Five New Zinc Phosphite Structures: Tertiary Building Blocks in the Construction of Hybrid Materials

The syntheses and structures of five new zinc phosphites [Zn(HPO3)(C4H6N2)] (1), [Zn2(HPO3)2(C10H10N2)2]2 (2),
[Zn(HPO3)(C14H14N4)0.5] (3), [Zn2(HPO3)2(C14H14N4)]·0.4H2O (4), and [Zn2(HPO3)2(C14H14N4)] (5) are reported. In
compounds 1−3, the zinc atoms are ligated by 1-methylimidazole, 1-benzylimidazole, and 1,4-bis(imidazol-1-ylmethyl)benzene, respectively, while compounds 4 and 5 are synthesized in the presence of the same bifunctional ligand,
1,3-bis(imidazol-1-ylmethyl)benzene. The inorganic framework of compound 1 is composed of vertex-shared ZnO3N
and HPO3 tetrahedra that form 4-rings, which, in turn, are linked to generate a one-dimensional ladder structure.
In 2, the inorganic framework is composed of 4-rings and 8-rings to form the well-known 4.82 2D network. This is
connected via C−H···π interactions between 1-benzylimidazole ligand to generate a pseudo-pillared-layer structure.
In 3, the inorganic framework again has the 4.82 topology pillared by the bis(imidazole) ligand, 1,3-bis(imidazol-1-ylmethyl)benzene. In 4, a new layer pattern is observed. Specifically, three edge-sharing 4-rings form triple-fused
4-rings. These tertiary building units are further connected to form 12-rings. The alternating triple 4-rings and
12-rings form a previously unknown 2D inorganic sheet. The sheets are joined together by the bis(imidazole)
ligand, 1,3-bis(imidazol-1-ylmethyl)benzene, to generate a 3D pillared-layer structure. In 4, benzene rings and imidazole
rings stack in a zigzag pattern in the interlayer space. A significant role for the triple 4-ring tertiary building unit in
the formation of hybrid inorganic/organic metal phosphite structures is proposed for 4 and 5. In 5, the triple 4-rings
fuse to give a 1D stair-step structure. Calculations show that the triple 4-ring pattern observed in the linear ladder
structure of 1 is more stable than that in the stair step pattern of 5.