometer. Solution quantum
yields were measured using a Hamamatsu absolute PL quantum
yield spectrometer C11347 Quantaurus_QY. A Shimadzu 8400S
spectrometer was used to record FT-IR spectra (all solid samples
using a Golden Gate accessory). Electrospray ionization (ESI) mass
spectra and high-resolution ESI mass spectra were recorded on
Bruker esquire 3000plus and Bruker maXis 4G mass spectrometers.
Electrochemical measurements were carried out using cyclic
voltammetry and were recorded using a CH Instruments 900B
potentiostat with glassy carbon working and platinum auxiliary
electrodes; a silver wire was used as a pseudo-reference electrode.
The solvent was HPLC-grade MeCN and 0.05 mol L−1 [nBu4N][PF6]
was used as supporting electrolyte. All solutions were degassed
with argon, and Cp2Fe was used as an internal reference. A Biotage
Initiator 8 reactor was used for reactions under microwave condi-
tions. Fluka silica 60 was used for column chromatography.
The compounds (E)-1-(pyridin-2-yl)-3-(pyridin-4-yl)prop-2-en-1-one,16
(E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one,17 1-(2-(4-(methoxycarbonyl)
pyridin-2-yl)-2-oxoethyl)pyridine-1-ium iodide,16 Phtpy,17 pytpy,18 and
4=-F3CSO3-2,2=:6=,2== -terpyridine19 were prepared according to pub-
lished methods (Phtpy = 4=-phenyl-2,2=:6=,2== -terpyridine, pytpy =
4=-(4-pyridyl)-2,2=:6=,2== -terpyridine). RuCl3·3H2O was purchased from
OXKEM.
4.38 mmol) and 1-(2-(4-(methoxycarbonyl)pyridin-2-yl)-2-oxoethyl)
pyridine-1-ium iodide (2.01 g, 5.25 mmol) were added and the
brown suspension was heated at reflux for 7 h; the solids slowly
dissolved. The white precipitate that formed was collected on a
glass frit, washed with cold MeOH and Et2O, and dried in air.
Compound 2 was isolated as a white powder (1.43 g, 3.88 mmol,
89%); mp 216–217 °C. 1H NMR (500 MHz, CDCl3) ␦ (ppm): 9.15 (dd, J =
1.6, 0.9 Hz, 1H, HD3), 8.86 (dd, J = 5.0, 0.9 Hz, 1H, HD6), 8.78 (d, J =
1.7 Hz, 1H, HB3), 8.76 (m, 3H, HC2+B5), 8.72 (m, 2H, HA6+A3), 7.92 (m,
2H, HA4+D5), 7.80 (dd, J = 4.5, 1.7 Hz, 2H, HC3), 7.39 (ddd, J = 7.5, 4.8,
1.3 Hz, 1H, HA5), 4.04 (s, 3H, HOMe). 13C{1H} NMR (126 MHz, CDCl3) ␦
(ppm): 165.9 (CC=O), 156.9 (CD2), 156.7 (CB2), 155.6 (CB6), 155.5 (CA2),
150.6 (CC2), 150.0 (CD6), 149.3 (CA6), 147.6 (CB4), 145.9 (CC4), 138.5
(CD4), 137.2 (CA4), 124.3 (CA5), 123.2 (CD5), 121.7 (CC3), 121.6 (CA3),
120.7 (CD3), 119.1 (CB3), 118.9 (CB5), 53.0 (COMe). ESI-MS (MeOH/
CHCl3): m/z 391.1 [M+Na]+ (base peak, calcd. 391.1), 369.2 [M+H]+
(calcd. 369.1). IR (solid, ␯ (cm−1)): 3020 (w), 2961 (w), 1731 (s), 1583 (m),
1559 (m), 1538 (m), 1533 (m), 1475 (m), 1436 (m), 1378 (m), 1309 (w),
1292 (w), 1270 (m), 1263 (w), 1218 (m), 1211 (m), 1130 (w), 973 (w),
895 (w), 821 (m), 795 (s), 770 (s), 736 (w), 682 (m), 669 (m), 660 (m),
618 (m), 533 (m). UV/VIS ␭ (nm) (␧ (dm3 mol−1 cm−1)) (CH3CN, 4.22 ×
10−5 mol dm−3): 242 (33000), 281 (16000), 316 sh (10000). Found:
C 70.96, H 4.44, N 15.19; C22H16N4O2·0.25H2O requires C 70.86,
H 4.46, N 15.02%.
Compound 1
Ammonium acetate (9.60 g, 124.68 mmol) was dissolved in
MeOH (110 mL). (E)-3-Phenyl-1-(pyridin-2-yl)prop-2-en-1-one (1.00 g,
4.76 mmol) and 1-(2-(4-(methoxycarbonyl)pyridin-2-yl)-2-oxoethyl)
pyridine-1-ium iodide (2.21 g, 5.71 mmol) were added and the
brown solution was heated at reflux for 16 h, during which time a
brown precipitate formed. The reaction mixture was then cooled
to room temperature and left to stand overnight in a freezer. The
brown precipitate was collected on a glass frit, washed with cold
MeOH, and dried in air. Compound 1 was isolated as a pale brown
powder (0.56 g, 1.53 mmol, 33%); mp 197–198 °C. 1H NMR (500 MHz,
CDCl3) ␦ (ppm): 9.16 (dd, J = 1.7, 0.9 Hz, 1H, HD3), 8.86 (dd, J = 5.0,
0.9 Hz, 1H, HD6), 8.78 (d, J = 1.7 Hz, 1H, HB3), 8.75 (d, J = 1.7 Hz, 1H,
HB5), 8.74 (ddd, J = 4.7, 1.9, 1.0 Hz, 1H, HA6), 8.72 (dt, J = 7.9, 1.1 Hz,
1H, HA3), 7.90 (m, 4H, HA4+C2+D5), 7.52 (m, 2H, HC3), 7.47 (m, 1H,
HC4), 7.37 (ddd, J = 7.5, 4.8, 1.2 Hz, 1H, HA5), 4.04 (s, 3H, HOMe).
13C{1H} NMR (126 MHz, CDCl3) ␦ (ppm): 166.1 (CC=O), 157.6 (CD2),
156.2 (CA2), 156.1 (CB2), 155.3 (CB6), 150.6 (CB4), 150.0 (CD6), 149.2
(CA6), 138.5 (CC1), 138.4 (CD4), 137.2 (CA4), 129.3 (CC4), 129.1 (CC3),
127.5 (CC2), 124.1 (CA5), 122.9 (CD5), 121.7 (CA3), 120.8 (CD3), 119.5 (CB5),
119.3 (CB3), 52.9 (COMe). ESI-MS (MeOH/CHCl3): m/z 390.0 [M+Na]+
(calcd. 390.1), 368.0 [M+H]+ (base peak, calcd. 368.1). IR (solid, ␯
(cm−1)): 3051 (w), 2969 (w), 1723 (s), 1583 (m), 1548 (m), 1467 (w),
1432 (m), 1378 (s), 1268 (s), 1218 (s), 1132 (w), 1099 (w), 989 (m),
887 (w), 800 (m), 775 (m), 764 (s), 754 (s), 731 (s), 707 (s), 694 (s),
681 (s), 662 (s), 620 (s), 517 (s). UV/VIS ␭ (nm) (CH3CN, 4.44 × 10−5 mol
dm−3) (␧ (dm3 mol−1 cm−1)): 253 (35 000), 276 sh (27 000), 310 sh
(13 000). Found: C 74.41, H 4.67, N 11.22; C23H17N3O2·0.25H2O re-
quires C 74.28, H 4.74, N 11.30%.
Compound 3
4=-F3CSO3-2,2=:6=,2== -Terpyridine (0.80 g, 2.10 mmol) and [Pd-
(PPh3)4] (0.24 g, 0.21 mmol) were suspended in MeCN (17 mL) in a
microwave vial (20 mL) and then NEt3 (0.38 g, 3.78 mmol) and
diethyl phosphite (0.49 g, 3.57 mmol) were added. The brown
suspension was heated in a microwave reactor (140 °C, 30 min)
and then allowed to cool to room temperature. The reaction mix-
ture was diluted with toluene and washed with aqueous NH4OH
(32%) and water. The organic layer was dried over MgSO4, filtered,
and the solvent removed in vacuo. The crude brown solid was
purified by flash column chromatography (SiO2), first eluting with
CH2Cl2 to remove Ph3PO and then with CH2Cl2−MeOH (98:2). Com-
Compound 2
Ammonium acetate (13 g, 160 mmol) was dissolved in MeOH
(150 mL). (E)-1-(Pyridin-2-yl)-3-(pyridin-4-yl)prop-2-en-1-one (0.92 g,
Published by NRC Research Press

726
Can. J. Chem. Vol. 92, 2014
pound 3 was isolated as a pale brown solid (0.65 g, 1.76 mmol,
376.6). HR ESI-MS m/z: 376.5600 [M – 2PF6]2+ (base peak, calcd.
376.5595), 752.1135 [M – H – 2PF6]+ (calcd. 752.1117). UV/VIS ␭ (nm)
(CH3CN, 1 × 10−5 mol dm−3) (␧ dm3 mol−1 cm−1)): 273 (54700), 282 sh
(42000), 311 (50300), 331 sh (33000), 486 (21000). Emission (CH3CN,
3.84 × 10−5 mol dm−3, ␭ex = 486 nm): ␭em = 704 nm. Found: C 42.94,
H 3.76, N 10.33; C37H30F12N7O3P3Ru·H2O·1.5CH3CN(1122.60) re-
quires C 42.81, H 3.28, N 10.16%.
84%). The NMR spectroscopic data matched those published.20
[Ru(3)Cl3]
Compound 3 (0.60 g, 1.63 mmol) and RuCl3·3H2O (0.43 g,
1.63 mmol) were suspended in EtOH (200 mL) and the reaction
mixture was heated at reflux for 3.5 h. The brown solid that
formed was separated by filtration, washed with cold EtOH
and Et2O, and dried in air, yielding a red-brown powder (0.83 g,
1.44 mmol, 88%). The product was used for the next step without
further purification and characterization.
[Ru(1)(4)][PF6]2
The method was as for [Ru(Phtpy)(4)][PF6]2 starting with 1 (71 mg,
0.19 mmol) and [Ru(3)Cl3] (112 mg, 0.19 mmol). [Ru(1)(4)][PF6]2 was
isolated as a red powder (177 mg, 0.161 mmol, 83%). 1H NMR
(400 MHz, CD3CN) ␦ (ppm): 9.15 (d, J = 1.4 Hz, 1H, HB3/B5), 9.12 (d,
JPH = 10. Hz, 2H, HF3), 9.08 (d, J = 1.2 Hz, 1H, HD3), 9.05 (d, J = 1.4 Hz,
1H, HB3/B5), 8.72 (d, J = 8.2 Hz, 2H, HE3), 8.66 (d, J = 7.9 Hz, 1H, HA3),
8.24 (m, 2H, HC2), 7.94 (td, J = 7.9, 1.5 Hz, 1H, HA4), 7.89 (td, J = 7.9,
1.5 Hz, 2H, HE4), 7.77 (m, 2H, HC3), 7.69 (m, 1H, HC4), 7.63 (d, J =
5.8 Hz, 1H, HD6), 7.56 (dd, J = 5.8, 1.8 Hz, 1H, HD5), 7.44 (d, J = 5.5 Hz,
1H, HA6), 7.39 (dd, J = 5.6, 1.4 Hz, 2H, HE6), 7.18 (m, 1H, HA5), 7.13
(ddd, J = 7.7, 5.6, 1.3 Hz, 2H, HE5), 4.07 (m, 2H, HCH2(Et)), 3.90 (s, 3H,
HOMe), 1.29 (t, J = 7.0 Hz, 3H, HCH3(Et)). 13C{1H} NMR (126 MHz,
CD3CN) ␦ (ppm): 165.0 (CC = O), 160.6 (CD2), 159.5 (CE2), 159.0 (CA2),
156.4 (CB2), 156.0 (CB6), 154.7 (CD6), 155.6 (d, JPC = 14 Hz, CF2), 153.7
(CA6), 153.3 (CE6), 149.4 (CB4), 139.4 (CD4), 139.2 (CA4+E4), 137.6 (CC1),
131.4 (CC4), 130.6 (CC3), 129.0 (CC2), 128.6 (CA5+E5), 128.2 (CD5), 127.6
(d, JPC = 10 Hz, CF3), 126.8 (CE3), 126.5 (CA3), 125.1 (CD3), 124.0 (CB3/B5),
123.7 (CB3/B5), 62.1 (CCH2(Et)), 54.3 (COMe), 17.5 (CCH3(Et)) (CF4 not re-
solved). IR (solid, ␯ (cm−1)): 3347 (br m), 1722 (w), 1605 (w), 1363 (m),
1268 (w), 1165 (w), 1137 (w), 1075 (w), 1032 (w), 945 (w), 825 (s),
787 (m), 767 (m), 700 (w), 607 (w). ESI-MS (CH3CN): m/z 809.5 [M – H –
2PF6]+ (base peak, calcd. 809.1). HR ESI-MS m/z: 405.0654 [M –
2PF6]2+ (base peak, calcd. 405.0647), 809.1233 [M – H – 2PF6]+ (calcd.
809.1220). UV/VIS ␭ (nm): (CH3CN, 3.6 × 10−5 mol dm−3) (␧
(dm3 mol−1 cm−1)): 274 (56 000), 285 (51 500), 309 (57 000), 330 sh
(41500), 491 (20 000). Satisfactory elemental analysis was not ob-
tained (see text).
[Ru(Phtpy)(4)][PF6]2
Phtpy (64 mg, 0.21 mmol) and [Ru(3)Cl3] (119 mg, 0.21 mmol)
were suspended in dry EtOH (3.5 mL) in a microwave reactor vial.
N-Ethylmorpholine (three drops) was added and the reaction mix-
ture was heated in a microwave reactor at 140 °C for 15 min. The
dark red solution was poured into aqueous NH4PF6 (250 mL), yield-
ing a red precipitate that was collected on Celite and washed
with cold water (250 mL) and Et2O (20 mL). The residue was redis-
solved in CH3CN and then solvent removed in vacuo to give a dark
red solid. This was purified by column chromatography (SiO2,
eluted with CH3CN − saturated aqueous KNO3 − water 7:1:0.5 by
volume). The first red band was collected, aqueous NH4PF6 added,
and solvent evaporated until a red precipitate formed. This
was collected on Celite and washed thoroughly with cold water
(250 mL), cold EtOH (15 mL), and Et2O (15 mL). The residue
was redissolved in CH3CN and solvent removed in vacuo.
[Ru(Phtpy)(4)][PF6]2 was isolated as a red powder (200 mg,
0.192 mmol, 93%). 1H NMR (400 MHz, CD3CN) ␦ (ppm): 9.06 (d, JPH
=
11 Hz, 2H, HF3), 8.99 (s, 2H, HB3), 8.68 (m, 4H, HA3+E3), 8.20 (m, 2H,
HC2), 7.90 (m, 4H, HA4+E4), 7.76 (m, 2H, HC3), 7.68 (m, 1H, HC4), 7.39
(m, 4H, HA6+E6), 7.15 (m, 4H, HA5+E5), 4.05 (m, 2H, HCH2(Et)), 1.31 (t, J =
7.0 Hz, 3H, HCH3(Et)). 13C{1H} NMR (126 MHz, CD3CN) ␦ (ppm): 159.3
(CE2), 158.8 (CA2), 156.2 (CB2), 155.7 (d, JPC = 12 Hz, CF2), 153.7 (CA6/E6),
153.3 (CA6/E6), 149.2 (CB4), 139.0 (CA4+E4), 137.9 (CC1), 131.3 (CC4), 130.6
(CC3), 128.7 (CC2), 128.5 (CA5/E5), 128.2 (CA5/E5), 126.4 (d, JPC = 20 Hz,
CF3), 125.6 (CA3/E3), 125.4 (CA3/E3), 122.5 (CB3), 61.8 (CCH2(Et)), 17.5
(CCH3(Et)) (CF4 not resolved). IR (solid, ␯ (cm−1)): 3315 (br m), 1662 (w),
1605 (w), 1542 (w), 1473 (w), 1412 (m), 1392 (m), 1345 (m), 1289 (w),
1209 (m), 1162 (w), 1140 (m), 1078 (m), 1034 (m), 962 (w), 898 (w), 826
(s), 791 (s), 764 (s), 733 (m), 689 (s), 664 (m), 603 (m). ESI-MS (MeCN):
m/z 751.4 [M – H – 2PF6]+ (100%, calcd. 751.1). HR ESI-MS m/z:
376.0621 [M – 2PF6]2+ (base peak, calcd. 376.0619), 751.1172 [M – H –
2PF6]+ (calcd. 751.1165). UV/VIS ␭ (nm) (MeCN, 2.88 × 10−5 mol dm−3) (␧
(dm3 mol−1 cm−1)): 274 (59000), 280 sh (54500), 310 (63000), 330 sh
[Ru(2)(4)][PF6]2
The method was as for [Ru(Phtpy)(4)][PF6]2 starting with 2 (50 mg,
0.14 mmol) and [Ru(3)Cl3] (78 mg, 0.14 mmol). [Ru(2)(4)][PF6]2 was
isolated as a red powder (35 mg, 0.032 mmol, 23%). 1H NMR
(500 MHz, CD3CN) ␦ (ppm): 9.23 (d, JPH = 11.5 Hz, 2H, HF3) overlap-
ping with 9.14 (d, J = 1.5 Hz, 1H, HB3/B5), 9.12 (d, J = 1.3 Hz, 1H, HB3/B5),
9.09 (d, J = 1.4 Hz, 1H, HD3), 8.98 (m, 2H, HC2), 8.77 (m, 3H, HA3+E3),
8.19 (m, 2H, HC3), 7.98 (td, J = 8.1, 1.4 Hz, 1H, HA4), 7.92 (td, J = 7.9,
1.5 Hz, 2H, HE4), 7.61 (m, 2H, HD5+D6), 7.46 (d, J = 5.6 Hz, 1H, HA6),
7.38 (dd, J = 5.7, 1.3 Hz, 2H, HE6), 7.21 (m, 1H, HA5), 7.16 (ddd, J = 7.2,
5.6, 1.2 Hz, 2H, HE5), 4.27 (m, 2H, HCH2(Et)), 3.91 (s, 3H, HOMe), 1.41 (t,
J = 6.9 Hz, 3H, HCH3(Et)). 13C{1H} NMR (126 MHz, CD3CN) ␦ (ppm):
164.3 (CC=O), 160.1 (CD2), 159.5 (CF2), 159.3 (CE2), 158.8 (CA2), 157.1
(CB2), 156.5 (CB6), 154.8 (CD6), 153.7 (CA6), 153.4 (CE6), 151.7 (CC2),
146.4 (CB4), 145.2 (CC4), 139.4 (CA4), 139.3 (CE4), 128.6 (CA5), 128.5
(CE5), 127.3 (CD5), 126.4 (d, JPC ≈ 10 Hz, CF3), 126.0 (CE3), 125.7 (CA3),
124.4 (CB3/B5), 123.3 (CB3/B5), 123.0 (CD3), 123.1 (CC3), 62.6 (CCH2(Et)),
53.8 (COMe), 16.9 (CCH3(Et)) (CF4 and CD4 not resolved). IR (solid, ␯
(cm−1)): 3211 (br s), 1729 (m), 1635 (w), 1600 (w), 1475 (w), 1409 (m),
1344 (w), 1313 (m), 1268 (m), 1235 (m), 1165 (m), 1138 (m), 1076 (m),
1030 (m), 950 (m), 826 (s), 786 (s), 753 (m), 688 (m), 652 (m), 605 (m).
ESI-MS (MeCN): m/z 405.6 [M – 2PF6]2+ (calcd. 405.6). HR ESI-MS m/z:
405.5628 [M – 2PF6]2+ (base peak, calcd. 405.5623), 810.1187 [M – H –
2PF6]+ (calcd. 810.1173). UV/VIS ␭ (nm) (CH3CN, 3.63 × 10−5 mol
dm−3) (␧ (dm3 mol−1 cm−1)): 274 (51 000), 284 sh (43 500), 308
(45 000), 330 sh (37 000), 491 (18 500). Satisfactory elemental anal-
ysis could not be obtained (see text).
(34000), 485 (23000). Emission (MeCN, 3 × 10−5 mol dm−3, ␭
=
ex
485 nm): ␭em = 647 nm. Satisfactory elemental analysis could not be
obtained (see text).
[Ru(pytpy)(4)][PF6]2
The method was as for [Ru(Phtpy)(4)][PF6]2 starting with pytpy
(160 mg, 0.52 mmol) and [Ru(3)Cl3] (300 mg, 0.52 mmol). [Ru(pytpy)
(4)][PF6]2 was isolated as a red powder (130 mg, 0.125 mmol, 24%).
1H NMR (500 MHz, CD3CN) ␦ (ppm): 9.05 (d, JPH = 11 Hz, 2H, HF3), 9.03 (s,
1H, HB3), 8.95 (m, 2H, HC2), 8.64 (d, J = 7.9 Hz, 2H, HA3/E3), 8.61 (d, J =
8.1 Hz, 2H, HA3/E3), 8.12 (m, 2H, HC3), 7.94 (m, 2H, HA4/E4), 7.88 (m,
2H, HA4/E4), 7.42 (d, J = 6.7 Hz, 2H, HA6/E6), 7.35 (d, J = 6.7 Hz, 2H,
HE6), 7.18 (m, 2H, HA5/E5), 7.15 (m, 2H, HA5/E5), 4.05 (m, 2H, HCH2(Et)),
1.32 (t, J = 6.8 Hz, 3H, HCH3(Et)). 13C{1H} NMR (126 MHz, CD3CN) ␦
(ppm): 158.7 (CE2), 158.5 (CA2), 158.0 (CF2), 157.0 (CB2), 153.8 (CA6/E6),
153.7 (CA6/E6), 151.5 (CC2), 145.3 (CB4+C4), 139.3 (CA4+E4), 128.8 (CA5/E5),
128.6 (CA5/E5), 126.2 (d, JPC ≈ 20 Hz, CF3), 126.1 (CA3/E3), 126.0 (CA3/E3),
123.2 (CB3), 123.1 (CC3), 63.2 (CCH2(Et)), 17.2 (CCH3(Et)) (CF4 not re-
solved). IR (solid, ␯ (cm−1)): 3350 (br s), 1660 (w), 1599 (s), 1532 (w),
1475 (m), 1394 (m), 1352 (w), 1291 (w), 1202 (s), 1166 (w), 1075 (m),
1069 (m), 1038 (m), 1028 (s), 942 (m), 844 (s), 826 (s), 818 (s), 784 (m),
776 (m), 745 (m). ESI-MS (CH3CN): m/z 376.5 [M – 2PF6]2+ (calcd.
Crystal structure determination of 1
Data were collected on a Bruker-Nonius Kappa APEX diffrac-
tometer; data reduction, solution, and refinement used APEX221
Published by NRC Research Press

Constable et al.
727
and SHELX13.22 Absorption correction was made using the pro-
gram “sadabs” as part of the “scale” package in AEPX2 software.21
The ORTEP plot was produced with Mercury v. 3.0,23,24 which was
also used for structure analysis. C23H17N3O2, M = 367.40, colorless
plate, crystal dimensions 0.25 mm × 0.13 mm × 0.03 mm, mono-
clinic, space group P21/c, a = 9.9644(9), b = 9.0359(8), c = 20.0424(17)
Å, ␤ = 96.975(6)°, U = 1791.2(3) Å3, Z = 4, Dc = 1.362 Mg m−3, ␮(Cu-
K␣) = 8.224 mm−1, T = 123 K. Total 18 887 reflections, 3181 unique,
Model compounds containing Phtpy and pytpy (Scheme 1) were
first prepared by reaction of [Ru(3)Cl3] with Phtpy and pytpy in the
presence of N-ethylmorpholine. After anion exchange and chro-
matographic workup, followed by a second anion exchange (to
remove [NO3]− introduced from aqueous KNO3 in the eluant), the
ruthenium(II) salts were isolated as red solids. Electrospray mass
spectrometic and NMR spectroscopic data were consistent with
the isolated products being complexes of the monoester 4
(Scheme 2) rather than the diester 3. Partial hydrolysis of 3 during
synthesis of ruthenium(II) complexes is known to occur under
conditions of high temperature reflux20 or heating in DMF at
60 °C.27 The second hydrolysis step to the phosphonic acid needs
acidic conditions or treatment with Me3SiBr. The ESI mass spec-
trum of [Ru(Phtpy)(4)][PF6]2 showed the base peak envelope at m/z
751.4 with an appropriate isotope pattern for the ion [M – H –
2PF6]+. The loss of H+ is consistent with the presence of the acidic
P–OH group. The high-resolution ESI (HR-ESI) mass spectrum was
also recorded and peaks arising from [M – H – 2PF6]+ and [M –
2PF6]2+ confirmed the identity of [Ru(Phtpy)(4)]2+. The HR-ESI mass
spectrum of [Ru(pytpy)(4)][PF6]2 exhibited peak envelopes arising
from the [M – H – 2PF6]+ and [M – 2PF6]2+ ions, and the latter was
also observed in the ESI mass spectrum.
Rint = 0.0428. Refinement of 2763 reflections (254 parameters) with
I > 2␴(I) converged at final R1 = 0.0378 (R1 all data = 0.0439), wR2 =
0.1009 (wR2 all data = 0.1048), goodness-of-fit = 1.064.
Results and discussion
Synthesis and characterization of ligands 1 and 2
Compounds 1 and 2 (Scheme 1) are the 4=-phenyl and 4=-(4-
pyridyl) analogues of 4=-tolyl-2,2=:6=,2== -terpyridine, the prepara-
tion and homoleptic ruthenium(II) complex of which were
reported a decade ago by Potvin and co-worker.25 Scheme 2 shows
the Kröhnke synthesis of 1 and 2, which yielded the compounds in
33% and 89%, respectively, as white solids. In the electrospray
mass spectrum of 1, the base peak (m/z = 338.0) arises from the [M +
H]+ ion, and a lower intensity peak at m/z = 390.0 was assigned to
[M + Na]+. Corresponding peaks at m/z 369.2 and 391.1 in the mass
spectrum of 2 were also observed. The 1H and 13C NMR spectra of
1 and 2 were fully assigned with COSY, HMQC, and HMBC tech-
niques and were consistent with the inequivalence of the outer
pyridine rings of the tpy domain (Scheme 1) and the presence of
the ester group.
1
The H and 13C NMR spectra of CD3CN solutions of [Ru(Phtpy)
(4)][PF6]2 and [Ru(pytpy)(4)][PF6]2 were consistent with the presence
of two tpy environments in each complex. A representative spec-
trum is shown in Fig. 2. Spectra were assigned using 2D methods
1
(COSY, HMQC, and HMBC); 400 MHz H spectra were routinely
1
recorded for better resolution of signals and 500 MHz H for 2D
measurements. The most characteristic feature of the spectrum in
Fig. 2 is the appearance of a singlet for protons HB3 (Phtpy ligand)
and a doublet for the corresponding protons HF3 (ligand 4) arising
from 31P−1H coupling (11 Hz). For [Ru(Phtpy)(4)][PF6]2, signals at ␦
4.05 and 1.31 ppm in the 1H NMR spectrum and their relative
integrals with respect to resonances in the aromatic region were
consistent with the monoester 4; in the 13C NMR spectrum, corre-
sponding signals at ␦ 61.8 and 17.5 ppm were observed.
Single crystals of 1 were grown by slow evaporation from a
CHCl3 solution of the compound and the structure (Fig. 1) was
confirmed by X-ray diffraction. Important bond parameters are
given in the figure caption. The tpy unit adopts a trans,trans-
conformation, which is expected for a nonprotonated ligand. The
tpy domain is essentially planar (the angles between the least
squares planes through the rings containing N1/N2 and N2/N3 =
5.5° and 4.5°); the phenyl ring is twisted 27.6° with respect to the
pyridine ring to which it is attached, consistent with minimizing
H···H repulsions between the two rings. The dominant packing
interactions are (1) face-to-face ␲-stacking of tpy domains across
The preparations of [Ru(1)(4)][PF6]2 and [Ru(2)(4)][PF6]2 were car-
ried out in an analogous manner to those of [Ru(Phtpy)(4)][PF6]2
and [Ru(pytpy)(4)][PF6]2. The base peak in the ESI mass spectrum of
[Ru(1)(4)][PF6]2 was assigned to [M – H – 2PF6]+; for [Ru(2)(4)][PF6]2,
the main peak envelope arose from [M – 2PF6]2+. High-resolution
ESI data showed peaks arising from [M – 2PF6]2+ and [M – H – 2PF6]+
for both complexes. The solution 1H and 13C NMR spectra (as-
signed by 2D methods) of [Ru(1)(4)][PF6]2 and [Ru(2)(4)][PF6]2 were
consistent with the presence of the symmetrical ligand 4 and one
asymmetrical ligand. Figure 3 shows part of the 1H NMR spectrum
of [Ru(2)(4)][PF6]2. The doublet for HF3 (JPH = 11.5 Hz) overlaps with
inversion centres, (2) Hmethyl···Npyridine contacts (H23A···N1i
=
2.98, H23B···N1i = 2.81 Å, symmetry code i = 1 + x, 1 + y, z), and
(3) Npyridine···HC contacts (N3···H3Aii–C3ii = 2.57 Å, symmetry code
ii = x, 3/2 – y, 1/2 + z).
The diethylphosphonate-functionalized ligand 3 has previously
been reported by Grätzel and co-workers.20 The literature synthe-
sis (which gives 3 in 72.3% yield) involves the [Pd(PPh3)4] catalysed
reaction of 4=-bromo-2,2=:6=,2== -terpyridine with diethyl phosphite
in NEt3 (95 °C for 3 h) followed by dissolution of the mixture in
MeOH and chromatographic workup. We adopted the more con-
venient strategy shown in Scheme 2. The 4=-triflate-functionalized
tpy was readily prepared according to the route described by Potts
et al.,19 and diethylphosphonate for triflate substitution occurs
under microwave conditions to give 3 in 84% yield (Scheme 3). The
NMR spectroscopic data for 3 were consistent with those pub-
lished.20
one of the two doublets (JHH 1.3 or 1.5 Hz) arising from HB3 and HB5
.
Pairs of signals for HE3/HA3, HE4/HA4, HE5/HA5, and HE6/HA6 with
relative integrals 2:1 appear for the unsubstituted pyridine rings
in ligand 4 and for ligands 1 or 2, respectively. The signal for HD3
(JHH = 1.4 Hz) was distinguished from those of HB3 and HB5 by its
COSY signature. The relative integrals for the signals for the ethyl
groups in 4 in both complexes were consistent with the monoester.
Yields of [Ru(Phtpy)(4)][PF6]2 and [Ru(1)(4)][PF6]2 were >80%, but
for the complexes containing pytpy, lower yields of approxi-
mately 25% were observed, due, in part, to formation of some of
the N-protonated species. We noted changes in the 1H NMR spec-
tra that were consistent with protonation of samples in solution.
Satisfactory elemental analysis could not always be obtained for
the hexafluoridophosphate salts, probably due to small amounts
Synthesis and characterization of heteroleptic
ruthenium(II) complexes
The heteroleptic complexes discussed in this section are sum-
marized in Scheme 4. Heteroleptic [Ru(Xtpy)(Ytpy)]2+ complexes
are typically prepared by first preparing an insoluble, paramag-
netic ruthenium(III) complex [Ru(Xtpy)Cl3] and treating this crude
material with Ytpy in the presence of N-ethylmorpholine, which
acts as a reducing agent.26 The precursor for the formation of the
new ruthenium(II) complexes was [Ru(3)Cl3], prepared by reaction
of RuCl3.3H2O with compound 3 in MeOH under reflux. [Ru(3)Cl3]
was isolated as a brown solid.
1
of residual NH4PF6. Traces of [NH4]+ were seen in the H NMR
spectra (␦ 6.02, J(14N1H) = 53 Hz) of some batches of the complexes.
X-ray-quality crystals of solvated [Ru(pytpy)(4)][PF6]2 were ob-
tained, but only preliminary structural data could be obtained
because of persistent twinning problems. However, these data
were sufficient to confirm the presence of the monoester ligand 4
and the octahedral coordination environment of the rutheni-
Published by NRC Research Press

728
Can. J. Chem. Vol. 92, 2014
Scheme 2. Synthetic route to ligands 1 and 2. Conditions: (i) MeOH, reflux.
Fig. 1. ORTEP representation of the structure of 1 (ellipsoids plotted
at 50% probability level). Selected bond parameters: N1–C1 = 1.342(2),
N1–C5 = 1.3386(19), N2–C6 = 1.3415(18), N2–C10 = 1.3412(17), N3–C11 =
1.3463(17), N3–C15 = 1.3295(19), C13–C22 = 1.4993(19), O1–C22 = 1.2052(18),
C22–O2 = 1.3309(18), O2–C23 = 1.4524(18) Å; C5–N1–C1 = 117.26(13), C6–N2–
C10 = 117.72(12), C15–N3–C11 = 117.80(12), O1–C22–O2 = 124.63(13), O1–C22–
C13 = 124.21(13), O2–C22–C13 = 111.15(12), C22–O2–C23 = 117.15(12)°.
Scheme 4. Structures of the heteroleptic complex cations prepared
as hexafluoridophosphate salts.
Fig. 2. Aromatic region of the 400 HMz 1H NMR spectrum of
[Ru(Phtpy)(4)][PF6]2. See Scheme 1 for ring labelling.
Scheme 3. Synthesis of phosphonate 4. Conditions: (i) [Pd(PPh3)4],
NEt3, HP(O)(OEt)2, MeCN, 140 °C, 30 min.
Fig. 3. Aromatic region of the 500 HMz 1H NMR spectrum of
[Ru(2)(4)][PF6]2. See Scheme 1 for ring labelling.
um(II) centre bound by the bis(chelating) donor sets of pytpy and
ligand 4. Despite attempts, X-ray-quality single crystals of the
other ruthenium(II) complexes were not obtained.
Absorption and emission spectroscopic properties
The absorption spectra of MeCN solutions of the complexes are
shown in Fig. 4. Each exhibits a series of high-energy bands arising
from ligand-based, spin-allowed transitions and a broad MLCT
band in the visible region. The values of ␭
for the MLCT
max
absorptions (485–491 nm, see Experimental section) compare
with 488 nm for both [Ru(Phtpy)2][PF6]226 and [Ru(pytpy)2][PF6]2.28
The spectra for [Ru(Phtpy)(4)][PF6]2 and [Ru(pytpy)(4)][PF6]2 are sim-
ilar to one another and to those of the homoleptic complexes
Published by NRC Research Press

Constable et al.
729
Fig. 4. Absorption spectra of MeCN solutions of [Ru(Phtpy)(4)][PF6]2,
[Ru(pytpy)(4)][PF6]2, [Ru(1)(4)][PF6]2, and [Ru(2)(4)][PF6]2. See
Experimental section for concentrations.
Table 1. Cyclic voltammetric data for the ruthenium(II)
complexes with respect to Fc/Fc+ in MeCN solutions with
[tBu4N][PF6] as supporting electrolyte and a scan rate of
0.1 V s−1 (ir, irreversible; qr, quasi-reversible).
Complex
E1/2ox (V)
E1/2red (V)
[Ru(Phtpy)(4)][PF6]2
[Ru(1)(4)][PF6]2
[Ru(pytpy)(4)][PF6]2
[Ru(2)(4)][PF6]2
+0.93
+0.96
+1.01
+1.04
−1.68, −1.93qr
−1.49, −1.90, −2.23ir
−1.57, −2.00ir
−1.43, −1.85
Supplementary material
CCDC 983369 contains the supplementary crystallographic
data for this paper. These data can be obtained, free of charge,
via http://www.ccdc.cam.ac.uk/products/csd/request/ (or from
the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: 44-1223-336033 or e-mail: deposit@
ccdc.cam.ac.uk)).
Acknowledgements
26
[Ru(Phtpy)2][PF6]2 and [Ru(pytpy)2][PF6]2.28 The introduction of
We thank the Swiss National Science Foundation, the European
Research Council (advanced grant 267816 LiLo), and the University
of Basel for financial support. Sven Brauchli and Dr. Heinz Nadig
are acknowledged for recording mass spectra. Angelo Lanzilotto
is thanked for assistance with absorption spectroscopic measure-
ments.
the methyl ester substituent leads to a change in the appearance of
the absorption maxima (Fig. 4), the trend being the same on going
from [Ru(Phtpy)(4)][PF6]2 to [Ru(1)(4)][PF6]2, and from [Ru(pytpy)(4)][PF6]2
to [Ru(2)(4)][PF6]2. The small red shift in the MLCT band upon intro-
duction of the CO2Me group is consistent with that observed on
going from [Ru(ttpy)2]2+ to [Ru(4-MeO2Cttpy)2]2+ (ttpy = 4=-tolyl-2,2=:
6=,2== -terpyridine; 4-MeO2Cttpy = 4-carboxymethyl-4=-tolyl-2,2=:6=,2== -
terpyridine).25
Excitation into the MLCT band of each of [Ru(Phtpy)(4)][PF6]2
and [Ru(1)(4)][PF6]2 (in degassed MeCN at room temperature) gives
rise to a weak emission at 647 and 665 nm, respectively, with a
quantum yield below the detection limit of the instrument (<1%).
References
(1) See for example: (a) Sauvage, J.-P.; Collin, J.-P.; Chambron, J. C.; Guillerez, S.;
Coudret, C.; Balzani, V.; Barigelletti, F.; De Cola, L.; Flamigni, L. Chem. Rev.
1994, 94, 993. doi:10.1021/cr00028a006; (b) Constable, E. C. Chem. Commun.
1997, 1073. doi:10.1039/A605102B; (c) Baranoff, E.; Collin, J.-P.; Flamigni, L.;
Sauvage, J.-P. Chem. Soc. Rev. 2004, 33, 147. doi:10.1039/b308983e;
(d) Andres, P. R.; Schubert, U. S. Adv. Mater. 2004, 16, 1043. doi:10.1002/adma.
200306518.
(2) Kröhnke, F. Synthesis 1976, 1. doi:10.1055/s-1976-23941.
(3) Campagna, S.; Puntoriero, F.; Nastasi, F.; Bergamini, G.; Balzani, V. Topic
Curr. Chem. 2007, 280, 117. doi:10.1007/128_2007_133.
(4) Maestri, M.; Armaroli, N.; Balzani, V.; Constable, E. C.; Cargil Thompson, A. M. W.
Inorg. Chem. 1995, 34, 2759. doi:10.1021/ic00114a039.
(5) Grätzel, M. Inorg. Chem. 2005, 44, 6841. doi:10.1021/ic0508371.
(6) Bozic-Weber, B.; Constable, E. C.; Housecroft, C. E. Coord. Chem. Rev. 2013,
257, 3089. doi:10.1016/j.ccr.2013.05.019.
Electrochemical properties
The complexes are electrochemically active and cyclic voltam-
metric data are given in Table 1. The reversible oxidation observed
for each complex arises from the Ru2+/Ru3+ couple. For the parent
[Ru(tpy)2]2+, this process occurs at +0.918 V,26 and introducing
electron-donating phenyl groups shifts it to lower potential
(+0.895 V in [Ru(Phtpy)2][PF6]2).26 Replacing one phenyl substitu-
ent by the electron-withdrawing phosphonic ester group shifts
the oxidation to +0.93 V (Table 1). A similar trend is seen on com-
paring the Ru2+/Ru3+ potential in [Ru(pytpy)2][PF6]2 (+0.95 V)28 with
that in [Ru(pytpy)(4)][PF6]2 (+1.01 V). Introduction of the methyl
ester unit results in a 0.03 V shift to more positive potential on
going from [Ru(Phtpy)(4)][PF6]2 to [Ru(1)(4)][PF6]2 or from [Ru(pytpy)
(4)][PF6]2 to [Ru(2)(4)][PF6]2. This is consistent with the trend ob-
(7) Bozic-Weber, B.; Brauchli, S.; Constable, E. C.; Fürer, S. O.; Housecroft, C. E.;
Wright, I. A. Phys. Chem. Chem. Phys. 2013, 15, 4500. doi:10.1039/C3CP50562F.
(8) See for example: (a) Fan, S.-Q.; Kim, C.; Fang, B.; Liao, K.-X.; Yang, G.-J.;
Li, C.-J.; Kim, J.-J.; Ko, J. J. Phys. Chem. C. 2011, 115, 7747. doi:10.1021/jp200700e;
(b) Wang, S.-W.; Wu, K.-L.; Ghadiri, E.; Lobello, M. G.; Ho, S.-T.; Chi, Y.;
Moser, J.-E.; De Angelis, F.; Grätzel, M.; Nazeeruddin, M. K. Chem. Sci., 2013,
4, 2423. doi:10.1039/c3sc50399b; (c) Nguyen, L. H.; Mulmudi, H. K.; Sabba, D.;
Kulkarni, S. A.; Batabyal, S. K.; Nonomura, K.; Grätzel, M.; Mhaislkar, S. G.
Phys. Chem. Chem. Phys. 2012, 14, 16182. doi:10.1039/C2CP42959D.
(9) He, J.; Lindström, H.; Hagfeldt, A.; Lindquist, S.-E. Solar Ener. Mater. Solar Cells
2000, 62, 265. doi:10.1016/S0927-0248(99)00168-3.
(10) Mishra, A.; Fischer, M. K. R.; Bäuerle, P. Angew. Chem. Int. Ed. 2009, 48, 2474.
doi:10.1002/anie.200804709.
(11) Pellegrin, Y.; Le Pleux, L.; Blart, E.; Renaud, A.; Chavillon, B.;
Szuwarski, N.; Boujtita, M.; Cario, L.; Jobic, S.; Jacquemin, D.; Odobel, F.
J. Photochem. Photobiol. A 2011, 219, 235. doi:10.1016/j.jphotochem.2011.02.025.
(12) Constable, E. C.; Homes, J. M. J. Organomet. Chem. 1986, 301, 203. doi:10.1016/
0022-328X(86)80011-0.
served from [Ru(ttpy)2]2+ to [Ru(4-MeO2Cttpy)2]2+ 25
A series of
ligand-based reduction processes is observed for each complex
(Table 1), consistent with expectations based on related com-
pounds.
.
(13) Reveco, P.; Cherry, W. R.; Medley, J.; Garber, A.; Gale, R. J.; Selbin, J. Inorg.
Chem. 1986, 25, 1842. doi:10.1021/ic00231a025.
Conclusions
(14) Ji, Z.; Natu, G.; Huang, Z.; Kokhan, O.; Zhang, X.; Wu, Y. J. Phys. Chem. C 2012,
116, 16854. doi:10.1021/jp303909x.
(15) Ji, Z.; Wu, Y. J. Phys. Chem. C 2013, 117, 18315. doi:10.1021/jp405659m.
(16) Eryazici, I.; Moorefield, C. N.; Durmus, S.; Newkome, G. R. J. Org. Chem. 2006,
71, 1009. doi:10.1021/jo052036l.
(17) Zhao, L.-X.; Kim, T. S.; Ahn, S.-H.; Kim, T.-H.; Kim, E.; Cho, W.-J.; Choi, H.;
Lee, C.-S.; Kim, J.-A.; Jeong, T. C.; Chang, C.; Lee, E.-S. Bioorg. Med. Chem. Lett.
2001, 11, 2659. doi:10.1016/S0960-894X(01)00531-5.
(18) Wang, J.; Hanan, G. S. Synlett 2005, 8, 1251. doi:10.1055/s-2005-868481.
(19) Potts, K. T.; Konwar, D. J. Org. Chem. 1991, 56, 4815. doi:10.1021/jo00015a050.
(20) Zakeeruddin, S. M.; Nazeeruddin, M. K.; Pechy, P.; Rotzinger, F. P.;
Humphry-Baker, R.; Kalyanasundaram, K.; Grätzel, M. Inorg. Chem. 1997, 36,
5937. doi:10.1021/ic970008i.
We have prepared and characterized four new heteroleptic
complexescontaining{Ru(tpy)2}cores. Oneligandcontainsaphos-
phonate ester group designed to act as an anchoring group to
metal oxide surfaces. The second ligand is Phtpy or pytpy in the
model systems and contains a methyl ester functionality in the
second of each pair of complexes. This provides a suitable site for
variable functionalization, for example, through transesterifica-
tion. We plan to use the heteroleptic complexes as a starting point
for development of ruthenium(II) dyes suited for sensitization of
p-type semiconductors.
Published by NRC Research Press

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Can. J. Chem. Vol. 92, 2014
(21) APEX2, Version 2 User Manual, M86-E01078; Bruker Analytical X-ray Systems,
Inc.: Madison, WI, 2006.
(22) Sheldrick, G. M. Acta Cryst. 2008, A64, 112. doi:10.1107/S0108767307043930.
(23) Bruno, I. J.; Cole, J. C.; Edgington, P. R.; Kessler, M. K.; Macrae, C. F.;
McCabe, P.; Pearson, J.; Taylor, R. Acta Cryst. 2002, B58, 389. doi:10.1107/
S0108768102003324.
(25) Mikel, C.; Potvin, P. G. Polyhedron 2002, 21, 49. doi:10.1016/S0277-5387(01)
00959-7.
(26) Constable, E. C.; Cargill Thompson, A. M. W.; Tocher, D. A.; Daniels, M. A. M.
New J. Chem. 1992, 16, 855.
(27) Zhong, D. K.; Zhao, S.; Polyansky, D. E.; Fujita, E. J. Catal. 2013, 307, 140.
doi:10.1016/j.jcat.2013.07.018.
(24) Macrae, C. F.; Bruno, I. J.; Chisholm, J. A.; Edgington, P. R.; McCabe, P.;
Pidcock, E.; Rodriguez-Monge, L.; Taylor, R.; van de Streek, J.; Wood, P. A.
J. Appl. Cryst. 2008, 41, 466. doi:10.1107/S0021889807067908.
(28) Constable, E. C.; Cargill Thompson, A. M. W. J. Chem. Soc., Dalton Trans. 1994,
1409. doi:10.1039/DT9940001409.
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