DFT study of potential energy surfaces and conical intersection structures of Rhenium(I) tricarbonyl diimine complexes

Potential energy surfaces of the ground and lowest excited states of [Re(CO)3(phen)L]q (L = imH, q = +1; L = Cl, q = 0) complexes were investigated by TDDFT methods in gas phase and solvent. Two (in gas phase) or three (in solvent) tautomeric structures, differing by the angle of rotation of the imidazole ligand around the Re–N bond were found for [Re(CO)3(imH)(phen)]+. Excited state minima of the lowest singlet and triplet states were found, and luminescence energies were calculated. 11 conical intersection (CI) structures in total were obtained. Three common types of CI’s were found both for [Re(CO)3(imH)(phen)]+ and [Re(CO)3(Cl)(phen)], and additional CI type was found only for [Re(CO)3(imH)(phen)]+. Every CI type of [Re(CO)3(imH)(phen)]+ corresponds to two CI structures, differing by the angle of rotation of the imH ligand.