From achiral tetrazolate-based tectons to chiral coordination networks: effects of substituents on the structures and NLO properties

Abstract

Using a hydrothermal synthesis method, the combination of four tetrazolate-yl acylamide tectons bearing substituents of different sizes, 4-nitro-N-(1H-tetrazol-5-yl)benzamide (H-NTBAN), 4-fluoro-N-(1H-tetrazol-5-yl)benzamide (H-NTBAF), N-(1H-tetrazol-5-yl)isonicotinamide (H-NTINA) and N-(1H-tetrazol-5-yl)thiophene-2-carboxamide (H-NTTCA), with cadmium dichloride led to four crystalline coordination networks, named Cd₃(NTBAN)₆ (1), Cd(NTBAF)₂ (2), Cd(NTINA)₂ (3) and Cd(NTTCA)₂ (4), respectively. The X-ray diffraction analysis revealed that compounds 2, 3 and 4 possess a 3D non-interpenetrated diamondoid framework, while compound 1 is of a 0D trinuclear structure. Wherein, compounds 2, 3 and 4 crystallized in chiral space groups with significant second harmonic generation (SHG) efficiencies. The effects of substituents in the semirigid tetrazole-yl acylamide tectons on the structural topologies as well as on the nonlinear optical properties of the generated coordination networks are discussed.