Schmidt Johann, Schmidt Ralf, Würthner Frank
Universität Würzburg, Institut für Organische Chemie, Am Hubland, 97074 Würzburg, Germany.
J Org Chem. 2008 Aug 15;73(16):6355-62. doi: 10.1021/jo801083b. Epub 2008 Jul 22.
A merocyanine dye equipped with a Hamilton-receptor unit has been synthesized that enables strong noncovalent binding of other merocyanine dyes bearing barbituric acid acceptor groups by six hydrogen bonds. NMR and UV/vis titration experiments in toluene, chloroform, dichloromethane, dioxane, and THF provide evidence for the formation of 1:1 complexes even in the dipolar solvents. An enhanced binding strength is observed for the more dipolar merocyanine dyes in the head-to-tail assembly structure with binding constants up to >10 (8) M (-1) in toluene. In the present bimolecular complexes two merocyanine chromophores are assembled in a head-to-tail fashion that affords increased dipole moments as demanded for efficient electric field induced poling processes in nonlinear optical and photorefractive polymeric hosts. The solvent dependency of the binding constants for various barbituric acid dye-Hamilton receptor complexes as well as a perylene imide-melamine complex reveals linear free energy relationships (LFER) that allow for an estimation of binding constants larger than 10 (12) M (-1) for Hamilton receptor organized head-to-tail merocyanine bimolecular complexes in aliphatic solvents. It is suggested that such LFER are valuable tools for the estimation of binding constants in solvents where experimental binding constants cannot be determined because of solubility or spectroscopic problems.
一种配备汉密尔顿受体单元的部花青染料已被合成，它能够通过六个氢键与带有巴比妥酸受体基团的其他部花青染料形成强非共价键结合。在甲苯、氯仿、二氯甲烷、二氧六环和四氢呋喃中进行的核磁共振和紫外/可见滴定实验证明，即使在偶极溶剂中也能形成1:1的配合物。对于在头对头组装结构中偶极更强的部花青染料，观察到结合强度增强，在甲苯中的结合常数高达>10(8)M(-1)。在目前的双分子配合物中，两个部花青发色团以头对头的方式组装，这为非线性光学和光折变聚合物主体中高效电场诱导极化过程所需的偶极矩增加提供了条件。各种巴比妥酸染料-汉密尔顿受体配合物以及苝酰亚胺-三聚氰胺配合物的结合常数对溶剂的依赖性揭示了线性自由能关系(LFER)，这使得能够估计在脂肪族溶剂中汉密尔顿受体组织的头对头部花青双分子配合物的结合常数大于10(12)M(-1)。有人认为，这种LFER是估计由于溶解度或光谱问题无法确定实验结合常数的溶剂中结合常数的有价值工具。
