Theoretical research of the force field of (difluoroamino)trinitromethane in the coordinates Хδ0

Actual problem of modern chemists-researchers is studying the properties of molecules of compounds. The latest achievements in the field of computer engineering and quantum chemistry make it possible to research various physicochemical parameters of studying compounds using theoretical calculations. Calculation methods can greatly simplify the task, as they are safer and more economical than experiment. It is noted that methane derivatives are also currently of interest for research in connection with their widespread use. This paper is devoted to the study of the force fields of molecule of (difluoro-amino)trinitromethane using quantum chemical calculations. The Becke-Lee-Yang-Parr method of density functional theory (DFT) B3LYP with a hybrid potential of 6-311++G(3df, 3pd) was chosen as the main approximation for the work performed, since when using it, the best quality of the result is noted. Also, in the present work, as an alternative to chemical (natural) coordinates, new coordinates Xδ0 were chosen, which allows one to take into account torsional vibrations. The calculations presented in this work were performed using the Gaussian and GaussView programs, designed to calculate a large number of properties and characteristics of chemical reactions. In this paper, using the proposed approach, the geometry of the molecule of (difluoroamino)tri-notromethane has been optimized, the geometric parameters of these compound were considered, in particular, the valence angles, dihedral angles, and long bonds were calculated, corresponding to the minimum energy of this molecule. For the first time, generalized force coefficients for F2NC(NO2)3 were calculated, and the "stiffness" of the chemical compounds of the molecule under study was evaluated. The frequencies of normal vibrations (wave numbers) for the studied compound in the harmonic approximation were calculated and analyzed. A comparison of the obtained wave numbers with experimental data is given. The results obtained indicate a satisfactory agreement between theory and experiment. A general view of the vibrational spectrum of (difluoroamino)trinotromethane obtained as a result of quantum chemical calculations is presented. The conclusion is drawn about the possibilities of applying the B3LYP 6-311++G(3df, 3pd) approach for calculating the frequencies of normal vibrations and force coefficients.

Спектральная диагностика динамики образования гомосопряженного комплекса [HCN.H.NCH]-=SUP=-+-=/SUP=-

A quantum-mechanical analysis of the manifestations of the NHN hydrogen bond in the vibrational spectra of the [HCN.H.NCH] + linear complex along the proton transfer reaction profile is given, and the laws governing the diagnostic parameters — potential descriptors of the dynamics of this process — are established. The surface of the potential energy and harmonic frequencies of normal vibrations along the profile of the proton transfer reaction path in the system studied are calculated. It has been shown that when the [HCNH] + and NCH fragments come closer together, a noticeable distortion of the forms of their skeletal vibrations occurs, up to complete mixing into the symmetric and antisymmetric forms. The frequency of the longitudinal vibration of the central proton ν (NH) varies along the reaction path from ~ 3600 to ~ 500 cm-1. In the region of intersection of the terms ν (NH) and ν (CN) an abrupt nature of frequency change is detected.