Host-Guest Symmetry and Charge Matching in Glycine-Templated Metal Sulfate-Oxalates Obtained by a Solvent-Free Method

The host-guest symmetry and charge-matchingeffecthas been demonstrated in two glycine-templated metal sulfate-oxalateswith moderate second-harmonic-generation responses. Two metal sulfate-oxalates, (Hgly)(2)center dot Zn-(SO4)-(C2O4) (1) and Hgly center dot In-(SO4)-(C2O4)-(gly)(2), wereprepared under solvent-free conditions, where gly = glycine. Theyhave similar layered structures despite the fact that aliovalent metalions are used as structural nodes. Notably, glycine molecules playdual roles as a protonated cation and a zwitterionic ligand in compound 2. The two compounds display moderate second-harmonic-generation(SHG) responses, confirming their noncentrosymmetric structures. Theoreticalcalculations were performed to reveal the origin of their SHG responses.