Ground and excited state dynamics of new dinuclear ruthenium complexes: NMR, UV-Vis, IR, electrochemical, photophysical characterization, and theoretical study of Ru(bpy)₂(渭-dpp)Ru(CN-X)₄ⁿ⁺ complexes

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• 作者：Margit Ková ; cs^a ; ^{makovacs@almos.vein.hu} ; Gá ; bor Szalontai^a ; Gyö ; rgy Lendvay^a ; ^b ; Gü ; nter Grampp^c ; Attila Horvá ; th^a ; ^{attila@vegic.uni-pannon.hu} ; ^{attila@vegic.vein.hu}
• 关键词：Ruthenium(II) ; Binuclear complexes ; Structure ; Isomers ; Characterization
• 刊名：Inorganica Chimica Acta
• 出版年：2012
• 期刊代码：40_00201693
• 类别：ch
• 出版时间：30 May, 2012
• 卷：387
• 期：Complete
• 页码：261-270
• 文件大小：729 K

摘要

Two novel binuclear complexes of ruthenium(II) have been synthesized and characterized by various spectroscopic (NMR, IR, UV-Vis absorption and emission) and electrochemical methods. Extensive and detailed NMR studies of [(bpy)₂Ru(渭-dpp)Ru(CN)₄] 1 and [(bpy)₂Ru(渭-dpp)Ru(CNCH₃)₄]⁴⁺ 2 complexes have revealed a dynamic equilibrium between the stereo isomers of the ground-state complexes. Small energy difference between the two isomers of 1 has been estimated using NMR data (2.7 kJ mol^鈭?) and by quantum chemistry calculations (4.7 kJ mol^鈭?). The relatively broad lowest energy absorption band appearing in the visible range is assigned as overlapping metal-to-ligand charge-transfer (MLCT) d蟺(Ru)_A 鈫?/strong> 蟺^{鈭?/sup>(渭-dpp) (MLCT_1A) and d蟺(Ru)_B 鈫?/strong> 蟺鈭?/sup>(渭-dpp) (MLCT_1B) transitions. The MLCT bands of complex 1 are solvatochromic (e.g. the lowest energy MLCT₁ band shifts from 506 to 540 nm upon changing the solvent from water to MeOH), while the same band of the complex 2 is not sensitive to the solvent nature. The luminescence properties of the excited 1 and 2 complexes are significantly different: (i) a rather small blue shift of the emission band (623 cm鈭?) is observed when the luminescence of complex 1 is detected at 77 K in rigid matrix instead of at ambient temperature in liquid phase. This blue shift is considerably larger (1923 cm鈭?) in the case of complex 2. (ii) Time resolved luminescence studies have revealed that the 3MLCT_1A and 3MLCT_1B excited states of complex 1 decay independently. On the other hand a dynamic equilibration occurs between two triplet excited states of complex 2. A slight interaction between the metal centers of complex 1 has been assumed by considering the electrochemical data, while a stronger coupling of the ruthenium atoms in complex 2 has been concluded by comparison of the oxidation potentials of the complex 2 with that of other binuclear ruthenium complexes of the metal centers possessing different chemical environment.}