Crystal and molecular structures of binuclear complexes of salycilic acid {Cu-M} (M = Cu, Sr, Ba)

Heterometallic complexes CuSr(SalH)₄(DMAA)₄(H₂O)] (II) and CuBa(SalH)₄(DMAA)₄ (H₂O)] (III) were synthesized by interaction of salicylates of s elements with copper nitrate. A mixture of III and vanadyl sulfate yielded the crystals of a homonuclear complex CuCu(SalH)₄(H₂O)₂]·2DMAA (I). According to single crystal X-ray data, all of the products are of lantern type and belong to two space groups: I is triclinic, space group P-1, unit cell parameters a = 9.9083(2) Å, b = 10.5077(3) Å, c = 10.9512(3) Å, α = 112.736(2)°, β = 114.0800(10)°, γ = 93.131°; II and III are tetragonal, space group P4/n, lattice parameters a = b = 16.3180(3) Å, c = 8.7838(2) Å for II and a = b = 16.362(3) Å, c = 8.920(1) Å III. The copper atoms have a square-pyramidal environment. The coordination number of Sr and Ba is 8, and the coordination polyhedron can be represented as a Thomson cube in both cases. The carboxylic groups are coordinated in a syn-syn bridging mode. The oxygen atom of the hydroxyl group of salicylic acid is not involved in coordination, but forms intramolecular hydrogen bonds to the carboxylic groups. The hydrogen bonds between water and DMAA solvate molecules, as well as — interactions between the aromatic fragments of the dimers, play a particularly important role in the molecular packing in crystal.