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Azulene‐Moiety‐Based Ligand for the Efficient Sensitization of Four Near‐Infrared Luminescent Lanthanide Cations: Nd 3+ , Er 3+ , Tm 3+ , and Yb 3+
Author(s) -
Zhang Jian,
Petoud Stéphane
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200701068
Subject(s) - lanthanide , chemistry , luminescence , ligand (biochemistry) , molecule , infrared spectroscopy , denticity , photochemistry , inorganic chemistry , analytical chemistry (journal) , crystallography , ion , materials science , crystal structure , organic chemistry , biochemistry , receptor , optoelectronics
The ML 4 complexes formed by reaction between the bidentate azulene‐based ligand diethyl 2‐hydroxyazulene‐1,3‐dicarboxylate (HAz) and several lanthanide cations (Pr 3+ , Nd 3+ , Gd 3+ , Ho 3+ , Er 3+ , Tm 3+ , Yb 3+ , and Lu 3+ ) have been synthesized and characterized by elemental analysis, FT‐IR vibrational spectroscopy and electrospray ionization mass spectroscopy. Spectrophotometric titrations have revealed that four Az − ligands react with one lanthanide cation to form the ML 4 complex in solution. Studies of the luminescence properties of these ML 4 complexes demonstrated that Az − is an efficient sensitizer for four different near‐infrared emitting lanthanide cations (Nd 3+ , Er 3+ , Tm 3+ , and Yb 3+ ); the resulting complexes have high quantum yield values in CH 3 CN. The near‐infrared emission arising from Tm 3+ is especially interesting for biologic imaging and bioanalytical applications since biological systems have minimal interaction with photons at this wavelength. Hydration numbers, representing the number of water molecules bound to the lanthanide cations, were obtained through luminescence lifetime measurements and indicated that no molecules of water/solvent are bound to the lanthanide cation in the ML 4 complex in solution. The four coordinated ligands protect well the central luminescent lanthanide cation against non‐radiative deactivation from solvent molecules.