IR spectra of [formula omitted] in Ar and [formula omitted] cryomatrices: Evidence of unusual band splitting in [formula omitted] matrix

Abstract

Matrix isolation IR spectra of CH2I2 in N2 matrix are analysed using IR spectra obtained in the Ar matrix, quantum chemical calculations, and molecular point group symmetry to determine the origin of the unusual splitting observed in the CH2 antisymmetric stretching (ν6), CH2 rocking (ν7), CH2 wagging (ν8), and CI2 antisymmetric stretching (ν9) modes of CH2I2 only in N2 matrix and not in Ar matrix. The ν6, ν7, ν8, and ν9 vibrational modes belong to either B1 or B2 irreducible representations under C2V point group symmetry. IR spectra in N2 matrix is reported for the first time. IR spectra recorded in Ar matrix are consistent with previous reports. Electronic structure calculations have been performed to obtain simulated IR spectra of CH2I2 with C2V and C2 point group symmetries, (CH2I2)2 conformers, [CH2I2-H2O], and [CH2I2-(N2)4]. IR spectra obtained in Ar and N2 matrices originate from CH2I2, (CH2I2)2, and splitting of IR peaks in N2 matrix. Splitting of the IR peaks of CH2I2 in solid state is described by Davydov splitting or factor group splitting. The observed splitting of IR peaks in N2 matrix is due to the lowering of symmetry of CH2I2 from C2V to one of its sub groups due to the perturbation of the rigid N2 matrix that possess quadrupole moment.