Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/xmlui/handle/100/16519
Title: Significant Influence of Coligands Toward Varying Coordination Modes of 2,2 '-Bipyridine-3,3 '-diol in Ruthenium Complexes
Authors: GHOSH, P
MONDAL, P
RAY, R
DAS, A
BAG, S
MOBIN, SM
LAHIRI, GK
Issue Date: 2014
Publisher: AMER CHEMICAL SOC
Citation: INORGANIC CHEMISTRY, 53(12)6094-6106
Abstract: The varying coordination modes of the ambidentate ligand 2,2'-bipyridine-3,3'-diol (H2L) in a set of ruthenium complexes were demonstrated with special reference to the electronic features of the coligands, including sigma-donating acac(-) (= acetylacetonate) in Ru-III(acac)(2)(HL-) (1), strongly pi-accepting pap (= 2-phenylazopyridine) in Ru-II(pap)(2)(L2-) (2)/[(pap)(2)Ru-II(mu-L2-)Ru-II(pap)(2)](ClO4)(2) ([4](ClO4)(2)), and reported moderately pi-accepting bpy (= 2,2'-bypiridine) in [Ru-II(bpy)(2)(HL-)]PF6 ([5]PF6)/[(bpy)(2)Ru(mu-L2-)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- coordinates to the metal ion via the N,N donors forming a five-membered chelate ring with hydrogen-bonded O-H center dot center dot center dot 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-,O- bonded seven-membered chelate of fully deprotonated but twisted L2-. The nonplanarity of the coordinated L2- 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-. Further, the deprotonated form of the model ligand 2,2'-biphenol (H2L') yields Ru-II(pap)(2)(L'(2-)) (3); its crystal structure establishes the expected O-,O- bonded seven-membered chelate of nonplanar L'(2-) as in reported Ru-II(bpy)(2)(L'(2-)) (6), although {Ru(acac)(2)} metal precursor altogether fails to react with H2L'. All attempts to make diruthenium complex from {Ru(acac)(2)} and H2L failed; however, the corresponding {Ru(pap)(2)(2+)} derived dimeric [4](ClO4)(2) was structurally characterized. It establishes the symmetric N,O-/N,O- bridging mode of nonplanar L2- as in reported [7](PF6)(2). Besides structural and spectroscopic characterization of the newly developed complexes, the ligand (HL-, L2-, L'(2-), pap)-, metal-, or mixed metal-ligand-based accessible redox processes in 1(n) (n = +2, +1, 0, -1), 2(n)/3(n) (n = +2, +1, 0, -1, -2), and 4(n) (n = +4, +3, +2, +1, 0, -1) were analyzed in conjunction with density functional theory calculations.
URI: http://dx.doi.org/10.1021/ic5004676
http://dspace.library.iitb.ac.in/jspui/handle/100/16519
ISSN: 0020-1669
1520-510X
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