Auxiliary ligand-directed synthesis of cadmium(II) and zinc(II) complexes from 1-D chains to 3-D architectures with 5-nitroisophthalate

A series of cadmium(II) and zinc(II) metal-organic frameworks, [Cd(NIPH)(2-apy)(H2O)center dot(H2O)] (1), [Cd(NIPH)(4-apy)(2)(H2O)] (2), [Zn-2(NIPH)(2)(mu(3)-OH)(H2O)center dot(2-Hapy)] (3), [Zn-5(NIPH)(4)(mu(3)-OH)(2)(mu(2)-OH)( H2O)center dot(3-Hapy)] (4), and [Zn-5(NIPH)(4)(mu(3)-OH)(2)(mu(2)-OH)(H2O)center dot(4-Hapy)center dot(H2O)] (5), were synthesized by hydrothermal reactions of the corresponding Cd(II) and Zn(II) salts with 5-nitroisophthalic acid (H2NIPH) in the presence of aminopyridine (apy) auxiliary ligands. These frameworks exhibit three typical structural features: 1 and 2 possess a 1-D double-stranded loop-like chain and a 1-D linear chain formed by [Cd2N2O10] dinuclear building blocks and [CdN2O5] monoclear building blocks, respectively; 3 is a 2-D anionic framework consisting of [Zn4O16] tetranuclear building blocks; both 4 and 5 are 3-D anionic frameworks constructed by both [Zn4O16] tetranuclear and [Zn6O22] hexanuclear building blocks. The apy ligands participate in constructing frameworks of 1 and 2, but are protonated in the channels of 3-5 as charge-balancing and space-filing agents. The thermal stability, luminescent properties and ion-exchange behavior of the complexes were investigated.