Understanding the vapochromic response of mixed copper(i) iodide/silver(i) Iodide nanoparticles toward dimethyl sulfide.

We report on the vapochromic behavior of a series of homo- and heterometallic copper(i) iodide/silver(i) iodide nanoparticles when exposed to dimethyl sulfide (DMS) vapor. These systems show remarkable colorimetric sensing behavior via emission color upon DMS exposure, shifting from pink to green emission. Kinetics measurements of CuI/AgI nanoparticle reactions with DMS show a significant rate increase with increasing Ag(i) content. However, luminescence spectroscopy and X-ray diffraction of the post-exposure samples with varying Ag(i) content reveal that the luminophore is identical in all cases and contains no Ag(i) ions. To rationalize the experimental observations and determine the vapochromic response mechanism, molecular dynamic calculations were performed on model (111) cation-terminated surfaces of copper iodide crystals doped with variable amounts of silver. Computational studies indicate that heterometallic Cu/Ag systems have a stronger binding affinity towards DMS vapor molecules than homometallic CuI and that embedding of the DMS molecules into the surface is the primary intermediate by which the vapochromic response occurs.

Synthesis, structure and photophysical properties of a 2D network with gold dicyanide donors coordinated to aza[5]helicene viologen acceptors.

A recently synthesized photoluminescent organic acceptor, 5,10-dimethyl-5,10-diaza[5]helicene is shown to react with dicyanoaurate anions to form a 2D network N,N-dimethylaza[5]helicene dicyanoaurate. The structure of the synthesized complex was investigated via X-ray crystallography showing the presence of [Au(CN)2]- dimers and monomers within the helicene framework. Photophysical measurements between 298 K and 10 K indicate quenching of the [Au(CN)2]- anion by 5,10-dimethyl-5,10-diaza[5]helicene via an electron transfer. A Stern-Volmer and Rehm-Weller analysis shows that this is a result of quenching from transfer of an electron from [Au(CN)2]- anions to 5,10-dimethyl-5,10-diaza[5]helicene as opposed to resonance energy transfer. DFT calculations were performed to support the assignment of an electron transfer.

Synthesis and Luminescence of Optical Memory Active Tetramethylammonium Cyanocuprate(I) 3D Networks.

The structures of three tetramethylammonium cyanocuprate(I) 3D networks [NMe4]2[Cu(CN)2]2•0.25H2O (1), [NMe4][Cu3(CN)4] (2), and [NMe4][Cu2(CN)3] (3), (Me4N = tetramethylammonium), and the photophysics of 1 and 2 are reported. These complexes are prepared by combining aqueous solutions of the simple salts tetramethylammonium chloride and potassium dicyanocuprate. Single-crystal X-ray diffraction analysis of complex 1 reveals {Cu2(CN)2(µ2-CN)4} rhomboids crosslinked by cyano ligands and D3h {Cu(CN)3} metal clusters into a 3D coordination polymer, while 2 features independent 2D layers of fused hexagonal {Cu8(CN)8} rings where two Cu(I) centers reside in a linear C∞v coordination sphere. Metallophilic interactions are observed in 1 as close Cu⋯Cu distances, but are noticeably absent in 2. Complex 3 is a simple honeycomb sheet composed of trigonal planar Cu(I) centers with no Cu…Cu interactions. Temperature and time-dependent luminescence of 1 and 2 have been performed between 298 K and 78 K and demonstrate that 1 is a dual singlet/triplet emitter at low temperatures while 2 is a triplet-only emitter. DFT and TD-DFT calculations were used to help interpret the experimental findings. Optical memory experiments show that 1 and 2 are both optical memory active. These complexes undergo a reduction of emission intensity upon laser irradiation at 255 nm although this loss is much faster in 2. The loss of emission intensity is reversible in both cases by applying heat to the sample. We propose a light-induced electron transfer mechanism for the optical memory behavior observed.

Photocatalytic degradation of ibuprofen over BiOCl nanosheets with identification of intermediates.

Photocatalysis directed at the removal of persistent organic pollutants, including pharmaceuticals, has been the subject of intense recent research. Bismuth oxychloride (BiOCl) has emerged as a potential alternative to traditional photocatalysts and has shown competitive removal efficiencies. However, pathways responsible for BiOCl photodegradation have not been well characterized. The present work is the first to determine, using LC-MS/MS analysis, the pathways by which BiOCl removes ibuprofen (IBP) from water. HPLC-DAD and LC-MS/MS analyses show that BiOCl converts IBP to two primary photochemical products, 4-isobutylacetophenone (IBAP) and 1-(4-isobutylphenyl)ethanol (IBPE). The reactivity for BiOCl is attributed to interactions of the carboxylic acid group of IBP with holes in the valence band. Hydroxylated-IBP was not detected in BiOCl photocatalytic degradation experiments which would be expected in a process driven by the formation and reactivity of reactive oxygen species. These data were used to formulate a photocatalytic degradation pathway for IBP and highlight the importance of studying both primary and secondary degradation reactions for photocatalytic studies.

Alkyl Pyridinium Iodocuprate(I) Clusters: Structural Types and Charge Transfer Behavior.

The reaction of copper(I) iodide (CuI) and N-alkyl pyridinium (RPy+, R = H, Me, Et, n-propyl = Pr, n-butyl = Bu, n-pentyl = Pn, and n-hexyl = Hx) or N-butyl-3-substituted pyridinium (N-Bu-3-PyX+, X = I, Br, Cl, CN, and OMe) iodide salts yielded pyridinium iodocuprate(I) salts. Crystal structures of iodocuprate ions coupled with RPy+ include {Cu3I6 3-} n (R = H), {Cu2I3 -} n (R = Me), {Cu3I4 -} n (R = Et), {Cu6I8 2-} n (R = Pr), and {Cu5I7 2-} n (R = Bu, Pn, Hx). The [N-Bu-3-PyX]+ ions were typically paired with the 1-D chain {Cu5I7 2-} n . Diffuse reflectance spectroscopy performed on the [N-Bu-3-PyX]+ iodocuprate salts revealed that increasing the electron withdrawing capacity of the [N-Bu-3-PyX]+ system reduced the absorption edge of the iodocuprate salt. Variable temperature emission spectra of several [N-Bu-3-PyX]+ compounds revealed two emission peaks, one consistent with a cluster-centered halide to metal charge transfer and the other consistent with an intermolecular mixed halide/metal charge transfer to the organic cation. The emission intensity and emission wavelength of the mixed halide/metal to cation charge transfer depends on the organic cation substitution.

Synthesis, Structure, and Luminescence of Copper(I) Halide Complexes of Chiral Bis(phosphines).

For investigation of structure-property relationships in copper phosphine halide complexes, treatment of copper(I) halides with chiral bis(phosphines) gave dinuclear [Cu((R,R)-i-Pr-DuPhos)(µ-X)]2 [X = I (1), Br (2), Cl (3)], [Cu(µ-((R,R)-Me-FerroLANE)(µ-I)]2 (5), and [Cu((S,S)-Et-FerroTANE)(I)]2 (6), pentanuclear cluster Cu5I5((S,S)-Et-FerroTANE)3 (7), and the monomeric Josiphos complexes Cu((R,S)-CyPF-t-Bu)(I) (8) and Cu((R,S)-PPF-t-Bu)(I) (9); 1-3, 5, and 7-9 were structurally characterized by X-ray crystallography. Treatment of iodide 1 with AgF gave [Cu((R,R)-i-Pr-DuPhos)(µ-F)]2 (4). DuPhos complexes 1-4 emitted yellow-green light upon UV irradiation at room temperature in the solid state. This process was studied by low-temperature emission spectroscopy and density functional theory (DFT) calculations, which assigned the luminescence to (M + X)LCT (Cu2X2 to DuPhos aryl) excited states. Including Grimme's dispersion corrections in the DFT calculations (B3LYP-D3) gave significantly shorter Cu-Cu distances than those obtained using B3LYP, with the nondispersion-corrected calculations better matching the crystallographic data; other intramolecular metrics are better reproduced using B3LYP-D3. A discussion of the factors leading to this unusual observation is presented.

Photocatalysis of fenoxycarb over silver-modified zeolites.

Two samples of silver doped into zeolite Y were prepared and characterized. ICP and SEM-EDS analysis indicate that the AgY1 sample contains twice the amount of silver compared to the AgY2 sample. Solid state luminescence spectroscopy shows variations in the emission modes of the site-selective luminescence where various luminophores might be excited upon selecting the proper excitation energy. The selected material effectively decomposed the pesticide fenoxycarb in aqueous solution. The photodecomposition of fenoxycarb reached 80 % upon irradiation for 60 min in the presence of the AgY1 catalyst. 2-(4-Phenoxy-phenoxy)ethyl] carbamic acid (1) and 1-amine-2-(phenoxy-4-ol) ethane (2) were identified as products for both uncatalyzed solution and the catalyzed fenoxycarb with AgY2 catalyst. Whereas, compound (2) was the only product identified in the catalyzed reaction with AgY1.

Photophysical properties of {[Ag(CN)2](-)}2 complexes trapped in a supramolecular electron-acceptor organic framework.

The organic acceptor 1,1'-bis-(2,4-dinitrophenyl)-4,4'-bipyridinium (DNP(2+)) reacts with dicyanoargentate to form a supramolecular complex with the general formula: {[Ag(CN)2]2DNP}·2H2O. The photophysical properties of this complex were determined using solid-state luminescence experiments including luminescence lifetime measurements. Luminescence of the dicyanoargentate dimers is observed both by direct excitation of the silver dimers as well as excitation of the DNP(2+) followed by indirect non-radiative energy transfer to the silver dimer units for emission. The structures themselves were characterized using X-ray crystallography. The results are compared to those from the previously studied {[Au(CN)2]2DNP}·4H2O system.

Photocatalytic degradation of 17α-ethinylestradiol (EE2) in the presence of TiO2-doped zeolite.

Current design limitations and ineffective remediation techniques in wastewater treatment plants have led to concerns about the prevalence of pharmaceutical and personal care products (PPCPs) in receiving waters. A novel photocatalyst, TiO2-doped low-silica X zeolite (TiO2-LSX), was used to study the degradation of the pharmaceutical compound, 17α-ethinylestradiol (EE2). The catalyst was synthesized and characterized using XRD, BET surface analysis, SEM-EDAX, and ICP-OES. The effects of different UV light intensities, initial EE2 concentrations, and catalyst dosages on the EE2 removal efficiency were studied. A higher EE2 removal efficiency was attained with UV-TiO2-LSX when compared with UV-TiO2 or UV alone. The EE2 degradation process followed pseudo-first-order kinetics. A comprehensive empirical model was developed to describe the EE2 degradation kinetics under different conditions using multiple linear regression analysis. The EE2 degradation mechanism was proposed based on molecular calculations, identification of photoproducts using HPLC-MS/MS, and reactive species quenching experiments; the results showed that oxidative degradation pathways initiated by hydroxyl radicals were predominant. This novel TiO2-doped zeolite system provides a promising application for the UV disinfection process in wastewater treatment plants.

Structure and emissive properties of heterobimetallic Ln-Au coordination polymers: role of Tb and Eu in non-aurophilic [nBu4N]2[Ln(NO3)4Au(CN)2] versus aurophilic Ln[Au(CN)2]3·3H2O/3D2O chains.

This investigation is focused on comparing photophysical properties between two series of lanthanide-dicyanoaurate coordination polymers that contain and lack aurophilic interactions, respectively. Luminescence and crystallographic studies have been carried out on five different coordination polymer chain frameworks: the non-aurophilic [(n)Bu4N]2[LnxGd1-x(NO3)4Au(CN)2] (Ln = Eu, Tb; x = 0.01, 0.02, 0.04, 0.08) and[(n)Bu4N]2[EuxTb1-x(NO3)4Au(CN)2] (x = 0.25, 0.5, 0.75), as well as the analogous solid-solutions of aurophilic LnxGd1-x[Au(CN)2]3·3H2O and EuxTb1-x[Au(CN)2]3·3H2O. The single-crystal structures of M[Au(CN)2]3 ·3H2O (M = Eu, Gd) are also reported for comparison. In the aurophilic frameworks the close proximity of gold(I) centers on neighboring chains allows for Au-Au interactions to take place that facilitate energy transfer between lanthanides. Terbium- and europium-doped aurophilic frameworks show energy transfer between one of the lanthanide ions and dicyanoaurate centers as observed via luminescence measurements. In the non-aurophilic frameworks the [(n)Bu4N] cations separate the Au-Au chains, thereby preventing interaction between them, and preventing energy transfer. By preparing the aurophilic EuxTb1-x[Au(CN)2]3·3D2O frameworks, it was shown that the O-H vibrational energy in the hydrated (aurophilic) samples can partially quench the Ln signal.

A Review of Luminescent Anionic Nano System: d10 Metallocyanide Excimers and Exciplexes in Alkali Halide Hosts.

Dicyanoaurate, dicyanoargentate, and dicyanocuprate ions in solution and doped in different alkali halide hosts exhibit interesting photophysical and photochemical behavior, such as multiple emission bands, exciplex tuning, optical memory, and thermochromism. This is attributed to the formation of different sizes of nanoclusters in solution and in doped hosts. A series of spectroscopic methods (luminescence, UV-reflectance, IR, and Raman) as well as theoretical calculations have confirmed the existence of excimers and exciplexes. This leads to the tunability of these nano systems over a wide wavelength interval. The population of these nanoclusters varies with temperature and external laser irradiation, which explains the thermochromism and optical memory. DFT calculations indicate an MLCT transition for each nanocluster and the emission energy decreases with increasing cluster size. This is in agreement with the relatively long life-time for the emission peaks and the multiple emission peaks dependence upon cluster concentration.

Network formation and photoluminescence in copper(I) halide complexes with substituted piperazine ligands.

The synthesis, X-ray structures and photophysics of ten complexes of CuX (X = I or Br) with bridging N-substituted and N,N'-disubstituted piperazines (Pip) are presented. Depending on the steric demand of the Pip substituents, the complexes fall into four categories: (CuX)(4)(Pip)(2), which are networks of linked Cu(4)X(4) cubane units, (CuX)(2)(Pip), which are chains of linked Cu(2)X(2) rhombs, and (CuX)(2)(Pip)(2) or (CuX)(4)(Pip)(4), which are simple rhomboid dimers and cubane tetramers. A combination of spectroscopic studies and DFT calculations was used to investigate the luminescence of the products. The results suggest that the relatively high energy emission seen in dimers is due to cluster-centred (XMLT/metal-centred) excitations for the aliphatic amines and MLCT (d →π*) for aromatic amines, and low energy emission seen in the tetramers is the result of cluster-centred transitions. The (CuI)(2)(Pip) complexes act as sensor materials, undergoing irreversible reaction with aliphatic and aromatic amines (Nu) in the vapour state, irreversibly producing cubanes (CuI)(4)Nu(4), with corresponding production of long wavelength emission.

Estimating pesticide sampling rates by the polar organic chemical integrative sampler (POCIS) in the presence of natural organic matter and varying hydrodynamic conditions.

The polar organic chemical integrative sampler (POCIS) was calibrated to monitor pesticides in water under controlled laboratory conditions. The effect of natural organic matter (NOM) on the sampling rates (R(s)) was evaluated in microcosms containing <0.1-5 mg L(-1) of total organic carbon (TOC). The effect of hydrodynamics was studied by comparing R(s) values measured in stirred (SBE) and quiescent (QBE) batch experiments and a flow-through system (FTS). The level of NOM in the water used in these experiments had no effect on the magnitude of the pesticide sampling rates (p > 0.05). However, flow velocity and turbulence significantly increased the sampling rates of the pesticides in the FTS and SBE compared to the QBE (p < 0.001). The calibration data generated can be used to derive pesticide concentrations in water from POCIS deployed in stagnant and turbulent environmental systems without correction for NOM.

Kinetics and equilibrium properties of the biosorption of Cu2+ by algae.

The purpose of this study was to examine the kinetics and equilibrium properties of freshwater algae with Cu(2+). This was a model system to explore using algae as biosensors for water quality. Methods included making luminescence measurements (fluorescence) and copper ion-selective electrode (CuISE) measurements vs. time to obtain kinetic data. Results were analyzed using a pseudo-first-order model to calculate the rate constants of Cu(2+) uptake by algae: k (p(Cu-algae)) = 0.0025 ± 0.0006 s(-1) by CuISE and k (p(Cu-algae)) = 0.0034 ± 0.0011 s(-1) by luminescence. The binding constant of Cu-algae, K (Cu-algae), was 1.62 ± 0.07 × 10(7) M(-1). Fluorescence results analyzed using the Stern-Volmer relationship indicate that algae have two types of binding sites of which only one appears to affect quenching. The fluorescence-based method was found to be able to detect the reaction of algae with Cu(2+) quickly and at a detection limit of 0.1 mg L(-1).

Heterobimetallic lanthanide-gold coordination polymers: structure and emissive properties of isomorphous [(n)Bu4N]2[Ln(NO3)4Au(CN)2] 1-D chains.

A new series of lanthanide-containing dicyanoaurate coordination polymers, [(n)Bu(4)N](2)[Ln(NO(3))(4)Au(CN)(2)] (Ln = Nd, Eu, Gd or Tb), were synthesized and structurally characterized. They form an isomorphous series, crystallizing in the space group I2(1)2(1)2(1). The structure is composed of a one dimensional zigzag of Ln-N-C-Au-C-N-Ln chains with no intra- or inter-chain aurophilic interactions. The series is related to and can be described as a reduced dimensionality analogue of the previously studied Ln[Au(CN)(2)](3)·3H(2)O. Unlike the Ln[Au(CN)(2)](3)·3H(2)O series, there is no efficient energy transfer between dicyanoaurate and the lanthanide metal centers in the complexes and they essentially act as two separate emissive chromophores.

Photophysical properties of {[Au(CN)2]-}2 dimers trapped in a supramolecular electron-acceptor organic framework.

Dicyanoaurate reacts with the organic acceptor molecule, 1,1'-bis-(2,4-dinitrophenyl)-4,4'-bipyridinium, DNP, to form a supramolecular complex with the general formula {[Au(CN)(2)](2)DNP}·4H(2)O. The complex was characterized by X-ray crystallography, and its photophysical properties were investigated in the solid-state. Although the initial (DNP)Cl(2) compound does not show photoluminescence behavior and the dicyanoaurate shows photoluminescence only in the UV range, the resulting supramolecular complex displays two simultaneous, essentially independent, photoluminescence bands in the visible range originating from individual contributions of the DNP unit and the dicyanoaurate dimers. This unusual simultaneous photoluminescence behavior displayed by both the dicyanoaurate donor units and the redox-active 4,4'-bipyridinium acceptor have lifetimes of 0.5 µs and several hundred µs, respectively.

Copper(I) thiocyanate-amine networks: synthesis, structure, and luminescence behavior.

A series of metal-organic networks of CuSCN were prepared by direct reactions with substituted pyridine and aliphatic amine ligands, L. Thiocyanate bridging is seen in all but 1 of 11 new X-ray structures. Structures are reported for (CuSCN)L sheets (L = 3-chloro- and 3-bromopyridine, N-methylmorpholine), ladders (L = 2-ethylpyridine, N-methylpiperidine), and chains (L = 2,4,6-collidine). X-ray structures of (CuSCN)L(2) are chains (L = 4-ethyl- and 4-t-butylpyridine, piperidine, and morpholine). A unique N-thiocyanato monomer structure, (CuSCN)(3-ethylpyridine)(3), is also reported. In most cases, amine ligands are thermally released at temperatures <100 °C. Strong yellow-to-green luminescence at ambient temperature is observed for the substituted pyridine complexes. High solid state quantum efficiencies are seen for many of the CuSCN-L complexes. Microsecond phosphorescence lifetimes seen for CuSCN-L are in direct contrast to the nanosecond-lifetime emission of CuSCN. MLCT associated with pyridine π* orbitals is proposed as the excitation mechanism.

Changes in electronic properties of polymeric one-dimensional {[M(CN)2]-}n (M = Au, Ag) chains due to neighboring closed-shell Zn(II) or open-shell Cu(II) ions.

A series of d(10) dicyanometallate polymeric compounds were studied by electronic spectroscopy and density functional theory (DFT) calculations. In these materials, the negatively charged one-dimensional (1D) polymeric chains are linked together by [M(en)(2)](2+) (M = Cu(II) and Zn(II); en = ethylenediamine). More than innocent building blocks, the [M(en)(2)](2+) units offer a possible synthetic way to modify electronic properties of the materials. Through its low energy d-d excited state, the d(9) copper(II) ions offer deactivation pathways for the normally emissive dicyanometallate polymer. Deactivation was shown to be specific to the excited state energy.

Reversible luminescent reaction of amines with copper(I) cyanide.

Copper(i) cyanide exposed to various liquid or vapor-phase amines (L) at ambient temperature produces a variety of visible photoluminescence colors via reversible formation of amine adducts. The adducts show phase matches to authentic (CuCN)L(n), n = 0.75-2.0, produced by heating CuCN with liquid amine.

Copper(I) cyanide networks: synthesis, structure, and luminescence behavior. Part 2. Piperazine ligands and hexamethylenetetramine.

A variety of photoluminescent, and in some cases thermochromic, metal-organic networks of CuCN were self-assembled in aqueous reactions with amine ligands: (CuCN) 2(Pip) ( 1a), (CuCN) 20(Pip) 7 ( 1b), (CuCN) 7(MePip) 2 ( 2), (CuCN) 2(Me 2Pip) ( 3a), (CuCN) 4(Me 2Pip) ( 3b), (CuCN) 7(EtPip) 2 ( 4), (CuCN) 4(Et 2Pip) ( 5), (CuCN) 3(BzPip) 2 ( 6a), (CuCN) 5(BzPip) 2 ( 6b), (CuCN) 7(BzPip) 2 ( 6c), (CuCN) 4(BzPip) ( 6d), (CuCN) 2(Bz 2Pip) ( 7), (CuCN)(Ph 2CHPip) ( 8a), (CuCN) 2(Ph 2CHPip) ( 8b), (CuCN) 3(HMTA) 2 ( 9a), (CuCN) 5(HMTA) 2 ( 9b), and (CuCN) 5(HMTA) ( 9c) (Pip = piperazine, MePip = N-methylpiperazine, Me 2Pip = N, N'-dimethylpiperazine, EtPip = N-ethylpiperazine, Et 2Pip = N, N'-diethylpiperazine, BzPip = N-benzylpiperazine, Bz 2Pip = N, N'-dibenzylpiperazine, Ph 2CHPip = N-(diphenylmethyl)piperazine, and HMTA = hexamethylenetetramine). New X-ray structures are reported for 1b, 2, 3b, 4, 5, 6a, 6d, 7, 8b, 9b, and 9c. An important structural theme is the formation of (6,3) (CuCN) 2(piperazine) sheets with or without threading of independent CuCN chains. Strong luminescence at ambient temperature is observed for all but complexes 6 and 7. All luminescent compounds show a broad emission band in the blue region at about 450 nm attributable to metal-to-ligand charge transfer behavior based on the large Stokes shift between excitation and emission maxima. 3, 8, and 9 are thermochromic due to an additional lower energy emission band, which is absent at 77 K.