Crystal and Molecular Structure of Two Proton Transfer Compounds from Quinolin-8-ol, 4-nitro-phthalic Acid, and 1,5-Naphthalenedisulfonic Acid

Abstract

Two crystalline proton transfer compounds (quinolin-8-ol) : (4-nitro-phthalic acid) [(HL)+ · (Hnpa)−, L = quinolin-8-ol, Hnpa = 4-nitro-hydrogenphthalate] (1), and (quinolin-8-ol):(1,5-naphthalenedisulfonic acid):2H2O [(HL+)2 · (nds2−) · 2H2O, nds2− = 1,5-naphthalenedisulfonate] (2) derived from quinolin-8-ol and organic acids (4-nitro-phthalic acid, and 1,5-naphthalenedisulfonic acid) were prepared and characterized by X-ray diffraction analysis, IR, mp, and elemental analysis. Compound 1 crystallizes in the monoclinic, space group P2(1), with a = 6.9540(8) A, b = 7.4425(10) A, c = 30.2082(18) A, β = 103.309(2)°, V = 1521.4(3) A3, Z = 4. Compound 2 crystallizes in the orthorhombic, space group Pbca, with a = 14.7954(13) A, b = 11.0924(11) A, c = 16.2422(14) A, V = 2665.6(4) A3, Z = 4. In both compounds, as predicted on the basis of pKa differences, proton transfer from the acidic group to the hetero-nitrogen of the quinolin-8-ol molecule occurs, together with primary N–H···O hydrogen-bond formation between donor and acceptor atoms. In neither of the compounds the primary cyclic hydrogen-bonded R 2 2 (8) A-B heterodimer was formed, involving the second oxygen of the anion and the 8-hydroxy substituent of quinolin-8-ol; nor were there any A–A or B–B homodimers found. Instead, this molecule acts in a bridging mode to link the associated molecular units into chain polymers through hydrogen bonds and other nonbonding interactions. The role of these noncovalent interactions in the crystal packing is ascertained. These weak interactions combined, both compounds displayed 3D framework structure. In addition, these two proton transfer compounds display different stoichiometric ratios, one is 1:1, and the other is 2:1. Due to the weak interactions, the compound displays 3D framework structure.