The Complexes between CH₃OH and CF₄. Infrared Matrix Isolation and Theoretical Studies

Abstract

The complex formed between methanol and tetrafluoromethane has been identified in argon and neon matrixes by help of FTIR spectroscopy. Three fundamentals (nu(OH), nu(FCF), and nu(CO)) were observed for the complex isolated in the two matrixes, and the OH stretch was red shifted in a neon matrix and blue shifted in an argon matrix with respect to the corresponding vibration of the methanol monomer. The theoretical studies of the structure and spectral characteristics of the complexes formed between CH(3)OH and CF(4) were carried out at the MP2 level of theory with the 6-311+G(2df,2pd) basis set. The calculations resulted in three stationary points from which two (I-1, I-2) corresponded to structures involving the O-H...F hydrogen bond and the third one (I-3) to the non-hydrogen-bonded structure. The topological analysis of the distribution of the charge density (AIM theory) confirmed the existence of the hydrogen bond in I-1, I-2 complexes and indicated weak interaction between the oxygen atom of CH(3)OH and three fluorine atoms of CF(4) in the I-3 complex. The comparison of the experimental and theoretical data suggests that in the matrixes only the non-hydrogen-bonded complex I-3 is trapped. The blue/red shift of the complex OH stretching vibration with respect to the corresponding vibration of CH(3)OH in argon/neon matrixes is explained by the different sensitivity of the complex and monomer vibrations to matrix material. The ab initio calculations performed for the ternary CH(3)OH-CF(4)-Ar systems indicated a negligible effect of an argon atom on the binary complex frequencies.

Kinetics of OCN−formation from the HNCO + NH3solid-state thermal reaction

“…This temperature may be the room temperature at which the deposition of the two gases is performed, the room temperature proportion between HNCO a (t=0) and HNCO na (t=0) is frozen when the molecular solid is condensed onto the cold surface. At a 300 K room temperature, we found a difference in Gibbs energy of 4.3 kJ mol −1 , which is on the order of magnitude of a molecular reorientation (Mielke et al 2006(Mielke et al , 2008. This means that our ice analogs, made from a room temperature gas quenching into an amorphous solid, are out of equilibrium.…”

FTIR/PCA study of propanol in argon matrix: The initial stage of clustering and conformational transitions

“…The most significant results on this field have been obtained using the vibrational spectroscopy (FTIR absorption and Raman) together with trapping/isolation in various cryogenic matrices [4][5][6][7][8][9][10][11][12][13][14]. This is mainly because the spectral acquisition carried out on isolated clusters at very low temperatures causes the appearance of narrow peaks with minimal band overlapping.…”

Theoretical studies on the infrared spectrum of the tetrahedral molecules R2MH2 (R = D(H), CH3, OH; M = Ti, Zr, Hf)

“…As shown in Table 3, interestingly, the gas phase calculations show that the TiH 2 scissor and wag frequencies are nearly degenerate (612.4 vs. 613.9 cm -1 ) while the argon matrix calculations indicate that the two frequencies are just like a doublet (594.1 vs. 600.1 cm -1 ). This point should be paid more attention to during the assignment of the experimental frequencies since the doublets may be easily explained to be due to the matrix site effect [4,9,10,34]. Note that the experimental argon matrix frequency 588.5 cm -1 was only assigned to the TiH 2 wag mode of their calculation (616.8 cm -1 ) [3].…”

“…However, the existing calculations are not in exact consistency with the experiments because the experimental frequencies were measured from the R 2 MH 2 molecules isolated in the rare gas matrix while the calculations were based on a gas phase model and the matrix effect was not modelled. Existing experiments have demonstrated that the rare gas matrix has an evident effect on the infrared fundamental frequencies of a single molecule [7][8][9] and that, sometimes, the matrix effect can even change the relative magnitude of two vibrational frequencies [9,10]. As a consequence, the modelling of the rare gas matrix effect should be of great significance for understanding the experimental matrix isolation infrared spectra of the R 2 MH 2 molecules.…”