Internal heavy atom effects in phenothiazinium dyes: enhancement of intersystem crossing via vibronic spin-orbit coupling.
Internal heavy atom effects in phenothiazinium dyes: enhancement of intersystem crossing via vibronic spin-orbit coupling.
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DOI：
10.1039/c5cp00194c
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发表时间：
2015-04
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影响因子：
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通讯作者：
Angela Rodríguez-Serrano;Vidisha Rai-Constapel;M. Daza;M. Doerr;C. Marian
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文献类型：
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作者：
Angela Rodríguez-Serrano;Vidisha Rai-Constapel;M. Daza;M. Doerr;C. Marian
用高水平量子力学方法研究了噻吩环内硫原子被氧（oxorylene）和硒（selenine）取代对体系间交叉（ISC）效率的影响。ISC速率常数显着增加时，从O到硒，而荧光速率常数保持不变。对于这三种染料，所有可进入的ISC通道都是由ππ* 态之间的振动自旋轨道耦合（SOC）驱动的。的地面和低洼的激发态之间的相互作用进行了研究，以确定占主导地位的弛豫途径。在氧化铯中，在水中光激发后弛豫到基态的过程基本上是通过从S1（πHπL*）亮态（kF = 2.10 × 10（8）s（-1））发出荧光进行的，这与高的实验荧光量子产率一致。在噻托溴铵水溶液中，ISC速率常数（kISC = 1 × 10（9）s（-1））比荧光速率常数（kF = 1.66 × 10（8）s（-1））高一个数量级，这与噻托溴铵在水溶液中观察到的高三重态量子产率（λ T = 0.53）相一致。由于硒中的电子振动SOC较强，ISC速率非常高（kISC = 10（10）s（-1）），并且比荧光（kF = 1.59 × 10（8）s（-1））快得多。这表明硒基染料是非常有效的三重态光敏剂。
The effect of substituting the intra-cyclic sulphur of thionine by oxygen (oxonine) and selenium (selenine) on the intersystem crossing (ISC) efficiency has been studied using high level quantum mechanical methods. The ISC rate constants are considerably increased when going from O towards Se while the fluorescence rate constants remain unchanged. For the three dyes, all accessible ISC channels are driven by vibronic spin-orbit coupling (SOC) between ππ* states. The interplay between the ground and low-lying excited states has been investigated in order to determine the dominant relaxation pathways. In oxonine the relaxation to the ground state after photoexcitation in water proceeds essentially via fluorescence from the S1(πHπL*) bright state (kF = 2.10 × 10(8) s(-1)), in agreement with the high experimental fluorescence quantum yield. In aqueous solution of thionine, the ISC rate constant (kISC ∼ 1 × 10(9) s(-1)) is one order of magnitude higher than fluorescence (kF = 1.66 × 10(8) s(-1)) which is consistent with its high triplet quantum yield observed in water (ϕT = 0.53). Due to a stronger vibronic SOC in selenine, the ISC rate is very high (kISC ∼ 10(10) s(-1)) and much faster than fluorescence (kF = 1.59 × 10(8) s(-1)). This suggests selenine-based dyes as very efficient triplet photosensitizers.