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pH‐Induced Luminescence Changes of Chromophore‐Quencher Tricarbonylpolypyridylrhenium(I) Complexes with 4‐Pyridinealdazine
Author(s) -
Cattaneo Mauricio,
Fagalde Florencia,
Katz Néstor E.,
Borsarelli Claudio D.,
Parella Teodor
Publication year - 2007
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/ejic.200700860
Subject(s) - chemistry , luminescence , chromophore , excited state , protonation , delocalized electron , bipyridine , photochemistry , aqueous solution , crystallography , osmium , rhenium , inorganic chemistry , ruthenium , crystal structure , organic chemistry , catalysis , ion , physics , optoelectronics , nuclear physics
Abstract The new chromophore‐quencher tricarbonylrhenium(I) complexes [Re(4,4′‐X 2 ‐bpy)(CO) 3 (PCA)] + , [(4,4′‐X 2 ‐bpy)(CO) 3 Re(μ‐PCA)Re(CO) 3 (4,4′‐X 2 ‐bpy)] 2+ , and [(4,4′‐X 2 ‐bpy)(CO) 3 Re I (μ‐PCA)Ru II (NH 3 ) 5 ] 3+ (X = Ph or CO 2 Me and PCA = 4‐pyridinealdazine) have been synthesized as their PF 6 – salts and characterized by spectroscopic, electrochemical, and photophysical techniques. In contrast to previously reported species with X = Me or H, these complexes emit at room temperature in CH 3 CN. The recovery of luminescence can thus be ascribed to the change of energy levels induced by adding electron‐withdrawing substituents to the 2,2′‐bipyridine ring, since the emissive Re II (X 2 bpy – ) excited state becomes much lower in energy than the Re II (PCA – ) non‐emissive excited state. For the mononuclear and symmetric dinuclear rhenium(I) complexes with X = CO 2 Me, consecutive protonation of both the pyridinyl and imine N atoms of PCA in aqueous solution leads to unusual bell‐shaped curves for both the absorption and the emission intensities vs. pH because of opposite effects on the electronic delocalization of PCA. This latter property can be employed to devise novel luminescent pH sensors of the on‐off‐on type. The corresponding unsymmetrical dinuclear complexes [(4,4′‐X 2 ‐bpy)(CO) 3 Re I (μ‐PCA)Ru III (NH 3 ) 5 ] 4+ have been obtained in situ by oxidizing the [Re I ,Ru II ] precursors in CH 3 CN solution. Spectral and electrochemical measurements with these complexes lead to the values of the metal‐to‐metal electronic coupling elements.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)