Spectra, equilibrium and photoredox chemistry of tri- and tetraiodoplumbate(II) complexes in acetonitrile
Spectra, equilibrium and photoredox chemistry of tri- and tetraiodoplumbate(II) complexes in acetonitrile
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DOI：
10.1016/s1010-6030(98)00214-7
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发表时间：
1998-04-15
影响因子：
4.3
通讯作者：
Miko, I
中科院分区：
文献类型：
--
作者：
Horvath, O;Miko, I
在乙腈(K-4 = 27 +/- 4 dm（3) mol(-1)）中测定了动力学不稳定的PbI42-配合物的逐步形成常数。三、四碘铅酸盐（II）配合物吸收光谱中的最低能带是由配体到金属的电荷转移跃迁引起的。这些配合物在溶液中的光解作用导致形成Pb(I)和I或I-2（-）作为初级产物。在355 nm激发下，两种配合物的量子产率均为0.10 +/- 0.005。在空气饱和体系中，由于对带负电荷的反应物的排斥力不同，PbI3-配合物（Phi = 0.026 +/- 0.002和Phi(4) = 0.010 +/- 0.004）的整体反应效率（最终产物为I-3(-)）高于PbI42-配合物(λ (irr) = 366 nm, C-Pb(II) = 1 × 10（-4) mol dm(-3)）。总量子产率主要由初级产物的竞争暗反应决定，主要是由I-2（-）的竞争暗反应决定。该反应机制的一个关键步骤是I-2（-）中间体与基态铅（II）配合物之间的反应，反应速率常数分别为3.4 +/- 1.1 x 10(7) dm(3) mol(-1) s（-1）和7.0 +/- 2.0 x 10(7) dm(3) mol(-1) s(-1)， PbI3-为37和94分摩尔百分比。(C) 1998 Elsevier Science S.A.版权所有
The stepwise formation constant of the kinetically labile PbI42- complex was determined in acetonitrile (K-4 = 27 +/- 4 dm(3) mol(-1)). The lowest-energy bands in the absorption spectra of the tri-and tetraiodoplumbate( II) complexes are attributed to ligand-to-metal charge transfer transitions. Photolysis of these complexes in solution results in the formation of Pb(I) and I or I-2(-) as primary products. The quantum yield of this reaction is 0.10 +/- 0.005 for both complexes at 355-nm excitation. The efficiency of the overall reaction (with the formation of I-3(-) as end product) is higher for the PbI3- than for the PbI42- complexes (Phi = 0.026 +/- 0.002 and Phi(4) = 0.010 +/- 0.004) in air-saturated system, lambda(irr) = 366 nm, C-Pb(II) = 1 x 10(-4) mol dm(-3)) due to the different repulsion towards the negatively charged reactants. The overall quantum yield is essentially determined by the competitive dark reactions of the primary products, mostly by those of I-2(-). One key step in the mechanism is the reaction between the I-2(-) intermediate and the ground-state lead(II) complexes, with rate constants of 3.4 +/- 1.1 x 10(7) dm(3) mol(-1) s(-1) and 7.0 +/- 2.0 x 10(7) dm(3) mol(-1) s(-1) at 37 and 94 partial molar percentages of PbI3-, respectively. (C) 1998 Elsevier Science S.A. All rights reserved.