Crystal Structure, Raman Spectroscopy and Dielectric Properties of New Semiorganic Crystals Based on 2-Methylbenzimidazole

Abstract

New single crystals, based on 2-methylbenzimidazole (MBI), of MBI-phosphite (C16H24N4O7P2), MBI-phosphate-1 (C16H24N4O9P2), and MBI-phosphate-2 (C8H16N2O9P2) were obtained by slow evaporation method from a mixture of alcohol solution of MBI crystals and water solution of phosphorous or phosphoric acids. Crystal structures and chemical compositions were determined by single crystal X-ray diffraction (XRD) analysis and confirmed by XRD of powders and elemental analysis. Raman spectroscopy of new crystals evidences the presence in crystals of MBI-, H3PO3-, or H3PO4- and water molecules. Dielectric properties of crystals reveal strong increase and low frequency dispersion of dielectric constant and losses at heating, indicating the appearance of proton conductivity. At low temperatures in MBI-phosphate-2, an increase of dielectric constant analogous to quantum paraelectric state is observed.

Structural Properties and Dielectric Hysteresis of Molecular Organic Ferroelectric Grown from Different Solvents

“…Some details of the XRD experiment and the analysis of XRD patterns are described in Ref. [19] and in Supplementary Materials (SM) to this article. Only brief necessary information on these issues will be given here.…”

“…A detailed analysis of the Raman spectra of MBI crystals grown from ethanol and their comparison with the spectra known in the literature is given in [19]. Figure 2 shows the Raman spectra of MBI samples grown from acetone, d-acetone and ethanol.…”

“…MBI single crystals and films have been grown by vacuum sublimation [5,11] or evaporation from a solution of chemically prepared MBI powder in organic solvents [6][7][8][9][10]. It is known that, when growing crystals from solutions, the solvent can significantly affect the properties of the crystals obtained, and at present the influence of the solvent is being intensively studied [15][16][17][18][19][20][21][22][23][24][25][26]. In particular, the growth of organic crystals from aqueous solutions can be accompanied by the appearance of liquid inclusions, that is, a noncrystallized liquid solution (mother liquor), physically enclosed in a growing crystal [15].…”

“…The presence of such inclusions can lead to the appearance of the temperature dependences of the dielectric constant or heat capacity of features characteristic of first-order phase transitions [17]. The crystals grown from aqueous solution can also include the water molecules as part of crystal structure [18,19]. Depending on the solvent the new compounds may crystallize, in which the solvent molecule is part of the crystal structure [16,20,21].…”

Supramolecular Synthon Promiscuity in Phosphoric Acid–Dihydrogen Phosphate Ionic Cocrystals

“…, ICCs were found to form reliably, and we consider such ICCs to be relevant to pharmaceuticals for improving the physicochemical properties of ionizable APIs as phosphoric acid is inexpensive, has a low molecular weight, and is FDAapproved. In addition, from a material property perspective, such ICCs may exhibit superior dielectric properties vs the corresponding DPA salts 79. ■ ASSOCIATED CONTENT * sı Supporting InformationThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.cgd.2c00150.…”