Abstract
Crystals of 7,11-bis(2,4-dichlorophenyl)-2,4-dimethyl-2,4-diazaspiro[5.5]undecane -1,3,5,9-tetraone were grown in polar solvents and subjected to single crystal X-ray diffraction. The molecular crystal is Triclinic, P-1, a= 8.3734 (19) , b= 12.382 (3) , c= 12.871 (3) , alpha= 66.639 (7) (a similar to), beta= 85.148 (7) (a similar to), gamma= 70.690 (6) (a similar to), V= 1154.5 (5) (3), Z= 2, D (calc)= 1.519 g cm (-3). The optimized molecular structure of the studied compound using B3LYP/6-311G(d,p) method showed good agreement with the X-ray structure. The electronic and spectroscopic properties of the title compound were predicted. The NBO calculations were used to calculate the natural atomic charges at the different atomic sites as well as the intramolecular charge transfer (ICT) interactions among the most significant natural orbitals. The high LP(N) -> BD*(2)C-O ICT interaction energies indicate strong electron delocalization from the lone pair of the N-atoms of the pyrimidinetrione ring to the adjacent carbonyl groups. In contrast, the small LP(O) -> BD*(1)C-H stabilization energies (E ((2))) indicated weak C-H-O interactions. Experimentally, the studied compound showed the most intense electronic transition band at 232 nm which is calculated using TD-DFT method as a shoulder at 231.3 nm (f =0.0832) and it belongs to H-3/H-1 -> L+1 and H-2 -> L+2 excitations. The GIAO calculated H-1 and C-13 NMR chemical shifts showed good correlations with the experimental data.