Conformational analysis and nonlinear optical properties of the N, N '-pentamethylenebis(salicylideneiminato)manganase(II) complex

Abstract

Conformational analysis of the tricyclic Schiff base chelate complex N,N'- pentamethylenebis(salicylideneiminato)manganese(II) is performed by means of the molecular mechanic (MM+), semi-empirical PM3 and density functional (B3LYP/LanL2DZ) methods, respectively. Eight starting structures of the complex are minimized. The structures of the three lowest minimum energy conformations of cyclooctane, boat-chair (bc), chair-chair (cc) and boat-boat (bb), are used as initial approximations to the geometry of the eight-membered chelate ring. The absolute-MEC (Mn-bc4) and the most unstable one (Mn-bb) originate from the boat-chair-shaped form of the eight-membred cycle, differing in the position of the metal atom. After the conformational analysis of the tricyclic Schiff base chelate complex, nonlinear optical properties and optical band gap (EHOMO-LUMO) were calculated with B3LYP/LanL2DZ level of theory for all conformations. The frontier molecular orbital calculations clearly show the inverse relationship of optical band gap (EHOMO-LUMO) with the total static hyperpolarizability.