Matrix-isolation spectroscopic and computational study of [2C, 2N, 2S] isomers: Photochemical generation of SCNNCS and NCSNCS from NCSSCN

Twenty three closed-shell singlet [2C, 2N, 2S] isomers, 10 open-chain pseudohalogens, 10 consisting of a three-membered CNS ring, and three with a thiothionyl moiety, have been investigated by quantum-chemical methods at the B3LYP and CCSD(T) levels. NCSSCN is thermodynamically the most stable, followed by its NCSNCS, and SCNNCS isomers. Anharmonic vibrational wavenumbers, infrared intensities, relative Raman intensities, and UV excitation energies have also been computed to assist their detection. NCSSCN has been generated, deposited into cryogenic noble gas matrices, and characterized by IR, Raman, and UV spectroscopic methods. It has been proved by IR and UV spectroscopy that the UV photolysis of NCSSCN leads to the formation of novel pseudohalogens, namely NCSNCS and SCNNCS.