title: Evolution of linear absorption and nonlinear optical properties in V-shaped ruthenium(II)-based chromophores.
abstract: In this article, we describe a series of complexes with electron-rich cis-{Ru(II)(NH(3))(4)}(2+) centers coordinated to two pyridyl ligands bearing N-methyl/arylpyridinium electron-acceptor groups. These V-shaped dipolar species are new, extended members of a class of chromophores first reported by us (Coe, B. J. et al. J. Am. Chem. Soc. 2005, 127, 4845-4859). They have been isolated as their PF(6)(-) salts and characterized by using various techniques including (1)H NMR and electronic absorption spectroscopies and cyclic voltammetry. Reversible Ru(III/II) waves show that the new complexes are potentially redox-switchable chromophores. Single crystal X-ray structures have been obtained for four complex salts; three of these crystallize noncentrosymmetrically, but with the individual molecular dipoles aligned largely antiparallel. Very large molecular first hyperpolarizabilities beta have been determined by using hyper-Rayleigh scattering (HRS) with an 800 nm laser and also via Stark (electroabsorption) spectroscopic studies on the intense, visible d --> pi* metal-to-ligand charge-transfer (MLCT) and pi --> pi* intraligand charge-transfer (ILCT) bands. The latter measurements afford total nonresonant beta(0) responses as high as ca. 600 x 10(-30) esu. These pseudo-C(2v) chromophores show two substantial components of the beta tensor, beta(zzz) and beta(zyy), although the relative significance of these varies with the physical method applied. According to HRS, beta(zzz) dominates in all cases, whereas the Stark analyses indicate that beta(zyy) is dominant in the shorter chromophores, but beta(zzz) and beta(zyy) are similar for the extended species. In contrast, finite field calculations predict that beta(zyy) is always the major component. Time-dependent density functional theory calculations predict increasing ILCT character for the nominally MLCT transitions and accompanying blue-shifts of the visible absorptions, as the ligand pi-systems are extended. Such unusual behavior has also been observed with related 1D complexes (Coe, B. J. et al. J. Am. Chem. Soc. 2004, 126, 3880-3891).
authors.affiliation: School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK. b.coe@manchester.ac.uk
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Coe
authors.forename: Simon P
authors.initials: SP
authors.lastname: Foxon
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Harper
authors.forename: Madeleine
authors.initials: M
authors.lastname: Helliwell
authors.forename: James
authors.initials: J
authors.lastname: Raftery
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Swanson
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Brunschwig
authors.forename: Koen
authors.initials: K
authors.lastname: Clays
authors.forename: Edith
authors.initials: E
authors.lastname: Franz
authors.forename: Javier
authors.initials: J
authors.lastname: Garín
authors.forename: Jesús
authors.initials: J
authors.lastname: Orduna
authors.forename: Peter N
authors.initials: PN
authors.lastname: Horton
authors.forename: Michael B
authors.initials: MB
authors.lastname: Hursthouse
mesh_terms: D000641:Ammonia / Q000737:chemistry; D004396:Coloring Agents / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011725:Pyridines / Q000737:chemistry; D011789:Quantum Theory; D017975:Ruthenium Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D013053:Spectrophotometry; D013237:Stereoisomerism
chemical_list: D004396:Coloring Agents; D011725:Pyridines; D017975:Ruthenium Compounds; D000641:Ammonia; C023666:pyridine