Systematic modulation of a bichromic cyclometalated ruthenium(II) scaffold bearing a redox-active triphenylamine constituent

Article abstract of DOI:10.1021/ic1025679

The syntheses and physicochemical properties of nine bis-tridentate ruthenium(II) complexes containing one cyclometalating ligand furnished with terminal triphenylamine (TPA) substituents are reported. The structure of each complex conforms to a molecular scaffold formulated as [Ru^II(TPA-2,5- thiophene-pbpy)(Me₃tctpy)] (pbpy = 6-phenyl-2,2′-bipyridine; Me₃tctpy = trimethyl-4,4′,4″-tricarboxylate-2,2′: 6′,2″-terpyridine), where various electron-donating groups (EDGs) and electron-withdrawing groups (EWGs) are installed about the TPA unit and the anionic ring of the pbpy ligand. It is found that the redox chemistry of the Ru center and the TPA unit can be independently modulated by (i) placing EWGs (e.g., -CF₃) or EDGs (e.g., -OMe) on the anionic ring of the pbpy ligand (substituted sites denoted as R₂ or R₃) and/or (ii) installing electron-donating substituents (e.g., -H, -Me, -OMe) para to the amine of the TPA group (i.e., R₁). The first oxidation potential is localized to the TPA unit when, for example, EDGs are placed at R₁ with EWGs at R₂ (e.g., the TPA^?+/TPA⁰ and Ru^III/Ru^II redox couples appear at +0.98 and +1.27 V vs NHE, respectively, when R₁ = -OMe and R₂ = -CF ₃). This situation is reversed when R₃ = EDG and R ₁ = -H: TPA-based and metal-centered oxidation waves occur at +1.20 and +1.11 V vs NHE, respectively. The UV-vis spectrum for each complex is broad (e.g., absorption bands are extended from the UV region to beyond 800 nm in all cases) and intense (e.g., ε ～ 10⁴ M ^-1?cm^-1) because of the overlapping intraligand charge-transfer and metal-to-ligand charge-transfer transitions. The information derived from this study offers guiding principles for modulating the physicochemical properties of bichromic cyclometalated ruthenium(II) complexes.

Full text of DOI:10.1021/ic1025679

ARTICLE
pubs.acs.org/IC
Systematic Modulation of a Bichromic Cyclometalated Ruthenium(II)
Scaffold Bearing a Redox-Active Triphenylamine Constituent
Kiyoshi C. D. Robson,† Barbora Sporinova,† Bryan D. Koivisto,† Eduardo Schott,‡ Douglas G. Brown,† and
Curtis P. Berlinguette*,†
†Department of Chemistry and Institute for Sustainable Energy, Environment and Economy, University of Calgary,
2500 University Drive NW, Calgary, Canada T2N 1N4
‡
ꢀ
Departamento de Ciencias Quimicas, Universidad Andres Bello, Repꢀublica 275, Santiago, Chile
S Supporting Information
b
ABSTRACT: The syntheses and physicochemical properties of nine bis-tridentate
ruthenium(II) complexes containing one cyclometalating ligand furnished with terminal
triphenylamine (TPA) substituents are reported. The structure of each complex conforms
to a molecular scaffold formulated as [RuII(TPA-2,5-thiophene-pbpy)(Me3tctpy)] (pbpy =
6-phenyl-2,20-bipyridine; Me3tctpy = trimethyl-4,40,400-tricarboxylate-2,20:60,200-terpyri-
dine), where various electron-donating groups (EDGs) and electron-withdrawing groups
(EWGs) are installed about the TPA unit and the anionic ring of the pbpy ligand. It is found
that the redox chemistry of the Ru center and the TPA unit can be independently
modulated by (i) placing EWGs (e.g., ꢀCF3) or EDGs (e.g., ꢀOMe) on the anionic ring of
the pbpy ligand (substituted sites denoted as R2 or R3) and/or (ii) installing electron-
donating substituents (e.g., ꢀH, ꢀMe, ꢀOMe) para to the amine of the TPA group (i.e.,
R1). The first oxidation potential is localized to the TPA unit when, for example, EDGs are
placed at R1 with EWGs at R2 (e.g., the TPA•þ/TPA0 and RuIII/RuII redox couples appear
at þ0.98 and þ1.27 V vs NHE, respectively, when R1 = ꢀOMe and R2 = ꢀCF3). This situation is reversed when R3 = EDG and R1 =
ꢀH: TPA-based and metal-centered oxidation waves occur at þ1.20 and þ1.11 V vs NHE, respectively. The UVꢀvis spectrum for
each complex is broad (e.g., absorption bands are extended from the UV region to beyond 800 nm in all cases) and intense (e.g., ε ∼
104 Mꢀ1 cmꢀ1) because of the overlapping intraligand charge-transfer and metal-to-ligand charge-transfer transitions. The
3
information derived from this study offers guiding principles for modulating the physicochemical properties of bichromic
cyclometalated ruthenium(II) complexes.
’ INTRODUCTION
that the cyclometalated complex [Ru(dcbpyH2)2(ppyF2)]þ
[ppyF2 = 2-(2,4-difluorophenyl)pyridine] could generate power
conversion efficiencies in excess of 10.1%.4 This result has
heralded a new paradigm of dye development because it repre-
sents the first “champion” (i.e., η > 10%) dye devoid of
NCSꢀ groups.2,11ꢀ16
Cyclometalated ruthenium(II) complexes have recently emerged
as a promising class of sensitizers for use in dye-sensitized solar
cells (DSSCs).1ꢀ7 Indeed, complexes formulated as [Ru(dcbpy)2-
(C∧N)]þ [dcbpy = 4,40-dicarboxy-2,200-bipyridine; C∧N = cy-
clometalating ligand (e.g., 2-phenylpyridine)] have proven to be
viable alternatives to conventional high-performance ruthenium-
based dyes [e.g., [Ru(dcbpy)2(NCS)2] (N3)]8 because of their
broad absorbance profiles and suitable ground- and excited-state
oxidation potentials.4,5 Moreover, cyclometalated derivatives
offer a significant advantage over conventional dyes in that the
absence of NCSꢀ ligands about the Ru center circumvents access
to significant degradation pathways within an operating cell; e.g.,
the monodentate NCSꢀ groups can be displaced by additives in
the electrolyte.9 The first documented DSSC containing a
cyclometalated Ru sensitizer was provided by van Koten et al.
in the form of a bis-tridentate complex [e.g., [RuII(tpy)-
(pdcbpy)]þ (tpy = 2,20:60,200-terpyridine; pdcbpy = 4,40-dicar-
boxy-6-phenyl-2,20-bipyridine].3 While the performance of this
dye in the DSSC was modest, we have shown that derivatives of
this complex can exceed power conversion efficiencies (η) of 8%.10
Moreover, independent report by Gr€atzel et al., demonstrated
Building on these and related studies by Sauvage et al.,17ꢀ20
Hammarstr€om et al.,13,21,22 and others,23ꢀ26 our program has
focused exclusively on systematically modulating bidentate and
tridentate cyclometalated ruthenium(II) complexes to gain a
fundamental understanding of how to modulate the optical and
electrochemical properties of this class of dyes. In general,
cyclometalated ruthenium complexes contain a highest occupied
molecular orbital (HOMO) that is extended over the metal and
anionic portion of the cyclometalating ligand.5,15,27ꢀ31 Because
the lowest unoccupied molecular orbital (LUMO) is localized to
the neutral polypyridyl ligands, a series of broad absorption
bands in the visible region arise from a suite of mixed-metal-
ligand-to-ligand charge-transfer transitions.15,32 Notably, these
Received: December 24, 2010
Published: June 09, 2011
r
2011 American Chemical Society
6019
dx.doi.org/10.1021/ic1025679 Inorg. Chem. 2011, 50, 6019–6028
|

Inorganic Chemistry
ARTICLE
Chart 1. Designation of Compoundsa
aCounterion = NO3ꢀ for 1ꢀ9.
transitions also position the excited-state electron density on the
polypyridyl ligand attached to the semiconductor to enable rapid
and efficient charge injection into a TiO2 collecting electrode.5,33ꢀ35
Moreover, replacement of the NCSꢀ groups with a cyclometa-
lating ligand offers the unique opportunity to independently tune
both the metal-based HOMO and the ligand π*-based LUMO.28,36
To further expand on this chemistry, we have set out to
consolidate these organometallic dyes8,37ꢀ42 with organic tri-
phenylamine (TPA) fragments43ꢀ46 as a means of generating
broad, intense absorbance bands in the visible region. While bis-
tridentate polypyridylruthenium complexes containing TPA
donor units are known,47,48 they are not ideal for sensitizing
TiO2 because of a relatively narrow absorption band coupled
with a low π* energy level.33,49 An examination of heteroleptic
cyclometalated ruthenium(II) bichromic complexes disclosed in
our previous study demonstrated that cyclometalating ligands
serve to desymmetrize the local geometry and raise the filled
frontier orbitals to induce a broad spectral profile extending
beyond 800 nm, while pushing up the π* energy levels to
enhance the possibility for electron injection into TiO2.10 More-
over, we have found that the TPA and metal-based chromo-
phores exist as electrochemically independent units, thereby
offering acute control of each of the chromophore units.
Our previous work identified that the optimal dye motif for
sensitizing TiO2 is the situation where the organometallic bond is
located cis to the central ring of the tridentate TPA-bearing
ligand (e.g., Chart 1).10 Not only does this arrangement balance
light absorption and electron-injection events, it also provides
the opportunity to induce an electronic cascade effect that
effectively shuttles holes away from the surface.47,50ꢀ54 Under
the auspices of these motivating factors, we detail herein our
efforts to further develop the molecular platform in Chart 1 to
examine how the optical and electrochemical properties are
affected by terminal substituents at both TPA (e.g., R1) and the
metal chelate (e.g., R2 and R3). This family of bichromic dyes
reveals that the ruthenium-based redox potential can be tuned
independently of the TPA redox potential by substitution of the
R2/R3 positions of the pbpy chelate with electron-withdrawing
groups (EWGs; i.e., ꢀCF3) or electron-donating groups (EDGs;
i.e., ꢀOMe). Similarly, tuning of the TPA•þ/TPA0 oxidation
potential can be achieved by substitution (e.g., ꢀH, ꢀMe, ꢀOMe)
at the R1 site of the TPA without affecting the metal-based redox
potentials. Systematic substitution of these two chromophore units
reveals that the electrochemical behavior can be adjusted such that the
HOMO resides on either the metal or the TPA unit. This control over
the relative energy alignment between the two chromophores offers
another handle for optimizing this class of dyes for the DSSC and
presents a promising route for developing “black dye” analogues that
are devoid of NCSꢀ groups.55
’ EXPERIMENTAL SECTION
Preparation of Compounds. All reactions and manipulations
were performed using solvents passed through an MBraun solvent
purification system prior to use. All reagents were purchased from
Aldrich except for RuCl3 3H2O (Pressure Chemical Co., Pittsburgh, PA)
3
and trimethyl-4,40,400-tricarboxylate-2,20:60,200-terpyridine (L10; Helios
Chemical Co., Ecublens, Switzerland). Purification by column chroma-
tography was carried out using silica (silicycle: ultrapure flash silica).
Analytical thin-layer chromatography was performed on aluminum-
backed sheets precoated with silica 60 F254 adsorbent (0.25 mm thick;
Merck, Darmstadt, Germany) and visualized under UV light. Routine 1H
and 13C NMR spectra were recorded at 400 and 100 MHz, respectively,
on a Bruker AV 400 instrument at ambient temperature. Chemical shifts
(δ) are reported in parts per million (ppm) from low to high field and
referenced to a residual nondeuterated solvent. Standard abbreviations
indicating multiplicity are used as follows: s = singlet; d = doublet; t =
triplet; m = multiplet. All proton assignments correspond to the generic
molecular schemes that are provided (Figure 1). Organic compounds N,N-
diphenyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (P1),56
4-methyl-N-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-
N-p-tolylaniline (P2),57 4-methoxy-N-(4-methoxyphenyl)-N-[4-(4,4,5,
5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]aniline (P3),58 4-(5-bro-
mothiophen-2-yl)-6-phenyl-2,20-bipyridine (P4),10 N,N-diphenyl-4-[5-
(6-phenyl-2,20-bipyridin-4-yl)thiophen-2-yl]aniline (L1H),10 4-methyl-
N-[4-[5-(6-phenyl-2,20-bipyridin-4-yl)thiophen-2-yl]phenyl]-N-p-tolyl-
aniline (L2H),10 4-methoxy-N-(4-methoxyphenyl)-N-[4-[5-(6-phenyl-2,
20-bipyridin-4-yl)thiophen-2-yl]phenyl]aniline (L3H),10 and 6-phenyl-2,
20-bipyridine (pbpy)5 were prepared as previously reported. Complexes
1ꢀ3 were also prepared as previously reported.10
6020
dx.doi.org/10.1021/ic1025679 |Inorg. Chem. 2011, 50, 6019–6028

Inorganic Chemistry
ARTICLE
Figure 1. Generic labeling scheme for 1H NMR signal assignments.
4-(5-Bromothiophen-2-yl)-6-[3-(trifluoromethyl)phenyl]-2,20-bipyridine
(P5). A mixture of 1-[2-oxo-2-[3-(trifluoromethyl)phenyl]ethyl]pyri-
dinium iodide59 (1.34 g, 3.40 mmol), (E)-3-(5-bromothiophen-2-yl)-
1-(pyridin-2-yl)prop-2-en-1-one60 (1.00 g, 3.40 mmol), and ammonium
acetate (6.81 g, 88.4 mmol) were refluxed in formamide (25 mL) for
14 h. The resulting heterogeneous solution was cooled to room tempe-
rature. The solid was removed by filtration, dried, and trituratured with
methanol (MeOH). The product was dried in vacuo to give 1.15 g (2.49
(0.15 mmol) were then added to the reaction solution, which was then
refluxed for 14 h under nitrogen. The reaction mixture was then cooled,
and the THF layer was washed with brine. The organic fractions were
isolated after being dried with MgSO4. The resultant oil was purified by
column chromatography and then triturated with MeOH to yield the
target ligand as a solid; specific details are given below.
N,N-Diphenyl-4-[5-[6-[3-(trifluoromethyl)phenyl]-2,20-bipyridin-4-
yl]thiophen-2-yl]aniline (L4H). Proligands: P1 and P5. Column chro-
matography: SiO2; CH2Cl2, Rf = 0.60. Yield: 853 mg (1.36 mmol,
81.6%); yellow-green solid. 1H NMR (400 MHz, CDCl3): δ 8.70 (ddd,
1H, 3J = 4.7 Hz, 4J = 1.6 Hz, 5J = 0.8 Hz, Ha), 8.59 (d, 1H, 4J = 1.6 Hz,
He), 8.57 (d, 1H, 3J = 7.9 Hz, Hd), 8.43 (s, 1H, Hn), 8.28 (d, 1H, 3J = 7.9
Hz, Hr), 7.83 (d, 1H, 4J = 1.6 Hz, Hm), 7.81 (dt, 1H, 3J = 7.7 Hz, 4J = 1.6
Hz, Hc), 7.68 (d, 1H, 3J = 7.9 Hz, Hp), 7.58 (t, 1H, 3J = 7.9 Hz, Hq), 7.57
(d, 1H, 3J = 3.9 Hz, Hf), 7.48 (d, 2H, 3J = 8.8 Hz, Hh), 7.33ꢀ7.25 (m, 5H,
1
mmol, 73.3%) of an off-white solid. H NMR (400 MHz, CDCl3): δ
8.69 (ddd, 1H, 3J = 4.8 Hz, 4J = 1.8 Hz, 5J = 1.0 Hz, Ha), 8.58 (ddd, 1H,
3J = 8.0 Hz, 4J = 1.0 Hz, 5J = 1.0 Hz, Hd), 8.55 (d, 1H, 4J = 1.6 Hz, He),
8.39 (s, 1H, Hn), 8.28 (d, 1H, 3J = 7.8 Hz, Hr), 7.86 (dt, 1H, 3J = 7.9, 4J =
1.8 Hz, Hc), 7.78 (d, 1H, 4J = 1.6 Hz, Hm), 7.69 (d, 1H, 3J = 7.8 Hz, Hp),
7.61 (t, 1H, 3J = 7.8 Hz, Hq), 7.44 (d, 1H, 3J = 3.9 Hz, Hf), 7.35 (ddd, 1H,
3J = 7.5 Hz, 3J = 4.8 Hz, 4J = 1.0 Hz, Hb), 7.11 (d, 1H, 3J = 3.9 Hz, Hg).
13C NMR (100 MHz, CDCl3): δ 156.9, 156.1, 155.7, 149.2, 143.0,
142.9, 140.0, 137.3, 131.5, 131.4 (q, 2JCF = 32.2 Hz), 130.4, 129.5, 126.3,
126.1 (q, 3JCF = 3.9 Hz), 124.5 (q, 1JCF = 272.5 Hz), 124.4, 124.1 (q,
3JCF = 3.9 Hz), 121.7, 116.4, 116.1, 114.7. HRMS (EI): m/z 461.9836
[(M)þ] (calcd for C21H12N2F3S81Brþ: m/z 461.9836).
3
3
Hb, Hk), 7.21 (d, 1H, J = 3.9 Hz, Hg), 7.14 (d, 4H, J = 9.0 Hz, Hj),
7.09ꢀ7.04 (m, 4H, Hi, Hl), 13C NMR (100 MHz, CDCl3): δ 156.8,
156.0, 155.8, 149.3, 148.1, 147.5, 146.5, 143.6, 140.3, 139.5, 137.1, 131.4
(q, 2JCF = 32.3 Hz), 130.4, 129.6, 129.5, 129.4, 127.7, 127.1, 126.8, 125.9
(q, 3JCF = 3.8 Hz), 125.0, 124.4 (q, 1JCF = 272.3 Hz), 124.2, 124.1 (q,
3JCF = 3.9 Hz), 123.6, 123.5, 121.6, 116.3, 116.0. HRMS (ESI): m/z
626.1875 [(MH)þ] (calcd for C39H27F3N3Sþ: m/z 626.1872).
4-(5-Bromothiophen-2-yl)-6-(3-methoxyphenyl)-2,20-bipyridine (P6).
A mixture of 1-[2-(3-methoxyphenyl)-2-oxoethyl]pyridinium iodide61
(1.81 g, 5.10 mmol), (E)-3-(5-bromothiophen-2-yl)-1-(pyridin-2-yl)-
prop-2-en-1-one60 (1.50 g, 5.10 mmol), and ammonium acetate (10.22
g, 133 mmol) were refluxed in formamide (25 mL) for 14 h. After the
resultant heterogeneous solution was cooled to room temperature, the
solid was removed by filtration, dried, and trituratured with MeOH. The
product was dried in vacuo to give 1.49 g (3.52 mmol, 69.0%) of an off-
white solid. 1H NMR (400 MHz, CDCl3): δ 8.69 (ddd, 1H, 3J = 4.8 Hz,
4J = 1.8 Hz, 5J = 1.0 Hz, Ha), 8.61 (ddd, 1H, 3J = 8.0 Hz, 4J = 1.0 Hz, 5J =
1.0 Hz, Hd), 8.51 (d, 1H, 4J = 1.6 Hz, He), 7.83 (dt, 1H, 3J = 7.8 Hz, 4J =
1.8 Hz, Hc), 7.78 (d, 1H, 4J = 1.6 Hz, Hm), 7.73 (t, 1H, 4J = 1.6 Hz, Hn),
7.68 (dd, 1H, 3J = 7.9 Hz, 4J = 1.6 Hz, Hr), 7.43 (d, 1H, 3J = 3.9 Hz, Hf),
7.42 (t, 1H, 3J = 7.9 Hz, Hq), 7.32 (ddd, 1H, 3J = 7.5 Hz, 3J = 4.8 Hz, 4J =
1.0 Hz, Hb), 7.10 (d, 1H, 3J = 3.9 Hz, Hg), 6.99 (ddd, 1H, 3J = 7.9 Hz, 4J =
1.8 Hz, 4J = 1.0 Hz, Hp), 3.91 (s, 3H, Ho). 13C NMR (100 MHz, CDCl3):
δ 160.3, 157.3, 156.7, 156.0, 149.2, 143.4, 142.5, 140.7, 137.1, 131.4,
129.9, 125.9, 124.2, 121.6, 119.6, 116.5, 115.5, 114.9, 114.3, 113.0, 55.6.
HRMS (EI): m/z 422.9981 [(M)þ] (calcd for C21H14N2OS81Brþ: m/z
422.9990).
4-Methyl-N-p-tolyl-N-[4-[5-[6-[3-(trifluoromethyl)phenyl]-2,20-bi-
pyridin-4-yl]thiophene-2-yl]phenyl]aniline (L5H). Proligands: P2 and
P5. Column chromatography: SiO2; CH2Cl2, Rf = 0.54. Yield: 734 mg
(1.12 mmol, 67.4%); yellow solid. 1H NMR (400 MHz, CDCl3): δ 8.71
(ddd, 1H, 3J = 4.7 Hz, 4J = 1.6 Hz, 5J = 0.8 Hz, Ha), 8.64 (d, 1H, 4J = 1.6
Hz, He), 8.61 (dt, 1H, 3J = 7.9 Hz, 4J = 1.0 Hz, Hd), 8.44 (s, 1H, Hn), 8.33
(d, 1H, 3J = 7.9 Hz, Hr), 7.91 (d, 1H, 4J = 1.6 Hz, Hm), 7.85 (dt, 1H, 3J =
7.7 Hz, 4J = 1.6 Hz, Hc), 7.70 (d, 1H, 3J = 7.9 Hz, Hp), 7.65 (d, 1H, 3J =
3.9 Hz, Hf), 7.62 (t, 1H, 3J = 7.9 Hz, Hq), 7.48 (d, 2H, 3J = 8.8 Hz, Hh),
7.35 (ddd, 1H, 3J = 7.5 Hz, 3J = 4.8 Hz, 4J = 1.0 Hz, Hb), 7.25 (d, 1H, 3J =
3.9 Hz, Hg), 7.08 (d, 4H, 3J = 8.2 Hz, Hk), 7.04ꢀ6.99 (m, 6H, Hi, Hj),
2.32 (s, 6H, Hl). 13C NMR (100 MHz, CDCl3): δ 156.7, 156.0, 155.8,
149.2, 148.5, 146.7, 145.0, 143.7, 140.3, 139.2, 137.2, 133.3, 131.3 (q,
2JCF = 32.3 Hz), 130.4, 130.2, 129.4, 127.1, 126.8, 126.7, 125.8 (q, 3JCF
=
3.8 Hz), 125.2, 124.5 (q, 1JCF = 272.3 Hz), 124.2, 124.1 (q, 3JCF = 3.9
Hz), 123.2, 122.2, 121.7, 116.2, 116.0, 21.1. HRMS (ESI): m/z 654.2184
[(MH)þ] (calcd for C41H31F3N3Sþ: m/z 654.2185).
4-Methoxy-N-(4-methoxyphenyl)-N-[4-[5-[6-[3-(trifluoromethyl)-
phenyl]-2,20-bipyridin-4-yl]thiophen-2-yl]phenyl]aniline (L6H). Proli-
gands: P3 and P5. Column chromatography: SiO2; CH2Cl2, Rf = 0.33.
Yield: 845 mg (1.23 mmol, 73.8%); yellow-orange solid. 1H NMR (400
MHz, CDCl3): δ 8.72 (ddd, 1H, 3J = 4.7 Hz, 4J = 1.6 Hz, 5J = 0.8 Hz, Ha),
General Preparation of Ligands L1HꢀL9H. Boronic esters
(P1ꢀP3; 1.67 mmol) and bromides (P4ꢀP6; 1.50 mmol) were solu-
bilized in a tetrahydrofuran (THF)/water solution (9:1; 130 mL) and
sparged for 10 min with nitrogen. K2CO3 (8.75 mmol) and Pd(PPh3)4
6021
dx.doi.org/10.1021/ic1025679 |Inorg. Chem. 2011, 50, 6019–6028

Inorganic Chemistry
ARTICLE
8.63 (d, 1H, 4J = 1.6 Hz, He), 8.61 (dt, 1H, 3J = 7.9 Hz, 4J = 1.0 Hz, Hd),
8.43 (s, 1H, Hn), 8.32 (d, 1H, 3J = 7.9 Hz, Hr), 7.89 (d, 1H, 4J = 1.6 Hz,
Hm), 7.86 (dt, 1H, 3J = 7.7 Hz, 4J = 1.6 Hz, Hc), 7.69 (d, 1H, 3J = 7.9 Hz,
Hp), 7.64 (d, 1H, 3J = 3.9 Hz, Hf), 7.62 (t, 1H, 3J = 7.9 Hz, Hq), 7.45 (d,
2H, 3J = 8.8 Hz, Hh), 7.34 (ddd, 1H, 3J = 7.5 Hz, 3J = 4.8 Hz, 4J = 1.0 Hz,
Hb), 7.21 (d, 1H, 3J = 3.9 Hz, Hg), 7.08 (d, 4H, 3J = 8.2 Hz, Hk), 6.92 (d,
General Preparation of Methyl Ester Complexes (1ꢀ10).
To a MeOH/H2O/THF solution (5:1:1, v/v/v, 280 mL) containing
0.40 mmol of the ligand (e.g., L1HꢀL9H and L12H) were added
0.4 mmol of Ru(L10)Cl3 and N-ethylmorpholine (0.5 mL). Following a
16-h reflux, AgNO3 (1.50 mmol) was added to the reaction mixture, and
the resulting mixture was then left to reflux for an additional 1.5 h. The
mixture was then cooled and preabsorbed on silica, and the solvent was
removed in vacuo. The product was purified by chromatographic
techniques (details specified below). The desired fraction was collected
and isolated to yield a dark red fine solid.
2H, 3J = 8.8 Hz, Hi), 6.84 (d, 4H, 3J = 8.2 Hz, Hj), 3.72 (s, 6H, Hl). 13
C
NMR (100 MHz, CDCl3): δ 156.7, 156.4, 156.0, 155.8, 149.2, 149.1,
147.0, 143.8, 140.6, 140.3, 138.9, 137.2, 131.4 (q, 2JCF = 32.3 Hz), 130.4,
3
129.4, 127.1, 127.0, 126.7, 125.9 (q, JCF = 3.8 Hz), 125.8, 124.5 (q,
1JCF = 272.3 Hz), 124.3, 124.1 (q, 3JCF = 3.9 Hz), 123.0, 121.7, 120.3,
116.3, 116.0, 115.0, 55.7. HRMS (ESI): m/z 686.2085 [(MH)þ] (calcd
for C41H31F3N3O2Sþ: m/z 686.2084).
[Ru(L4)(L10)]NO3 (4). Chromatographic conditions: SiO2; 9:1
1
CH2Cl2/MeOH; Rf = 0.59. Yield: 333 mg (0.28 mmol, 70.0%). H
NMR (400 MHz, CDCl3): δ 9.16 (s, 2H, HE), 9.05 (d, 1H, 3J = 1.4 Hz,
He), 9.02 (d, 1H, 3J = 7.3 Hz, Hd), 8.92 (d, 2H, 4J = 0.8 Hz, HD), 8.25 (d,
1H, 3J = 1.4 Hz, Hm), 8.22 (d, 1H, 3J = 3.9 Hz, Hf), 7.93 (s, 1H, Hn), 7.92
(dt, 1H, 3J = 7.5 Hz, 4J = 1.0 Hz, Hc), 7.70ꢀ7.63 (m, 4H, HA, HB), 7.58
(d, 2H, 3J = 8.9 Hz, Hh), 7.42 (d, 1H, 3J = 3.9 Hz, Hg), 7.31ꢀ7.24 (m, 5H,
Ha, Hk), 7.17ꢀ7.03 (m, 9H, Hb, Hi, Hj, Hl), 6.66 (d, 1H, 3J = 7.3 Hz, Hp),
5.53 (d, 1H, 3J = 7.6 Hz, Hq), 4.19 (s, 3H, HF), 3.94 (s, 6H, HC). HRMS
(ESI): m/z 1133.1901 [(M)þ] (calcd for C60H42F3N6O6RuSþ: m/z
4-[5-[6-(3-Methoxyphenyl)-2,20-bipyridin-4-yl]thiophen-2-yl]-N,N-
diphenylaniline (L7H). Proligands: P1 and P6. Column chromatogra-
phy: SiO2; CH2Cl2, Rf = 0.33. Yield: 724 mg (1.23 mmol, 74.2%);
1
yellow-orange solid. H NMR (400 MHz, CDCl3): δ 8.72 (ddd, 1H,
3J = 4.8 Hz, 4J = 1.8 Hz, 5J = 1.0 Hz, Ha), 8.64 (ddd, 1H, 3J = 8.0 Hz, 4J =
1.0 Hz, 5J = 1.0 Hz, Hd), 8.61 (d, 1H, 4J = 1.6 Hz, He), 7.90 (d, 1H, 4J =
1.6 Hz, Hm), 7.83 (dt, 1H, 3J = 7.7 Hz, 4J = 1.6 Hz, Hc), 7.78 (dd, 1H, 4J =
1.5 and 1.0 Hz, Hn), 7.73 (dt, 1H, 3J = 7.9 Hz, 4J = 1.6 Hz, Hr), 7.63 (d,
1H, 3J = 3.9 Hz, Hf), 7.51 (d, 2H, 3J = 8.9 Hz, Hh), 7.43 (t, 1H, 3J = 7.9
1133.1882). Anal. Calcd for C60H42F3N7O9RuS 2H2O: C, 58.53; H,
3
3.77; N, 7.96. Found: C, 58.18; H, 4.10; N, 7.58.
3
3
4
Hz, Hq), 7.32 (ddd, 1H, J = 7.5 Hz, J = 4.8 Hz, J = 1.0 Hz, Hb),
7.31ꢀ7.24 (m, 5H, Hk, Hg), 7.13 (d, 4H, 3J = 8.1 Hz, Hj), 7.10ꢀ7.04 (m,
4H, Hi, Hl), 7.00 (ddd, 1H, 3J = 7.9 Hz, 4J = 1.8 Hz, 4J = 1.0 Hz, Hp), 3.93
(s, 3H, Ho). 13C NMR (100 MHz, CDCl3): δ 160.3, 157.2, 156.5, 156.3,
149.2, 148.0, 147.6, 146.2, 143.4, 141.0, 139.9, 137.1, 135.3, 129.9, 129.6,
128.3, 127.9, 126.8, 124.9, 124.1, 123.6, 123.5, 121.7, 119.7, 116.5, 115.5,
114.8, 113.1, 55.6. HRMS (EI): m/z 587.2059 [(M)þ] (calcd for
C39H29N3OSþ: m/z 587.2031).
[Ru(L5)(L10)]NO3 (5). Chromatographic conditions: SiO2; 9:1
1
CH2Cl2/MeOH; Rf = 0.45. Yield: 334 mg (0.28 mmol, 70.4%). H
NMR (400 MHz, CDCl3): δ 9.16 (s, 2H, HE), 9.01 (d, 1H, 3J = 1.4 Hz,
He), 8.99 (d, 1H, 3J = 7.3 Hz, Hd), 8.92 (d, 2H, 4J = 0.8 Hz, HD), 8.24 (d,
1H, 3J = 1.4 Hz, Hm), 8.20 (d, 1H, 3J = 3.9 Hz, Hf), 7.96ꢀ7.88 (m, 2H,
Hn, Hc), 7.70ꢀ7.65 (m, 4H, HA, HB), 7.54 (d, 2H, 3J = 8.9 Hz, Hh), 7.39
(d, 1H, 3J = 3.9 Hz, Hg), 7.27 (d, 1H, 3J = 5.3 Hz, Ha), 7.09 (d, 4H, 3J =
8.3 Hz, Hk), 7.12ꢀ7.00 (m, 7H, Hb, Hi, Hj), 6.66 (d, 1H, 3J = 7.3 Hz,
Hp), 5.53 (d, 1H, 3J = 7.6 Hz, Hq), 4.19 (s, 3H, HF), 3.94 (s, 6H, HC),
2.32 (s, 6H, Hl). HRMS (ESI): m/z 1161.2210 [(M)þ] (calcd for
C62H46F3N6O6RuSþ: m/z 1161.2195). Anal. Calcd for C62H46F3N7-
4-[5-[6-(3-Methoxyphenyl)-2,20-bipyridin-4-yl]thiophen-2-yl]-N,N-
di-p-tolylaniline (L8H). Proligands: P2 and P6. Column chromatogra-
phy: SiO2; CH2Cl2, Rf = 0.21. Yield: 665 mg (1.08 mmol, 64.8%);
yellow-green solid. 1H NMR (400 MHz, CDCl3): δ 8.71 (dd, 1H, 3J =
4.8 Hz, 4J = 1.5 Hz, Ha), 8.63 (d, 1H, 3J = 7.5 Hz, Hd), 8.59 (d, 1H, 4J =
1.6 Hz, He), 7.89 (d, 1H, 4J = 1.6 Hz, Hm), 7.83 (dt, 1H, 3J = 7.7 Hz, 4J =
1.6 Hz, Hc), 7.78 (t, 1H, 4J = 1.0 Hz, Hn), 7.72 (d, 1H, 3J = 7.9 Hz, Hr),
7.63 (d, 1H, 3J = 3.9 Hz, Hf), 7.47 (d, 2H, 3J = 8.9 Hz, Hh), 7.43 (t, 1H,
3J = 7.9 Hz, Hq), 7.32 (ddd, 1H, 3J = 7.5 Hz, 3J = 4.8 Hz, 4J = 1.0 Hz, Hb),
7.22 (d, 1H, 3J = 3.9 Hz, Hg), 7.09 (d, 4H, 3J = 8.1 Hz, Hk), 7.05ꢀ6.98
(m, 7H, Hi, Hj, Hp), 3.92 (s, 3H, Ho), 2.32 (s, 6H, Hl). 13C NMR (100
MHz, CDCl3): δ 160.2, 157.2, 156.4, 156.3, 149.2, 148.4, 146.4, 145.1,
143.4, 141.0, 139.6, 137.0, 133.2, 130.2, 129.9, 126.9, 126.8, 126.7, 125.2,
124.0, 123.2, 122.3, 121.7, 119.7, 116.5, 115.5, 114.7, 113.0, 55.6, 21.0.
HRMS (ESI): m/z 616.2411 [(MH)þ] (calcd for C41H34N3OSþ: m/z
616.2417).
O9RuS 2H2O: C, 59.14; H, 4.00; N, 7.79. Found: C, 59.13; H, 4.06;
3
N, 7.55.
[Ru(L6)(L10)]NO3 (6). Chromatographic conditions: SiO2; 9:1
1
CH2Cl2/MeOH; Rf = 0.63. Yield: 306 mg (0.24 mmol, 61.2%). H
NMR (400 MHz, CDCl3): δ 9.15 (s, 2H, HE), 9.01 (d, 1H, 3J = 1.4 Hz,
He), 9.00 (d, 1H, 3J = 7.3 Hz, Hd), 8.92 (d, 2H, 4J = 0.8 Hz, HD), 8.24 (d,
1H, 3J = 1.4 Hz, Hm), 8.21 (d, 1H, 3J = 3.9 Hz, Hf), 7.97ꢀ7.88 (m, 2H,
Hn, Hc), 7.70ꢀ7.63 (m, 4H, HA, HB), 7.52 (d, 2H, 3J = 8.9 Hz, Hh), 7.38
(d, 1H, 3J = 3.9 Hz, Hg), 7.27 (d, 1H, 3J = 5.3 Hz, Ha), 7.12ꢀ7.06 (m, 5H,
Hk, Hb), 6.95 (d, 2H, 3J = 8.9 Hz, Hi), 6.85 (d, 4H, 3J = 8.2 Hz, Hj), 6.66
(d, 1H, 3J = 7.3 Hz, Hp), 5.53 (d, 1H, 3J = 7.6 Hz, Hq), 4.19 (s, 3H, HF),
3.94 (s, 6H, HC), 3.80 (s, 6H, Hl). HRMS (ESI): m/z 1193.2114 [(M)þ]
(calcd for C62H46F3N6O8RuSþ: m/z 1193.2093). Anal. Calcd for
4-Methoxy-N-(4-methoxyphenyl)-N-[4-[5-[6-(3-methoxyphenyl)-
2,20-bipyridin-4-yl]thiophen-2-yl]phenyl]aniline (L9H). Proligands: P3
and P6. Column chromatography: SiO2; CH2Cl2, Rf = 0.12. Yield: 735
mg (1.13 mmol, 68.0%); orange solid. 1H NMR (400 MHz, CDCl3): δ
8.71 (dd, 1H, 3J = 4.8 Hz, 4J = 1.5 Hz, Ha), 8.63 (d, 1H, 3J = 7.5 Hz, Hd),
8.59 (d, 1H, 4J = 1.6 Hz, He), 7.89 (d, 1H, 4J = 1.6 Hz, Hm), 7.83 (dt,
1H, 3J = 7.7 Hz, 4J = 1.6 Hz, Hc), 7.77 (dd, 1H, 4J = 1.5 and 1.0 Hz, Hn),
7.72 (dt, 1H, 3J = 7.9 Hz, 4J = 1.6 Hz, Hr), 7.63 (d, 1H, 3J = 3.9 Hz, Hf),
7.45 (d, 2H, 3J = 8.9 Hz, Hh), 7.42 (t, 1H, 3J = 7.9 Hz, Hq), 7.32 (ddd,
1H, 3J = 7.5 Hz, 3J = 4.8 Hz, 4J = 1.0 Hz, Hb), 7.21 (d, 1H, 3J = 3.9 Hz,
Hg), 7.08 (d, 4H, 3J = 8.1 Hz, Hk), 6.99 (ddd, 1H, 3J = 7.9 Hz, 4J = 1.8
Hz, 4J = 1.0 Hz, Hp), 7.08 (d, 2H, 3J = 8.8 Hz, Hi), 7.08 (d, 4H, 3J = 8.1
Hz, Hj), 3.92 (s, 3H, Ho), 3.79 (s, 6H, Hl). 13C NMR (100 MHz,
CDCl3): δ 160.3, 157.2, 156.5, 156.4, 149.2, 149.0, 146.6, 143.4, 141.1,
140.7, 139.4, 137.0, 129.9, 127.1, 126.8, 126.7, 125.9, 124.1, 122.9,
121.7, 120.4, 119.7, 116.5, 115.4, 115.2, 115.0, 114.7, 113.0, 55.7, 55.6.
HRMS (ESI): m/z 648.2323 [(M)þ] (calcd for C41H34N3O3Sþ: m/z
648.2315).
C62H46F3N7O11RuS 2H2O: C, 57.67; H, 3.90; N, 7.59. Found: C,
57.85; H, 4.19; N, 7.27.
3
[Ru(L7)(L10)]NO3 (7). Chromatographic conditions: SiO2; 9:1
1
CH2Cl2/MeOH; Rf = 0.56. Yield: 254 mg (0.22 mmol, 55.2%). H
NMR (400 MHz, CDCl3): δ 9.10 (s, 2H, HE), 8.92 (d, 1H, 3J = 7.3 Hz,
Hd), 8.89 (d, 1H, 3J = 1.4 Hz, He), 8.87 (d, 2H, 4J = 0.8 Hz, HD), 8.27 (d,
1H, 3J = 1.4 Hz, Hm), 8.17 (d, 1H, 3J = 3.9 Hz, Hf), 7.90 (dt, 1H, 3J = 7.6
Hz, 4J = 1.0 Hz, Hc), 7.67 (d, 2H, 3J = 5.4 Hz, HA), 7.61 (dd, 2H, 3J = 5.4
Hz, 4J = 1.0 Hz, HB), 7.55 (d, 2H, 3J = 8.9 Hz, Hh), 7.54 (d, 1H, 3J = 7.8
3
3
Hz, Hn), 7.40 (d, 1H, J = 3.9 Hz, Hg), 7.28 (t, 4H, J = 8.3 Hz, Hk),
7.17ꢀ7.00 (m, 9H, Hj, Hb, Hi, Hl), 6.92 (d, 1H, 3J = 5.3 Hz, Ha), 6.81 (t,
1H, 3J = 7.8 Hz, Ho), 5.97 (d, 1H, 3J = 7.8 Hz, Hp), 4.19 (s, 3H, HF), 3.94
(s, 6H, HC), 2.74 (s, 3H, Hq). HRMS (ESI): m/z 1095.2125 [(M)þ]
(calcd for C60H45N6O7RuSþ: m/z 1095.2114). Anal. Calcd for
C60H45N7O10RuS 2H2O: C, 60.40; H, 4.14; N, 8.22. Found: C,
3
60.68; H, 4.24; N, 7.83.
[Ru(L8)(L10)]NO3 (8). Chromatographic conditions: SiO2;9:1CH2Cl2/
MeOH; Rf = 0.61. Yield: 313 mg (0.26 mmol, 66.4%). 1H NMR (400 MHz,
6022
dx.doi.org/10.1021/ic1025679 |Inorg. Chem. 2011, 50, 6019–6028

Inorganic Chemistry
ARTICLE
CDCl3): δ 9.10 (s, 2H, HE), 8.90 (d, 1H, 3J = 7.3 Hz, Hd), 8.87 (m, 3H,
He, HD), 8.27 (d, 1H, 3J = 1.4 Hz, Hm), 8.16 (d, 1H, 3J = 3.9 Hz, Hf), 7.91
(dt, 1H, 3J = 7.6 Hz, 4J = 1.0 Hz, Hc), 7.66 (d, 2H, 3J = 5.4 Hz, HA), 7.61
(dd, 2H, 3J = 5.4 Hz, 4J = 1.0 Hz, HB), 7.54 (d, 1H, 3J = 7.8 Hz, Hn), 7.51
(d, 2H, 3J = 8.9 Hz, Hh), 7.38 (d, 1H, 3J = 3.9 Hz, Hg), 7.09 (d, 4H, 3J =
8.3 Hz, Hk), 7.06ꢀ7.00 (m, 7H, Hj, Hb, Hi), 6.93 (d, 1H, 3J = 5.3 Hz, Ha),
6.81 (t, 1H, 3J = 7.8 Hz, Ho), 5.97 (d, 1H, 3J = 7.8 Hz, Hp), 4.19 (s, 3H,
HF), 3.94 (s, 6H, HC), 2.74 (s, 3H, Hq), 2.32 (s, 6H, Hl). HRMS (ESI):
m/z 1123.2434 [(M)þ] (calcd for C62H49N6O7RuSþ: m/z 1123.2427).
and a 6-31G* basis set was used for C, H, N, P, and Cl atoms.67 Time-
dependent density functional theory (TDDFT) calculations were also
performed using this methodology, and the first 60 singlet excited states
were calculated. Calculations by the first-principles method were used to
obtain accurate excitation energies and oscillator strengths. We modeled
the solvent with the polarizable continuum model using MeOH as the
solvent.68,69
’ RESULTS AND DISCUSSION
Anal. Calcd for C62H49N7O10RuS 2H2O: C, 60.98; H, 4.37; N, 8.03.
3
Found: C, 60.76; H, 4.51; N, 7.69.
Synthesis and Structural Characterization. A modular
synthetic approach (Scheme 1) was used to isolate the library
of TPA-functionalized tridentate ligands in Chart 1. The synth-
esis of each of these donor ligands was achieved in reasonably
high yield on a large scale utilizing well-established synthetic
methods. Proligands P4ꢀP6 were synthesized through Kr€ohnke
condensations to yield the bromothiophene-substituted pbpy
platform, which were further reacted with Suzuki reagents
(e.g., P1ꢀP3) to give the desired ligands, L1HꢀL9H, in high
yields.
[Ru(L9)(L10)]NO3 (9). Chromatographic conditions: SiO2;9:1CH2Cl2/
MeOH; Rf = 0.58. Yield: 356 mg (0.29 mmol, 73.5%). 1H NMR
(400 MHz, CDCl3): δ 9.10 (s, 2H, HE), 8.87 (s, 2H, HD), 8.86 (d,
1H, 3J = 7.3 Hz, Hd), 8.83 (d, 1H, 3J = 1.4 Hz, He), 8.26 (d, 1H, 3J = 1.4
Hz, Hm), 8.13 (d, 1H, 3J = 3.9 Hz, Hf), 7.90 (dt, 1H, 3J = 7.6 Hz, 4J = 1.0
Hz, Hc), 7.66 (d, 2H, 3J = 5.4 Hz, HA), 7.61 (dd, 2H, 3J = 5.4 Hz, 4J = 1.0
Hz, HB), 7.54 (d, 1H, 3J = 7.8 Hz, Hn), 7.48 (d, 2H, 3J = 8.9 Hz, Hh), 7.35
(d, 1H, 3J = 3.9 Hz, Hg), 7.09 (d, 4H, 3J = 8.3 Hz, Hk), 7.03 (dt, 1H, 3J =
7.6 Hz, 4J = 1.0 Hz, Hb), 6.93 (d, 3H, 3J = 8.9 Hz, Hi, Ha), 6.85 (d, 4H, 3J =
8.2 Hz, Hj), 6.80 (t, 1H, 3J = 7.8 Hz, Ho), 5.97 (d, 1H, 3J = 7.8 Hz, Hp),
4.19 (s, 3H, HF), 3.94 (s, 6H, HC), 3.79 (s, 6H, Hl), 2.74 (s, 3H, Hq).
HRMS (ESI): m/z 1155.2327 [(M)þ] (calcd for C62H49N6O9RuSþ:
Following previously established synthetic routes,5,10 the
syntheses of the cyclometalated complexes were achieved
through reaction of the Ru(L10)Cl3 synthon with the corre-
sponding ligand, producing the methyl ester complexes (1ꢀ9) in
high yields ranging between 55 and 70% after chromatographic
purification to remove the byproduct (Scheme S1 in the Sup-
porting Information). The structural identities of all ligands and
complexes were confirmed by a combination of NMR spectros-
m/z 1155.2325). Anal. Calcd for C62H49N7O12RuS 2H2O: C, 59.42; H,
3
4.26; N, 7.82. Found: C, 59.03; H, 4.39; N, 7.44.
[Ru(pbpy)(L10)]NO3 (10). Chromatographic conditions: SiO2; 9:1
1
CH2Cl2/MeOH; Rf = 0.50. Yield: 148 mg (0.19 mmol, 46.4%). H
NMR (400 MHz, CDCl3): δ 9.13 (s, 2H, HE), 8.90 (s, 2H, HD), 8.74 (d,
1H, 3J = 8.0 Hz, He), 8.70 (d, 1H, 3J = 8.0 Hz, Hd), 8.23 (t, 1H, 3J = 8.0
Hz, Hs), 8.14 (d, 1H, 3J = 8.0 Hz, Hm), 7.90 (dt, 1H, 3J = 8.0 Hz, 4J = 1.2
Hz, Hc), 7.70 (d, 1H, 3J = 7.6 Hz, Ha), 7.67ꢀ7.63 (m, 4H, HA, HB), 7.17
(d, 1H, 3J = 4.8 Hz, Hn), 7.03 (t, 1H, 3J = 7.2 Hz, Hb), 6.74 (t, 1H, 3J = 7.6
Hz, Hp), 6.44 (t, 1H, 3J = 7.8 Hz, Ho), 5.33 (d, 1H, 3J = 7.2 Hz, Hq), 4.19
(s, 3H, HF), 3.94 (s, 6H, HC). HRMS (ESI): m/z 740.1087 [(M)þ]
(calcd for C37H28N5O6Ruþ: m/z 740.1083). Anal. Calcd for C37H28-
1
copy, mass spectrometry, and/or EA. H NMR (1D and 2D)
spectroscopy is a particularly effective diagnostic tool for these
complexes because of separation of the aromatic signals and the
inherent asymmetry of the complexes. A collection of represen-
tative 1H NMR spectra are provided in Figure 2 to illustrate the
effect of substitution on the anionic ring of the pbpy chelate with
EWGs or EDGs (e.g., 2, 5, and 8). A signature of cyclometalation
of the TPA-substituted pbpy ligand is the upfield shift of the
signal corresponding to the proton ortho to the RuꢀC bond (i.e.,
Hq) that arises because of the proximity of the anionic carbon.
This signal is observed for compounds with either ꢀH (e.g., 2) or
ꢀCF3 (e.g., 5) on the anionic ring (Figure 2). The electron-
withdrawing nature of the ꢀCF3 group is revealed in the down-
field chemical shift of the proton ortho to the RuꢀC bond, Hq, of
5 (Hq = 5.53 ppm) relative to the ꢀH-substituted analogue 2
(Hq = 5.35 ppm). Curiously, the most-upfield signal in the aromatic
region for ꢀOMe-substituted complex 8 is not Hq but is instead
a doublet corresponding to the resonance signal of the proton
meta to the RuꢀC bond, Hp, at 5.97 ppm. This signature
provides direct evidence that the ꢀOMe group appears at
the R3 position (i.e., ortho to the RuꢀC bond) rather than at
the R2 position (vide infra). Because the position of the
substituent on the phenyl ring of the pbpy chelate is found
to fluctuate in the series (i.e., at either R2 or R3), Hn emerges as
a better spectroscopic handle to probe the electronic effects of
substitution for this particular series. In this regard, the
chemical shift of Hp follows the expected trend of electron
density on the anionic ring, e.g., 2 (6.47 ppm), 5 (6.66 ppm),
and 8 (5.97 ppm).
N6O9Ru H2O: C, 54.21; H, 3.69; N, 10.25. Found: C, 54.56; H, 3.92;
3
N, 9.88.
Physical Methods. Elemental analysis (EA), electrospray ioniza-
tion mass spectrometry (ESI-MS), matrix-assisted laser desorption/
ionization mass spectrometry (MALDI-TOF), and electron impact (EI)
mass spectrometry data were collected at the Chemistry Instrumenta-
tion Facility of the University of Calgary. Electrochemical measurements
were performed under anaerobic conditions with a Princeton Applied
Research VersaStat 3 potentiostat using dry solvents, platinum working
and counter electrodes, a silver pseudoreference electrode, and a 0.1 M
NBu4BF4 supporting electrolyte. Electronic spectroscopic data were
collected on MeOH solutions using a Cary 5000 UVꢀvis spectro-
photometer (Varian). Steady-state emission spectra were obtained at
room temperature using an Edinburgh Instruments FLS920 spectro-
meter equipped with a Xe900 450-W steady-state xenon arc lamp, a
TMS300-X excitation monochromator, a TMS300-M emission mono-
chromator, and a Hamamatsu R2658P PMT detector and corrected for
detector response. Lifetime measurements were obtained at room
temperature using an Edinburgh Instruments FLS920 spectrometer
equipped with a Fianium SC400 super continuum white light source and
a Hamamatsu R3809U-50 multichannel plate detector, and data were
analyzed with Edinbrugh Instruments F900 software. Curve fitting of the
data was performed using a nonlinear least-squares procedure in the
F900 software.
CꢀH activation takes place para to the substituent on the
anionic ring for the complexes bearing ꢀCF3 substituents
anionic (e.g., 5). Taking into account the electron-withdrawing
character of the ꢀCF3 group, it is not remarkable that the CꢀH
bond para to the substituent is activated to form the RuꢀC bond.
Computational Methods. The Gaussian 03 computational
package62 to perform ground-state geometry optimization calculations
employing Becke’s three-parameter hybrid exchange functional, the
LeeꢀYangꢀParr non-local correlation functional B3LYP,63,64 and SDD
basis set65,66 with an effective core potential, was used for the Ru atom
6023
dx.doi.org/10.1021/ic1025679 |Inorg. Chem. 2011, 50, 6019–6028

Inorganic Chemistry
ARTICLE
Scheme 1. Synthesis of Precursors P4ꢀP6 and Ligands L1HꢀL9Ha
a Reaction conditions: (a) ammonium acetate, formamide, 120 °C, 14 h; (b) Pd(PPh3)4, K2CO3, THF/H2O (9:1); 65 °C, 14 h.
We anticipated that the ꢀOMe substituent would also appear
para to the RuꢀC bond due to steric considerations; however,
the CꢀH activation step is found to occur ortho to the ꢀOMe
group. It appears that this anomaly is a result of the more
thermodynamically stable isomer being the favored product.
This hypothesis is corroborated by electrochemical data that
indicate that this isomer is more stable by ∼130 mV (vide infra).
Electrochemical Data. The electrochemical properties of the
free ligands and the corresponding metal complexes were
examined in CH2Cl2 by cyclic voltammetry. Relevant redox
values are collected in Table 1. The redox properties of similar
TPA-substituted ligands have been discussed previously.10,48 In
brief, there is a single quasi-reversible one-electron oxidation
ox
(E1/2 = þ0.98ꢀ1.22 V) localized to the TPA portion of the
ligand (i.e., TPA•þ/TPA0). The position of this oxidation wave
remains static after coordination to the ruthenium metal
(Figure 3); however, it is sensitive to the solvent medium (e.g.,
the TPA•þ/TPA0 oxidation potential is shifted ∼ꢀ70 mV in MeCN).
An anodic sweep of each of the solutions containing the
cyclometalated complexes typically produces two consecutive
quasi-reversible single-electron oxidation processes that corre-
spond to oxidation of the TPA unit and ruthenium(II) metal; the
differences in Ep,a and Ep,c (i.e., ΔE) are provided in Table 1. The
careful assignment of the oxidative behavior was aided by
references to previously reported compounds;10 however, in
certain cases, differential pulse voltammetry (DPV) was required
to resolve the closely spaced oxidation processes (e.g., 1, 2, 7, and
8). As stated above, the TPA•þ/TPA0 oxidation potential is not
affected by ligation to the {Ru(L10)} core, nor is it affected by
substitution of the pbpy chelate; i.e., the oxidation potential is the
same for the free ligand and complex [e.g., ∼þ1.2 V for L1H and
1, ∼þ1.1 V for L5H and 5 (Figure 3), and ∼þ1.0 V for L9H and
9]. Similarly, the RuIII/RuII redox couple is not affected by
substitution of TPA at R1 (e.g., þ1.17 V for 1ꢀ3, respectively).
With installation of the ꢀCF3 group at the R2 position, the RuIII/
RuII redox couple resides at þ1.27 V, which is þ100 and þ170 mV
greater than the cases where R2 = ꢀH and R3 = ꢀOMe, respecti-
vely. Note that a ꢀOMe substitutent para to the RuꢀC bond can
Figure 2. 1H NMR spectra for CDCl3 solutions of 5, 2, and 8 at
ambient temperatures highlighting how substituents affect the elec-
tron density on the anionic ring. Color scheme: green, Hq; red, Hs;
blue, Hp; purple, Hn.
6024
dx.doi.org/10.1021/ic1025679 |Inorg. Chem. 2011, 50, 6019–6028

Inorganic Chemistry
ARTICLE
Table 1. Summary of the Spectroscopic and Electrochemical Properties for Ligands L1HꢀL9H and Complexes 1ꢀ10
emission datab
E1/2, V vs NHEd
compound
UVꢀvis absorbance data:a λmax, nm (ε ꢁ 103, Mꢀ1 cmꢀ1
)
λem, nm
τ, ns;c ϕ
RuIII/RuII
TPA•þ/TPA0
3
e
L1H
1
391 (26.7)
536 (390)
549 (429)
563 (397)
561 (433)
3.4 (0.99); 0.91
3.2 (1.02); 0.27
3.8 (1.04); 0.58
3.6 (1.00); 0.24
1.20
1.21 (75) f
681sh (3.4), 584sh, 526 (26.7), 431 (39.4), 330 (42.4)
1.17 (72) f
e
L2H
2
399 (31.2)
1.10
681sh (3.5), 584sh, 526 (28.4), 435 (39.3), 330 (42.5)
404 (33.2)
681sh (2.9), 574sh, 527 (29.6), 437 (37.5), 331 (41.0)
1.17 (87) g
e
1.11 (89) g
0.99
L3H
3
616 (401)
0.6 (0.91); 0.16
e
e
1.17 (86)
e
0.99 (89)
L4H
4
420 (23.8)
545 (391)
3.3 (0.94); 0.81
1.20
664sh (4.0), 572sh, 517 (33.0), 427 (43.1), 328 (50.7)
402 (29.0)
666sh (4.2), 571sh, 518 (37.6), 430 (44.1), 329 (54.3)
1.27 (91) h
e
1.19 (92) h
1.11
e
e
L5H
5
573 (419)
3.4 (1.06); 0.52
e
e
1.27 (80)
e
1.10 (78)
0.99
L6H
6
408 (25.0)
632 (403)
0.5 (0.97); 0.34
666sh (4.1), 571sh, 520 (39.1), 431 (41.5), 330 (52.6)
391 (28.4)
664sh (4.3), 571sh, 531 (29.1), 433 (45.9), 329 (51.2)
1.27 (93)
e
0.98 (96)
1.20
e
e
L7H
7
535 (387)
2.9 (0.96); 0.55
e
e
1.11 (76)
e
1.20 (74)
1.10
L8H
8
399 (31.2)
563 (396)
4.0 (1.09); 0.82
667sh (4.0), 571sh, 532 (29.2), 437 (43.4), 330 (48.6)
404 (33.5)
668sh (4.2), 571sh, 532 (32.8), 439 (44.9), 330 (50.8)
684sh (3.0), 574sh, 523 (9.7), 433 (17.0), 329 (29.6)
1.09 (77)
e
1.09 (77)
0.98
e
e
L9H
621 (401)
e; 0.18
e
e
9
10i
1.10 (88)
1.12
0.98 (90)
e
e
e
a Data collected in MeOH. b Data collected in MeCN; λex values indicated in parentheses with units of nm. χ2 indicated in parentheses; absolute
quantum yield measured with an integrating sphere. d Data collected using 0.1 M NBu4BF4/CH2Cl2 solutions at 100 mV/s and referenced to a
[Fc]/[Fc]þ or [OFc]/[OFc]þ internal standard followed by conversion to NHE; [Fc]/[Fcþ] = þ765 mV vs NHE in CH2Cl2; [OFc]/[OFc]þ = þ290
c
e
mV vs NHE in CH2Cl2; values in parentheses are the ΔE values of Ep,a and Ep,cg given in mV determined from DPV experiments. Not observed.
f Oxidative sweep in DPV experiments produces two peaks resolved by 40 mV. Oxidative sweep generates two peaks resolved by 60 mV in DPV
experiments. h Oxidative sweep generates two peaks resolved by 80 mV in DPV experiments. Benchmark complex: [Ru(pbpy)(L10)](NO3).
i
Superscript “sh” indicates shoulder.
lower the RuIII/RuII oxidation potential by ca. ∼200 mV;28 thus,
the observation that this couple is only affected by ∼70 mV is
primarily attributed to the ꢀOMe substituent being positioned
ortho to the RuꢀC bond. The stabilizing effect of this EDG
ortho to the organometallic bond (rather than para) is rationa-
lized by the suppressed donating ability of the O-atom lone-pair
into the aromatic ring due to hindered steric rotation about the
CꢀOMe bond.
Figure 4b reveals a slightly more pronounced effect on the optical
properties when the pbpy chelate is modified. The position of the
lowest-energy maxima reflects a higher metal-based HOMO level
(involving the dxy orbital) with progressively greater electron
density on the anionic ring; e.g., λmax follows the trend 8 (532 nm)
> 2 (526 nm) > 5 (518 nm). This trend is also consistent with the
lowest-energy absorption band containing a significant MLCT
contribution emanating from the occupied dxy orbital to the π*
orbital of the L10 ligand (vide infra). There are, however, ILCT
contributions within the low-energy band, as evidenced by the
slightly lower shoulder at ca. 570 nm that becomes more
prominent with substituents on the pbpy chelate. In the case of
5, for example, there appears to be an enhancement of the
transition dipole for the ILCT transition furnished by the elec-
tron-deficient CF3-substituted pbpy chelate (i.e., from πTPA f π*
of the pbpy chelate). Consequently, the most intense low-energy
band is observed for 5, followed by 2 and 3, respectively.
DFT. Ground-state optimization and TDDFT calculations
were performed to aid the assignment of the optical spectra. The
four major predicted transitions and the corresponding molec-
ular orbital diagrams are shown for 1 in Figure 5. The lowest-
energy transition, λ1, involves a transition from the HOMOꢀ1
orbital containing significant Ru dxy character to the LUMO,
which contains π*-orbital character over the Me3tctpy ligand. We
note that the shoulder may also have some contribution from the
direct population of a 3MLCT state facilitated by the heavy-metal
ion.70 The transition λ2 at 599 nm contains two transitions of
approximately equal weight (i.e., HOMOꢀ1 f LUMOþ1 and
Optical Properties. Electronic absorption and emission data
were collected to delineate the effects of substitution at the R1
and R2/R3 positions (Table 1). Each of the free TPA-substituted
ligands displays a relatively broad intense absorption band
centered within the 390ꢀ420 nm range (Figure S2 in the
Supporting Information) that arises from a series of intramole-
cular π f π* transitions emanating from the TPA fragment to
the π* system of the pbpy fragment. Ligation to the metal center
renders a broad and intense absorption envelope for each of the
complexes due to multiple intraligand charge-transfer (ILCT)
and metal-to-ligand charge-transfer (MLCT) transitions (Figure 4).
A general assignment of the principle electronic transitions for
the title complexes is made possible by the extensive library of
related compounds available to us within this study as well as our
prior work.10 The optical spectra for 1ꢀ3 in Figure 4a show that
there are negligible changes in the intensities and positions of the
absorption spectra when different substituents are installed at the
R1 position. The slight increase in the extinction coefficient at
∼540 nm for complex 3 is ascribed to a higher transition dipole
induced by the electron-rich ꢀOMe substituent on the TPA unit.
6025
dx.doi.org/10.1021/ic1025679 |Inorg. Chem. 2011, 50, 6019–6028

Inorganic Chemistry
ARTICLE
HOMOꢀ2 f LUMO). The orbital character for the HOMOꢀ2
is distributed over the Ru dxz orbital and the π system extending
over the thiophene spacer and TPA; the LUMO and LUMOþ1
orbitals are both localized over the π* system of the anchoring
Me3tctpy ligand. The orbital character for the HOMOꢀ3 orbital,
which is involved in λ4, is primarily Ru dyz in character, with some
minor contributions from the π system of the anionic portion of
the cyclometalating ring and the Me3tctpy ligand. The spectral
analysis for 2ꢀ9 is provided as Supporting Information (Figures
S3ꢀS10). In general, the first three low-energy transitions
(λ1ꢀλ3) involve the promotion of electrons from molecular
orbitals localized over TPA and/or the ruthenium metal and
anionic ring to the π* system of the Me3tctpy ligand. The highest-
energy transition (i.e., λ4) involves a filled orbital with character
that is either localized to the TPA or over the dyz orbital. We note
that all four light-induced transitions λ1ꢀλ4 involve the move-
ment of electron density toward Me3tctpy, which is ideal for
sensitization applications.
The predicted UVꢀvis spectra match well with the experi-
mental spectra; indeed, the oscillator strengths of the calculated
transitions match well with the molar extinction coefficients
derived from experiment. One curious result, however, is the
prediction that the HOMO resides on the TPA in all cases. This
finding contrasts the electrochemical data, which clearly indicate
that thefirst oxidation potential is not always TPA-based (e.g., 1 and
7). We ascribe this discrepancy to solvation of the TPA unit: the
oxidation potential of the TPA•þ/TPA0 couple can shift to more
positive values in polar solvents (e.g, a ∼ꢀ70 mV shift when the
solvent is switched from CH2Cl2 to MeCN). Thus, in the
absence of an appropriate solvation model for the TPA unit,
we anticipate the predicted thermodynamic position of the
HOMO localized to TPA to be shifted to more negative
values.
’ SUMMARY
The primary objective of this synthetic endeavor is to develop
a series of complexes where a direct correlation of the properties
to the molecular structure could be established to guide the
design of cyclometalated complexes for light-harvesting applica-
tions. Building on our previous studies,10,48 we have expanded
the development of the dual-chromophore scaffold, [Ru(TPA-
pbpy)(Me3tctpy)], to show that we can systematically tune the
electrochemical behavior of both the ruthenium and TPA units.
We show that the electronic properties of each electrophore can
be manipulated to make the RuIII/RuII couple more or less
oxidizing than the TPA unit. This feature is possible because the
ground-state oxidation potentials of the each unit can be
modulated over a wide range of potentials: ΔE1/2 = 180 and
230 mV for the RuIII/RuII and TPA•þ/TPA couples, respec-
tively. Consequently, the HOMO character can be positioned on
either the metal chelate or the TPA unit, with the latter scenario
being optimal for sensitizing TiO2.10,47,51
Figure 3. Cyclic voltammograms for ligand L5H and the corresponding
metal complex 5 in CH2Cl2 at ambient temperatures (scan rate =
100 mV/s). Dashed lines emphasize that Ep,a and Ep,c of the TPA•þ/TPA0
couple are the same as those for the free ligand and complex.
Figure 4. UVꢀvis absorption spectra demonstrating the (a) minor optical changes when R1 = ꢀH (1), ꢀMe (2), and ꢀOMe (3) and (b) the more
significant optical response to substituents at the pbpy chelate (e.g., 2, R2/R3 = ꢀH; 5, R2 = ꢀCF3, R3 = ꢀH; 8, R2 = ꢀH, R3 = ꢀOMe). The spectrum of
N3 is also provided as a benchmark.
6026
dx.doi.org/10.1021/ic1025679 |Inorg. Chem. 2011, 50, 6019–6028

Inorganic Chemistry
ARTICLE
and ligands L1HꢀL9H in MeOH, a synthetic scheme for
1
compounds 1ꢀ9, comparative H NMR spectra for 2, 5, and
8, and molecular orbital pictures and TDDFT spectra for 2ꢀ9.
This material is available free of charge via the Internet at http://
pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: cberling@ucalgary.ca.
’ ACKNOWLEDGMENT
This work was financially supported by the Canadian Natural
Science and Engineering Research Council (NSERC), Canada
Research Chairs, Canadian Foundation for Innovation (CFI),
Alberta Ingenuity, and the Canada School of Energy and
Environment (CSEE). We are also grateful to NSERC (K.C.D.
R., B.S., and E.S.), Alberta Innovates (K.C.D.R.), and DI-26-10/I,
AT24100024, and CONICYT (E.S.) for student fellowships.
Figure 5. Experimental UVꢀvis absorption spectrum of 1 overlaid with
calculated transitions represented by vertical bars (only the transitions
with contributions >40% are shown). Details of calculated transitions
(theoretical wavelength in nm, oscillator strength, % contribution to the
transition): λ1, HOMOꢀ1 f LUMO (709, 0.027, 85%); λ2, HOMOꢀ
2 f LUMO (594, 0.11, 50%) and HOMOꢀ1 f LUMOþ1 (594, 0.11,
40%); λ3, HOMOꢀ2 f LUMOþ1 (536, 0.11, 85%); λ4, HOMOꢀ3 f
LUMOþ2 (447, 0.38, 64%).
’ REFERENCES
(1) O’Regan, B.; Gr€atzel, M. Nature 1991, 353, 737–740.
(2) Hagfeldt, A.; Boschloo, G.; Sun, L.; Kloo, L.; Pettersson, H.
Chem. Rev. 2010, 110, 6595–6663.
In contrast to the rich electrochemical behavior, the relative
positions of the two redox units are found to have negligible effects
on the optical properties: substitution at both the R1 and R2/R3
positions produces minor changes in both the intensities and shapes
of the absorbance profiles. This finding stands in stark contrast to
the significant spectral changes that occur when the position of the
organometallic bond in this platform is varied.10 Notwithstanding,
the differences in the optical spectra, however slight, remain con-
sistent with the dipole changes—and relative weighting—for both
the ILCT and MLCT transitions and harvest a significant amount of
light out to 800 nm (note that the optical profiles are superior to that
of N3; Figure 4). Thus, the ability to control the redox properties
without affecting the optical properties provides a distinct advantage
for inducing an electronic cascade and the thermodynamic driving
force for the reaction between the electrolyte and photooxidized
dye. Transient spectroscopic studies are underway to further unravel
the electron-transfer events that occur after light absorption.
This work adds further evidence that bichromic cyclometa-
lated ruthenium(II) complexes offer a number of benefits over
tridentate polypyridylruthenium(II) compounds for sensitizing
TiO2. Distortion of the ligand field by the anionic cyclometalat-
ing ligands leads to a broad absorption envelope while increasing
the π* orbital of the LUMO, which will presumably lead to
enhanced rates of electron injection into the TiO2 anode.71 The
incorporation of a secondary chromophore is shown to increase
the intensity of the absorption bands substantially compared to
analogous tridentate cyclometalated derivatives.28 Moreover,
previous studies have shown that the TPA unit can increase
the excited-state lifetime of the ruthenium chromophore and
spatial charge separation on TiO2.47,50,52,72 The device perfor-
mance for this entire suite of complexes in liquid-junction and
solid-state DSSCs will be disseminated in a future study.
(3) Wadman, S. H.; Kroon, J. M.; Bakker, K.; Lutz, M.; Spek, A. L.;
van Klink, G. P. M.; van Koten, G. Chem. Commun. 2007, 1907–1909.
(4) Bessho, T.; Yoneda, E.; Yum, J.-H.; Guglielmi, M.; Tavernelli, I.;
Imai, H.; Rothlisberger, U.; Nazeeruddin, M. K.; Gr€atzel, M. J. Am.
Chem. Soc. 2009, 131, 5930–5934.
(5) Bomben, P. G.; Robson, K. C. D.; Sedach, P. A.; Berlinguette,
C. P. Inorg. Chem. 2009, 48, 9631–9643.
(6) Funaki, T.; Yanagida, M.; Onozawa-Komatsuzaki, N.; Kasuga,
K.; Kawanishi, Y.; Kurashige, M.; Sayama, K.; Sugihara, H. Inorg. Chem.
Commun. 2009, 12, 842–845.
(7) Bomben, P. G.; Thꢀeriault, K. D.; Berlinguette, C. P. Eur. J. Inorg.
Chem. 2011, 2011, 1806–1814.
(8) Nazeeruddin, M. K.; Kay, A.; Rodicio, I.; Humphry-Baker, R.;
M€ueller, E.; Liska, P.; Vlachopoulos, N.; Gr€atzel, M. J. Am. Chem. Soc.
1993, 115, 6382–6390.
(9) Asghar, M. I.; Miettunen, K.; Halme, J.; Vahermaa, P.; Toivola,
M.; Aitola, K.; Lund, P. Energy Environ. Sci. 2010, 3, 418–426.
(10) Robson, K. C. D.; Sporinova, B.; Koivisto, B. D.; Baumgartner,
T.; Yella, A.; Nazeeruddin, K. M.; Gr€atzel, M.; Berlinguette, C. P. Inorg.
Chem. 2011 50, 5494–5508.
(11) Dixon, I. M.; Alary, F.; Heully, J.-L. Dalton Trans. 2010,
39, 10959–10966.
(12) Jacko, A. C.; McKenzie, R. H.; Powell, B. J. J. Mater. Chem.
2010, 20, 10301–10307.
(13) J€ager, M.; Smeigh, A.; Lombeck, F.; G€orls, H.; Collin, J.-P.;
Sauvage, J.-P.; Hammarstr€om, L.; Johansson, O. Inorg. Chem. 2010,
49, 374–376.
(14) Wadman, S. H.; Kroon, J. M.; Bakker, K.; Havenith, R. W. A.;
van Klink, G. P. M.; van Koten, G. Organometallics 2010, 29, 1569–1579.
(15) Wadman, S. H.; Lutz, M.; Tooke, D. M.; Spek, A. L.; Hartl, F.;
Havenith, R. W. A.; van Klink, G. P. M.; van Koten, G. Inorg. Chem. 2009,
48, 1887–1900.
(16) Wu, K.-L.; Hsu, H.-C.; Chen, K.; Chi, Y.; Chung, M.-W.; Liu,
W.-H.; Chou, P.-T. Chem. Commun. 2010, 46, 5124–5126.
(17) Collin, J. P.; Kayhanian, R.; Sauvage, J. P.; Calogero, G.;
Barigelletti, F.; DeCian, A.; Fischer, J. Chem. Commun. 1997, 775–776.
(18) Alonso-Vante, N.; Nierengarten, J.-F.; Sauvage, J.-P. J. Chem.
Soc., Dalton Trans. 1994, 1649–1654.
’ ASSOCIATED CONTENT
S
Supporting Information. UVꢀvis absorption spectra
(19) Beley, M.; Chodorowski, S.; Collin, J.-P.; Sauvage, J.-P.;
Flamigni, L.; Barigelletti, F. Inorg. Chem. 1994, 33, 2543–2547.
b
highlighting the optical affects of the position of the RuꢀC bond
6027
dx.doi.org/10.1021/ic1025679 |Inorg. Chem. 2011, 50, 6019–6028

Inorganic Chemistry
ARTICLE
(20) Barigelletti, F.; Flamigni, L.; Guardigli, M.; Juris, A.; Beley, M.;
Chodorowski-Kimmes, S.; Collin, J.-P.; Sauvage, J.-P. Inorg. Chem. 1996,
35, 136–142.
(21) B€orgstrom, M.; Ott, S.; Lomoth, R.; Bergquist, J.;
Hammarstr€om, L.; Johansson, O. Inorg. Chem. 2006, 45, 4820–4829.
(22) Ott, S.; Borgstr€om, M.; Hammarstr€om, L.; Johansson, O.
Dalton Trans 2006, 1434–1443.
(23) Dixon, I. M.; Collin, J. P. J. Porphyrins Phthalocyanines 2001,
5, 600–607.
(24) Yam, V. W.-W.; Chu, B. W.-K.; Ko, C. C.; Cheung, K. K.
J. Chem. Soc., Dalton Trans. 2001, 1911–1919.
(52) Karthikeyan, C. S.; Wietasch, H.; Thelakkat, M. Adv. Mater.
2007, 19, 1091–1095.
(53) Argazzi, R.; Bignozzi, C. A.; Heimer, T. A.; Castellano, F. N.;
Meyer, G. J. J. Am. Chem. Soc. 1995, 117, 11815–11816.
(54) Argazzi, R.; Bignozzi, C. A.; Heimer, T. A.; Castellano, F. N.;
Meyer, G. J. J. Phys. Chem. C 1997, 101, 2591–2597.
(55) Nazeeruddin, M. K.; Pꢀechy, P.; Renouard, T.; Zakeeruddin,
S. M.; Humphry-Baker, R.; Comtꢀe, P.; Liska, P.; Cevey, L.; Costa, E.;
Shklover, V.; Spiccia, L.; Deacon, G. B.; Bignozzi, C. A.; Gr€atzel, M.
J. Am. Chem. Soc. 2001, 123, 1613–1624.
(56) Medina, A.; Claessens, C. G.; Rahman, G. M. A.; Lamsabhi,
A. M.; Mo, O.; Yanez, M.; Guldi, D. M.; Torres, T. Chem. Commun.
2008, 1759–1761.
(25) Maestri, M.; Balzani, V.; Deuschel-Cornioley, C.; Von Zelewsky,
A. Adv. Photochem. 1992, 17, 1–68.
(26) Djukic, J. P.; Sortais, J. B.; Barloy, L.; Pfeffer, M. Eur. J. Inorg.
Chem. 2009, 817–853.
(57) Anemian, R.; Cupertino, D. C.; Mackie, P. R.; Yeates, S. G.
Tetrahedron Lett. 2005, 46, 6717–6721.
(27) Constable, E. C.; Housecroft, C. E. Polyhedron 1990, 9, 1939–
1947.
(28) Koivisto, B. D.; Robson, K. C. D.; Berlinguette, C. P. Inorg.
(58) Amthor, S.; Lambert, C. J. Phys. Chem. A 2006, 110, 1177–1189.
(59) Ash, A. B.; Blumbergs, P.; Markovac, A.; La Montagne, M. P.
U.S. Patent 3,7631,488, 1973.
Chem. 2009, 48, 9644–9652.
(29) Yao, C.-J.; Sui, L.-Z.; Xie, H.-Y.; Xiao, W.-J.; Zhong, Y.-W.; Yao,
J. Inorg. Chem. 2010, 49, 8347–8350.
(60) Zhao, L.-X.; Kim, T. S.; Ahn, S.-H.; Kim, T.-H.; Kim, E.-k.; Cho,
W.-J.; Choi, H.; Lee, C.-S.; Kim, J.-A.; Jeong, T. C.; Chang, C.-j.; Lee,
E.-S. Bioorg. Med. Chem. Lett. 2001, 11, 2659–2662.
(30) Guillon, T.; Boggio-Pasqua, M.; Alary, F.; Heully, J.-L.; Lebon,
E.; Sutra, P.; Igau, A. Inorg. Chem. 2010, 49, 8862–8872.
(31) Moorlag, C.; Sarkar, B.; Sanrame, C. N.; B€auerle, P.; Kaim, W.;
Wolf, M. O. Inorg. Chem. 2006, 45, 7044–7046.
(32) Sun, Y.; El Ojaimi, M.; Hammitt, R.; Thummel, R. P.; Turro, C.
J. Phys. Chem. B 2010, 114, 14664–14670.
(33) Ardo, S.; Meyer, G. J. Chem. Soc. Rev. 2009, 38, 115–164.
(34) Durrant, J. R.; Haque, S. A.; Palomares, E. Coord. Chem. Rev.
2004, 248, 1247–1257.
(35) Kuciauskas, D.; Monat, J. E.; Villahermosa, R.; Gray, H. B.;
Lewis, N. S.; McCusker, J. K. J. Phys. Chem. B 2002, 106, 9347–9358.
(36) Bomben, P. G.; Koivisto, B. D.; Berlinguette, C. P. Inorg. Chem.
2010, 49, 4960–4971.
(37) Robertson, N. Angew. Chem., Int. Ed. 2006, 45, 2338–2345.
(38) Garcia, C. G.; De Lima, J. F.; Iha, N. Y. M. Coord. Chem. Rev.
2000, 196, 219–247.
(39) Gao, F. F.; Wang, Y.; Zhang, J.; Shi, D.; Wang, M. K.; Humphry-
Baker, R.; Wang, P.; Zakeeruddin, S. M.; Gr€atzel, M. Chem. Commun.
2008, 2635–2637.
(40) Yum, J.-H.; Jung, I.; Baik, C.; Ko, J.; Nazeeruddin, M. K.;
Gr€atzel, M. Energy Environ. Sci. 2009, 2, 100–102.
(41) Wang, P.; Klein, C.; Humphry-Baker, R.; Zakeeruddin, S. M.;
Gr€atzel, M. J. Am. Chem. Soc. 2005, 127, 808–809.
(42) Chen, B.-S.; Chen, K.; Hong, Y.-H.; Liu, W.-H.; Li, T.-H.; Lai,
C.-H.; Chou, P.-T.; Chi, Y.; Lee, G.-H. Chem. Commun. 2009, 5844–5846.
(43) Zeng, W.; Cao, Y.; Bai, Y.; Wang, Y.; Shi, Y.; Zhang, M.; Wang,
F.; Pan, C.; Wang, P. Chem. Mater. 2010, 22, 1915–1925.
(44) Mishra, A.; Fischer, M. K. R.; B€auerle, P. Angew. Chem., Int. Ed.
2009, 48, 2474–2499.
(61) Sasaki, I.; Vendier, L.; Sournia-Saquet, A.; Lacroix, P. G. Eur. J.
Inorg. Chem. 2006, 3294–3302.
(62) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.;
Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.;
Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson,
G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.;
Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.;
Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.;
Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.;
Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski,
V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick,
D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui,
Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith,
T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.;
Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.;
Pople, J. A. Gaussian 03; Gaussian, Inc.: Wallingford, CT, 2004.
(63) Becke, A. D. Phys. Rev. A: Gen. Phys. 1988, 38, 3098–3100.
(64) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B: Condens. Matter
1988, 37, 785–789.
(65) Dolg, M.; Stoll, H.; Preuss, H. Theor. Chem. Acc. 1993, 85, 441–
450.
(66) Wedig, M. D.; Stoll, H. Quantum Chemistry: The Challenge of
Transition Metals and Coordination Chemistry; Kluwer Academic Pub-
lishers: Dordrecht, Holland, 1986.
(67) Rassolov, V. A.; Ratner, M. A.; Pople, J. A.; Redfern, P. C.;
Curtiss, L. A. J. Comput. Chem. 2001, 22, 976–984.
(45) Marinado, T.; Nonomura, K.; Nissfolk, J.; Karlsson, M. K.;
Hagberg, D. P.; Sun, L. C.; Mori, S.; Hagfeldt, A. Langmuir 2010,
26, 2592–2598.
(68) Barone, V.; Cossi, M.; Tomasi, J. J. Chem. Phys. 1997, 107,
3210–3221.
(69) Cossi, M.; Scalmani, G.; Rega, N.; Barone, V. J. Chem. Phys.
(46) Hagberg, D. P.; Marinado, T.; Karlsson, K. M.; Nonomura, K.;
Qin, P.; Boschloo, G.; Brinck, T.; Hagfeldt, A.; Sun, L. J. Org. Chem.
2007, 72, 9550–9556.
2002, 117, 43–54.
(70) Flamigni, L.; Barbieri, A.; Sabatini, C.; Ventura, B.; Barigelletti,
F. Top. Curr. Chem. 2007, 281, 143–203.
(47) Bonh^ote, P.; Moser, J.-E.; Humphry-Baker, R.; Vlachopoulos,
N.; Zakeeruddin, S. M.; Walder, L.; Gr€atzel, M. J. Am. Chem. Soc. 1999,
121, 1324–1336.
(48) Robson, K. C. D.; Koivisto, B. D.; Gordon, T. J.; Baumgartner,
T.; Berlinguette, C. P. Inorg. Chem. 2010, 49, 5335–5337.
(49) Abrahamsson, M.; Wolpher, H.; Johansson, O.; Larsson, J.;
Kritikos, M.; Eriksson, L.; Norrby, P.-O.; Bergquist, J.; Sun, L.; Aker-
mark, B.; Hammarstr€om, L. Inorg. Chem. 2005, 44, 3215–3225.
(50) Handa, S.; Wietasch, H.; Thelakkat, M.; Durrant, J. R.; Haque,
S. A. Chem. Commun. 2007, 1725–1727.
(71) Koops, S. E.; O’Regan, B. C.; Barnes, P. R. F.; Durrant, J. R.
J. Am. Chem. Soc. 2009, 131, 4808–4818.
(72) Karthikeyan, C. S.; Peter, K.; Wietasch, H.; Thelakkat, M. Sol.
Energy Mater. Sol. Cells 2007, 91, 432–439.
(51) Haque, S. A.; Handa, S.; Peter, K.; Palomares, E.; Thelakkat, M.;
Durrant, J. R. Angew. Chem., Int. Ed. 2005, 44, 5740–5744.
6028
dx.doi.org/10.1021/ic1025679 |Inorg. Chem. 2011, 50, 6019–6028