A new organic-inorganic hybrid compound based on sulfate: Structural characterization, DFT study, Hirshfeld analysis, and electrical, vibrational and thermal properties

Abstract

This paper aims to study a new organo-sulfate (N(C2H5)4[HSO4][H2SO4]2) using X-ray diffraction, DFT, Hirshfeld surface analysis, thermal analysis, and IR, Raman, NMR, and impedance spectroscopy. The structure of this centrosymmetric compound with P21/c space group [Z = 4, a = 6.765(2) Å, b = 15.531(4) Å, c = 13.843(2) Å, β = 101.00(2)°] consists of (CH3CH2)4N+ cations, [HSO4]- anions, and bis sulfuric acid [H2SO4]2; the two sulfate species are linked via strong hydrogen bonds O–H⋯O and form (H2SO4.HSO4.H2SO4) trimmers. Hirshfeld surface analysis highlighted the predominance of O ….H/H⋯O contacts, as an indication of the strong hydrogen bonding in this compound. The IR (400–3600 cm−1) and Raman (50–3500 cm−1) spectra have been analyzed at room temperature. The bond lengths, angles, and theoretical frequencies of the optimized molecular geometry have been calculated using the DFT (B3LYP/6-31G(d)) method and compared to the experimental properties. This method represents the molecular structure and vibrational properties with reliable correlation coefficient values, calculated by the linear fitting, for distances (0.9963), angles (0.9833), and frequencies (0.9919).The 13C NMR spectrum shows two different carbon environments in the –CH2 and –CH3 groups. TGA-DTA analysis has shown that the adsorbed water molecules depart at 374 K and the crystal melts at 432 K. The electrical conductivity was measured using complex impedance spectroscopy in the frequency range of 1 kHz–13 MHz and temperature range of 313–363 K. The conductivity activation energies were calculated from the log(σT) and log(fp) curves at ΔEσ(LT) = 0.42eV and ΔEf(LT) = 0.40 eV. The conductivity relaxation parameters calculated from the M"/M"max curves (313–363K) reveal the H+ ion hopping process conduction in this material.