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Ruthenium monoterpyridine complexes incorporating α,α′-diimine based ancillary functions. Synthesis, crystal structure, spectroelectrochemical properties and catalytic aspect

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Title Ruthenium monoterpyridine complexes incorporating α,α′-diimine based ancillary functions. Synthesis, crystal structure, spectroelectrochemical properties and catalytic aspect
 
Creator CHANDA, NRIPEN
MONDAL, BIPLAB
PURANIK, VEDAVATI G
LAHIRI, GOUTAM KUMAR
 
Subject spectroelectrochemistry
ruthenium
crystal structure
proton
 
Description Ruthenium monoterpyridine complexes of the type [RuII(trpy)(L′)(X)](ClO4)m·2H2O (1–2) [trpy=2,2′:6′,2″-terpyridine; L′=NC5H4C(H)=N(C6H4)nNH2 (n=1 and 2); X=Cl−, m=1 (1); X=H2O, m=2 (2)] have been synthesized via the selective hydrolysis of one of the imine functions present in the preformed stable dinucleating bridging functions, NC5H4C(H)=N(C6H4)nN=C(H)H4C5N (L) (n=1, 2). The single crystal X-ray structures of the dinucleating bridging function (L1) and the chloro complex (1a) (in both cases n=1) have been determined. The complexes stabilize preferentially in one particular isomeric form where the Cl− or H2O molecule is in the trans configuration with respect to the N(imine) center. The chloro complexes (1) exhibit strong MLCT bands near 500 nm whereas in the case of the aqua complexes (2) the MLCT bands are blue shifted near 470 nm. The chloro complexes (1) exhibit weak emissions in EtOH–MeOH (4:1 v/v) glass at 77 K near 600 nm (quantum yield, Φem=0.015–0.03). In acetonitrile solvent 1 display a ruthenium(III)–ruthenium(II) couple near 0.8 V and terpyridine based reduction near 1 V versus SCE. The aqua complexes (2) exhibit a concerted 2e−/2H+ oxidation process in the acidic region and in the alkaline region, the complexes display a 2e−/H+ oxidation process. The potentials are observed to decrease linearly with the increase in pH. The proton coupled redox processes in the acidic and basic regions correspond to [RuII(trpy)(L′)(H2O)]2+–[RuIV(trpy)(L′)(O)]2+ and [RuII(trpy)(L′)(OH)]+–[RuIV(trpy)(L′)(O)]2+ couples, respectively. The chemical oxidation of 2 by excess CeIV solution in 1 (N) H2SO4 also leads to the formation of the corresponding [RuIV(trpy)(L′)(O)]2+ (3). The oxo complexes (3) are stable only in the presence of excess CeIV ion, otherwise they slowly catalyze the oxidation of water to dioxygen and return back to the parent aqua species. The electrochemically generated oxo-species are found to catalyze the benzyl alcohol oxidation process.
 
Publisher Elsevier
 
Date 2009-04-03T09:04:20Z
2011-11-25T20:35:01Z
2011-12-26T13:08:11Z
2011-12-27T05:56:12Z
2009-04-03T09:04:20Z
2011-11-25T20:35:01Z
2011-12-26T13:08:11Z
2011-12-27T05:56:12Z
2002
 
Type Article
 
Identifier Polyhedron 21(20), 2033-2043
0277-5387
http://dx.doi.org/10.1016/S0277-5387(02)01131-2
http://hdl.handle.net/10054/1117
http://dspace.library.iitb.ac.in/xmlui/handle/10054/1117
 
Language en