3-Quinoline-and 5-isoquinolineboronic acids (3QBA and 5IQBA) were combined with 1-naphthyl and diphenyl phosphate (1NP and DPP) to give three crystalline molecular salts of 1:1 stoichiometric composition, viz., 3QBA-1NP, 5IQBA-1NP and 3QBA-DPP. The products were characterized by elemental analysis, single-crystal X-ray diffraction studies, IR spectroscopy, luminescence spectroscopy and TG-DSC measurements. The analysis of the solid-state structures revealed that the molecular components are linked by strong charge-assisted hydrogen bonds forming heterodimeric synthons of the type B(OH) 2 ··· -O 2 P and N + -H···O(P). In addition, the hydrogen phos- [a] Crystalline solids of compounds 3QBA-1NP, 5IQBA-1NP and 3QBA-DPP were isolated upon combination of the starting reagents in absolute ethanol. The products were characterized by elemental analysis, single-crystal X-ray diffraction (SCXRD) analysis, IR spectroscopy and TG-DSC analysis. In addition, the luminescence properties were explored. 2708 Scheme 1. List of compounds employed for the formation of the molecular salts described in this contribution.
8-Hydroxyquinolin-5-sulfonic acid (8HQSA) was combined with 3-pyridineboronic acid (3PBA) or 4-pyridineboronic acid (4PBA) to give two zwitterionic monoboron complexes in crystalline form. The compounds were characterized by elemental analysis, single-crystal X-ray diffraction studies, and IR, 1H NMR, UV-Visible, and luminescence spectroscopy. The analyses revealed compounds with boron atoms adopting tetrahedral geometry. In the solid state, the molecular components are linked by charge-assisted (B)(O-H···−O(S) and N+-H···O(S) hydrogen bonds aside from C-H···O contacts and π···π interactions, as shown by Hirshfeld surface analyses and 2D fingerprint plots. The luminescence properties were characterized in terms of the emission behavior in solution and the solid state, showing emission in the bluish-green region in solution and large positive solvatofluorochromism, caused by intramolecular charge transfer. According to TD-DFT calculations at the M06-2X/6-31G(d) level of theory simulating an ethanol solvent environment, the emission properties are originated from π-π * and n-π * HOMO-LUMO transitions.
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