"Turn-on" fluorescent sensor for Hg2+ via displacement approach

A new Cu2+ compound Cu- NB, (where H2 NB is bis(2-hydroxyl-naphthalene-carboxaldehyde) benzil dihydrazone) was synthesized as a highly selective fluorescence chemosensor for the detection of Hg2+ in aqueous media through a displacement "turn-on" signaling strategy. Whereas the coordination of Cu2+ resulted in a considerable quenching of the typical luminescence of the naphthol rings in Cu-NB, the addition of Hg2+ ion led to a dramatic increase in the emission intensity of Cu-NB at about 530 nm (excitation at 430 nm). The competitive fluorescent experiments showed that alkali, alkaline earth metal ions, the group 12 metals Zn2+, Cd2+, the first-row transition-metal ions such as Mn2+, Fe2+, Co2+, and Ni2+, as well as Pb2+ could not inhibit the Hg2+-binding fluorescent enhancement. It is postulated that the existence of Cu2+ in the luminescent probe Cu-NB could turn away the interferences of other metal cations from Hg2+ detection. The optical responses of the free ligand upon addition of Cu2+ ion, and of the Hg-H2NB compound upon the addition of Cu2+ were also investigated for comparisons.     

Discovery of a sensitive Cu(II)-cyanide "off-on" sensor based on new C-glycosyl triazolyl bis-amino acid scaffold

A new functional glycosyl peptidomimetic, featuring a C-glucosyl 1,4-dimethoxynaphthalene backbone in conjugation with two triazolyl phenylalanine moieties on its adjacent C3,4-positions, was readily synthesized via click chemistry. Primary optical measurements indicated that the fluorescence of the ester form of this probe (4) could be selectively quenched by Pb(2+). In contrast, the fluorescence intensity of its analog 5 with released carboxylic groups was uniquely diminished by Cu(2+) with remarkably enhanced sensitivity and selectivity. Moreover, subsequent addition of cyanide to the methanol solution of the resulting Cu(2+)-5 complex induced its fluorescence recovery with a nanomolar detection limit, which was two orders of magnitude smaller than the regulated concentration limit of CN(-) in drinking water. This suggests the promising applicability of C-glycosyl bis-triazolyl amino acid scaffold in the future design and exploration of sensitive "off-on" Cu(II)-cyanide chemosensors.     

Cu2+ colorimetric sensing and fluorescence enhancement and Hg2+ fluorescence diminution in "scorpionate"-like tetrathienyl-substituted boron-dipyrrins

Four novel tetrathienyl-substituted boron-dipyrrin-type (BODIPY-type) complexes, 3-(R')-4,4-di(R')-8-R-4-bora-3a,4a-diaza-s-indacene (4a, R = 2-T, R' = 2-T; 4b, R = 3-T, R' = 2-T; 5a, R = 2-T, R' = 3-T; 5b, R = 3-T, R' = 3-T; T = thienyl) have been prepared and fully characterized to explore patterns of stoichiometric Mn+ recognition in solution. Treatment of the respective parent BF2 dipyrrin with 2- or 3-thienyllithium gave the unexpected asymmetric tetrathienyl-substituted products in 8.5-35% yield. Compounds 4a and 4b bear a neutral "scorpionate"-like [SSS] tridentate binding pocket. Extensive NMR and UV-vis spectroscopic studies were performed on 4a-5b; 5a, 4b, and 5b were structurally characterized. The PhiF values for 4a-5b all decrease compared to the BF2-containing parent molecules (0.00058, 0.012, 0.00090, and 0.0051, respectively), with lambda(abs,max) values (epsilon, M(-1) cm(-1)) of 563 (44,000), 553 (29,000), 539 (33,000), and 531 (44,000) nm, respectively, and Stokes' shifts of 25-36 nm. Upon treatment with metal ion (Ca2+, Cs+, Mn2+, Co2+, Cu2+, Ag+, Zn2+, Cd2+, Hg2+, Pb2+) perchlorate salts, the solution of 4b undergoes rapid pink-to-clear switch-off behavior upon Cu2+ addition (10 microM scale) with smaller effects seen for 4a. Further, there were 2- to 19-fold Cu2+ fluorescence enhancements for these ligands. Cu2+- and Hg2+-L (L = 4a-5b) binding was modeled, and response patterns for Mn+-L 1:1 molar solutions upon Cu2+ addition were measured. Upon treatment with Hg2+, all ligand solutions show a significant fluorescence decrease accompanied by minor absorption increases. The UV-vis spectroscopic detection limit for Cu2+ and Hg2+ is approximately 270 ppb and approximately 1.7 ppm, respectively; the naked eye detection limit for Cu2+ with 4b (1.0 x 10(-5) M) is approximately 23 microM. DFT calculations gave HOMO-LUMO gaps of 478 (4a), 462 (4b), 448 (5a), and 442 nm (5b). Molecular orbital diagrams for 4a-5b revealed that the HOMO and LUMO electron density is distributed onto the 3-position-thienyl group and to a lesser degree the B(thienyl)2 moiety.     

Self-induced "electroclick" immobilization of a copper complex onto self-assembled monolayers on a gold electrode

We report the self-induced "electroclick" immobilization of the [Cu(II)(6-ethynyl-TMPA)(H(2)O)](2+) complex, by its simple electro-reduction, onto a mixed azidoundodecane-/decane-thiol modified gold electrode. The redox response of the grafted [Cu(II/I)(TMPA)] at the modified electrode is fully reversible indicating no Cu coordination change and a fast electron transfer.     

"Naked-eye" detection of histidine by regulation of Cu(II) coordination modes

The association of various alpha-amino acids with four new, coordinatively unsaturated metal complexes ([Cu(5)]2+, [Cu(6)]2+, [Cu(7)]2+, and [Zn(8)]2+) was examined. The receptors [Cu(5)]2+ and [Cu(7)]2+ were found to discriminate histidine (His) from other zwitterionic alpha-amino acids by means of indicator-displacement assays (IDAs) using 5(6)-carboxyfluorescein as an indicator in buffered methanol/water (3:1) solvent. The colorimetric detection of His was achieved by using this IDA method, which appears to owe its selectivity to a unique process involving disruption of the host complex to form a 2:1 His/Cu(II) complex rather than simple indicator displacement. The occurrence of distinct intermolecular coordination processes in response to the introduction of a different amino acid is observed. X-ray crystal structures of the host metal complexes were obtained and exhibit the adoption of a variety of coordination geometries about the metal center.     

Effect of Cu(II) on the electrochemically initiated reaction of thiols with<Emphasis Type="Italic"> N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diethyl-<Emphasis Type="Italic">p</Emphasis>-phenylenediamine: methodology for the indirect voltammetric determination of Cu(II)

The effect of Cu(II) on the determination of homocysteine via its electrochemically initiated reaction with N,N-diethyl-p-phenylenediamine is examined. The presence of copper inhibited the detection process for homocysteine owing to a complexation reaction occurring. This provided an indirect route for the sensitive and selective determination of Cu(II), which produced a linear response over the range from 2.5 to 500 M and a limit of detection of 2.5 M. The detection pathway was examined in the presence of metallic and inorganic ions, with negligible interference observed.     

Solvent controlled sugar-rhodamine fluorescence sensor for Cu(2+) detection

A "turn-on" fluorescence probe for Cu(2+) detection has been reported according to a Cu(2+) triggered spirolactam ring-opening reaction. The probe is a double-responsive fluorescent and colorimetric Cu(2+)-specific sensor in aqueous solution containing 20% of acetonitrile with high selectivity and excellent sensitivity (limit of detection is 12 μg L(-1)). Furthermore, the significant color changes visible to the naked eye at the concentration of 3 μM (ca. 0.20 mg L(-1)) are about ten times lower than the WHO (World Health Organization) recommended level (2.0 mg L(-1)) for Cu(2+) ions in drinking water.     

A fluorescence "turn-on" chemodosimeter for Cu2+ in aqueous solution based on the ion promoted oxidation

We developed a novel method for Cu(2+) detection based on the ion promoted oxidation reaction. Chemodosimeter L (weak fluorescence) can be oxidized into 3-benzothiazoly-7-N,N-diethylaminocoumarin (strong green fluorescence, coumarin 6) by Cu(2+) with high selectivity and sensitivity in HEPES (10 mM, pH = 7.4) buffer containing 50% (v/v) water-CH(3)CN solution.     

Octanuclear and nonanuclear supramolecular copper(II) complexes with linear "tritopic" ligands: structural and magnetic studies

The structures and magnetic properties of self-assembled copper(II) clusters and grids with the "tritopic" ligands 2poap (a), Cl2poap (b), m2poap (c), Cl2pomp (d), and 2pomp (e) are described [ligands derived by reaction of 4-R-2,6-pyridinedicarboxylic hydrazide (R = H, Cl, MeO) with 2-pyridinemethylimidate (a-c, respectively) or 2-acetylpyridine (d, R = Cl; e, R = H)]. Cl2poap and Cl2pomp self-assemble with Cu(NO(3))(2) to form octanuclear "pinwheel" cluster complexes [Cu(8)(Cl2poap-2H)(4)(NO(3))(8)].20H(2)O (1) and [Cu(8)(Cl2pomp-2H)(4)(NO(3))(8)].15H(2)O (2), built on a square [2 x 2] grid with four pendant copper arms, using "mild" reaction conditions. Similar reactions of Cl2pomp and 2pomp with Cu(ClO(4))(2) produce pinwheel clusters [Cu(8)(Cl2pomp-2H)(4)(H(2)O)(8)](ClO(4))(8).7H(2)O (3) and [Cu(8)(2pomp-2H)(4)(H(2)O)(8)](ClO(4))(8) (4), respectively. Heating a solution of 1 in MeOH/H(2)O produces a [3 x 3] nonanuclear square grid complex, [Cu(9)(Cl2poap-H)(3)(Cl2poap-2H)(3)](NO(3))(9).18H(2)O (5), which is also produced by direct reaction of the ligand and metal salt under similar conditions. Reaction of m2poap with Cu(NO(3))(2) produces only the [3 x 3] grid [Cu(9)(m2poap-H)(2)(m2poap-2H)(4)](NO(3))(8).17H(2)O (6) under similar conditions. Mixing the tritopic ligand 2poap with pyridine-2,6-dicarboxylic acid (picd) in the presence of Cu(NO(3))(2) produces a remarkable mixed ligand, nonanuclear grid complex [Cu(9)(2poap-H)(4)(picd-H)(3)(picd-2H)](NO(3))(9).9H(2)O (7), in which aromatic pi-stacking interactions are important in stabilizing the structure. Complexes 1-3 and 5-7 involve single oxygen atom (alkoxide) bridging connections between adjacent copper centers, while complex 4 has an unprecedented mixed micro-(N-N) and micro-O metal ion connectivity. Compound 1 (C(76)H(92)N(44)Cu(8)O(50)Cl(4)) crystallizes in the tetragonal system, space group I, with a = 21.645(1) A, c = 12.950(1) A, and Z = 2. Compound 2 (C(84)H(88)N(36)O(44)Cl(4)Cu(8)) crystallizes in the tetragonal system, space group I, with a = 21.2562(8) A, c = 12.7583(9) A, and Z = 2. Compound 4 (C(84)H(120)N(28)O(66)Cl(8)Cu(8)) crystallizes in the tetragonal system, space group I4(1)/a, with a = 20.7790(4) A, c = 32.561(1) A, and Z = 4. Compound 7(C(104)H(104)N(46)O(56)Cu(9)) crystallizes in the triclinic system, space group P, with a = 15.473(1) A, b = 19.869(2) A, c = 23.083(2) A, alpha = 88.890(2) degrees, beta = 81.511(2) degrees, gamma = 68.607(1) degrees, and Z = 2. All complexes exhibit dominant intramolecular ferromagnetic exchange coupling, resulting from an orthogonal bridging arrangement within each polynuclear structure.     

Nitrate-Bridged "Pseudo-Double-Propeller"-Type Lanthanide(III)-Copper(II) Heterometallic Clusters: Syntheses, Structures, and Magnetic Properties

Two discrete nitrate-bridged novel "pseudo-double-propeller"-shaped hexanuclear Cu/Ln clusters of the formula [Cu(4)Ln(2)L(4)L'(4)(NO(3))(2)(OH(2))(2)]·3NO(3)·4H(2)O [Ln = Dy, Gd; LH = o-vanilin; L'H = 2-(hydroxyethyl)pyridine] were synthesized and characterized. Single-crystal X-ray diffraction studies revealed the trimeric half-propeller-type Cu(2)/Ln core connected to other opposite-handed similar trimers by a bridging nitrate ligand. The Dy analogue, [Cu(4)Dy(2)L(4)L'(4)(NO(3))(2)(OH(2))(2)]·3NO(3)·4H(2)O, shows frequency-dependent out-of-phase alternating-current magnetic susceptibility, which indicates that this novel discrete [Cu(4)Dy(2)] heterometallic cluster may exhibit single-molecule-magnet behavior.     

Dendronized linear polymers via "click chemistry"

Dendronized linear polymers are prepared from dendritic azides and poly(vinylacetylene) using "click chemistry." The Cu(I)-catalyzed Huisgen [2 + 3] cycloaddition is quantitative up to the third generation.     

Highly sensitive and selective chemosensor for Cu2+ detection based on a N-propargyl rhodamine 6G-hydrazide derivative

A novel fluorescence "turn-on" probe for Cu2+ detection has been designed based on a Cu2+ triggered spirolactam ring-opening reaction.The synthetic probe is a double-responsive fluorescent and colorimetric Cu2+-specific sensor.In aqueous solution,it exhibits high selectivity and excellent sensitivity.With a significant color change visible to the naked eye at the concentration of 3 μM(ca.0.19 mg/L),about one magnitude lower than the WHO(World Health Organization) recommended level(2.0 mg/L) for Cu2+ ions in drinking water,the probe could be used to monitor Cu2+ ions in drinking water.     

Fluorescent zinc(II) complex exhibiting "on-off-on" switching toward Cu2+ and Ag+ ions

Binuclear zinc(II) and copper(II) complexes based on a new Schiff base ligand N,N'-bis(2-hydroxybenzilidene)-2,4,6-trimethylbenzene-1,3-diamine (H(2)L) have been synthesized. The ligand H(2)L and complexes under investigation have been characterized by elemental analyses, spectral (FT-IR, (1)H, (13)C NMR, ESI-MS, electronic absorption, emission), and electrochemical studies. The structures of H(2)L and complexes [{Zn(C(23)H(18)N(2)O(2))}(2)] (1) and [{Cu(C(23)H(18)N(2)O(2))}(2)]·H(2)O (2) have been determined crystallographically. Selective "On-Off-On" switching behavior of the fluorescent complex 1 has been studied. The fluorescence intensity of 1 quenches (turns-off) upon addition of Cu(2+), while enhances (turns-on) in the presence of Ag(+) ions. The mechanisms of "On-Off-On" signaling have been supported by (1)H NMR, ESI-MS, electronic absorption, and emission spectral studies. Job's plot analysis supported 1:1 and 1:2 stoichiometries for Cu(2+) and Ag(+) ions, respectively. Association and quenching constants have been estimated by the Benesi-Hildebrand method and Stern-Volmer plot. Moreover, 1 mimics a molecular keypad lock that follows correct chemical input order to give maximum output signal.     

Structural characterization of the intra- and inter-repeat copper binding modes within the N-terminal region of "prion related protein" (PrP-rel-2) of zebrafish

The unique biology of prion proteins (PrPs) allied with the public-health risks posed by prion zoonoses, such as various animal neurodegenerations, has focused much attention on the molecular basis of the controls cross-species and on the similarities between PrPs from different species. Given the common feature of PrPs as Cu(2+) binding proteins, it appears relevant to compare the impact of Cu(2+) on the stability constants and structures of "physiological" complexes. After having comprehensively delineated the interaction of Cu(2+) with mammalian and avian PrPs, the stabilities and molecular structures of species generated by Cu(2+) interacting with the irregular repeated domain derived from Danio rerio zebrafish PrP-rel-2 were investigated. Copper complexes with different zebrafish PrP-rel-2 fragments were analyzed by potentiometric and spectroscopic techniques. The data were interpreted as to provide evidence of all investigated repeat units selectively binding Cu(2+) via the His imidazole(s). The structural models obtained from paramagnetic NMR showed an intra- or inter-copper binding according to the number of the His in the sequence. In comparison to the mammalian and avian cases, the enzymatic function referred to SOD-like activity was shown to be rather faint in the fish PrPs cases.     

General method for synthesis of functionalized macrocycles and catenanes utilizing "click" chemistry

A new protocol for efficient and high yield synthesis of functionalized macrocycles and catenanes has been developed using "click" chemistry in combination with Sauvage's metal template route to interlocked structures. The procedure involves introduction of terminal alkyne moieties on a symmetrical 2,9-diaryl-1,10-phenanthroline (phen) building block, followed by double-"click" ring closure using aryl 3,5-diazides in the presence of CuI, sodium ascorbate, the base DBU and a sulfonated phenanthroline ligand in an oxygen-free 7:3:1 ethanol/water/toluene mixture at 70 degrees C. Utilizing acetal and vinyl substituted diazides, the corresponding bistriazole/phen macrocycles, characterized spectroscopically, were obtained in 65-70% yield. Formation of a binary Cu(I) complex of the diethynylphen ligand followed by reaction with aryl 3,5-diazides using a modified procedure affords the corresponding difunctionalized catenane in one step in 85-92% yield. The initial catenanes obtained after workup are Cu-free. Reintroduction of Cu(I) using Cu(CH3CN)4+PF6- gives the metallocatenanes, whose spectral properties are identical to those of related (phen)2Cu(I) catenanes reported by Sauvage and co-workers. This methodology provides ready access to functionalized interlocked structures, which can be used as intermediates in the preparation of a variety of new materials, including compounds of interest as artificial photosynthetic systems.     

高灵敏比色检测Cu~(2+)的反蛋白石结构光子晶体水凝胶膜

以丙烯酰胺(AM)和N-乙烯基咪唑(NVI)为双功能单体,借助"三明治"结构有效控制前驱液的填充,制备了可特异性识别Cu~(2+)的反蛋白石结构光子晶体水凝胶膜(PCHs).该PCHs具有相互贯通的三维有序大孔结构,可在Cu~(2+)缓冲溶液中快速响应,产生特征的布拉格(Bragg)衍射峰.随着Cu~(2+)浓度的增大(0~10-4mol/L),PCHs的Bragg衍射峰位移66 nm,并伴随着明显的颜色变化(由棕红色逐渐变为黄绿色).此外,PCHs在混合金属盐溶液中仍能实现对Cu~(2+)的特异性识别.PCHs对Cu~(2+)的特异识别性、快速响应及自表达的特点为Cu~(2+)现场快速检测提供了可能.     

铜离子催化DPKA关环反应及其潜在应用

铜离子催化的氧化关环有机反应，用于选择性荧光探测金属铜离子的存在。晶体结构和光谱分析表明,在DPKA的乙腈/水混合溶剂中，引入铜离子可以促使苯并三氮唑类荧光化合物(2)的形成，该反应可以使得溶液的荧光明显增强。而且在滴定溶液里，引入Cu²⁺螯合剂EDTA，并不能使得溶液的荧光减弱，表明荧光是由有机物2发射的。同时，其他金属离子的引入并不能产生荧光，而且干扰离子的存在也不能使得荧光光谱发生显著改变，表明DPKA可以高选择性的检测溶液中的铜离子。研究表明，荧光响应呈现2个线性关系，区间分别在0.64～3.2 mg·kg^-1和3.84～7.04 mg·kg^-1。     

"Click chemistry"en route to pseudo-starch

Rapid assembly of starch fragment analogues was achieved using "click chemistry". Specifically, two hexadecasaccharide mimics containing two parallel maltoheptaosyl chains linked via [1,2,3]-triazoles to a maltose core were synthesized using Cu(i)-catalyzed [3 + 2] dipolar cycloaddition of azido saccharides and 6,6'- and 4',6'-dipropargylated p-methoxyphenyl maltoside.     

First three-dimensional inorganic-organic hybrid material constructed from an "inverted Keggin" polyoxometalate and a copper(I)-organic complex

A new polyoxometalate (POM) based on a flexible bidentate ligand and "inverted Keggin" inorganic building block, namely, [Cu(8)L(8)[Mo(12)O(46)(AsPh)(4)](2)]·H(2)O (1), where L is 1,3-bis(1,2,4-triazol-1-yl)propane, has been synthesized under hydrothermal condition. In 1, the "inverted Keggin" [Mo(12)O(46)(AsPh)(4)](4-) building blocks are linked by the one-dimensional (1D) zigzag [Cu(I)(trans-L)](+) chains and [Cu(I)(4)(cis-L)(4)](4+) macrocycles to yield a three-dimensional (3D) framework. The compound 1 represents the first 3D "inverted Keggin" polyoxometalate modified by a transition-metal complex. Topologically, the 3D framework can be considered as an 8-connected net with a Schl?fli symbol of 4(22)·6(6). As far as we know, compound 1 is the highest-connected uninodal network topology presently known for POM-based materials. The compound was characterized by its IR spectrum, UV-vis spectrum, thermogravimetric analysis (TGA), and powder X-ray diffraction (XRD) patterns. Remarkably, compound 1 exhibits photocatalytic activity for dye degradation under visible light irradiation and shows good stability toward visible-light photocatalysis.     

A highly selective and sensitive inorganic/organic hybrid polymer fluorescence "turn-on" chemosensory system for iron cations

A polymer-based fluorescence "turn-on" chemosensor is demonstrated with high sensitivity and selectivity toward Fe2+ cations. This system is an inorganic/organic hybrid system in which Cu2+ is coordinated at the receptor site of a conjugated polymer sensor. The unique quenching behavior of the Cu2+ toward this conjugated polymer was used to lower the initial fluorescence intensity of the sensory system. This results in a highly sensitive and also selective sensory system toward Fe2+ as compared to other related divalent transition-metal cations in solution.