Ab initio structure of the (Na(2)[CAl(4)])(2) dimer. Next step toward solid materials containing tetracoordinate planar carbon

We performed ab initio calculations on the (Na(2)[CAl(4)])(2) dimer in order to test if the two CAl(4)(2-) groups react to form the more stable dimeric structure, or if the two CAl(4)(2-) groups remain separated in a true dimeric structure. Working at the B3LYP/6-311+G* level of theory (previously found to be satisfactory in our earlier calculations with CAl(4)(-) and Na[CAl(4)](-)), we established that structures with the C-C bond are higher in energy than the structures with two isolated structural CAl(4)(-) units separated by more than 5 A with their structural and electronic integrity preserved. However, alternative structures involving reaction between two CAl(4)(2-) groups forming a C(2)Al(8)(4-) cluster without the C-C bond are higher in energy, but they are still competitive with the true dimeric structure. While we found alternative structures of Na(4)C(2)Al(8) with the energy comparable to that of the true dimeric structure, we hope that the solid ionic salt with the pentaatomic tetracoordinate planar carbon [CAl(4)](2)(-) building block can be synthesized.     

Metal complexes with a new N(4)O(3) amine pendant-armed macrocyclic ligand: synthesis, characterization, crystal structures, and fluorescence studies

The synthesis of a new oxaaza macrocyclic ligand, L, derived from O(1),O(7)-bis(2-formylphenyl)-1,4,7-trioxaheptane and tren containing an amine terminal pendant arm, and its metal complexation with alkaline earth (M = Ca(2+), Sr(2+), Ba(2+)), transition (M = Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+)), post-transition (M = Pb(2+)), and Y(3+) and lanthanide (M = La(3+), Er(3+)) metal ions are reported. Crystal structures of [H(2)L](ClO(4))(2).3H(2)O, [PbL](ClO(4))(2), and [ZnLCl](ClO(4)).H(2)O are also reported. In the [PbL] complex, the metal ion is located inside the macrocyclic cavity coordinated by all N(4)O(3) donor atoms while, in the [ZnLCl] complex, the metal ion is encapsulated only by the nitrogen atoms present in the ligand. pi-pi interactions in the [H(2)L](ClO(4))(2).3H(2)O and [PbL](ClO(4))(2) structures are observed. Protonation and Zn(2+), Cd(2+), and Cu(2+) complexation were studied by means of potentiometric, UV-vis, and fluorescent emission measurements. The 10-fold fluorescence emission increase observed in the pH range 7-9 in the presence of Zn(2+) leads to L as a good sensor for this biological metal in water solution.     

N-氧化吡啶-2-甲醛衍生物的配合物研究(Ⅰ)——与二胺生成的双Schiff碱铜配合物的合成和晶体结构

报道了N-氧化吡啶-2-甲醛(Pio)与乙二胺(en)及1,3-丙二胺(tn)生成的双Schiff碱Cu(Ⅱ)配合物([Cu(Pioen)H_2O](ClO_4)_2和[Cu(Piotn)(H_2O)_2](ClO_4)2)的合成和晶体结构。晶体[Cu(Pioen)H_2O_3(ClO_4)_2属正交晶系,空间群P2_12_12_2,α=7.9534(19),b=7.6768(48),c=26.1037(189),Z=4,R=0.077 1,R_w=0.0771。晶体[Cu(Piotn)-(H_2O)_2](ClO_4)_2属正交晶系,空间群P~(nam),α=7.1360(24)。b=13.7887(42),0=22.2556(81),Z=4,R=0.0491,R_w=0.0491。结构由Patterson函数及Fourier合成法解出,经全矩阵最小二乘法修正至收敛。     

Metal Ion-Coupled Electron Transfer of a Nonheme Oxoiron(IV) Complex: Remarkable Enhancement of Electron-Transfer Rates by Sc(3+)

Rates of electron transfer from a series of one-electron reductants to a nonheme oxoiron(IV) complex, [(N4Py)Fe(IV)(O)](2+), are enhanced as much as 10(8)-fold by addition of metal ions such as Sc(3+), Zn(2+), Mg(2+), and Ca(2+); the metal ion effect follows the Lewis acidity of metal ions. The one-electron reduction potential of [(N4Py)Fe(IV)(O)](2+) is shifted to a positive direction by 0.84 V in the presence of Sc(3+) ion (0.20 M).     

Visible absorption spectra of metal-catecholate and metal-tironate complexes

Interactions between metals and catechol (1,2-dihydroxybenzene) or other ortho-dihydroxy moieties are being found in an increasing number of biological systems with functions ranging from metal ion internalization to biomaterial synthesis. Although metal-catecholate interactions have been studied in the past, we present the first systematic study of an array of these compounds, all prepared under identical conditions. We report the ultraviolet-visible absorption (UV-vis) spectra for catecholate and tironate complexes of the first row transition elements. Generation and identification of these species were accomplished by preparing aqueous solutions with varied ligand:metal ratios and subsequently titrating with base (NaOH). Controlled ligand deprotonation and metal binding resulted in sequential formation of complexes with one, two, and sometimes three catecholate or tironate ligands bound to a metal ion. We prepared the mono-, bis- and tris-catecholates and -tironates of Fe(3+), V(3+), V(4+)and Mn(3+), the mono- and bis-catecholates and -tironates of Cu(2+), Co(2+), Ni(2+), Zn(2+), Cr(2+) and Mn(2+), and several Ti(4+) and Cr(3+) species. The UV-vis spectra of each complex are described, some of which have not been reported previously. These data can now be applied to characterization of biological metal-catecholate systems.     

Planar carbon radical's assembly and stabilization, a way to design spin-based molecular materials

In this work, we report the first computational study on the assembly and stabilization of a novel kind of radical, i.e., the planar tetracoordinate carbon radical CAl(4)(-). Based on the 6-31+G(d)-UB3LYP, UMP2 and UCCSD(T) calculations on charged [D(CAl(4))M](q-), saturated [D(CAl(4))M(n)] and extended (CpM)(p)(CAl(4))(q) sandwich-like compounds (D = CAl(4)(-), Cp(-); M = Li, Na, K, Be, Mg, Ca), we find that for the six metals, the planar radical CAl(4)(-) can only be assembled in the "hetero-decked sandwich" scheme (e.g. [CpM(CAl(4))](q-)) rather than the traditional "homo-decked sandwich" scheme. Moreover, the low and high spin states of the designed sandwich-like species are perfectly degenerate during assembly. This can be ascribed to the good spin conservation of the CAl(4)(-) deck and the good spatial separation between two CAl(4)(-) decks. Our results show for the first time that the planar radical CAl(4)(-) can act as a new type of spin-embedded "superatom" for cluster assembly when it is assisted by a rigid partner like Cp(-). The good spin-conservation of CAl(4)(-) is very promising for the future design of novel paramagnetic and diamagnetic materials. The ionic, clustering and radical interactions between the two decks are analyzed in detail, which is quite crucial to improve the insight and understanding of the nature and origin of the interactions of the "deck-core-deck" in the metallocenes. Such information is also important in understanding the radical reactions and designing novel spin-based molecular materials. The present study should be expected to enrich the flat carbon chemistry, radical chemistry, metallocene chemistry and combinatorial chemistry.     

Sorption of divalent metal ions on CrPO4

The divalent metal ion sorption (Cu(2+), Cd(2+), Ni(2+), and Pb(2+)) on chromium phosphate (CrPO(4)) was studied as a function of pH, temperature, and concentration of metal ions. The sorption of metal ions is observed to increase with the increase in pH, temperature, and concentration of metal ions in solution. The mechanism of sorption is found to be the exchange of the hydrolyzed metal cations with the protons from solid at high temperature. The sorption at low temperature is found to be accompanied by the precipitation of the corresponding metal phosphates such as Pb(3)(PO(4))(2).     

酚醛型苯基硫脲树脂对Pt4+、Pd2+的吸附性能

螯合树脂是一类具有螯合功能基,能从含有金属离子的溶液中有选择的捕集、分离特定金属离子的功能高分子。含N、S、O配位原子的螯合树脂对贵、重金属离子有良好的吸附性能和吸附选择性。利用螯合树脂的吸附性能,     

硫酸铵-碘化钾-氯化十六烷基吡啶-水体系浮选分离镉的研究

研究了硫酸铵-碘化钾-氯化十六烷基吡啶-水体系浮选分离镉的行为及其与常见离子分离的条件。结果表明，控制pH5．0，在1．0g(NH4)2SO4存在下，Cd^2 可被碘化钾-氯化十六烷基吡啶-水体系浮选，而Zn^2 、Mn^2 、Fe^2 、Co^2 、Ni^2 、A1^3 等离子在该体系中不被浮选，可实现Cd^2 与这些离子的定量分离。对合成水样进行了浮选分离测定，结果满意。     

Solvent extraction of divalent metal ions with azacrown ether substituted acylpyrazolones

Novel 4-acyl-5-pyrazolones having aza-15-crown-5 (HPMP-A15C5) and aza-18-crown-6 (HPMP-A18C6) moieties as an intramolecular synergist have been synthesized by simple coupling reactions between 1-phenyl-3-methyl-4-chloroacetyl-5-pyrazolone and the corresponding azacrown ethers. The solvent extraction of the divalent metal ions (Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Pb(2+)) were examined. Synergistic extractions with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HPMBP) and benzocrown ethers were also examined for a comparison. Extractions with the novel acylpyrazolones were unique and quite different from those with HPMBP and benzocrown ethers. The synergistic effect with benzocrown ethers was low, and an obvious difference brought by the ring size was not observed. The extractions of the divalent metal ions with HPMP-A18C6 were generally enhanced, as compared to those alone with HPMBP; on the contrary, the extractions with HPMP-A15C5 were relatively poor.     

Complex formation between phytic acid and divalent metal ions: a solution equilibria and solid state investigation

An investigation on the complex formation equilibria between divalent metal ions Me (with Me=Mn, Co, Ni, Cu, Cd, and Pb) and phytic acid (H(12)L) is presented. Experiments were performed through a potentiometric methodology by measuring, at 25 degrees C, the proton and, in some cases (Cu(2+), Cd(2+), and Pb(2+)), also the metal ion activity at equilibrium in solutions containing, besides the metal and the ligand, 3 M NaClO(4) as the ionic medium. Unhydrolyzed solutions of the metal ion at millimolar concentration levels were titrated with solutions of about 10 mM sodium phytate, until the formation of a solid phase took place (always at pH approximately 2.5, except in the case of Cu(2+), which formed soluble complexes up to pH approximately 3.3). Coulometry was employed to produce very dilute solutions of either Cu(2+), Cd(2+), or Pb(2+) of accurately known composition. The emf data were explained by assuming, in the acidity interval explored, the formation of the complexes of general stoichiometry MeH(5)L(5-) and Me(2)H(3)L(5-). Coordination compounds in the solid state were also synthesized and characterized by elemental analysis, thermal analysis, and ICP spectroscopy. The solids had a general stoichiometry Me(6)H (t)LCl (t). x H(2)O, with the following t and x values for each metal investigated: Me ( t; x) = Mn (4; 2); Co (4; 2); Ni (4; 2); Cu (2; 2.5); Zn (2; 1); Sn (6; 6).     

Vibrational characteristics of outer-sphere surface complexes: example of sulfate ions adsorbed onto metal (hydr)oxides

The vibrational characteristics of outer-sphere complexes of sulfate at several mineral oxide-water interfaces were investigated by in situ attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy. In the IR spectra obtained from surface outer-sphere complexes, only one peak of the asymmetric stretching vibrational mode υ(3) similar to that of free sulfate ion SO(4)(2-) in aqueous solution is observed. However, on the investigated (hydr)oxide surfaces of Al(3+), Ti(4+), Fe(2+/3+), Cr(3+), Ce(4+), Cu(2+), Y(3+), Zn(2+), and Nd(3+), a shift of up to 14 cm(-1) was found, which was correlated to the polarizing power of the metal cations. A high polarizing power was found to result in a stronger shift of υ(3) compared to that of the aqueous SO(4)(2-) ion. Furthermore, the impact of the metal oxide structure on the characteristics of the formed outer-sphere complex was negligible because different Al and Fe (hydr)oxides did not show any changes in the respective IR spectra. Finally, the ionic strength (1-10(-4) M) and pH (6.8-3.1) have been modified to change the surface potential, showing no direct influence on the spectra (i.e., on the geometry of the outer-sphere complex).     

Highly sensitive and fast responsive fluorescence turn-on chemodosimeter for Cu2+ and its application in live cell imaging

A rhodamine B derivative 4 containing a highly electron-rich S atom has been synthesized as a fluorescence turn-on chemodosimeter for Cu(2+). Following Cu(2+)-promoted ring-opening, redox and hydrolysis reactions, comparable amplifications of absorption and fluorescence signals were observed upon addition of Cu(2+); this suggests that chemodosimeter 4 effectively avoided the fluorescence quenching caused by the paramagnetic nature of Cu(2+). Importantly, 4 can selectively recognize Cu(2+) in aqueous media in the presence of other trace metal ions in organisms (such as Fe(3+), Fe(2+), Cu(+), Zn(2+), Cr(3+), Mn(2+), Co(2+), and Ni(2+)), abundant cellular cations (such as Na(+), K(+), Mg(2+), and Ca(2+)), and the prevalent toxic metal ions in the environment (such as Pb(2+) and Cd(2+)) with high sensitivity (detection limit < or =10 ppb) and a rapid response time (< or =1 min). Moreover, by virtue of the chemodosimeter as fluorescent probe for Cu(2+), confocal and two-photon microscopy experiments revealed a significant increase of intracellular Cu(2+) concentration and the subcellular distribution of Cu(2+), which was internalized into the living HeLa cells upon incubation in growth medium supplemented with 50 muM CuCl(2) for 20 h.     

Separation and gravimetric determination of cerium and lanthanum with N-m-tolyl-m-nitrobenzohydroxamic acid

Cerium and lanthanum were determined gravimetrically by selective precipitation with N-m-tolyl-m-nitrobenzohydroxamic acid and separated from several metal ions such as Ag(+), Be(2+) , Pb(2+) , Mn(2+) , Cu(2+), Zn(2+) , Cd(2+) , Hg(2+) , Pd(2+) , Ga(3+) A1(3+) , Bi(3+) , Sb(3+), Sn(4+), Ce(3+) , Pr(3+) , Nd(3+) , Ti(4+), Zr(4+), Th(4+), V(5+) , Mo(6+) and U(6+) . The precipitates were weighted directly after drying at 110 degrees . The analytical results indicated the composition of the complexes to be (C(14)H(11)N(2)O(4))(n)M.     

Metal ion-binding properties of 1-methyl-4-aminobenzimidazole (=9-methyl-1,3-dideazaadenine) and 1,4-dimethylbenzimidazole (=6,9-dimethyl-1,3-dideazapurine). quantification of the steric effect of the 6-amino group on metal ion binding at the N7 site of the adenine residue

The stability constants of the 1:1 complexes formed between Mg(2+), Ca(2+), Sr(2+), Ba(2+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), or Cd(2+) (=M(2+)) and 1-methyl-4-aminobenzimidazole (MABI) or 1,4-dimethylbenzimidazole (DMBI) were determined by potentiometric pH titrations in aqueous solution (25 degrees C; I = 0.5 M, NaNO(3)). Some of the stability constants were also measured by UV spectrophotometry. The acidity constants of the species H(2)(MABI)(2+) and H(DMBI)(+) were determined by the same methods, some twice. Comparison of the stability constants of the M(MABI)(2+) and M(DMBI)(2+) complexes with those calculated from log versus p straight-line plots, which were established previously for sterically unhindered benzimidazole-type ligands (=L), reveals that the stabilities of the M(MABI)(2+) and M(DMBI)(2+) complexes are significantly reduced due to steric effects of the C4 substituents on metal ion binding at N3. This effect is more pronounced in the M(DMBI)(2+) complexes. Considering the steric equivalence of methyl and (noncoordinating) amino groups (as they occur in adenines), it is concluded that the same extent of steric inhibition by the (C6)NH(2) group is to be expected on metal ion binding at N7 with adenine derivatives. The basicity of the amino group in MABI is significantly higher than in its corresponding adenine derivative. Indeed, it is concluded that in the M(MABI)(2+) complexes chelate formation involving the amino group occurs to some extent. The formation degrees of these "closed" species are calculated; they vary for the complexes of Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), or Cd(2+) between about 50 and 90%. The stability of the M(MABI)(2+) and M(DMBI)(2+) complexes with the alkaline earth ions is very low but unaffected by the C4 substituent; this probably indicates that in these instances outersphere complexes (with a water molecule between N3 and the metal ion) are formed.     

A bis-guanidine-based multisignaling sensor molecule that displays redox-ratiometric behavior or fluorescence enhancement in the presence of anions and cations

[structure: see text]The guanidine bridge in the new structural motif [3,3]ferrocenophane acts as a dual binding site for anions and metal ions. Sensing of anions (Cl(-), F(-), NO(3)(-), HSO(4)(-), and H(2)PO(4)(-)) takes place by redox-ratiometric measurements, whereas metal ion (Zn(2+), Ni(2+), and Cd(2+)) recognition is achieved by fluorescence measurements.     

Serendipity and design in the generation of new coordination polymers: an extensive series of highly symmetrical guanidinium-templated, carbonate-based networks with the sodalite topology

The serendipitous discovery of a 3D [Cu(CO(3))(2)(2-)](n) network with the topology of the 4(2)6(4) sodalite net in [Cu(6)(CO(3))(12)(CH(6)N(3))(8)].K(4).8H(2)O paved the way for the deliberate engineering of an extensive series of structurally related guanidinium-templated metal carbonates of composition [M(6)(CO(3))(12)(CH(6)N(3))(8)]Na(3-)[N(CH(3))(4)].xH(2)O, where the divalent metal M in the framework may be Mg, Mn, Fe, Co, Ni, Cu, Zn, or Cd. A closely related crystalline material with a [Ca(CO(3))(2)(2-)](n) sodalite-like framework, but containing K(+) rather than Na(+), of composition [Ca(6)(CO(3))(12)(CH(6)N(3))(8)]K(3)[N(CH(3))(4)].3H(2)O was also isolated. All of these compounds were obtained under the simplest possible conditions from aqueous solution at room temperature, and their structures were determined by single-crystal X-ray diffraction. Pairs of guanidinium cations are associated with the hexagonal windows of the sodalite cages, alkali-metal cations are associated with their square windows, and N(CH(3))(4)(+) ions are located at their centers. Structures fall into two classes depending on the metal, M(II), in the framework. One type, the BC type (Im3m), comprising the compounds for which M(2+) = Ca(2+), Mn(2+), Cu(2+), and Cd(2+), has a body-centered cubic unit cell, while the second type, the FC type (Fd3c), for which M(2+) = Mg(2+), Fe(2+), Co(2+), Ni(2+), and Zn(2+), has a face-centered cubic unit cell with edges on the order of twice those of the BC structural type. The metal M in the BC structures has four close carbonate oxygen donors and four other more distant ones, while M in the FC structures has an octahedral environment consisting of two bidentate chelating carbonate ligands and two cis monodentate carbonate ligands.     

Aldimines generated from aza-Wittig reaction between bis(iminophosphoranes) derived from 1,1'-diazidoferrocene and aromatic or heteroaromatic aldehydes: electrochemical and optical behaviour towards metal cations

Aldimine 4 bearing a 2-quinolyl group was prepared by aza-Wittig reaction between the triphenyliminophosphorane derived from the 1,1'-diazidoferrocene and 2-formylquinoline. However, aldimine 5, bearing a pyrene ring, was prepared using the most reactive tributyliminophosphorane derivative and the corresponding 1-formylpyrene. On the other hand, formation of aldimine 8 involves a tandem process, Staudinger reaction/intramolecular aza-Wittig reaction, by using directly 1,1'-diazidoferrocene and 2-(diphenylphosphonyl)benzaldehyde. Aldimine 4 behaves as chemosensor molecule for Ni(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+) cations through two different channels: electrochemical (ΔE(1/2) = 222-361 mV) and chromogenic (Δλ = 122-153 nm), which can be used for the "naked eye" detection of these metal cations. Aldimine 5 behaves as a highly selective redox (in CH(3)CN) and fluorescent (in CH(3)Cl-DMF) probe for Hg(2+) metal cations even in the presence of a large excess of the other metal cations tested. Aldimine 8 displays electrochemical affinity (ΔE(1/2) = 60-288 mV) to Li(+), Ca(2+), Mg(2+), Zn(2+) and Pb(2+) metal cations, with the phosphorus oxide functionality as a binding site. From the (1)H NMR titration data as well as DFT calculations, different tentative binding modes have been established, for these structurally related ferrocenyl derivatives.     

含酚醚中心功能基开链冠醚的合成及其配位性能的研究

4-氯-2,6-二羟甲基笨甲醚与氯乙酸钠缩合,制得4-氯-2,6-双(羧甲氧基甲基)笨甲醚,此关键中间体经酰氯化后再与相应的胺反应,制备了含酚醚中心功能的4a-g。用紫外光谱法,考查了它们对NiCl_2、ZnCl_2、CdCl_2、CoCl_2和HgCl_2的配位性能。结果表明,它们对Ni~(2+)和Co~(2+)有较强的配合能力,其中又以4g为最好。