Vibrational spectroscopic investigation of free and coordinated 5-aminoquinoline: The IR, Raman and DFT studies

Combined experimental and computational vibrational spectra of 5-aminoquinoline (5-AQ) and its zinc chloride complex {Zn(5-AQ)2Cl2}, together with the computational results of 5-AQ interacting with H2O through the ring nitrogen {5-AQ·H2O} have been reported. The geometry of the free 5-AQ were optimized using DFT method at B3LYP/6-31G(d,p) and 6-31++G(d,p) levels of theory. Coordinated 5-AQ molecules; {5-AQ·H2O} and {Zn(5-AQ)2Cl2} were optimized using DFT/B3LYP/6-31G(d,p) level of theory. Harmonic and anharmonic vibrational frequencies and infrared intensities were calculated at the same level of theory. The fundamental vibrational modes were characterised depending on their total energy distribution (TED%). Coordination effects on 5-AQ vibrational frequencies were investigated.