Mono‐, Di‐ and Polymeric Calcium and Gadolinium Complexes of the Tripodal Ligand 2,2′,2′′‐Nitrilotribenzoic Acid

Abstract

AbstractThree novel carboxylate‐bridged complexes incorporating the tripodal N,O ligand 2,2′,2′′‐nitrilotribenzoic acid H3L of formula [CaII(H2L)(OH2)4][(H2L)]·4H2O (1), [CaII(OH2)4]‐[CaII(L)(OH2)2]2·7H2O (2) and [GdIII(L)(OH2)3]2[GdIII(L)‐(OH2)4]2·13H2O (3) were synthesized and characterized by X‐ray crystallography. In all three complexes, the ligand H3L binds to the metal centre only by its three carboxylate donors, leaving the bridgehead nitrogen atom nonbonding. The calcium(II) ion in the monomeric complex 1 is distorted pentagonal‐bipyramidal coordinated, the +1 charge of the complex cation [CaII(H2L)(OH2)4]+ is balanced by an H2L– anion and both units are connected by hydrogen bonds. The polymeric compound 2 displays a one‐dimensional chain structure, in which two [CaII(L)]2– units form a dimeric structure and are connected by hydrated CaII ions. 3 contains two different [GdIII(L)(OH2)n] dimers. In one of them the two GdIII ions are linked by two monoatomic carboxylate O‐bridges showing a short Gd···Gd distance of 3.99 Å. In the second, a syn‐anti carboxylate 1,3‐bridge with a longer Gd···Gd distance of 4.96 Å is observed. Magnetic measurements of 3 show paramagnetic behaviour with weak antiferromagnetic coupling. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)