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Zinc sensor molecules containing quinoline have been synthesized, which show fluorescence in the presence of Zn2+. The nitrogen in quinoline is critical to fluorescence and fluorescence enhancement is promoted by deprotonating the sensor’s amide. One of the sensors is highly selective for Zn2+ over Cd2+ and other cations such as Hg2+, Fe2+, Mn2+ and Ca2+. This selectivity can be attributed to the increased absorption of the sensor in the presence of Zn2+ and the strong binding of Zn2+. Structural studies, including X-ray and NMR, show the ability of dipicolylamine (DPA) to bind in facial and meridional manners to Zn2+. Crystal structures of different compounds show Zn2+ coordinating to three, four, and five nitrogens from the compounds. They also indicate that the selectivity of DPA containing compounds towards Zn2+ may originate from Zn2+ being stable in different coordination environments.

Zinc-benzoates can be rationally tuned to form four different types of structures with a bridging bpe (1,2-bis(4-pyridyl)ethene) ligand by controlling zinc(benzoate)-to-ligand ratios and solvent systems, and they reveal three coordination polymers having different 1-D characteristics and a dinuclear Z-type molecule. Reactivity study of the compounds 1–4 for the transesterification of a variety of esters showed that the coordination polymers 1–3 have better activity than the discrete dinuclear molecule 4. Strong emissions of compounds 1–3 were observed at 393 nm for 1, 378 nm for 2, and 393 nm for 3, respectively, but weak luminescence was observed at 380 nm for 4 under the same experimental conditions. The thermal stabilities of these complexes were also examined.

Five new structures of HgII complexes containing Hdpa ligands have been determined. With halides, tetrahedral HgII is constructed by a Hdpa and two chlorides or bromides, and strong hydrogen bonds between amine hydrogen atoms and halide atoms provide dimeric compounds. With benzoates, distorted octahedral HgII is constructed by a Hdpa and two chelating benzoate ligands, and hydrogen bonding and π–π interactions provide a polymeric compound. With nitrates or perchlorates, two dpa ligands bridge two HgII ions, and counter-anions axially coordinate to HgII ions to form a polymeric compounds. In addition, all five HgII complexes showed the intense emissions at room temperature, which are red-shifted compared to the corresponding ligand. Moreover, 3 and 4 have shown efficient catalytic transesterification recation, while 1, 2 and 5 has displayed a very slow conversion.

The reaction of Cd(NO3)2 and CF3COONH4 with bpe (trans-1,2-(bis(4-pyridyl)ethene)) ligands was investigated for a light-induced solid-state [2+2] cycloaddition reaction. The three structures (1 [Cd(bpe)2(CF3COO)2]n, 2 [Cd(bpe)2(NO3)2]n, and 3 [Cd(NO3)(μ-NO3)(H2O)(bpe)1.5]n) formed in light while only compound 1 (or 1-dark) was formed in the dark. All three compounds were completely transformed to the final [2+2] cycloaddition products containing rctt-tetrakis(4-pyridyl)cyclobutane (rctt-tpcb; rctt means regional cis, trans, and trans of the four pyridyl groups attached to the cyclobutane ring) in solution under a natural light after 4 weeks. Among the final products, only one 3-D structure (4 [{Cd(rctt-tpcb)2(NO3)2}{Cd(rctt-tpcb)2(OH)2}]n) with a good crystallinity was determined by the X-ray diffraction technique. These observations were also in line with the spectroscopic results such as 1H NMR. Meanwhile, 3 was also prepared separately and exposed to natural light. X-ray and NMR studies showed that 3 was completely transformed to 4 containing rctt-tpcb by a light-induced cycloaddition reaction for the 4 weeks. The reaction progress was further monitored by fluorescent spectroscopy. 1-dark also underwent the solid-state [2+2] cycloaddition under the natural light over four weeks.

Chemosensors are developed to image zinc ions. Fluorescence enhancement due to Zn2+ binding is an excellent way to detect its presence. A chemosensor for Zn2+ based on dipicolylamine (DPA) groups connected by a pyridyl amide backbone has been synthesized. Addition of 2-chloroacetyl chloride to 2,6-diaminopyridine affords 2,6-bis(chloroethylamido)pyridine, which is converted to the sensor BADPA-P by 2,2′-dipicolylamine displacement of chlorine. This compound along with two others, the mono-DPA, ADPA-P and the benzyl in place of pyridyl, BADPA-B, present three potential Zn2+ sensors. It was found that BADPA-P in the presence of Zn2+ shows a large increase in fluorescence, whether in polar organic or aqueous environments. Its fluorescence in the presence of Cd2+, unlike with Zn2+, is not enhanced when excited at longer wavelengths. Proton NMR measurements, indicate two Zn2+ ions bind to BADPA-P. Also, Zn2+ enhances fluorescence even when other metal ions are present.

Six new structures of ZnII complexes containing 2,2′-bipyridine (2,2′-bpy) ligands have been determined. Halide anions were used as simple coordinating ligands to form a tetrahedral environment around the ZnII ion. Nitrate and benzoate anions were used as chelating ligands to form an octahedral environment. For non-coordinating ClO 4 - and bridging SO 4 2 - anions, three 2,2′-bpy ligands chelate ZnII to form an octahedral environment, and both ClO 4 - and SO 4 2 - anions occupy empty positions between the metal cations for charge balance. Polymeric structures of the ZnII–2,2′-bpy complexes are produced by hydrogen bonding. [Zn(2,2′-bpy)(O2CC6H5)2] catalyzed efficiently the transesterification reaction of esters with methanol under the neutral conditions, while the remaining compounds showed very slow conversions.

New chromogenic anion receptors 2 and 4 utilizing quinoline and nitrophenyl groups as signaling groups were synthesized. In these receptors, amide and amine groups made strong multiple hydrogen interactions with anions. The receptors 2 and 4 bind anions with a selectivity of F− > CN− > CH 3 CO 2 - and proved to be an efficient naked-eye detector for the fluoride and cyanide ion.

Three new Cd(II) complexes containing 3-bpdb ligands with amide moiety as hydrogen-bond capable backbone, formulated as [Cd(3-bpdb)X 2 ] n (3-bpdb = N,N′-dipyridin-3-ylpyridine-2,6-dicarboxamide, X = Cl ( 1 ), Br ( 2 ), and I ( 3 )), have been synthesized. All three compounds show 1-dimensional looped chain structures, and intra- and inter-molecular hydrogen bonding interactions provide 2-dimensional sheets. Among three pausible conformers of ligand 3-bpdb, all three halide compounds show only anti – anti conformation to provide 1-dimensional looped chains. In addition, emissions of compounds 1 and 2 were observed at 424 nm and 431 nm, respectively, suggesting that they might be a good candidate for a potential hybrid inorganic – organic photoactive material. Moreover, compounds 1–3 carried out an efficient transesterification of vinyl acetate.

The synthesis, spectroscopic characterisation, conformational switching and fluorescence quenching efficiency of a resorcinarene-based cavitand containing Zn-salen (Zn-Cav) are reported. Synthesis of Zn-Cav was accomplished by the condensation of a quinoxaline derivatised with Zn-salen and a resorcinarene-based cavitand containing three quinoxalines. 1H NMR spectroscopy confirmed that in DMSO, chloroform and acetone Zn-Cav resides in the vase conformation. The molecular geometry of Zn-Cav selectively changes from vase to kite under acidic conditions. Detection by fluorescence quenching of nitro-containing molecules, such as 4-nitrotoluene, 2,4-dinitrotoluene and 2,3-dimethyl-2,3-dinitrobutane was explored by spectrofluorimetry. It was found that the fluorescence of Zn-Cav is efficiently quenched by nitroaromatic compounds.

A mononuclear nonheme cobalt(III) complex of a tetradentate ligand containing two deprotonated amide moieties, [Co(bpc)Cl(2)][Et(4)N] (1; H(2)bpc = 4,5-dichloro-1,2-bis(2-pyridine-2-carboxamido)benzene), was prepared and then characterized by elemental analysis, IR, UV/Vis, and EPR spectroscopy, and X-ray crystallography. This nonheme Co(III) complex catalyzes olefin epoxidation upon treatment with meta-chloroperbenzoic acid. It is proposed that complex 1 shows partitioning between the heterolytic and homolytic cleavage of an O-O bond to afford Co(V)=O (3) and Co(IV)=O (4) intermediates, proposed to be responsible for the stereospecific olefin epoxidation and radical-type oxidations, respectively. Moreover, under extreme conditions, in which the concentration of an active substrate is very high, the Co-OOC(O)R (2) species is a possible reactive species for epoxidation. Furthermore, partitioning between heterolysis and homolysis of the O-O bond of the intermediate 2 might be very sensitive to the nature of the solvent, and the O-O bond of the Co-OOC(O)R species might proceed predominantly by heterolytic cleavage, even in the presence of small amounts of protic solvent, to produce a discrete Co(V) O intermediate as the dominant reactive species. Evidence for these multiple active oxidants was derived from product analysis, the use of peroxyphenylacetic acid as the peracid, and EPR measurements. The results suggest that a less accessible Co(V)=O moiety can form in a system in which the supporting chelate ligand comprises a mixture of neutral and anionic nitrogen donors.

Zinc sensors based on 2,3-dipicolylamine (DPA) and quinoline have been synthesized. They fluoresced in the presence of Zn(2+) and remained fluorescent when other metal ions were present. Fluorescence enhancement of the sensors was not seen for most other metal ions. In vitro studies with fibroblasts showed fluorescence when sensor and Zn(2+) were present. As seen by single crystal X-ray analysis, four nitrogens from the sensor bind to Zn(2+). These new sensors have lower binding constants than the pentadentate sensors based on 2,2-DPA.

Six ZnII–(e,a-cis-1,2-chdc) complexes, [Zn2(1,2-chdc)2(2,2′-bpy)2(H2O)2]·H2O 1, [{Zn2(1,2-chdc)2(H2O)2(μ-bpa)}·4H2O]n2, [{Zn2(μ-1,2-chdc)2(μ-4,4′-bpy)}·3CH3OH]n3, [{Zn2(μ-1,2-chdc)2(μ-bpe)}·2H2O]n4, [[{Zn2(μ-1,2-chdc)2}n-(μ-bpp)-{Zn2(μ-1,2-hdc)2(H2O)2}]·CH3CN·2H2O]n5, and [{Zn2(μ-dtp)2(μ-1,2-chdc)}2·4·5H2O]n6 (1,2-chdc = 1,2-cyclohexanedicarboxylate), with different assistant ligands (2,2′-bipyridine (2,2′-bpy), 1,2-bis(4-pyridyl)ethane (bpa), 1,2-bis(4-pyridyl)ethylene (bpe), 1,3-bis(4-pyridyl)propane (bpp), and, 4,4′-bipyridine (4,4′-bpy) and 4,4′-dithiodipyridine (dtp)) have been synthesized and their structures were determined. Depending on the assistant ligands, the structures and dimensionalities of ZnII–(e,a-cis-1,2-chdc) complexes have been varied. Two carboxylates in e,a-cis-1,2-chdc coordinate to ZnII ions with (11) or (10) connectivity. Photoluminescence study of the compounds 1–6 showed that emission spectra of compounds 1, 2, 4, and 5 were observed at 343 nm for 1, 419 nm for 2, 507 nm for 4, 396 nm for 5, respectively, while no obvious luminescences were displayed for 3 and 6. In addition, it has been found that compound 1 catalyzed the transesterification reaction of phenyl acetate with methanol, with quantitative conversion to methyl acetate, under the neutral conditions, while compounds 2–6 showed very slow conversions. The thermal stabilities of these complexes were also examined.