Microwave-assisted solvent-free synthesis, Hirshfeld surface analysis and DFT studies of 1-(hydroxymethyl)-pyrazoles

Abstract

A facile high-yield, solvent-free approach for the synthesis of a series of 1-(hydroxymethyl)-pyrazoles under microwave irradiation was developed for the first time. The structures of four pyrazoles compounds were characterised by a single-crystal X-ray diffraction, and showed interesting intermolecular O‒H∙∙∙N hydrogen bonding linking two pyrazoles molecules to form R22(10) dimer architectures. In additional, the intermolecular interactions in the crystal were investigated through the Hirshfeld surface analysis to understand the characteristics of the close contacts, and the 2D-fingerprint plot data exposed that a significant contributions to the crystal packing are from N∙∙∙H/H∙∙∙N contacts. The geometry optimization, electronic properties and energies level of HOMO, LUMO were performed by Density functional theory (DFT) calculations. Quantitative electrostatic potential analysis (ESP) and independent gradient model based on Hirshfeld partition (IGMH) explained the active hydrogen bonding sites in four pyrazoles compounds and confirmed the hydrogen bonding modes in their crystal structure.