Density Functional Study of the Ground and Excited State Potential Energy Surfaces of aLight-Driven Rotary Molecular Motor(3R,3'R)-(P,P)-trans-1,1',2,2',3,3',4,4'-Octahydro-3,3'-dimethyl-4,4'-biphenanthrylidene

摘要

Potential energy surfaces of the ground and the first excited singlet states of the (3R,3' R)-(P,P)-trans-1,1',2,2',3,3',4,4'-octahydro-3,3'-dimethy1-4,4'-biphenanthrylidene rotary molecular motor have been investigatedalong the central C4=C4'double bond twisting mode starting from the(P,P)-transand P,P)-cisconformations occurring in the photoisomerization cycle of this compound. The potential energy profilesobtained with the help of the state average spin restricted ensemble-referenced Kohn—Sham (SA-REKS)method feature minima on the excited state surface, the positions of which are displaced with respect to thebarriers on the ground state surface toward the isomerization products, the (M,M)-cis and the (M,M)-transconformations, respectively. The origin of these minima is analyzed and explained. The results of the presentstudy suggest that the experimentally observed unidirectionality of photoinduced rotation in the above compoundcan be corroborated by the obtained profiles of the ground and excited state potential energy surfaces.