Copper(I)-dioxygen reactivity of [(L)Cu(I)](+) (L = tris(2-pyridylmethyl)amine): kinetic/thermodynamic and spectroscopic studies concerning the formation of Cu-O2 and Cu2-O2 adducts as a function of solvent medium and 4-pyridyl ligand substituent variations

The kinetic and thermodynamic behavior of O(2)-binding to Cu(I) complexes can provide fundamental understanding of copper(I)/dioxygen chemistry, which is of interest in chemical and biological systems. Here we report stopped-flow kinetic investigations of the oxygenation reactions of a series of tetradentate copper(I) complexes [(L(R))Cu(I)(MeCN)](+) (1(R), R=H, Me, tBu, MeO, Me(2)N) in propionitrile (EtCN), tetrahydrofuran (THF), and acetone. The syntheses of 4-pyridyl substituted tris(2-pyridylmethyl)amine ligands (L(R)) and copper(I) complexes are detailed. Variations of ligand electronic properties are manifested in the electrochemistry of 1(R) and nu(CO) of [(L(R))Cu(I)-CO](+) complexes. The kinetic studies in EtCN and THF show that the O(2)-reactions of 1(R) follow the reaction mechanism established for oxygenation of 1(H) in EtCN (J. Am. Chem. Soc. 1993, 115, 9506), involving reversible formation (k(1)/k(-1)) of [(L(R))Cu(II)(O(2-))](+) (2(R)), which further reacts (k(2)/k(-2)) with 1(R) to form the 2:1 Cu(2)O(2) complex [[(L(R))Cu(II)](2)(O(2)(2-))](2+) (3(R)). In EtCN, the rate constants for formation of 2(R) (k(1)) are not dramatically affected by the ligand electronic variations. For R = Me and tBu, the kinetic and thermodynamic parameters are very similar to those of the parent complex (1(H)); e.g., k(1) is in the range 1.2 x 10(4) to 3.1 x 10(4) M(-1) s(-1) at 183 K. With the stronger donors R = MeO and Me(2)N, more significant effects were observed, with the expected increase in thermodynamic stability of resultant 2(R) and 3(R) complexes, and decreased dissociation rates. The modest ligand electronic effects manifested in EtCN are due to the competitive binding of solvent and dioxygen to the copper centers. In THF, a weakly coordinating solvent, the formation rate for 2(H) is much faster (>/=100 times) than that in EtCN, and the thermodynamic stabilities of both the 1:1 (K(1)) and 2:1 (beta = K(1)K(2)) copper-dioxygen species are much higher than those in EtCN (e.g., for 2(H), deltaH(o) (K(1))=-41 kJ mol(-1) in THF versus -29.8 kJ mol(-1) in EtCN; for 3(H), deltaH(o) (beta)=-94 kJ mol(-1) in THF versus -77 kJ mol(-1) in EtCN). In addition, a more significant ligand electronic effect is seen for the oxygenation reactions of 1(MeO) in THF compared to that in EtCN; the thermal stability of superoxo- and peroxocopper complexes are considerably enhanced using L(MeO) compared to L(H). In acetone as solvent, a different reaction mechanism involving dimeric copper(I) species [(L(R))(2)Cu(I)(2)](2+) is proposed for the oxygenation reactions, supported by kinetic analyses, electrical conductivity measurements, and variable-temperature NMR spectroscopic studies. The present study is the first systematic study investigating both solvent medium and ligand electronic effects in reactions forming copper-dioxygen adducts.     

Synthesis and characterization of Cu(2)(I,I), Cu(2)(I,II), and Cu(2)(II,II) compounds supported by two phthalazine-based ligands: influence of a hydrophobic pocket

The copper coordination chemistry of two phthalazine-based ligands of differing steric bulk was investigated. A family of dinuclear complexes were prepared from reactions of [Cu(2)(bdptz)(MeCN)(2)](OTf)(2), 1(OTf)(2), where bdptz = 1,4-bis(2,2'-dipyridylmethyl)phthalazine. Treatment of 1(OTf)(2) with NaO(2)CCH(3) afforded the class I mixed-valent compound [Cu(2)(bdptz)(2)](OTf)(3), 2(OTf)(3), by disproportionation of Cu(I). Compound 2(OTf)(3) displays an electron paramagnetic resonance spectrum, with g( parallel ) = 2.25 (A( parallel ) = 169 G) and g( perpendicular ) = 2.06, and exhibits a reversible redox wave at -452 mV versus Cp(2)Fe(+)/Cp(2)Fe. The complex [Cu(2)(bdptz)(micro-OH)(MeCN)(2)](OTf)(3), 3(OTf)(3), was prepared by chemical oxidation of 1 with AgOTf, and exposure of 1 to dioxygen afforded [Cu(2)(bdptz)(micro-OH)(2)](2)(OTs)(4), 4(OTs)(4), which can also be obtained directly from [Cu(H(2)O)(6)](OTs)(2). In compound [Cu(2)(bdptz)(micro-vpy)](OTf)(2), 5(OTf)(2), where vpy = 2-vinylpyridine, the vpy ligand bridges the two Cu(I) centers by using both its pyridine nitrogen and the olefin as donor functionalities. The sterically hindered compounds [Cu(2)(Ph(4)bdptz)(MeCN)(2)](OTf)(2), 6(OTf)(2), and [Cu(2)(Ph(4)bdptz)(micro-O(2)CCH(3))](OTf), 7(OTf), were also synthesized, where Ph(4)bdptz = 1,4-bis[bis(6-phenyl-2-pyridyl)methyl]phthalazine. Complexes 1-7 were characterized structurally by X-ray crystallography. In 6 and 7, the four phenyl rings form a hydrophobic pocket that houses the acetonitrile and acetate ligands. Complex 6 displays two reversible redox waves with E(1/2) values of +41 and +516 mV versus Cp(2)Fe(+)/Cp(2)Fe. Analysis of oxygenated solutions of 6 by electrospray ionization mass spectrometry reveals probable aromatic hydroxylation of the Ph(4)bdptz ligand. The different chemical and electrochemical behavior of 1 versus 6 highlights the influence of a hydrophobic binding pocket on the stability and reactivity of the dicopper(I) centers.     

Novel aggregation of [Ni(thiolato)2(amine)2]-type square planes assisted by silver(I) ions

Treatment of [Ni(L)][L =((-)SCH(2)CH(2)NH[double bond, length as m-dash]C(CH(3))-)(2)] with Ag(+) in water gave a pinwheel-like S-bridged Ni(II)(3)Ag(I)(2) structure in [Ag(2)[Ni(L)](3)](2+), which further reacted with [Ni(L)] to produce a Ni(II)(4)Ag(I)(2) structure in [Ag(2)[Ni(L)](4)](2+) and a Ni(II)(7)Ag(I)(4) structure in [Ag(4)[Ni(L)](7)](4+).     

Electrospray ionization mass spectrometric study of Cu(I) and Cu(II) bipyridine complexes employed in atom transfer radical polymerization

We report an electrospray ionization mass spectrometric study of Cu(I) and Cu(II) bipyridine complexes employed in atom transfer radical polymerization. Mass spectra of Cu(I)Br complexed with 2 equiv. of 4,4'-di(5-nonyl)-2,2'-bipyridine (dNbpy) in toluene, methyl acrylate or styrene showed the presence of [Cu(I)(dNbpy)(2)](+) cation and [Cu(I)Br(2)](-) anion. For the Cu(II)Br(2)/2dNbpy system, [Cu(II)(dNbpy)(2)Br](+), [Cu(II)(dNbpy)Br](+), [Cu(I)Br(2)](-), [Cu(II)Br(3)](-) and [Cu(II)(dNbpy)Br(3)](-) species were observed. In addition, for mixed Cu(I)Br/2dNbpy and Cu(II)Br(2)/2dNbpy systems, the negative ion mode showed only the presence of [Cu(I)Br(2)](-) anions, which are potentially formed through halogen exchange between [Cu(II)Br(3)](-) and [Cu(I)(dNbpy)(2)](+). Copyright 2000 John Wiley & Sons, Ltd.     

Modulation of metal-metal separations in a series of Ag(I) and intensely blue photoluminescent Cu(I) NHC-bridged triangular clusters

A series of picolyl-substituted NHC-bridged triangular complexes of Ag(I) and Cu(I) were synthesized upon reaction of the corresponding ligand precursors, [Him(CH(2)py)(2)]BF(4) (1a), [Him(CH(2)py-3,4-(OMe)(2))(2)]BF(4) (1b), [Him(CH(2)py-3,5-Me(2)-4-OMe)(2)]BF(4) (1c), [Him(CH(2)py-6-COOMe)(2)]BF(4) (1d), and [H(S)im(CH(2)py)(2)]BF(4) (1e), with Ag(2)O and Cu(2)O, respectively. Complexes [Cu(3)(im(CH(2)py)(2))(3)](BF(4))(3) (2a), [Cu(3)(im(CH(2)py-3,4-(OMe)(2))(2))(3)](BF(4))(3) (2b), [Cu(3)(im(CH(2)py-3,5-Me(2)-4-OMe)(2))(3)](BF(4))(3), (2c), [Ag(3)(im(CH(2)py-3,4-(OMe)(2))(2))(3)](BF(4))(3), (3b), [Ag(3)(im(CH(2)py-3,5-Me(2)-4-OMe)(2))(3)](BF(4))(3) (3c), [Ag(3)(im(CH(2)py-6-COOMe)(2))(3)](BF(4))(3) (3d), and [Ag(3)((S)im(CH(2)py)(2))(3)](BF(4))(3) (3e) were easily prepared by this method. Complex 2e, [Cu(3)((S)im(CH(2)py)(2))(3)](BF(4))(3), was synthesized by a carbene-transfer reaction of 3e, [Ag(3)((S)im(CH(2)py)(2))(3)](BF(4))(3), with CuCl in acetonitrile. The ligand precursor 1d did not react with Cu(2)O. All complexes were fully characterized by NMR, UV-vis, and luminescence spectroscopies and high-resolution mass spectrometry. Complexes 2a-2c, 2e, and 3b-3e were additionally characterized by single-crystal X-ray diffraction. Each metal complex contains a nearly equilateral triangular M(3) core wrapped by three bridging NHC ligands. In 2a-2c and 2e, the Cu-Cu separations are short and range from 2.4907 to 2.5150 ?. In the corresponding Ag(I) system, the metal-metal separations range from 2.7226 to 2.8624 ?. The Cu(I)-containing species are intensely blue photoluminescent at room temperature both in solution and in the solid state. Upon UV excitation in CH(3)CN, complexes 2a-2c and 2e emit at 459, 427, 429, and 441 nm, whereas in the solid state, these bands move to 433, 429, 432, and 440 nm, respectively. As demonstrated by (1)H NMR spectroscopy, complexes 3b-3e are dynamic in solution and undergo a ligand dissociation process. Complexes 3b-3e are weakly photoemissive in the solid state.     

Reaction behaviour of dinuclear copper(I) complexes with m-xylyl-based ligands towards dioxygen

Intramolecular ligand hydroxylation was observed during the reactions of dioxygen with the dicopper(I) complexes of the ligands L(1)(L(1)=alpha,alpha'-bis[(2-pyridylethyl)amino]-m-xylene) and L(3)(L(3)=alpha, alpha'-bis[N-(2-pyridylethyl)-N-(2-pyridylmethyl)amino]-m-xylene). The dinuclear copper(I) complex [Cu(2)L(3)](ClO(4))(2) and the dicopper(II) complex [Cu(2)(L(1)-O)(OH)(ClO(4))]ClO(4) were characterized by single-crystal X-ray structure analysis. Furthermore, phenolate-bridged complexes were synthesized with the ligand L(2)-OH (structurally characterized [Cu(2)(L(2)-O)Cl(3)] with L(2)=alpha, alpha'-bis[N-methyl-N-(2-pyridylethyl)amino]-m-xylene; synthesized from the reaction between [Cu(2)(L(2)-O)(OH)](ClO(4))(2) and Cl(-)) and Me-L(3)-OH: [Cu(2)(Me-L(3)-O)(mu-X)](ClO(4))(2)xnH(2)O (Me-L(3)-OH = 2,6-bis[N-(2-pyridylethyl)-N-(2-pyridylmethyl)amino]-4-methylphenol and X = C(3)H(3)N(2)(-)(prz), MeCO(2)(-) and N(3)(-)). The magnetochemical characteristics of compounds were determined by temperature-dependent magnetic studies, revealing their antiferromagnetic behaviour [-2J(in cm(-1)) values: -92, -86 and -88; -374].     

A mechanistic study of the reaction between a diiron(II) complex [FeII(2)(mu-OH)2(6-Me3-TPA)2](2+) and O2 to form a diiron(III) peroxo complex

A kinetic study of the reaction between a diiron(II) complex [Fe(II)(2)(mu-OH)(2)(6-Me(3)-TPA)(2)](2+) 1, where 6-Me(3)-TPA = tris(6-methyl-2-pyridylmethyl)amine, and dioxygen is presented. A diiron(III) peroxo complex [Fe(III)(2)(mu-O)(mu-O(2))(6-Me(3)-TPA)(2)](2+) 2 forms quantitatively in dichloromethane at temperatures from -80 to -40 degrees C. The reaction is first order in [Fe(II)(2)] and [O(2)], with the activation parameters DeltaH(double dagger) = 17 +/- 2 kJ mol(-1) and DeltaS(double dagger) = -175 +/- 20 J mol(-1) K(-1). The reaction rate is not significantly influenced by the addition of H(2)O or D(2)O. The reaction proceeds faster in more polar solvents (acetone and acetonitrile), but the yield of 2 is not quantitative in these solvents. Complex 1 reacts with NO at a rate about 10(3) faster than with O(2). The mechanistic analysis suggests an associative rate-limiting step for the oxygenation of 1, similar to that for stearoyl-ACP Delta(9)-desaturase, but distinct from the probable dissociative pathway of methane monoxygenase. An eta(1)-superoxo Fe(II)Fe(III) species is a likely steady-state intermediate during the oxygenation of complex 1.     

Polynuclear and mixed-ligand mononuclear Cu(I) complexes with N-thiophosphorylated thioureas and 1,10-phenanthroline or PPh3

Deprotonation of the N-thiophosphorylated thioureas RC(S)NHP(S)(OiPr)(2) (R = Me(2)N, HL(I); iPrNH, HL(II); 2,6-Me(2)C(6)H(3)NH, HL(III), 2,4,6-Me(3)C(6)H(2)NH, HL(IV), aza-15-crown-5, HL(V)) and reaction with CuI or Cu(NO(3))(2) in aqueous EtOH leads to the polynuclear complexes [Cu(4)(L(I)-S,S')(4)], [Cu(8)(L(II)-S,S')(8)], and [Cu(3)(L(III-V)-S,S')(3)]. The structures of these compounds were investigated by IR, (1)H, (31)P{(1)H} NMR, UV-vis spectroscopy and elemental analyses. The crystal structures of [Cu(4)L(I)(4)], [Cu(8)L(II)(8)], [Cu(3)L(III,IV)(3)] were determined by single-crystal X-ray diffraction. Reaction of the deprotonated ligands (L(I-V))(-) with a mixture of CuI and 1,10-phenanthroline (phen) or PPh(3) leads to the mixed-ligand mononuclear complexes [Cu(phen)L(I-V)], [Cu(PPh(3))L(I-V)] or [Cu(PPh(3))(2)L(I-V)]. The same mixed-ligand complexes were obtained from the reaction of [Cu(4)L(I)(4)], [Cu(8)L(II)(8)], [Cu(3)L(III-V)(3)] with phen or PPh(3).     

Characterization and electrochemical properties of molecular icosanuclear and bidimensional hexanuclear Cu(II) azido polyoxometalates

Two new Cu(II) azido polyoxometalates compounds have been synthesized, and their structures were determined by X-ray crystallography. The compound Na(14)[SiW(9)O(34)Cu(3)(N(3))(2)(OH)(H(2)O)](2) x 24H(2)O (1) is built from two [SiW(9)O(34)Cu(3)(mu(1,1,3)-N(3))(2)(mu-OH)(H(2)O)](7-) subunits where the copper centers, connected by two azido ligands and one hydroxo group, form a nearly equilateral triangle. The two subunits are related by an inversion center and connected via the two mu(1,1,3)-N(3) ligands in an end-to-end fashion, affording a hexanuclear Cu(II) cluster. Linkage of these fragments via Cu-O=W bonds leads to a bidimensional arrangement of the polyoxometalate units. The complex LiK(14)Na(9)[P(8)W(48)O(184)Cu(20)(N(3))(6)(OH)(18)] x 60H(2)O (2) consists of two {Cu(5)(OH)(4)}(6+) and two {Cu(5)(OH)(2)(mu(1,1,3,3)-N(3))}(7+) subunits connected via four mu-OH and four mu(1,1)-N(3) additional ligands, the 20 copper centers being encapsulated in the [P(8)W(48)O(184)](40-) crown polyoxotungstate ligand. 1 represents the first multidimensional compound based on azido polyoxometalate (POM) units, and 2 represents by far the largest azido POM complex isolated to date. Magnetic measurements revealed an overall antiferromagnetic behavior for both compounds. Nevertheless, the study of the variation of the magnetization with the applied field indicates that 1 possesses a triplet ground state, which can be attributed to weak ferromagnetic interaction between the S = 1/2 triangular subunits. The stability of 1 and 2 evidenced by UV-vis spectroscopy and gel filtration chromatography, in particular at pH 5, has allowed a detailed study of their redox and electrocatalytic properties. For both compounds, the stability of the Cu(II)/Cu(I) couple is remarkable compared with the observations made in other Cu(II)-substituted POMs. Electrochemical quartz crystal microbalance measurements clearly demonstrate that the formation of the Cu(I) species occurs neatly without the formation of Cu(0). The accumulation of such Cu(II) centers within the complexes is a favorable condition to envision applications involving several electrons. The electrocatalytic reduction of dioxygen and hydrogen peroxide was achieved efficiently and has shown that the reactivity increases with the nuclearity and/or the Cu/W ratio of the POM complex. The dioxygen reduction is an overall four-electron process with water as the final product. Finally, the reduction of the W centers triggers a strong electrocatalysis of solvent reduction.     

Modeling Tyrosinase Monooxygenase Activity. Spectroscopic and Magnetic Investigations of Products Due to Reactions between Copper(I) Complexes of Xylyl-Based Dinucleating Ligands and Dioxygen: Aromatic Ring Hydroxylation and Irreversible Oxidation Products

A full account of a chemical system possessing features that mimic the reactivity aspects of tyrosinase is presented. Using dinucleating ligands with a m-xylyl spacer three new dicopper(I) complexes have been synthesized and their reactivity with dioxygen investigated. The six-membered chelate ring forming ligands provide only two nitrogen coordinations to each copper. The complexes [Cu(I)(2)L(CH(3)CN)(2)]X(2) (X = ClO(4)(-) (1a), SbF(6)(-) (1b)) and [Cu(I)(2)(L-NO(2))(CH(3)CN)(2)][SbF(6)](2) (1c) [L = alpha,alpha'-bis[N-methyl-N-(2-pyridylethyl)amino]-m-xylene; L-NO(2) = para-nitro derivative of L] have been characterized by IR and (1)H NMR spectroscopy. The reaction of O(2) with 1a-c in CH(2)Cl(2) or THF is instantaneous and causes stoichiometric xylyl hydroxylation reactions producing phenol products. Thus 1a produces phenoxo-/hydroxo-bridged product [Cu(II)(2)(L-O)(OH)][ClO(4)](2) (2a). The existence of putative peroxo-dicopper(II) species could not be detected even at -80 degrees C. A trend is observed for the extent of aromatic ring hydroxylation (298 K): CH(3)CN approximately DMF > CH(3)OH > CH(2)Cl(2). Cyclic voltammetric experiment of 1a in DMF reveals an appreciably low redox potential (E(1/2) = -0.26 V vs SCE) for the Cu(II)(2)/Cu(I)(2) redox process. Variable-temperature (25-300 K) magnetic susceptibility measurements establish that the copper(II) centers in 2a and the dihydroxo-bridged complex [Cu(II)(2)L'(OH)(2)][ClO(4)](2) (2b) [formed due to an impurity (L') present during the synthesis of L following Method A; L' = bis[alpha,alpha'-bis(N-methyl-N-(2-pyridylethyl)amino)-m-xylene]methylamine] are antiferromagnetically coupled, with 2a considerably more coupled than 2b. Reaction of 1a with O(2) in CH(2)Cl(2) (298 K) produces an additional unhydroxylated product of composition [Cu(II)(2)L(OH)(OH(2))][ClO(4)](3).2H(2)O.0.5HCl (3a). In agreement with its proposed hydroxo-/aquo-bridged structure, 3a is weakly antiferromagnetically coupled. In CH(3)CN solution, 3a rearranges to generate a doubly hydroxo-bridged species [Cu(II)(2)L(OH)(2)](2+). Using a solution-generated dicopper(I) complex of a closely similar ligand (L' ') providing five-membered chelate ring, the reactivity toward dioxygen was also investigated. It produces only an irreversibly oxidized product of composition Cu(II)(2)L' '(OH)(ClO(4))(3)(H(2)O)(2) (3b) (L' ' = alpha,alpha'-bis[N-methyl-N-(2-pyridylmethyl)amino]-m-xylene). For 3b the copper(II) centers are almost uncoupled.     

Cellular delivery of pyrenyl-arene ruthenium complexes by a water-soluble arene ruthenium metalla-cage

Three pyrenyl-arene ruthenium complexes (M(1)-M(3)) of the general formula [Ru(η(6)-arene-pyrenyl)Cl(2)(pta)] (pta = 1,3,5-triaza-7-phosphaadamantane) have been synthesised and characterised. Prior to the coordination to ruthenium, pyrene was connected to the arene ligand via an alkane chain containing different functional groups: ester (L(1)), ether (L(2)) and amide (L(3)), respectively. Furthermore, the pyrenyl moieties of the M(n) complexes were encapsulated within the hydrophobic cavity of the water soluble metalla-cage, [Ru(6)(η(6)-p-cymene)(6)(tpt)(2)(donq)(3)](6+) (tpt = 2,4,6-tri-(pyridin-4-yl)-1,3,5-triazine; donq = 5,8-dioxydo-1,4-naphthoquinonato), while the arene ruthenium end was pointing out of the cage, thus giving rise to the corresponding host-guest systems [M(n)?Ru(6)(η(6)-p-cymene)(6)(tpt)(2)(donq)(3)](6+) ([M(n)?cage](6+)). The antitumor activity of the pyrenyl-arene ruthenium complexes (M(n)) and the corresponding host-guest systems [M(n)?cage][CF(3)SO(3)](6) were evaluated in vitro in different types of human cancer cell lines (A549, A2780, A2780cisR, Me300 and HeLa). Complex M(2), which contains an ether group within the alkane chain, demonstrated at least a 10 times higher cytotoxicity than the reference compound [Ru(η(6)-p-cymene)Cl(2)(pta)] (RAPTA-C). All host-guest systems [M(n)?cage](6+) showed good anticancer activity with IC(50) values ranging from 2 to 8 μM after 72 h exposure. The fluorescence of the pyrenyl moiety allowed the monitoring of the cellular uptake and revealed an increase of uptake by a factor two of the M(2) complex when encapsulated in the metalla-cage [Ru(6)(η(6)-p-cymene)(6)(tpt)(2)(donq)(3)](6+).     

A double arene hydroxylation mediated by dicopper(II)-hydroperoxide species

The dicopper(II) complex [Cu(2)(L)](4+) (L = alpha,alpha'-bis[bis[2-(1'-methyl-2'-benzimidazolyl)ethyl]amino]-m-xylene) reacts with hydrogen peroxide to give the dicopper(II)-hydroquinone complex in which the xylyl ring of the ligand has undergone a double hydroxylation reaction at ring positions 2 and 5. The dihydroxylated ligand 2,6-bis([bis[2-(3-methyl-1H-benzimidazol-2-yl)ethyl]amino]methyl)benzene-1,4-diol was isolated by decomposition of the product complex. The incorporation of two oxygen atoms from H(2)O(2) into the ligand was confirmed by isotope labeling studies using H(2)(18)O(2). The pathway of the unusual double hydroxylation was investigated by preparing the two isomeric phenolic derivatives of L, namely 3,5-bis([bis[2-(1-methyl-1H-benzimidazol-2-yl)ethyl]amino]methyl)phenol (6) and 2,6-bis([bis[2-(1-methyl-1H-benzimidazol-2-yl)ethyl]amino]methyl)phenol (7), carrying the hydroxyl group in one of the two positions where L is hydroxylated. The dicopper(II) complexes prepared with the new ligands 6 and 7 and containing bridging micro-phenoxo moieties are inactive in the hydroxylation. Though, the dicopper(II) complex 3 derived from 6 and containing a protonated phenol is rapidly hydroxylated by H(2)O(2) and represents the first product formed in the hydroxylation of [Cu(2)(L)](4+). Kinetic studies performed on the reactions of [Cu(2)(L)](4+) and 3 with H(2)O(2) show that the second hydroxylation is faster than the first one at room temperature (0.13 +/- 0.05 s(-1) vs 5.0(+/-0.1) x 10(-3) s(-1)) and both are intramolecular processes. However, the two reactions exhibit different activation parameters (Delta H++ = 39.1 +/- 0.9 kJ mol(-1) and Delta S++ = -115.7 +/- 2.4 J K(-1) mol(-1) for the first hydroxylation; Delta H++ = 77.8 +/- 1.6 kJ mol(-1) and Delta S++ = -14.0 +/- 0.4 J K(-1) mol(-1) for the second hydroxylation). By studying the reaction between [Cu(2)(L)](4+) and H(2)O(2) at low temperature, we were able to characterize the intermediate eta(1):eta(1)-hydroperoxodicopper(II) adduct active in the first hydroxylation step, [Cu(2)(L)(OOH)](3+) [lambda(max) = 342 (epsilon 12,000), 444 (epsilon 1200), and 610 nm (epsilon 800 M(-1)cm(-1)); broad EPR signal in frozen solution indicative of magnetically coupled Cu(II) centers].     

From discrete [Y(DMF)8][Cu4(mu3-I)2(mu-I)3I2] ion pairs to extended [Y(DMF)6(H2O)2][Cu7(mu4-I)3(mu3-I)2(mu-I)4(I)]1infinity and [Y(DMF)6(H2O)3][Cu(I)7Cu(II)2(mu3-I)8(mu-I)6]2infinity arrays by H-bond templating in a confined solvent-free environment

An ionic heterometallic species [Y(DMF)(8)][Cu(4)(micro(3)-I)(2)(micro-I)(3)I(2)](1) was isolated from a solution of CuI, NH(4)I and YI(3)(Pr(i)OH)(4) in DMF-isopropoxyethanol, and was converted in a confined environment by progressive substitution of the DMF ligands with water molecules first into a 1D zig-zag structure [Y(DMF)(6)(H(2)O)(2)][Cu(7)(micro(4)-I)(3)(micro(3)-I)(2)(micro-I)(4)(I)](1infinity)(2) and finally into a 2D sheet [Y(DMF)(6)(H(2)O)(3)][Cu(I)(7)Cu(II)(2)(micro(3)-I)(8)(micro-I)(6)](2infinity)(3) by H-bond templating.     

Identification of a copper(I) intermediate in the conversion of 1-aminocyclopropane carboxylic acid (ACC) into ethylene by Cu(II)-ACC complexes and hydrogen peroxide

Several Cu(II) complexes with ACC (=1-aminocyclopropane carboxylic acid) or AIB (=aminoisobutyric acid) were prepared using 2,2'-bipyridine, 1,10-phenanthroline, and 2-picolylamine ligands: [Cu(2,2'-bipyridine)(ACC)(H2O)](ClO4) (1a), [Cu(1,10-phenanthroline)(ACC)](ClO4) (2a), [Cu(2-picolylamine)(ACC)](ClO4) (3a), and [Cu(2,2'-bipyridine)(AIB)(H2O)](ClO4) (1b). All of the complexes were characterized by X-ray diffraction analysis. The Cu(II)-ACC complexes are able to convert the bound ACC moiety into ethylene in the presence of hydrogen peroxide, in an "ACC-oxidase-like" activity. A few equivalents of base are necessary to deprotonate H2O2 for optimum activity. The presence of dioxygen lowers the yield of ACC conversion into ethylene by the copper(II) complexes. During the course of the reaction of Cu(II)-ACC complexes with H2O2, brown species (EPR silent and lambda max approximately 435 nm) were detected and characterized as being the Cu(I)-ACC complexes that are obtained upon reduction of the corresponding Cu(II) complexes by the deprotonated form of hydrogen peroxide. The geometry of the Cu(I) species was optimized by DFT calculations that reveal a change from square-planar to tetrahedral geometry upon reduction of the copper ion, in accordance with the observed nonreversibility of the redox process. In situ prepared Cu(I)-ACC complexes were also reacted with hydrogen peroxide, and a high level of ethylene formation was obtained. We propose Cu(I)-OOH as a possible active species for the conversion of ACC into ethylene, the structure of which was examined by DFT calculation.     

Highly luminescent octanuclear Au(I)-Cu(I) clusters adopting two structural motifs: the effect of aliphatic alkynyl ligands

Reactions of the homoleptic (AuC(2)R)(n) precursors with stoichiometric amount of diphosphine ligand PPh(2)C(6)H(4)PPh(2) (P^P) and Cu(+) ions lead to an assembly of a new family of bimetallic clusters [Au(6)Cu(2)(C(2)R)(6)(P^P)(2)](2+) (type I; R=9-fluorenolyl (1), diphenylmethanolyl (2), 2,6-dimethyl-4-heptanolyl (3), 1-cyclohexanolyl (4), Cy (5), tBu (6)). In the case of R=1-cyclohexanolyl, a structurally different complex [Au(6)Cu(2)(C(2)C(6)H(11)O)(6)(P^P)(3)](2+) (7, type II) could be obtained by treatment of 4 with one equivalent of the diphosphine, while for R=isopropanolyl only the latter type of cluster [Au(6)Cu(2)(C(2)C(3)H(7)O)(6)(P^P)(3)](2+) (8) was detected. Steric bulkiness of the alkynyl ligands and O···H-O hydrogen bonding are suggested to play an important role in stabilizing the type I and type II cluster structural motif, respectively. All the complexes exhibit intense photoluminescence in solution with emission parameters that depending on the geometrical arrangement of the octanuclear metal core. The clusters 1-4 and 6 show single emission band in a blue region (469-488 nm) with maximum quantum yield of 94% (4), while structurally different 7 and 8 emit yellow-orange (590 nm) with unity quantum efficiency. The theoretical DFT calculations of the electronic structures have been carried out to demonstrate that the metal-centered triplet emission within the heterometallic core plays a key role for the observed phosphorescence.     

Copper perchlorate and tetrafluoridoborate compounds with the ligand 1,4,5-triazanaphthalene. Gradual transformation of mononuclear Cu(II) compounds via polynuclear mixed-valence Cu(II)/Cu(I) species to dinuclear Cu(I); syntheses, characterizations and X-ray structures

When the ligand 1,4,5-triazanaphthalene (abbreviated as tan) is reacted with Cu(II) BF(4)(-) and ClO(4)(-) salts, a variety of mononuclear compounds has been found, all with the [Cu(tan)(4)] unit and varying amounts of weakly coordinating axial ligands and lattice solvents. Reproducible compounds formed include two purple compounds, analyzing as [Cu(tan)(4)](ClO(4))(2)(CH(3)OH)(2)(H(2)O) (1) and [Cu(tan)(4)](BF(4))(2)(CH(3)OH)(1.5)(H(2)O) (3), and two blue compounds, analyzing as [Cu(tan)(4)](ClO(4))(2)(H(2)O)(2) (2) and [Cu(tan)(4)](2)(BF(4))(2)(H(2)O)(2) (4). Upon standing at room temperature, red-coloured, mixed-valence dinuclear-based 3D coordination polymers are formed by conversion of the purple/blue products, of which [Cu(2)(tan)(4)](n)(BF(4))(3n) (5) and the isomorphic methanol-water adduct [Cu(tan)(4)](n)(BF(4))(3n)(CH(3)OH)(n)(H(2)O)(5n) (5A) are presented in this paper. In addition a fully reduced dinuclear Cu(I) compound of formula [Cu(2)(tan)(3)(ClO(4))(2)] (7) has been observed, and structurally characterized, as a rare three-blade propeller structure, with a Cu-Cu distance of 2.504 ?.     

Efficient and specific strand scission of DNA by a dinuclear copper complex: comparative reactivity of complexes with linked tris(2-pyridylmethyl)amine moieties

The compound [Cu(II)(2)(D(1))(H(2)O)(2)](ClO(4))(4) (D(1) = dinucleating ligand with two tris(2-pyridylmethyl)amine units covalently linked in their 5-pyridyl positions by a -CH(2)CH(2)- bridge) selectively promotes cleavage of DNA on oligonucleotide strands that extend from the 3' side of frayed duplex structures at a site two residues displaced from the junction. The minimal requirements for reaction include a guanine in the n (i.e. first unpaired) position of the 3' overhang adjacent to the cleavage site and an adenine in the n position on the 5' overhang. Recognition and strand scission are independent of the nucleobase at the cleavage site. The necessary presence of both a reductant and dioxygen indicates that the intermediate responsible for cleavage is produced by the activation of dioxygen by a copper(I) form of the dinuclear complex. The lack of sensitivity to radical quenching agents and the high level of site selectivity in scission suggest a mechanism that does not involve a diffusible radical species. The multiple metal center exhibits a synergy to promote efficient cleavage as compared to the action of a mononuclear analogue [Cu(II)(TMPA)(H(2)O)](ClO(4))(2) (TMPA = tris(2-pyridylmethyl)amine) and [Cu(OP)(2)](2+) (OP = 1,10-phenanthroline) at equivalent copper ion concentrations. The dinuclear complex, [Cu(II)(2)(D(1))(H(2)O)(2)](ClO(4))(4), is even capable of mediating efficient specific strand scission at concentrations where [Cu(OP)(2)](2+) does not detectably modify DNA. The unique coordination and reactivity properties of [Cu(II)(2)(D(1))(H(2)O)(2)](ClO(4))(4) are critical for its efficiency and site selectivity since an analogue, [Cu(II)(2)(DO)(Cl(2))](ClO(4))(2), where DO is a dinucleating ligand very similar to D(1), but with a -CH(2)OCH(2)- bridge, exhibits only nonselective cleavage of DNA. The differences in the reactivity of these two complexes with DNA and their previously established interaction with dioxygen suggest that specific strand scission is a function of the orientation of a reactive intermediate.     

Self-assembly of D-penicillaminato M6M'8 (M = Ni(II), Pd(II), Pt(II); M' = Cu(I), Ag(I)) clusters and their organization into extended La(III)M6M'8 supramolecular structures

A series of chiral M(6)M'(8) cluster compounds having twelve free carboxylate groups, [M(6)M'(8)(D-pen-N,S)(12)X](5-) (M/M'/X = Pd(II)/Ag(I)/Cl(-) ([1](5-)), Pd(II)/Ag(I)/Br(-) ([2](5-)), Pd(II)/Ag(I)/I(-) ([3](5-)), Ni(II)/Ag(I)/Cl(-) ([4](5-)), Pt(II)/Ag(I)/Cl(-) ([5](5-)), Pd(II)/Cu(I)/Cl(-) ([6](5-)); D-H(2)pen = D-penicillamine), in which six cis-[M(D-pen-N,S)(2)](2-) square-planar units are bound to a [M'(8)X](7+) cubic core through sulfur-bridges, was synthesized by the reactions of cis-[M(D-pen-N,S)(2)](2-) with M' in water in the presence of halide ions. These M(6)M'(8) clusters readily reacted with La(3+) in aqueous buffer to form La(III)(2)M(6)M'(8) heterotrimetallic compounds, La(2)[1](CH(3)COO), La(2)[2](CH(3)COO), La(2)[3](CH(3)COO), La(2)[4](CH(3)COO), La(2)[5](CH(3)COO) and La(2)[6]Cl, in which the M(6)M'(8) cluster units are linked by La(3+) ions through carboxylate groups in a 1?:?2 ratio. While the La(III)(2)M(6)Ag(I)(8) compounds derived from [1](5-), [2](5-), [3](5-), [4](5-) and [5](5-) have a 1D helix supramolecular structure with a right-handedness, the La(III)(2)Pd(II)(6)Cu(I)(8) compound derived from [6](5-) has a 2D sheet-like structure with a triangular grid of the Pd(II)(6)Cu(I)(8) cluster units. When aqueous HCl was added to the reaction solution of [6](5-) and La(3+), another La(III)(2)Pd(II)(6)Cu(I)(8) heterotrimetallic compound, La(2)[6]Cl·HCl, in which the Pd(II)(6)Cu(I)(8) cluster units are linked by La(3+) ions to form a 2D structure with a rectangular grid, was produced. The solid-state structures of these La(III)(2)M(6)M'(8) compounds, determined by single-crystal X-ray crystallography, along with the spectroscopic properties of the M(6)M'(8) cluster compounds in solution, are described.     

3d-Metal derivatives of the [Cu(I)(SO3)4]7- ion: structure and magnetism

The Cu(SO(3))(4)(7-) anion, which consists of a tetrahedrally coordinated Cu(I) centre coordinated to four sulfur atoms, is able to act as a multidentate ligand in discrete and infinite supramolecular species. The slow oxidation of an aqueous solution of Na(7)Cu(SO(3))(4) yields a mixed oxidation state, 2D network of composition Na(5){[Cu(II)(H(2)O)][Cu(I)(SO(3))(4)]}·6H(2)O. The addition of Cu(II) and 2,2'-bipyridine to an aqueous Na(7)Cu(SO(3))(4) solution leads to the formation of a pentanuclear complex of composition {[Cu(II)(H(2)O)(bipy)](4)[Cu(I)(SO(3))(4)]}(+); a combination of hydrogen bonding and π-π stacking interactions leads to the generation of infinite parallel channels that are occupied by disordered nitrate anions and water molecules. A pair of Cu(SO(3))(4)(7-) anions each act as a tridentate ligand towards a single Mn(II) centre when Mn(II) ions are combined with an excess of Cu(SO(3))(4)(7-). An anionic pentanuclear complex of composition {[Cu(I)(SO(3))(4)](2)[Fe(III)(H(2)O)](3)(O)} is formed when Fe(II) is added to a Cu(+)/SO(3)(2-) solution. Hydrated ferrous [Fe(H(2)O)(6)(2+)] and sodium ions act as counterions for the complexes and are responsible for the formation of an extensive hydrogen bond network within the crystal. Magnetic susceptibility studies over the temperature range 2-300 K show that weak ferromagnetic coupling occurs within the Cu(II) containing chains of Na(5){[Cu(II)(H(2)O)][Cu(I)(SO(3))(4)]}·6H(2)O, while zero coupling exists in the pentanuclear cluster {[Cu(II)(H(2)O)(bipy)](4)[Cu(I)(SO(3))(4)]}(NO(3))·H(2)O. Weak Mn(II)-O-S-O-Mn(II) antiferromagnetic coupling occurs in Na(H(2)O)(6){[Cu(I)(SO(3))(4)][Mn(II)(H(2)O)(2)](3)}, the latter formed when Mn was in excess during synthesis. The compound, Na(3)(H(2)O)(6)[Fe(II)(H(2)O)(6)](2){[Cu(I)(SO(3))(4)](2)[Fe(III)(H(2)O)](3)(O)}·H(2)O, contained trace magnetic impurities that affected the expected magnetic behaviour.     

Ligand influence over the formation of dinuclear [2+2] versus trinuclear [3+3] Cu(I) Schiff base macrocyclic complexes

The preparation and characterization of three new macrocyclic ligands with pendant arms based on the [2+2] condensation of isophthalaldehyde and the corresponding triamine substituted at the central N-atom is reported. None of these new macrocyclic ligands undergo any equilibrium reaction, based on imine hydrolysis to generate [1+1] macrocyclic formation or higher oligomeric compounds, such as [3+3], [4+4], etc., at least within the time scale of days. This indicates the stability of the newly generated imine bond. In sharp contrast, the reaction of the [2+2] macrocyclic Schiff bases with Cu(I) generates the corresponding dinuclear Cu(I) complexes [Cu(2)(L(1))](2+), 1(2+); [Cu(2)(L(2))(CH(3)CN)(2)](2+), 2(2+); and [Cu(2)(L(3))(CH(3)CN)(2)](2+), 3(2+), together with their trinuclear Cu(I) homologues [Cu(3)(L(4))](3+), 4(3+); [Cu(3)(L(5))(CH(3)CN)(3)](3+), 5(3+); and [Cu(3)(L(6))(CH(3)CN)(3)](3+), 6(3+), where the [2+2] ligand has undergone an expansion to the corresponding [3+3] Schiff base that is denoted as L(4), L(5), or L(6). The conditions under which the dinuclear and trinuclear complexes are formed were analyzed in terms of solvent dependence and synthetic pathways. The new complexes are characterized in solution by NMR, UV-vis, and MS spectroscopy and in the solid state by X-ray diffraction analysis and IR spectroscopy. For the particular case of the L(2) ligand, MS spectroscopy is also used to monitor the metal assisted transformation where the dinuclear complex 2(2+) is transformed into the trinuclear complex 5(3+). The Cu(I) complexes described here, in general, react slowly (within the time scale of days) with molecular oxygen, except for the ones containing the phenolic ligands 2(2+) and 5(3+) that react a bit faster.