A High Molar Extinction Coefficient Bisterpyridyl Homoleptic Ru(II) Complex with trans-2-Methyl-2-butenoic Acid Functionality: Potential Dye for Dye-Sensitized Solar Cells
In our continued efforts in the synthesis of ruthenium(II) polypyridine complexes as potential dyes for use in varied applications, such as the dye-sensitized solar cells (DSSCs), this work particularly describes the synthesis, absorption spectrum, redox behavior and luminescence properties of a new homoleptic ruthenium(II) complex bearing a simple trans-2-methyl-2-butenoic acid functionality as the anchoring ligand on terpyridine moiety. The functionalized terpyridine ligand: 4’-( trans-2-methyl-2-butenoic acid)-terpyridyl (L1) was synthesized by aryl bromide substitution on terpyridine in a basic reaction condition under palladium carbide catalysis. In particular, the photophysical and redox properties of the complex formulated as: bis-4’-( trans-2-methyl-2-butenoic acid)-terpyridyl ruthenium(II) bis-hexafluorophosphate [Ru(L1) 2(PF 6) 2] are significantly better compared to those of [Ru(tpy) 2] 2+ and compare well with those of the best emitters of Ru(II) polypyridine family containing tridentate ligands. Reasons for the improved photophysical and redox properties of the complex may be attributed partly to the presence of a substituted α,β-unsaturated carboxylic acid moiety leading to increase in the length of π-conjugation bond thereby enhancing the MLCT-MC (Metal-to-ligand-charge transfer-metal centred) energy gap, and to the reduced difference between the minima of the excited and ground states potential energy surfaces.
References
[1]
O’Regan, B.; Gratzel, M. A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films. Nature 1991, 353, 737–740.
[2]
Hagfeldt, A.; Gratzel, M. Light-induced redox reactions in nanocrystalline systems. Chem. Rev 1995, 95, 49–68.
Park, H.; Bae, E.; Lee, J.-J.; Park, J.; Choi, W. Effect of the anchoring group in Ru-bipyridyl sensitizers on the photoelectrochemical behaviour of dye-sensitized TiO2 electrodes: Carboxylate versus Phosphonate linkages. J. Phys. Chem. B 2006, 110, 8740–8749.
[5]
Zaban, A.; Ferrrere, S.; Sprague, J.; Gregg, B.A. pH-dependent redox potential induced in a sensitizing dye by adsorption onto TiO2. J. Phys. Chem. B 1997, 101, 55–57.
Pichot, F.; Gregg, B.A. The photovoltage-determining mechanism in dye-sensitized solar cells. J. Phys. Chem. B 2000, 104, 6–10.
[8]
Fallapour, R.A. Photochemical and thermal reactions of azido-oligopyridines: Diazepinones, a new class of metal-complex ligands. Helv. Chim. Acta 2000, 83, 384–393.
Argazzi, R.; Bignozzi, C.A.; Heimer, T.A.; Meyer, G.J. Remote electron injection from supramolecular sensitizers. Inorg. Chem 1997, 36, 2–3.
[11]
Wolpher, H.; Sinha, S.; Pan, J.; Johansson, A.; Lundqvist, M.J.; Persson, P.; Lomoth, R.; Bergquist, J.; Sun, L.; Sundstrolm, V.; et al. Synthesis and electron transfer studies of ruthenium-terpyridine-based dyads attached to nanostructured TiO2. Inorg. Chem 2007, 46, 638–651.
[12]
Asbury, J.B.; Ellingson, R.J.; Ghosh, H.N.; Ferrere, S.; Nozik, A.J.; Lian, T. Femtosecond IR study of excited-state relaxation and electron-injection dynamics of [Ru(dcbpy)2(NCS)2] in solution and on nanocrystalline TiO2 and Al2O3 thin films. J. Phys. Chem. B 1999, 103, 3110–3119.
[13]
Winter, C.; Sizman, R.; Vant Hull, L. Solar Power Plants; Springer-Verlag: New York, NY, USA, 1991; Volume Chapter 2.
[14]
Nazeeruddin, M.K.; Pechy, P.; Renouard, T.; Zakeeruddin, S.M.; Humphry-Baker, R.; Comte, P.; Liska, P.; Cevey, L.; Costa, E.; Shklover, V.; et al. Engineering of efficient panchromatic sensitizers for nanocrystalline TiO2-based solar cells. J. Am. Chem. Soc 2001, 123, 1613–1624.
Meyer, T.J. Photochemistry of metal coordination complexes: Metal to ligand charge transfer excited states. Pure Appl. Chem 1986, 58, 1193–1206.
[17]
Meyer, T.J; Huynh, M.H.V. The remarkable reactivity of high oxidation state ruthenium and osmium polypyridyl complexes. Inorg. Chem 2003, 42, 8140–8160.
[18]
Bonnet, S.; Collin, J.P.; Sauvage, J.P. Synthesis and photochemistry of a two-position Ru(terpy)(phen)(L)2+ scorpionate complex. Inorg. Chem 2006, 45, 4024–4034.
[19]
Karidi, K.; Garoufis, A.; Tsipis, A.; Hadjiliadis, N.; Dulk, H.; Reedijk, J.J. Synthesis, characterization, in-vitro antitumor activity, DNA-binding properties and electronic structure (DFT) of the new complex cis-(Cl, Cl)[RuIICl2(NO+)(terpy)]Cl. Chem. Soc. Dalton Trans 2005, 1176–1187.
Treadway, J.A.; Loeb, B.; Lopez, R.; Anderson, P.A.; Keene, F.R.; Meyer, T.J. Effect of delocalization and rigidity in the acceptor ligand on MLCT excited-state decay. Inorg. Chem 1996, 35, 2242–2246.
[22]
Nazeeruddin, M.K.; Kay, A.; Rodicio, I.; Humphry-Baker, R.; Muller, E.; Liska, P.; Vlachopoulos, N.; Gratzel, M. Conversion of light to electricity by cis-X2(dcbpy)2Ru(II) CT sensitizers on nanocrystalline TiO2 electrodes. J. Am. Chem. Soc 1993, 115, 6382–6390.
Treadway, J.A.; Moss, J.A.; Meyer, T.J. Visible region photooxidation on TiO2 with a chromophore-catalyst molecular assembly. Inorg. Chem 1999, 38, 4386–4387.
[25]
Zakeeruddin, S.M.; Nazeeruddin, M.K.; Humphry-Baker, R.; Gratzel, M.; Shklover, V. Stepwise assembly of tris-heteroleptic polypyridyl complexes of ruthenium(II). Inorg. Chem 1998, 37, 5251–5259.
[26]
Adeloye, A.O.; Ajibade, P.A. A high molar extinction coefficient mono-anthracenyl bipyridyl heteroleptic ruthenium(II) complex: Synthesis, photophysical and electrochemical properties. Molecules 2011, 16, 4615–4631.
[27]
Adeloye, A.O.; Ajibade, P.A. Synthesis, characterization and preliminary investigation of the electroredox properties of anthracenyl-functionalized terpyridyl ligands. Tetrahedron Lett 2011, 52, 274–277.
[28]
Adeloye, A.O. Synthesis, photophysical and electrochemical properties of a mixed-bipyridyl-phenanthrolyl ligand Ru(II) heteroleptic complex having trans-2-Methyl-2-butenoic acid functionalities. Molecules 2011, 16, 8353–8367.
[29]
Duffy, N.W.; Dobson, K.D.; Gordon, K.C.; Robinson, B.H.; McQuillan, A.J. In situ infrared spectroscopic analysis of the adsorption of ruthenium(II) bipyridyl dicarboxylic acid photosensitizers to TiO2 in aqueous solutions. Chem. Phys. Lett 1997, 266, 451–455.
[30]
Coates, J. Interpretation of infrared spectra, a practical approach. In Encyclopedia of Analytical Chemistry; Meyers, R.A., Ed.; John Wiley & Sons Ltd: Chichester, UK, 2000; pp. 10815–10837.
[31]
Nazeeruddin, M.K.; Kay, A.; Rodicio, I.; Humphry-Baker, R.; Muller, E.; Liska, P.; Vlachopoulos, N.; Gratzel, M. Conversion of light to electricity by cis-X2(dcbpy)2Ru(II) CT sensitizers on nanocrystalline TiO2 electrodes. J. Am. Chem. Soc 1993, 115, 6382–6390.
[32]
Fang, Y.Q.; Taylor, N.J.; Laverdiere, F.; Hanan, G.S.; Loiseau, F.; Nastasi, F.; Campagna, S.; Nierengarten, H.; Leize-Wagner, E.; van Dorsselae, A. Ruthenium(II) complexes with improved photophysical properties base on planar 4′-(2-Pyrimidinyl)-2,2′,6′,2″-terpyridine ligands. Inorg. Chem 2007, 46, 2854–2863.
Sauvage, J.P.; Collin, J.P.; Chambron, J.C.; Guillerez, S.; Coudret, C.; Balzani, V.; Barigelletti, F.; de Cola, L.; Flamigni, L. Ruthenium(II) and Osmium(II) bis(terpyridine) complexes in covalently-linked multicomponent systems: Synthesis, electrochemical behavior, absorption spectra, and photochemical and photophysical properties. Chem. Rev 1994, 94, 993–1019.
[35]
Beres, J.E.; Constable, E.C.; Housecroft, C.E.; Neuburger, M.; Schaffner, S. A pyrazolyl-terminated 2,2′:6′,2″-terpyridine ligand: Iron(II), Ruthenium(II) and Palladium(II) complexes of 4′-(3,5-dimethylpyrazol-1-yl)-2,2′:6′,2″-terpyridine. Polyhedron 2008, 27, 2395–2401.
[36]
Kawanishi, Y.; Kitamura, N.; Tazuke, S. Dependence of spectroscopic, electrochemical, and excited-state properties of tris-chelate ruthenium(II) complexes on ligand structure. Inorg. Chem 1989, 28, 2968–2975.
Strouse, G.F.; Schoonover, J.R.; Duesing, R.; Boyde, S.; Jones, W.E.; Meyer, T.J. Influence of electronic delocalization in metal to ligand charge transfer excited states. Inorg. Chem 1995, 34, 473–487.
Wacholtz, W.F.; Aeurbach, R.A.; Schmehl, R.H. Independent control charge transfer and metal centered excited states in mixed ligand polypyridine ruthenium(II) complexes via specific ligand design. Inorg. Chem 1986, 25, 227–234.
[41]
Anderson, P.A.; Strouse, G.F.; Treadway, J.A.; Keene, F.R.; Meyer, T.J. Black MLCT absorbers. Inorg. Chem 1994, 33, 3863–3864.
[42]
Kalyanasundaram, K.; Nazeeruddin, M.K.; Gratzel, M.; Viscardi, G.; Savarino, P.; Barni, E. Synthesis and photophysical characterization of highly luminescent complexes of ruthenium(II) containing 4,4′-di (p-carboxyphenyl)-2,2′-bipyridine. Inorg. Chem. Acta 1992, 198–200, 831–839.
[43]
Demas, J.N.; Harris, E.W.; McBride, R.P.J. Energy transfer from luminescent transition metal complexes to oxygen. J. Am. Chem. Soc 1977, 99, 3547–3551.
[44]
Wolfgang, S.; Gafney, H.D. Quenching of Ru(bpy)3 2+ ionically bound to porous Vycor glass by O2, N2O and SO2. J. Phys. Chem 1983, 87, 5395–5401.
[45]
Vyas, P.; Bhatt, A.K.; Ramachandraiah, G.; Bedekar, A.V. Environmentally benign chlorination and bromination of aromatic amines, hydrocarbons and naphthols. Tetrahedron Lett 2003, 44, 4085–4088.
[46]
Evans, I.P.; Spencer, A.; Wilkinson, G. Dichlorotetrakis(dimethyl sulphoxide) ruthenium(II) and its use as a source material for some new Ruthenium(II) complexes. J. Chem. Soc. Dalton Trans 1973, doi:10.1039/DT9730000204.
[47]
Mitsopoulou, C.A.; Veroni, I.; Philippopoulos, A.I.; Falaras, P. Synthesis, characterization and sensitization properties of two novel mono and bis carboxyl-dipyrido-phenazine ruthenium(II) charge transfer complexes. J. Photochem. Photobiol. A 2007, 191, 6–12.
