Abstract
The work presented in this paper deals with the experimental and theoretical investigations on the ground state structure and CT transitions in complex obtained from the reaction between picric acid (PA) and the antibiotic drug ciprofloxacin (Cip) using two theoretical methods: DFT; density functional theory and TD-DFT; time-dependent density functional theory. The HOMO and LUMO energies permit the calculation of molecular and atomic properties and exhibit the CT occurs in the molecule. The equilibrium geometry, bonding features, and vibration modes have also been examined. Molecular stability appearing from hyperconjugative interactions leading to its charge delocalization has been resolved using natural bond order (NBO). H-1 NMR chemical shifts of the molecule were calculated using the gauge-independent atomic orbital (GIAO) method. This study suggests that the CT interaction between the PA and the drug Cip was associated with a proton transfer from PA acceptor to Cip donor followed by appearing intermolecular hydrogen bond. The theoretical data were found to be in good agreement with the experimental data previously reported in the literature.