Design, synthesis, and characterization of pyridine-containing organic crystals with different substitution positions using solvothermal method

Abstract

The organic crystals of Tröger's base (TB) analogs with ortho-/meta-substituted terminal pyridine units, 2,8-(6H,12H-5,11-methanodibenzo[b,f]diazocineylene)-di(o-ethenylpyridine) (TBOP) and 2,8-(6H,12H-5,11-methanodibenzo[b,f]diazocineylene)-di(m-ethenylpyridine) (TBMP), were prepared using solvothermal method. By alternating the solution system and ratio, not only the TBOP and TBMP crystals but also the central-methylene-removed 5,6,11,12-tetrahydro-2,8-dimethylphenhomazine-di(o-ethenyl-N-pyridine) (PHZOP) and 5,6,11,12-tetrahydro-2,8-dimethylphenhomazine-di(m-ethenyl-N-pyridine) (PHZMP) crystals could be obtained from TBOP and TBMP. Furthermore, single-crystal XRD, ¹H NMR, ¹³C NMR, fluorescence spectrometry, combined with Hirshfeld surface calculation, were performed to analyze the relationship between crystal structures and photophysical properties. Since the pyridine unit can only act as a hydrogen bond acceptor in the crystal packing process, the competition and the synergic effects between the pyridine H-acceptor and other intermolecular interaction sites caused by the small alteration of N-substitution lead to significant changes in crystal structures and photophysical properties.