Peral F, Gallego E
Departamento de Ciencias y Técnicas Fisicoquímicas, U.N.E.D., Senda del Rey, Madrid, Spain.
Spectrochim Acta A Mol Biomol Spectrosc. 2000 Mar;56(4):747-59. doi: 10.1016/s1386-1425(99)00160-2.
The self-association of four heteroaromatic compounds with fused five- and six-membered rings: purine, 6-methylpurine, benzimidazole, and imidazo[1,2-a]pyridine, was studied in aqueous solution at different pH values, by ultraviolet spectroscopy. The variation in molar absorptivity with the concentration of these compounds was measured for the band systems in the mid-ultraviolet region. Hypochromic deviations from the Beer-Lambert law with increasing concentration were found for all compounds. These results were interpreted in terms of self-association processes involving the formation of dimers and, in certain cases, also the formation of polymers. From the fitting of the experimental curves of hypochromic effects, self-association constants for dimerization and polymerization were calculated. The results obtained are discussed in relation to the self-association properties of the building blocks of each compound, studied by us in previous works. The relevance of the position of the nitrogen atoms at the five- and six-membered rings was analyzed to elucidate the nature of the self-association processes, in particular the tendency to polymerization. The values of the calculated self-association constants are discussed in relation to the intermolecular interaction energies of these compounds in aqueous solution.
通过紫外光谱法，在不同pH值的水溶液中研究了四种具有稠合五元环和六元环的杂芳族化合物：嘌呤、6-甲基嘌呤、苯并咪唑和咪唑并[1,2-a]吡啶的自缔合。测量了这些化合物在中紫外区域的能带体系中摩尔吸光率随浓度的变化。发现所有化合物的浓度增加时均出现偏离比尔-朗伯定律的减色现象。这些结果是根据涉及二聚体形成以及在某些情况下聚合物形成的自缔合过程来解释的。通过对减色效应实验曲线的拟合，计算了二聚化和聚合的自缔合常数。将所得结果与我们在先前工作中研究的每种化合物的结构单元的自缔合性质相关联进行讨论。分析了五元环和六元环上氮原子的位置的相关性，以阐明自缔合过程的性质，特别是聚合倾向。将计算得到的自缔合常数的值与这些化合物在水溶液中的分子间相互作用能相关联进行讨论。
