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Fluorescent Chemosensors for Heavy Metal Ions Based on Bis(terpyridyl) Ruthenium(II) Complexes Containing Aza‐Oxa and Polyaza Macrocycles
Author(s) -
PadillaTosta Miguel E.,
Lloris José Manuel,
MartínezMáñez Ramón,
Marcos M. Dolores,
Miranda Miguel A.,
Pardo Teresa,
Sancenón Felix,
Soto Juan
Publication year - 2001
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200106)2001:6<1475::aid-ejic1475>3.0.co;2-n
Subject(s) - ruthenium , chemistry , terpyridine , homoleptic , hexafluorophosphate , ligand (biochemistry) , fluorescence , chromophore , metal ions in aqueous solution , dichloromethane , metal , photochemistry , stereochemistry , medicinal chemistry , crystallography , catalysis , organic chemistry , ionic liquid , receptor , solvent , biochemistry , physics , quantum mechanics
Reactions of 4′‐[4‐(bromomethyl)phenyl]‐2,2′:6′,2′′‐terpyridine with 4,10‐diaza‐15‐crown‐5 and 1‐aza‐12‐crown‐4 in dichloromethane yielded the ligands L 1 and L 3 , respectively. Reaction of an excess of 4′‐[4‐(bromomethyl)phenyl]‐2,2′:6′,2′′‐terpyridine with 4,10‐diaza‐15‐crown‐5 yielded L 2 , while treatment of the same terpyridine ligand with 1,4,7,10,13‐pentaazacyclopentadecane afforded L 4 . Reactions of L 1 , L 3 , and L 4 with Ru(mtpy)Cl 3 (mtpy = 4′‐methyl‐2,2′:6′,2′′‐terpyridine) in methanol yielded the metallo receptors [Ru(L 1 )(mtpy)][PF 6 ] 2 , [Ru(L 3 )(mtpy)][PF 6 ] 2 , and [Ru(L 4 )(mtpy)][PF 6 ] 2 after precipitation with ammonium hexafluorophosphate and column chromatography. On treating L 3 with RuCl 3 , the homoleptic ruthenium complex [Ru(L 3 ) 2 ][PF 6 ] 2 was obtained. The synthesized metallo receptors contain oxa‐aza crown or polyazacycloalkane moieties as recognition sites and [Ru(tpy) 2 ] 2+ cores as the signal‐generating centre. The electronic spectra of the complexes are as expected for an Ru(tpy) 2 2+ chromophore, with the main Ru[d(π)] → tpy(π*) MLCT transition at ca. 484 nm and intense ligand‐centred transitions in the UV region. One of the most interesting aspects of these ruthenium complexes is their multicomponent nature, as they contain both coordination sites and fluorescent Ru(tpy) 2 2+ cores. The cations [Ru(L 1 )(mtpy)] 2+ , [Ru(L 3 )(mtpy)] 2+ , and [Ru(L 3 ) 2 ] 2+ display an emission maximum at ca. 650 nm, the intensity of which is pH dependent, showing an enhancement upon protonation. The metallo receptor [Ru(L 1 )(mtpy)] 2+ selectively senses Hg 2+ in preference to Cu 2+ , Cd 2+ , and Pb 2+ . The emission intensity vs. pH curve for [Ru(L 2 )(mtpy)] 2+ in the presence of Cu 2+ and Hg 2+ ions is close to that of the free receptor, but the presence of Cd 2+ or Pb 2+ enhances the emission intensity in the range pH 4−6. For the [Ru(L 3 ) 2 ] 2+ complex, Cd 2+ , Pb 2+ , and Hg 2+ induce an enhancement of the fluorescence of the Ru(tpy) 2 2+ core in the range pH 3.5−7.5. These results are compared with those obtained for the metallo receptor [Ru(L 4 )(mtpy)] 2+ containing a polyazacycloalkane moiety as the binding domain.