Crucial influence of solvent and chirality - The formation of helices and three-dimensional nets by hydrogen-bonded biimidazolate complexes

Deprotonation and recrystallisation of racemic [Co(2,2'-biimidazole)(3)]- [ NO3](3) by ammonia in water/dimethylformamide solutions gave crystals of [C o(Hbiim)(3)].0.8H(2)O .0.5DMF (2: Hbiim=monoanion of 2,2'-biimidazole, DMF = dimethylformamide), a porous material that contains fourfold interpenetra ting (10,3) three-dimensional nets formed by neutral, hydrogen-bonded [Co(H biim)(3)] units, with DMF molecules in the narrow channels. Recrystallisati on of [Delta -Co(2,2'-biimidazolate)(3)] gave helices instead of the expect ed (10,3)-a net. These results are discussed in the light of additional den sity functional theory and molecular mechanics calculations and the X-ray s tructure of [Co(H(2)biim)(3)][NO3](3).