A highly selective fluorescent sensor for distinguishing cadmium from zinc ions based on a quinoline platform

A fluorescent sensor, N-(quinolin-8-yl)-2-(quinolin-8-yloxy)acetamide (HL), based on 8-aminoquinoline and 8-hydroxyquinoline platforms has been synthesized. This sensor displays high selectivity and sensitive fluorescence enhancement to Cd(2+) in ethanol. Moreover, sensor HL can distinguish Cd(2+) from Zn(2+) via two different sensing mechanisms (photoinduced electron transfer for Cd(2+); internal charge transfer for Zn(2+)). The composition of the complex Cd(2+)/HL or Zn(2+)/L(-) has been found to be 1:1, based on the fluorescence/absorption titration and further confirmed by X-ray crystallography.     

A Two‐Dimensional Coordination Compound as a Zinc Ion Selective Luminescent Probe for Biological Applications

A 2D coordination compound {[Cu₂(HL)(N₃)]?ClO₄}_∞ ( 1 ; H₃L=2,6‐bis(hydroxyethyliminoethyl)‐4‐methyl phenol) was synthesized and characterized by single‐crystal X‐ray diffraction to be a polymer in the crystalline state. Each [Cu₂(HL)(N₃)]⁺ species is connected to its adjacent unit by a bridging alkoxide oxygen atom of the ligand to form a helical propagation along the crystallographic a axis. The adjacent helical frameworks are connected by a ligand alcoholic oxygen atom along the crystallographic b axis to produce pleated 2D sheets. In solution, 1 dissociates into [Cu₂(HL)₂(H₃L)]?2H₂O ( 2 ); the monomer displays high selectivity for Zn²⁺ and can be used in HEPES buffer (pH 7.4) as a zinc ion selective luminescent probe for biological application. The system shows a nearly 19‐fold Zn²⁺‐selective chelation‐enhanced fluorescence response in the working buffer. Application of 2 to cultured living cells (B16F10 mouse melanoma and A375 human melanoma) and rat hippocampal slices was also studied by fluorescence microscopy.     

Synthesis, spectral and electrochemical properties of Al(III) and Zn(II) complexes with flavonoids

The synthesis, electrochemical and spectral (UV-vis, 1H NMR, IR, fluorescence) properties as well as thermal behaviors of Al(III) and Zn(II) complexes with the flavonoids quercetin (H2L(1)), rutin (H2L(2)) and galangin (HL(3)) are presented. The complexes may be formulated as [Al2(L(1))(H2O)8]Cl4, [Al3(L(2))2(H2O)12]Cl5, [Al(L(3))(H2O)4]Cl2, [Zn2(L(1))(H2O)4]Cl2, [Zn3(L(2))2(H2O)6]Cl2 and [Zn(L(3))(H2O)2]Cl. The higher fluorescence intensities of the complexes related to the free flavonoids, are attributed to the coordination of the ligands to the small, highly charged Al(III) and Zn(II) ions. The coordination effectively increases the rigidity of the ligand structure and increases the fluorescence quantum yield by reducing the probability of non-radiative energy dissipation process. Antioxidant activities of the compounds were also investigated under an electrochemical point of view. The cyclic voltammetric data show a considerable decrease of the oxidation potentials of the complexes related to that of the free flavonoids. Thus, the flavonoid-metal complexes are more effective antioxidants than the free flavonoids.     

Binding of H+ and Zn(II) ions with a new fluorescent macrocyclic phenanthrolinophane

The new macrocyclic ligand 1,9(4,7)-diphenanthroline-3,7,11,15-tetraazacyclohexadecaphane (L) was synthesized by a 2?:?2 reaction of 1,10-phenanthroline-4,7-dialdehyde with 1,3-diaminopropane, followed by reduction with NaBH(4). L contains two phenanthroline groups linked together by two 1,3-diaminopropane chains in such a way that the heteroaromatic nitrogen atoms point outside the ligand cavity. The ligand structure defines two pairs of identical compartments displaying a specific ability in the binding of protons (1,3-diaminopropane) and metal ions (phenanthroline). Protonation and Zn(II) coordination were studied by means of potentiometric and spectroscopic ((1)H NMR, UV-vis, fluorescence) techniques. Both protonation and Zn(II) coordination consistently affect the fluorescence emission properties of L, giving rise to enhancement or quenching of the emission, depending on the species involved. L becomes emissive upon protonation, but the formation of the highly protonated species, in particular the fully protonated [H(6)L](6+), quenches the emission. The mono- and dinuclear Zn(II) complexes of the unprotonated ligand are non-emissive, like free L, while Zn(II) binding to [HL](+) activates the emission. The most interesting aspect, however, is the chelation enhancement of quenching (CHEQ) observed upon Zn(II) binding to [H(2)L](2+) and [H(4)L](4+), being among the few examples of CHEQ effect observed for Zn(II) complexes. Hydrogen bonding between a metal coordinated water molecule and a phenanthroline group seems to be responsible for the CHEQ observed for [ZnH(2)L](4+).     

Hydrothermal synthesis, structures, and photoluminescent properties of benzenepentacarboxylate bridged networks incorporating zinc(II)-hydroxide clusters or zinc(II)-carboxylate layers

The first coordination compounds of partially or wholly deprotonated benzenepentacarboxylic acid (H5L) were synthesized in the presence or absence of auxiliary 2,2'-bipyridyl (2,2'-bpy) and 1,10-phenanthroline (phen) ligands, and their crystal structures and photoluminescent properties were characterized. Their formulas are [Zn6(mu3-OH)2(L)2(H2O)6]n (1), [Zn5(mu3-OH)2(HL)2(2,2'-bpy)2]n (2), [Zn2(HL)(phen)2(H2O)2]n (3), and [Zn5(L)2(phen)4(H2O)3]n.2nH2O (4). Both 1 and 2 are three-dimensional (3D) zinc(II)-hydroxide cluster based coordination frameworks. 1 contains distorted chairlike hexanuclear Zn6(mu3-OH)2 cluster units as secondary building blocks. Each Zn6(mu3-OH)2 unit connects six others through the three-connected nodes of L5- ligands into a 3D rigid and condensed coordination network, whereas in 2, each pentanuclear Zn5(mu3-OH)2 unit connects the other six ones through the three-connected [HL]4- nodes into a 3D network in the simple cubic packing mode. 3 has two-dimensional (2D) Zn(II)-carboxylate supramolecular layers constructed from a one-dimensional (1D) coordination chain structure by hydrogen bonds of the water and mu5-[HL]4- bridges, whereas 4 has 2D coordination layers composed of Zn(II) and mu8-L5- bridges. The adjacent coordination assemblies in 3 and 4 are further extended by hydrogen bonds and pi...pi interactions into 3D supramolecular architectures. 1-4 are photoluminescent active materials, and their photofluorescent properties are closely related to their intrinsic structure arrangements.     

吡咯并[2,1,5-cd]中氮茚酰腙衍生物的合成及Cu2+荧光探针行为

设计合成了吡咯并[2,1,5-cd]中氮茚酰腙衍生物6. 测试了其紫外光谱和荧光光谱, 研究了其对铜离子的选择性识别作用. 结果表明, 化合物6作为铜离子荧光探针, 受常见离子干扰较小, 对于铜离子有着较高的选择性和较低的检出限.     

Boron dipyrromethene fluorophore based fluorescence sensor for the selective imaging of Zn(II) in living cells

A simple PET fluorescence sensor (BDA) for Zn2+ that utilizes 1,3,5,7-tetramethyl-boron dipyrromethene as a reporting group and di(2-picolyl)amine as a chelator for Zn2+ has been synthesized and characterized. BDA has an excitation (491 nm) and emission wavelength (509 nm) in the visible range. The fluorescence quantum yields of the zinc-free and zinc-bound states of BDA are 0.077 and 0.857, respectively. With a low pKa of 2.1 +/- 0.1, BDA has the advantage of less sensitivity to pH than fluorescein-based Zn2+ sensors, and the fluorescence emission of zinc-binding is pH-independent in the range of pH 3-10. Under physiological conditions, metal ions such as Na+, K+, Ca2+, Mg2+, Mn2+ and Fe2+ have little interference. The apparent dissociation constant (Kd) is 1.0 +/- 0.1 nM. Using fluorescence microscopy, the sensor is shown to be capable of imaging intracellular Zn2+ changes.     

Selective fluorescent probes based on CN isomerization and intramolecular charge transfer (ICT) for zinc ions in aqueous solution

As the second most abundant transition-metal ion in the human body, Zn2+ plays crucial roles in many important biological processes; while in the environment, an excessive concentration of Zn2+ may reduce the soil microbial activity resulting in phytotoxic effects. Therefore, developing effective and sensitive detection method for Zn2+ has become crucially important and necessary both in life and environment science. Two new fluorescence probes, 2-((2-hydroxynaphthalen-1-yl)methyleneamino)-3-(1H-imidazol-5-yl) propanoic acid (2) and 2-hydroxy-2-((2-hydroxynaphthalen-1-yl) methyleneamino) acetic acid (3), were easily prepared by a one step reaction between 2-hydroxy-1-naphthaldehyde with histidine and serine, respectively, in ethanol. The optical properties of them were investigated by fluorescence spectra, which displayed specific and sensitive recognition to Zn2+ and especially avoided the interference of Cd2+ when they were tested against a range of physiological and environmentally relevant metal ions in aqueous solution. The responsive mechanism of the two probes to Zn2+ were involved both the CN isomerization and ICT, which were clarified by NBO charge analysis and the HOMO-LUMO energy gap calculation by using B3LYP/6-31G density functional theory.     

A new fluorescent probe for zinc(II): an 8-hydroxy-5-N,N-dimethylaminosulfonylquinoline-pendant 1,4,7,10-tetraazacyclododecane

A new fluorescent probe for Zn2+, namely, 8-hydroxy-5-N,N-dimethylaminosulfonylquinolin-2-ylmethyl-pendant cyclen (L8), was designed and synthesized (cyclen=1,4,7,10-tetraazacyclododecane). By potentiometric pH, 1H NMR, and UV spectroscopic titrations, the deprotonation constants pKa1-pKa6 of L(8)4 HCl were determined to be <2, <2, <2 (for amino groups of the cyclen and quinoline moieties), 7.19+/-0.05 (for 8-OH of the quinoline moiety), 10.10+/-0.05, and 11.49+/-0.05, respectively, at 25 degrees C with I=0.1 (NaNO3). The results of 1H NMR, potentiometric pH, and UV titrations, as well as single-crystal X-ray diffraction analysis, showed that L8 and Zn2+ form a 1:1 complex [Zn(H-1L8)], in which the 8-OH group of the quinoline ring of L8 is deprotonated and coordinates to Zn2+, in aqueous solution at neutral pH. On addition of one equivalent of Zn2+ and Cd2+, the fluorescence emission of L8 (5 microM) at 512 nm in aqueous solution at pH 7.4 [10 mM HEPES with I=0.1 (NaNO3)] and 25 degrees C increased by factors of 17 and 43, respectively. We found that the cyclen moiety has the unique property of quenching the fluorescence emission of the quinolinol moiety when not complexed with metal cations, but enhancing emission when complexed with Zn2+ or Cd2+. In addition, the Zn2+-L8 complex [Zn(H-1L8)] is much more thermodynamically and kinetically stable (Kd{Zn(H-1L8)}=[Zn2+]free[L8]free/[Zn(H-1L8)]=8 fM at pH 7.4) than the Zn2+ complexes of our previous Zn2+ fluorophores ([Zn(H-1L2)] and [Zn(L3)]). Furthermore, formation of [Zn(H-1L8)] is much faster than those of [Zn(H-1L2)] and [Zn(L3)]. The staining of early-stage apoptotic cells with L8 is also described.     

1D, 2D and 3D luminescent zinc(II) coordination polymers assembled from varying flexible thioether ligands

Using a series flexible thioether ligands, 4-(2-pyridylmethylthio)benzoic acid (HL(1)), 4-(4-pyridylmethylthio)benzoic acid (HL(2)) and 4-(3-pyridylmethylthio)benzoic acid (HL(3)), a 1D infinite chain [Zn(3)(L(1))(6)](n) (), a 2D interpenetrating sheet [Zn(L(2))(2)](n) (), and a chiral 3D framework [Zn(L(3))(2)H(2)O](n) () were obtained. Luminescent properties of these compounds were also studied.     

Spectrophotometric study of the complex formation of 3-(2-hydroxyphenyl)-2-mercaptopropenoic acid with Ni(II) and Zn(II)

The dissociation and complex formation equilibria between Ni(II) and Zn(II) with 3-(2-hydroxyphenyl)-2-mercaptopropenoic acid, at 25 degrees in aqueous 0.1 and 1.0M sodium perchlorate solutions, containing about 1% ethanol, have been studied spectrophotometrically. The data were connected directly from the spectrophotometer to an IBM-PC via a serial interface, using the DUMOD program (written in BASIC), described in the paper. The obtained spectra were treated by the factor analysis program NIPALS in order to determine the number of absorbing species and the experimental error. Dissociation constants of ligand (H(3)L), and formation constants for the complexes Ni(HL), Ni(HL)(2), Zn(HL) and Zn(HL)(2) at 0.1 and 1.0M ionic strengths, refined by the SQUAD program, are reported.     

A photometric study of the complexation reaction between Alizarin complexan and zinc(II), nickel(II), lead(II), cobalt(II) and copper(II)

The complexation reaction between Alizarin complexan ([3-N,N-di(carboxymethyl)aminomethyl]-1,2-dihydroxyanthraquinone; H(4)L) and zinc(II), nickel(II), lead(II), cobalt(II) and copper(II) has been studied by a spectrophotometric method. All these metal ions form 1:1 complexes with HL; 2:1 metal:ligand complex were found only for Pb(II) and Cu(II). The stability constants are (ionic strength I = 0.1, 20 degrees C): Zn(2+) + HL(3-) right harpoon over left harpoon ZnHL(-) log K +/- 3sigma(log K) = 12.19 +/- 0.09 (I = 0.5) Ni(2+) + HL(3-) right harpoon over left harpoon NiHL(-) log K +/- 3sigma(log K) = 12.23 +/- 0.21 Pb(2+) + HL(3-) right harpoon over left harpoon PbHL(-) log K +/- 3sigma(log K) = 11.69 +/- 0.06 PbHL(-) + Pb(2+) right harpoon over left harpoon Pb(2)L + H(+) log K approximately -0.8 Co(2+) + HL(3-) right harpoon over left harpoon CoHL(-) log K 3sigma(log K) = 12.25 + 0.13 Cu(2+) + HL(3-) right harpoon over left harpoon CuHL(-) log K 3sigma(log K) = 14.75 +/- 0.07 Cu(2+) + CuHL(-) right harpoon over left harpoon Cu(2)L + H(+) log K approximately 3.5 The solubility and stability of both the reagent and the complexes and the closenes of the values of the stability constants make this reagent suitable for the photometric detection of several metal ions in the eluate from an ion-exchange column.     

One-and Two-photon Excited Fluorescence of Zinc(II),Cadmium(II)Complexes Containing Phenothiazine Ligand

In fluorescence imaging, two-photon excitation (TPE) has developed as an important alternative to traditional one-photon excitation (OPE) in fluorescence microscopy and spectroscopy1,2. The intrinsic advantages of the two-photon excitation include reduced background fluorescence from fluorophores outside the focal volume, decreased photobleaching, inherent optical sectioning capability, and lower photodamage of sensitive biological sample3. But, all the reported materials, which exhibit a …     

One—and Two—photon Excited Fluorescence of Zinc（Ⅱ）,Cadmium（Ⅱ）Complexes Containing Phenothiazine Ligand

A new ligand,10-ethylphenothiazinyl-3-yl-methylene thiosemicarbazon(HL) and its complexes ML2 (M=Zn^2 ,Cd^2 ),which exhibit intensive two-photon excited (TPE) fluoresce at 800 nm laser pulses in femtosecond regime,were synthesized and characterized.The measured power dependence of the fluorescence signals provided direct evidence for TPE.All of them exhibited a large two-photon absorptive cross section and ,more importantly from the application point of view,high photochemical/photothermal stability.     

A new branched phenanthroline derivative ligand: synthesis, solution chemistry, and crystal structures of copper(II) and zinc(II) complexes

The synthesis and characterization of the new ligand 2,9-bis[N,N-bis(2-aminoethyl)aminomethyl]-1,10-phenanthroline (L) are reported. L contains two diethylenetriamine units connected on the central nitrogen atom by a 1,10-phenanthroline group forming a symmetrical branched ligand. The basicity and binding properties of L toward Cu(II) and Zn(II) in aqueous solution were determined by means of potentiometric, UV-vis, fluorescence, and 1H and 13C NMR techniques. L behaves as pentaprotic base under the experimental conditions used; from HL+ to H4L4+ species it is the secondary amine functions that are protonated while in the H5L5+ species also the phenanthroline is involved in protonation. L does not show fluorescence properties in the range of pH (0-14) investigated. It forms both mono- and dinuclear stable species where the phenanthroline is directly involved with both nitrogens in the coordination of the first metal which is coordinated in a pentacoordination environment also by one dien unit. The other dien unit undergoes easy protonation in the mononuclear complex while it binds the second metal in the dinuclear species. For this reason, L, in providing two different binding areas for metal coordination, behaves as an unsymmetrical compartmental ligand; one area is formed by one dien unit and by the phenanthroline, and the other by the remaining dien unit. This produces unsymmetrical metal complexes both for the mono- and dinuclear species; however, the role of the binding areas is fast exchanging in aqueous solution, at least on the NMR time scale. Solution studies and the three crystal structures of the [Zn(H2L)]4+, [[Cu(H2L)](ClO4)]3+, and [[Cu2LCl2](ClO4)]+ species highlight the unsymmetrical compartmental behavior of L as well as the host properties of the complexes in adding exogenous ligands such as hydroxide, pherchlorate, and chloride anions.     

A nanoscale slipped sandwich of Tb(10)-stabilization of a benzaldehyde methyl hemiacetyl

A nanoscale slipped sandwich of Tb(10) is formed from the reaction of 5-bromo-3-methoxysalicylaldehyde (HL) with TbCl(3)x6H(2)O and Zn(OAc)(2)x2H(2)O. The compound also features an unusual example of a coordinated methylhemiacetal which is derived from HL.     

N-(8-对氨基苯磺酰)胺基喹啉的合成及其荧光性质的研究

合成了一种Zn2+荧光探针N-(8-对氨基苯磺酰)胺基喹啉(HQAS),探讨了HQAS与Zn2+的键合比和配位模式,以及不同pH,其它金属离子对Zn2+检测的影响.研究结果显示:该探针与Zn2+形成配合物,使其荧光增强,键合比为2:1,pH 7.2时荧光强度增大9.4倍.大多数金属离子几乎不干扰Zn2+的检测,Cu2+...     

A Two-dimensional Metallic Oxide Constructed from Molybdenum Clusters and Zn（Ⅱ）-[3-（2-pyridyl）pyrazole] Cationic Coordination Components

A new polyoxomolybdate compound [Zn(HL)2(Mo8O26)(4,4'-Bipy)]·(4,4'-Bipy) (HL = 3-(2-pyridyl)pyrazole, 4,4'-Bipy = 4,4'-bipyridine) 1 has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, elemental analyses, TG and IR spectroscopy. The compound crystallizes in monoclinic, space group C2/c with a = 18.060(4), b = 13.870(3), c = 19.360(4) , β = 93.50(3)°, V = 4840.5(17) 3, C36H30Mo8N10O26Zn, Mr = 1851.59, Dc = 2.541 g/cm3, μ(MoKα) = 2.589 mm·1, F(000) = 3560, Z = 4, the final R = 0.0328 and wR = 0.0870 for 4005 observed reflections (I > 2σ(I)). X-ray diffraction analyses reveal that compound 1 is constructed from Mo8O264-units linked by Zn(HL)22+ and 4,4'-Bipy. Mo8O264-is connected by Zn(HL)22+ via terminal oxygen atoms along the [010] axis forming chains, which are further linked by 4,4'-Bipy along the [001] axis forming a two-dimensional network structure.     

Formation of Zinc(II) and Cadmium(II) Complexes with Pyridine Oxime Ligands in Aqueous Solution

Complex formation equilibria involving pyridine-2-carboxaldehyde oxime (1), 1-(2-pyridinyl)ethanone oxime (2) and 6-methylpyridine-2-carboxaldehyde oxime (3), HL, with zinc(II) and cadmium(II) ions were studied in aqueous 0.1 M NaCl solution at 25° C by potentiometric titrations with a glass electrode. Experimental data were analysed with the least-squares computer program SUPERQUAD to determine the complexes formed and their stability constants. With Ligands 1 and 2 the sets of complexes for Zn(II) and Cd(II) are essentially the same, mono- and dinuclear oxime complexes and their deprotonated/hydrolysed products H_pM_q(HL)^2q+p _r. Owing to the steric requirements of the 6-methyl group, sets of complexes formed with 3 are distinctly different. For zinc(II), only dinuclear oximato species H_pZn₂(HL)^4q+p ₂ ( p = ? 2, ? 3, ? 4) are found, while for the larger cadmium(II) ion mononuclear oximato species CdL⁺ and CdL₂ are detected in addition to the dinuclear complex H_pCd₂(HL)^4q+p ₂ ( p = ? 3).     

Radical pathway in catecholase activity with zinc-based model complexes of compartmental ligands

Four dinuclear and three mononuclear Zn(II) complexes of phenol-based compartmental ligands (HL(1)-HL(7)) have been synthesized with the aim to investigate the viability of a radical pathway in catecholase activity. The complexes have been characterized by routine physicochemical studies as well as X-ray single-crystal structure analysis: [Zn(2)(H(2)L(1))(OH)(H(2)O)(NO(3))](NO(3))(3) (1), [Zn(2)L(2)Cl(3)] (2), [Zn(2)L(3)Cl(3)] (3), [Zn(2)(L(4))(2)(CH(3)COO)(2)] (4), [Zn(HL(5))Cl(2)] (5), [Zn(HL(6))Cl(2)] (6), and [Zn(HL(7))Cl(2)] (7) [L(1)-L(3) and L(5)-L(7) = 2,6-bis(R-iminomethyl)-4-methylphenolato, where R= N-ethylpiperazine for L(1), R = 2-(N-ethyl)pyridine for L(2), R = N-ethylpyrrolidine for L(3), R = N-methylbenzene for L(5), R = 2-(N-methyl)thiophene for L(6), R = 2-(N-ethyl)thiophene for L(7), and L(4) = 2-formyl-4-methyl-6-N-methylbenzene-iminomethyl-phenolato]. Catecholase-like activity of the complexes has been investigated in methanol medium by UV-vis spectrophotometric study using 3,5-di-tert-butylcatechol as model substrate. All complexes are highly active in catalyzing the aerobic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ). Conversion of 3,5-DTBC to 3,5-DTBQ catalyzed by mononuclear complexes (5-7) is observed to proceed via formation of two enzyme-substrate adducts, ES1 and ES2, detected spectroscopically, a finding reported for the first time in any Zn(II) complex catalyzed oxidation of catechol. On the other hand, no such enzyme-substrate adduct has been identified, and 3,5-DTBC to 3,5-DTBQ conversion is observed to be catalyzed by the dinuclear complexes (1-4) very smoothly. EPR experiment suggests generation of radicals in the presence of 3,5-DTBC, and that finding has been strengthened by cyclic voltammetric study. Thus, it may be proposed that the radical pathway is probably responsible for conversion of 3,5-DTBC to 3,5-DTBQ promoted by complexes of redox-innocent Zn(II) ion. The ligand-centered radical generation has further been verified by density functional theory calculation.