Synthesis, an experimental and quantum chemical computational study: Proton sharing in 4-Morpholinium bis(hydrogen squarate)

Abstract

The experimental and theoretical investigation results of a novel organic squarate salt of 4-Morpholinium bis(hydrogen squarate) (1), C6H14ON+ center dot C8H3O8-, were reported in this study. The crystal structure of the title compound was found to crystallize in the triclinic P - 1 space group. In the crystals of 1 the morpholine ring adopts the chair conformation with the ethyl group in the equatorial and hydrogen atoms in axial positions. The hydrogen squarate anions are linked into a homoconjugated anion, [(HSQ)(2)H], by a short symmetric, nonlinear O8 center dot center dot center dot H2 center dot center dot center dot O2 hydrogen bond of 2.444 (2) angstrom. The structural and vibrational properties of the compound were also studied by computational methods of ab-initio performed on the compound at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) level of theory. The obtained calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 obtained are presented and compared with the X-ray analysis result. On the other hand the molecular electrostatic potential (MEP), electronic absorption spectra, frontier molecular orbitals (FMOs), conformational flexibility and non-linear optical properties (NLO) of the title compound were also studied at the 2 level and the results are reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained. (C) 2014 Elsevier B.V. All rights reserved.