Proton-Coupled Electron Transfer of a Pd(II) Hydroxyporphycene Complex
Proton-Coupled Electron Transfer of a Pd(II) Hydroxyporphycene Complex
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Pd(II) 羟基卟啉配合物的质子耦合电子转移
DOI：
10.1007/s11164-012-0640-8
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
and Yoshio Hisaeda
中科院分区：
文献类型：
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作者：
Toru Okawara;Masaaki Abe;Hisashi Shimakoshi;and Yoshio Hisaeda
合成并表征了 Pd(II) 配合物 Pd(TPrPc-OH) (1, TprPc-OH = 9-羟基-2,7,12,17-四丙基卟啉二价阴离子)。 1 H NMR 光谱显示化合物 1 在溶液中以烯醇形式存在。添加乙醇-d6 后，1 中羟基的氢原子被氘交换。紫外-可见光谱显示，与乙酰氧基衍生物 Pd(TPrPc-OAc) (2, TPrPc-OAc = 9-acetoxy-2,7,12,17-tetrapropylporphycenato dianion) 相比，THF 中 1 的 Q 带发生红移。通过紫外可见滴定实验测定1中羟基的pKa值为10.56。 THF 和 Britton-Robinson 缓冲水溶液混合物中的 1 的循环伏安图显示，在 pH 值范围为 2.7 至 10.5 的氧化过程中，存在单电子和单质子耦合转移，这一点通过 pH 变化实验和 Pourbaix 图进行了识别。瞬态吸收光谱表明，在 532 nm 脉冲激光照射下，从 1 的三重激发态到 2,3,5,6-四甲基-1,4-苯醌（duroquinone，DQ）发生了电子转移反应。在 Ni 类似物 Ni(TPrPc-OH) 和 DQ 之间没有观察到这种分子间光诱导电子转移反应。反应速率常数 kq 表明动力学同位素效应，kq(H)/kq(D)= 1.7，支持这样的观点：从 1 到 DQ 的激发态电子转移伴随着质子转移。
A Pd(II) complex, Pd(TPrPc-OH) (1, TPrPc-OH = 9-hydroxy-2,7,12,17-tetrapropylporphycenato dianion), has been synthesized and characterized.1H NMR spectroscopy revealed that compound1exists as itsenolform in solution. The H atom of the hydroxy group in1was exchanged with deuterium on addition of ethanol-d6. UV–visible spectra showed a red shift of the Q band of1in THF compared with that of the acetoxy derivative Pd(TPrPc-OAc) (2, TPrPc-OAc = 9-acetoxy-2,7,12,17-tetrapropylporphycenato dianion). The pKavalue of the hydroxy group in1was determined, by means of a UV–visible titration experiment, to be 10.56. A cyclic voltammogram of1in a mixture of THF and Britton–Robinson buffered aqueous solution revealed one-electron and one-proton coupled transfer in the oxidation process in the pH range from 2.7 to 10.5, which was identified by pH-varying experiments and the Pourbaix diagram. Transient absorption spectroscopy revealed that an electron-transfer reaction occurred from the triplet excited-state of1to 2,3,5,6-tetramethyl-1,4-benzoquinone (duroquinone, DQ) upon pulse laser irradiation at 532 nm. Such an intermolecular photoinduced electron-transfer reaction was not observed between the Ni analog, Ni(TPrPc-OH), and DQ. The reaction rate constant,kq, was indicative of a kinetic isotope effect withkq(H)/kq(D)= 1.7, supporting the belief that the exited-state electron transfer from1to DQ is accompanied by proton transfer.