Thermal and photochemical reduction of aqueous chlorine by ruthenium(II) polypyridyl complexes

Studies are reported on the reactions of aqueous chlorine with a series of substitution-inert, one-electron metal-complex reductants, which includes [Ru(bpy)3]2+, [Ru(4,4'-Me2bpy)3]2+, [Ru(4,7-Me2phen)3]2+, [Ru(terpy)2]2+, and [Fe(3,4,7,8-Me4phen)3]2+. The reactions were studied by spectrophotometry at 25 degrees C in acidic chloride media at mu = 0.3 M. In general the reactions have the stoichiometry 2[ML3]2+ + Cl2-->2[ML3]3+ + 2Cl-. In the case of [Ru(bpy)3]2+, the reaction is quite photosensitive; the thermal reaction is so slow as to be practically immeasurable. The reactions of [Ru(4,4'-Me2bpy)3]2+ and [Ru(4,7-Me2phen)3]2+ are also highly photosensitive, giving pseudo-first-order rate constants that depend on the monochromator slit width in a stopped-flow instrument; however, the thermal rates are fast enough that they can be obtained by extrapolation of kobs to zero slit width. The reactions of [Ru(terpy)2]2+ and [Fe(3,4,7,8-Me4phen)3]2+ show no appreciable photosensitivity, allowing direct determination of their thermal rate laws. From the kinetic effects of pH, [Cl2]tot, and [Cl-] it is evident that all of the thermal rate laws have a first-order dependence on [ML3]2+ and on [Cl2]. The second-order rate constants decrease as Eo for the complex increases, consistent with the predictions of Marcus theory for an outer-sphere electron-transfer mechanism. Quantum yields at 460 nm for the reactions of [Ru(4,4'-Me2bpy)3]2+ and [Ru(4,7-Me2phen)3]2+ exceed 0.1 and show a dependence on [Cl2] indicative of competition among spontaneous decay of *Ru, nonreactive quenching by Cl2, and reactive quenching by Cl2.     

Influence of steric confinement within zeolite Y on photoinduced energy transfer between [Ru(bpy)3]2+ and iron polypyridyl complexes

The spectroscopic and photophysical properties of zeolite-Y-entrapped [Ru(bpy)3]2+ co-doped with either [Fe(bpy)3]2+ or [Fe(tpy)2]2+ over a range of iron complex loadings are presented. In solution, [Ru(bpy)3]2+ undergoes efficient bimolecular energy transfer to [Fe(bpy)3]2+, whereas only radiative or trivial energy transfer occurs between [Ru(bpy)3]2+ and [Fe(tpy)2]2+. In sharp contrast, within zeolite Y, both [Fe(bpy)3]2+ and [Fe(tpy)2]2+ were found to effectively quench the donor emission. Fitting the Perrin model to the photophysical data yields an effective quenching radius of 32 and 27 A, respectively, for [Fe(bpy)3]2+ and [Fe(tpy)2]2+. The long-range nature of the quenching suggests F?rster energy transfer. Detailed spectroscopic investigations indicate that [Fe(tpy)2]2+ bound within zeolite Y undergoes significant distortion from octahedral geometry. This distortion results in increased oscillator strength and enhanced spectral overlap, between the [Ru(bpy)3]2+ (3)d pi-pi* donor emission and the co-incident acceptor (1)T2-(1)A1 ligand field absorption compared with solution. This turns on an efficient energy transfer to [Fe(tpy)2]2+ within the confinement of the zeolite Y supercage. Overall, this is an interesting example of the ability of the zeolite environment to provoke new photophysical processes not possible in solution.     

Simultaneous determination of stable isotopically labelled L-histidine and urocanic acid in human plasma by stable isotope dilution mass spectrometry.

A capillary gas chromatographic-mass spectrometric method for the simultaneous determination of stable isotopically labelled L-histidine (L-[3,3-2H2,1',3'-15N2]histidine, L-His-[M + 4]) and urocanic acid ([3-2H,1',3'-15N2]urocanic acid, UA-[M + 3]) in human plasma was developed using DL-[2,3,3,5'-2H4,2'-13C,1',3'-15N2]histidine (DL-His-[M + 7]) and [2,3,5'-2H3,2'-13C,1',3'-15N2]urocanic acid (UA-[M + 6]) as internal standards. L-Histidine and urocanic acid were derivatized to alpha N-(trifluoroacetyl)-imN-(ethoxycarbonyl)-L-histidine n-butyl ester and imN-(ethoxycarbonyl)urocanic acid n-butyl ester. Quantification was carried out by selected ion monitoring of the molecular ions of the respective derivatives of L-His-[M + 4], DL-His-[M + 7], UA-[M + 3] and UA-[M + 6]. The sensitivity, specificity, precision and accuracy of the method were demonstrated to be satisfactory for measuring plasma concentrations of L-His-[M + 4] and UA-[M + 3] following administration of trace amounts of L-His-[M + 4] to humans.     

Synthesis, characterization, and chiral properties of CoIII2AgI3 pentanuclear, CoIII4ZnII4 octanuclear, and CoIII mononuclear complexes with aza-capped hexadentate-N3S3 thiolate ligands: crystal structures of

The reaction of an S-bridged Co2(III)Ag3(I) pentanuclear complex, [Ag3[Co(aet)3]2][BF4]3 (aet = NH2CH2CH2S-), with paraformaldehyde in basic acetonitrile, followed by adding aqueous ammonia, produced an aza-capped Co2(III)-Ag3(I) complex, [Ag3[Co(L)]2]3+ ([1]3+) (L = N(CH2NHCH2CH2S-)3). The crystal structure of [1]3+ was determined by X-ray crystallography. [1][PF6]3 x H2O, empirical formula C18H44Ag3Co2F18N8OP3S6, crystallizes in the tetragonal space group 142m with a = 13.012(1) A, c = 24.707(2) A, and Z = 4. In [1]3+ the two aza-capped [Co(L)] units are linked by three Ag(I) atoms, such that the two Co(III) atoms are encapsulated in a macrobicyclic metallocage, [Ag3(I)(L)2]3-. [1]3+ was converted to an aza-capped Co4(III)Zn4(II) octanuclear complex, [Zn4O[Co(L)]4]6+ ([2]6+), by reaction with I- in the presence of Zn2+ and ZnO in water. The crystal structure of [2]6+ was also determined by X-ray crystallography. [2][PF6]6 x 8H2O, empirical formula C36H100Co4F36N16O9P6S12Zn4, crystallizes in the monoclinic space group P2(1/n) with a = 14.33(7) A, b = 25.67(10) A, c = 24.83(6) A, beta = 101.3(3) degrees , and Z = 4. In [2]6+ each of four [Co(L)] units is bound to each trigonal Zn3(II) face of the tetrahedral [Zn4(II)O]6+ core, such that each Co(III) atom is encapsulated in a macrobicyclic [Zn4(II)O(L)] fragment. Treatment of [2]6+ with a basic aqueous solution resulted in a cleavage of the Zn-S bonds to produce an aza-capped Co(III) mononuclear complex, [Co(L)] ([3]), from which [1]3+ is readily reproduced by the reaction with Ag+ in water. All the reactions were found to proceed with retention of the absolute configuration (delta or lambda) of the Co(III) chiral centers; deltadelta-[1]3+, deltadeltadeltadelta-[2]6+, and A-[3] were derived from deltadelta-[Ag3[Co(aet)3]2]3+. The contributions to circular dichroism (CD) from the triple helicity in [1]3+, besides from the asymmetric N and S donor atoms and the Co(III) chiral centers in [1]3+ and [2]6+, were estimated by comparing the CD spectra of deltadelta-[1]3+, deltadeltadeltadelta-[2]6+, and delta-[3].     

Two stereoisomers of an S-bridged RhIII2PtII2 tetranuclear complex [{Pt(NH3)2}2{Rh(aet)3}2]4+ that lead to a discrete and a 1D RhIII2PtII2AgI structures by reacting with AgI (aet = 2-aminoethanethiolate)

An S-bridged RhIII2PtII2 tetranuclear complex having two nonbridging thiolato groups, [{Pt(NH3)2}2{Rh(aet)3}2]4+ ([1]4+), in which two fac(S)-[Rh(aet)3] units are linked by two trans-[Pt(NH3)2]2+ moieties, was synthesized by the 1:1 reaction of fac(S)-[Rh(aet)3] (aet = 2-aminoethanethiolate) with trans-[PtCl2(NH3)2] in water. Complex [1]4+ gave both the meso (DeltaLambda) and racemic (DeltaDelta/LambdaLambda) forms, which were separated by fractional crystallization. Of two possible geometries, syn and anti, which arise from the arrangement of two nonbridging thiolato groups, the meso and racemic forms of [1]4+ selectively afforded the anti and syn geometries, respectively. The DeltaLambda-anti and DeltaDelta/LambdaLambda-syn isomers of [1]4+ reacted with Ag+ using two nonbridging thiolato groups to produce a {RhIII2PtII2AgI}n) polymeric complex, {[Ag{Pt(NH3)2}2{Rh(aet)3}2]5+}n) ([2]5+), and a RhIII2PtII2AgI pentanuclear complex, [Ag{Pt2(mu-H2O)(NH3)2}{Rh(aet)3}2]5+ ([3]5+), respectively, which contain octahedral RhIII, square-planar PtII, and linear AgI centers. In [2]5+, each DeltaLambda-anti-[{Pt(NH3)2}2{Rh(aet)3}2]4+ tetranuclear unit is bound to two AgI atoms to form a one-dimensional zigzag chain, indicating the retention of the parental S-bridged structure in DeltaLambda-anti-[1]4+. In [3]5+, two Delta- or Lambda-fac(S)-[Rh(aet)3] units are linked by a [Pt2(mu-H2O)(NH3)2]4+ dinuclear moiety, together with an AgI atom, indicating that two NH3 molecules in [1]4+ have been replaced by a water molecule that bridges two PtII centers, while the parental DeltaDelta/LambdaLambda-syn configuration is retained. The complexes obtained were characterized on the basis of electronic absorption, CD, and NMR spectra, along with single-crystal X-ray analyses.     

Improved sensitivity for quantification of proteins using triply charged cleavable isotope-coded affinity tag peptides

Isotope-coded affinity tag (ICAT) methods, in conjunction with capillary liquid chromatography/tandem mass spectrometry (LC/MS/MS), represent a promising approach for accurate protein quantification. However, sensitivity remains a challenge for the quantification of low-copy proteins in complex biological matrices. Here we investigated the electrospray ionization (ESI) and collision-activated dissociation (CAD) behavior of peptides derivatized with the cleavable ICAT (cICAT) reagent. For cICAT-peptides that were either synthesized or obtained by digestion of model proteins, the cICAT moiety showed a tendency toward protonation under positive ESI, producing relatively intense triply charged cICAT-peptide ions ([IP+3H]3+). [IP+3H]3+ exhibited significantly higher CAD reactivity than did the doubly charged cICAT-peptide ([IP+2H]2+), and produced a greater abundance of fragments at lower collision energies. Fragmentation spectra of [IP+3H]3+ showed variable intensities of doubly charged y and b ions, and the amount of sequence information obtained was dependent on the position of the cICAT-labeled cysteine residue in the peptide sequence. However, the absolute abundances of major fragments of [IP+3H]3+ were much higher than for [IP+2H]2+. Although the efficiency of identification of cICAT-peptides was compromised by their charge distribution toward the triply charged state and by the unique CAD behavior of the [IP+3H]3+ ions, it was found that the triply charged ions provided higher sensitivity than [IP+2H]2+ for quantification using multiple reaction monitoring (MRM). ESI and CAD conditions for MRM of [IP+3H]3+ were optimized, and, for all cICAT-peptides studied, MRM using [IP+3H]3+ as precursors showed 2- to 8-fold higher sensitivity than obtained using [IP+2H]2+, without compromising quantitative accuracy. Using this approach, the time course of tyrosine aminotransferase induction by methylprednisolone was monitored in rat livers. A remarkably better signal-to-noise ratio was observed by using [IP+3H]3+ for quantification compared to [IP+2H]2+.     

Complex Salts Derived from the Reactions of Organotin(IV) with 6-Methylpyridine-2-Carboxaldehyde Phenylhydrazone: X-Ray Crystal Structure of BIS[6-Methylpyridine- 2-Carboxaldehydehydrazodium]- Tetrachlorodimethylstannate(IV)

Reactions of organotin(IV) chloride (Me 2 SnCl 2 , PhSnCl 3 and n -BuSnCl 3 ) with the Schiff base 6-methylpyridine-2-carboxaldehyde phenylhydrazone ( L ) result in the formation of organotin(IV) anionic complexes. Me 2 SnCl 2 reacts with L in dichloromethane to form [ L H + ] 2 [Me 2 SnCl 4 ] 2 m . X-ray structural analysis has been carried out on the complex salt bis[6-methylpyridine-2-carboxaldehydehydrazodium]tetra-chlorodimethylstannate(IV), [ L H + ] 2 [Me 2 SnCl 4 ] 2 m wherein the tin moieties exist as monomers. Reactions of PhSnC1 3 and n -BuSnCl 3 with L form the complexes [ L H + ] 2 [PhSnCl 5 ] 2 m and [ L H + ] 2 [ n- BuSnCl 5 ] 2 m . Compounds were also characterized by FTIR, 1 H and 13 C NMR spectroscopy.     

pH-dependent H2-activation cycle coupled to reduction of nitrate ion by CpIr complexes.

This paper reports a pH-dependent H2-activation [H2 (pH 1-4) --> H+ + H- (pH -1) --> 2H+ + 2e-] promoted by CpIr complexes [Cp = eta5-C5(CH3)5]. In a pH range of about 1-4, an aqueous HNO3 solution of [CpIr(III)(H2O)3]2+ (1) reacts with 3 equiv of H2 to yield a solution of [(CpIr(III))2(mu-H)3]+ (2) as a result of heterolytic H2-activation [2[1] + 3H2 (pH 1-4) --> [2] + 3H+ + 6H2O]. The hydrido ligands of 2 display protonic behavior and undergo H/D exchange with D+: [M-(H)3-M]+ + 3D+ <==>[M-(D)3-M]+ + 3H+ (where M = CpIr). Complex 2 is insoluble in a pH range of about -0.2 (1.6 M HNO3/H2O) to -0.8 (6.3 M HNO3/H2O). At pH -1 (10 M HNO3/H2O), a powder of 2 drastically reacts with HNO3 to give a solution of [CpIr(III)(NO3)2] (3) with evolution of H2, NO, and NO2 gases. D-labeling experiments show that the evolved H2 is derived from the hydrido ligands of 2. These results suggest that oxidation of the hydrido ligands of 2 [[2] + 4NO3- (pH -1) --> 2[3] + H2 + H+ + 4e-] couples to reduction of NO3- (NO3- --> NO2- --> NO). To complete the reaction cycle, complex 3 is transformed into 1 by increasing the pH of the solution from -1 to 1. Therefore, we are able to repeat the reaction cycle using 1, H2, and a pH gradient between 1 and -1. A conceivable mechanism for the H2-activation cycle with reduction of NO3- is proposed.     

Proton-induced cis-trans conversion of a platinum(II) center coordinated by L-cysteinatocobalt(III) metalloligands

Treatment of LambdaL-[Co(L-cys-N,S)(en)2]+ (l-H2cys = L-cysteine) with [PtCl4]2- in water, followed by the addition of acid, gave an S-bridged CoIII2PtII trinuclear complex ([1]4+), which was reversibly converted to its deprotonated complex ([2]2+) in an aqueous solution. While [1]4+ formed only a trans isomer, [2]2+ existed as a mixture of trans and cis isomers. The selective formation of a cis isomer was achieved by treatment of [1]4+ or [2]2+ with phthalic acid in water, which afforded a unique CoIII4PtII2 hexanuclear complex ([3]4+). Complex [3]4+ was reverted back to [1]4+ by treatment with aqueous HCl, accompanied by the complete cis-to-trans conversion.     

Cobalt(I)-catalyzed [6+2] cycloadditions of cyclooctatetra(tri)ene with alkynes

The cobalt-catalyzed [6+2] cycloaddition of cyclooctatetraene 1 with alkynes 3 affords monosubstituted bicyclo[4.2.2]deca-2,4,7,9-tetraenes 4 in fair to good yields. Due to the valence tautomerism, 1,3,5-cyclooctatriene 2, in equilibrium with bicyclo[4.2.0]octa-2,4-diene A, and alkynes 3 are converted to 10 and 11 according to [6+2] and [4+2] cycloadditions, respectively.     

Hetero [6+3] cycloaddition of fulvenes with N-alkylidene glycine esters: a facile synthesis of the delavayine and incarvillateine framework

[reaction: see text] In contrast to the [3+2] or [4+3] cycloaddition of N-metalated azomethine ylides and various alkenes, N-benzylidene glycine ethyl ester reacts with fulvenes to give the hetero [6+3] cycloaddition adducts with high stereoselectivity, constituting an efficient and novel route to [2]pyrindines.     

3 + 2] cycloaddition reactions of 4-alkyl-3-hydroxy-2H-pyrazolo[4,3-c]isoquinolinium inner salts

Heating dipolarophiles with 4-alkyl-3-hydroxy-2H-pyrazolo[4,3-c]isoquinolinium hydroxide inner salts results in [3 + 2] cycloaddition across positions 3a and 5 of the aromatic system to give the [3 + 2] cycloadducts in good yield. When the 4-alkyl substituent is a 2-acetate ester and the methylene group can be deprotonated, a second mode of [3 + 2] cycloaddition becomes available for the resulting anion (across the side chain methine group and position 5 of the aromatic system) and occurs under basic conditions, allowing either of two modes of [3 + 2] cycloaddition to be selected by appropriate choice of reaction conditions.     

Investigation of the copper binding site on the human islet amyloid polypeptide hormone

The metal ion binding sites of human islet amyloid polypeptide (hIAPP) have been investigated to explain the biological activity difference in the fibril formation process. The structures of [hIAPP...Cu (or Al)](n+) and [hIAPP17-30...Cu]2+ complex were investigated by electrospray ionization-mass spectrometry (ESI-MS). The fragmentation patterns of [hIAPP...Cu [or Al)](n+) and [hIAPP17-30...Cu]2+ complex were analyzed by tandem mass spectrometry (MS/MS) and multi-stage mass spectrometry (MS3) spectra. The [hIAPP+Cu+H]3+, [hIAPP+Al+H]4+ and [hIAPP17-30+Cu]2+ complexes were observed in MS spectra. The Cu binding site of hIAPP is suggested to be the N22-F-G-A-I26 part for the [hIAPP+Cu+H]3+ gas-phase complex. The original hIAPP conformation was supposed to be changed by the interaction between the Cu ion and the N22-F-G-A-I26 part in the [hIAPP+Cu+H]3+ gas-phase complex.     

Vectorial property dependence in bis {4'-(n-pyridyl)-2,2':6',2"-terpyridine}iron(II) and ruthenium(II) complexes with n = 2, 3 and 4

A comparative structural and spectroscopic investigation of the complexes [M(1)2]2+, [M(2)2]2+ and [M(3)2]2+ in which M = Fe or Ru, and ligands 1, 2 and 3 are 4'-(2-pyridyl)-, 4'-(3-pyridyl)- and 4'-(4-pyridyl)-2,2':6',2"-terpyridine, respectively, is reported. The complexes [Ru(1)2]2+, [Ru(2)2]2+ and [Ru(3)2]2+ undergo mono- and bis-N-methylation. The consequences of methylation on the absorption spectra and electrochemical properties are discussed; the solid-state structure of the bis(N-methylated) derivative of [Ru(2)2][PF6]2 is presented.     

Reaction mechanism and chemoselectivity of intermolecular cycloaddition reactions between phenyl-substituted cyclopropenone ketal and methyl vinyl ketone

In this paper, the mechanisms of the intermolecular [3+2] and [1+2] cycloaddition reactions of 1,1/1,3-dipolar π-delocalized singlet vinylcarbenes, which is obtained from cyclopropenone, with an electron-deficient C═O or C═C dipolarophile, to generate five-membered ring products are first disclosed by the density functional theory (DFT). Four reaction pathways, including two concerted [3+2] cycloaddition reaction pathways and two stepwise reaction pathways (an initial [1+2] cycloaddition and then a rearrangement from the [1+2] cycloadducts to the final [3+2] cycloadducts), are investigated at the B3LYP/6-31G(d,p) level of theory. The calculated results reveal that, in contrast to the concerted C═O [3+2] cycloaddition reaction pathway, which is 7.1 kcal/mol more energetically preferred compared with its stepwise reaction pathway, the C═C dipolarophile favors undergoing [1+2] cycloaddition rather than concerted [3+2] cycloaddition (difference of 5.3 kcal/mol). The lowest free energy barrier of the C═O concerted [3+2] cycloaddition reaction pathway shows that it predominates all other reaction pathways. This observation is consistent with the finding that the C═O [3 + 2] cycloadduct is the main product under experimental conditions. In addition, natural bond orbital second-order perturbation charge analyses are carried out to explain the preferred chemoselectivity of C═O to the C═C dipolarophile and the origins of cis-stereoselectivity for C═C [1+2] cycloaddition. Solvent effects are further considered at the B3LYP/6-31G(d,p) level in the solvents CH(3)CN, DMF, THF, CH(2)Cl(2), toluene, and benzene using the PCM model. The results indicate that the relative reaction trends and the main products are insensitive to the polarity of the reaction solvent.     

Influence of Molecular Structure on the Dimerization Reactivity of Germaaromatic Compounds： a Theoretical Study

Density functional theory (DFT) calculations, at the B3LYP/6-311G** level of theory, were performed to study the reaction mechanism and potential energy surface of the [2 + 2], [4 + 2] and [4 + 4] dimerization reactions of some germaaromatic compounds. The influence of reactant's molecular structure and benzene solvent on the potential energy surface of the studied reactions was investigated. Our calculation results show that [2 + 2] and [4 + 4] reactions are concerted and synchronous processes; while [4 + 2] reactions proceed via a concerted but asynchronous way in general. [2 + 2] and [4 + 2] reactions of germabenzenes and 1-germana- phthalene proceed much more easily than the corresponding [4 + 4] reaction, both thermo- dynamically and kinetically; while most [4 + 2] paths have lower activation barrier than the corres- ponding [2 + 2] ones. As the number of six-membered aromatic rings in reactant molecules becomes larger, [2 + 2], [4 + 2] and [4 + 4] reactions become easier to proceed. The influence of substituents at the Ge atom of germabenzenes on the potential energy surface of [2 + 2] and [4 + 2] reactions correlates with their electronic properties and volume. Solvent effect is not crucial for the potential energy surfaces of the studied reactions.     

Reactivity of tri- and tetra-nuclear ethylidyne cyclopentadienylcobalt clusters towards protonic acids

The bis(μ₃-ethylidyne) tricobalt cluster [(CpCo)₃(μ₃-CCH₃)₂] (1b) is protonated by trifluoroacetic acid to give the dicobalt edge-protonated cation [H(CpCo)₃(μ₃-CCH₃)₂]⁺ [lb + H]⁺. Protonation of the μ₃-ethylidyne tetracobalt cluster hydride [H(CpCo)₄(μ₃-CCH₃)] (3) takes place in two consecutive steps. At low temperature [H₂(CpCo)₄(μ₃-CCH₃)]⁺ [3 + H]⁺ is formed first, and is then slowly converted into [H₃(CpCo)₄(μ₃-CCH₃)]²⁺ [3 + 2H]²⁺ by an excess of acid. As judged by the ¹H NMR data and the crystal structure of [3 + X]⁺[(CF₃COO)₂X]⁻ (X = H or D) the endo hydrogens in [3 + H]⁺ and [3 + 2H]²⁺ occupy μ₃-(Co₃) face capping hydridic positions. The cations [1b + H]⁺ and [3 + H]⁺ show hydride fluxionality in solution, which in the case of [3 + H]⁺ can be frozen out on the NMR timescale at low temperature (ΔG ^≠ (203 K) = 40.8 kJ/mol). The structure of [3 + X]⁺ [(CF₃COO)₂X]⁻ (X = H or D) was determined by X-ray crystallography. One of the hydrides/deuterides is located on the crystallographic mirror plane, capping a tricobalt face of the cluster cation. The other endo hydrogen atom is believed to be disordered between the other two μ₃-(Co₃) sites, which are related by space group symmetry. Deuteronation of 3 shows a strong normal kinetic deuterium isotope effect. From the temperature independence of the ¹H NMR spectrum of [3 + 2D]²⁺ a non-fluxional solution structure can be inferred. In all the systems studied, hydridic (μ₂- or μ₃-) sites are thermodynamically preferred to possible isomeric agostic CoHC or Co₂HC sites for the endo hydrogens. Agostic interactions cannot, however, be ruled out in transient intermediates during the course of the protonations.     

新型双核配合物的形成及荧光性质研究

利用光谱学方法研究了[Ru(bpy)2TPPHZ]2+(TPPHZ=四吡啶[3,2-a: 2',3'-c: 3",2"-h: 2'",3'"-j]吩嗪)和[Ru(bpy)2ODHIP]2+(ODHIP=3,4-二羟基-咪唑并[4,5-f][1,10]邻菲咯啉)与Ni2+的配位情况及配位后的荧光性质变化, 探讨了配合物与Ni2+配位形成双核配合物后与DNA的作用机制变化. 结果表明, [Ru(bpy)2TPPHZ]2+和[Ru(bpy)2ODHIP]2+均可与Ni2+配位, 形成双核配合物[Ru(bpy)2(TPPHZ)Ni]4+和[Ru(bpy)2(ODHIP)Ni]4+, 配合物的荧光强度随着Ni2+浓度的增加而减弱. 与DNA作用后, 配合物仍可与Ni2+配位形成双核配合物, [Ru(bpy)2(TPPHZ)Ni]4+的荧光几乎完全消失, 同时配合物与DNA保持插入模式作用, 而配合物[Ru(bpy)2(ODHIP)Ni]4+与DNA的作用则由沟面结合改为插入结合, 同时配合物的荧光减弱.     

3D H-bonding networks self-assembly from pyridinium derivatives and bis(maleonitriledithiolato)zincate(II)

The two ion-pair complexes, [pyH]₂[Zn(mnt)₂] (1) and [4,4′-bipyH₂]-[Zn(mnt)₂] (2), were synthesized, where mnt²⁻ denotes maleonitriledithiolate, and [pyH]⁺, [4,4′-bipyH₂]²⁺ represent pyridinium and diprotonated 4,4′-bipyridinium, respectively. Their single crystal structures show that there are strong bifurcated H-bonding interactions between the cations of the pyridinium derivative and the [Zn(mnt)₂]²⁻ anions in both 1 and 2. The bifurcated H-bonding interactions between the N–H of the pyridiniums and the CN groups of the mnt²⁻ ligands give rise to a 2D layered H-bonding network, the adjacent layers come together in such way as mutual embrace to give a tight pack, thus 2D hydrogen-bonding sheets further develop into 3D H-bonding networks through weak C–HS and ππ stacking interactions in 1. As for 2, the cations and anions connect into several types of H-bonding macrorings ([2+2], [3+3] and [4+4]), these H-bonding macrorings fuse to extend into 2D layered structure, the interpenetration between [3+3] and [4+4] type H-bonding macrorings in the adjacent layers give further rise to novel 3D extended H-bonding networks, in which there are clearly parallel stacks of cations and the chelate rings of anions.     

Mobile phase variations in thermospray liquid chromatography-mass spectrometry of pesticides

The effect of four different mobile phase compositions with reversed-phase methanol-water (50:50) + 0.05 M ammonium acetate, methanol-water (50:50) + 0.05 M ammonium formate, acetonitrile-water (50:50) + 0.05 M ammonium acetate and acetonitrile-water (50:50) + 0.05 M ammonium formate were compared in filament-on thermospray liquid chromatography-mass spectrometry for the determination of carbamate and chlorotriazine pesticides. In the positive-ion mode, [M + H]+ and [M + NH4]+ were generally the base peaks for the chlorotriazines and the carbamates, respectively. Depending on the mobile phase used, other adduct ions obtained corresponded to [M + CH3CN + H]+, [M + CH3OH + NH4]+, [M + CH3COONH4 + NH4 - 2H2O]+, [M + CH3CN + NH4]+, [M + CH3COONH4 + H - H2O]+ and the dimer [2M + H]+. In the negative-ion mode, [M - H]- and adducts with the ionizing additive [M + CH3COO]- or [M + HCOO]- were obtained. Other ions for the carbamates carbaryl and oxamyl corresponded to [M - CONHCH3 + CH3COOH]- and [M - CON(CH3)2 + HCOO]-, respectively. The variation of mobile phase composition provides additional structural information in thermospray liquid chromatography-mass spectrometry with no appreciable loss of sensitivity. Applications are reported for the determination of carbamate and chlorotriazine pesticides at the ng/g level in spiked and real soil samples, respectively.