Pyridine Anion Research Articles

Total synthesis of (-)-securingine G.

In this study, we present the first total synthesis of (-)-securingine G. Diverging from the proposed biosynthetic pathway, our approach involves the addition of nucleophilic pyridine anion species to the electrophilic menisdaurilide congener. Crucially, incorporating a weakly basic yet nucleophilic tri(2-pyridinyl)lanthanum complex proved essential to circumvent undesired base-mediated pathways during the key coupling reaction. Notably, we introduce n-Bu3La·5LiCl as a new exchange reagent, facilitating efficient halide/lanthanum exchange of (hetero)aryl halides.

Anion-Activated Bases and Nucleophiles Characterized by Photoelectron Spectroscopy.

Negative ion photoelectron spectra at 20 K along with ab initio [CCSD(T)] and M06-2X density functional theory calculations are reported for a series of six basic and nucleophilic pyridine derivatives with an anionic substituent [i.e., 3- and 4-PyrBX3-, where X = F, 4-t-BuC6H4, 4-MeOC6H4, and 3,5-(MeO)2C6H3]. Vertical detachment energies (VDEs) of these charge-activated reagents span from 4.50-5.85 eV and are well reproduced by M06-2X/aug-cc-pVTZ and CCSD(T)/maug-cc-pVTZ computations. Surprisingly, the VDEs are found to correlate with the SN2 reactivity of the PPh4+ salts of the substituted pyridine anions with 1-iodooctane in dichloromethane. This provides an experimental measure of the nucleophilicity of these charge-activated anions, which represent a new class of chemical reagent.

Theoretical modeling of the singlet-triplet spin transition in different Ni(II)-diketo-pyrphyrin-based metal-ligand octahedral complexes.

The structural stability, charge transfer effects and strength of the spin-orbit couplings in different Ni(ii)-ligand complexes have been studied at the DFT (B3LYP and CAM-B3LYP) and coupled cluster (DLPNO-CCSD(T)) levels of theory. Accordingly, two different, porphyrin- and diketo-pyrphyrin-based four-coordination macrocycles as planar ligands as well as pyridine (or pyrrole) and mesylate anion molecular groups as vertical ligands were considered in order to build metal-organic complexes with octahedral coordination configurations. For each molecular system, the identification of equilibrium geometries and the intersystem crossing (the minimum energy crossing) points between the potential energy surfaces of the singlet and triplet spin states is followed by computing the spin-orbit couplings between the two spin states. Structures, based on the diketo-pyrphyrin macrocycle as the planar ligand, show stronger six-coordination metal-organic complexes due to the extra electrostatic interaction between the positively charged central metal cation and the negatively charged vertical ligands. The results also show that the magnitude of the spin-orbit coupling is influenced by the atomic positions of deprotonations of the ligands, and implicitly the direction of the charge transfer between the ligand and the central metal ion.

Co‐Reactant and Annihilation Electrogenerated Chemiluminescence of [Ir(df‐ppy)2(ptb)]+ Derivatives

AbstractThe [Ir(df‐ppy)2(ptb)]+ complex (where df‐ppy=2‐(2,4‐difluorophenyl)pyridine anion; ptb=1‐benzyl‐1,2,3‐triazol‐4‐ylpyridine) has previously been shown to be a promising blue luminophore for electrogenerated chemiluminescence (ECL). Herein, we examine the ECL of three [Ir(df‐ppy)2(ptb)]+ derivatives (containing df(CF3)‐ppy‐Me, df(CN)‐ppy, or df‐ppy‐CF3 ligands) in comparison with the parent complex. In the annihilation mode, all four complexes exhibited ECL, although the emission from [Ir(df(CN)‐ppy)2(ptb)]+ was weak and red‐shifted from its photoluminescence. The absence of this shift in the corresponding reductive‐oxidation co‐reactant ECL with benzoyl peroxide (BPO), and the very low ECL intensity in oxidative–reductive co‐reactant ECL with tri‐n‐propylamine (TPrA) enables this effect to be ascribed to oxidative degradation. The [Ir(df‐ppy‐CF3)2(ptb)]+ complex gave the greatest ECL intensities of the four [Ir 2(ptb)]+ complexes in the annihilation mode and through both co‐reactant pathways, and shows great potential as a blue electrochemiluminophore. In “mixed annihilation” ECL experiments involving the oxidation of Ir(ppy)3 and the reduction of the [Ir 2(ptb)]+ complexes, only [Ir(df‐ppy)2(ptb)]+ and [Ir(df(CF3)‐ppy‐Me)2(ptb)]+ elicited the green ECL from Ir(ppy)3*, as the electron‐withdrawing substituents on the other two complexes lower the SOMO energy of the reduced complexes below that required to attain the Ir(ppy)3* excited state upon reaction with [Ir(ppy)3]+.

Ultrafast dynamics of the dipole moment reversal in a polar organic monolayer.

Pyridine layers on Cu(110) possess a strong electric field due to the large dipole of adsorbed pyridine. This electric field is visible as an enhanced sum frequency response from both the copper surface electrons and the aromatic C-H stretch of pyridine via a third order susceptibility. In response to a visible pump pulse, both surface electron and C-H stretch sum frequency signals are reduced on a subpicosecond time scale. In addition, the relative phase between the two signals changes over a few hundred femtoseconds, which indicates a change in the electronic structure of the adsorbate. We explain the transients as a consequence of the previously observed pyridine dipole field reversal when the pump pulse excites electrons into the pyridine π* orbital. The pyridine anions in the pyridine layer cause a large-scale structural change which alters the pyridine-copper bond, reflected in the altered sum frequency response.

Heterolytic bond activation at gold: evidence for gold(iii) H-B, H-Si complexes, H-H and H-C cleavage.

The coordinatively unsaturated gold(iii) chelate complex [(C^N-CH)Au(C6F5)]+ (1 +) reacts with main group hydrides H-BPin and H-SiEt3 in dichloromethane solution at -70 °C to form the corresponding σ-complexes, which were spectroscopically characterized (C^N-CH = 2-(C6H3Bu t )-6-(C6H4Bu t )pyridine anion; Pin = OCMe2CMe2O). In the presence of an external base such as diethyl ether, heterolytic cleavage of the silane H-Si bond leads to the gold hydrides [{(C^N-CH)AuC6F5}2(μ-H)]+ (2 +) and (C^N-CH)AuH(C6F5) (5), together with spectroscopically detected [Et3Si-OEt2]+. The activation of dihydrogen also involves heterolytic H-H bond cleavage but requires a higher temperature (-20 °C). H2 activation proceeds in two mechanistically distinct steps: the first leading to 2 plus [H(OEt2)2]+, the second to protonation of one of the C^N pyridine ligands and reductive elimination of C6F5H. By comparison, formation of gold hydrides by cleavage of suitably activated C-H bonds is very much more facile; e.g. the reaction of 1·OEt2 with Hantzsch ester is essentially instantaneous and quantitative at -30 °C. This is the first experimental observation of species involved in the initial steps of gold catalyzed hydroboration, hydrosilylation and hydrogenation and the first demonstration of the ability of organic C-H bonds to act as hydride donors towards gold.

Synthesis, crystal structure and magnetic property of a new Co(II) complex based on 4-phenyl pyridine and 5-sulfoisophthalic acid anion

ABSTRACTA new cobalt complex [Co3(SIP)2(4-PP)8(H2O)6]·4H2O·2(4-PP) (1) with 5-sulfoisophthalic acid sodium (NaH2SIP) and 4-phenyl pyridine (4-PP) as ligands has been synthesized in the mixed solvents of ethanol and water. It crystallized in monoclinic, space group P21/c, with a = 20.9642(9) Å, b = 15.6091(5) Å, c = 20.0126(8) Å, α = 90.00°, β = 115.493(6)°, γ = 90.00°, V = 5911.2(4) Å3, Z = 2, Dc = 1.346 g/cm−3, F(000) = 2494, the final GOOF = 1.038, Rint = 0.0258 and wR2 = 0.1793. The complex (1) was characterized by single-crystal X-ray diffraction, magnetic susceptibility and IR spectroscopy analyses. Single-crystal X-ray diffraction shows that complex (1) is trinuclear based on cobalt units. Magnetic susceptibility measurement indicates that complex (1) shows an antiferromagnetic coupling between the Co(II) ions.

Octahedral manganese(i) and ruthenium(ii) complexes containing 2-(methylamido)pyridine-borane as a tripod κ3N,H,H-ligand.

The borane adduct of the 2-(methylamido)pyridine anion, [mapyBH3]-, has been incorporated into octahedral metal complexes. In fac-[Mn(κ3N,H,H-mapyBH3)(CO)3] (1) and fac-[RuH(κ3N,H,H-mapyBH3)(CO)(PiPr3)] (2), which have been prepared by treating K[mapyBH3] with fac-[MnBr(MeCN)2(CO)3] and [RuHCl(CO)(PiPr3)2], respectively, it behaves as a tripod ligand, attached to the metal atom through the amido N atom and through two H atoms of the BH3 moiety. X-ray diffraction analyses and theoretical studies (DFT, QTAIM) have shown that the MH2B atom grouping of 1 and 2 comprises two 3c-2e M-H-B interactions that are between those of the Shimoi type (κ1H coordination of the B-H bond) and those of the agostic type (κ2B,H coordination of the B-H bond). However, while both M-H-B interactions are almost identical in complex 1, this is not the case in complex 2, in which one M-H-B interaction is more agostic than the other due to the different trans influence of the hydride and phosphane ligands.

2-巯基吡啶配合物的合成及量子化学计算

基于配体2,2’-二硫二吡啶(简称Dpds)，采用分层扩散法，合成出六核簇状配位化合物Cu6(C5H4NS)6。采用密度泛函理论(DFT)下的B3LYP计算方法、NBO计算方法对该配合物进行量子化学计算，同时进行了前线轨道的研究。结果表明：每个配合物含六个铜离子、六个2-巯基吡啶阴离子，优化后的理论值与实验值比较吻合，误差在允许的范围内，理论计算的完成证明了实验数据的可靠性。 A six-core cluster compound Cu6(C5H4NS)6, was prepared by layered a N, N-Dimethylformamide solution of Cu(CH3COO)2•H2O on a dichloromethane solution of Dpds. The quantum chemistry cal-culation of the complex was carried out by using the B3LYP calculation method of density functional theory (DFT) and the NBO calculation method; at the same time, the research of frontier orbital is carried out. The results showed that the six-core copper (II) cluster complex contains six crystallographically unique Cu (II) ions and six 2-mercapto pyridine anions. It is found that the theoretical values are in agreement with the experimental ones, and the error is within the al-lowable range. And the completion of theoretical calculations proved the reliability of the experi-mental data.

Excellent electrocatalytic activity of benzil for direct reduction of CO2 as well as indirect reduction of pyridine: A kinetic view of the electrocarboxylation process

Benzil, 1,2-diphenylethane-1,2-dione, was used as an excellent electrocatalyst for reduction of carbon dioxide, CO2. The reduction overpotential of CO2 was reduced about 900mV in the presence of a benzil mediator. The chemical reaction of the product of the electrocatalytic reduction of CO2, (activated CO2, CO2•−) with pyridine at a glassy carbon electrode, GCE, surface and in an acetonitrile-But4NClO4 solution was investigated by cyclic voltammetry, chronoamperometry and controlled potential coulometry. By chronoamperometry, the catalytic rate constant, k, for the electron transfer between benzil and CO2 was obtained as 8.1±0.4M−1s−1. The results indicate that pyridine has a strong interaction with the activated CO2. The coulometry method was used to obtain the product of the pyridine chemical reaction with CO2•−. The spectral characterizations of FTIR, 1H and 13C NMR of the coulometry experiment product proved that the pyridine anion radical, Py•−, was carboxylated by CO2•−, and isonicotinic acid is the final major product.

Highly Phosphorescent Cyclometalated Iridium(III) Complexes for Optoelectronic Applications: Fine Tuning of the Emission Wavelength through Ancillary Ligands

A series of novel, highly phosphorescent cyclometalated iridium(III) complexes of type [(X2C^N)2Ir(Q2bpy)]+PF6– (where X2C^N is 2-phenylpyridine or 2-(2,4-difluorophenyl)pyridine anion and Q2bpy are 4,4′-bifunctionalized 2,2′-bipyridines) is presented. The complexes were fully characterized by means of NMR spectroscopy, high-resolution mass spectrometry (HRMS), cyclic voltammetry, and UV–vis. For several compounds also the crystallographic structures were obtained. The cyclometalates exhibited efficient photoluminescence at 298 K both in solution and in the solid state with good intensity and color purity. The emission wavelength range covered almost the whole visible spectrum and was strongly correlated with the EWG/ERG character of the Q substituent in the ancillary ligand. For further insight into the electronic structure of the complexes, a comprehensive electrochemical support (CV) was introduced, and finally, it was confronted with theoretical background using a density functional theory approach to...

Blue Electrogenerated Chemiluminescence from Water-Soluble Iridium Complexes Containing Sulfonated Phenylpyridine or Tetraethylene Glycol Derivatized Triazolylpyridine Ligands.

Incorporating phenylpyridine- and triazolylpyridine-based ligands decorated with methylsulfonate or tetraethylene glycol (TEG) groups, a series of iridium(III) complexes has been created for green and blue electrogenerated chemiluminescence under analytically useful aqueous conditions, with tri-n-propylamine as a coreactant. The relative electrochemiluminescence (ECL) intensities of the complexes were dependent on the sensitivity of the photodetector over the wavelength range and the pulse time of the applied electrochemical potential. In terms of the integrated area of corrected ECL spectra, with a pulse time of 0.5 s, the intensities of the Ir(III) complexes were between 18 and 102 % that of [Ru(bpy)3 ](2+) (bpy=2,2'-bipyridine). However, when the intensities were measured with a typical bialkali photomultiplier tube, the signal of the most effective blue emitter, [Ir(df-ppy)2 (pt-TEG)](+) (df-ppy=2-(2,4-difluorophenyl)pyridine anion, pt-TEG=1-(2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethyl)-4-(2-pyridyl)-1,2,3-triazole), was over 1200 % that of the orange-red emitter [Ru(bpy)3 ](2+) . A combined experimental and theoretical investigation of the electrochemical and spectroscopic properties of the Ir(III) complexes indicated that the greater intensity from [Ir(df-ppy)2 (pt-TEG)](+) relative to those of the other Ir(III) complexes resulted from a combination of many factors, rather than being significantly favored in one area.

A novel cross-linked anion exchange membrane with conjugated and non-conjugated pyridine groups

A novel cross-linked pyridine anion exchange membrane was synthesized via thermal cross-linking methods. 2,5-bis(2,3,4,5,6-pentafluorophenyl)-1,3,4-oxadiazole (FPOx) and diallyl bisphenol A (DABPA) were reacted to obtain the main polymer chain (MP). MP was substituted with 4-bromopyridine and 4-hydroxypyridine to generate two pyridine polymers conjugated pyridine polymer (CPP) and non-conjugated pyridine polymer (NPP). The different conjugation statues of CPP and NPP led to distinct mechanical and electrochemical properties. The diallyl groups in MP acted as the cross-linking structures which strengthened the mechanical properties of CPP and NPP and provided more flexible side chains. The ultimate membrane CPP-membrane and NPP-membrane were prepared by solution casting methods. Compared with NPP-membrane, the ionic conductivity of CPP can achieve to 20.1 mS/cm at 20 °C with excellent mechanical and thermal characteristics. Quantum theory computation and AFM morphology were carried out to figure out the reason of the difference in ionic conductivities and physical properties.

Complexes of Rh(III), Ir(III), and Pt(IV) with metallated 2-(n-tolyl)pyridine, ethylendiamine, acetate, and diethyldithiocarbamate ligands

cis-C,C Isomers of the [M(ptpy)2(L∧L)](PF6)Z complexes [M = Rh(III), Ir(III), Pt(IV); ptpy− = deprotonated form of 2-(n-tolyl)pyridine, (L∧L) = acetate, trifluoroacetate, or diethyldithiocarbamate anions, or ethylenediamine; z = 0, 1, 2] were prepared and characterized by 1H and 19F NMR, IR, electronic absorption and emissions spectroscopy, and by voltammetry methods. The highest occupied and the lowest unoccupied molecular orbitals were assigned to dπ and π*ptpy orbitals of the metal and the metallated ligand. Luminescence of the complexes in the visible spectral region was assigned to the spin-forbidden optical transition from the lowest energy state of the mixed nature (πptpy-π*ptpy/dx-π*ptpy).

Preorganization in bistriazolyl anion receptors

A series of 4,6-bis-(1,2,3-triazolyl)-pyrimidine and 4,6-bis-(1,2,3-triazolyl)-pyridine anion receptors were synthesized and the effect of the pyrimidine and pyridine moieties on their binding properties was examined. We found that intramolecular interactions preorganize the 4,6-bis-(1,2,3-triazolyl)-pyridine receptors resulting in higher anion binding constants in comparison with the nonpreorganized 4,6-bis-(1,2,3-triazolyl)-pyrimidine receptor.

Reversible C–C Bond Formation between Redox-Active Pyridine Ligands in Iron Complexes

This manuscript describes the formally iron(I) complexes L(Me)Fe(Py-R)(2) (L(Me) = bulky β-diketiminate; R = H, 4-tBu), in which the basal pyridine ligands preferentially accept significant unpaired spin density. Structural, spectroscopic, and computational studies on the complex with 4-tert-butylpyridine ((tBu)py) indicate that the S = 3/2 species is a resonance hybrid between descriptions as (a) high-spin iron(II) with antiferromagnetic coupling to a pyridine anion radical and (b) high-spin iron(I). When the pyridine lacks the protection of the tert-butyl group, it rapidly and reversibly undergoes radical coupling reactions that form new C-C bonds. In one reaction, the coordinated pyridine couples to triphenylmethyl radical, and in another, it dimerizes to give a pyridine-derived dianion that bridges two iron(II) ions. The rapid, reversible C-C bond formation in the dimer stores electrons from the formally reduced metal as a C-C bond in the ligands, as demonstrated by using the coupled diiron(II) complex to generate products that are known to come from iron(I) precursors.

Structure and Bonding in the Trichalcogenometaphosphate–Pyridine Anions [PX3 − Py]− (X = O, S, Se, Te)

The structures, bonding, NMR chemical shifts, and Lewis acid/base behavior of the trichalcogenometaphosphate–pyridine anions [PX3 − Py]− (X = O, S, Se, Te) have been evaluated theoretically on the basis of B3LYP/ECP(Se,Te) + cc-pVTZ//PM3 calculations using quasirelativistic pseudopotentials for Se and Te. The molecular and electronic structures of the trichalcogenometaphosphate–pyridine adducts [PX3 − Py]− (X = O, S, Se, Te) were calculated, and the bonding was analyzed and discussed on the basis of natural bond orbital (NBO) analyses and qualitative valence bond (VB) considerations. The (σ(px)-LP(N)) → (σ(px)-LP*(P)) donor–acceptor interaction increases, and, consequently, the P‒N bond length decreases from PO3 − Py− (weak interaction, long P‒N bond) to PTe3 − Py− (strong interaction, short P‒N bond). This theoretical finding is in good accord with the measured P‒N bond lengths in [PSe3 − Py]− and [PTe3 − Py]−. In the gas phase, all four [PX3 − Py]− (X = O, S, Se, Te) adducts are unstable with respect to dissociation into free PX3 − and pyridine.

Electrochemical and Spectroscopic Characterization of a Series of Mixed-Ligand Diruthenium Compounds

The electrochemistry and spectroelectrochemistry of a novel series of mixed-ligand diruthenium compounds were examined. The investigated compounds having the formula Ru(2)(CH(3)CO(2))(x)(Fap)(4-x)Cl where x = 1-3 and Fap is 2-(2-fluoroanilino)pyridinate anion were made from the reaction of Ru(2)(CH(3)CO(2))(4)Cl with 2-(2-fluoroanilino)pyridine (HFap) in refluxing methanol. The previously characterized Ru(2)(Fap)(4)Cl as well as the three newly isolated compounds represented as Ru(2)(CH(3)CO(2))(Fap)(3)Cl (1), Ru(2)(CH(3)CO(2))(2)(Fap)(2)Cl (2), and Ru(2)(CH(3)CO(2))(3)(Fap)Cl (3) possess three unpaired electrons with a Ru(2)(5+) dimetal core. Complexes 1 and 2 have well-defined Ru(2)(5+/4+) and Ru(2)(5+/6+) redox couples in CH(2)Cl(2), but 3 exhibits a more complicated electrochemical behavior due to equilibria involving association or dissociation of the anionic chloride axial ligand on the initial and oxidized or reduced forms of the compound. The E(1/2) values for the Ru(2)(5+/4+) and Ru(2)(5+/6+) processes vary linearly with the number of CH(3)CO(2)(-) bridging ligands on Ru(2)(CH(3)CO(2))(x)(Fap)(4-x)Cl and plots of reversible half-wave potentials vs the number of acetate groups follow linear free energy relationships with the largest substituent effect being observed for the oxidation. The major UV-visible band of the examined compounds in their neutral Ru(2)(5+) form is located between 550 and 800 nm in CH(2)Cl(2) and also varies linearly with the number of CH(3)CO(2)(-) ligands on Ru(2)(CH(3)CO(2))(x)(Fap)(4-x)Cl. The electronic spectra of the singly oxidized and singly reduced forms of each diruthenium species were characterized by UV-visible spectroelectrochemistry in CH(2)Cl(2).

Interconversion between (3,1) and (4,0) Isomers of Ru2(L)4X Complexes where L is 2-Anilinopyridinate or 2-(2,4,6-Trifluoroanilino)pyridinate Anion and X = Cl− or C≡CC5H4N−

A reaction between the (4,0) isomer of Ru 2(ap) 4Cl and LiC[triple bond]CC5H4N leads to a (3,1) isomer of Ru 2(ap) 4(C[triple bond]CC5H4N) 2 1 (ap = anilinopyridinate anion), whereas a reaction involving the (3,1) isomer of Ru 2(F 3ap) 4Cl and TBACl.H 2O leads to (4,0) Ru 2(F 3ap) 4Cl 2 (F 3ap = 2-(2,4,6-trifluoroanilino)pyridinate anion). To our knowledge, these are the first documented examples for isomeric conversion involving diruthenium compounds with tetracarboxylate-type structures. The structural, electrochemical, and spectroscopic properties of 1 and 2 were examined. The reversible Ru 2 (5+/6+) process of (3,1) [Ru 2(F 3ap) 4Cl] (+) is located at 0.62 V in CH 2Cl 2, 0.1 M TBAP but shifts to 0.29 V upon formation of (3,1) Ru 2(F 3ap) 4Cl 2 in CH 2Cl 2 containing chloride from added TBACl.H 2O and shifts even further to E 1/2 = 0.10 V after generation of (4,0) Ru 2(F 3ap) 4Cl 2 in solution. The 190 mV potential difference between the Ru 2 (6+/5+) redox couples of (3,1) Ru 2(F 3ap) 4Cl 2 and (4,0) Ru 2(F 3ap) 4Cl 2 in chloride-containing media can be compared to a smaller potential difference of only 60 mV between the Ru 2 (6+/5+) redox couples of (3,1) Ru 2(F 3ap) 4Cl and (4,0) Ru 2(F 3ap) 4Cl in CH 2Cl 2 containing 0.1 M tetrabutylammonium perchlorate (TBAP) as supporting electrolyte. The larger Delta E 1/2 in the case of the bis-chloride complexes in solutions containing 0.1 M TBACl.H 2O can be accounted for in large part by structural differences that manifest themselves in different strengths of axial coordination to the Ru 2 (5+) form of the compounds.

Unconventional ion exchange resins and their retention properties for Hg 2+ ions

Synthesis of two unconventional ion exchange resins and their behaviour on the mercury sorption experiments were investigated. The ion exchange resins were obtained by the quaternization reaction of 4-vinylpyridine:divinylbenzene copolymer, gel-type, by two ways namely, the nucleophilic substitution of the pyridine matrix with 2-chloroacetamide and the nucleophilic addition of protonated copolymer to acrylamide. Comparative sorptions of Hg 2+ ions on the synthesized pyridine resins by batch experiments in mono- and binary system were analyzed. Mercury retention experiments aimed to study the influence of the solution concentration, contact time and solution pH. The removal of Hg 2+ ions from aqueous solutions depends on the pH values, the amount of the retained mercury increased with the pH value. The studied strong base pyridine anion exchange resins presented a good selectivity for the Hg 2+ ions during the competitive sorption of Hg 2+/Cu 2+, Hg 2+/Zn 2+ and Hg 2+/Fe 3+ at metal cations ratio of 1:1.