The first betaineâmineral acid complex of 3â:â2 stoichiometry, as well as a 1â:â1 complex common for this class of compounds, has been obtained. Crystalline [di-(3-trimethylammonium-benzoic acid)â(3-trimethylammonium-benzoate)]diiodide (1) is the only betaineâmineral acid 3â:â2 complex obtained so far. Two concomitant polymorphs of this 3â:â2 complex, 1-I and 1-II, have been isolated and characterized by X-ray diffraction and FTIR spectroscopy. Polymorphs 1-I, of monoclinic space group P21/c, and 1-II, of orthorhombic space group Pccn, have very similar lattices and aggregates of one zwitterionic molecule and two cations OâHâ¯O bonded into a 3-membered catemeric carboxylâcarboxylateâcarboxyl interval, but polymorph 1-II dissolves better in methanol than 1-I. Alternative hypothetical aggregates of 3-trimethylammonium-benzoate hydroiodide 1â:â1, 2â:â1 and 3â:â2 complexes optimized at the B3LYP/6-31G(d,p) level of theory suggest that the betaine-to-acid 3â:â2 stoichiometry is favoured at the stage of small cluster aggregation and not due to the complex crystal packing preferences.
我们首次获得了3:â2配比的
甜菜碱矿物酸复合物,以及该类化合物常见的1:â1复合物。晶体[二-(3-三甲基
铵-
苯甲酸)-(3-三甲基
铵-
苯甲酸)]二
碘化物(1)是迄今为止获得的唯一一种
甜菜碱-矿物质酸 3:â2 复合物。通过 X 射线衍射和傅立叶变换红外光谱分析,我们分离出了这种 3:â2 复合物的两种同系多晶体,即 1-I 和 1-II。单斜空间群 P21/c 的多晶体 1-I 和正交空间群 Pccn 的多晶体 1-II,具有非常相似的晶格和由一个齐聚分子和两个阳离子 OâHâ¯O 组成的聚合体,它们键合在一个 3 元
邻苯二甲酸酯羧基间,但多晶体 1-II 在
甲醇中的溶解性比 1-I 好。根据 B3LYP/6-31G(d,p)理论
水平优化的 3-三甲基
苯甲酸铵氢
碘化物 1â:â1、2â:â1 和 3â:â2 复合物的替代假定聚集体表明,
甜菜碱-酸 3â:â2 的
化学计量在小聚集体聚集阶段更受青睐,而不是由于复合物晶体堆积的偏好。