Role of counteranions in acid-induced aggregation of isomeric tetrapyridylporphyrins in organic solvents
Role of counteranions in acid-induced aggregation of isomeric tetrapyridylporphyrins in organic solvents
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DOI：
10.1021/jp0448797
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发表时间：
2005-04-21
影响因子：
3.3
通讯作者：
Scolaro, LM
中科院分区：
文献类型：
--
作者：
De Luca, G;Romeo, A;Scolaro, LM
添加不同种类的酸HX（X = Cl，Br，I，CF 3COO，CF 3SO 3，TFP B（（3，5-（CF 3）（2）C6 H3）（4）B）到同分异构四四（2-吡啶基）卟啉（3-吡啶基）卟啉，和用紫外维斯吸收光谱法研究了4-吡啶基卟啉（TpyP（2），TpyP（3），TpyP（4））在二氯甲烷溶液中的吸收光谱，荧光发射和共振光散射（RLS）技术。实验证据表明，质子化和聚集行为对酸和卟啉的性质有明显的依赖性。一般来说，可以识别三种不同的趋势：（i）形成完全质子化的物质，随后聚集;（ii）形成四质子化的物质，其聚集，并且在进一步添加酸时解聚;和（iii）四个吡啶基部分的质子化，在大体积TFPB-阴离子的独特情况下，导致四质子化的离子对。在所有情况下，质子化的物种和由此产生的聚集体表现出的光谱特征，显着影响的抗衡阴离子的性质。J-聚集的模型已被提出的基础上的相互作用的氢键，静电相互作用，和分散的相互作用。聚集过程的动力学控制允许对最终聚集物质的光谱性质进行微调。
The effect of adding various kinds of acids HX (X = Cl, Br, I, CF3COO, CF3SO3, TFPB ((3,5-(CF3)(2)C6H3)(4)B) to isomeric tetra(2-pyridyl)porphyrin, tetra(3-pyridyl)porphyrin, and tetra(4-pyridyl)porphyrin (TpyP(2), TpyP(3), and TpyP(4)) in dichloromethane solution has been investigated through the combined use of UV/ vis absorption, fluorescence emission, and resonance light scattering (RLS) techniques. The experimental evidence points to a marked dependence of the protonation and aggregation behavior on the nature of both acids and porphyrins. In general, three different trends can be recognized: (i) formation of a fully protonated species, followed by aggregation; (ii) formation of a tetraprotonated species, which aggregates and, on further addition of acid, disaggregates; and (iii) protonation of the four pyridyl moieties, leading to a tetraprotonated ion pair, in the unique case of the bulky TFPB- anion. In all cases, the protonated species and the resulting aggregates exhibit spectroscopic features that are markedly influenced by the nature of the counteranions. A model for J-aggregation has been proposed on the basis of an interplay of hydrogen bonding, electrostatic interactions, and dispersive interactions. Kinetic control of the aggregation process allows for a fine-tuning of the spectroscopic properties of the final aggregated species.