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By using a flexible multicarboxylate ligand, 2,2′-(2-((2-carboxy-5-methylphenoxy)methyl)-2-(4-methylphenylsulfonamido)propane-1,3-diyl)bis(oxy)bis(4-methylbenzoic acid) (H3L), and two kinds of N-donor ligands, four new zinc(II) and cadmium (II) metal coordination complexes [Zn2(HL2−)2(phen)2]·2H2O (1), [Zn(HL2−)(4,4′-bpy)0.5(H2O)]n (2), [Cd(HL2−)(phen)(H2O)]n (3), and [Cd2(HL2−)2(4,4′-bpy)3]n·n(DMF·CH3OH·H2O) (4) (phen = 1,10-phenanthroline, and 4,4′-bpy = 4,4′-dipyridine) have been prepared under solvothermal conditions and structurally characterized by elemental analysis, FT-IR spectra, thermogravimetric analysis. The various topologies of the structures have been generated by adjusting the auxiliary N-donor ligand and the central metal ions. Complex 1 features a discrete neutral dinuclear cage structure, complex 2 displays a 1D ladder-like chain, complex 3 exhibits a 1D infinite zigzag chain, while complex 4 possesses a rare 5-connected 2D networks with the point symbol (48·62). These results indicate that both the metal center and the auxiliary N-donor ligand have significant influences on the structure of the final assembly. Moreover, the thermal stabilities and luminescent properties of 1–4 have also been investigated in detail.

Three complexes with the ditopic ligand 4′-[4-(quinolin-8-yloxymethyl)phenyl]-2,2′:6′,2′′-terpyridine (abbreviated as L), [Ni(L)2](CH3COO)2 (1), [Cd(L)2](ClO4)2 (2), and [Cu2(L)2](ClO4)4·4DMF (3), were synthesized and characterized by elemental analysis, IR spectroscopy, and structurally analyzed by X-ray single-crystal diffraction. Interestingly, in complexes 1 and 2, two ligands adopt a tridentate chelating pattern where the oxaquinoline group is non-coordinated and coordinate with one MII ion (M = Ni for 1, M = Cd for 2) to form a mononuclear unit. In complex 3, two ligands bridge two CuII ions by pyridyl N atoms, ethereal O atoms, and quinolyl N atoms in a head-to-tail mode to generate a dinuclear [Cu2L2] unit. Moreover, extended 1D and 2D supramolecular architectures are further constructed in 1–3 by multiple secondary interactions such as aromatic stacking and hydrogen bonding. Notably, the structural diversity of complexes 1–3 can be properly assigned to the central metal ions that have distinct coordination preferences. In addition, luminescent properties of the ligand and complex 2 were also investigated.

A simple quinoline-based fluorescent probe L for Ag+ has been developed. Probe L shows fluorescence enhancement (turn on) response towards Ag+ with high selectivity in aqueous media (methanol–water, v/v = 3:7, pH 7.2, 20 mM Tris–HCl) based on a combinational effect of the inhibition of intermolecular photoinduced proton transfer and chelation-enhanced fluorescence. And an obvious fluorescent color change could be observed by naked eyes under the light of 365 nm. The binding mode between L and Ag+ has been found to be 1:1 based on the fluorescence/absorption titration, ESI-MS and further confirmed by X-ray crystallography.

A full account of our studies of 2,4,6-trinitrophenol (TNP) sensing is provided. A series of chemosensors with a variety of aromatic chromophores for specific recognition of TNP has been designed and then realized through the fluorescence "on/off" mechanism. These chemosensors demonstrated highly selective, sensitive, and fluorescent quenching of TNP with remarkable visual changes through the intramolecular charge-transfer (ICT) process. Their host-guest interactions were investigated by (1)H NMR spectroscopic titrations and their corresponding co-crystal structures, which showed that the 1:1 host-guest complexes were formed by multiple hydrogen-bond interactions in solution or in the solid state. The origins of the significant affinity demonstrated during the fluorescence recognition process were further disclosed through DFT calculations of corresponding compounds.

Several rhodamine-B (C.I. Basic Violet 10) hydrazide derivatives were employed as specific fluorescent and colorimetric chemosensors for Cu 2+ in neutral buffered media. The probes exhibited selective “off-on” type changes in both absorption and emission spectra toward Cu 2+ ions compared to other metal cations, which was attributed to transformation of the non-fluorescent and colorless spirolactam derivative to the ring-opened, fluorescent, pink coloured amide. Further studies of structure-activity relationship revealed that the designated acyl hydrazone skeleton moiety shared by these chemosensors, derived from the dye hydrazide and salicylaldehyde analogues, determines the selectivity for Cu 2+ over other cations.

A chiral BINOL derivative bearing Schiff’s base group has been synthesized for the selective fluorescent recognition of Hg2+. Highly selective “turn-on” type fluorescence changes were observed upon the addition of Hg2+. The fluorescence intensity enhancement was ascribed to the complex formation between (R)-1 and Hg2+ which blocked the photo-induced electron transfer process.

A new Tb(III) complex based on a tripodal carboxylate ligand has been synthesized for the selective fluorescent recognition of phosphate anions, including inorganic phosphates and nucleoside phosphates (e.g., ATP), in Tris buffer solution. The resulting L · Tb complex shows the characteristic emission bands centered at about 495 and 550 nm from the Tb(III)-centered (5)D4 excited state to (7)FJ transitions with J = 6 and 5, where the chelating ligand acts only as an "antenna". Upon the addition of phosphate anions to the aqueous solution of Tb(III) complex, significant "on-off" fluorescence changes were observed, which were attributed to the inhibition of the "antenna" effect between the ligand and Tb(III) after the incorporation of phosphate anions. Furthermore, this unique Tb(III) complex has been successfully utilized to detect phosphate anions with filter papers and hydrogels. Notably, the Tb(III) complex also can be used for the construction of molecular logic gates with TRANSFER and INHIBIT logic functions by using the above fluorescence changes.

Two novel binaphthyl compounds have been synthesized for the selective fluorescent recognition of Ca2+ or Pb2+. By introducing different terminal groups to the receptor unit, the fluorescence signals of the receptors are significantly changed: 1 is fluorescence enhancement for Ca2+, 2 is fluorescence quenching for Pb2+. The binding properties for metal ions were examined by the absorption and fluorescence spectra. The fluorescence intensity enhancement was ascribed to the complex formation between Ca2+ and 1 which blocked the photo-induced electron transfer process.

In the binuclear title complex, [Ag(2)(C(31)H(22)N(4)O)(2)](ClO(4))(2)·2C(3)H(7)NO, the Ag(I) atom is penta-coordinated by three N atoms from the tridentate chelating terpyridyl group and by one N atom and one O atom from the quinolin-8-yl-oxy group in a distorted square-pyramidal geometry with the O atom at the apical position. The centrosymmetric complex cation involves intra-molecular π-π stacking inter-actions [centroid-centroid distance = 3.862 (4) Å] between the central pyridine and benzene rings. In the crystal structure, inter-molecular C-H⋯O hydrogen bonds result in the formation of a supra-molecular network.

A fluorescent and colorimetric receptor (L) for specific recognition of TNP was described. The origins of this remarkable affinity was disclosed by the crystal structure of corresponding host-guest complex L·TNP.

Six new homodinuclear lanthanide(III) complexes with a flexible tripodal carboxylate ligand (H(3)L), of formulae [Ln(2)L(2)(DMF)(4)]·4DMF (Ln = La (1), Nd (2), Eu (3), Gd (4), Tb (5), Dy (6), DMF = N, N-Dimethylformamide) have been synthesized. Among them, 1, 2, 3, 4, 6 were characterized by single-crystal X-ray diffraction, which crystallized in the monoclinic space group P2(1)/n with a = 13.309(2) Å, b = 27.404(4) Å, c = 16.686(3) Å, β = 105.115(2) and V = 5875.2(17) Å(3) for 1, a = 13.3016(5) Å, b = 27.1952(12) Å, c = 16.6339(7) Å, β = 105.030(2) and V = 5811.3(4) Å(3) for 2, a = 13.2797(10) Å, b = 27.072(2) Å, c = 16.6564(13) Å, β = 104.9390(10) and V = 5785.7(8) Å(3) for 3, a = 13.2855(3) Å, b = 27.0074(6) Å, c = 16.6357(3) Å, β = 104.9790(10) and V = 5766.2(2) Å(3) for 4, a = 13.2837(5) Å, b = 26.9105(10) Å, c = 16.6066(6) Å, β = 104.917(2) and V = 5736.3(4) Å(3) for 6. The crystal structures reveal that these complexes are isostructural, and molecules are connected from 0D to 3D supramolecular structures by hydrogen bonds. All of them were characterized by elemental analysis, IR spectroscopy, XRD and TGA. Unusually, non-luminescent Tb(III) complex was obtained. The photophysical property of the Eu(III) complex and the magnetic property of Gd(III) complex are investigated and discussed in detail.

The molecule of the title compound, C30H24N2O2S4, adopts a Z-shaped conformation. The terminal benzothiazole ring systems are oriented at a dihedral angle of 60.81 (8)°, while the central benzene rings are twisted to each other by a dihedral angle of 13.56 (14)°. Weak intermolecular C—H...π interactions are present in the crystal structure.

Five new rare earth complexes with a new flexible tripodal salicylic ligand (H(3)L), 2,2'-(2-((2-carboxyphenoxy)methyl)-2-(4-methylphenylsulfonamido)propane-1,3-diyl)bis(oxy)dibenzoic acid, of formulae [La(2)L(2)(DMF)(4)]·4DMF·4EtOH·2H(2)O (1), [Eu(2)L(2)(DMF)(4)]·2DMF (2), {[GdL(DMF)(H(2)O)(2)]·DMF}(∞) (3), {[TbL(DMF)(H(2)O)(2)]·DMF}(∞) (4) and {[YL(DMF)(H(2)O)(2)]·DMF}(∞) (5) (DMF = N,N-dimethylformamide) have been prepared. The single-crystal X-ray diffraction analysis revealed that complexes 1 and 2 present a cage-like homodinuclear species, while 3-5 show a helical one-dimensional coordination polymer. All these complexes are further connected by hydrogen bonds or π-π interactions, resulting in 3D supramolecular structures. The photophysical properties of the Eu and Tb complexes are investigated in the solid state at room temperature.