852547-85-4Relevant academic research and scientific papers
Sensitive oxidation state ambivalence in unsymmetrical three-center (M/Q/M) systems [(acac)2Ru(μ-Q)Ru(acac)2]n, Q = 1,10-phenanthroline-5,6-dione or 1,10-phenanthroline-5,6-diimine (n = +, 0, -, 2-)
Ghumaan, Sandeep,Sarkar, Biprajit,Patra, Srikanta,Van Slageren, Joris,Fiedler, Jan,Kaim, Wolfgang,Lahiri, Goutam Kumar
, p. 3210 - 3214 (2005)
The new redox systems [(acac)2Ru(μ-Q1)Ru(acac) 2]n (1n) and [(acac)2Ru(μ-Q 2)Ru(acac)2]n (2n) with Q1 = 1,10-phenanthroline-5,6-dione and Q2 = 1,10-phenanthroline-5,6- diimine were studied for n = +, 0, -, and 2- using UV-Vis-NIR spectroelectrochemistry and, in part, EPR and susceptometry. The ligands can bind the first metal (left) through the phenanthroline nitrogen atoms and the second metal (right) at the o-quinonoid chelate site. The neutral compounds are already different: Compound 1 is formulated as a RuII(μ-Q 1).- RuIII species with partially coupled semiquinone and ruthenium(III) centers. In contrast, a RuIII(μ- Q2)2- RuIII structure is assigned to 2, which shows a weak antiferromagnetic spin-spin interaction (J = -1.14 cm-1) and displays an intense half-field signal in the EPR spectrum. The one-electron reduced forms are also differently formulated as RuII(μ-Q 1)2- RuIII for 1- with a Ru III-typical EPR response and as RuII(μ-Q 2).- RuII for 2- with a radical-type EPR signal at g = 2.0020. In contrast, both 12- and 22- can only be described as RuII(μ-Q)2-RuII species. The monooxidized forms 1+ and 2+ show very similar spectroscopy, including a RuIII-type EPR signal. Although no unambiguous assignment was possible here for the alternatives Ru II(μ-Q)0RuIII, RuIII(μ-Q) 2-RuIV or RuIII(μ-Q).-Ru III, the last description is favored. The reasons for identical or different oxidation state combinations are discussed.
