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 6salts 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 β 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 f π* metal-to-ligand charge-transfer (MLCT) and π f π* intraligand charge-transfer (ILCT) bands. The latter measurements afford total nonresonant β 0 responses as high as ca. 600 × 10 -30 esu. These pseudo-C 2v chromophores show two substantial components of the β tensor, β zzz and β zyy , although the relative significance of these varies with the physical method applied. According to HRS, β zzz dominates in all cases, whereas the Stark analyses indicate that β zyy is dominant in the shorter chromophores, but β zzz and β zyy are similar for the extended species. In contrast, finite field calculations predict that β 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 π-systems are extended. Such unusual behavior has also been observed with related 1D complexes (Coe, B. J. et al.
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