| Abstract: Five cadmium naphthalene-diphosphonates, formulated as [Cd1.5(1,4-ndpaH2)2(4,4'-bpyH)(4,4'-bpy)0.5 (H2O)2]2 (1), [Cd(1,4-ndpaH2)(1,4-bib)0.5(H2O)] (2), [Cd(1,4-ndpaH3)2(1,2-dpe)(H2O)]·(1,2-dpe)·7H2O (3), (1,2-bixH) [Cd3(1,4-ndpaH)(1,4-ndpaH2)2(H2O)2] (4), and [Cd(1,4-ndpaH2)(H2O)]·H2O (5), have been synthesized from the selfassembly reactions of 1,4-naphthalenediphosphonic acid (1,4-ndpaH4) with Cd(NO3)2·4H2O by introducing auxiliary ligands with variation of rigidity, such as 4,4'-bipyridine (4,4'-bpy), 1,4-bis(1-imidazolyl)benzene (1,4-bib), 1,2-di(4pyridyl)ethylene (1,2-dpe), 1,3-di(4-pyridyl)propane (1,3-dpp), and bis(imidazol-1-ylmethyl)benzene (1,2-bix), respectively. Structure resolution by single crystal X ray diffraction reveals that compound 1 possesses a layered framework, in which the {Cd3(PO2)2} trimers made up of corner-sharing two {CdO4N2} and one {CdO6} octahedra are connected by phosphonate groups, forming a ribbon, which are cross-linked by 4,4'-bipy ligands, forming a 2D layer. Compound 2 shows a 3D open-framework structure, where chains of corner-sharing {CdO4N} trigonal bipyramids and {PO3C} tetrahedra are cross-linked by 1,4-bib and/or phosphonate groups. A 1D ladder-like chain structure is found in compound 3, where the ladder-like chains made up of corner-sharing {CdO5N} octahedra and {PO3C} tetrahedra are connected by 1,4-ndpaH22-. Both compounds 4 and 5 obtained by the introduction of flexible ligands during the synthesis show a 2D layered structure, which is formed by ligand crosslinking double metal chains. Interestingly, In 4, flexible 1,2-bix was singly protonated, as guest molecules, filled between layer and layer, while flexible ligand 1,3-dpp is absent in 5. Photophysical measurements indicate that compounds 1-5 show ligand-centered emissions. |
