Structural diversity in lanthanum(III) coordination polymers constructed with the isomeric flexible double betaines 1,4-bis( n-picolyloxyl)benzene- N, N′-diacetate ( n=2, 3)

Abstract

Six coordination polymers: {[La(H 2O) 6L 1] 2Cl 6·12H 2O} ∞ ( 1), [La(H 2O) 2L 1(NO 3) 3] ∞ ( 2), {[La(H 2O) 4(L 1) 2](CF 3SO 3) 3·H 2O} ∞ ( 3), {[La(H 2O) 7(L 2) 0.5]Cl 3} ∞ ( 4), {[La(H 2O) 2L 2(NO 3) 2]NO 3·0.5H 2O} ∞ ( 5) and {[La(H 2O) 3(L 2) 2](CF 3SO 3) 3·6H 2O} ∞ ( 6) have been synthesized by the reaction between lanthanum(III) salts and the isomeric double betaines 1,4-bis(2-picolyloxyl)benzene- N, N′-diacetate (L 1) and 1,4-bis(3-picolyloxyl)benzene- N, N′-diacetate (L 2). Compound 1, 2 and 3 are all mononuclear: 1 shows a double-layer network constructed by ML 1 coordination bonds together with hydrogen bonds, while 2 and 3 are 3D frameworks. In compound 4, 5 and 6, dinuclear units are linked by one, two and four L 2 ligands, respectively, leading to different kinds of polymeric chains; in each compound the chains are further connected through intermolecular hydrogen bonding and π–π stacking to generate a 2D network.