The compound 4,4′-dinitro-2,2′,6,6′-tetracarboxybiphenyl (H₄A) was shown to produce cocrystals and salts with various N-heterocycles such as 4,4′-bipyridylethylene, 4,4′-bipyridine, 4,4′-bipyridylethane, 1,10-phenanthroline, phenazine, and 2-(2-(pyridin-4-yl)vinyl)-1H-imidazo[4,5-c]pyridine in MeOH solvent. Crystal structures of all the complexes were analyzed in terms of protonation–deprotonation in the acid–base systems, hydrogen-bonded synthons, and stacking interactions. The molecule H₄A formed a cocrystal as well as a salt with the coformer 4,4′-bipyridylethylene depending on the concentration of the methanolic solution. Among other coformers, only phenazine was found to form a cocrystal. Various hydrogen-bonded frameworks derived from the structural analyses of the complexes include a one-dimensional chain, two-dimensional herringbone and rectangular grid networks, and three-dimensional pseudodiamondoid network. The cocrystal obtained from the coformer 4,4′-bipyridylethylene was found to be photoreactive to undergo a solid state photodimerization reaction despite the criss-cross arrangement of the olefinic double bonds. Photophysical properties of all the complexes were explored through diffuse reflectance spectroscopy and solid state photoluminescence studies.

中文翻译：

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4,4'-二硝基-2,2'，6,6'-四羧基联苯与N-杂环的共晶体和盐：Criss-Cross对准的烯烃的固态光二聚化和光物理性质

已显示化合物4,4'-二硝基-2,2'，6,6'-四羧基联苯（H ₄ A）与各种N杂环（例如4,4'-联吡啶乙烯，4,4'）共晶和形成盐-联吡啶，4,4'-联吡啶乙烷，1,10-菲咯啉，吩嗪和2-（2-（吡啶-4-基）乙烯基）-1 H-咪唑并[4,5- c ]吡啶在MeOH溶剂中。分析了所有配合物的晶体结构，包括酸碱体系中的质子化-去质子化，氢键合成子和堆积相互作用。分子H ₄ A取决于甲醇溶液的浓度，与共形成剂4,4'-联吡啶基乙烯形成共晶以及盐。在其他共形成剂中，仅发现吩嗪形成共晶体。从配合物的结构分析中得出的各种氢键构架包括一维链，二维人字形和矩形网格网络以及三维伪菱形网络。尽管从烯烃双键的纵横交错排列，发现从共形成剂4,4'-联吡啶基乙烯获得的共晶体具有光反应性以进行固态光二聚反应。通过漫反射光谱和固态光致发光研究探索了所有配合物的光物理性质。