Article

All-trans-ClRuII(py)4(NC)RuII(py)4(CN)RuII(py)4(NO)(PF6)4: A Redox-Active 2-Donor/1-Acceptor System Based on the Electrophilic RuNO6 Motif

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Inorganic Chemistry, 48 (2): 565--573 (2009)
DOI: 10.1021/ic801347d

Abstract

The new linear homotrinuclear compd. trans-ClRuII(py)4(NC)RuII(py)4(CN)RuII(py)4(NO)(PF6)4 was prepd. by reaction between the nitro complex trans-(NC)RuII(py)4(CN)RuII(py)4(NO2)+ and the solvento complex obtained by reaction between ClRuII(py)4(NO)3+ and N3- in acetone. The trans-ClRuII(py)4(NC)RuII(py)4(CN)RuII(py)4(NO)4+ ion (I) was characterized by 1H NMR and IR spectroscopy (nNO = 1919 cm-1). This species displays intense electronic absorptions in the visible region which can be assigned to donor-acceptor charge-transfer transitions (DACT) involving RuNO6-centered acceptor orbitals and donor orbitals located on the 2 different neighboring metal centers at $\sim$6.7 and 12.6 \AA distance from the metal in the RuNO6 fragment. Addn. of OH- to I generated the nitro complex with a 2nd-order rate const. of (12.5 $\pm$ 0.2) $\times$ 103 M-1 s-1 (25°). Cyclic voltammetry expts. complemented by spectroelectrochem. in the UV-visible-NIR region reveal that I can be reversibly reduced at 0.49 or 0.20 V vs. AgCl/Ag for MeCN and H2O, resp., and oxidized at 0.71 or 0.57 V vs. AgCl/Ag. The spectroscopic and spectroelectrochem. information (UV-visible-NIR, X-band EPR) supplemented with electronic structure computation (DFT) reveals that the 1-electron redn. is centered on the nitrosyl moiety to yield a RuNO7 species, while oxidn. occurs on the chlororuthenium side of the mol. Both processes yield significant changes of the electronic spectra which are discussed in parallel with the electronic structure picture as obtained by DFT. on SciFinder(R)

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