title: Synthesis, crystal structures, and luminescence of organic-lanthanide complexes with nicotinate and isonicotinate ligands.
abstract: Six lanthanide coordination compounds with two isomeric carboxylic acids, nicotinic acid (HL(1)) and isonicotinic acid (HL(2)), [(L(1))3Ln(H2O)2]2 (Ln = Eu, 1; Gd, 2; Tb, 3) and [( L(2))2Ln(H2O)4][NO3] (Ln = Eu, 4; Gd, 5; Tb, 6), have been synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1-3 are dimeric whereas 4-6 are polymeric, all with 8-coordination of Ln(3+). The distinction between these lanthanide complexes is readily accomplished from the 10 K high resolution electronic emission spectra. Spectral interpretation is given for the Eu(3+) complexes 1, 4, whereas the spectra of 3 and 6 are more complex. The relationships between spectroscopic and crystallographic site symmetries are discussed. The calculated second rank crystal field strengths of Eu(3+) in 1 and 4 are intermediate in magnitude.
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR., PR China.
authors.forename: Guohua
authors.initials: G
authors.lastname: Jia
authors.forename: Ga-Lai
authors.initials: GL
authors.lastname: Law
authors.forename: Ka-Leung
authors.initials: KL
authors.lastname: Wong
authors.forename: Peter A
authors.initials: PA
authors.lastname: Tanner
authors.forename: Wing-Tak
authors.initials: WT
authors.lastname: Wong