The Cr(III) and V(IV) complexes of 3-methylpicolinic acid (3-mpaH) were synthesized. The XRD and LC-MS/MS were performed to determine experimental geometric structure of the synthesized complexes. Their experimental spectral analyses were carried out by FT-IR and UV-Vis spectra. Their alpha-glucosidase activities were also evaluated. The synthesized Cr(III) and V(IV) complexes exhibited alpha-glucosidase inhibitory activity with the IC50 values of >600 mu M. Furthermore, the optimal molecular structure geometries, vibrational frequencies, electronic spectral properties, refractive index, band gap, second- and third-order nonlinear optical (NLO) parameters of these complexes were obtained by using DFT/HSEh1PBE/6-311G (d,p)/LanL2DZ level. NLO results demonstrate that the complex 1 is a promising candidate to materials with the high first- and second-order hyperpolarizability values obtained at 55.3 x 10(-30) and 251.0 x 10(-36) esu in ethanol solvent. The experimental refractive index and band gap parameters were comparatively presented. Lastly, NBO analysis was fulfilled to investigate inter- and intra-molecular bonding and the definition of coordination geometries around the central metal ions, as well as the electronic charge transfer interactions in the Cr(III) and V(IV) complexes. (C) 2020 Elsevier B.V. All rights reserved.