Titi Hatem M, Goldberg Israel
School of Chemistry, Sackler Faculty of Exact Sciences, Tel-Aviv University, Ramat-Aviv, 69978 Tel-Aviv, Israel.
Acta Crystallogr C. 2009 Dec;65(Pt 12):o639-44. doi: 10.1107/S0108270109047519. Epub 2009 Nov 18.
The structure of 1-benzofuran-2,3-dicarboxylic acid (BFDC), C(10)H(6)O(5), (I), exhibits an intramolecular hydrogen bond between one -COOH group and the other, while the second carboxyl function is involved in intermolecular hydrogen bonding to neighbouring species. The latter results in the formation of flat one-dimensional hydrogen-bonded chains in the crystal structure, which are pi-pi stacked along the normal to the plane of the molecular framework, forming a layered structure. 1:1 Cocrystallization of BFDC with pyridine, phenazine and 1,4-phenylenediamine is associated with H-atom transfer from BFDC to the base and charge-assisted hydrogen bonding between the BFDC(-) monoanion and the corresponding ammonium species, while preserving, in all cases, the intramolecular hydrogen bond between the carboxyl and carboxylate functions. The pyridinium 2-carboxylato-1-benzofuran-3-carboxylic acid, C(5)H(6)N(+).C(10)H(5)O(5)(-), (II), and phenazinium 3-carboxylato-1-benzofuran-2-carboxylic acid, C(12)H(9)N(2)(+).C(10)H(5)O(5)(-), (III), adducts form discrete hydrogen-bonded ion-pair entities. In the corresponding crystal structures, the two components are arranged in either segregated or mixed pi-pi stacks, respectively. On the other hand, the structure of 4-aminoanilinium 2-carboxylato-1-benzofuran-3-carboxylic acid, C(6)H(9)N(2)(+).C(10)H(5)O(5)(-), (IV), exhibits an intermolecular hydrogen-bonding network with three-dimensional connectivity. Moreover, this fourth structure exhibits induction of supramolecular chirality by the extended hydrogen bonding, leading to a helical arrangement of the interacting moieties around 2(1) screw axes. The significance of this study is that it presents the first crystallographic characterization of pure BFDC, and manifestation of its cocrystallization with a variety of weakly basic amine molecules. It confirms the tendency of BFDC to preserve its intramolecular hydrogen bond and to prefer a monoanionic form in supramolecular association with other components. The aromaticity of the flat benzofuran residue plays an important role in directing either homo- or heteromolecular pi-pi stacking in the first three structures, while the occurrence of a chiral architecture directed by multiple hydrogen bonding is the dominant feature in the fourth.
1-苯并呋喃-2,3-二羧酸（BFDC），C(10)H(6)O(5)，（I）的结构显示，一个-COOH基团与另一个-COOH基团之间存在分子内氢键，而第二个羧基官能团则参与与相邻分子的分子间氢键作用。后者导致在晶体结构中形成扁平的一维氢键链，这些链沿着垂直于分子骨架平面的方向进行π-π堆积，形成层状结构。BFDC与吡啶、菲嗪和1,4-苯二胺的1:1共结晶与氢原子从BFDC转移到碱以及BFDC（-）单阴离子与相应铵物种之间的电荷辅助氢键有关，同时在所有情况下都保留了羧基和羧酸盐官能团之间的分子内氢键。吡啶鎓2-羧基-1-苯并呋喃-3-羧酸，C(5)H(6)N(+).C(10)H(5)O(5)(-)，（II）和菲嗪鎓3-羧基-1-苯并呋喃-2-羧酸，C(12)H(9)N(2)(+).C(10)H(5)O(5)(-)，加合物形成离散的氢键离子对实体。在相应的晶体结构中，两种组分分别以分离或混合的π-π堆积排列。另一方面，4-氨基苯胺鎓2-羧基-1-苯并呋喃-3-羧酸，C(6)H(9)N(2)(+).C(10)H(5)O(5)(-)，（IV）的结构显示出具有三维连通性的分子间氢键网络。此外，这种第四种结构通过扩展的氢键作用表现出超分子手性的诱导，导致相互作用部分围绕2(1)螺旋轴呈螺旋排列。这项研究的意义在于，它首次对纯BFDC进行了晶体学表征，并展示了其与多种弱碱性胺分子的共结晶现象。它证实了BFDC在与其他组分的超分子缔合中保留其分子内氢键并倾向于单阴离子形式的趋势。扁平苯并呋喃残基的芳香性在前三种结构中对于指导同分子或异分子π-π堆积起着重要作用，而由多重氢键作用引导的手性结构的出现是第四种结构的主要特征。
