Enhancements of the first and second hyperpolarizability of a GMP coordination polymer: crystal structure and computational studies†

Abstract

A chiral cobalt coordination complex {[Co(GMP)(BPE)(H₂O)₃]·9H₂O}_n (1) has been studied and characterized by X-ray single crystal and powder diffraction. The crystal structural study of complex 1 reveals a 1D coordination polymer with a space group of P1 and a triclinic crystal system, which are packed in a crystal lattice via H-bonding and π–π interactions. The crystal packing's stabilization and intermolecular interactions of the complex are explored by crystallography combined with Hirshfeld surface analysis. The model complex 1 exhibits stupendous enhanced second harmonic generation (SHG), with intensity up to 2.1 times that of potassium dihydrogen phosphate (KDP). Computational studies (DFT and TD-DFT) explain the emergence of the first and second hyperpolarizability in complex 1, in which the first hyperpolarizability is associated with non-centrosymmetry and hydrogen bonding and the remarkably enhanced second hyperpolarizability originates from intramolecular charge transfer. The computed β^SHG of complex 1 is 27.70 and 3.79 times higher than those of KDP and para-nitroaniline (p-NA), respectively. The simultaneous presence of first and second hyperpolarizability suggests that the synthesized complex 1 could be a promising candidate for nonlinear optical materials with potential applications in optoelectronic devices.