Synthesis and characterization of two new open-framework zinc phosphites [M(C₆N₄H₁₈)][Zn₃(HPO ₃)₄] (M=Ni, Co) with multi-directional intersecting 12-membered ring channels

Two new open-framework zinc phosphites, [M(C₆N₄H ₁₈)][Zn₃(HPO₃)₄] (M=Ni, Co), have been prepared under hydrothermal conditions. Single-crystal X-ray diffraction analysis shows that [Ni(C₆N₄H₁₈)][Zn ₃(HPO₃)₄] (1) and [Co(C₆N ₄H₁₈)][Zn₃(HPO₃)₄] (2) are isostructural and both crystallize in the monoclinic space group C2/c with a=15.325(3)Å, b=9.792(2)Å, c=14.514(3)Å, β=109.83(3) °, V=2048.8(7)Å3, Z=4, R1=0.0408 (I>2σ(I)), and wR2=0.1104 (all data) for 1, and a=15.277(2)Å, b=9.8831(13)Å, c=14.534(2)Å, β=109.328(2)°, V=2070.7(5)Å3, Z=4, R1=0.0380 (I>2σ(I)), and wR2=0.1093 (all data) for 2. The structures of 1 and 2 are built up from strictly alternating ZnO₄ tetrahedra and HPO ₃ pseudo-pyramids linked through oxygen vertices to form the three-dimensional (3-D) open-frameworks with multi-directional intersecting 12-membered ring (12-MR) channels. The M(TETA) (M=Ni, Co) complexes self-assembled under hydrothermal system connect with the inorganic host via M-O-P linkages and interact with inorganic framework through weak H-bonds. The two compounds show intense photoluminescence upon photoexcitation at 235 nm.