1,10-Phenanthrolinium hydrogensquarate monohydrate—A non-centrosymmetric structure from two non-chiral agents

The novel hydrogensquarate salt of 1,10-phenanthroline has been synthesized, isolated and structurally elucidated by single crystal X-ray diffraction. 1,10-Phenanthrolinium hydrogensquarate monohydrate (1) crystallizes in the non-centrosymmetric P21 space group. Its hydrogensquarate anions form a stable dimer by means of (Sq)OH⋯OC(Sq) hydrogen bonds with lengths of 2.509, 2.526, 2.510, and 2.524 Å. The solvent water molecule interacts with the anion dimers by means of strong and moderate hydrogen bonds HOH⋯OC(Sq) with bond lengths of 2.782 and 2.845 Å, respectively. The 1,10-phenanthrolinium cation participates in NH⋯OH2 interactions with the water molecule (bond lengths of 2.810, 2.758, 2.779 and 2.760 Å). Surprisingly, compound contains four independent molecules in the unit cell. Optical properties were elucidated by means of linear-polarized solid-state IR-spectroscopy and UV-spectroscopy. In addition TGA, DSC, DTA data, positive and negative ESI mass spectra as well as 1H- and 13C NMR spectra are presented. Quantum chemical methods were used to calculate the electronic structure, vibrational data and electronic spectra as well as non-linear optical properties of neutral 1,10-phenanthroline and its protonated cation. Second harmonic generation measurements of the novel compound demonstrate that the compound possesses effective d coefficients of 1.9 ± 0.5 pm V−1, value that is about three times higher that of the low temperature form of potassium dideuterophosphate.