Intercomponent Electronic Energy Transfer in Heteropolynuclear Complexes Containing Ruthenium- and Rhenium-Based Chromophores Bridged by an Asymmetric Quaterpyridine Ligand
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- 作者：Rosemary L. Cleary ; Kate J. Byrom ; David A. Bardwell ; John C. Jeffery ; Michael D. Ward ; Giuseppe Calogero ; Nicola Armaroli ; Lucia Flamigni ; and Francesco Barigelletti
- 刊名：Inorganic Chemistry
- 出版年：1997
- 出版时间：June 4, 1997
- 年：1997
- 卷：36
- 期：12
- 页码：2601 - 2609
- 全文大小：337K
- 年卷期：v.36,no.12(June 4, 1997)
- ISSN：1520-510X
文摘
We have prepared the mononuclear complexes[Ru(bpy)2(AB)][PF6]2,[Ru(bpy)(AB)2][PF6]2,and[Ru(AB)3][PF6]2(designated Ru-AB,Ru-AB2, andRu-AB3,respectively) [where bpy is 2,2'-bipyridine and AB is theasymmetricbis(bipyridyl) bridging ligand2,2':3',2'':6'',2'''-quaterpyridine] in which there are one, two, orthree (respectively)bpy-type fragments pendant from the{Ru(bpy)3}2+ core. In everycase the less hindered site A of the ligand ABis coordinated to Ru(II) and the more hindered site B is pendant.Reaction with Re(CO)5Cl affords theheteronuclearcomplexes[Ru(bpy)2{ABRe(CO)3Cl}][PF6]2,[Ru(bpy){ABRe(CO)3Cl}2][PF6]2,and[Ru{ABRe(CO)3Cl}3][PF6]2(designated Ru-ABRe,Ru-ABRe2, andRu-ABRe3,respectively) in which each pendant site B is nowcoordinated to a {Re(CO)3Cl} fragment.Because of the conformational properties of the ABligand, in thetetranuclearRu-ABRe3complex the Ru-based chromophore occupies an internal position in asort of molecularball, the three Re-based groups being located outside.Electrochemical studies show that the pendant{Re(CO)3Cl}fragments exert an electron-withdrawing effect on the{Ru(bpy)3}2+ core such that theRu(II)/Ru(III) redox couplemoves to more positive potentials as the number of pendant{Re(CO)3Cl} fragments increases. Weemployedsteady-state and time-resolved luminescence spectroscopy to investigatethe Re 
Ru intercomponent energytransfer taking place in the mixed-metal complexes and found that Re Ru energy transfer takes place with100% efficiency in all cases. For the tetranuclear complex, it isthus possible to convey a substantial portion ofthe electronic excitation energy from the molecular periphery to thecenter. It is also found that the peripheralRe-containing units exert a shielding effect against luminescencequenching processes at the Ru center by molecularoxygen dissolved in the solvent. During the syntheses, theunexpected byproduct[Ru(AB)(
3-AB)Cl][PF6]wasalso isolated in which one of the AB ligands is coordinatedin a hitherto unseen terdentate mode; this wascrystallographically characterized. Data for[Ru(AB)(3-AB)Cl][PF6]·2MeCN:C44H34ClF6N10PRu;triclinic, P
;a = 10.578(3) Å, b = 14.330(2) Å,c = 14.761(3) Å; 
= 84.56(2)
, 
=70.408(12), 
= 86.03(2); V=2096.8(8) Å3; Z = 2.
Ru intercomponent energytransfer taking place in the mixed-metal complexes and found that Re Ru energy transfer takes place with100% efficiency in all cases. For the tetranuclear complex, it isthus possible to convey a substantial portion ofthe electronic excitation energy from the molecular periphery to thecenter. It is also found that the peripheralRe-containing units exert a shielding effect against luminescencequenching processes at the Ru center by molecularoxygen dissolved in the solvent. During the syntheses, theunexpected byproduct[Ru(AB)(3-AB)Cl][PF6]wasalso isolated in which one of the AB ligands is coordinatedin a hitherto unseen terdentate mode; this wascrystallographically characterized. Data for[Ru(AB)(3-AB)Cl][PF6]·2MeCN:C44H34ClF6N10PRu;triclinic, P;a = 10.578(3) Å, b = 14.330(2) Å,c = 14.761(3) Å; = 84.56(2), =70.408(12), = 86.03(2); V=2096.8(8) Å3; Z = 2.