Supramolecular cocrystals of O-H...O hydrogen-bonded 18-crown-6 with isophthalic acid derivatives: Hirshfeld surface analysis and third-order nonlinear optical properties

Two cocrystals of 18-crown-6 with isophthalic acid derivatives, 5-hydroxyisophthalic acid and trimesic acid, have been successfully grown by the slow evaporation solution growth technique. Crystal structures of (18-crown-6)·6(5-hydroxyisophthalic acid)·10(H₂O) (I) and (18-crown-6)·2(trimesic acid)·2(H₂O) (II) elucidated by single crystal X-ray diffraction reveal that both cocrystals pack the centrosymmetric triclinic space group P{\overline 1}. The molecules are associated by strong/weak hydrogen bonds, π...π and H...H stacking interactions. Powder X-ray diffraction analyses, experimental and simulated from single-crystal diffractogram data have been matched. The vibrational patterns in FT-IR spectra are used to identify the functional groups. The band gap energy is estimated by the application of the Kubelka-Munk algorithm. Hirshfeld surfaces derived from X-ray diffraction analysis reveal the type of molecular interactions and their relative contributions. The constructed supramolecular assembly of crown ether cocrystal is thoroughly described. Both cocrystals exhibit a significant third-order nonlinear optical response and it is observed that (I) possesses a significant first-order molecular hyperpolarizability whereas it is negligible for (II).

Crystal structures of the [18]-crown-6 ammoniate C12H24O6 · 2 NH3 and the cryptand [2.2.2] ammoniate C18H36O6N2 · 2 NH3

The crystal structures of the new polyether ligand-ammoniates C12H24O6 · 2 NH3 (1) and C18H36O6N2 · 2 NH3 (2) have been elucidated at 123 K by single crystal X-ray structure analysis. Compound 1 crystallizes as yellow plate-like crystals in the monoclinic space group P21/c (no. 14) with unit cell parameters a = 7.572(4) Å, b = 7.724(4) and c = 14.448(7) Å with an angle β = 91.79(6)°. It consists of a molecule of [18]-crown-6 to which two ammonia molecules of crystallisation are bound by three hydrogen bonds each. The ammonia molecules reside below and above the plane of the crown ether oxygen atoms. Compound 2 crystallizes as colourless isometric crystals in the space group P6322 (no. 182) with unit cell parameters a = 8.2568(5) Å and c = 18.992(2) Å. It consists of molecules of cryptand [2.2.2] which are connected by hydrogen bonds via ammonia molecules of crystallisation, resulting in two-dimensional layers parallel to the ab-plane.