Construction of 0D to 3D cadmium complexes from different pyridyl diimide ligands

Four semirigid ditopic ligands, N,N'-bis(3-pyridylmethyl)-pyromellitic diimide (L(1)), N,N'-bis(4-pyridylmethyl)-pyromellitic diimide (L(2)), N,N'-bis(3-pyridylmethyl)-naphthalene diimide (L(3)), and N,N'-bis(4-pyridylmethyl)-naphthalene diimide (L(4)), reacted with Cd(NO(3))(2) to result in four cadmium(II) complexes, namely, {[Cd(2)(L(1))(2)(NO(3))(4)(CH(3)OH)(4)]·H(2)O} (1), [Cd(L(2))(NO(3))(2)(CH(3)OH)(2)·Cd(2)(L(2))(3)(NO(3))(4)]·{4(HCCl(3))·2H(2)O}(n) (2), {[Cd(L(3))(2)(NO(3))(2)]}(n) (3), and {[Cd(L(4))(2)(NO(3))(2)]·2(CHCl(3))}(n) (4). These complexes have been characterized by elemental analyses, powder X-ray diffraction, thermogravimetric (TG) analyses, IR spectroscopy, and single-crystal X-ray diffraction. Structural analyses show that four types of structures are formed: (1) a discrete M(2)L(2) ring with two Cd ions and two cis-L(1) ligands comprising a zero-dimensional molecular rectangle (0D), (2) an unusual zigzag linear chain and a one-dimensional ladder existing simultaneously in the crystal lattice (1D), (3) a two-dimensional network of the (4,4) net structure (2D), and (4) an unusual chiral three-dimensional framework with 5-fold interpenetrating diamond (dia) topology (3D). In these complexes, the ligands exhibit different coordination modes and construct various architectures by bridging Cd(NO(3))(2) inorganic building blocks. These results suggest that structural diversity of the complexes is tunable by ligand modifications, that is, varying the ligand spacer bulkiness or substituent position of terminal group. Furthermore, gas adsorption measurements indicate that 4 possesses moderate CO(2) uptake and some adsorption selectivity for CO(2) over N(2).     

Structure-based description of a step-by-step synthesis of homo- and heterodinuclear (4f, 4f ') lanthanide complexes

The stepwise course of the synthesis of homo- (4f, 4f) and heterodilanthanide (4f, 4f ') complexes has been investigated through structural determination of the intermediate and final products occurring in the process. In the first step, the tripodal ligand H(3)L is reacted with Ln(NO(3))(3) x 5H(2)O to give a complex (H(3)L)Ln(NO(3))(3) in which the ligand does exist in a zwitterionic form. This unexpected feature has been definitely supported by a structural determination performed on a closely related complex (HL')(3)Ln(NO(3))(3) (1). These species are fairly stable and may be isolated. In basic medium, (H(3)L)Ln(NO(3))(3) is deprotonated to yield a neutral LLn complex crystallized as LLnNaClO(4) (2), the lanthanide ion being linked to the inner N(4)O(3) coordination site of the ligand. Finally, addition of Ln'(NO(3))(3) x 5H(2)O (Ln' being similar or different from Ln) to the LLn complex yields the desired homo- or heterodinuclear LLnLn'(NO(3))(3) complex 3, where the Ln' ion is coordinated to the outer O(3)O(3) coordination site of the tripodal ligand. Complex 1 (Ln = La) crystallizes in the triclinic space group P1 (No. 2): a = 11.1883(7) A, b = 11.8993(9) A, c = 16.4197(10) A, alpha = 81.900 (6) degrees, beta = 79.406(5) degrees, gamma = 79.470(6) degrees, V = 2099.5(2) A(3), Z = 2. Complex 2 (Ln = Eu) crystallizes in the monoclinic space group P2(1)/n (No. 14): a = 13.6333(13) A, b = 15.3799(12) A, c = 17.1473(13) A, beta = 111.283(10) degrees, V = 3350.2(5) A(3), Z = 4. Complex 3 (Ln = Ln' = Dy) crystallizes in the trigonal space group R3 (No. 148) with a = b = 23.847(3) A, c = 42.982(2) A, V = 21168(4) A(3), Z = 18. Complex 3 possesses a Dy(O(phenoxo))(3)Dy core, and a nitrato anion has been replaced by a eta(2)-chelated o-vanillin anion. We did not succeed in obtaining crystals of any of the heterodinuclear LLnLn'(NO(3))(3) entities, but their existence was unambiguously confirmed by positive fast atom bombardment mass spectrometry experiments.     

Gravimetric determination of cadmium with N-phenylbenzohydroxamic acid

A quantitative gravimetric determination of cadmium in presence of Ag(+), Be(2+), Pb(2+), Mn(2+), Ni(2+), Cu(2+), Zn(2+), Hg(2+), Pd(2+), Ga(3+), Al(3+), Bi(3+), Sb(3+), La(3+), Ti(4+), Zr(4+), V(5+), Mo(6+) and U(6+) was made by selective precipitation with N-phenylbenzohydroxamic acid from a solution containing 6-15 mg of cadmium acetate at pH 5.8-6.5. The precipitate was weighed directly after drying at 110-120 degrees . The cadmium complex is curdy white, granular and melts at 225 degrees. The analytical results indicate the complex to be (C(13)H(10)NO(2))(2)Cd.     

Anion-directed formation and degradation of an interlocked metallohelicate

Although there are many examples of catenanes, those of more complex mechanically interlocked molecular architectures are rare. Additionally, little attention has been paid to the degradation of such interlocked systems into their starting complexes, although formation and degradation are complementary phenomena and are equally important. Interlocked metallohelicate, [(Pd(2)L(4))(2)](8+) (2(8+)), is a quadruply interlocked molecular architecture consisting of two mechanically interlocked monomers, [Pd(2)L(4)](4+) (1(4+)). 2(8+) has three internal cavities, each of which encapsulates one NO(3)(-) ion (1:3 host-guest complex, 2?(NO(3)|NO(3)|NO(3))(5+)) and is characterized by unusual thermodynamic stability. However, both the driving force for the dimerization and the origin of the thermodynamic stability remain unclear. To clarify these issues, BF(4)(-), PF(6)(-), and OTf(-) have been used to demonstrate that the dimerization is driven by the anion template effect. Interestingly, the stability of 2(8+) strongly depends on the encapsulated anions (2?(NO(3)|NO(3)|NO(3))(5+) ? 2?(BF(4)|BF(4)|BF(4))(5+)). The origins of this differing thermodynamic stability have been shown through detailed investigations to be due to the differences in the stabilization of the interlocked structure by the host-guest interaction and the size of the anion. We have found that 2-naphthalenesulfonate (ONs(-)) induces the monomerization of 2?(NO(3)|NO(3)|NO(3))(5+) via intermediate 2?(ONs|NO(3)|ONs)(5+), which is formed by anion exchange. On the basis of this finding, and using p-toluenesulfonate (OTs(-)), the physical separation of 2?(NO(3)|NO(3)|NO(3))(5+) and 1(4+) as OTs(-) salt was accomplished.     

Synthesis and coordination chemistry of two N2-donor chelating di(indazolyl)methane ligands: structural characterization and comparison of their metal chelation aptitudes

The N(2)-donor bidentate ligands di(1H-indazol-1-yl)methane (L(1)) and di(2H-indazol-2-yl)methane (L(2)) (L in general) have been synthesized, and their coordination behavior toward Zn(II), Cd(II), and Hg(II) salts has been studied. Reaction of L(1) and L(2) with ZnX(2) (X = Cl, Br, or I) yields [ZnX(2)L] species (1-6), that, in the solid state, show a tetrahedral structure with dihapto ligand coordination via the pyrazolyl arms. The reaction of L(1) and L(2) with Zn(NO(3))(2)·6H(2)O is strongly dependent on the reaction conditions and on the ligand employed. Reaction of L(1) with equimolar quantities of Zn(NO(3))(2)·6H(2)O yields the neutral six-coordinate species [Zn(NO(3))(2)(L(1))], 7. On the other hand the use of L(1) excess gives the 2:1 adduct [Zn(NO(3))(2)(L(1))(2)], 8 where both nitrates act as a unidentate coordinating ligand. Analogous stoichiometry is found in the compound obtained from the reaction of L(2) with Zn(NO(3))(2)·6H(2)O which gives the ionic [Zn(NO(3))(L(2))(2)](NO(3)), 10. Complete displacement of both nitrates from the zinc coordination sphere is observed when the reaction between L(1) excess and the zinc salt was carried out in hydrothermal conditions. The metal ion type is also determining structure and stoichiometry: the reaction of L(2) with CdCl(2) gave the 2:1 adduct [CdCl(2)(L(2))(2)] 11 where both chlorides complete the coordination sphere of the six-coordinate cadmium center; on the other hand from the reaction of L(1) with CdBr(2) the polynuclear [CdBr(2)(L(1))](n) 12 is obtained, the Br(-) anion acting as bridging ligands in a six-coordinate cadmium coordination environment. The reaction of L(1) and L(2) with HgX(2) (X = Cl, I, SCN) is also dependent on the reaction conditions and the nature of X, two different types of adducts being formed [HgX(L)] (14: L = L(1), 16, 17: L = L(1) or L(2), X = I, 19: L = L(2), X = SCN) and [HgX(L)(2)] (15: L = L(2), X = Cl, 18: L = L(1), X = SCN). The X-ray diffraction analyses of compounds 1, 2, 4, 5, 7, 8, 10-12, 14, 15, and 19 are also reported. The variations of the coordination geometry parameters in the complexes are compared and discussed.     

Sensitive stripping voltammetry of heavy metals by using a composite sensor based on a built-in bismuth precursor

A new graphite-epoxy composite electrode (GECE) containing Bi(NO(3))(3) as a built-in bismuth precursor for simultaneous and individual anodic stripping analysis of heavy trace metals like lead and cadmium is reported. The developed Bi(NO(3))(3)-GECE is compatible with bismuth film electrodes reported previously including the composite electrodes (Bi-GECE) recently reported by our group. Bi(NO(3))(3)-GECE displays the ability for the detection of both individual and simultaneous determination of heavy trace metals and exhibits well defined, reproducible and sharp stripping signals. The sensitive response is combined with the minimal toxicity of Bi(NO(3))(3). This novel sensor would be an appropriate alternative tool to sensors using bismuth in solution during their utilization in environmental quality monitoring as well as other applications.     

Determination of cadmium and copper with ET-AAS after electrochemical deposition on a graphite electrode

The electrodeposition of cadmium and copper on a special graphite disk electrode has been performed at controlled potential. The electrode with the deposit has been inserted into the graphite atomizer HGA-400 by an adapted automatic sampler for the final determination by ET-ASS. The sensitivity of determination has been 0.371 (microg l(-1))(-1) for cadmium and 0.025 (microg l(-1))(-1) for copper for 2 min electrodeposition and increased linearly with the time of deposition. The limit of detection (3s(bl)) has been 7.9 ng l(-1) Cd(2+) and 0.11 microg l(-1) Cu(2+) for 2 min deposition and it has been improved with increased time of electrodeposition. The technique has been applied to the determination of both metals in seawater and to speciation in the presence of EDTA complexing agent.     

Syntheses, Structures, and Steady State and Time Resolved Photophysical Properties of a Tetraiminodiphenol Macrocyclic Ligand and Its Dinuclear Zinc(II)/Cadmium(II) Complexes with Coordinating and Noncoordinating Anions

The work in the present investigation reports the syntheses, structures, steady state, and time-resolved photophysical properties of a tetraiminodiphenol macrocyclic ligand H(2)L and its eight dinuclear zinc(II) complexes and one cadmium(II) complex having composition [Zn(2)L(H(2)O)(2)](ClO(4))(2)·2CH(3)CN (1), [Zn(2)L(H(2)O)(2)](ClO(4))(2)·2dmf (2), [Zn(2)L(H(2)O)(2)](NO(3))(2)·2dmf (3), [Zn(2)LCl(2)] (4), [Zn(2)L(N(3))(2)] (5), [Zn(2)L(NCS)(2)] (6), [Zn(2)L(NCO)(2)] (7), [Zn(2)L(NCSe)(2)](2)·dmf (8), and [Cd(2)L(OAc)(2)] (9) with various coordinating and noncoordinating anions. The structures of all the complexes 1-9 have been determined by single-crystal X-ray diffraction. The noncovalent interactions in the complexes result in the generation of the following topologies: two-dimensional network in 1, 2, 4, 6, 7, 8, and 9; three-dimensional network in 5. Spectrophotometric and spectrofluorometric titrations of the diprotonated salt [H(4)L](ClO(4))(2) with triethylamine as well as with zinc(II) acetate and cadmium(II) acetate have been carried out, revealing fluorescence enhancement of the macrocyclic system by the base and the metal ions. Steady state fluorescence properties of [H(4)L](ClO(4))(2) and 1-9 have been studied and their quantum yields have been determined. Time resolved fluorescence behavior of [H(4)L](ClO(4))(2) and the dizinc(II) and dicadmium(II) complexes 1-9 have also been studied, and their lifetimes and radiative and nonradiative rate constants have been determined. The induced fluorescence enhancement of the macrocycle by zinc(II) and cadmium(II) is in line with the greater rate of increase of the radiative rate constants in comparison to the smaller rate of increase of nonradiative rate constants for the metal complexes. The fluorescence decay profiles of all the systems, being investigated here, that is, [H(4)L](ClO(4))(2) and 1-9, follow triexponential patterns, revealing that at least three conformers/components are responsible to exhibit the fluorescence decay behavior. The systems and studies in this report have been compared with those in the reports of the previously published similar systems, revealing some interesting aspects.     

A ruthenium nitrosyl that rapidly delivers NO to proteins in aqueous solution upon short exposure to UV light

Two Ru(III) complexes, [Ru(PaPy(3))(Cl)](BF(4)) (2) and [Ru(PaPy(3))(NO)](BF(4))(2) (3) (PaPy(3)H = N,N'-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-carboxamide), have been synthesized and characterized by spectroscopy and X-ray diffraction. Nitrosyl complex 3 has been prepared by passage of purified NO gas to the hot methanolic solution of the chloro derivative 2. Complex 3 exhibits nu(NuOmicron) stretching frequency at 1899 cm(-)(1) indicating a [Ru-NO](6) configuration. Clean (1)H NMR spectra of 3 in D(2)O and CD(3)CN confirm the S = 0 ground state. When an aqueous solution of [Ru(PaPy(3))(NO)](BF(4))(2) is exposed to low intensity UV light, it rapidly loses NO and forms [Ru(PaPy(3))(H(2)O)](2+). This reaction can be conveniently used to transfer NO to proteins such as myoglobin (Mb) and cytochrome c oxidase. The NO transfer reaction is clean and occurs upon short exposure to light.     

Thermal activation of hydrocarbon C-H bonds by tungsten alkylidene complexes.

Thermal activation of CpW(NO)(CH(2)CMe(3))(2) (1) in neat hydrocarbon solutions transiently generates the neopentylidene complex, CpW(NO)(=CHCMe(3)) (A), which subsequently activates solvent C-H bonds. For example, the thermolysis of 1 in tetramethylsilane and perdeuteriotetramethylsilane results in the clean formation of CpW(NO)(CH(2)CMe(3))(CH(2)SiMe(3)) (2) and CpW(NO)(CHDCMe(3))[CD(2)Si(CD(3))(3)] (2-d(12)), respectively, in virtually quantitative yields. The neopentylidene intermediate A can be trapped by PMe(3) to obtain CpW(NO)(=CHCMe(3))(PMe(3)) in two isomeric forms (4a-b), and in benzene, 1 cleanly forms the phenyl complex CpW(NO)(CH(2)CMe(3))(C(6)H(5)) (5). Kinetic and mechanistic studies indicate that the C-H activation chemistry derived from 1 proceeds through two distinct steps, namely, (1) rate-determining intramolecular alpha-H elimination of neopentane from 1 to form A and (2) 1,2-cis addition of a substrate C-H bond across the W=C linkage in A. The thermolysis of 1 in cyclohexane in the presence of PMe(3) yields 4a-b as well as the olefin complex CpW(NO)(eta(2)-cyclohexene)(PMe(3)) (6). In contrast, methylcyclohexane and ethylcyclohexane afford principally the allyl hydride complexes CpW(NO)(eta(3)-C(7)H(11))(H) (7a-b) and CpW(NO)(eta(3)-C(8)H(13))(H) (8a-b), respectively, under identical experimental conditions. The thermolysis of 1 in toluene affords a surprisingly complex mixture of six products. The two major products are the neopentyl aryl complexes, CpW(NO)(CH(2)CMe(3))(C(6)H(4)-3-Me) (9a) and CpW(NO)(CH(2)CMe(3))(C(6)H(4)-4-Me) (9b), in approximately 47 and 33% yields. Of the other four products, one is the aryl isomer of 9a-b, namely, CpW(NO)(CH(2)CMe(3))(C(6)H(4)-2-Me) (9c) ( approximately 1%). The remaining three products all arise from the incorporation of two molecules of toluene; namely, CpW(NO)(CH(2)C(6)H(5))(C(6)H(4)-3-Me) (11a; approximately 12%), CpW(NO)(CH(2)C(6)H(5))(C(6)H(4)-4-Me) (11b; approximately 6%), and CpW(NO)(CH(2)C(6)H(5))(2) (10; approximately 1%). It has been demonstrated that the formation of complexes 10 and 11a-b involves the transient formation of CpW(NO)(CH(2)CMe(3))(CH(2)C(6)H(5)) (12), the product of toluene activation at the methyl position, which reductively eliminates neopentane to generate the C-H activating benzylidene complex CpW(NO)(=CHC(6)H(5)) (B). Consistently, the thermolysis of independently prepared 12 in benzene and benzene-d(6) affords CpW(NO)(CH(2)C(6)H(5))(C(6)H(5)) (13) and CpW(NO)(CHDC(6)H(5))(C(6)D(5)) (13-d(6)), respectively, in addition to free neopentane. Intermediate B can also be trapped by PMe(3) to obtain the adducts CpW(NO)(=CHC(6)H(5))(PMe(3)) (14a-b) in two rotameric forms. From their reactions with toluene, it can be deduced that both alkylidene intermediates A and B exhibit a preference for activating the stronger aryl sp(2) C-H bonds. The C-H activating ability of B also encompasses aliphatic substrates as well as it reacts with tetramethylsilane and cyclohexanes in a manner similar to that summarized above for A. All new complexes have been characterized by conventional spectroscopic methods, and the solid-state molecular structures of 4a, 6, 7a, 8a, and 14a have been established by X-ray diffraction methods.     

Electrochemical characterization of boron-doped polycrystalline diamond thin-film electrodes

The electrochemical characterization of boron-doped polycrystalline diamond thin-film (BDF) electrodes was studied using the anodic scan after concentrating lead in 0.1 mol/L KCl - 41 micromol/L Hg(NO(3))(2) and 0.1 mol/L KNO(3) - 0.01 mol/L HNO(3) - 41 micromol/L Hg(NO(3))(2); accumulation voltage was -0.90 V. The results obtained were compared with those given by glassy carbon (GC) electrodes and proved that the BDF electrodes offered high sensitivity, good precision and extreme stability over a 2-month period. These electrodes provided good resolving power for the determination of lead and cadmium and gave satisfactory results in the analysis of a pure water sample.     

Open-framework cadmium succinates of different dimensionalities

Open-framework cadmium succinates, [CN(3)H(6)](2)[Cd(2)(C(4)H(4)O(4))(Cl)(2)], I; [CN(3)H(6)](2)[Cd(C(4)H(4)O(4))(2)], II; Cd(2)(C(4)H(4)O(4))(2)(C(4)N(2)H(8))(H(2)O)(3), III; [C(4)N(2)H(12)][Cd(2)(C(4)H(4)O(4))(3)].4H(2)O, IV; Cd(C(4)H(4)O(4))(H(2)O)(2), V; and Cd(3)(C(4)H(4)O(4))(2)(OH)(2)], VI, of different dimensionalities have been synthesized by hydrothermal procedure by employing two different strategies, one involving the reaction of Cd salts with organic-amine succinates and the other involving the hydrothermal reaction of Cd salts with a mixture of succinic acid and the organic amine. While the latter procedure yields structures without any amine in them, the former gives rise to amine templated cadmium succinates with open architectures. By employing guanidinium succinate we have obtained I and II, and with piperazinium succinate we obtained III and IV. Of these I has a one-dimensional chain structure, IV has a layered structure, and II and III have three-dimensional architectures. The two cadmium succinates without incorporation of amine, V and VI, possess layered and three-dimensional structures, respectively. The three-dimensional structures II and III exhibit interpenetration similar to that in diamondoid and alpha-polonium type structures, respectively.     

Synthesis and characterization of new five-coordinate platinum nitrosyl derivatives: density functional theory study of their electronic structure

The neutral, five-coordinate platinum nitrosyl compounds [Pt(C(6)F(5))(3)(L)(NO)] (2) [L=CNtBu (2 a), NC(5)H(4)Me-4 (2 b), PPhMe(2) (2 c), PPh(3) (2 d) and tht (2 e)] have been prepared by the reaction of [NBu(4)][Pt(C(6)F(5))(3)(L)] (1) with NOClO(4) in CH(2)Cl(2). The ionic compound [N(PPh(3))(2)][Pt(C(6)F(5))(4)(NO)] (4) has been prepared in a similar way starting from the homoleptic species [N(PPh(3))(2)](2)[Pt(C(6)F(5))(4)] (3). Compounds 2 and 4 are all diamagnetic with [PtNO](8) electronic configuration and show nu(NO) stretching frequencies at around 1800 cm(-1). The crystal and molecular structures of 2 c and 4 have been established by X-ray diffraction methods. The coordination environment for the Pt center in both compounds can be described as square pyramidal (SPY-5). Bent nitrosyl coordination is observed in both cases with Pt-N-O angles of 120.1(6) and 130.2(7) degrees for 2 c and 4, respectively. The bonding mechanism of the nitrosyl ligand coordinated to various model [Pt(II)R(4)](2-) (R=H, Me, Cl, CN, C(6)F(5) or C(6)Cl(5)) and [Pt(C(6)F(5))(3)(L)](-) (L=CNMe, PH(3)) systems has been studied by density functional calculations at the B3LYP level of theory, using the SDD basis set. The R(4)Pt-NO and (C(6)F(5))(3)(L)Pt-NO interactions generally involve two components: i) a direct Pt-NO bonding interaction and ii) multicenter-bonding interactions between the N atom of the NO ligand and the donor atoms of the R and L ligands. Moreover, with the more complex R groups, C(6)F(5) or C(6)Cl(5), a third component has been found to arise, which involves multicenter electrostatic interactions between the positively charged NO ligand and the negatively charged halo-substituents in the ortho-position of the C(6)X(5) groups (X=F, Cl). The contribution of each component to the Pt-NO bonding in R(4)Pt-NO and (C(6)F(5))(3)(L)Pt-NO compounds seems to be modulated by the electronic and steric effects of the R and L ligands.     

The reaction of Li[Al(OR)4] R = OC(CF3)2Ph, OC(CF3)3 with NO/NO2 giving NO[Al(OR)4], Li[NO3] and N2O. The synthesis of NO[Al(OR)4] from Li[Al(OR)4] and NO[SbF6] in sulfur dioxide solution

NO[Al(OC(CF(3))(2)Ph)(4)] 1 and NO[Al(OC(CF(3))(3))(4)] 2 were obtained by the metathesis reaction of NO[SbF(6)] and the corresponding Li[Al(OR)(4)] salts in liquid sulfur dioxide solution in ca 40% (1) and 85% (2) isolated yield. 1 and 2, as well as Li[NO(3)] and N(2)O, were also given by the reaction of an excess of mixture of (90 mol%) NO, (10 mol%) NO(2) with Li[Al(OR)(4)] followed by extraction with SO(2). The unfavourable disproportionation reaction of 2NO(2)(g) to [NO](+)(g) and [NO(3)](-)(g)[DeltaH degrees = +616.2 kJ mol(-1)] is more than compensated by the disproportionation energy of 3NO(g) to N(2)O(g) and NO(2)(g)[DeltaH degrees =-155.4 kJ mol(-1)] and the lattice energy of Li[NO(3)](s)[U(POT)= 862 kJ mol(-1)]. Evidence is presented that the reaction proceeds via a complex of [Li](+) with NO, NO(2)(or their dimers) and N(2)O. NO(2) and Li[Al(OC(CF(3))(3))(4)] gave [NO(3)(NO)(3)][Al(OC(CF(3))(3))(4)](2), NO[Al(OC(CF(3))(3))(4)] and (NO(2))[Al(OC(CF(3))(3))(4)] products. The aluminium complex [Li[AlF(OC(CF(3))(2)Ph)(3)]](2) 3 was prepared by the thermal decomposition of Li[Al(OC(CF(3))(2)Ph)(4)]. Compounds 1 and 3 were characterized by single crystal X-ray structural analyses, 1-3 by elemental analyses, NMR, IR, Raman and mass spectra. Solid 1 contains [Al(OC(CF(3))(2)Ph)(4)](-) and [NO](+) weakly linked via donor acceptor interactions, while in the SO(2) solution there is an equilibrium between the associated [NO](+)[Al(OC(CF(3))(2)Ph)(4)](-) and separated solvated ions. Solid 2 contains essentially ionic [NO](+) and [Al(OC(CF(3))(3))(4)](-). Complex 3 consists of two [Li[AlF(OC(CF(3))(2)Ph)(3)]] units linked via fluorine lithium contacts. Compound 1 is unstable in the SO(2) solution and decomposes to yield [AlF(OC(CF(3))(2)Ph)(3)](-), [(PhC(CF(3))(2)O)(3)Al(mu-F)Al(OC(CF(3))(2)Ph)(3)](-) anions as well as (NO)C(6)H(4)C(CF(3))(2)OH, while compound 2 is stable in liquid SO(2). The [small nu](NO(+)) in 1 and [NO](+)(toluene)[SbCl(6)] are similar, implying similar basicities of [Al(OC(CF(3))(2)Ph)(4)](-) and toluene.     

Luminescent complexes of silver(I) with pyridylbis(3-hexamethyleneiminyl thiosemicarbazone): effect of the counterion on the nuclearity

The reaction of pyridylbis(3-hexamethyleneiminyl thiosemicarbazone) (H(2)Plhexim) with various silver(I) salts and metal-ligand ratios led to the isolation of different complexes of the formulae [Ag(NO(3))(H(2)Plhexim)]·H(2)O (1), [Ag(2)(NO(3))(H(2)Plhexim)(CH(3)OH)](NO(3)) (2), [Ag(2)(ClO(4))(2)(H(2)Plhexim)] (3), [Ag(HPlhexim)]·xH(2)O (4), [Ag(HPlhexim)] (4a), [Ag(2)(Plhexim)(PPh(3))(4)]·2MeOH (5) and [Ag(4)(Plhexim)(2)]·DMF (6). The complexes were fully characterized by elemental analysis, ESI mass spectrometry, IR and NMR ((1)H, (31)P) spectroscopy. The structures of 4a, 5 and 6 were also identified by single crystal X-ray structure determination. The concentration dependence on the absorption spectra of the methanolic solutions indicates polymerization equilibria in the ground state in both the ligand and the complexes. While H(2)Plhexim is essentially non-fluorescent, complexes 1-5 fluoresce more strongly by comparison. This fluorescent behavior is consistent with the monomeric or dimeric nature of the complexes.     

Thermodynamic study on the complexation of Am(III) and Eu(III) with tetradentate nitrogen ligands: a probe of complex species and reactions in aqueous solution

A thermodynamic investigation has been performed to study the complexation of trivalent metal (M) ions (M = Am(III), Eu(III)) with tetradentate ligands (L), 6,6'-bis(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2'-bipyridines (BTBPs), by using relativistic quantum mechanical calculations. The structures and stabilities of the inner-sphere BTBPs complexes were explored in the presence of various counterions such as NO(3)(-), Cl(-), and ClO(4)(-). According to our calculations, Am(III) and Eu(III) can chelate eight or nine water molecules at most, whereas more stable species like M(NO(3))(3)(H(2)O)(4) tend to be formed in the presence of nitrate ions. The inner sphere of the BTBPs complexes can accommodate four water molecules or three nitrate ions based on our calculations, forming species such as [ML(H(2)O)(4)](3+) and ML(NO(3))(3). Compared with Eu(III) complexes, the Am(III) counterparts have obviously lower binding energies in both the gas phase and solution. In addition, the solvent effect significantly decreases the binding energies of the BTBPs complexes. It has been found that the complexing reactions, in which products and reactants possess the same or close number of nitrate ions, are more favorable for formation of the BTBPs complexes. In short, the reactions of M(NO(3))(3)(H(2)O)(4) → ML(NO(3))(3) and [M(NO(3))(H(2)O)(7)](2+) → [ML(2)(NO(3))](2+) are probably the dominant ones in the Am(III)/Eu(III) separation process.     

Separation and preconcentration of trace amounts of several metals in magnesium metal and nitrate, with activated carbon as a collector

A method is described for the preconcentration and determination of traces of Hg, Ag, Cu, Fe, In, Mn, Pb, and Zn present as impurities in magnesium metal (1 g) and nitrate (100 g). After the metal sample has been dissolved in nitric acid (or the salt in water) and the pH adjusted to 8.1-9 (except for preconcentration of Hg, when pH 3 is used), the solution is filtered through a 2-cm paper coated with 50 mg of activated carbon. The trace metals are quantitatively adsorbed on the activated carbon and separated from the matrix. The rest of the procedure has already been described. The detection limits for the analysis of 1 g of Mg and 100 g of Mg(NO(3))(2).6H(2)O are 0.03-1.3 ppm and 0.00031-0.013 ppm respectively, for all the trace metals except Hg. The limit is 0.00001(4) ppm for Hg in 100 g of Mg(NO(3))(2).6H(2)O. The coefficient of variation is 4-33%, depending on the trace metal.     

Moisture-triggered 1,3,5-triazine-based Cu(II) molecular switch: a combined X-ray single-crystal and powder diffraction study

A solvothermal synthetic procedure has been exploited to prepare the new [Cu(3)L(NO(3))(6)](n) coordination polymer (1) by reaction of the polydentate N,N'-{2,4-di-[(di-pyridin-2-yl)amine]-1,3,5-triazine}ethylenediamine ligand (opytrizediam L) with copper(II) nitrate. 1 has been structurally characterized by means of the conventional X-ray single-crystal diffraction technique. It crystallizes in the monoclinic C2/c space group with a = 16.830(3), b = 20.701(4), c = 18.170(4) Angstroms, beta = 113.26(3) degrees, V = 5816(2) Angstroms(3), Z = 4. 1 consists of trinuclear Cu(3)L(NO(3))(5) units connected by means of a nitrato-O,O' bridge. The resulting chains are involved in weak interchain head-to-tail pi-pi stacking interactions. In the presence of moisture, 1 is readily converted into the hydrated [Cu(3)L(NO(3))(5)](NO(3)).H(2)O form (2). This second phase, monoclinic P2(1)/c, consists of isolated [Cu(3)L(NO(3))(5)](+) and (NO(3))(-) ions which accommodate water molecules in the crystal lattice. These subtle chemical and structural modifications accompanying the moisture-triggered 1-to-2 transformation have been demonstrated through a X-ray powder diffraction study. A thermodiffractometric analysis has evidenced that this solid-to-solid transformation is fully reversible, i.e., thermally induced dehydration of 2 restores 1. The analysis of the temperature dependence of the magnetic susceptibility for 2 has revealed very weak ferromagnetic interactions, consistent with the large Cu...Cu separation (ca. 7.5 Angstroms) in the trinuclear units.     

Anion induced formation of supramolecular associations involving lone pair-π and anion-π interactions in Co(II) malonate complexes: experimental observations, Hirshfeld surface analyses and DFT studies

Three Co(II)-malonate complexes, namely, (C(5)H(7)N(2))(4)[Co(C(3)H(2)O(4))(2)(H(2)O)(2)](NO(3))(2) (1), (C(5)H(7)N(2))(4)[Co(C(3)H(2)O(4))(2)(H(2)O)(2)](ClO(4))(2) (2), and (C(5)H(7)N(2))(4)[Co(C(3)H(2)O(4))(2)(H(2)O)(2)](PF(6))(2) (3) [C(5)H(7)N(2) = protonated 2-aminopyridine, C(3)H(4)O(4) = malonic acid, NO(3)(-) = nitrate, ClO(4)(-) = perchlorate, PF(6)(-) = hexafluorophosphate], have been synthesized from purely aqueous media, and their crystal structures have been determined by single crystal X-ray diffraction. A thorough analysis of Hirshfeld surfaces and fingerprint plots facilitates a comparison of intermolecular interactions in 1-3, which are crucial in building supramolecular architectures. When these complexes are structurally compared with their previously reported analogous Ni(II) or Mg(II) compounds, a very interesting feature regarding the role of counteranions has emerged. This phenomenon can be best described as anion-induced formation of extended supramolecular networks of the type lone pair-π/π-π/π-anion-π/π-lone pair and lone pair-π/π-π/π-anion involving various weak forces like lone pair-π, π-π, and anion-π interactions. The strength of these π contacts has been estimated using DFT calculations (M06/6-31+G*), and the formation energy of the supramolecular networks has been also evaluated. The influence of the anion (NO(3)(-), ClO(4)(-), and PF(6)(-)) on the total interaction energy of the assembly is also studied.     

Experimental and theoretical studies of the vibrational and electronic spectra of a lanthanide ion at a site of T(h) symmetry: Pr3+ in Cs2NaPr(NO2)6

The Pr(3+) ion in Cs(2)NaPr(NO(2))(6) is situated at a site of T(h) symmetry with 12-coordination to O atoms of bidentate nitrito groups. First-principles calculations of the vibrational modes of the complex were carried out using the density functional theory with the generalized gradient approximation Perdew-Burke-Ernzerhof exchange-correlation functional. The calculations that treated the Pr(3+) 4f electrons as valence electrons showed better agreement with the experimental vibrational assignments compared with those treating the 4f electrons a part of the inner core. The (1)D(2) → (3)H(4) emission spectra of Cs(2)NaPr(NO(2))(6) at 7 K enabled assignments to be made for the crystal-field (CF) levels of the ground-state multiplet. The emission of the dilute system Cs(2)NaY(NO(2))(6):Pr(3+) was dominated by NO(2)(-) triplet emission, which was quenched at elevated temperatures by energy transfer to trace Eu(3+) impurity. From magnetic dipole calculations and the vibronic fingerprint, detailed assignments are given for the complex 10 K electronic absorption spectrum of Cs(2)NaPr(NO(2))(6) between 3940 and 18800 cm(-1), and the derived Pr(3+) 4f(2) energy-level data set has been fitted by calculation. By comparison with Cs(2)NaPrCl(6), the fourth-order CF parameter in Cs(2)NaPr(NO(2))(6) is relatively small so that interaction with a 4fnp configuration is not important. From the NO(2)(-) absorption bands above 20,000 cm(-1), the N-O bond length change upon excitation is small, whereas the angle O-N-O opens by more than 10° in the triplet state. By contrast to the NO(2)(-) internal vibration frequencies, which except for the wagging mode show only minor changes with the environment, the triplet-state energy shows a linear decrease with an increase of the lanthanide (Ln(3+)) ionic radius in Cs(2)NaLn(NO(2))(6). Using the eigenvectors from the energy-level fit, the variation of the inverse magnetic susceptibility with temperature has been calculated between 1 and 100 K and the values are somewhat lower than those from experiment.