Synthesis and molecular characterization of 5,5′-((2,4-dichlorophenyl)methylene)bis(1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione)

•Novel bis-pyrimidine derivative 4 was synthesized.•The 3D structure of 4 was confirmed by single-crystal X-ray structure elucidation.•Experimental and theoretical spectral analyses were studied.

A simple, economical, and green approach to the synthesis of 5,5′-((2,4-dichlorophenyl)methylene)bis(1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione) 4 using a tandem Aldol condensation-Michael addition process in aqueous diethylamine medium was described. The 3D structure of the latter was confirmed by single-crystal X-ray structure determination. The molecular structure of the titled compound was calculated using DFT B3LYP/6-311G(d,p) method. The calculated geometric parameters are in good agreement with the experimental data obtained from our reported X-ay structure. The two pyrimidinetrione rings have C16 and C20 atoms deviated significantly from the ring plane. The electronic spectra of the studied compound have been calculated using the TD-DFT method. The longest wavelength band (257.8 nm, f = 0.0276) occurs due to H → L (86%) transition. The 1H and 13C NMR calculated chemical shifts using GIAO method showed good correlation with the experimental data. The molecular electrostatic potential (MEP) showed that the most reactive sites for electrophilic and nucleophilic attacks are the carbonyl oxygen (O5) and the H21 atoms, respectively. The NBO calculations were performed to predict the natural atomic charges at the different atomic sites and to study the different intramolecular charge transfer (ICT) interactions occurring in the studied system. Interestingly, there is some delocalization of electron densities from the occupied σ-type NBO of the C20H21 to the unoccupied π∗-NBO of the two adjacent carbonyl groups.

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