Aggregation behavior of water soluble bis(benzothiazolylidene)squaraine derivatives in aqueous media
Aggregation behavior of water soluble bis(benzothiazolylidene)squaraine derivatives in aqueous media
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DOI：
10.1021/jp961885x
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发表时间：
1996-10-24
影响因子：
--
通讯作者：
George, MV
中科院分区：
文献类型：
--
作者：
Das, S;Thomas, KG;George, MV
合成了双[3-（对羧基苄基）苯并噻唑-2-乙基]squaraine （Sq1）和双[3-（羧基甲基）苯并噻唑-2-乙基]squaraine （Sq2）两种新型水溶性方卡因染料，并对其光物理性质进行了表征。Sql和Sq2在水中形成二聚体聚集体，其吸收带蓝移到单体形式。在D2O中比在H2O中更容易形成聚集体。在低浓度(（3 × 10(-4) M）聚乙烯吡咯烷酮（PVP）的存在下，观察到Sql的聚集形成增强，而Sq2的聚集形成不受影响。较高的PVP浓度（bbb3 × 10(-4) M）导致聚集体的破坏和新物种的形成，其吸收带红移到相应单体的吸收带上。这些相互作用的性质已经被研究过了。本文认为，显色单元之间的疏水相互作用是水中h型（三明治）聚集体形成的主要驱动力。红移物种归因于单体形式，微封装在PVP提供的疏水环境中。皮秒激光闪光对聚集体的光解研究清楚地表明，聚集体从激发态分裂成激发态-基态单体对，并迅速重组为基态二聚体。
Two new water soluble squaraine dyes, bis[3-(p-carboxybenzyl)benzothiazol-2-ylidene]squaraine (Sq1) and bis[3-(carboxymethyl)benzothiazol-2-ylidene] squaraine (Sq2), have been synthesized and their photophysical properties have been characterized. Sql and Sq2 form dimer aggregates in water that have absorption bands blue-shifted to those of the monomeric forms. Aggregate formation is more preferred in D2O than in H2O. In the presence of low concentrations ((3 x 10(-4) M) of poly(vinylpyrrolidone) (PVP), enhancement in aggregate formation of Sql is observed, whereas that of Sq2 remains unaffected. Higher concentration (>3 x 10(-4) M) of PVP leads to the disruption of the aggregate and formation of a new species with absorption bands red-shifted to those of the corresponding monomers. The nature of these interactions has been investigated. It is proposed that hydrophobic interaction between the chromophoric units is the major driving force for the formation of the H-type (sandwich) aggregates in water. The red-shifted species are attributed to the monomeric forms, microencapsulated in a hydrophobic environment provided by PVP. Picosecond laser flash photolysis studies of the aggregates show clear evidence for the breakup of the aggregate from the excited state to yield an excited state-ground state monomer pair that rapidly recombines to reform the ground state dimer.