Synthesis, structures and luminescent properties of cadmium(ii) metal organic frameworks based on 3-pyrid-4-ylbenzoic acid, 4-pyrid-4-ylbenzoic acid ligands

Two three-dimensional metal–organic frameworks, [Cd3K(L1)6(H2O)3](OH)(DMF)4 (1) (HL1 = 3-pyrid-4-ylbenzoic acid) and [Cd(L2)2](DMF)(H2O)0.25 (2) (HL2 = 4-pyrid-4-ylbenzoic acid), have been synthesized by using two ligands with different configuration and characterized by X-Ray diffraction and other techniques. Compound 1 shows a nanosize channel which is constructed by interlocked six-fold one-dimensional helical chains with the asymmetrical ligand HL1. Compared with compound 1, compound 2 shows a larger size channel with the symmetrical ligand HL2 in a single set of diamond cage. Nevertheless, the whole structure with the 4-fold interpenetrated diamondoid network leads to the absence of void space. The two compounds exhibit fascinating luminescence because of the interaction between Cd ions and organic ligands.