Conformation stability, halogen and solvent effects on CO stretching of 4-chloro-3-halogenobenzaldehydes

Synthesis of 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazol-5(4H)-one and 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazole-5(4H)-thione and solvent effects on their infrared spectra in organic solvents

In the present study novel 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazol-5(4H)-one (compound (4)) and 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazole-5(4H)-thione (compound (5)) were synthesized. These oxadiazole ring derivatives were characterized by IR, ¹H NMR, ¹³C NMR and HRMS analyses. The solvent effects on CO, CN and CS stretching vibrational frequencies (ν(CO), ν(CN) and ν(CS)) of synthesized compounds were investigated experimentally using attenuated total reflection (ATR) infrared spectroscopy and compared with the theoretical results assigned using the potential energy distribution (PED) contributions. Furthermore, the ν(CO), ν(CN) and ν(CS) of compound (4) and compound (5) were correlated with empirical solvent parameters such as the solvent acceptor numbers, the Swain equation, the Kirkwood-Bauer-Magat equation, and the linear solvation energy relationships. Apart from the linear effects investigated in similar studies, solvent-induced vibrational shifts were investigated using the quadratic equation. The prediction capabilities of empirical solvent parameters were statistically compared. It was found that the linear solvation energy relationships show better correlation than the other empirical solvent parameters. Additionally, the quadratic equation provided more accurate predictions for the vibrational frequency locations than the Swain and the linear solvation energy relationships equations.

Structural and spectroscopic properties of 3-halogenobenzaldehydes: DFT and TDDFT simulations

Conformers of 3-halogenobenzaldehydes (3HB, halogen atom: F [3FB], Cl [3CB] and Br [3BB]) in the gas phase and solutions were studied using density functional theory (DFT) and time dependent density functional theory (TDDFT), B3LYP functional and MP2 method with 6–311+G(3df,p) and aug-cc-pVDZ basis sets. The present study aims to investigate the halogen and medium effects on the conformational stability, structural parameter, dipole moment, carbonyl stretching frequency, frontier molecular orbitals, band gap, absorption band and density of states. Carbonyl stretching frequencies were evaluated with some solvent models. All results will be useful for further analysis of halogen-substituted benzaldehydes.

Molecular, vibrational and electronic structure of 4-bromo-2-halogenobenzaldehydes: Halogen and solvent effects

The halogen and solvent effects on the structure of 4-bromo-2-halogenobenzaldehydes [C

Halogen and solvent effects on the conformational, vibrational and electronic properties of 1,4-diformylpiperazine: A combined experimental and DFT study

The molecular structure and properties of 1,4-diformylpiperazine (1,4-dfp, C6H[Formula: see text]N2O2) were investigated by Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy and density functional theory (DFT). The Becke-3-Lee–Yang–Parr (B3LYP) functional was used with the 6-31[Formula: see text]G(d,p) basis set. Total energy distribution (TED) analysis of normal modes was performed to identify characteristic frequencies by the scaled quantum mechanical (SQM) method. Halogeno-analogs of 1,4-dfp were studied to understand the halogen effect. Computations were focused on five conformational isomers of the compounds in the gas phase and in solutions. The computed and experimental frequencies of the C[Formula: see text]O stretching vibration of 1,4-dfp were correlated with the empirical solvent parameters such as the Kirkwood–Bauer–Magat (KBM) equation, the solvent acceptor number (AN), Swain parameters and linear solvation energy relationships (LSER). The electronic properties of the compounds were also examined. The findings from the present work may be useful to understand systems involving the halogens and conformational changes analogous to the compounds investigated.