Theoretical Design of a Molecular Switch with Controlled Hydrogen Bonds: Electronic and Vibrational Spectra of [Co(2,2′-biimidazole)(C6H4O2)(NH3)2

Abstract

Abstract The electronic and vibrational spectra of a proton–electron-coupled inorganic complex [Co(Hbim)(C6H4O2)(NH3)2]2 having multistable states, were theoretically investigated using density functional theory calculations using B3LYP parameters. The electronic excitation spectrum in the low-spin ground 1Ag state of the complex has no strong absorption in the visible region (600–700 nm), while in the high-spin 5A1 and 9Ag complexes, some prominent peaks were predicted in the visible region. Frequency analyses of the 1Ag, 5A1, and 9Ag states showed the strong band of the NH stretching vibration at 2690, 2120, and 2770 cm−1, respectively. Based on this, it is possible to distinguish 5A1 from 1Ag and 9Ag by measuring IR light absorption at 2120 cm−1, showing that [Co(Hbim)(C6H4O2)(NH3)2]2 would be a good candidate for use as optically durable molecular level memory.