LAUSR

Abstract Novel series of Zn2+ binary and ternary complexes with antiepileptic drug (gabapentin) and neurotransmitters (glycine, aspartic acid, glutamic acid, serine, γ-aminobutyric acid and adenosine) were synthesized. All the complexes were non-electrolytes where their purity and molecular weights were confirmed using GC-MS spectra. C,H,N,M analysis and EDX spectra showed the formulae [Zn(Gpn)2SO4], [Zn(Gpn)2Br2], [Zn(Gpn)(Gly)½SO4], [Zn(Gpn)(Asp)(H2O)]·3H2O, [Zn(Gpn)(Glu)(H2O)]·4H2O, [Zn(Gpn)(Ser)½SO4], [Zn(Gpn)(GABA)SO4], and [Zn(Gpn)(Ade)SO4]·2H2O. Crystallographic parameters were calculated for the complexes from their XRD data using Expo2014 computer program showing monoclinic and orthorhombic crystal systems with space group P 1 21 1, A 1 2/n 1, A 1 2 1 and P 2 a. IR data revealed that Zn2+ is bonded through COO− of the gabapentin, as a monodentate ligand, and through NH2 and COO− of the neurotransmitter as a bidentate chelating ligand. 1H NMR spectra showed that gabapentin exists in a zwitterion form. UV–Vis and fluorescence spectra exhibited the π→π*, n→π*, and LMCT transitions. Also, TGA, DTG, DTA, and the suggested decomposition mechanism confirmed the proposed structure of the complexes. Kinetic and thermodynamic parameters were calculated for the second and third decomposition steps using Coats-Redfern equation. Docking studies showed that some complexes showed superior activity compared to gabapentin due to their larger size, ability to form stronger hydrophobic and/or polar interactions with the residues on the loops with Val175 and Gln234, and direct polar interaction with Tyr193 which is not feasible in case of gabapentin.