QM/MM Approach to Isomerization of Ruthenium(II) Sulfur Dioxide Complex in Crystal; Comparison with Solution and Gas Phases

Abstract

The theoretical study of chemical reactions in molecular crystals is a challenging research target. To optimize the transition state in a crystal, we have improved the crystal model and modified the quantum mechanics/molecular mechanics (QM/MM) method based on the periodic MM crystal model. We applied this method to the ruthenium(II) sulfur dioxide complex [RuII(NH3)4(SO2)Py]2+ 1Py which is potentially useful for optical data storage systems in crystal because this Ru complex has two isolable metastable structures, η1-O-bound MS1 and η2-S,O-bound MS2, in addition to η1-S-bound ground state GS in crystal. MS2 and MS1 are formed from GS by photoirradiation at low temperature (10–100 K) and thermal isomerization occurs from MS2 to MS1 and from MS2 to GS by raising the temperature. For comparison, the thermal isomerization of [RuII(NH3)4(SO2)L]n+ (L = Cl–, W, and Py) was investigated in gas and aqueous phases, where the three-regions 3D reference site interaction model self-consistent field (RISM-SCF) method ...