Dioxygen and hydrogen peroxide reduction with hemocyanin model complexes

Three copper polypyridyl complexes were examined as electrocatalysts for the oxygen reduction reaction (ORR): a Cu-N(3) complex, [Cu-[tris(6-methylpyridin-2-yl)methane]-(NCMe)]PF(6) (1); a related Cu(2)N(6) derivative, [Cu(2)-[1,2-bis(6-(bis(6-methylpyridin-2-yl)methyl)pyridin-2-yl)ethane]-(NCMe)(2)](PF(6))(2) (2); and the CuN(4) species [Cu-[tris(pyridin-2-ylmethyl)amine]](ClO(4))(2) [3](ClO(4))(2). Compared to other copper complexes, [3](ClO(4))(2) exhibits the highest reported ORR onset potential for a Cu complex of 0.53 V vs reversible hydrogen electrode at pH 1. The Cu(2)N(6) hemocyanin model is more active than the CuN(3), but both are less active than the CuN(4) complex. The results indicate that copper polypyridyl complexes are promising cathode catalysts for ORR.     

Ferromagnetic coupling in a 1D coordination polymer containing a symmetric [Cu(mu1,1-N3)2Cu(mu1,1-N3)2Cu]2+ core and based on an organic ligand obtained from the solid state

Addition of rctt-tetrakis(2-pyridyl)cyclobutane (2,2'-tpcb) in a Cu(II)/N(3)- solution afforded the 1D coordination polymer [Cu(3)(N(3))(6)(2,2'-tpcb)(DMF)(2)](n) (1). The ligand 2,2'-tpcb serves as a tetradentate bis-chelating ligand by linking linear [(DMF)Cu(mu(1,1)-N(3))(2)Cu(N(3))(2)(mu(1,1)-N(3))(2)Cu(DMF)] trinuclear units to produce a zigzag chain. Within each centrosymmetric trinuclear unit there exist two irregularly asymmetric end-on double azido-bridged [Cu(mu(1,1)-N(3))(2)Cu](2+) cores, while one of the largest Cu-Nazide-Cu angles is observed. Magnetic susceptibility data, measured from 2 to 300 K, show bulk moderate ferromagnetic coupling within the magnetically isolated trinuclear units. These data were fitted to the appropriate equation derived from the Hamiltonian H = -J(1)(S(A1)S(B) + S(A2)S(B)) - J(2)S(A1)S(A2), giving the parameters J1 = +70(3) cm(-1), J2 = -3(2) cm(-1), g = 2.12(1), with an intertrimer interaction parameter theta = -0.74(2) K. The coupling constants were correlated with the structural parameters. Density functional calculations reproduce very well the experimental J values and show that ferromagnetism for this complex is mainly due to the topology of the magnetic orbitals and the different coordination spheres of two neighboring Cu(II) atoms, resulting in a small overlap of the orbitals possessing the unpaired electrons.     

Structural snapshots of a flexible Cu2P2 core that accommodates the oxidation states Cu(I)Cu(I), Cu1.5Cu1.5, and Cu(II)Cu(II)

The phosphido-bridged dicopper(I) complex {(PPP)Cu}2 has been synthesized and structurally characterized ([PPP]- = bis(2-di-iso-propylphosphinophenyl)phosphide). Cyclic voltammetry of {(PPP)Cu}2 in THF shows fully reversible oxidations at -1.02 V (Cu1.5Cu1.5/CuICuI) and -0.423 V (CuIICuII/Cu1.5Cu1.5). Chemical oxidation of {(PPP)Cu}2 by one electron yields the class III mixed-valence species [{(PPP)Cu}2]+ (EPR, UV-vis). Structural data establish an unexpectedly large change (0.538 A) in the Cu...Cu distance upon oxidation state. Oxidation of {(PPP)Cu}2 by two electrons yields the dication [{(PPP)Cu}2]2+, an antiferromagnetically coupled dicopper(II) complex. Maintenance of a pseudotetrahedral geometry that is midway between a square plane and an ideal tetrahedron at the copper centers, along with a high degree of flexibility at the phosphide hinges, allows for efficient access to CuICuI, Cu1.5Cu1.5, and CuIICuII redox states without the need for ligand exchange, substitution, or redistribution processes.     

Electronic modification of the [Ru(II)(tpy)(bpy)(OH(2))](2+) scaffold: effects on catalytic water oxidation

The mechanistic details of the Ce(IV)-driven oxidation of water mediated by a series of structurally related catalysts formulated as [Ru(tpy)(L)(OH(2))](2+) [L = 2,2'-bipyridine (bpy), 1; 4,4'-dimethoxy-2,2'-bipyridine (bpy-OMe), 2; 4,4'-dicarboxy-2,2'-bipyridine (bpy-CO(2)H), 3; tpy = 2,2';6',2'-terpyridine] is reported. Cyclic voltammetry shows that each of these complexes undergo three successive (proton-coupled) electron-transfer reactions to generate the [Ru(V)(tpy)(L)O](3+) ([Ru(V)=O](3+)) motif; the relative positions of each of these redox couples reflects the nature of the electron-donating or withdrawing character of the substituents on the bpy ligands. The first two (proton-coupled) electron-transfer reaction steps (k(1) and k(2)) were determined by stopped-flow spectroscopic techniques to be faster for 3 than 1 and 2. The addition of one (or more) equivalents of the terminal electron-acceptor, (NH(4))(2)[Ce(NO(3))(6)] (CAN), to the [Ru(IV)(tpy)(L)O](2+) ([Ru(IV)=O](2+)) forms of each of the catalysts, however, leads to divergent reaction pathways. The addition of 1 eq of CAN to the [Ru(IV)=O](2+) form of 2 generates [Ru(V)=O](3+) (k(3) = 3.7 M(-1) s(-1)), which, in turn, undergoes slow O-O bond formation with the substrate (k(O-O) = 3 × 10(-5) s(-1)). The minimal (or negligible) thermodynamic driving force for the reaction between the [Ru(IV)=O](2+) form of 1 or 3 and 1 eq of CAN results in slow reactivity, but the rate-determining step is assigned as the liberation of dioxygen from the [Ru(IV)-OO](2+) level under catalytic conditions for each complex. Complex 2, however, passes through the [Ru(V)-OO](3+) level prior to the rapid loss of dioxygen. Evidence for a competing reaction pathway is provided for 3, where the [Ru(V)=O](3+) and [Ru(III)-OH](2+) redox levels can be generated by disproportionation of the [Ru(IV)=O](2+) form of the catalyst (k(d) = 1.2 M(-1) s(-1)). An auxiliary reaction pathway involving the abstraction of an O-atom from CAN is also implicated during catalysis. The variability of reactivity for 1-3, including the position of the RDS and potential for O-atom transfer from the terminal oxidant, is confirmed to be intimately sensitive to electron density at the metal site through extensive kinetic and isotopic labeling experiments. This study outlines the need to strike a balance between the reactivity of the [Ru═O](z) unit and the accessibility of higher redox levels in pursuit of robust and reactive water oxidation catalysts.     

Solution- and solid-state characterisation of a configurationally-stable beta-diketiminato-supported calcium primary amide

'Selective' protonolysis of the beta-diketiminato calcium derivative [Ca[(NDippCMe)(2)CH][N(SiMe(3))(2)](THF)] Dipp = C(6)H(3)(i)Pr(2)-2,6) with H(2)N(CH(2))(2)OCH(3) produced the dimeric species [Ca[(NDippCMe)(2)CH][mu-NH(CH(2))(2)OMe]](2), which has been fully characterised in solution and in the solid state.     

Structural changes upon photoexcitation into the metal-to-ligand charge-transfer state of [Cu(pqx)(PPh3)2]+ probed by resonance Raman spectroscopy and density functional theory

The structural changes that occur when [Cu(pqx)(PPh(3))(2)](+) (pqx is 2-(2'-pyridyl)quinoxaline) undergoes excitation through a metal-to-ligand charge-transfer (MLCT) transition are investigated using resonance Raman excitation profiles coupled with density functional theory (DFT). The DFT calculations predict bond lengths to within 3 pm and absolute deviations of 7 cm(-1) for the vibrational frequencies of [Cu(pqx)(PPh(3))(2)](+). TD-DFT calculations of oscillator strengths (f = 0.089) and band positions (419 nm) showed close agreement with experiment (f = 0.07, 431 nm). Resonance Raman spectra show the 527 cm(-1) (nu(29)) and 1476 cm(-1) (nu(75)) modes undergo the largest dimensionless displacement (Delta = 1.5 and 1.1, respectively) following photoexcitation into the MLCT Franck-Condon region. The solvent couples strongly to the MLCT transition and resonance Raman intensity analysis (RRIA) gives a solvent reorganization energy of 3400 cm(-1) for dichloromethane and 2800 cm(-1) for chloroform solutions. A large inner-sphere reorganization of 3430 cm(-1) in dichloromethane solution (3520 cm(-1) in chloroform solution) was found for [Cu(pqx)(PPh(3))(2)](+), indicating that the molecule as a whole undergoes significant distortion following MLCT excitation.     

Dehydration reaction of hydroxyl substituted alkenes and alkynes on the Ru(2)S(2) complex

A variety of inter- and intramolecular dehydration was found in the reactions of [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)(mu-S(2))](CF(3)SO(3))(4) (1) with hydroxyl substituted alkenes and alkynes. Treatment of 1 with allyl alcohol gave a C(3)S(2) five-membered ring complex, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH(2)CH(2)CH(OCH(2)CH=CH(2))S]](CF(3)SO(3))(4) (2), via C-S bond formation after C-H bond activation and intermolecular dehydration. On the other hand, intramolecular dehydration was observed in the reaction of 1 with 3-buten-1-ol giving a C(4)S(2) six-membered ring complex, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2) [mu-SCH(2)CH=CHCH(2)S]](CF(3)SO(3))(4) (3). Complex 1 reacts with 2-propyn-1-ol or 2-butyn-1-ol to give homocoupling products, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCR=CHCH(OCH(2)C triple bond CR)S]](CF(3)SO(3))(4) (4: R = H, 5: R = CH(3)), via intermolecular dehydration. In the reaction with 2-propyn-1-ol, the intermediate complex having a hydroxyl group, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH=CHCH(OH)S]](CF(3)SO(3))(4) (6), was isolated, which further reacted with 2-propyn-1-ol and 2-butyn-1-ol to give 4 and a cross-coupling product, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH=CHCH(OCH(2)C triple bond CCH(3))S]](CF(3)SO(3))(4) (7), respectively. The reaction of 1 with diols, (HO)CHRC triple bond CCHR(OH), gave furyl complexes, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SSC=CROCR=CH]](CF(3)SO(3))(3) (8: R = H, 9: R = CH(3)) via intramolecular elimination of a H(2)O molecule and a H(+). Even though (HO)(H(3)C)(2)CC triple bond CC(CH(3))(2)(OH) does not have any propargylic C-H bond, it also reacts with 1 to give [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH(2)C(=CH(2))C(=C=C(CH(3))(2))]S](CF(3)SO(3))(4) (10). In addition, the reaction of 1 with (CH(3)O)(H(3)C)(2)CC triple bond CC(CH(3))(2)(OCH(3)) gives [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(2)][mu-S=C(C(CH(3))(2)OCH(3))C=CC(CH(3))CH(2)S][Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)]](CF(3)SO(3))(4) (11), in which one molecule of CH(3)OH is eliminated, and the S-S bond is cleaved.     

Synthesis and characterization of the dimercury(I)-linked compound [PPn]4[(Re7C(CO)21Hg)2]. Oxidative cleavage of the mercury-mercury bond leading to carbidoheptarhenate complexes of mercury(II), including [PPN][Re7C(CO)21Hg(S=C(NME2)2)

The reaction of [PPN](3)[Re(7)C(CO)(21)] with Hg(2)(NO(3))(2).2H(2)O in dichloromethane formed the complex [PPN](4)[(Re(7)C(CO)(21)Hg)(2)] ([PPN](4)[1]), isolated in 60% yield. Analogous salts of [1](4-) with [PPh(4)](+) and [NEt(4)](+) were also prepared. The crystal structure of [PPN](4)[1] showed that two carbidoheptarhenate cores are linked by a dimercury(I) unit (d(Hg-Hg) = 2.610(4) A), with each individual mercury atom face-bridging. Oxidative cleavage of the Hg-Hg bond in [1](4-) was effected by 4-bromophenyl disulfide to form [Re(7)C(CO)(21)HgSC(6)H(4)Br](2-) ([4](2-)), by I(2) to form [Re(7)C(CO)(21)HgI](2-) ([5](2-)), and by Br(2) to form [Re(7)C(CO)(21)HgBr](2-) ([6](2-)). Oxidation of [1](4-) by ferrocenium ion (2 equiv) in the presence of tetramethylthiourea resulted in the derivative [Re(7)C(CO)(21)HgSC(NMe(2))(2)](-) ([7](-)). The molecular structure of [PPN][7] was determined by X-ray crystallography. This is the first example of a carbidoheptarhenate-mercury complex with a neutral ligand on mercury, and ligand exchange was demonstrated by displacement with triethylphosphine. Complex [7](-) can also be prepared by protonating [Re(7)C(CO)(21)HgO(2)CCH(3)](2-) in the presence of tetramethylthiourea. Cyclic voltammetry data to calibrate and compare the redox properties of compounds [1](4-) and [7](-) have been measured.     

Syntheses, structural studies, and magnetic properties of divalent Cu and Co selenites with organic constituents

Six new divalent metal selenites have been synthesized by hydro-/solvothermal methods which leads to the incorporation of the organic template as a cation or a ligand. The structure of [H(2)pip][Cu(SeO(3))(2)] (1) (pip=piperazine) features 1D anionic chains of [Cu(SeO(3))(2)](2-) which are cross-linked by the template cations through hydrogen bonds into a 2D layer. In [Cu(C(3)H(4)N(2))(SeO(3))] (2) the organic template is coordinated to the copper(II) ion of the inorganic Cu(SeO(3)) layer. The isostructural compounds [H(2)en][M(HSeO(3))(2)Cl(2)] (en=ethylenediamine; M=Cu (3), Co (4)) contain layers of [MCl(2)(HSeO(3))(2)](2-) units (M=Cu, Co), which are cross-linked by the template cations via hydrogen bonds into a 3D network. The structure of [H(2)en][Cu(2)(SeO(3))(2)(HSeO(3))](2)H(2)O (5), consists of a pillared layered architecture in which the Cu(SeO(3)) layers are further interconnected by bridging hydrogen selenite groups (the pillar). The compound [H(2)pip][Cu(2)(Se(2)O(5))(3)] (6), which crystallizes as a 3D open framework represents the first organically templated metal diselenite. These new compounds are thermally stable up to at least 170 degrees C. All of the compounds exhibit fairly strong antiferromagnetic interactions. More interestingly, compounds 3 and 4 behave as a weak ferromagnets below the critical temperatures of T(c)=12 and 8 K, respectively, and both of them exhibit spin-flop phase transitions around 800+/-100 Oe.     

Syntheses and structures of copper(I) complexes based on Cu(n)X(n) (X = Br and I; n = 1, 2 and 4) units and bis(pyridyl) ligands with longer flexible spacer

Self-assembly of four bis(pyridyl) ligands with longer flexible spacer: 1,4-bis(3-pyridylaminomethyl)benzene (L1), 1,4-bis(2-pyridylaminomethyl)benzene (L2), 1,3-bis(3-pyridylaminomethyl)benzene (L3) and 1,3-bis(2-pyridylaminomethyl)benzene (L4), and CuX (X = Br and I) leads to the formation of eight [Cu(n)X(n)]-based (X = Br and I; n = 1, 2, and 4) complexes, [Cu(2)I(2)L1(PPh(3))(4)] (1), [Cu(4)Cl(2)Br(2)(L4)(2)(PPh(3))(6)]·(CH(3)CN)(2) (2), [Cu(2)I(2)(L3)(2)] (3), {[Cu(2)Br(2)L2(PPh(3))(2)]·(CH(2)Cl(2))(2)}(n) (4), [CuIL1](n)·nCH(2)Cl(2) (5), [CuIL1](n) (6), [CuIL4](n) (7) and [Cu(2)I(2)L4](n) (8), which have been synthesized and characterized by elemental analysis, IR, TG, powder and single-crystal X-ray diffraction. Structural analyses show that the eight complexes possess an increasing dimensionality from 0D (1-3) to 1D (4) to 2D (5-8), in which 1 and 2 contain a CuX unit, 2-7 contain a Cu(2)X(2) unit and 8 contains a Cu(4)X(4) unit. Such evolvement indicates that the conformation of flexible bis(pyridyl) ligands and the participation of triphenylphosphine (PPh(3)) as a second ligand take an essential role in the framework formation of the Cu(i) complexes. Moreover, a pair of symmetry-related L3 ligands in complex 3 coordinate to the rhomboid Cu(2)I(2) dimer to form "handcuff-shaped" dinuclear structures, which are further joined together through intermolecular N-HI hydrogen bonds to furnish a 2D (4,4) layer. Although complexes 5 and 6 exhibit a similar 2D (4,4) layer constructed from L1 ligand bridging [Cu(2)I(2)](n) units, the different packing fashion of the layers leads to the formation of 3D porous frameworks of 5 and dense 3D frameworks of 6. The "twisted-boat" conformation of the Cu(4)I(4) tetramer unit in complex 8 has not been reported so far.     

Fully Delocalized Mixed-Valent Cu1.5Cu1.5 Complex: Strong Cu-Cu interaction and Fast Electron Self-Exchange Rate Despite Large Structural Changes**

A flexible macrocyclic ligand with two tridentate {CNC} compartments can host two Cu ions in reversibly interconvertible states, Cu^ICu^I ( 1 ) and mixed-valent Cu^1.5Cu^1.5 ( 2 ). They were characterized by XRD and multiple spectroscopic methods, including EPR, UV/Vis absorption and MCD, in combination with TD-DFT and CASSCF calculations. 2 features a short Cu⋅⋅⋅Cu distance (≈2.5 Å; compared to ≈4.0 Å in 1 ) and a very high delocalization energy of 13 000 cm⁻¹, comparable to the mixed-valent state of the biological Cu_A site. Electron self-exchange between 1 and 2 is rapid despite large structural reorganization, and is proposed to proceed via a sequential mechanism involving an active conformer of 1 , viz. 1′ ; the latter has been characterized by XRD. Such electron transfer (ET) process is reminiscent of the conformationally gated ET proposed for biological systems. This redox couple is a unique pair of flexible dicopper complexes, achieving fast electron self-exchange closely related to the function of the Cu_A site.     

Construction of a novel Mo/Cu/S cluster with a closed double-cubane-like polyhedron and a chain polymer of W/Cu/S clusters

Reaction of [MoOS(3)](2)(-) and [WS(4)](2)(-) with Cudtp (dtp = diethyl dithiophosphate) gave rise to the clusters [Bu(4)N](2)[(MoOS(3))(4)Cu(12)(dtp)(6)], 1, and [Et(4)N][(WS(4)Cu(4))(dtp)(3)], 2, respectively. In cluster 1, the dtp- ligands act as both monodentate and bidentate ligands that bridge between Cu atoms and link together a closed double-cubane-like [Mo(2)O(2)S(6)Cu(6)](2+) core and two incomplete cubane-like [MoOS(3)Cu(3)]+ units. In cluster 2, the [WS(4)Cu(4)](2+) fragments were connected via bidentate and doubly bridging dtp- bridges to give a chain polymeric anion. Cluster 1 is the first example of a Mo/Cu/S cluster that contains a closed double-cubane-like structure. Compound 2 is also rare and the first W/Cu/S polymer with dtp- linkages.     

Synthesis of the (N2)3- radical from Y2+ and its protonolysis reactivity to form (N2H2)2- via the Y[N(SiMe3)2]3/KC8 reduction system

Examination of the Y[N(SiMe(3))(2)](3)/KC(8) reduction system that allowed isolation of the (N(2))(3-) radical has led to the first evidence of Y(2+) in solution. The deep-blue solutions obtained from Y[N(SiMe(3))(2)](3) and KC(8) in THF at -35 °C under argon have EPR spectra containing a doublet at g(iso) = 1.976 with a 110 G hyperfine coupling constant. The solutions react with N(2) to generate (N(2))(2-) and (N(2))(3-) complexes {[(Me(3)Si)(2)N](2)(THF)Y}(2)(μ-η(2):η(2)-N(2)) (1) and {[(Me(3)Si)(2)N](2)(THF)Y}(2)(μ-η(2):η(2)-N(2))[K(THF)(6)] (2), respectively, and demonstrate that the Y[N(SiMe(3))(2)](3)/KC(8) reaction can proceed through an Y(2+) intermediate. The reactivity of (N(2))(3-) radical with proton sources was probed for the first time for comparison with the (N(2))(2-) and (N(2))(4-) chemistry. Complex 2 reacts with [Et(3)NH][BPh(4)] to form {[(Me(3)Si)(2)N](2)(THF)Y}(2)(μ-N(2)H(2)), the first lanthanide (N(2)H(2))(2-) complex derived from dinitrogen, as well as 1 as a byproduct, consistent with radical disproportionation reactivity.     

First example of a 2:1 cocrystal of mixed Cu(I)/Cu(II) complexes and a novel ferromagnetic bis(mu-hydroxo)dicopper(II) complex with a bis(pyrazol-1-yl)methane bidentate ligand

A unique 2:1 cocrystal of mixed Cu(I)/Cu(II) complexes [Cu(I)(H2CPz2)(MeCN)2](ClO4) (1) and [Cu(II)(H2CPz2)2(ClO4)2] (4), a novel ferromagnetic ClO(4-)-bridged bis(mu-hydroxo)dicopper(II) complex, [Cu2(H2CPz2)2(OH)2(ClO4)](ClO4)(CH3CN)(0.5) (5), and a bischelated copper(I) complex, [Cu(H2CPz2)2](ClO4) (2), prepared from a one-pot reaction of [Cu(MeCN)4](ClO4) and H2CPz2, are described. The structures of these complexes have been determined by X-ray crystallographic methods. The Cu(I)-N(acetonitrile) bond distances in complex 1 are nonequivalent (1.907(8) and 2.034(9) A), leading to the dissociation of one MeCN to form a Y-shaped complex, [Cu(I)(H2CPz2)(MeCN)](ClO4) (3), which is oxidized readily in air to form complex 5 with a butterfly Cu2O2 core.     

用[BMIM][Cu2Cl3]离子液体萃取脱除汽油中的硫化物

以不同的IL（ionic liquid）/油质量比,采用[BMIM][Cu2Cl3]（[BMIM]=1-butyl-3-methylimidazolium）对模型汽油和商品汽油进行单步和多步萃取脱硫实验;并合成几种具有不同阴离子和阳离子结构的离子液体,评价和比较了离子液体对商品汽油的萃取脱硫性能的影响。实验结果表明,具有较好的水稳定性和常温流动性的[BMIM] [Cu2Cl3]离子液体硫容较高,在IL/油质量比为1∶3时,经多步萃取后,油品中的硫质量分数降至20×10-6～30×10-6,累计脱硫率超过95%。汽油中其他组分对脱硫效果影响很小。[BMIM][Cu2Cl3]与汽油形成稳定的两相系统,分离方便。离子液体脱硫能力可以通过四氯化碳反萃取完全恢复。     

Cu(I)-containing room temperature ionic liquids as selective and reversible absorbents for propyne

A Cu(i)-containing room temperature ionic liquid (Cu-RTIL), prepared from CuCl and 1,3-dimethylimidazolium methylphosphite ([DMIM][MeHPO(3)]), was found to reversibly and selectively interact with propyne over propylene. Cu-RTIL exhibited 12 times higher propyne absorption capacity and 14 times higher ideal propyne/propylene selectivity than [DMIM][MeHPO(3)]. Fast atom bombardment (FAB)-mass spectral and computational results with Cu-RTIL (CuCl/[DMIM][MeHPO(3)] = 1/2) strongly imply that the Cu-RTIL contains stable methylphosphite-coordinated anionic Cu(i) species such as CuCl(MeHPO(3))(-) and Cu(MeHPO(3))(2)(-). Computational studies on the optimized structures demonstrate that the preferential absorption of propyne over propylene in a Cu-RTIL originates from the difference in the interaction mode between the coordinated phosphite ligand and propyne or propylene. Strong π-complexation of propylene and propyne with Cu in Cu-RTIL is not observed.     

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 ?.     

The axial methionine ligand may control the redox reorganizations in the active site of blue copper proteins

Structural and energetic reorganizations in redox reaction of type 1 copper proteins are studied by density functional and ab initio molecular orbital calculations. Model complexes of the active site with varying number of ligands, from Cu(SCH(3))(0/+) to Cu(SCH(3))(Im)(2)(S(CH(3))(2))(0/+), where Im denotes imidazole, are investigated. Following the findings of structural instability in Cu(I)(SCH(3))(Im)(2) and its stabilization by the addition of the axial methionine (Met) ligand model, the structure and energetics are examined as functions of the Cu-S(Met) distance in the range of 2.1-3.3 A?. The reorganization energies in both redox states exhibit a minimum at the Cu-S(Met) distance of ～2.4?A?, whereas the ionization potential increases monotonically. The changes of reorganization energies correlate well with one of the Cu-N(His) distances rather than the Cu-S(Cys) distance. The estimated Arrhenius factor for oxidation of plastocyanin by P700(+) (in photosystem I) changes by an order of magnitude when the Cu-S(Met) distance fluctuates between 2.4 and 3.0 A?, whereas the factor for reduction of plastocyanin by cytochrome f is nearly constant. Together with the data from our previous classical molecular dynamics simulation of solvated protein, we argue that the electron transfer rate is affected, and thus may be controlled, by the fluctuation of a weakly bound axial Met ligand. We also present the assessment of various exchange-correlation functionals, including those with the long-range correction, against the CCSD(T) reference and on the basis of a perturbative adiabatic connection model. For Cu(SCH(3)) and Cu(SCH(3))(Im), simple correlations have been found between the reorganization energies and the amount of Hartree-Fock exchange.     

Catalytic transesterification of dialkyl phosphates by a bioinspired dicopper(II) macrocyclic complex

For a number of phosphoryltransfer enzymes, including the exonuclease subunit of DNA polymerase I, a mechanism involving two-metal ions and double Lewis-acid activation of the substrate, combined with leaving group stabilization, has been proposed. Inspired by the active site structure of this enzyme, we have designed as a synthetic phosphoryl transfer catalyst the dicopper(II) macrocyclic complex LCu(2). Crystal structures of complexes [(L)Cu(2)(mu-NO(3))(NO(3))](NO(3))(2) (1), [(L)Cu(2)(mu-CO(3))(CH(3)OH)](BF(4))(2) (2), and [(L)Cu(2)(mu-O(2)P(OCH(3))(2))(NO(3))](NO(3))(2) (3) illustrate various possibilities for the interaction of oxoanions with the dicopper(II) site. 1 efficiently promotes the transesterification of dimethyl phosphate (DMP) in CD(3)OD, k(cat) = 2 x 10(-)(4) s(-)(1) at 55 degrees C. 1 is the only available catalyst for the smooth transesterification of highly inert simple dialkyl phosphates. From photometric titrations and the pH dependence of reactivity, we conclude that a complex [(L)Cu(2)(DMP)(OCH(3))](2+) is the reactive species. Steric bulk at the -OR substituents of phosphodiester substrates O(2)P(OR)(2)(-) drastically reduces the reactivity of 1. This is explained with -OR leaving group stabilization by Cu coordination, an interaction which is sensitive to steric crowding at the alpha-C-atom of substituent R. A proposed reaction mechanism related to that of the exonuclease unit of DNA polymerase I is supported by DFT calculations on reaction intermediates. The complex [(L)Cu(3)(mu(3)-OH)(mu-CH(3)O)(2)(CH(3)CN)(2)](ClO(4))(3) (4) incorporates a [Cu(OH)(OCH(3))(2)(CH(3)CN)(2)](-) complex anion, which might be considered as an analogue of the [PO(2)(OCH(3))(2)(OCD(3))](2)(-) transition state (or intermediate) of DMP transesterification catalyzed by LCu(2).     

New structural features of unsupported chains of metal ions in luminescent [(NH3)4Pt][Au(CN)2]2 x 1.5(H2O) and related salts

Luminescent [(NH(3))(4)Pt][Au(CN)(2)](2).1.5(H(2)O), which forms from aqueous solutions of [(NH(3))(4)Pt]Cl(2) and K[Au(CN)(2)], crystallizes with extended chains of the two ions with multiple close Pt...Au (3.2804(4) and 3.2794(4) A) and Au...Au (3.2902(5), 3.3312(5), and 3.1902(4) A) contacts. Nonluminescent [(NH(3))(4)Pt][Ag(CN)(2)](2).1.4(H(2)O) is isostructural with [(NH(3))(4)Pt][Au(CN)(2)](2).1.5(H(2)O). Treatment of [(NH(3))(6)Ni]Cl(2) with K[Au(CN)(2)] forms [(NH(3))(2)Ni][Au(CN)(2)](2) in which the [Au(CN)(2)](-) ions function as nitrile ligands toward nickel, which assumes a six-coordinate structure with trans NH(3) ligands. The [Au(CN)(2)](-) ions self-associate into linear columns with close Au...Au contacts of 3.0830(5) A, and pairs of gold ions in these chains make additional but longer (3.4246(5) A) contacts with other gold ions.