Methanol triggered ligand flip isomerization in a binuclear copper(I) complex and the luminescence response

Methanol drives the blue emissive complex, [Cu(2)(dppy)(3)(MeCN)](BF(4))(2) (dppy = diphenylphosphino-pyridine), with a head-to-tail arrangement of the three bridging phosphine ligands to convert to its linkage isomer (head-to-head, green emissive) in the solid state, and the transformation could be reversibly realized through recrystallization in different solvents.     

Determination of copper(II) in a complex matrix after prereduction to copper(I) in a flow-injection system with an amperometric detector

A flow-injection system with a carbon paste detector is proposed for the determination of copper in complex media at +0.050 V vs. Ag/AgCl. Both the reduction current peak of Cu(II) and the oxidation peak of Cu(I) (obtained in the presence of hydroxylamine in the reagent stream) were proportional to the Cu(II) concentration in the original sample. The stabilization of Cu(I) in the hydroxylamine system provides a novel approach; the inherent repeatability of operation of flow-injection systems (timing, etc.) proved ideal for this utilization. Acidified Cu(II) samples containing additional metal ions [Fe(lI), Zn(II), Pb(II)] and relatively high concentrations of serum albumin were analysed. A chelating column retained heavy metal ions while allowing albumin to run to waste. The retained metals were subsequently eluted with nitric acid into a stream of sodium acetate or sodium acetate-hydroxyl- amine. Before reaching the detector, the pH of the sample plug was adjusted. With the hydroxylamine system, Fe(III) interference was minimized and the sensitivity and reproducibility were improved. The sample throughput was 25 h^?1. National Bureau of Standards Standard Reference Material 909 Human Serum was used to test the method.     

Bright phosphorescence of a trinuclear copper(I) complex: luminescence thermochromism, solvatochromism, and "concentration luminochromism"

A photophysical study is reported for the trinuclear copper(I) complex {[3,5-(CF3)2Pz]Cu}3. The neutral compound exhibits multicolor bright phosphorescent emissions both in the solid state and in solution. The emission can be tuned to multiple visible colors by controlling the temperature, solvent, and {[3,5-(CF3)2Pz]Cu}3 concentration, giving rise to luminescence thermochromism, luminescence solvatochromism, and a new optical phenomenon called "concentration luminochromism", respectively.     

Efficient luminescence from a copper(I) complex doped in organic light-emitting diodes by suppressing C-H vibrational quenching

Efficient luminescence was realized by suppressing not only excited-state distortion but also C-H vibrational quenching in a Cu complex. Organic light-emitting diodes containing the Cu complex as an emitting dopant exhibited a maximum external quantum efficiency of 7.4%.     

Aggregation-induced phosphorescence and mechanochromic luminescence of a tetraphenylethene-based gold(I) isocyanide complex

In this study, a new twisting gold(I) isocyanide complex based on tetraphenylethene (TPE), TPE-NC-Au, was designed and synthesized. It exhibits aggregation induced phosphorescence (AIP) characteristics, owing to the incorporation of Au moiety and conformation rigidification in the aggregated states. Moreover, the emission color of the crystalline solid of TPE-NC-Au changes from blue (454 nm) to green (500 nm) in response to mechanical grinding, due to the combined effects of conformation planarization, enhanced π…π stacking, as well as the emergence of aurophilic interactions in the ground amorphous state. Notably, the emission color can be restored upon solvent fuming, associating with the reconstruction of crystalline lattices. The AIP and switchable mechanochromism of TPE-NC-Au make it suitable for potential applications in bioimaging, sensing, and optoelectronic devices.     

Complex formation constants for the aqueous copper(I)-acetonitrile system by a simple general method

A simple spectrophotometric method for the evaluation of formation constants for aqueous copper(I) has been developed, based on the kinetics of reduction of Co(III)(NH(3))(5)X complexes. The method has been applied to the aqueous copper(I)-acetonitrile system to determine the successive formation constants beta(1), beta(2), and beta(3) as 4.3 x 10(2) M(-)(1), 1.0 x 10(4) M(-)(2), and 2.0 x 10(4) M(-)(3), respectively, in 0.14 M NaClO(4)/HClO(4) at 21 +/- 1 degrees C.     

The unusual thermochromic NIR luminescence of Cu(I) clusters: tuned by Cu-Cu interactions and packing modes

Two hexanuclear Cu(I) clusters [Cu(I)(3)(4-ptt)(3)](2)·3DMF·3H(2)O (1) and [Cu(I)(4-ptt)](6)·8DMF·7H(2)O (2) (4-Hptt = 5-(pyridin-4-yl)-1H-1,2,4-triazole-3-thiol, DMF = N,N-dimethylformamide), were synthesized and characterized. Compounds 1 and 2 with similar coordination environments are isomers, but their detailed structures are different due to the reaction temperature tuning effect. Both 1 and 2 extend from monomers to 3D supramolecules with the help of hydrogen bonding between the triazole and pyridine from the 4-ptt ligands. The Cu(6)S(6) units of 1 pack in a polydirectional array, while the Cu(6)S(6) units in 2 extend in one direction and link the planes of adjacent ligands to enhance the delocalization of π electrons. Their varied Cu-Cu interactions and individual packing modes cause differences in luminescent and thermostable behaviors. Compound 1 exhibits an unusually long wavelength at about 900 nm and a higher thermal stability; while the emission of 2 splits into two bands (high-energy and low-energy emission bands) as the temperature decreases. Therefore, the emissions of 1 originate from a (3)CC transition, and those of 2 are from a mixture of (3)CC and MLCT.     

Reaction of a copper(II)-nitrosyl complex with hydrogen peroxide: putative formation of a copper(I)-peroxynitrite intermediate

The reaction of a Cu(II)-nitrosyl complex (1) with hydrogen peroxide at -20 °C in acetonitrile results in the formation of the corresponding Cu(I)-peroxynitrite intermediate. The reduction of the Cu(II) center was monitored by UV-visible spectroscopic studies. Formation of the peroxynitrite intermediate has been confirmed by its characteristic phenol ring nitration reaction as well as isolation of corresponding Cu(I)-nitrate (2). On air oxidation, 2 resulted in the corresponding Cu(II)-nitrate (3). Thus, these results demonstrate a possible decomposition pathway for H(2)O(2) and NO through the formation of a peroxynitrite intermediate in biological systems.     

Dioxygen activation by a neutral beta-diketiminato copper(I) ethylene complex

The synthesis and structure of two thermally stable neutral beta-diketiminato copper(I) olefin complexes are presented along with the structure of a Cu(II)2(mu-OH)2 dimer that results from the reaction of the Cu(I) ethylene complex with O2 via the proposed intermediacy of a Cu(III)2(mu-O)2 species.     

Supramolecular assembly and solvochromic luminescence of a Au(I) complex containing di(4-pyridylmethyl)aminedithiocarbamate

The di(4-pyridylmethyl)aminedithiocarbamate (DPMACS₂) ligand was used to react with (Me₂S)AuCl to give a dinuclear complex, [Au(DPMACS₂)]₂, which shows both intramolecular Au(I)⋅⋅⋅Au(I) distances of 2.741(9)–2.788(1) Å and intermolecular Au(I)···Au(I) contacts of 2.917(5)–3.047(7) Å, leading to 1-D Au(I) chains in the solid state. In addition, complex [Au(DPMACS₂)]₂ shows the luminescence at 555 nm at room temperature while excited, and almost no energy shift for the luminescence at 553 nm upon grinding has been observed. In this regard, we further examined the solvochromic luminescence upon grinding with various solvents, and the luminescence is within 549–572 nm. It is noted that the solvochromic luminescence for dichloromethane (566 nm) and 1,2-dichloroethane (572 nm) has been observed, and the original luminescence at 555 nm can be restored upon solvent loss. Indeed, such red-shifts for the solvochromic luminescence are most likely due to a decrease in intermolecular Au(I)⋅⋅⋅Au(I) contacts while solvents entering into crystal lattices upon grinding and it is a reversible process upon solvent loss.     

A sensitized europium complex generated by micromolar concentrations of copper(I): toward the detection of copper(I) in biology

Formation of a luminescent device by the Huisgen 1,3-dipolar cycloaddition reaction between a Eu(III) complex and dansyl azide is reported. This reaction is catalyzed by a common biological copper(I) complex [GS--Cu(I)], and the resultant copper(I) catalytic sensor shows a 10-fold enhancement of europium luminescence emission.     

Unprecedented binding and activation of CS2 in a dinuclear copper(I) complex

The first structural characterisation of a copper-carbondisulfide complex revealed a hitherto unknown binding mode for CS(2): it interacts with two metal centres (Cu(I)) simultaneously via both C=S π bonds. DFT calculations showed that complex formation occurs mainly due to a donation of electron density from the copper centres into the C=S π* orbitals.     

Mononuclear copper(II)-hydroperoxo complex derived from reaction of copper(I) complex with dioxygen as a model of DbetaM and PHM

A mononuclear copper(II)-hydroperoxo species has been generated by the reaction of Cu(I)-H2BPPA complex with dioxygen, which illustrates the enzymatic reaction process of the CuB site in the DbetaM and PHM.     

Chemical modulation of the luminescence of a DNA-bound diruthenium(II) complex by copper(II) ion and EDTA

A method for the chemical modulation of the photoluminescence of a DNA-bound diruthenium(II) complex, [(bipy)₂Ru(bpib)Ru(bipy)₂]⁴⁺ (bipy = 2,2′-bipyridine, bpib = 1,4-bis([1, 10]phenanthroline [5,6-d]imidazol-2-yl) benzene) by the introduction of Cu²⁺ ion and EDTA has been developed. The diruthenium(II) complex showed strong photoluminescence both in buffer solutions and on an indium-tin oxide (ITO) surface, which was not modulated by Cu²⁺ or EDTA. The DNA-bound [(bipy)₂Ru(bpib)Ru(bipy)₂]⁴⁺ with a binding constant of 3.8 × 10⁴ M⁻¹ showed an enhancement in the luminescence based on the electrostatic interaction between the complex and DNA. The presence of Cu²⁺ was found to quench the luminescence of DNA-bound [(bipy)₂Ru(bpib)Ru(bipy)₂]⁴⁺, but the quenched luminescence was recovered by addition of an equimolar concentration of EDTA. Hence, the photoluminescence of DNA-bound [(bipy)₂Ru(bpib)Ru(bipy)₂]⁴⁺ depends strongly on the introduction of Cu²⁺ and EDTA.     

Structure study and luminescence thermochromism in hexanuclear 6-methyl-2-pyridinethiolato copper(I) crystals

The structure of hexanuclear 6-methyl-2-pyridinethiolato copper(I) [Cu6(6-mpyt)(6)] crystals has been studied by the X-ray diffraction analysis. These crystals show highly efficient luminescence whose color changes drastically from red to green-blue with lowering temperature from room temperature (RT) to liquid nitrogen temperature (LNT). This is a new example of luminescence thermochromism for hexanuclear copper(I) cluster compounds. Two relaxed luminescence bands appear predominantly: one (CC-band), red luminescence appearing in the lower-energy region around 1.8 eV at higher temperature, is assigned to the transition between intramolecular orbitals (MO) of a Cu cluster center (CC), and the other (CT-band), green-blue luminescence appearing at the higher energy side of 2.6 eV than the CC-band at lower temperature, is assigned to a charge transfer (CT) transition from the CC-MO to a ligand MO. Additionally, the CT band can be deconvoluted to two subbands CT(L) and CT(H). The intensities of the CC- and the CT-bands change complementarily with temperature via a thermal activation process, giving the thermochromism. All of these band shapes can be fitted by a Gaussian function, and their widths are fairly large obeying the hyperbolic cotangent law. These features reflect our system to be a strong electron-lattice coupling one. The relaxation process of the photoexcited states is discussed in terms of a configuration coordinate model.     

Dimerization mechanism of bis(triphenylphosphine)copper(I) tetrahydroborate: proton transfer via a dihydrogen bond

The mechanism of transition-metal tetrahydroborate dimerization was established for the first time on the example of (Ph(3)P)(2)Cu(η(2)-BH(4)) interaction with different proton donors [MeOH, CH(2)FCH(2)OH, CF(3)CH(2)OH, (CF(3))(2)CHOH, (CF(3))(3)CHOH, p-NO(2)C(6)H(4)OH, p-NO(2)C(6)H(4)N═NC(6)H(4)OH, p-NO(2)C(6)H(4)NH(2)] using the combination of experimental (IR, 190-300 K) and quantum-chemical (DFT/M06) methods. The formation of dihydrogen-bonded complexes as the first reaction step was established experimentally. Their structural, electronic, energetic, and spectroscopic features were thoroughly analyzed by means of quantum-chemical calculations. Bifurcate complexes involving both bridging and terminal hydride hydrogen atoms become thermodynamically preferred for strong proton donors. Their formation was found to be a prerequisite for the subsequent proton transfer and dimerization to occur. Reaction kinetics was studied at variable temperature, showing that proton transfer is the rate-determining step. This result is in agreement with the computed potential energy profile of (Ph(3)P)(2)Cu(η(2)-BH(4)) dimerization, yielding [{(Ph(3)P)(2)Cu}(2)(μ,η(4)-BH(4))](+).