Assembly of a series of d10 coordination polymers of pamoic acid through a mixed-ligand synthetic strategy: syntheses, structures and fluorescence properties

Eight mixed-ligand coordination compounds, [Zn(PA)(bpp)](n) (1), {[Cd(PA)(2)(Hbpp)(2)(H2O)(2)]center dot 2H(2)O}(n) (2), [Zn(PA)(bbi)](n) (3), [Cd(PA)(bbi)(H2O)](n) (4), {[Cd-3(PA)(2)(bbi)(3)(Cl)(2)]}(n) (5), {[Zn-6(PA)(5)(datrz)(2)(Hdatrz)(2)(H2O)(2)]center dot 16DMF}(n) (6), [Cd-2(PA)(datrz)(2)(DMF)(2)](n) (7), and {[Cd-2(PA)(2)(bix)(2)(DMF)(2)]center dot 4DMF}(n) (8) (bpp = 1,3-bi(4-pyridyl)propane, bbi = 1,4-bis(imidazol-1-yl)butane, H(2)datrz = 3,5-diamino-1,2,4-triazole, bix = 1,4-bis(imidazol-1-ylmethyl)benzene), have been synthesized through the reaction of zinc and cadmium salts with pamoic acid (H(2)PA) and different N-donor ligands. The assembly of the ligands in different coordination modes and conformations leads to fascinating structures. 1 and 3 afford an interpenetrating polythreaded 2D -> 3D motif composed of 4(4) sql undulated sheets, while right- and left-helices are alternatively arranged in 3. 2 possesses an interesting 3-D supramolecular network with 1-D hydrogen-bonded chains spanning different directions. 4 and 5 display both polyrotaxane and polycatenane characteristics. In 4, two 2,4-connected (4.85) nets interlocked with each other, forming a 2D -> 2D polycatenating network. 5 exhibits a twofold interpenetrated (3,5,6)-connected (3.5.6)(3.5(2).6(7))(3(2).5(4).6(6).7(2).9) topology. 6 and 7 represent rare pentanodal (3,4)-connected and binodal (3,4)-connected frameworks with topologies of (4.5.6)(4.8.10)(5(2).6.8.9.11)(4.5.6.8.9(2))(4.5.7) and (4.6.8)(4.6(2).8(3)), respectively. 8 displays 3-fold inter-penetrated 4-connected SrAl2 topology with flexible bix ligands bridging Cd centers to form right- and left-helices. The mixed-ligand effect of the conformations of the PA ligand and N-heterocyclic coligands as well as the metal centers on the assembly of frameworks is unravelled in detail. Solid-state luminescence properties of all compounds were reported as well. Moreover, fluorescence properties of compounds 6 and 8 in various solvent suspensions at room temperature have also been investigated.