Luminescence and thermal behavior by simultaneous TG/DTG–DTA coupled with MS of neutral copper (I) complexes with heterocyclic thiones

Copper(I) halide complexes formulated as [(L)CuX(μ₂-L)₂CuX(L)] (X = Cl, Br and L = pyridine-2-thione (py2SH), or 4,6-dimethylpyrimidine-2-thione (dmpymtH)) were prepared, and their photoluminescence and thermal properties were investigated. The complexes are strongly emissive in the solid state, with the emissions being dominated by large Stokes shifts (>200 nm), which are depending on both the heterocyclic thione and the nature of the halogen. These emissions can be assigned to MLCT with some mixing of the halide-to-ligand (XL) CT characters. Simultaneous TG/DTG–DTA technique, coupled with MS for the analysis of the gaseous decomposition products, was used for two complexes with the dmpymtH ligand to determine their thermal degradation, which was found to be very complicated. In inert atmosphere the residues at 1,000 °C (verified with PXRD) were a mixture of Cu₂S and CuX, while at 1,300 °C a mixture of Cu₂S and Cu. In oxygen atmosphere the residues were CuO.     

Luminescence and thermal behavior of copper (I) complexes with heterocyclic thiones. Part II: cationic complexes

Copper (I) halide complexes formulated as [(L)₂Cu(μ₂-L)₂Cu(L)₂]²⁺ 2Χ⁻, (X = Cl, Br and L = pyridine-2-thione (py2SH) or 4,6-dimethylpyrimidine-2-thione (dmpymtH)) were prepared, and their photoluminescence and thermal properties were investigated. The complexes are strongly emissive in the solid state, with the emissions being dominated by large Stokes shifts (>200 nm), which are depending on both the heterocyclic thione and the nature of the halogen. These emissions can be assigned to MLCT with some mixing of the halide-to-ligand (XL) CT characters. Simultaneous TG/DTG–DTA technique was used for two complexes with the dmpymtH ligand to determine their thermal degradation, which was found to be very complicated. In inert atmosphere the residues at 1,000 °C (verified with PXRD) were mainly Cu₂S, while at 1,300 °C a mixture of Cu₂S and Cu. In oxygen atmosphere the residues were CuO.     

Syntheses, Structures, and Nonlinear Optical Properties of Two Crown-like Heteroselenometallic Compounds [Et4N]4[(μ5-WSe4)(CuX)5(μ-X)2] (X = Cl, Br)

Two isostructural crown-like heteroselenometallic cluster compounds, [Et₄N]₄[(μ₅-WSe₄)(CuX)₅(μ-X)₂] (X = Cl 1, Br 2), were prepared from the reactions of [Et₄N]₂[WSe₄] with CuX and [Et₄N]X· xH₂O in the presence of 2-picoline and characterized by single-crystal diffraction analysis. The [(μ₅-WSe₄)(Cu-X)₅(μ-X)₂]⁴⁻ anions in the cluster compounds consists of five CuX fragments coordinated to the five edges of the tetrahedral [WSe₄]²⁻ moiety along with two bridging halides connected to each of the two pairs of the symmetric copper atoms, exhibiting a novel crown-like core structure. The nonlinear optical absorption and refraction of cluster compound 2 were determined to be α₂ = 6.15 × 10⁻¹⁰ m/W and n ₂ = 4.18 × 10⁻¹¹ esu, respectively.     

Synthesis,structural characterization and substituent effects of two copper(II) complexes with benzaldehyde ortho-oxime ligands

Two new Cu(II) complexes, [Cu(L¹)₂] (1) and [Cu(L²)₂] (2) (HL¹ = (E)-3-bromo-5-chloro-2-hydroxy benzaldehyde O-methyl oxime; HL² = (E)-3-bromo-5-chloro-2-hydroxy benzaldehyde O-ethyl oxime), have been synthesized and characterized by physicochemical and spectroscopic methods. X-ray crystallographic analyses show that complexes 1 and 2 have similar structures, consisting of one Cu(II) atom and two L⁻ units. In both complexes, the Cu(II) atom, lying on an inversion center, is four-coordinated in a trans-CuN₂O₂ square-planar geometry by two phenolate O and two oxime N atoms from two symmetry-related N,O-bidentate oxime ligands. Moreover, both complexes form an infinite three-dimensional supramolecular structure involving intermolecular C–H···Br hydrogen bonds and π···π stacking interactions between the metal chelate rings and aromatic rings. Substituent effects in the two complexes are discussed.     

Synthesis and structures of copper(I) and cobalt(III) dimers with the dicyano-acetic acid methyl ester anion derived from TCNE

In the presence of CoCl₂ · 6H₂O or CuCl, the reaction of tetracyanoethylene and CH₃OH provides a dicyano-acetic acid methyl ester anion (L1), which has been obtained as a bridged ligand in two compounds [(PPh₃)₂(NC)₂Co^III(μ₂-L1₂)Co^III(CN)₂(PPh₃)₂] · (PPh₃)(CH₃OH) 1 and [(PPh₃)₂Cu^I(μ₂-L1₂)Cu^I(PPh₃)₂] 2. The coordination geometry of the Co atom in 1 is distorted octahedral, and the Co atoms are μ₂-bridged by two pairs of L. For compound 2, Cu is coordinated with two P atoms from PPh₃ and two N atoms of L1, and two Cu atoms are linked by μ₂-bridged L1. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Recent studies on chemistry of novel μ-CO-containing butterfly Fe/E (E=S,Se,Te) cluster salts

This article describes recent developments in chemical study on a series of butterfly-shaped μ-CO-containing Fe/E (E = S, Se, Te) cluster salts. These salts include eleven novel cluster anions, which are the single butterfly one μ-CO-containing [(μ-RE)(μ-CO)Fe2(CO)6]- (A), the double butterfly two μ-CO-containing {[(μ-CO)Fe2(CO)6]2(μ-EZE-μ)}2- (B, E = S; C, E = Se), the triple butterfly three μ-CO- containing {[(μ-CO)Fe2(CO)6]3[(μ-SCH2CH2)3N]}3- (D), {[(μ-CO)Fe2(CO)6]3[1,3,5-(μ-SCH2)3C6H3]}3- (E), {[(μ- CO)...     

Syntheses and Crystal Structures of Polynuclear Cu(I) Complexes Containing the 1,1′-Bis-(diphenylphosphino)-ferrocene Ligand

Summary.  The reaction between [Cu(NCMe)₄][PF₆] and 1,1′-bis-(diphenylphosphino)-ferrocene (dppf) in several ratios, solvents, and conditions led to the synthesis and structural characterization of the Cu(I) complexes [Cu(dppf)(Odppf)][PF₆] (1), [(dppf)Cu(μ-dppf)Cu(dppf)][PF₆]₂ (2), and [(dppf)Cu(μ-Cl)₂Cu(dppf)] (3). Although 1 and the cation in 2 were known, the first was structurally characterized for the first time, exhibiting a significant asymmetry in the coordination sphere of Cu(I) owing to the presence of oxygen. In 2, the PF₆ ⁻ anion led to an interesting crystal packing with large open channels containing water. Finally, DFT calculations on a model of 3 showed that its HOMO exhibits, besides Fe, a significant Cu and Cl character, which is reflected in its electrochemical properties. Received July 14, 2000. Accepted July 21, 2000     

Synthesis and properties of the Cu(II) complexes with chiral bis{( E )-[(1 S ,4 R )-Δ7,8-1-amino-2- para -menthalidene]aminohydroxy}methane (L — a derivative of natural terpenoid ( R )-(+)-limonene). Crystal structure of the [Cu(L)(μ-Cl)CuCl3] · iso -PrOH solvate

The Cu₂LCl₄ complex (I) with chiral bis{(E)-[(1S,4R)-Δ^7,8-1-amino-2-para-menthalidene]aminohydroxy} methane (L — a derivative of natural monoterpenoid (R)-(+)-limonene) is synthesized. The crystal structure of the solvate of complex I[Cu(L)(μ-Cl)CuCl₃] · iso-PrOH (II) is determined by X-ray diffraction analysis. Structure II is based on molecules of the [Cu(L)(μ-Cl)CuCl₃] binuclear complexes in which L is the tetradentate cycleforming ligand. One Cl atom manifests the bridging function. The CuN₄ Cl coordination unit is a square pyramid, and CuCl₄ is a distorted tetrahedron. The iso-PrOH molecules are localized in cavities between the layers of structure II. The μ_eff value for complex I is 2.56 μB and indicates the absence of an appreciable interaction between the Cu²⁺ ions in the Cu(II)-Cl-Cu(II) exchange cluster. The compound CuLCl₂· H₂O (III) is synthesized. The μ_eff value for compound III is 1.6 μB. Complexes I and III are studied by EPR and IR spectroscopy. Original Russian Text ? T.E. Kokina, L.A. Glinskaya, R.F. Klevtsova, E.G. Boguslavskii, L.A. Sheludyakova, S.N. Bisyaev, A.V. Tkachev, S.V. Larionov, 2009, published in Koordinatsionnaya Khimiya, 2009, Vol. 35, No. 3, pp. 202–211.     

Kinetics of the Reactions between [(RS)2Fe(µ-S)2M(µ-S)2Fe(SR)2] n− (M = Mo, R = Ph, n = 2; M = V, R = Et, n = 3) and [Fe(SR)4]2−: Key Steps in the Assembly of Cuboidal Fe—S-based Clusters

The reaction of [S₂Mo(μ-S)₂Fe(SPh)₂]²⁻ with [Fe(SPh)₄]²⁻ produces the dicuboidal cluster [{MoFe₃S₄(SPh)₃}₂(μ-(SPh)₃]³⁻ in a three stage process studied by ¹H-n.m.r. spectroscopy and stopped-flow spectrophotometry. The initial stage involves the formation of the linear trinuclear [(PhS)₂Fe(μ-S)₂Mo(μ-S)₂Fe(SPh)₂]²⁻ and the kinetics indicate an equilibrium reaction (k₁^Mo = 2.5±0.3x 10² dm³ mol⁻¹ s⁻¹, k₋₁^Mo = 0.8±0.1 s⁻¹). The second stage involves the reduction of [(PhS)₂Fe(μ-S)₂Mo(μ-S)₂Fe(SPh)₂]²⁻ by [Fe(SPh)₄]²⁻ to form [(PhS)₂Fe(μ-S)₂Mo(μ-S)₂Fe(SPh)₂]³⁻ which subsequently rearranges to form the voided cuboidal [MoFe₂S₄(SPh)₃]²⁻. The kinetics of the second stage exhibits a simple first order dependence on the concentrations of both [(PhS)₂Fe(μ-S)₂Mo(μ-S)₂Fe(SPh)₂]³⁻ and [Fe(SPh)₄]²⁻ (k₂^Mo = 25 ± 2 dm³ mol⁻¹ s⁻¹). The Kinetics of the third stage have not been studied but must involve incorporation of the final Fe and formation of the dicuboidal [{MoFe₃S₄(SPh)₃}₂(μ-SPh)₃]³⁻. The kinetics of the reaction between [(EtS)₂Fe(μ-S)₂V(μ-S)₂Fe(SEt)₂]³⁻ and [Fe(SEt)₄]²⁻ to form [{VFe₃S₄(SEt)₃}₂(μ-SEt)₃]³⁻ have also been studied. An important difference between this reaction and the formation of the analogous [{MoFe₃S₄(SPh)₃}₂(μ-SPh)₃]³⁻ is that the formation of [{MoFe₃S₄(SPh)₃}₂(μ-SPh)₃]³⁻ from [(PhS)₂Fe(μ-S)₂Mo(μ-S)₂Fe(SPh)₂]²⁻ involves a change in the redox state of the cluster, whilst the formation of [{VFe₃S₄(SEt)₃}₂(μ-SEt)₃]³⁻ from [(EtS)₂Fe(μ-S)₂V(μ-S)₂Fe(SEt)₂]³⁻ requires no change in redox state. The reaction between [(EtS)₂Fe(μ-S)₂V(μ-S)₂Fe(SEt)₂]³⁻ and [Fe(SEt)₄]²⁻ involves two stages. The kinetics of the faster phase is associated with a rate law analogous to that observed for the reaction between [(PhS)₂Fe(μ-S)₂Mo(μ-S)₂ Fe(SPh)₂]²⁻ with [Fe(SPh)₄]²⁻: a first order dependence on the concentrations of [(EtS)₂Fe(μ-S)₂V(μ-S)₂Fe(SEt)₂]³⁻ and [Fe(SEt)₄]²⁻ (k₂^V = 1.1±0.1 x 10³ dm³ mol⁻¹ s⁻¹. This observation indicates that whilst there is no change in redox state between [(EtS)₂Fe(μ-S)₂V(μ-S)₂Fe(SEt)₂]³⁻ and [{VFe₃S₄(SEt)₃}₂(μ-SEt)₃]³⁻, reduction is necessary to catalyse the conversion of the linear [(EtS)₂Fe(μ-S)₂V(μ-S)₂Fe(SEt)₂]³⁻ into the voided cuboidal [VFe₂S₄(SEt)₃]³⁻. The results of the studies reported in this paper together with those on other putative reactions involved in the assembly of cuboidal clusters, have been combined to present a scheme of the mechanism of cuboidal cluster assembly. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Synthesis,crystal structures,and antibacterial activities of two copper(II) complexes derived from 1-[(2-morpholin-4-ylethylimino)methyl]-naphthalen-2-ol

A trinuclear complex, [Cu(Cu(μ-Br)₂L)₂], and a dinuclear complex, [Cu₂(μ-Cl)₂L₂], have been synthesized with the tridentate Schiff base 1-[(2-morpholin-4-ylethylimino)methyl]-naphthalen-2-ol (HL), derived from 2-hydroxy-1-naphthyaldehyde and 4-(2-aminoethyl)morpholine. Both complexes have been characterized by physicochemical and spectroscopic methods. [Cu(Cu(μ-Br)₂L)₂] is a centrosymmetric bromide and phenolate oxygen-bridged trinuclear compound, while complex [Cu₂(μ-Cl)₂L₂] is a centrosymmetric-chloride-bridged dinuclear compound. The central Cu(II) atom in [Cu(Cu(μ-Br)₂L)₂] is six-coordinated in an octahedral coordination, while other Cu(II) atoms in both complexes are five-coordinated in square-pyramidal coordinations. Both complexes and HL were tested in vitro for their antibacterial activities.     

Structure of complex salts [Co(NH3)6][Rh(NO2)6] and [Co(NH3)6][(NO2)3Rh(μ-NO2)1+x(μ-OH)2?xRh(NO2)3]·(2-x)(H2O), x = 0.17

The structures of two salts [Co(NH₃)₆][Rh(NO₂)₆] (I) and [Co(NH₃)₆][(NO₂)₃Rh(μ-NO₂)_1+x (μ-OH)_2−x Rh(NO₂)₃]·(2−x)(H₂O), x = 0.17 (II) are solved. Single crystals of the salts are obtained by the counter diffusion method through the gel of aqueous solutions of [Co(NH₃)₆]Cl₃ and Na₃[Rh(NO₂)₆]. The structure of [Co(NH₃)₆][Rh(NO₂)₆] is consistent with the diffraction data for a polycrystalline sample of poorly soluble fine salt formed in the exchange reaction between aqueous solutions of [Co(NH₃)₆]Cl₃ and Na₃[Rh(NO₂)₆]. The structure of [Co(NH₃)₆][(NO₂)₃Rh(μ-NO₂)_1+x (μ-OH)_2−x Rh(NO₂)₃]·(2−x)(H₂O), x = 0.17 exhibits the stabilizing effect of a large cation in the formation of novel, unknown previously coordination ions: [(NO₂)₃Rh(μ-NO₂)(μ-OH)₂Rh(NO₂)₃]³⁻ and [(NO₂)₃Rh(μ-NO₂)₂(μ-OH)Rh(NO₂)₃]³⁻.     

Electrospray Ionization Based Methods for the Generation of Polynuclear Oxo- and Hydroxo Group 6 Anions in the Gas-Phase

Electrospray ionization (ESI) of the Lindqvist (n-Bu₄N)₂[M₆O₁₉] (M = Mo, W) polyoxometalates provides a straightforward entry for the generation of an assortment of oxo- and hydroxo anions in the gas-phase. In particular, the series of oxo dianions of general formula [(MO₃) _n O]²⁻ (n = 2–6; M = Mo, W), monoanions, namely [(MO₃) _n O]⁻ (n = 1, 2) and [(MO₃) _n ]⁻ (n = 1, 2), and the hydroxo [(MO₃) _n (OH)]⁻ (n = 1–6) species can be readily generated in the gas-phase upon varying the solvent composition as well as the ionisation conditions (typically the U_c cone voltage). Complementary tandem mass experiments (collision induced dissociation and ion–molecule reactions) are also used aimed to investigate the consecutive dissociation of these species and their intrinsic gas-phase reactivity towards methanol. Special emphasis is paid to some of the key factors of these group 6 anions related to the gas-phase activation of methanol, such as molecular composition, open vs closed shell electronic nature and cluster size.     

Synthesis and characterization of stable thiazolylazo anion radical complexes of ruthenium(II)

Two stable thiazolylazo anion radical complexes of ruthenium(II), [Ru(L1^•−)(Cl)(CO)(PPh₃)₂] (1) and [Ru(L2^•−)(Cl)(CO)(PPh₃)₂] (2) (where L1 = 2′-Thiazolylazo-2-imidazole and L2 = 4-(2′-Thiazolylazo)-1-n-hexadecyloxy-naphthalene), have been synthesized and characterized by spectroscopic and electrochemical techniques. The radical nature of the complexes has been confirmed from their room temperature magnetic moments and X-band ESR spectra. The radical complexes display a moderately intense (ε ~ 10⁴ M⁻¹ cm⁻¹) and relatively broad band in 430–460 nm region. In the microcrystalline state, complexes (1) and (2) display strong ESR signals at g = 1.951 and g = 1.988, respectively. In CH₂Cl₂ solution, complexes (1) and (2) show a quasireversible one-electron response near −0.64 and −0.59 V, respectively, versus Ag/AgCl due to the radical redox couple [Ru^II(L)(Cl)(CO)(PPh₃)₂]/[Ru^II (L^•−)(Cl)(CO)(PPh₃)₂].     

Thiolate-bridged Trinuclear Heterobimetallic Complexes [Cd(μ-SPh-4-Me)4{M(PPh3)2}2] (M?=?Cu, Ag) and [Sn(μ-SPh)6(AgPPh3)2]

Abstract  

Reaction of the [Me₄N]₂[Cd(SPh-4-Me)₄] with two equivalents of [M(PPh₃)₂NO₃] afforded the neutral linear trinuclear complexes [Cd(μ-SPh-4-Me)₄{M(PPh₃)₂}₂] (M = Cu 1, Ag 2) in which two [M(PPh₃)₂]⁺ fragments chelate with the opposite edges of a tetrahedral [Cd(SPh-4-Me)₄]²⁻ moiety via the sulfur atoms of the Me-4-PhS⁻ species. Treatment of [Sn(SPh)₄] with two equivalents of [Ag(PPh₃)₂NO₃] gave the neutral linear trinuclear complex [Sn(μ-SPh)₆(AgPPh₃)₂] (3) that is composed of a central distorted SnS₆ octahedron sharing two opposite planes with two slightly distorted AgS₃P tetrahedrons. Complexes 2 and 3 are air and optically stable. Their nonlinear optical absorption and refraction were investigated under the same conditions. The nonlinear optical absorption and refraction of complex 2 were determined to be α ₂ = 3.11 × 10⁻¹¹ m/W and n ₂ = 4.15 × 10⁻¹² esu, respectively. The nonlinear optical absorption and refraction of complex 3 were determined to be α ₂ = 8.36 × 10⁻¹¹ m/W and n ₂ = 1.47 × 10⁻¹¹ esu, respectively.     

Kinetics of oxidation of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-ethylenebis(isonitrosoacetylacetoneimine)copper(II) by peroxydisulfate in aqueous acidic solutions

Peroxydisulfate (PDS) oxidizes N,N′-ethylenebis(isonitrosoacetyleacetoneimine)copper(II) complex, Cu^IIL, to the corresponding copper(III) complex, [Cu^IIIL]⁺. The kinetic runs were performed in the presence of EDTA to scavenge any trace metal impurities. The kinetics of the reaction at constant pH, ionic strength, and temperature obeys the rate law d[Cu^IIIL]/dt = 2k ₂[Cu^IIL][S₂O₈ ²⁻] with k ₂ having a value of (8.85 ± 0.32) × 10⁻² M⁻¹ s⁻¹ at μ = 0.30 M and T = 25.0 °C. The rate constant k ₂ is not affected by variation of pH over the range 3.60–5.20. The second order rate constant is also unaffected by changing ionic strength. The values of k _obs were determined over the temperature 25.0–40.0 °C range. The enthalpy of activation, ∆H*, and entropy of activation, ∆S*, have been calculated as 34.9 ± 0.5 kJ mol⁻¹ and −173.3 ± 11.4 J K⁻¹ mol⁻¹, respectively. The kinetics of this reaction, as far as we know, is the first evidence that copper(III) is the likely reactive species in copper catalyzed PDS oxidation reactions.     

A new cobalt complex of 1-decyl-1<Emphasis Type="Italic">H</Emphasis>-benzo[<Emphasis Type="Italic">d</Emphasis>]imidazole: synthesis,characterization and electrocatalysis

The present work reports on the synthesis, characterization and performance of a new cobalt(II) complex, [Co(C₁₀H₂₁-bim)₂(SCN)₂] (bim = benzimidazole) as electrocatalyst for trichloroacetic acid and bromate reduction. Its structure was characterized by X-ray crystallography, IR spectroscopy and elemental analysis. The cobalt atom adopts a distorted tetrahedral geometry by coordinating to four nitrogen atoms from two thiocyanates and two 1-decyl-1H-benzo[d]imidazole ligands. The electrochemical behavior and electrocatalysis of the title complex bulk-modified carbon paste electrode (Co-CPE) have been studied by cyclic voltammetry. The Co-CPE shows good electrocatalytic activities toward the reduction of trichloroacetic acid and bromate. The detection limit and the sensitivity are 0.02 μM, 34.63 μA μM⁻¹ for trichloroacetic acid detection, and 0.03 μM, 78.92 μA μM⁻¹ for bromate detection, respectively. This modified electrode shows good reproducibility, high stability, low detection limit, technical simplicity and possibility of rapid preparation, which is important for practical application.     

Synthesis, structure, and properties of a binuclear Fe(III) complex with N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine

Mannich reaction of 2-Amino propanol, 2-tert-butyl-4-methylphenol, and formaldehyde in the ratio of 1:2:2 provides a new compound, N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L), which has been characterized by X-ray crystallography and elemental analysis. In the presence of Et₃N, the reaction of H₃L and FeCl₃·6H₂O gives a dinuclear Fe(III) complex [Fe₂L₂] 1, which has been characterized by X-ray crystallography, magnetic measurement, and cyclic voltammetry. The value of μ_eff at room temperature (5.97 μ_B) is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ZS(S + 1)]^1/2], indicating there are strong coupling interactions between Fe³⁺ ions. The magnetic behavior of 1 denotes the occurrence of intramolecular antiferromagnetic interactions (J = −13.35 cm⁻¹ ). CV of 1 reveals two reversible waves at 0.433 and 1.227 V versus AgCl/Ag, which can be ascribed to the successive redox coupling of Fe^IIFe^II/Fe^IIIFe^II and Fe^IIIFe^II/Fe^IIIFe^III, respectively.     

Copper complexes of 1-[(2-carboxyethyl)benzene]-3-[2-pyridine]triazene

The triazenide, 1-[(2-carboxyethyl)benzene]-3-[2-pyridine]triazene (HL), has been synthesized. In the presence of Et₃N, the reaction of HL with Cu(OAc)₂·H₂O or CuCl₂·2H₂O gives the tetranuclear copper(II) complexes {Cu₄(L)₂(μ₂-OH)₂(OAc)₄} 1 and {Cu₄L₄(μ₄-O)Cl₂} 2, respectively. The X-ray crystal structures of both complexes have been obtained. Magnetic studies indicate significant antiferromagnetic coupling between the copper(II) centers for both complexes, with coupling constants (J) of −493.4 cm⁻¹ for 1 and −165 cm⁻¹ for 2.     

Synthesis, electrochemistry, thin-layer UV-vis and fluorescence spectroelectrochemistry of a new salicylaldimine ligand and its copper complex

The new asymmetric, fluorescent Schiff-base ligand, N-(pyrene)-salicylaldimine (L), and its copper complex having an ONNO donor set, [Cu(L) ₂ ], were synthesized and characterized using elemental analysis, IR, UV-vis, ¹H and ¹³C-NMR spectroscopies. Their electrochemical and spectroelectrochemical behaviors were investigated in a detail by using cyclic voltammetry (CV), square wave voltammetry (SWV), in-situ UV-vis, and fluorescence spectroelectrochemistry. The formation of the complex was monitored by the in-situ fluorescence technique based on the quenching of the fluorescence-probe ligand. Electrochemical studies showed that L exhibits a single irreversible reduction process. However, the SWV indicated that this process was not totally irreversible in the time scale of the measurement. The cathodic peak potential of the reduction process occurred at E _pc = −1.35 V vs Ag/AgCl (scan rate: 0.025 Vs⁻¹). On the other hand, [Cu(L) ₂ ] showed one quasi-reversible one-electron reduction process in the scan rates of 0.025–0.50 Vs⁻¹, which was assigned to metal-based one-electron process; [Cu(2+)(L)₂] + e⁻ → [Cu(+)(L)₂]⁻. The value of half-wave potential (E _1/2) of the reduction process was −0.54 V vs Ag/AgCl (scan rate: 0.025 Vs⁻¹). The time-resolved spectra showed, when the potential (E _app = −1.60 V) was applied in a thin-layer cell, that the main and shoulder bands of (L) at 385, 336, and 407 nm almost disappeared and a new band at 443 nm with a shoulder formed during the reduction process. No change was observed on the final spectrum of the totally reduced ligand for long period under nitrogen atmosphere, which indicated that the singly reduced species remained stable and was not accompanied by a chemical reaction in the time scale of the spectroelectrochemical measurement. The spectral changes during the reduction process of [Cu(L) ₂ ] confirmed the metal-centered reduction process. The fluorescence intensity of L decreased during the reduction process in the thin-layer cell, as result of the perturbation of the conjugated system of the reduced species.     

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.