Synthesis, spectral and theoretical (DFT) investigations of 4,6-diphenyl-6-hydroxy-1-{[(1Z)-1-phenyl ethylidene] amino}tetrahydropyrimidine-2(1H)-one

4,6-diphenyl-6-hydroxy-1-{[(1Z)-1-phenylethylidene]amino}tetrahydropyrimidine-2(1H)-one (PPEP), a member of pyrimidine derivatives which represents a broad class of compounds with a wide range of biological activities, was newly synthesized and its structural characterization was made by spectral measurements. Density Functional Theory (DFT) calculations at B3LYP and CAM-B3LYP functionals with 6-31G(d) level of theory were carried out to investigate spectral characteristics, stability, structural and electronic properties of the compound as well. For this purpose, rotational barrier, conformer, hydrogen bonding, Natural Bond Orbital (NBO), Frontier molecular orbital (HOMO-LUMO), Molecular Electrostatic Potential (MEP), Mulliken & APT & NBO population and normal vibrational analyses were performed for PPEP in this study. Two stable conformational isomers were obtained by potential energy surface scan (PES) calculations. PPEP shows amide <-> imide tautomerism over transition state (TS). The amide forms are found more stable than the imide forms by similar to 18-20 kcal/mol and require similar to 47-49 kcal/mol for the transitions. The theoretical vibrational wavenumbers of the most stable conformer in the amide form were in good agreement with the experimental IR values having the RMS errors of 9.82 cm(-1) and 13.38 cm(-1), with the two methods and the new better scaling factors were obtained as 0.9614 and 0.9497 for B3LYP/6-31G(d) and CAM-B3LYP/6-31G(d) levels, respectively. (C) 2021 Elsevier B.V. All rights reserved.