Vibrational spectroscopy, electrical characterization, nonlinear optical properties and DFT calculation of (NEt<sub>4</sub>)(H<sub>2</sub>AsO<sub>4</sub>)(H<sub>3</sub>AsO<sub>4</sub>)<sub>2</sub>

<p>An organic-inorganic compound of tetraethylammonium dihydrogenarsenate bis(arsenic acid) salts of formula (NEt<sub>4</sub>)(H<sub>2</sub>AsO<sub>4</sub>)(H<sub>3</sub>AsO<sub>4</sub>)<sub>2</sub>, a potential new nonlinear optical material, was prepared by a slow evaporation technique and characterized by IR and Raman spectroscopy accomplished with DFT calculation and electrical-dielectrical measurements. The structure has been solved using direct method and refined by least-squares analysis. In this case, the structure consists of infinite parallel two-dimensional planes built of mutually H<sub>2</sub>AsO<sub>4</sub><sup>−</sup>, H<sub>3</sub>AsO<sub>4</sub> tetrahedra connected by strong O–H⋯O hydrogen bonding giving birth to trimers. The geometry, first hyperpolarizability and harmonic vibrational wavenumbers were calculated by means of density functional theory (DFT) with the B3LYP/6-31G(d) level of theory. Good consistency was found between the calculated and the experimental structure, IR, and Raman results. The first hyperpolarizability β<sub>tot</sub> of the title compound is about 1.75 times more than that of the reference crystal KDP. The complex impedance has been investigated in relation to the temperature and frequency ranges 297 and 373 K and 1 to 100 KHz, respectively. The conductivity temperature variation shows a typical Arrhenius-type behavior with a linear dependence on logarithm of conductivity. Transport properties in this material appear to be due to proton hopping mechanism.</p>