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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Explicit solvent DRF INDOs/CIS computations of charge transfer state energetics in a pyrenyldeoxyuridine nucleoside model
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Explicit solvent DRF INDOs/CIS computations of charge transfer state energetics in a pyrenyldeoxyuridine nucleoside model

机译：a基脱氧尿苷核苷模型中电荷转移态高能的显式溶剂DRF INDOs / CIS计算

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In this work we present calculated absorption and emission spectra in acetonitrile (MeCN) solution of N-acetyl-1-aminopyrene (PAAc, a spectroscopic model compound) and N-(1-pyrenyl)-1-methyluracil-5-carboxamide (PAU(Me), a computational model for 5-(N-carboxyl-1-aminopyrenyl)-2'-deoxyuridine (PAdU)). The computational method used-the discrete reaction field approach (DRF)-combines a quantum mechanical (QM) description of the solute (here DFT and INDOs/CIS, i.e., the INDO parametrization for spectroscopy) with a classical, molecular mechanics (MM) description of the solvent molecules. The latter are modeled with point charges representing the permanent charge distribution and polarizabilities to account for many-body interactions among the solute and other solvent molecules. Molecular dynamics is used to sample the degrees of freedom of the solution around several solute conformations each in two electronic excited states. This leads to a large number of solute/solvent configurations from which 800 are selected for each excited state and collected into a single ensemble by means of proper Boltzmann averaging. DRF INDOs/CIS applied to the selected solute/solvent configurations give simulated absorption and emission band spectra-each based on 15200 calculated transitions-that compare well with experimental results. For example, the much broader absorption and emission bands in PAdU compared with PAAc are reproduced, and the simulated emission spectra of PAU(Me) agree well with broad (380-550 nm) charge transfer (CT) emission seen for PAdU in MeCN. The observed multiexponential fluorescence decay profiles for PAdU in different polar solvents are interpreted in terms of solute/solvent conformational heterogeneity here generated in the MD simulations for PAUMe in MeCN. Additionally, the simulations demonstrate the mixing of the forbidden Pycenter dot+/dU(center dot-) CT states with allowed pyrenyl (1)(pi,pi*) states.
机译：在这项工作中，我们介绍了N-乙酰基-1-氨基py（PAAc，光谱模型化合物）和N-（1-吡啶基）-1-甲基尿嘧啶5-羧酰胺（PAU）在乙腈（MeCN）溶液中的吸收光谱和发射光谱（Me），是5-（N-羧基-1-氨基吡啶）-2'-脱氧尿苷（PAdU）的计算模型。所用的计算方法-离散反应场方法（DRF）-将溶质的量子力学（QM）描述（此处为DFT和INDOs / CIS，即用于光谱学的INDO参数化）与经典的分子力学（MM）相结合溶剂分子的描述。后者用表示永久电荷分布和极化率的点电荷进行建模，以说明溶质和其他溶剂分子之间的多体相互作用。分子动力学用于对围绕几种溶质构象的溶液的自由度进行采样，每个溶质构象均处于两个电子激发态。这导致大量的溶质/溶剂构型，从中为每个激发态选择800种溶质/溶剂构型，并通过适当的玻尔兹曼平均将其收集到一个整体中。应用于选定的溶质/溶剂配置的DRF INDO / CIS提供了模拟的吸收和发射谱带-每个基于15200计算的跃迁-与实验结果很好地比较。例如，与PAAc相比，PAdU中的吸收和发射谱带要宽得多，并且模拟的PAU（Me）发射光谱与在MeCN中PAdU看到的宽（380-550 nm）电荷转移（CT）发射非常吻合。根据在MeCN中PAUMe的MD模拟中生成的溶质/溶剂构象异质性来解释在不同极性溶剂中观察到的PAdU的多指数荧光衰减曲线。此外，模拟显示了禁止的Pycenter dot + / dU（center dot-）CT状态与允许的pyr基（1）（pi，pi *）状态的混合。

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