Experimental and theoretical investigation of the spectroscopic and electronic properties of pyrazolyl ligands

The electronic and spectroscopic properties of seven pyrazole derivatives are presented in order to give a clear understanding of their distinguishing features. Four out of the seven ligands are synthesised and are also characterised experimentally. A very high correlation was observed between the experimental and the theoretical IR, H-1 NMR and C-13 NMR, which help in the characterisation of the ligands. The excitation properties computed using the TDDFT shows that most of experimentally observed absorptions of the ligands are predominantly form either the HOMO or HOMO-1 to LUMO or LUMO+1. The characteristic features of the *N atoms (i.e. metal available coordinating centre) shows that the carboxylic unit may possibly decrease the metal affinity of the pyrazole unit while the pyridine unit will increase the affinity. The conductivity properties of the seven ligands are found to be in the order of bdmpzpy > bpzpy > bphpza > bdcpzpy > phpz > dcpz. The J-coupling of *N-N can give an insight into the variation in their bond distance, bond stretch and bond strength in the ligands. Also the atomic properties of the *N atoms and their *N-N bonds can help in the molecular characterisation, differentiation and in prediction of the non-linear optical properties of the ligands as conductive materials. (C) 2014 Elsevier B.V. All rights reserved.