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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Spin chemical control of photoinduced electron-transfer processes in ruthenium(II)-trisbipyridine-based supramolecular triads: 2. The effect of oxygen, sulfur, and selenium as heteroatom in the azine donor
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Spin chemical control of photoinduced electron-transfer processes in ruthenium(II)-trisbipyridine-based supramolecular triads: 2. The effect of oxygen, sulfur, and selenium as heteroatom in the azine donor

机译：基于钌（II）-三联吡啶的超分子三元组中光诱导电子转移过程的自旋化学控制：2.氧，硫和硒作为杂原子在嗪供体中的作用

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Nanosecond time-resolved absorption studies in a magnetic field ranging from 0 to 2.0 T have been performed on a series of covalently linked donor(PXZ)-Ru(bipyridine)(3)-acceptor(diquat) complexes (D-C2+-A(2+)). In the PXZ moiety, the heteroatom (X = O (oxygen), T (sulfur), and S (selenium)) is systematically varied to study spin-orbit coupling effects. On the nanosecond time scale, the first detectable photoinduced electron-transfer product after exciting the chromophore C2+ is the charge-separated (CS) state, D+-C2+-A(+), where an electron of the PXZ moiety, D, has been transferred to the diquat moiety, A(2+). The magnetic-field-dependent kinetic behavior of charge recombination (monoexponential at 0 T progressing to biexponential for all three complexes with increasing field) can be quantitatively modeled by the radical pair relaxation mechanism assuming creation of the CS state with pure triplet spin correlation ((CS)-C-3). Magnetic-field-independent contributions to the rate constant k(r) of T-+/- -> (T-0,S) relaxation are about 4.5 x 10(5) s(-1) for DCA-POZ and -PTZ (due to a vibrational mechanism) and 3.5 x 10(6) s(-1) for DCA-PSZ (due to spin rotational mechanism). Recombination to the singlet ground state is allowed only from the (CS)-C-1 spin level; spin-forbidden recombination from (CS)-C-3 seems negligible even for DCA-PSZ. The field dependence of k(r) (field-dependent recombination) can be decomposed into the contributions of various relaxation mechanisms. For all compounds, the electron spin dipolar coupling relaxation mechanism dominates the field dependence of tau(slow) at fields up to about 100 mT. Spin relaxation due to the g-tensor anisotropy relaxation mechanism accounts for the field dependence of tau(slow) for DCA-PSZ at high fields. For the underlying stochastic process, a very short correlation time of 2 ps has to be assumed, which is tentatively assigned to a flapping motion of the central, nonplanar ring in PSZ. Finally, it has been confirmed by paramagnetic quenching (here Heisenberg exchange) experiments of the magnetic-field effects with TEMPO that all magnetic-field dependencies observed with the present DCA-PSZ systems are indeed due to the magnetic-field dependence of spin relaxation.
机译：已对一系列共价连接的供体（PXZ）-Ru（联吡啶）（3）-受体（敌草快）络合物（D-C2 + -A（ 2+））。在PXZ部分中，杂原子（X = O（氧），T（硫）和S（硒））被系统地改变以研究自旋轨道耦合效应。在纳秒时间尺度上，激发发色团C2 +之后的第一个可检测到的光诱导电子转移产物是电荷分离（CS）状态D + -C2 + -A（+），其中PXZ部分的电子D转移到敌草快部分，A（2+）。假设通过创建具有纯三重态自旋相关性的CS态（（（ CS）-C-3）。对于DCA-POZ和-PTZ，磁场对T-+ /-->（T-0，S）弛豫速率常数k（r）的贡献约为4.5 x 10（5）s（-1） （由于振动机制）和DCA-PSZ的3.5 x 10（6）s（-1）（由于旋转机制）。仅从（CS）-C-1自旋水平允许重组为单重态基态;即使对于DCA-PSZ，（CS）-C-3的自旋禁止重组也可以忽略不计。 k（r）的场依赖性（场依赖性重组）可以分解为各种弛豫机制的贡献。对于所有化合物，在高达约100 mT的电场中，电子自旋偶极耦合弛豫机制主导着tau（slow）的电场依赖性。由于g张量各向异性弛豫机制而引起的自旋弛豫解释了DCA-PSZ在高场下tau（慢）的场依赖性。对于基本的随机过程，必须假设2 ps的非常短的相关时间，并暂时将其分配给PSZ中非平面中心环的拍动。最后，通过使用TEMPO的磁场效应的顺磁淬火（这里为Heisenberg交换）实验已确认，使用本DCA-PSZ系统观察到的所有磁场依赖性确实是由于自旋弛豫的磁场依赖性。

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