Self-assembly of alternating left- and right-handed infinite Cd(II) helicates into a 2D open framework structure

Pyrazine-2,3,5,6-tetracarboxylic acid (ptcH4) reacts with Cd(NO3)2·6H2O at room temperature in the presence of pyridine to form a 2D open framework built from alternating left- and right-handed helicates with the empirical formula, {[Cd2(ptc)·(py)5·H2O]·5H2O·py}n, 1. Lattice water and pyridine molecules form an intricate array of H-bonding with the 2D sheets leading to a 3D structure. This compound crystallizes in the monoclinic space group C2/c with the following lattice parameters—a=24.103(2), b=13.480(5), c=29.176(4) Å, β=109.427(3)°, V=8940(4) Å3, Z=8, R1=0.0513, wR2=0.1552, S=1.085.