Vaidyalingam A, Dutta PK
Department of Chemistry, Ohio State University, Columbus 43210, USA.
Anal Chem. 2000 Nov 1;72(21):5219-24. doi: 10.1021/ac000408e.
The photodecomposition products of Ru(bpy)3(2+) in water, in aqueous buffered solutions and encapsulated in zeolite-Y have been analyzed by chromatography and UV-visible spectroscopy. The chromatographic method is found to be capable of separating species with the same charge but slightly different ligands as well as geometrical isomers. In all the systems investigated, photodecomposition proceeded via photoaquation resulting in the formation of cis- and trans-Ru(bpy)2(OH2)2(2+). In the case of acetate and phthalate buffers, a third species, Ru(bpy)2(L)(OH2)+, where L is the buffer anion, was found to be the dominant product. For a given pH, the extent of decomposition was found to be dependent on both the buffer anion, following the trend, phosphate < acetate << phthalate and buffer concentration. The presence of the electron-transfer quenching agent, N,N'-dimethyl-4,4'-bipyridinium ion in the medium led to a decrease of the photodecomposition and closely followed the quenching efficiency as measured by intensity and lifetime quenching studies. Encapsulation of Ru(bpy)3(2+) in the supercages of zeolite-Y did not lead to a substantial decrease in photodecomposition as compared to an aqueous solution, suggesting that the expected enhanced stability of Ru(bpy)3(2+*) due to the destabilization of 3dd orbitals and the cage effect was being negated by the close proximity and intrazeolite packing of H2O molecules around the Ru center.
通过色谱法和紫外可见光谱法分析了Ru(bpy)3(2+)在水中、水性缓冲溶液中以及封装在Y型沸石中的光分解产物。发现色谱法能够分离电荷相同但配体略有不同的物种以及几何异构体。在所研究的所有体系中，光分解通过光水合作用进行，生成顺式和反式Ru(bpy)2(OH2)2(2+)。在乙酸盐和邻苯二甲酸盐缓冲溶液的情况下，发现第三种物种Ru(bpy)2(L)(OH2)+（其中L为缓冲阴离子）是主要产物。对于给定的pH值，发现分解程度取决于缓冲阴离子，遵循磷酸盐＜乙酸盐＜＜邻苯二甲酸盐的趋势以及缓冲液浓度。介质中电子转移猝灭剂N,N'-二甲基-4,4'-联吡啶鎓离子的存在导致光分解减少，并且紧密遵循通过强度和寿命猝灭研究测量的猝灭效率。与水溶液相比，将Ru(bpy)3(2+)封装在Y型沸石的超笼中并没有导致光分解大幅降低，这表明由于3d轨道不稳定和笼效应预期的Ru(bpy)3(2+*)稳定性增强被Ru中心周围H2O分子的紧密接近和沸石内堆积所抵消。
