Abstract

The synthesis and structure of a novel ortho-fluoroazobenzene, methyl 4-bromo-3-((2,6-difluorophenyl)diazenyl) benzoate is described. The title molecule crystallizes in the centrocemetric space group P-1 with two rotomer molecules of the title compound in the asymmetric unit. The position of ortho-fluoro azo rings differ between the two rotomers with one molecule having a rotation angle of 4.4° and the other molecule having a rotation angle of 76.9° with respect to the methyl 4-bromobenzoate. Due to the tight packing the pure molecule was not seen to be photoactive. However, in solution the absorption bands in the visible region show a separation of about 20 nm as expected for o-fluoroazobenzene. A comparison to related and previously published co-crystals of substituted azobenzenes are presented.

Graphic Abstract

The structure of a novel ortho-fluoroazobenzene, methyl 4-bromo-3-((2,6-difluorophenyl)diazenyl) benzoate reveals the presence of two crystallographically unique rotomers in the lattice, and although the molecule is photoactive in solution, the close-packed lattice appears to inhibit photo-induced structural reorganization in the crystalline state.

中文翻译：

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光敏4-溴-3-（（2,6-二氟苯基）二氮烯基）苯甲酸甲酯的合成与表征

摘要

描述了新型的邻氟偶氮苯，4-溴-3-（（2,6-二氟苯基）二氮烯基）苯甲酸甲酯的合成和结构。标题分子在中心密度空间群P -1中结晶，标题化合物的两个旋转异构体分子位于不对称单元中。相对于4-溴苯甲酸甲酯，两种分子的旋转异构体之间的邻氟偶氮环的位置不同，一个分子的旋转角为4.4°，另一个分子的旋转角为76.9°。由于紧密堆积，未发现纯分子具有光活性。然而，在溶液中的可见区域的吸收谱带表明约20nm的间隔如预期ö-氟偶氮苯。提出了与相关的和先前发表的取代偶氮苯共晶体的比较。

图形摘要

新型邻氟偶氮苯，4-溴-3-（（2,6-二氟苯基）二氮烯基）苯甲酸甲酯的结构揭示了晶格中存在两种晶体学独特的旋转异构体，尽管该分子在溶液中具有光活性，但紧密的堆积的晶格似乎在结晶状态下抑制了光诱导的结构重组。