TRIS(2,2'-BIPYRIDINE)RUTHENIUM(II)-SENSITIZED PHOTO-OXIDATION OF PHENOLS - ENVIRONMENTAL-EFFECTS ON ELECTRON-TRANSFER YIELDS AND KINETICS
TRIS(2,2'-BIPYRIDINE)RUTHENIUM(II)-SENSITIZED PHOTO-OXIDATION OF PHENOLS - ENVIRONMENTAL-EFFECTS ON ELECTRON-TRANSFER YIELDS AND KINETICS
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DOI：
10.1021/ja00390a012
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发表时间：
1982-01-01
影响因子：
15
通讯作者：
DAS, PK
中科院分区：
文献类型：
--
作者：
MIEDLAR, K;DAS, PK
采用激光闪光光解（337.1 nm）结合动态吸收发射分光光度法研究了一系列酚类物质对三(2,2''-联吡啶)钌(II)的光还原反应，重点研究了溶剂、温度和离子强度对电子转移动力学和产率的影响。激发态猝灭速率常数(kq)在1×的范围内。 106-5 次。取代酚根离子（pH 12.7）为 109 M-1 s-1，与 Hammett σ+ 值以及氧化电位密切相关。 RT ln kq'' 与.**GRAPHIC** 的关系图。斜率为 -0.5，kq'' 是针对初始扩散过程校正的淬火速率常数。在水溶液中使用 p-CH3O-C6H4O-、C6H5O- 和 p-COO--C6H4O- 作为猝灭剂的情况下，kq 的阿伦尼乌斯图在 0°-80°C 的温度范围内呈线性。 C 并分别给出 4.2、8.1 和 12.8 kcal/mol 作为表观活化能。以对甲氧基苯酚离子和对甲氧基-N,N-二甲基苯胺作为猝灭剂，当溶剂从水改为95%乙醇或95%丙酮（均为水溶液）时，kq增加；然而，这种增加并不是单调的，从 kq 在中间溶剂组成处经历最小值可以明显看出。水溶液中（pH 12.7）各种酚根离子的电子转移产率（η）在 0.3-1.0 范围内。正如用对甲氧基苯酚离子和对甲氧基-N,N-二甲基苯胺观察到的，η。在高温下、在富含非水组分（丙酮或乙醇）的水性溶剂系统中以及在较低离子强度下表现出增加的趋势。还报道了三(2,2''-联吡啶)钌(II)在水溶液中在230-800 nm光谱范围内的激发态吸收光谱（三重态-三重态），除了在短波长（240-400 nm）下具有突出的3波段特征外，在长波长（500-800 nm）下显示出小但不可忽略的光谱吸收。
Laser flash photolysis (337.1 nm) combined with kinetic absorption-emission spectrophotometry was used to study the photoreduction of tris(2,2''-bipyridine)ruthenium(II) by a series of phenols with special emphasis on the effects of solvent, temperature, and ionic strength on electron transfer kinetics and yields. The excited-state quenching rate constants (kq) are in the range 1 .times. 106-5 .times. 109 M-1 s-1 for substituted phenolate ions (at pH 12.7) and correlate well with Hammett .sigma.+ values as well as with oxidation potentials. The plot of RT ln kq'' against .**GRAPHIC**. has a slope of -0.5, kq'' being the quenching rate constant corrected for the initial diffusional process. Arrhenius plots for kq in the cases of p-CH3O-C6H4O-, C6H5O-, and p-COO--C6H4O- as quenchers in aqueous solutions are linear in the temperature range 0.degree.-80.degree. C and give 4.2, 8.1, and 12.8 kcal/mol, respectively, as apparent activation energies. With p-methoxyphenolate ion and p-methoxy-N,N-dimethylaniline as quenchers, kq increases on changing solvent from water to 95% ethanol or 95% acetone (both aqueous); this increase, however, is not monotonous as evident from kq going through a minimum at intermediate solvent compositions. The electron transfer yields (.eta.) are in the range 0.3-1.0 for various phenolate ions in aqueous solutions (at pH 12.7). As observed with p-methoxyphenolate ion and p-methoxy-N,N-dimethylaniline, .eta. exhibits an increasing trend at elevated temperatures, in aqueous solvent systems richer in the nonaqueous component (acetone or ethanol), and at lower ionic strengths. Also reported is the excited-state absorption spectrum (triplet-triplet) of tris(2,2''-bipyridine)ruthenium(II) in aqueous solution in the spectral region 230-800 nm showing small but nonnegligible spectral absorption at longwave lengths (500-800 nm) in addition to a prominent 3-band feature at short wavelengths (240-400 nm).