Preparation of single crystals of coordination solids in silica gels: synthesis and structure of CuII(1,4-C4H4N2)(C4O4)(OH2)4

The title compound, Cu II (1,4-C 4 H 4 N 2 )(C 4 O 4 )((OH 2 ) 4 , was synthesized at room temperature using a silica gel medium to grow single crystals that have been analyzed by X-ray diffraction. It crystallizes in the monoclinic space group P2 1 /n, with a = 6.887(3)A, b = 11.141(4)A, c = 7.545(3)A, β = 90.68(3)°, V = 578.9(4) A 3 , Z = 2, and R(R w ) = 0.0263 (0.0393). The structure is composed of a linear chain of Cu II (1,4-C 4 H 4 N 2 )(OH 2 ) 4 that is closely hydrogen bonded to squarate anions which link the chains together in a 3-D framework. This material was found to be insoluble in most common solvents; thus it was difficult to obtain large crystals without employing the gel as a diffusion medium. This method might serve as a route to accessing new crystalline solids that are constructed from soluble molecular building blocks.