IR spectra of CH2I2 in Ar and N2 cryomatrices: Evidence of unusual band splitting in N2 matrix

Matrix isolation IR spectra of CH2I2 in N-2 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 (nu(6)), CH2 rocking (nu(7)), CH2 wagging (nu(8)), and CI2 antisymmetric stretching (nu(9)) modes of CH2I2 only in N-2 matrix and not in Ar matrix. The nu(6), nu(7), nu(8), and nu(9) vibrational modes belong to either B-1 or B-2 irreducible representations under C-2V point group symmetry. IR spectra in N-2 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 C-2V and C-2 point group symmetries, (CH2I2 )(2) conformers, [CH2I2 - H2O ], and [ CH2I2 - (N-2)(4) ]. IR spectra obtained in Ar and N-2 matrices originate from CH2I2 , (CH2I2 )(2), and splitting of IR peaks in N-2 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 N-2 matrix is due to the lowering of symmetry of CH2I2 from C-2V to one of its sub groups due to the perturbation of the rigid N-2 matrix that possess quadrupole moment.(C) 2022 Elsevier B.V. All rights reserved.