Synthesis, structural characterization, and computational study of novel (E)-N′-(1-p-tolylethylidene)furan-2-carbohydrazide

An efficient synthesis of the novel (E)-N′-(1-p-tolylethylidene)furan-2-carbohydrazide is described. The molecular structural features were then confirmed by single crystal X-ray diffraction. Quantum chemical calculations including molecular geometry, intermolecular H-bonds, and vibrational frequencies were carried out for the structures to explain stability and geometry using both density functional (DFT/B3LYP) and the Hartree-Fock (HF) with 6-311+G(d,p) basis set. The calculated structural parameters are presented and compared with their experimental X-ray counterparts. The E-isomer is a global minimum on the potential energy surface. However, validation of the computational methods here via comparison with the observed X-ray data enabled computational analysis to predict that head-to-tail E/E-dimer of the observed E-isomer has significantly stronger intermolecular hydrogen bonding compared with the non-observed Z/Z-dimer. It was observed that the stretching mode of NH and CO shifted to lower frequencies, due to pairwise intermolecular NH⋯O hydrogen bonds. This provides a clear rationale for the isomeric specificity obtained and provides a validation of the optimized method which could be applied to predict structures of other useful carbohydrazides. Generally, it has been concluded that the findings of B3LYP hybrid functional fit better to the observed geometrical and vibrational parameters than the results of the HF.