The first substituted macrocyclic ligand Py2N4S2 containing four naphthylmethylene pendant-armed groups: Synthesis and photophysical properties

The synthesis of a pendant donor emissive macrocyclic ligand Py₂N₄S₂ with up to four naphthylmethylene arms (L) has been achieved. Their derivative solid metal complexes (Co^2 +, Ni^2 +, Cu^2 +, Zn^2 +, Cd^2 +, Hg^2 + and Ag⁺) have been isolated and characterized. The photophysical properties of the free ligand L and their complexation behaviour have been investigated in solution. In dichloromethane, the free ligand presents two emission bands which are related to the monomer naphthalene emission and a red-shifted band attributable to ground state dimers (interaction between two naphthalene chromophores), which was further validated from time-resolved data, with bi-exponential decay with absence of dynamic components. UV–Vis spectroscopy has revealed a 2:1 binding stoichiometry for Co^2 +, Cu^2 +, Zn^2 +, Hg^2 + and Ag⁺.     

Structural characterization of ferromagnetic bridged-acetato and -dichlorido copper(II) complexes based on bicompartmental 4-t-butylphenol

The reaction of Cu(II) salts with 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-t-butylphenol (L^t-Bu-OH) afforded two bridged-phenoxido/hydroxido complexes. The dinuclear bridged acetate species [Cu₂(μ-L^t-Bu-O)(μ-CH₃COO)](PF₆)₂ (1) and the 1D polymeric doubly-bridged-chlorido {[Cu₂(μ-L^t-Bu-OH)(μ-Cl)₂](ClO₄)₂·4H₂O}_n (2). The two complexes were structurally characterized. Both complexes revealed ferromagnetic interactions; moderate in complex 1 (J = + 30.8 cm^− 1) and very weak (J = + 2.25 cm⁻¹) in 2.     

A new copper(II) selective fluorescence probe based on naphthalimide: Synthesis,mechanism and application in living cells

A new fluorescence probe L based on naphthalimide has been synthesized for selective and quantitative detection of Cu^2 + in CH₃CN:H₂O (4:1, v/v) solution. L exhibited a strong green fluorescence. Upon addition of 2 equiv. of Cu^2 +, the fluorescence emission shows a steady and smooth decrease until a plateau is reached with a 30-fold quenching of fluorescence intensity. In the presence of Cu^2 +, the absorbance peak of L maximum at 466 nm decreased, and a new absorption band at 600 nm appeared. Under the identical conditions, other physiological and environmental important metal ions induced negligible spectroscopic changes. The 1:2 stoichiometry binding mode of L with Cu^2 + was supported by the Benesi–Hildebrand analysis and ESI-MS spectra studies. The detection limit for Cu^2 + was estimated to be 64 ppb. Fluorescence microscopy experiments showed that L has practical application in living cells.     

Luminescence sensing of an unusual tetranodal 3-connected topology of Cu(I)-MOF

A new Cu(I)-based complex with chemical formulae [Cu₄Cl_0.24(CN)_3.76(L)] (1), (L = 1,3,5-tris(1-imidazolyl) benzene) has been synthesized and structurally characterized. Compound 1 shows an unusual tetranodal 3-connected topology and is self-penetrating – 0-membered shortest circuits. It shows that 1 can work as highly sensitive sensors to Cu^2 + and nitrobenzene (NB) explosive by luminescent quenching. This study shows that 1 could be a useful luminescent sensor for metal ions and organic small molecules.     

A new stable Cd(II)-framework for sensitive and selective detection of Cu2 + ions

A new water-stable 3D metal–organic framework (MOF), [Cd₂L₂]·NMP·MeOH (1, H₂L = 2-(3,5-dimethyl-1H-pyrazol-4-yl)-1,3-dioxoisoindoline-5,6-dicarboxylic acid, NMP = 1-methyl-2-pyrrolidinone) has been solvothermally synthesized and structurally characterized. 1 exhibits a 3D open-framework with a 2D metallic plane pillared by L^2 − fragments. Meanwhile, luminescent studies indicate that the luminescence intensity of 1 was strongly dependent on different metal ions. Most interestingly, 1 exhibited significantly quenching effect toward Cu^2 +, which implies that it may be used as a luminescent probe for the detection of Cu^2 +.     

Cyanide-bridged mixed-valence copper(II/I) coordination polymers: Unique 7-connected sev-type 3D network versus anionic 2D host network encapsulated with cationic complex

Reactions of CuCl₂, K₂[Ni(CN)₄]/K₃[Co(CN)₆], and 5-amino-1H-tetrazole led to cyanide-bridged mixed-valence Cu(II/I) complexes, [Cu(H₂O)₃Cu₃(CN)₅] (1) and [Cu(H₂O)₄][Cu₄(CN)₆] (2).The uncommon semi-closed {Cu₂(CN)₃} dimmers in 1 are bridged by μ₃-C,C,N cyanide ligands to afford rare 1D centipedal-like chain motifs, which are further bridged by μ₂-C,N and metalloligand “CN–Cu(4)–CN” to finish sophisticated zeolite-like 3-D structure. Topologically, 1 is the first example of uninodal 7-connected sev-like cyanide-bridged network. Compound 2 consists of two-dimensional honeycomb-related anionic layers [Cu₄(CN)₆]^2 −, within which the [Cu(H₂O)₄]^2 + cations are intercalated into alternate interlamellar space. Compound 1 shows antiferromagnetic couple arising from pure ground-state configuration of Cu(II) mediated by diamagnetic bridges –CN–Cu^I–CN −. The inclusion compound 2 shows blue photoluminescence originated from Cu(I) center to the unoccupied π* orbital of the cyanide ligand (MLCT) charge transfer.     

Molybdenum-oxygen anionic chain grafted by Cu-phen complex. Synthesis,crystal structure and properties

An unreported inorganic-organic hybrid compound [Cu(phen)(H₂O)₂(Mo₃O₁₀)] (1) was hydrothermally synthesized and characterized with elemental analysis, IR spectroscopy, thermal analysis, luminescent spectroscopy, magnetic measurement. The crystal structure was determined with X-ray single-crystal diffraction. Compound 1 has a 1-D chain structure constructed by {Mo₃O₁₀}^2 − units via edge-sharing and [Cu(phen)(H₂O)₂]^2 + fragments grafting the chain from two sides via the coordination of the terminal oxygen atom of the MoO₆ octahedra to Cu^2 + ion. The coordination of phen to Cu^2 + ion increases the molecular rigidity so that an emission peak at 500 nm was observed and assigned to the phosphorescent n–π* and π–π* transition from ligand-centered triple state. In compound 1 Cu(II) exhibits an antiferromagnetic exchange.     

Synthesis and mechanism study of a dimeric tetranuclear carbonate-bridged copper(II) complex resulting from CO2 fixation by controlling O2 concentration

A dimeric tetranuclear carbonate-bridged Cu(II) complex [Cu₄(DPA-ⁱBu)₄(μ₂-CO₃)₂(MeOH)₂]^4 + 1 was prepared in-situ through oxidation of Cu(I) species by controlling the concentration of O₂ in CO₂. Lower concentration of O₂ led to the formation of 1 after CO₂ fixation but higher would give product as bis-μ₂-hydroxo complex [Cu(DPA-ⁱBu)(OH)]₂^2 + 2, which was found to be an intermediate to generate trinuclear carbonated complex [Cu₃(DPA-ⁱBu)₃(μ₃-CO₃)(MeCN)₂(H₂O)]^4 + 3. The mechanism of this reaction was proposed and the nucleophilic attack of μ-peroxo Cu(II) species to CO₂ molecules was suggested to be responsible for the generation of 1.     

Highly selective recognition of mercury ions through the “naked-eye”

A new sensor 2-((E)-(3-(1H-imidazol-1-yl)propylimino)methyl)-5-(diethylamino)phenol (1) based on the combination of diethylaminosalicylaldehyde and imidazole groups was designed and synthesized as a Hg^2 + selective colorimetric chemosensor. Upon treatment of 1 with mercury ions, sensor 1 showed a color-change from colorless to yellow in a mixture of H₂O/DMF (5:95), while many other ions such as Al^3 +, Zn^2 +, Cd^2 +, Cu^2 +, Fe^2 +, Mg^2 +, Cr^3 +, Ag⁺, Co^2 +, Ni^2 +, Na⁺, K⁺, Ca^2 +, Mn^2 + and Pb^2 + had no influence. Notably, this chemosensor could distinguish clearly Hg^2 + from Cu^2 +, Ag⁺, Fe^2 + and Pb^2 +. The underlying signaling mechanism is a ligand-to-metal charge-transfer (LMCT) process. Compound 1 showed the serial formation of the 1:1 and the 1:2 complexation between 1 and Hg^2 +. This two-step binding mode was proposed based on the UV titration, ¹H NMR titration and ESI-mass studies.     

DNA and copper (II) governed fluorescence tuning of phenanthroline possessing Ru(II) complex. Interplay of electrostatic interactions

Tuning of the fluorescence properties of [Ru (bpy) ₂ (L₁)] ^2 + (1) [L₁ = 2-(2-methoxyphenyl)-1H–imidazo [4, 5-f] Kumar et al. (2010), Rawle et al. (1992) phenanthroline] by DNA and/or Cu^2 + ion have been investigated. Fluorescence of 1 gets enhanced upon binding to DNA owing to electrostatic interactions. The binding constant of 8.4 × 10⁴ has been evaluated. Cu^2 + ions though unable to alter the fluorescence intensity of free 1 but successfully sequestrate the DNA bound 1, evidently decreasing its fluorescence intensity. The reversibility of the sequestration process was ascertained by the recovery of the quenched fluorescence intensity via introduction of equimolar EDTA to the buffer system of DNA bound 1 and Cu^2 +.     

Synthesis,crystal structure and magnetic properties of a new cyanide-bridged mixed-valence copper(I)/copper(II) clathrate

A unique cyanide-bridge mixed-valence Cu^I/Cu^II clathrate of formula [Cu^I₂(CN)₃][{Cu^II(tren)}₂(μ-CN)](CF₃SO₃)₂ [tren = tris(2-aminoethyl)amine] containing cyanide-bridged [{Cu^II(tren)}₂(μ-CN)]^3 + binuclear cations stacked between anionic honeycomb layered copper(I) cyanide networks, was synthesized and structurally characterized by single crystal X-ray diffraction. Variable-temperature magnetic susceptibility studies showed that the cyanide bridge mediates a strong antiferromagnetic interaction between the copper(II) centers (J = − 160 cm^− 1, the spin Hamiltonian being defined as H = −J S_A⋅S_B).     

Synthesis and cytotoxicity of a ruthenium nitrosyl nitric oxide donor with isonicotinic acid and a cell penetrating peptide

The syntheses and properties of trans-[Ru(NH₃)₄(L)(NO)](BF₄)₃ (L = isonicotinic acid (inaH) (I) or ina-Tat48–60 (II)) are described. Tat48–60, a cell penetrating peptide fragment of the Tat regulatory protein of the HIV virus, was linked to the ruthenium nitrosyl through inaH. I and II release NO after reduction forming trans-[Ru(NH₃)₄(L)(H₂O)]^3 +. The IC₅₀ values against B16-F10 melanoma cells of I and II (21 μmol L^− 1 and 23 μmol L^− 1, respectively) are close to that of the commercially available cisplatin (33 μmol L^− 1) and smaller than similar complexes. The cytotoxicity is assigned to the NO released from I and II.     

Constructing two new crystalline metal–organic frameworks based on a mixed-donor ligand

The self-assembly of a prominent ligand, 5-(4-(1H-tetrazolyl)phen)isophthalic acid (H₃TZPI), with Zn^2 +/Cu^2 + centres generates two new MOFs, [Zn₂(TZPI)(μ₃-OH)(H₂O)₂]·2H₂O (JUC-161) and [Cu(HTZPI)(μ₂-H₂O)_0.5(H₂O)_1.5]·5(H₂O) (JUC-162). JUC-161 exhibits fascinating three-dimensional structures containing rectangular channels with dimensions of 6.5 × 3.0 Å², and JUC-162 displays 3D supramolecular structures with 12.5 × 14.6 Å² hexagonal channels. The observed structural diversity in these frameworks is due to the two distinct coordinating moieties of the H₃TZPI ligand. The photoluminescence of JUC-161 and the magnetic properties of JUC-162 are also measured at room temperature. Photoluminescence investigations reveal that JUC-161 displays a strong main emission spectrum peak at 388 nm. JUC-162 is found to exhibit an antiferromagnetic interaction between Cu^2 + ions.     

A NBD-based highly sensitive and selective colorimetric chemosensor for Ni2 + and Cu2 +

A new colorimetric chemosensor 1, containing the 7-nitrobenzo-2-oxo-1,3-diazolyl (NBD) moiety and the phenol one connected through Schiff-base linkage, has been synthesized. Sensor 1 showed remarkable color changes from pink to orange and pale brown, respectively, upon selective binding to Ni^2 + and Cu^2 + that can be identified by the naked-eye. The binding modes of sensor 1 to Ni^2 + and Cu^2 + were determined to be 1:1 stoichiometries using a Job plot and ESI-mass analysis. The sensor 1 showed high sensitivity toward Ni^2 + and Cu^2 + with the detection limits of 0.48 μM and 0.26 μM, respectively. The recognition properties of the sensor 1 toward Ni^2 + and Cu^2 + were explained by using photophysical experiments and theoretical calculations. Practically, sensor 1 functioned as a visible test strip for Ni^2 + and Cu^2 +.     

Sequential detection of copper(II) and cyanide by a simple colorimetric chemosensor

A simple colorimetric receptor 1 based on the combination of N-(5-nitro-2-pyridyl)-1,2-ethanediamine and 4-(diethylamino)-2-hydroxybenzaldehyde was synthesized for the sequential detection of Cu^2 + and CN⁻. The receptor 1 showed a distinct color change toward Cu^2 + from colorless to yellow. The detection limit of 1 for Cu^2 + (0.88 μM) was much lower than the World Health Organization guideline (31.5 μM) as the maximum allowable copper concentration in drinking water. In addition, 1-Cu^2 + complex could be used to detect cyanide by showing a color change from yellow to colorless, indicating the recovery of 1 from 1-Cu^2 +. Furthermore, the sensing mechanism of 1 for Cu^2 + was supported by theoretical calculations.     

Three novel bismuth-based coordination polymers: Synthesis,structure and luminescent properties

Three novel bismuth-based coordination polymers, [(CH₃)₂NH₂][Bi(pdc)(bdc)]·2DMF, [(CH₃)₂NH₂][Bi(tdc)₂]·1.5DMF and [Bi(bpdc)₂H₂O]·xGuest (compounds 1–3) (H₂pdc = 3,5-pyridinedicarboxylic acid, H₂bdc = 1,4-benzenedicarboxylic acid, H₂tdc = 2,5-thiophenedicarboxylic acid, H₂bpdc = 4,4′-biphenyldicarboxylic acid), have been successfully synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction. Compounds 1 and 2, which are constructed by 9-coordinated or 8-coordinated Bi^3 +, feature three-dimensional structures with hms and dia topology, respectively. However, 5-coordinated Bi^3 + based compound 3 is a two-dimensional layered structure. Compound 1 can tune emissive performance by doping different lanthanide ions Tb^3 +, Eu^3 + and Dy^3 +. Furthermore, detection of nitro explosives is investigated. All of the compounds are characterized by elemental analysis, IR spectrum and thermogravimetric analysis.     

Two new tetrazamacrocycle based Cu(II) complexes with 2D → 0D single-crystal to single-crystal transformation

Two new tetrazamacrocycle based compounds, namely, [Cu₆L₃(SO₄)₂]·SO₄·8H₂O (1) and [Cu₂L(SO₄)(H₂O)]^.2H₂O (2), have been prepared at different temperatures (H₂L = 10,21-dimethyl-3,6,14,17-tetraazatricyclo[17.3.18,12]tetracosa-1(23),8,10,12(24),19,21-hexaene-23,24-diolate). In 1, each SO₄^2 − anion bridges three [Cu₂L]^2 + cations to yield a hexagonal network, whereas in 2 each SO₄^2 − anion only links one [Cu₂L]^2 + cation to afford a discrete binuclear structure. Remarkably, the 2D network structure of 1 was transformed into the 0D structure of 2 in a single-crystal to single-crystal (SC–SC) fashion at room temperature.     

Synthesis,luminescence, and structural characterization of Zn and Cd coordination polymers of flexible bis(imidazolyl) derivatives

Coordination polymers [Zn(imc)(L¹)] · H₂O, (1, imc = iminodiacetate, L¹ = bis(N-imidazolyl)methane) [Zn(hba)₂(L²)]₂ · EtOH · 3H₂O, (2, hba = p-hydroxybenzoate, L² = bis(N-benzimidazolyl)methane), [Cd(mal)(H₂O)(L³)](3, L³ = 1,4-bis(N-imidazolyl)butane, mal = maleate) have been prepared and structurally characterized. Complex 1 consists of hexa-coordinated central Zn ions and exhibits 2D network structure. The Zn atoms in 2 have tetrahedral coordination geometry, and are linked by bis(imidazolyl) ligands into 1D chain structure. The cadmium ions in 3 are hepta-coordinated with pentagonal bipyramidal geometry. Complex 3 displays 2D grid structure. The TGA showed that the coordination polymers are stable up to 200 °C. All the three complexes are emissive at room temperature in their solid state.     

A highly selective and sensitive Schiff-base based turn-on optical sensor for Cu2 + in aqueous medium and acetonitrile

A simple “turn-on” fluorescence chemosensor L (E)-2-((4-(diphenylamino)benzylide-ne)amino)phenol has been synthesized, which displays a rapid, highly sensitive and selective detection for Cu^2 + ions amongst other metal ions. The association constant for L-Cu^2 + complex determine from Benesi–Hildbrand plot was found as 1.96 × 10⁷ M^− 1 and 5.43 × 10⁷ M^− 1 with the detection limit of 1.8 × 10^− 7 M and 8.5 × 10^− 7 M in CH₃CN and CH₃CN/H₂O (v/v = 4/6, pH = 7.4) HEPES buffer, respectively. Potential application of L for Cu^2 + detection in real water samples was also investigated.     

Hydrothermal synthesis,crystal structure and strong blue fluorescence of a novel 3D coordination polymer containing copper and zinc centers linked by isonicotinic acid ligands

The first mixed metal Zn/Cu coordination polymer, [Zn₃Cu₂(IN)₈] (1) (HIN = isonicotinic acid) was synthesized under hydrothermal conditions. The three dimensional structure of 1 has a novel topological metal-organic framework, which is built up by Zn²⁺, Cu⁺ and ligands IN to generate an open-framework with an unusual helical [–Zn(Cu)-IN–]_n chains along the b axis. The very strong blue fluorescence for 1 can be observed in the solid state.