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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Stark Spectroscopy of Size-Selected Helical H-Aggregates of a Cyanine Dye Templated by Duplex DNA. Effect of Exciton Coupling on Electronic Polarizabilities
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Stark Spectroscopy of Size-Selected Helical H-Aggregates of a Cyanine Dye Templated by Duplex DNA. Effect of Exciton Coupling on Electronic Polarizabilities

机译：通过双链DNA模板化的花青染料的大小选择的螺旋H-聚集体的Stark光谱。激子耦合对电子极化率的影响

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Stark spectroscopy (electroabsorption) is used to study the variation of electronic properties with the size of helical H-aggregates that are formed by the spontaneous noncovalent assembly of co-facial dimers of the cyanine dye (DiSC_2(5)) into the minor groove of double-helical DNA. The unique and important property of these aggregates, first synthesized and characterized by Armitage and co-workers (J. Am. Chem. Soc. 1999, 121, 2987), is that their size is controlled by the properties of the DNA template. Specifically, the length of the aggregate formed is determined by the length of the DNA template and its width along the π stacking dimension is restricted to that of the dye dimer due to steric constraints in the minor groove. Results for aggregates consisting of 1, 2, 5, and ～35 adjacent dimers bound to DNA are presented here. The absorption maxima of these species exhibit a large blue shift (1750 cm~(-1)) from that of the monomer due to the face-to-face interactions within the dimers. Relatively weak (330-650 cm~(-1)) secondary splittings are also seen that arise from end-to-end interactions between adjacent dimers on the chain. The average change in polarizability to excitation (<Δα_=>) is found to double when two dyes form a stacked dimer whereas no further increase in <Δα_=> is seen as the chain length is increased. Semiempirical (INDO-SCI) calculations yield exciton coupling energies that are consistent with experiment. However, <Δα_=> is predicted to increase toward more positive values on dimerization while the reverse trend is seen experimentally. Nonetheless, both experiment and theory find that <Δα_=> is unaffected by higher aggregation.
机译：斯塔克光谱法（电吸收）用于研究电子性能随花菁染料（DiSC_2（5））的共面二聚体自发地非共价组装成H的小槽而形成的螺旋H聚集体的大小的变化。双螺旋DNA。这些聚集体的独特而重要的性质是首先由Armitage及其同事合成和表征的（J. Am。Chem。Soc。1999，121，2987），其大小受DNA模板性质的控制。具体地，形成的聚集体的长度由DNA模板的长度决定，并且由于小槽中的空间限制，其沿着π堆叠尺寸的宽度被限制为染料二聚体的宽度。本文介绍了由1、2、5和〜35个与DNA结合的相邻二聚体组成的聚集体的结果。由于二聚体之间的面对面相互作用，这些物质的吸收最大值显示出与单体相比最大的蓝移（1750 cm〜（-1））。还可以看到相对较弱的（330-650 cm〜（-1））二次分裂是由链上相邻二聚体之间的端到端相互作用引起的。当两种染料形成一个堆叠的二聚体时，发现激发极化率的平均变化（<Δα_ =>）增加了一倍，而随着链长的增加，<Δα_ =>的进一步增加没有看到。半经验（INDO-SCI）计算得出的激子耦合能与实验一致。但是，预测<Δα_ =>会在二聚化时朝更正值增加，而在实验中观察到相反的趋势。尽管如此，实验和理论均发现<Δα_ =>不受较高聚集的影响。

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