Mononuclear copper (II) salicylate imidazole complexes derived from copper (II) aspirinate. Crystallographic determination of three copper geometries in a unit cell

Complexes of the type Cu(Im)n(sal)2 (1,2,3) (where Im = imidazole, and sal = salicylate ion) have been prepared from the reaction of Im with tetrakis (aspirinato) dicopper (II) and were crystallographically and spectroscopically characterized. The three imidazole complexes 1 (n=2), 2 (n=5) and 3 (n=6) co-crystallize and each complex is found in the unit cell. Crystals that contained 1, 2 and 3 have unit cell parameters of a=12.772(5), b=13.078(4) and c=18.199(7) Å, α=79.53(3), β=81.20(3) and γ=75.98(3)° and belong to the space group Pl̄. In 1 the copper ion is coordinated in a trans arrangement by two imidazole nitrogen atoms and two carboxylate oxygen atoms from the salicylate ligands. The second carboxylate atoms form weak interactions with the copper ion. For complex 2 the copper ion is in a distorted square pyramidal environment of nitrogen atoms from five imidazole ligands. There are two salicylate counterions. Complex 3 exists as tetragonally distorted octahedral copper (II) cation with six coordinated imidazole ligands and two salicylate counterions.