Synthesis, crystal structure, spectroscopic and nonlinear optical properties of organic salt: A combined experimental and theoretical study

The 2-methoxy-pyrido[1,2-a]quinoxalin-11-ylium bromide (2MPQYB) crystal was characterized from single crystal X-ray diffraction (SCXRD) and spectroscopy analysis. The fluorescence spectrum of the compound showed one broad peak at 473 nm. The supramolecular arrangement in solid state was confirmed by 2D-fingerprint plots and Hirshfeld surface analysis. An additional topological analysis from quantum theory of atoms in molecules (QTAIM) highlights the observed halogen bonds on solid state for 2MPQYB. Also the supermolecule (SM) approach was used to simulate the crystalline environment with 246,064 atoms and an ab-initio calculation method, which includes the Density Functional Theory (DFT) at CAM-B3LYP/6-311++G(d,p) level, was used to estimate the crystal linear refractive index and the third-order nonlinear susceptibility at the frequency of omega = 0.086 a.u. (lambda = 532 nm) and the obtained values were 1.85 and chi(3) = 621.14 x 10(-22)m(2)/V-2 respectively. This chi(3)-value is up to 312.13 times greater than obtained for others organic crystals of the literature, thus indicating that the 2MPQYB can be considered for various applications of NLO materials. (C) 2020 Elsevier B.V. All rights reserved.