Construction of tube- and ladderlike copper(II). Coordination polymers based on the nicotinato tecton
Résumé
Three 1-D copper(II) coordination polymers have been obtained by using the nicotinato anion (NA-) as a bridge, and 2,2'-bipyridine or dicyanamide (dca) as coligands: Cu2(bipy)2(NA)2](ClO4)2·H2O 1, Cu2(Me2bipy)2(NA)2](ClO4)2 2, Cu3(NA)4(dca)2(H2O)8]·2H2O 3 (bipy = 2,2'-bipyridine; Me2bipy = 4,4'-dimethyl-2,2'-bipyridine, dca = dicyanamide anion). The metal-ligand association in compounds 1 and 2 is very similar and generates tubelike coordination polymers, which are constructed from pairs of copper atoms connected through two carboxylato groups from two NA- ligands. Each pyridyl moiety from the NA- ligand coordinates at the apical position of the copper ions from another pair, resulting in chains running along the crystallographic c axis. The structure of 3 consists of infinite ladderlike chains: the rungs are formed by trinuclear [Cu3] moieties, with the copper(II) ions connected through NA- bridges, the ladder sides being constructed from dca- bridging ligands. The cryomagnetic investigation of the three compounds reveals weak antiferromagnetic interactions mediated by the nicotinato ligand, 1: J = -7.3 cm-1, 2: -15.3 cm-1, 3: -0.58 cm-1