pH modulated assembly in the mixed-ligand system Cd(II)-dpstc-phen: structural diversity and luminescent properties

Hydrothermal reaction of cadmium salt, 3,3',4,4'-diphenylsulfonetetracarboxylic acid (H(4)dpstc) and 1,10-phenanthroline (phen) under different pH conditions have afforded four novel supramolecular complexes, in which the pH value of the reaction solution plays a crucial structure-directing role. [Cd(H(2)dpstc)(phen)](n) (1) formed in a neutral reaction environment exhibits a 1D infinite chain structure containing partially deprotonated H(2)dpstc(2-) as the H-bond donors and acceptors. Whereas [Cd-2(dpstc)(phen)(2)](n)center dot 4.5nH(2)O (2), [Cd-2(dpstc)(phen)(2)](n)center dot nH(2)O (3) and [Cd-2(dpstc)(phen)(4)(H2O)(2)]center dot 6H(2)O (4) contain fully deprotonated dpstc(4-) ligands due to the alkaline reaction conditions. Complex 2 possesses a unique 2D layered structure with 1D channels. The most striking feature of 2 is that its 2D holed (4,4)-water-net is constructed from hexameric water clusters and two types of dimeric water clusters. Surprisingly, the water net and the metal-organic skeleton are interpenetrated to form a fascinating 3D metal-organic-water supramolecular architecture. A further increase of the pH value leads to another 2D layered framework of 3 containing dumbbell-shaped rings as subunits. Reaction at a strongly alkaline solution leads to a discrete molecule of 4. Meanwhile solid-state properties such as thermal stability and the photoluminescence properties at room temperature for these complexes have also been systematically investigated.