Density functional theory calculations of iodine cluster anions: Structures, chemical bonding nature, and vibrational spectra

Structures, chemical bonding nature, and vibrational properties of polyiodide anion species ( I n - ; n = 3, 5, 7) are investigated by means of density functional theory calculations (B3PW91/MCPtzp+). All polyiodide anion species are predicted to have single or branched chain structures. Natural bond orbital (NBO) analyses of I n - (n = 5, 7) isomers clearly show that the polyiodide species consists of I2 and linear I 3 - units. A comparison of theoretically predicted Raman spectra with experimental reports revealed the existence of I n - (n = 5, 7) isomers with three-center four-electron (3c–4e) bonds.