Photo-Transformation Trajectories of Nitro-Spiropyran in Hybrid Compounds with [60]Fullerene

Abstract

Photo-and thermo-isomerization trajectories of various conversion pathways between nitrospiropyran and its trans-trans-cis merocyanine form were produced and the role of n* states was investigated along the corresponding potential energy surface calculated using the B97XD functional using the cc-pVDZ basis set. The nondissociative n* states on the photo-isomerization trajectories can switch from/to the dissociative photoactive * state at two intersections between their energy surfaces. The photochromic properties inherited in hybrid compounds of nitrospiropyran-containing [60]fullerene is interpreted as a reversible "dual energy bypass" *n* mechanism in terms of both adiabatic absorption and highly effective nonadiabatic dissipative transitions between the excited states of the photochromic fragment, that prevents energy loss through the [60]fullerene and in this way keep the photochromic properties intact.