DFT study of hydrogen-bonding effects on the 17O, 14N and 2H electric field gradient tensors and isotropic chemical shifts of 8-hydroxyquinolinium and the 2-carboxy-4,5-dichlorobenzoate (I) and 8-aminoquinolinium and the 2-carboxy-4,5-dichlorobenzoate (II)

The structures of the 1:1 proton-transfer compounds of 4,5- dichlorophthalic acid with 8-hydroxyquinoline, 8-aminoquinoline and quinoline-2-carboxylic acid (quinaldic acid), namely anhydrous 8-hydroxyquinolinium2-carboxy-4,5 dichlorobenzoate, C9H8NO+.C8H3Cl2O4_,(I),8-aminoquinolinium2-carboxy-4,5- dichlorobenzoate,C9H9N2 +.C8H3Cl2O4 -,(II), have been determined at 130 K. Compounds (I) and (II) are isomorphous and all twocompounds have one-dimensional hydrogen-bonded chain structures, formed in (I) through O—H…Ocarboxyl extensions and in (II) through N+—H…Ocarboxyl extensions of cation–anion pairs.In both (I) and (II), there are also cation–anion aromatic ring π − π associations [1]. In all two compounds, proton transfer has occurred, with the quinolinium group giving a primaryN+–H…Ocarboxyl hydrogen-bonding interaction However, in (I) and (II), which are isomorphous, the association is hetero meric (Figs. 1 and 2) . Since the most characteristic nature of HB is electrostatic, those techniques dealt with this nature are proper in the investigation of HB properties.The solid-state NMR parameters, quadrupole coupling constants and isotropic chemical shifts at oxygen, nitrogen, and hydrogen nuclei of the 8-hydroxyquinolinium cation and the 2- carboxy-4,5-dichlorobenzoate anion in (I) and 8 aminoquinolinium cation and the 2-carboxy-4,5-dichlorobenzoate anion in (II) were calculated by DFT. Then the variations of these parameters are compared to each other to find the properties of the hydrogen bonds in these compounds. To perform the calculations, the neutron diffraction parameters of the crystalline 8-hydroxyquinolinium cation and the 2-carboxy-4,5-dichlorobenzoate anion in (I) and 8- aminoquinolinium cation and the 2-carboxy 4,5-dichlorobenzoate anion in (II) at 130K were obtained from literature including the most HB interacting molecules with the target. The EFG tensors are more sensitive to HB effects rather than the CS tensors.