Steric effect involvement on norbornadiene-quadricyclane system for maximizing the solar energy storage: DFT calculations

Solving today's energy problems through the employment of the environmentally safe solar energy has received much attention [1]. Intramolecular photochemical [2π-2π]-cycloaddition of norbornadiene, 1, to quadricyclane, 2, has been studied as a mechanistic point of view. The 1 / 2 system has been used for solar energy storage, in molecular switching, in optoelectronic devices, as a data storage compound, as photodynamic chemosensor for metalcations, as a potential photoresponsive organic magnet and as an energetic binder for solid rocket propellants [2-6]. As a continuation of our studies [7-8], we studied the photochemical energy storage in the ground states of 1 / 2 system with exchanging of monoheteroatoms at C1, C2 or C7 atoms of 1 and 2.