Unequivocal characterisation of a [Ln(terpy)(NO 3) 3·(H 2O)] complex. : The synthesis and structure of [M(terpy)(NO 3) 3·(H 2O)] (M=Eu, Tb); a comparison with the structure of [Eu(bipy) 2(NO 3) 3] and with other europium nitrate complexes {terpy=2,2′:6′,2″-terpyridyl; bipy=2,2′-bipyridyl}

Abstract

The complexes [M(terpy)(NO 3) 3·(H 2O)] (M=Eu ( 1), Tb( 2); terpy=2,2′:6′,2″-terpyridyl) are isomorphous and crystallise in the triclinic space group P 1 ̄ with Z=2, while the related complex [Eu(bipy) 2(NO 3) 3] ( 3) (bipy=2,2′-bipyridyl) crystallises in the orthorhombic space group Pcan (non-standard setting of Pbcn) with Z=4 such that the two halves of the molecule are related by a crystallographic twofold axis. In each of the three complexes the metal atom is 10 co-ordinate and all three contain three bidentate nitrate groups. In complexes 1 and 2 the coordination sphere is completed by the three nitrogen donor atoms of the terpyridine ligand and by the oxygen donor atom of the coordinated water solvent molecule. In complex 3 the coordination sphere is completed by two nitrogen donor atoms from each of the two bipyridine ligands. These structures are compared with other lanthanide complexes of related ligands and the factors affecting the co-ordination geometry evaluated.