Coupled states in dinitrofluorene: relationships between ground state and excited state mixed valence.

The electronic absorption spectrum of 9,9-dimethyl-2,7-dinitrofluorene radical anion in HMPA displays both a NIR intervalence charge transfer and a visible excited state mixed valence transition. These transitions contain a similar vibronic progression resulting from molecular orbitals that are common to both transitions. Vibrational frequency and intensity data are acquired from the resonance Raman spectrum and used to calculate a best fit for the absorption spectrum. The normal coordinate distortions are analyzed in terms of the electronic changes for both transitions to explain their similarity. The Raman scattering intensity decreases at lower excitation wavelength as a result of Raman de-enhancement caused by interference between neighboring excited states.

Characterization of an iron-ruthenium interaction in a ferrocene diamide complex.

Reaction of [fc(NH2)2]RuCl2(PPh3)2 (fc = 1,1'-ferrocenylene) with 2 equiv of KO(t)Bu led to the formation of a diamido ruthenium complex, [fc(NH)2]Ru(PPh3)2, whose solid-state molecular structure revealed a short Fe-Ru distance. A metal-to-metal charge transfer band was observed in the electronic absorption spectrum of [fc(NH)2]Ru(PPh3)2. The Fe-Ru interaction was characterized by resonance Raman spectroscopy for the first time and also by (1)H NMR, UV-vis, NIR, Mössbauer spectroscopy, and X-ray crystallography. Density functional theory (DFT) calculations including natural bond order analysis, Bader's atom in molecules method, and time-dependent DFT (TDDFT) provided further support that the iron-ruthenium bond is a weak donor-acceptor interaction with iron acting as the Lewis base.

Isolation of a radical dianion of nitrogen oxide (NO)(2-).

Nitric oxide, NO, the diatomic hybrid of dinitrogen and dioxygen, has extensive biochemical, industrial and atmospheric chemistry. The unpaired electron on NO makes it highly reactive and its facile oxidation and reduction to make (NO)(1+) and (NO)(1-), respectively, have been heavily studied. Now the (NO)(2-) dianion has been isolated for the first time from the two-electron reduction of NO by the recently discovered (N(2))(3-) yttrium complex {[(Me(3)Si)(2)N](2)(THF)Y}(2)(micro(3)-eta(2):eta(2):eta(2)-N(2))K. NO reacts with this complex to form {[(Me(3)Si)(2)N](2)(THF)Y}(2)(micro-eta(2):eta(2)-NO), a paramagnetic complex that has an electron paramagnetic resonance spectrum definitive for the (NO)(2-) radical. Density functional theory reveals that a metal d(pi) to ligand pi* interaction is crucial for the stability of this complex, which reacts with additional NO to generate the diamagnetic (ON=NO)(2-) product, {[(Me(3)Si)(2)N](2)Y}(4)(micro(3)-ON=NO)(2)(THF)(2).