Molecular structure of 1,4-bis(substituted-carbonyl)benzene: A combined experimental and theoretical approach

Abstract The reaction of pyrazole derivatives (pyrazole (Pz), 3-methylpyrazole (MPz) and 3,5-dimethylpyrazole (DMPz)) with terephthaloyl dichloride (TD) in the presence of Et3N afforded the desired products, 1,4-bis(pyrazolylcarbonyl)benzene (1), 1,4-bis(3-methylpyrazolylcarbonyl)benzene (2) and 1,4-bis(3,5-dimethylpyrazolylcarbonyl)benzene (3). Good quality crystals were isolated and diffraction data for single crystal were collected which revealed that compounds 1–3 are monoclinic with space group P21/n, C2/c and P21/c, respectively. These compounds were obtained as a result of C–N coupling reaction between the acid chloride and pyrazol derivatives with the intent to explore their structure in solution as well as solid state. Density function theory (DFT) calculations using B3LYP and CAM-B3LYP functionals with 6-311G(d,p) basis set were performed to explore geometric and electronic properties of compounds. The Root Mean Square Error (RMSE) has also been calculated for the values of geometric parameters, indicating a good agreement with experimental findings. Moreover, frontier molecular orbitals (FMOs) and natural bond orbitals (NBOs) analyses were carried out through B3LYP/6-311G(d,p) level of theory. The linear polarizability (α) values of nonlinear optical (NLO) analysis were calculated with the same level of theory and basis set as FMO but under different solvent conditions. Time Dependent Density Functional Theory (TD-DFT) study of these pyrazole substituted derivatives was performed aiming to investigate UV–Visible behavior. The stability of molecule has been additionally analyzed by Hirshfeld surface analysis in addition to NBO analysis. The calculated HOMO and LUMO energies from FMO assisted in calculating global reactivity parameters (Chemical hardness, chemical softness, electronegativity, EA, IP and electrophilicity). Natural population analysis (NPA) and Molecular electrostatic potential (MEP) were also performed to obtain insights about the reactivity of compounds 1–3. Theoretical calculations indicate that these compounds have considerable low reactivity and can be used for development of coordination chemistry under optimum conditions.