Global Journal of Science Frontier Research, H: Environment & Earth Science, Volume 23 Issue 1

Investigation of Formaldehyde+Hydrogen Fluoride Complex in Gas Phase by the Help of Ftir Spectroscopy and Computational Methods Akhtam Amonov Abstract- High-resolution infrared absorption spectra of the H 2 CO···HF complex and its monomers are recorded in a gas phase in C=O and C−H regions using Bruker HR 125 spectrometer recorded at 0.05 cm -1 resolution. After complex formation about the HF stretching band complicated shapes are not observed due to weak interaction couplings between C=O and C−H stretching of the H 2 CO•••HF complex. Also, quantum chemical calculations are performed in mp2//6311++g(3df, 3pd) approximation, and energetic, geometrical, and harmonic spectral parameters have been calculated. Keywords: absorption spectra, hydrogen bond, hydrogen fluoride, formaldehyde. I. I ntroduction ydrogen bond (HB) is vital in many physical, chemical, and biological systems in life, and hydrogen fluoride (HF) is one of the strong proton donor molecule which is worthy of investigation nature of (HB). In [1] ν (HF) stretching band formation mechanisms of B···HF complexes were investigated both experimentally and theoretically in detail. Recently, computational efforts performed on the relevant complexes [2]. In [3] for (H 2 CO) 2 •••HF and H 2 CO•••(HF) 2 trimers accurate spectral parameters were presented through a very high level of quantum chemical calculations. Optimal geometry, harmonic spectral parameters and energetic evaluations of the H 2 CO···HF complexes were shown in [4]. This (CH 2 O) 2 complex has been investigated both experimentally and theoretically by THz spectroscopic and CCSD(T)- F12/aug-cc-pV5Z and MP2/aug-cc-pVQZ quantum chemical calculations [5]. In this work dissociation energy of the dimer is estimated as D 0 =13.7±0.3 kJ·mol −1 for the global potential energy minimum. Anharmonic calculations in mp2/6- 311++G(3df,3pd) approximation and low temperature matrix-isolation experimental studies were performed in [6]. For the CH 3 CN···HF complex, both experimental and computational results have showed in our paper [7]. In [8], spectral and geometrical parameters of the [F(HF) 2 ]- and [F(DF) 2 ]- complexes were performed by using the Author: Institute of Engineering Physics, Samarkand State University Boulevard 15, 140104, Uzbekistan. e-mail: akhtamul@gmail.com mp2 theory and multidimensional variation methods. Anharmonic calculations are play an essential role in the investigation of hydrogen bonded molecular complexes due to well agreement with the experimental results. Recently, numerous works have been devoted to solving anharmonic multidimensional problems with the help of Schrödinger equations with the variational methods [9- 11]. In [12] authors utilized fully automated code for the establishing of interatomic force constants for the identification ro-vibrational spectral parameters for several HB molecular complexes. The results in the report are significantly important to analyze internal dynamics, to recognize spectral manifestation of molecular complexes, and to distinguishing overlapping spectral lines of noncovalent bonded molecular complexes. In this work, H 2 CO···HF complex and monomers are studied with the help FTIR spectroscopy in the gas phase and quantum chemical calculations. Obtained results are coincided with relevant literature. II. E xperimental and C omputational M ethods a) Experimental Methods The high-resolution absorption spectra of the H 2 CO···HF complex and H 2 CO monomer were recorded with the help Bruker 125 HR spectrometer at the resolution of 0.05 cm –1 in the gas phase. Formaldehyde molecule transferred from the powder to the gas phase by the phase changer vacuum equipment. The vacuum atmosphere has created inside of cavity cell, and the samples were placed into stainless steel cavity according to the real gas lows. The stainless-steel cavity was 20 cm in length with sapphire and ZnSe windows. Total pressure of the mixture was about 20–100 Torr. b) Computational Methods Quantum chemical calculations are carried out by the help of the latest version of GAUSSIAN 16 software [15] with mp2/6-311++G(3df,3pd) approximation. Equilibrium geometries, interaction energies, and various harmonic spectral parameters of the complex have been determined. H 1 Year 2023 15 © 2023 Global Journals Global Journal of Science Frontier Research Volume XXIII Issue ersion I VI ( H )