Dimer species in dimethyl sulfoxide–water (80∶20 w/w) solution of N,N′-bis(salicylideneimine)-m-phenylenediamine (H2sal-m-phen) and similar Schiff bases with CuII, NiII, CoII and ZnII. Crystal structure of [Co2(sal-m-phen)2]·CHCl3 ‡ | Publicación