Origin of Anomalous Electronic Circular DichroismSpectrum of RuPt2(tppz)2Cl2(PF6)4in Acetonitrile.

Wereport a theoretical study of the structures, energetics, andelectronic spectra of the PtII/RuIImixed-metalcomplex RuPt2(tppz)2Cl2(PF6)4(tppz = 2,3,5,6-tetra(2-pyridyl)pyrazine) in acetonitrile.The hybrid B3LYP density functional theory and its TDDFT methods wereused with a complete basis set (CBS) extrapolation scheme and a conductorpolarizable continuum model (C-PCM) for solvation effects. Resultsshowed that the trinuclear complex has four types of stable conformersand/or enantiomers. They are separated by high barriers owing to therepulsive H/H geometrical constraints in tppz. A strong entropy effectwas found for the dissociation of RuPt2(tppz)2Cl2(PF6)nin acetonitrile. The UV–visibleand emission spectra of the complex were also simulated. They arein good agreement with experiments. In this work we have largely focusedon exploring the origin of anomalous electronic circular dichroism(ECD) spectra of the RuPt2(tppz)2Cl2(PF6)4complex in acetonitrile. As a result,a new mechanism has been proposed together with a clear illustrationby using a physical model. [ABSTRACT FROM AUTHOR]