Solvent-free synthesis and optical properties of two open-framework metal oxalates with zeolitic ABW and diamondoid topologies

Two new metal oxalates, namely, C9H25N3<middle dot>Sc2(C2O4)4<middle dot>2H2O (1) and C9H25N3<middle dot>In2(C2O4)4 (2), have been prepared under solvent-free conditions. They have different 4-connected frameworks with zeolitic ABW and diamondoid topologies, respectively. Notably, compound 2 displays a moderate second-harmonic-generation response under 1064 nm laser irradiation. Theoretical calculations are performed to gain insight into the optical properties of the two compounds. Two noncentrosymmetric open-framework metal oxalates with wide optical band gaps and moderate birefringences were prepared under solvent-free conditions.