Spectroscopic analysis and thermodynamic investigation of Newly Synthesized Novel dihydro-pyrimidine derivatives by using DFT (B3LYP) calculations.

• Experimental and theoretical spectral investigation of dihydro-pyrimidines. • Experimental and theoretical Fourier transform infrared (FT-IR) spectra were recorded and compared. • Experimental and theoretical IRaman were also calculated and compared. • A benchmark analysis was performed by employing DFT functions by estimating HOMO to LUMO UV transitions, band gaps (eV) and oscillator strength φ by comparing with experimental λ max. Theoretical 1H and 13C NMR chemical shift values. • In addition, Muliken charges, natural population analysis (NPA), fukui functions, and thermodynamic parameters were calculated. In this article, theoretical and experimental study is presented for eight derivatives of dihydro-pyrimidinones (symbolized as U1-U6, U10 and U11). The Fourier transform infrared (FT-IR) spectra of dihydro-pyrimidinones were recorded in the range of 4000cm−1 to 400cm−1 in solid phase and compared with experimental vibrational assignments. The potential energy distributions (PED) was assigned to each scaled vibrational wavenumber value by using Vibrational Energy Distribution Analysis (VEDA4) program. In order to get insight into electronic properties and a good UV absorber compound Time Dependent Density Functional Theory (TF-DFT) approach was taken into consideration. A benchmark analysis was performed by employing DFT functional B3LYP, HSEH1PBE, MPW1PW91, WB97XD by estimating HOMO to LUMO UV transitions, band gaps (eV) and oscillator strength φ by comparing with experimental λ max. Theoretical 1H and 13C NMR chemical shift was calculated using GIAO method and compared with already published experimental NMR chemical shift values by using linear correlation factor R2. Electron poor, rich and reactive sites were probed by Mulliken atomic charge, natural population analysis (NPA) and fukui functions accompanying the optimized structures by utilizing density functional theory (DFT) methods with B3LYP function and 6–311 G (d, p) as basis set. In last vibrational assignments were subjected to thermodynamic parameter calculations using Moltran v.2.5. program. [Display omitted] [ABSTRACT FROM AUTHOR]