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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Time-Resolved Fluorescence Study on the Pressure-Induced Viscosity Dependence of Exciplex Formation in Liquid Solution
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Time-Resolved Fluorescence Study on the Pressure-Induced Viscosity Dependence of Exciplex Formation in Liquid Solution

机译：溶液中激基形成的压力诱导粘度相关性的时间分辨荧光研究

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摘要

The contribution of diffusion to the exciplex formation of the 1, 2-benzanthracene (BZAN)/dimethylaniline (DMA) and pyrene (PY)/DMA systems in methycyclohexane at pressures up to 400 MPa was investigated. That rate constant, k_3, for the exciplex formation, which was determined by the analysis of the rise and decay curve of the exciplex emission, decreased significantly with increasing pressure. The apparent activation volume for k_3, ΔV_3~≠, was 14.9 and 18.1 cm~3/mol for BZAN/DMA and PY/DMA, respectively, For comparison, the rate constant, k_q, for the fluorescence quenching by carbon tetrabromide (CBr_4) of BZAN and PY that is believed to be fully diffusion-controlled was also measured as a function of pressure. The apparent activation volume for k_q, ΔV_q~≠, was 17.9 and 20.1 cm~3/mol for BZAN/CBr_4 and PY/CBr_4, respectively. These results are interpreted by assuming an encounter complex formed between the donor and acceptor pairs, and it was concluded that the exciplex formation reaction studied in this work is not fully diffusion controlled but competes with a diffusion process of the donor and acceptor molecules that is expressed by a modified Debye equation. It was also concluded that the quenching by CBr_4 is not fully diffusion controlled at the lower pressure range. The bimolecular rate constant, k_(bim) (=K_cK_(diff)/K_(-diff)), for the exciplex formation was estimated to be 1.5 * 10~(10) M~(-1)s~(-1) for BZAN/DMA and 1.9 * 10~(10) M~(-1)s~(-1) for PY/DMA. The activation volumes for the various rate processes also are discussed.
机译：研究了甲基环己烷中压力高达400 MPa时扩散对1,2-苯并蒽（BZAN）/二甲基苯胺（DMA）和pyr（PY）/ DMA系统的激基复合物形成的贡献。通过分析激基复合物发射的上升和衰减曲线确定的激基复合物形成的速率常数k_3，随着压力的增加而显着降低。对于BZAN / DMA和PY / DMA，k_3的表观活化体积为ΔV_3〜≠，分别为14.9和18.1 cm〜3 / mol。为了进行比较，用四溴化碳（CBr_4）进行荧光猝灭的速率常数k_q。还测量了被认为是完全扩散控制的BZAN和PY的最大压力，它是压力的函数。对于BZAN / CBr_4和PY / CBr_4，k_q的表观活化体积为ΔV_q_≠，分别为17.9和20.1 cm〜3 / mol。通过假定供体和受体对之间形成了相遇复合物来解释这些结果，并且得出的结论是，这项工作中研究的激基复合物形成反应不是完全受扩散控制的，而是与表达的供体和受体分子的扩散过程竞争通过修改的德拜方程式还得出结论，在较低的压力范围内，通过CBr_4进行的淬灭并未完全扩散控制。激基复合物形成的双分子速率常数k_（bim）（= K_cK_（diff）/ K _（-diff））估计为1.5 * 10〜（10）M〜（-1）s〜（-1）对于BZAN / DMA，PY / DMA为1.9 * 10〜（10）M〜（-1）s〜（-1）。还讨论了各种费率过程的激活量。

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