CuII Ions Research Articles

Series of coordination polymers with multifunctional properties for nitroaromatic compounds and CuII sensing

Pollutants caused by heavy metals and nitroaromatics (NACs) have become a serious environmental issue. Herein, we designed and synthesized series of coordination polymers (CPs) as a universal sensing platform that demonstrated a great potential for detecting and removing heavy metals and NACs. The results showed the different structural motifs can be controlled by N-donor ligands. Without using bridging N-containing ligand, five non-interpenetrating 1D chain (1 and 7) and 2D layer (4–6) were constructed. In the presence of 4,4′-bipy ligand, two 3D 4-fold interpenetrated frameworks with pcu topology and fsg topology for 2 and 3 were produced, respectively. 1,2,4,5 not only display sensitivity for nitroaromatics (NACs) and small organic solvents, but also have impressive removal capabilities of Cu2+ ion. Sensing studies of samples to detect nitro-aromatic compounds reveal highly detection of 2,4,6-Trinitrophenol (TNP) with a low limit of detection (LOD: 1.16 ​ppm for 1, 2.59 ​ppm for 2, 3.36 ​ppm for 4 and 2.30 ​ppm for 5). The coefficient of correlations between (I0–I)/I0 and the content of Cu2+ ions was got in the detection limit range of 1.04–2.57 ​ppm for 1, 2, 4, 5. The immobilized CuII ions could be easily removed by EDTA without structural decomposition.

Binuclear isophthaloylbis(N,N-diphenylthioureate) transition metal complexes: Synthesis, spectroscopic, thermal and structural characterization

The isophthaloylbis(N,N-diphenylthiourea) molecule (H2L ligand) reacts with CuI, CuII, MnIII, FeII, FeIII and CoII ions to form binuclear complexes with formula [M2(L-O,S)2] (M = CuII (1), NiII (2)) or [M2(L-O,S)3] (M = FeIII (4), CoIII (5)). In presence of dimethyl sulfoxide, [Mn2(L-O,S)2(dmso)2] (3) was successfully obtained and represents the first manganese complex with any thiourea derivative ligand. The ligand and the complexes were characterized by spectroscopic techniques and elemental analysis. Complexes 1, 3, 4 and 5 were structurally analyzed by single crystal X-ray diffraction data, confirming the O,S chelating coordination mode. The stoichiometries were confirmed by thermal analysis with formation of the corresponding metal oxides. The set of the performed analysis corroborated that some metal ions undergo oxidation or reduction to form stable 2:2 or 2:3 metal to ligand stoichiometric complexes with H2L.

Mercaptothiacalixarenes Steer 24 Copper(I) Centers to form a Hollow‐Sphere Structure Featuring Cu2S2 Motifs with Exceptionally Short Cu⋅⋅⋅Cu Distances

AbstractTetramercaptotetrathiacalix[4]arene (LH4) can be used as a coordination platform to bind four CuI ions at the thiolate and thioether S atoms. Donor ligands such as phosphanes can stabilize the resulting [LCu4] units, which then remain monomeric ([(Ph3PCu)4L]). In the absence of donor ligands, they aggregate, providing a hexamer ([LCu4]6) in high yields, with a hollow‐sphere structure formed by an unprecedented Cu24S48 cage that is surrounded by the organic framework of the calixarene chalices. Preliminary NMR experiments with regard to the host‐guest chemistry in solution showed that the compound represents a polytopic host for acetonitrile and methane.

Mercaptothiacalixarenes Steer 24 Copper(I) Centers to form a Hollow-Sphere Structure Featuring Cu2 S2 Motifs with Exceptionally Short Cu⋅⋅⋅Cu Distances.

Tetramercaptotetrathiacalix[4]arene (LH4) can be used as a coordination platform to bind four CuI ions at the thiolate and thioether S atoms. Donor ligands such as phosphanes can stabilize the resulting [LCu4] units, which then remain monomeric ([(Ph3PCu)4L]). In the absence of donor ligands, they aggregate, providing a hexamer ([LCu4]6) in high yields, with a hollow‐sphere structure formed by an unprecedented Cu24S48 cage that is surrounded by the organic framework of the calixarene chalices. Preliminary NMR experiments with regard to the host‐guest chemistry in solution showed that the compound represents a polytopic host for acetonitrile and methane.

Construction of Mono-, Bi- and Trinuclear Clusters to Modify Wells–Dawson Anions through Using Different Transition Metals and Flexible Bis(Pyrazole) Ligands

Three new Wells–Dawson compounds, namely [CoII(edpz)(H2bdpm)3][(H4P2W18O62)] (1), [CdII2(mpz)(H2bhpe)2.5(H2O)(H2P2W18O62)] · (ppz) · 6H2O (2) and [CuII3(ppz)(H2bhpe)2(P2W18O62)(H2O)3] · 2H2O (3) (edpz = 4-ethyl-3,5-dimethyl-1H-pyrazole, H2bdpm = 1,1'-bis(3,5-dimethyl-1H-pyrazolate)methane, mpz = 4-methyl-4H-pyrazole, H2bhpe = 1,2-bis(1H-pyrazolyl)ethane, ppz = 4-propyl-1H-pyrazole), have been hydrothermally synthesized by using flexible bis(pyrazole) ligands and characterized by single-crystal X-ray diffraction analysis, IR spectra and elemental analyses. In compound 1, there are two discrete subunits: a mono-nuclear [Co(edpz)(H2bdpm)3]2+ cluster and a Wells–Dawson anion. The hydrogen bonding interactions between these subunits induce a 2D supramolecular structure. In compound 2, two Cd ions are fused by one mpz and five H2bhpe ligands to construct a bi-nuclear Cd cluster. The [P2W18O62]6– anions link bi-nuclear Cd clusters to form a 3D framework. In compound 3, four H2bhpe ligands fuse three CuII ions to construct a planar tri-nuclear cluster, with one ppz ligand vertical with this tri-nuclear cluster. The [P2W18O62]6– anions connect adjacent tri-nuclear clusters to form a 3D framework. Moreover, we also investigated the electrochemical and photocatalytic properties of compounds 1−3.

Improved Photostability of a CuI Complex by Macrocyclization of the Phenanthroline Ligands.

The development of molecular materials for conversion of solar energy into electricity and fuels is one of the most active research areas, in which the light absorber plays a key role. While copper(I)‐bis(diimine) complexes [CuI(L)2]+ are considered as potent substitutes for [RuII(bpy)3]2+, they exhibit limited structural integrity as ligand loss by substitution can occur. In this article, we present a new concept to stabilize copper bis(phenanthroline) complexes by macrocyclization of the ligands which are preorganized around the CuI ion. Using oxidative Hay acetylene homocoupling conditions, several CuI complexes with varying bridge length were prepared and analyzed. Absorption and emission properties are assessed; rewardingly, the envisioned approach was successful since the flexible 1,4‐butadiyl‐bridged complex does show enhanced MLCT absorption and emission, as well as improved photostability upon irradiation with a blue LED compared to a reference complex.

Transition-Metal-Functionalized DNA Double-Crossover Tiles: Enhanced Stability and Chirality Transfer to Metal Centers.

The double crossover junction (DX) is a fundamental building block for generating complex and varied structures from DNA. However, its implementation in functional devices is limited to the inherent properties of DNA itself. Here, we developed design strategies to generate the first metal-DX DNA tiles (DXM ) by site-specifically functionalizing the tile crossovers with tetrahedral binding pockets that coordinate CuI . These DX junctions bind two CuI ions independently at distinct sites, display greater thermal stability than native DX tiles upon metalation, and melt in a cooperative fashion. In addition, the right-handed helical chirality of DNA is transferred to the metal centers. Our tiles display high metal ion selectivity, such that CuII is spontaneously reduced to CuI in situ. By modifying our design over three generations of tiles, we elucidated the thermodynamic and geometric requirements for the successful assembly of DXM tiles, which have direct applicability in developing robust, stable DNA-based materials with electroactive, photoactive, and catalytic properties.

Transition‐Metal‐Functionalized DNA Double‐Crossover Tiles: Enhanced Stability and Chirality Transfer to Metal Centers

AbstractThe double crossover junction (DX) is a fundamental building block for generating complex and varied structures from DNA. However, its implementation in functional devices is limited to the inherent properties of DNA itself. Here, we developed design strategies to generate the first metal–DX DNA tiles (DXM) by site‐specifically functionalizing the tile crossovers with tetrahedral binding pockets that coordinate CuI. These DX junctions bind two CuI ions independently at distinct sites, display greater thermal stability than native DX tiles upon metalation, and melt in a cooperative fashion. In addition, the right‐handed helical chirality of DNA is transferred to the metal centers. Our tiles display high metal ion selectivity, such that CuII is spontaneously reduced to CuI in situ. By modifying our design over three generations of tiles, we elucidated the thermodynamic and geometric requirements for the successful assembly of DXM tiles, which have direct applicability in developing robust, stable DNA‐based materials with electroactive, photoactive, and catalytic properties.

NH2-UiO-66(Zr) with fast electron transfer routes for breaking down nitric oxide via photocatalysis

MOFs-based photocatalysts always suffer from poor performance owing to its slow charge transfer. Herein, transient metal Cu (CuI/II) species were introduced to NH2-UiO-66(Zr) (Cu-NU0) via in-situ partial reduction of CuII ions to CuI. A ligand to linker metal charge transfer (LLMCT) pathway in MOFs was constructed for accelerating the photogenerated electrons transfer from organic linkers to Cu species, greatly enhanced increasing both the carrier density value and the separation efficiency of photogenerated carriers. A longer photogenerated charge lifetime (78.2 ps) was obtained and about 4 times higher than that of Cu-NU0. More photogenerated electrons in the Cu coordinated MOFs (Cu-NU7) were transferred to the outside surface of the MOFs, producing O2− for the photocatalytic oxidation of low-concentration (550 ppb) of NO indoor flow gas. An 88 % removal rate of NO under visible-light irradiation (λ > 420 nm) was obtained and well maintained up to 24 h with excellent durability.

Crystal structure, spectroscopic characterization and Hirshfeld surface analysis of aqua-dichlorido-{N-[(pyridin-2-yl)methyl-idene]aniline}copper(II) monohydrate.

The reaction of N-phenyl-1-(pyridin-2-yl)methanimine with copper chloride dihydrate produced the title neutral complex, [CuCl2(C12H10N2)(H2O)]·H2O. The CuII ion is five-coordinated in a distorted square-pyramidal geometry, in which the two N atoms of the bidentate Schiff base, as well as one chloro and a water mol-ecule, form the irregular base of the pyramidal structure. Meanwhile, the apical chloride ligand inter-acts through a strong hydrogen bond with a water mol-ecule of crystallization. In the crystal, mol-ecules are arranged in pairs, forming a stacking of symmetrical cyclic dimers that inter-act in turn through strong hydrogen bonds between the chloride ligands and both the coordinated and the crystallization water mol-ecules. The mol-ecular and electronic structures of the complex were also studied in detail using EPR (continuous and pulsed), FT-IR and Raman spectroscopy, as well as magnetization measurements. Likewise, Hirshfeld surface analysis was used to investigate the inter-molecular inter-actions in the crystal packing.

Heterobimetallic complexes from 0D clusters to 3D networks based on various polycyanometallates and [Cu(dmpn)2]2+ (dmpn = 2,2-dimethyl-1,3-diaminopropane): synthesis, crystal structures and magnetic properties

Six new cyanide-bridged complexes (0–3D) have been assembled by employing one copper compound and six cyano precursors. Investigation of the magnetic properties revealed the ferro- or antiferromagnetic coupling between FeIII/CrI ion and CuII ion.

Combined Analytical Py-GC/MS, SEM, FTIR and 13C NMR for Investigating the Removal of Trace Metals from Aqueous Solutions by Biochar

In this study, the efficiency of biochar (BC) produced from sugarcane bagasse at different pyrolysis temperatures (300, 400, 500 and 600 oC) for simultaneous removal of CdII, PbII, CuII, CrIII, NiII and ZnII ions from aqueous solutions was assessed. All BC were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), 13C nuclear magnetic resonance (13C NMR) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The effects of pyrolysis temperature, initial adsorbate concentration and adsorbent dosage on adorption capacity of BC were examined through batch experiments. The BC efficiency was also evaluated after a desorption cycle. The maximal adsorptions (CdII: 51.50%, CrIII: 74.35%, CuII: 91.18%, NiII: 47.05%, PbII: 96.17% and ZnII: 40.50%) were observed for BC produced at 500 oC, probably because of its higher porosity and presence of functional groups detected by SEM and FTIR. The maximum adsorption capacity for CdII, CrIII, CuII, NiII and ZnII (ions fitted to Langmuir model) were 175, 303, 455, 156 and 128 µg g-1, respectively. The predominance of phenolic groups observed in Py-GC-MS data may explain the high percentage of multi-element removal. Experimental data were best fitted to pseudo-second order, Sips and Freundlich models. The BC presented good removal results after a desorption cycle.

A novel antibacterial active [CuII—GdIII] complex constructed from an asymmetric salamo-based ligand: synthesis and structural characterization

In the present study, we describe a reaction of Cu(OAc)2·H2O and Gd(NO3)3·6H2O with equimolar amounts of the asymmetric salamo-type ligand 6-methoxy-6'-ethoxy-2,2'-[ethylenedioxybis(azinomethyl)]diphenol (H2L) generated by Schiff base condensation of 2-[O-(1-ethyloxyamide)]oxime-3-methoxy-phenol with 3-ethoxysalicylaldehyde to obtain a novel 3d—4f hetero-polynuclear complex [{Cu(L)Gd(NO3)3}2][Cu(L)Gd(NO3)3]2. The complex is fully characterized by X-ray diffraction (XRD), elemental analyses, FTIR and UV-Vis spectra. The phase purity is clearly confirmed by powder XRD. In the [CuII—GdIII] complex, the coordination environments of CuII ions are different, but the apical coordination atoms to the GdIII ions are nearly identical. The antibacterial and fluorescent properties of the H2L ligand and the [CuII—GdIII] complex are also investigated. Supramolecular interactions are studied in detail.

Crystal structure and Hirshfeld surface analysis of a copper(II) complex with ethyl-enedi-amine and non-coordinated benzoate.

In the title compound, di-aqua-bis-(ethyl-enedi-amine-κ2 N,N')copper(II) bis-(2-nitro-benzoate), [Cu(C2H8N2)2(H2O)2](C7H4NO4)2, two di-aqua-bis-(ethyl-enedi-amine)-copper(II) cations and four nitro-benzoate anions are present in the asymmetric unit. All four anions are 'whole-mol-ecule' disordered over two sets of sites. The major components have refined occupancies of 0.572 (13), 0.591 (9), 0.601 (9) and 0.794 (10). The CuII ions exhibit slightly distorted octa-hedral geometries. In the crystal, cations and anions are connected to each other via N-H⋯O and O-H⋯O hydrogen bonds, forming a two-dimensional network parallel to (200). The inter-molecular contacts in the crystal were further analysed using Hirshfeld surface analysis, which indicates that the most significant contacts are O⋯H/H⋯O (42.9%), followed by H⋯H (35.7%), C⋯H/H⋯C (14.2%), C⋯C (2.9%), C⋯O/O⋯C (2.2%), N⋯H/H⋯N (0.9%) and N⋯O/O⋯N (0.3%).

A Highly Selective Colorimetric Sensor for Cysteine Detection

Introducing a hybrid xanthene as a fluorophore, an ‘ensemble’-based fluorescent sensor (E)-2-(6-(diethylamino)-2-((2-hydroxyphenylimino)methyl)-3-oxo-3H-xanthen-9-yl)benzoic acid (a) was designed and synthesised for detection of cysteine. Cysteine can release CuII ion from the non-fluorescent a-CuII complex. Then hydrolytic cleavage of Schiff base a produces a pink fluorescent compound 2-(6-(diethylamino)-2-formyl-3-oxo-3H-xanthen-9-yl)benzoic acid (2). We call this process a fluorescence off-on change. An obvious color change from purple a to pink 2 can be easily observed by the naked-eye. The calibration curve showed that the fluorescence intensity at 560 nm linearly increased over the cysteine concentration range of 0.379-100 µmol L-1 with a limit of detection of 0.379 µmol L-1. Sensor a-CuII displayed excellent selectivity for cysteine, even homocysteine and glutathione did not show influence. The sensor was also used for detecting cysteine in human breast adenocarcinoma cells, which illustrates the practical value. Overall, the sensor appears to be useful for rapid, convenient and selective cysteine detection in living tissues.

Unprecedented Dinuclear CuII N,O-Donor Complex: Synthesis, Structural Characterization, Fluorescence Property, and Hirshfeld Analysis

An unprecedented dinuclear CuII complex, [Cu2(L2)2], derived from a salamo-like chelating ligand H2L2, was produced by the cleavage of a newly synthesized, half-salamo-like ligand HL1 (2-[O-(1-ethyloxyamide)]oxime-3,5-dichloro-phenol). This was synthesized and characterized by elemental analyses, IR, UV–Vis and fluorescent spectra, single crystal X-ray diffraction analysis, and Hirshfeld surface analysis. X-ray crystallographic analysis indicated that the two CuII (Cu1 and Cu2) ions bore different (N2O3 and N2O2) coordination environments, the penta-coordinated Cu1 ion possessed a slightly twisted tetragonal pyramid geometry with the τ value τ = 0.004, and the tetra-coordinated Cu2 ion showed a slightly twisted square planar geometry. Interestingly, one oxime oxygen atom participated in the coordination reported previously. Moreover, an infinite two-dimensional layered supramolecular network was formed. Compared with HL1, the CuII complex possessed the characteristic of fluorescence quenching.

Enzymatic Synthesis of Cu(II)-Responsive Deoxyribozymes through Polymerase Incorporation of Artificial Ligand-Type Nucleotides.

Metal-mediated artificial base pairs, consisting of ligand-type nucleotides and a bridging metal ion, have shown promise as functional units to develop stimuli-responsive DNA materials. Although a variety of metal-mediated base pairs have been constructed with artificial ligand-type nucleotides and various metal ions, the application of such metal-mediated base pairs has been relatively poorly explored mainly due to the cumbersome chemical synthesis of artificial DNA strands. Herein we report a facile enzymatic method to synthesize DNA strands containing a ligand-type hydroxypyridone (H) nucleotide, which forms a CuII-mediated base pair (H-CuII-H). A two-step primer extension reaction using two commercially available polymerases enabled the incorporation of a H nucleotide at an internal position of oligonucleotides. The polymerase synthesis was subsequently applied to the development of metal-responsive deoxyribozymes (DNAzymes), whose catalytic activity was regulated by the formation of a single H-CuII-H base pair in its stem region. The DNAzyme activity was reversibly switched by the alternate addition and the removal of CuII ions. Furthermore, metal-dependent orthogonal activation of a CuII-responsive H-DNAzyme and a HgII-responsive T-DNAzyme was experimentally demonstrated by utilizing both H-CuII-H as well as widely explored T-HgII-T base pairs. These results suggest that the incorporation of H-CuII-H base pairs would facilitate the rational design of metal-responsive functional DNAs. Accordingly, the facile enzymatic synthesis of artificial ligand-bearing DNAs developed in this study would significantly expand the toolbox of DNA-based supramolecular chemistry and DNA nanotechnology.

A new 1,8-naphthalimide-based fluorescent “turn-off” sensor for detecting Cu2+ and sensing mechanisms

In this article, a new “turn-off” fluorescent sensor N- n-butyl-4-{2-[(ethylimino)methyl]phenol}-1,8-naphthalimide (HL) for CuII ions is synthesized, which contains a 1,8-naphthalimide moiety as the fluorophore and a Schiff base as the recognition group. As expected, it exhibits high selectivity and sensitivity for detecting CuII ions over other common metal ions in acetonitrile–2-(4-(2-hydroxyethyl)-1-piperazinyl)-ethanesulfonic acid (HEPES) (1:1 v/v, pH = 7.4) solution. In addition, the fluorescence intensity for HL showed a good linearity with the concentration of CuII ions in the range of 0.5–5.0 μM. The 2:1 binding stoichiometry between HL and CuII ions was established on the basis of combined fluorescence titrations, a Job’s plot, single-crystal X-ray analysis and mass spectrometry. The quenching response of HL toward CuII ions is attributed to the reverse photoinduced electron transfer mechanism. The proposed sensor HL is preliminarily applied to quantify CuII ions in water samples from the Yellow River and tap water.

Syntheses, crystal structures and magnetic properties of redox active cyanide-bridged trinuclear Ru-M2 (M = Co, Ni, Cu) complexes

Three redox active cyanide-bridged trinuclear complexes trans-(DMAP)4Ru(μ-CN)2- [M(PY5Me2)]2[PF6]4 (M = Co (1), Ni (2), Cu (3)) {DMAP = 4-dimethylamino-pyridine, PY5Me2 = 2,6-bis(1,1-bis(2-pyridyl)ethyl)pyridine} were designed, synthesized and fully characterized by single-crystal X-ray diffraction, elemental analysis, IR spectrum, cyclic voltammetry and magnetic measurement. Due to the Jahn-Teller effect of CuII ion, the structure of compound 3 shows peculiar disordered configuration. Cyclic voltammograms show that compounds 1 and 2 possess redox-active Co and Ni centers except for the Ru center. Magnetic measurements show compound 1 behaves as paramagnetism with strong magnetic anisotropy of CoII ion and compound 2 has a very weak anti-ferromagnetic coupling constant, but compound 3 is only simple paramagnetism.

Crystal structure of catena-poly[[[(2-eth-oxy-pyrazine-κN)copper(I)]-di-μ2-cyanido] [copper(I)-μ2-cyanido]

In the asymmetric unit of the title coordination compound, {[Cu(CN)(C4H3OC2H5N2)][Cu(CN)]} n , there are two Cu atoms with different coordination environments. One CuI ion is coordinated in a triangular coordination geometry by the N atom of the 2-eth-oxy-pyrazine mol-ecule and by two bridging cyanide ligands, equally disordered over two sites exchanging C and N atoms, thus forming polymeric chains parallel to the c axis. The other Cu atom is connected to two bridging cyanide groups disordered over two sites with an occupancy of 0.5 for each C and N atom, and forming an almost linear polymeric chain parallel to the b axis. In the crystal, the two types of chain, which are orthogonal to each other, are connected by cuprophilic Cu⋯Cu inter-actions [2.7958 (13) Å], forming two-dimensional metal-organic coordination layers parallel to the bc plane. The coordination framework is further stabilized by weak long-range (electrostatic type) C-H⋯π inter-actions between cyano groups and 2-eth-oxy-pyrazine rings.