Significant Influence of Coligands Toward Varying Coordination Modes of 2,2鈥?Bipyridine-3,3鈥?diol in Ruthenium Complexes
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- 作者：Prabir Ghosh ; Prasenjit Mondal ; Ritwika Ray ; Ankita Das ; Sukdev Bag ; Shaikh M. Mobin ; Goutam Kumar Lahiri
- 刊名：Inorganic Chemistry
- 出版年：2014
- 出版时间：June 16, 2014
- 年：2014
- 卷：53
- 期：12
- 页码：6094-6106
- 全文大小：601K
- 年卷期：v.53,no.12(June 16, 2014)
- ISSN：1520-510X
文摘
The varying coordination modes of the ambidentate ligand 2,2鈥?bipyridine-3,3鈥?diol (H2L) in a set of ruthenium complexes were demonstrated with special reference to the electronic features of the coligands, including 蟽-donating acac鈥?/sup> (= acetylacetonate) in RuIII(acac)2(HL鈥?/sup>) (1), strongly 蟺-accepting pap (= 2-phenylazopyridine) in RuII(pap)2(L2鈥?/sup>) (2)/[(pap)2RuII(渭-L2鈥?/sup>)RuII(pap)2](ClO4)2 ([4](ClO4)2), and reported moderately 蟺-accepting bpy (= 2,2鈥?bypiridine) in [RuII(bpy)2(HL鈥?/sup>)]PF6 ([5]PF6)/[(bpy)2Ru(渭-L2鈥?/sup>)Ru(bpy)2](PF6)2 ([7](PF6)2). The single-crystal X-ray structures reveal that, in paramagnetic and electron paramagnetic resonance active 1 and reported diamagnetic [5]PF6, nearly planar monoanionic HL鈥?/sup> coordinates to the metal ion via the N,N donors forming a five-membered chelate ring with hydrogen-bonded O鈥揌路路路O function at the backbone of the ligand framework, as has also been reported in other metal complexes. However, structurally characterized diamagnetic 2 represents O鈥?/sup>,O鈥?/sup> bonded seven-membered chelate of fully deprotonated but twisted L2鈥?/sup>. The nonplanarity of the coordinated L2鈥?/sup> in 2 does not permit the second metal fragment {Ru(pap)2} or {Ru(bpy)2} or {Ru(acac)2} to bind with the available N,N donors at the back face of L2鈥?/sup>. Further, the deprotonated form of the model ligand 2,2鈥?biphenol (H2L鈥? yields RuII(pap)2(L鈥?sup>2鈥?/sup>) (3); its crystal structure establishes the expected O鈥?/sup>,O鈥?/sup> bonded seven-membered chelate of nonplanar L鈥?sup>2鈥?/sup> as in reported RuII(bpy)2(L鈥?sup>2鈥?/sup>) (6), although {Ru(acac)2} metal precursor altogether fails to react with H2L鈥? All attempts to make diruthenium complex from {Ru(acac)2} and H2L failed; however, the corresponding {Ru(pap)22+} derived dimeric [4](ClO4)2 was structurally characterized. It establishes the symmetric N,O鈥?/sup>/N,O鈥?/sup> bridging mode of nonplanar L2鈥?/sup> as in reported [7](PF6)2. Besides structural and spectroscopic characterization of the newly developed complexes, the ligand (HL鈥?/sup>, L2鈥?/sup>, L鈥?sup>2鈥?/sup>, pap)-, metal-, or mixed metal鈥搇igand-based accessible redox processes in 1n (n = +2, +1, 0, 鈭?), 2n/3n (n = +2, +1, 0, 鈭?, 鈭?), and 4n (n = +4, +3, +2, +1, 0, 鈭?) were analyzed in conjunction with density functional theory calculations.