- A prospective study of the use of the [Os(tpy)2]2+ (tpy = 2,2′;6′:2″-terpyridine) core as signalling scaffolding for the development of chemical sensors
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The heteroleptic osmium(II) complex [Os(L1)(Me-phtpy)]-[PF 6]2 (L1 = 1-[4′-p-tolyl-(2,2′: 6′,2″-terpyridyl)]-1,4,8,11-tetraazacyclotetradecane, Me-phtpy = 4′-p-tolyl-2,2′:6′,2″-terpyridine) has been prepared, characterized and its potential use for chemical sensing purposes studied. The complex contains a polyazacycloalkane as binding site and a Os(tpy)22+ core that acts as a signalling subunit . The emission intensity of the osmium complex was quenched in acetonitrile/water (1:1 v/v) by Cu2+ and Ni2+. Potentiometric titrations of [Os(L1)(Me-phtpy)]2+ in the presence of Cu2+ were carried out in order to determine thermodynamic binding constants in acetonitrile/water (70:30 v/v, 0.1 mol·dm -3 tetrabutylammonium perchlorate). With Cu2+ the receptor [Os(L1)-(Me-phtpy)]2+ forms the complex {Cu[Os(L 1)(Me-phtpy)]}4+ at neutral pH. Moreover it undergoes two stepwise protonation processes at acid pH related to the partial protonation of the cyclam core and forms two hydroxo complexes at basic pH. The Ni2+ complexes of the osmium receptor [Os(L1)(Me-phtpy)]2+ are able to act as an anion fluorogenic chemosensor in acetonitrile/water mixtures. A displacement of the quenching effect to more acidic pH in the Ni 2+-[Os(L1)(Me-phtpy)]2+ system was observed for anions in the order ATP > AMP > chloride. A prospective study of the use of the [Os(L1)-(Me-phtpy)]2+ complex as a fluorogenic sensor for oxygen was also carried out by incorporation of the complex in solgel silica films made with TEOS and MTEOS. Significant quenching of the osmium fluorescence by oxygen was observed. The oxygen response of the films showed good stability and repeatability. The study suggested that the Os(tpy) 22+ core might act as suitable signalling scaffolding in chemical sensing systems of cations, anions and gases. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Ros-Lis, Jose V.,Martinez-Manez, Ramon,Soto, Juan,McDonagh, Colette,Guckian, Adrian
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- Coordination chemistry of some terpyridyl-polyamine bridging ligands
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A series of ditopic ligands bearing terpyridyl and polyamine coordination sites have been prepared. Complexes with RuII bound to the terpyridyl sites of many of these ligands have been prepared. RuII complexes of these ligands appear vulnerable to nucleophilic displacement of the polyamine portion of the ligand by BH4 -. A limited study of the coordination chemistry of the polyamine portion of the RuII complexes has been conducted, including the synthesis and characterization of Ru IICoIII heterodinuclear complexes in which the Co III centre is coordinated by a cyclam macrocycle. The Co III centre in these systems is unexpectedly labile it can be removed from the polyamine upon treatment with ethane-1,2-diamine. CSIRO 2010.
- Zibaseresht, Ramin,Downward, Alan M.,Hartshorn, Richard M.
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experimental part
p. 669 - 679
(2010/08/20)
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- Bis(terpyridyl)-ruthenium(II) units attached to polyazacycloalkanes as sensing fluorescent receptors for transition metal ions
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A synthetic strategy has been devised for the preparation of new compounds in which terpyridyl fragments are linked to 1,4,8,11- tetraazacyclotetradecane (cyclam). Reaction of excess cyclam with 4'-[(4- bromomethyl)phenyl]-2,2':2'',6'-terpyridine afforded the ligand 1-[4'-p- tolyl-(2,2':6',2''-terpyridyl)]-1,4,8,11-tetraazacyclotetradecane (L1) in which the tetraaza macrocycle was covalently attached to one benzylterpyridyl fragment. Under similar conditions reaction of cyclam with excess 4'-[(4- bromomethyl)phenyl]-2,2':2'',6'-terpyridine gave the tetra substituted cyclam derivative 1,4,8,11-[4'-p-tolyl-(2,2':6',2''-terpyridyl)]-1,4,8,11- tetraazacyclotetradecane (L2). The multidentate ligand L2 was crystallographically characterised by single-crystal X-ray diffraction techniques. Reaction of L1 with [Ru(mtpy)Cl3] gave the heteroleptic ruthenium(II) complex [Ru(L1)(mtpy)][PF6]2 (mtpy = 4'-methyl-2,2':6'2''- terpyridine). The fluorescent intensity of the metallo-receptor [Ru(L1)(mtpy)][PF6]2 was quenched selectively in the presence of copper(II) in an aqueous environment. To gain insight into the nature of this interaction, potentiometric titrations on [Ru(L1)(mtpy)]2+ in the presence of Cu2+ were carried out. The quenching of the emission intensity was associated with the presence of the copper {Cu[Ru(L1)(mtpy)]}4+ complex in solution. The receptor 1-[4'-methyl-(2,2':6',2''-terpyridyl)]-1,4,8,11- tetraazacyclotetradecane (L3), in which the cyclam fragment is separated from the terpyriyl by a methylene group, has also been synthesised by reaction of 4'-bromomethyl-2,2':2'',6'-terpyridine and cyclam. With L3 as starting material, the ruthenium complex [Ru(L3)(mtpy)]2+ was prepared in order to evaluate the effect that the nature of the spacer has on the quenching of the fluorescence upon addition of Cu2+.
- Padilla-Tosta, Miguel E.,Lloris, José Manuel,Martínez-Má?ez, Ramón,Benito, Angel,Soto, Juan,Pardo, Teresa,Miranda, Miguel A.,Marcos, M. Dolores
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p. 741 - 748
(2007/10/03)
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