Homochiral helical wavelike (4,4) networks constructed by divalent metal ions and S-carboxymethyl-l-cysteine

The synthesis, X-ray characterization and second-harmonic generation of three new two-dimensional coordination polymers [CuL(H₂O)]_n (1), [ZnL(H₂O)]_n (2) and {[CdL(H₂O)]·2H₂O}_n (3) (L=S-carboxymethyl-l-cysteine) are reported, which exhibit wavelike (4,4) topology, and are assembled into three-dimensional networks by hydrogen-bonding interactions. The most intriguing feature in 1, 2 and 3 is the presence of two types of homo-chiral helices. They crystallize in the chiral space groups P2₁ or P2₁2₁2₁, and displays modest powder SHG efficiencies.