De Luca Giovanna, Romeo Andrea, Scolaro Luigi Monsù
Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina, Salita Sperone 31, 98166 Vill. S. Agata, Messina, Italy.
J Phys Chem B. 2005 Apr 21;109(15):7149-58. doi: 10.1021/jp0448797.
The effect of adding various kinds of acids HX (X = Cl, Br, I, CF(3)COO, CF(3)SO(3), TFPB ((3,5-(CF(3))(2)C(6)H(3))(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.
通过联合使用紫外可见吸收光谱、荧光发射光谱和共振光散射（RLS）技术，研究了在二氯甲烷溶液中向同分异构体四（2-吡啶基）卟啉、四（3-吡啶基）卟啉和四（4-吡啶基）卟啉（TpyP(2)、TpyP(3)和TpyP(4)）中添加各种酸HX（X = Cl、Br、I、CF(3)COO、CF(3)SO(3)、TFPB（(3,5-(CF(3))(2)C(6)H(3))(4)B）的效果。实验证据表明，质子化和聚集行为明显依赖于酸和卟啉的性质。一般来说，可以识别出三种不同的趋势：（i）形成完全质子化的物种，随后聚集；（ii）形成四质子化的物种，其聚集，在进一步添加酸时解聚；以及（iii）在庞大的TFPB(-)阴离子的独特情况下，四个吡啶基部分质子化，导致形成四质子化离子对。在所有情况下，质子化物种和由此产生的聚集体表现出明显受抗衡阴离子性质影响的光谱特征。基于氢键、静电相互作用和色散相互作用的相互作用，提出了一种J-聚集模型。聚集过程的动力学控制允许对最终聚集物种的光谱性质进行微调。
