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Lanthanide complexes of the tetradentate N-donor liganddihydrobis[3-(2-pyridyl)pyrazolyl]borate and the terdentate N-donorligand 2,6-bis(1H-pyrazol-3-yl)pyridine: syntheses, crystalstructures and solution structures based on luminescence lifetime studies

Elefteria Psillakis, Peter L Jones, Michael D Ward, David A Bardwell

Πλήρης Εγγραφή

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Περίληψη

Lanthanide complexes of two polydentate N-donor ligands containing a mixture of pyridyl and pyrazolyl donors have been prepared. Dihydrobis[3-(2-pyridyl)pyrazolyl]borate (L 1 ) - is a tetradentate ligand with two bidentate chelating pyridyl/pyrazolyl arms linked by an apical BH 2 group; 2,6-bis(1H-pyrazol-3-yl)pyridine (L 2 ) is a terdentate chelating ligand reminiscent of terpyridine. Reaction of L 1 with lanthanide salts gave complexes of the type [M(L 1 ) 2 X] n+ ; the crystal structures of [Eu(L 1 ) 2 (dmf)][ClO 4 ]· 2.5CH 2 Cl 2 , [Tb(L 1 ) 2 (NO 3 )]·2CH 2 Cl 2 and [Tb(L 1 ) 2 (H 2 O)][L 1 ]· H 2 O·0.5CH 2 Cl 2 were determined and all contain two tetradentate ligands L 1 and an ancillary ligand X [dimethylformamide (dmf), nitrate or water] whose nature depends on the reaction/recrystallisation conditions to complete the co-ordination sphere. Luminescence studies of [Tb(L 1 ) 2 (NO 3 )] in water or D 2 O and MeOH or CD 3 OD showed that in methanol the solvation number q is ≈1.8, consistent with displacement of nitrate by the solvent; however in water q ≈ 4.5, indicating additional displacement of some of the N-donor heterocyclic rings of L 1 by co-ordinating water molecules. Reaction of L 2 with lanthanide salts afforded [M(L 2 ) 3 ] 3+ , all isolated as their hexafluorophosphate salts. The crystal structures of three of these (M = Eu, Gd or Ho) showed that they are isostructural and isomorphous, with tricapped trigonal-prismatic nine-co-ordinate geometries similar to that of [M(terpy) 3 ] 3+ (terpy = 2,2′:6′,2″- terpyridine).

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