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Bis(terpyridyl)‐Ruthenium(II) Units Attached to Polyazacycloalkanes as Sensing Fluorescent Receptors For Transition Metal Ions
Author(s) -
PadillaTosta Miguel E.,
Lloris José Manuel,
MartónezMáñez Ramón,
Benito Angel,
Soto Juan,
Pardo Teresa,
Miranda Miguel A.,
Marcos M. Dolores
Publication year - 2000
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/(sici)1099-0682(200004)2000:4<741::aid-ejic741>3.0.co;2-6
Subject(s) - chemistry , cyclam , ruthenium , terpyridine , ligand (biochemistry) , denticity , potentiometric titration , crystallography , photochemistry , crystal structure , medicinal chemistry , stereochemistry , metal , ion , organic chemistry , catalysis , biochemistry , receptor
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 (L 1 ) in which the tetraaza macrocycle was covalently attached to one benzyl‐terpyridyl 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 (L 2 ). The multidentate ligand L 2 was crystallographically characterised by single‐crystal X‐ray diffraction techniques. Reaction of L 1 with [Ru(mtpy)Cl 3 ] gave the heteroleptic ruthenium(II) complex [Ru(L 1 )(mtpy)][PF 6 ] 2 (mtpy = 4′‐methyl‐2,2′:6′2″‐terpyridine). The fluorescent intensity of the metallo‐receptor [Ru(L 1 )(mtpy)][PF 6 ] 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(L 1 )(mtpy)] 2+ in the presence of Cu 2+ were carried out. The quenching of the emission intensity was associated with the presence of the copper {Cu[Ru(L 1 )(mtpy)]} 4+ complex in solution. The receptor 1‐[4′‐methyl‐(2,2′:6′,2″‐terpyridyl)]‐1,4,8,11‐tetraazacyclotetradecane (L 3 ), 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 L 3 as starting material, the ruthenium complex [Ru(L 3 )(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 Cu 2+ .