Triazole Complexes Research Articles

Spin Crossover in Dinuclear N4S2 Iron(II) Thioether-Triazole Complexes: Access to [HS-HS], [HS-LS], and [LS-LS] States.

Access to a new family of thioether-linked PSRT ligands, 4-substituted-3,5-bis{[(2-pyridylmethyl)sulfanyl]methyl}-4H-1,2,4-triazoles (analogues of the previously studied amino-linked PMRT ligands), has been established. Four such ligands have been prepared, PSPhT, PS(i)BuT, PS(t-Bu)PhT, and PS(Me)PhT, with R = Ph, (i)Bu, (t-Bu)Ph, and (Me)Ph, respectively. Three dinuclear colorless to pale green iron(II) complexes, [Fe(II)2(PSRT)2](BF4)4·solvent, featuring N4S2 donor sets, were prepared. Single-crystal structure determinations on [Fe(II)2(PSPhT)2](BF4)4·2MeCN·H2O, [Fe(II)2(PSPhT)2](BF4)4·2(1)/2MeCN·(1)/2H2O·THF, [Fe(II)2(PS(Me)PhT)2](BF4)4·2MeCN, and [Fe(II)2(PS(i)BuT)2](BF4)4·4MeCN reveal that all four are stabilized in the [HS-HS] state to 100 K and that both possible binding modes of the bis-terdentate ligands, cis- and trans-axial, are observed. Variable-temperature magnetic susceptibility studies of air-dried crystals (solvatomorphs of the single crystal samples) reveal the first examples of spin crossover (SCO) for a dinuclear iron(II) complex with N4S2 coordination. Specifically, [Fe(II)2(PSPhT)2](BF4)4·2(1)/2H2O undergoes a multistep but complete SCO from [HS-HS] to [LS-LS], whereas [Fe(II)2(PS(Me)PhT)2](BF4)4·1(1)/2MeCN·2H2O exhibits a half-SCO from [HS-HS] to [HS-LS]. In contrast, [Fe(II)2(PS(i)BuT)2](BF4)4·MeCN·H2O remains [HS-HS] down to 50 K. The reflectance spectrum of pale green [Fe(II)2(PSPhT)2](BF4)4·(1)/2CHCl3·2(1)/2H2O (solvatomorph A) reveals a trace of LS character (572 nm band (1)A1g → (1)T1g). Evans' (1)H NMR method and UV-vis spectroscopy studies revealed that on cooling dark green acetonitrile solutions of these complexes from 313 to 233 K, all three undergo SCO centered at or near room temperature. The tendency of the complexes to go LS in solution reflects the electronic impact of R on the σ-donor strength of the PSRT ligand, whereas the opposite trend in stabilization of the LS state is seen in the solid state, where crystal packing effects, of the R group and solvent content, dominate the SCO behavior.

Polynuclear Silver(I) Triazole Complexes: Ion Conduction and Nanowire Formation in the Mesophase.

Examples of polynuclear metallomesogens are few. Herein,1,2,4-triazole ligands were used to prepare mono- and polynuclear silver(I) triazole metallomesogens. Besides showing an SmA phase in the mesophase, two interesting properties were observed. First, higher ion conductivity is always found for the polynuclear complexes than for the mononuclear complexes with the same anion, an observation contrary to the knowledge that migration of a monomeric cation should be faster than that of a polymeric cation. Second, thermolysis of the polynuclear silver(I) triazole complexes in the assembled mesophase yielded Ag nanowires, in an excellent demonstration of the assembled nature of the polynuclear silver(I) ions in the thermolysis process.

Electrocatalytic Dihydrogen Production with a Robust Mesoionic Pyridylcarbene Cobalt Catalyst.

A Co(III) complex with a mesoionic pyridylcarbene ligand is presented. This complex is an efficient electrocatalyst for H2 production at very low overpotential and high turnovers when using a (glassy carbon) GC electrode. The corresponding triazole complexes display no catalytic activity whatsoever under identical conditions. The remarkable robustness of the Co-C(carbene) bond towards acids is likely responsible for the high efficiency of this catalyst. The present results thus open new avenues for carbene-based ligands for generating functional models for hydrogenases.

Hexaconazole–Cu complex improves the salt tolerance of Triticum aestivum seedlings

Hexaconazole is one of the triazole complexes that are broadly used as systemic fungicides with non-traditional plant growth regulator properties. Hexaconazole-Cu complex (Hex-Cu) is a new triazole derivative, and the biological effect of Hex-Cu has been rarely studied. In this work, we investigated the functions of Hex-Cu in regulating growth and the response to salt stress in the seedlings of Triticum aestivum. Pretreated with 60μmolL(-1) Hex-Cu, the seedling plants got increased root/shoot ratio by 42.0%, and the contents of chlorophyll and soluble protein were also increased by 38.1% and 27.9%, respectively. Furthermore, Hex-Cu alleviated the growth inhibition caused by salt stress, enabled the seedlings to maintain a higher proline content and lower malondialdehyde accumulation. The functions of Hex-Cu in regulating the expression of proline synthetase (P5CS and P5CR) genes were investigated by quantitative real-time PCR (qPCR). Under 100mmolL(-1) NaCl stress, the expression of P5CS and P5CR in the seedlings by Hex-Cu pretreatment were significantly up-regulated. It attributed to the enhanced salt tolerance in plants.

Tuning the spin-crossover temperature of polynuclear iron(II)–triazole complexes in solution by water and preparation of thermochromic fibers

The spin-crossover temperatures of alkyl-substituted Fe2+–triazole complexes with the counter ions 4-dodecylbenzenesulfonate (DBS−) and 2-naphthalenesulfonate (2ns−) are strongly influenced by water in the dissolved state, whereby the low-spin state is stabilized by water. This effect was found to be more pronounced in complexes with the counter ion DBS− compared to 2ns−. It appears that non-coordinating water molecules interact with the counter ion and thus alter the ligand-field splitting. Notably, the spin-crossover temperature depends only on the Fe2+/H2O ratio and not on the concentration of the complex in solution. As a consequence, the spin-crossover temperature can be controlled by the Fe2+/H2O ratio (for DBS− complexes within a temperature range of 7–47 °C), and on the other hand small amounts of water (in the ppm range) can be detected in apolar solvents. Furthermore, fibers of blends of the complex [Fe(C18trz)3](DBS)2 with ultra-high molecular weight polyethylene (UHMWPE) could be prepared. In these fibers, spin-crossover is maintained leading to pronounced thermochromism as in the bulk material, indicating essentially no interaction between UHMWPE and Fe2+–triazole complex.

Synthesis, crystal structure and properties of sandwich type compounds based on {AsW9} and a hexa-nuclear unit with three supporting TM–triazole complexes

Tree {AsW9}-based sandwich compounds exhibit good electrocatalytic activity, antiferromagnetic interactions, and inhibitory effect on proliferation of HeLa cells.

Synthesis and characterization of redox active cyrhetrene–triazole click products

We report the synthesis and characterization of two new cyclopentadienyl tricarbonyl rhenium(I) (cyrhetrene) complexes modified with a 1,4-disubstituted 1,2,3-triazole moiety. The two compounds, (η5-[4-phenyltriazol-1-yl]cyclopentadienyl) tricarbonyl rhenium(I), and (η5-[4-(4-aminophenyl)triazol-1-yl]cyclopentadienyl) tricarbonyl rhenium(I), were structurally characterized using 1H and 13C NMR, ATR-IR spectroscopy, UV–vis spectroscopy, mass spectrometry and X-ray crystallography where appropriate. The electrochemical behaviour of these two cyrhetrene–triazole complexes was explored using cyclic voltammetry, whereupon we observed that irreversible oxidation of the pendant 4-substituted-triazole moiety occurs before any electron transfer at the metal centre. This redox behaviour is in stark contrast to that of the analogous manganese(I) cymantrene–triazole derivatives, recently reported by our group.

Uncommon approach toward NHC–triazole complexes of palladium: Synthesis and applications

New imidazolium–triazole adducts have been synthesized. Their coordination to palladium has been studied and the catalytic activity of the corresponding complexes has been explored in the Suzuki–Miyaura Cross Coupling.

Cymantrene–Triazole “Click” Products: Structural Characterization and Electrochemical Properties

We report the first known examples of triazole-derivatized cymantrene complexes (η5-[4-substituted triazol-1-yl]cyclopentadienyl)tricarbonylmanganese(I), obtained via a “click” chemical synthesis, bearing a phenyl, 3-aminophenyl, or 4-aminophenyl moiety at the 4-position of the triazole ring. Structural characterization data using multinuclear NMR, UV–vis, ATR-IR, and mass spectrometric methods are provided, as well as crystallographic data for (η5-[4-phenyltriazol-1-yl]cyclopentadienyl)tricarbonylmanganese(I) and (η5-[4-(3-aminophenyl)triazol-1-yl]cyclopentadienyl)tricarbonylmanganese(I). Cyclic voltammetric characterization of the redox behavior of each of the three cymantrene–triazole complexes is presented together with digital simulations, in situ infrared spectroelectrochemistry, and DFT calculations to extract the associated kinetic and thermodynamic parameters. The trypanocidal activity of each cymantrene–triazole complex is also examined, and these complexes are found to be more active than cymantrene alone.

ChemInform Abstract: Self‐Assembly and Functionalization of Lipophilic Metal—Triazole Complexes in Various Media

AbstractReview: 50 refs.

Syntheses, structures and magnetic properties of a series of iron(II)-triazole crystalline coordination compounds: Solvent effect, different substituted groups and incomplete spin transition

Abstract Based on 4-substituted mono- and bis-triazole ligands 4-2-pyridyl-1,2,4-triazole (L1) and 2,6-(1,2,4-triazole-4-yl)-pyridine (L2), a series of iron(II)-triazole complexes, namely [Fe2(μ2-L1)3(L1)2(NCS)4] 2H2O (1), [Fe2(μ2-L1)3(L1)2(NCS)4] CH3OH CH3CH2OH (2) and [Fe(μ2-L2)2(NCS)2]n (3) have been isolated. For the Fe(II)-L1 system, though dinuclear complexes were obtained in both aqueous solution and methanol/ethanol solution for 1 and 2, respectively, anti-ferromagnetic interactions were found in 1 while incomplete spin transition phenomenon was found in 2. Low temperature structural analysis (100 K) of 2 is consistent with one of the Fe(II) centers within the dinuclear complex at low spin (LS) state and the other at high-spin (HS) state resulting in a [LS:HS] species. When L2 is used under the similar preparation method for 1–2, one-dimensional neutral iron (II) chain complex 3 is isolated. The different substituted groups and solvent effect are both important for self-assembly and different magnetic properties of these crystalline iron(II)-triazole complexes 1–3.

Efficient and Systematic Click-Based Synthetic Routes to Amino Acid Functionalized Metallatricarbadecaboranes

A general method for the systematic syntheses of amino acid functionalized metallatricarbadecaboranyl complexes has been developed that employs the copper-catalyzed click addition reactions of N-azidoacetyl amino acid methyl esters to a p-ethynylphenyl substituent at a cage carbon of the metallatricarbadecaboranyl cage. The trimethylsilyl-protected p-ethynylphenyl Li+[6-(p-((CH3)3SiC≡C)C6H4)-nido-5,6,9-C3B7H9–] (1) tricarbadecaboranyl anion was synthesized via the reaction of arachno-4,6-C2B7H12– with p-((CH3)3SiC≡C)C6H5CN. Reaction of 1 with (η5-C5H5)Fe(CO)2I and (η5-C5H5)Ru(CH3CN)3PF6 produced 1-(η5-C5H5)-2-(p-((CH3)3SiC≡C)C6H4)-closo-1,2,3,4-MC3B7H9 (M = Fe (2), Ru (3)). Deprotection of 2 and 3 with K2CO3 in MeOH/THF afforded the ethynyl derivatives 1-(η5-C5H5)-2-(p-(HC≡C)C6H4)-closo-1,2,3,4-MC3B7H9 (M = Fe (4), Ru (5)). Click addition of the model compound benzyl azide to 4 and 5 to form the triazole complexes, 1-(η5-C5H5)-2-(p-(1-(C6H5CH2)-1H-1,2,3-N3C2-4-)C6H4)-closo-1,2,3,4-MC3B7H9 (M = Fe (6), Ru (7)) confirmed the reactivity of the p-ethynyl group toward copper-catalyzed click azide addition, with the triazole-linked structure of 7 crystallographically established. Subsequent click addition reactions of the N-azidoacetyl amino acid methyl esters to 4 yielded a wide range of amino acid functionalized ferratricarbadecaboranyl complexes: 1-(η5-C5H5)-2-(p-(1-(Xaa-C(O)CH2)-1H-1,2,3-N3C2-4-)C6H4)-closo-1,2,3,4-FeC3B7H9 (Xaa = PheOMe (8), LeuOMe (9), ValOMe (10), MetOMe (11), AlaOMe (12), TryOMe (13)).

Electrochemical Characterization of Adsorbed and Immobilized Cu Triazole Complexes: Some Mechanistic Aspects

We have synthesized and electrochemically characterized a variety of adsorbed Cu complexes of substituted triazoles for use as catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. To validate our methods versus previously reported Cu catalysts, we focused our preliminary work on the synthesis and electrochemical characterization of the ORR catalytic activity of adsorbed Cu diamino triazole (Cu-DATZ) complexes. The effects on the performance of parameters such as Cu salts, ligand to metal ratio, adsorption temperature and carbon pretreatment were studied. To develop a deeper understanding of these materials we examined ORR mechanistic aspects such as the number of electrons transferred and the reaction order with respect to oxygen.

Electrochemical Characterization of Adsorbed and Immobilized Cu Triazole Complexes: Some Mechanistic Aspects

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Reactivity study of arene(azido)ruthenium N∩O-base complexes with activated alkynes

Substitution reaction of chloro η6-arene ruthenium N∩O-base complexes [(η6-arene)Ru(N∩O)Cl] [N∩O=pyrazine-2-carboxylic acid (pca-H), 8-hydroxyquinoline (hq-H); arene=p-iPrC6H4Me, N∩O=hq (1); arene=C6Me6, N∩O=hq (2)] with NaN3 yield the neutral arene ruthenium azido complexes of the general formula [(η6-arene)Ru(N∩O)N3] [N∩O=pca, arene=p-iPrC6H4Me (3), arene=C6Me6 (4); N∩O=hq, arene=p-iPrC6H4Me (5), arene=C6Me6 (6)]. These complexes undergo [3+2] dipolar cycloaddition reaction with activated alkynes dimethyl and diethyl acetylenedicarboxylates to yield the arene triazole complexes [(η6-arene)Ru(N∩O){N3C2(CO2R)2}] [N∩O=pca, R=Me, arene=p-iPrC6H4Me (7), C6Me6 (8); R=Et, arene=p-iPrC6H4Me (9), C6Me6 (10); N∩O=hq, R=Me, arene=p-iPrC6H4Me (11) C6Me6 (12); R=Et, arene=p-iPrC6H4Me (13), C6Me6 (14)]. On the bases of proton NMR study, in the above triazole complexes N(2) isomers are assigned with dimethylacetylenedicarboxylate whereas N(1) isomers with diethylacetylenedicarboxylate. All complexes have been characterized by IR and NMR spectroscopy as well as by elemental analysis. The molecular structures of the azido complexes [(η6-p-iPrC6H4Me)Ru(pca)N3] (3), [(η6-p-iPrC6H4Me)Ru(hq)N3] (5) and [(η6-C6Me6)Ru(hq)N3] (6) have been established by single crystal X-ray diffraction studies.

Electrochemical Characterization of Cu Triazole Complexes as Oxygen Reduction Reaction Catalysts for Proton Exchange Fuel Cells Applications

not Available.

Synthesis and characterisation of luminescent rhenium tricarbonyl complexes with axially coordinated 1,2,3-triazole ligands

A series of 1-alkyl-4-aryl-1,2,3-triazoles (1-methyl-4-phenyl-1,2,3-triazole (1a); 1-propyl-4-phenyl-1,2,3-triazole (1b); 1-benzyl-4-phenyl-1,2,3-triazole (1c); 1-propyl-4-p-tolyl-1,2,3-triazole (1d)) have been prepared through a one-pot procedure involving in situ generation of the alkyl azide from a halide precursor followed by copper catalysed alkyne/azide cycloaddition (CuAAC) with the appropriate aryl alkyne. Cationic Re(I) complexes [Re(bpy)(CO)(3)(1a-d)]PF(6) (2a-d) were then prepared by stirring [Re(bpy)(CO)(3)Cl] with AgPF(6) in dichloromethane in the presence of ligands 1a-d. X-ray crystal structures were obtained for 2a and 2b. In the solid state, 2a adopts a highly distorted geometry, which is not seen for 2b, in which the plane of the triazole ligand tilts by 13° with respect to the Re-N bond as a result of a π-stacking interaction between the Ph substituent and one of the rings of the bpy ligand. This π-stacking interaction also results in severe twisting of the bpy ligand. Infrared spectra of 2a-d exhibit ν(CO) bands at ∼2035 and ∼1926 cm(-1) suggesting that these ligands are marginally better donors than pyridine (ν(CO) = 2037, 1932 cm(-1)). The complexes are luminescent in aerated dichloromethane at room temperature with emission maxima at 542 to 552 nm comparable to that of the pyridine analogue (549 nm) and blue shifted relative to the parent chloride complex. Long luminescent lifetimes are observed for the triazole complexes (475 to 513 ns) in aerated dichloromethane solutions at room temperature.

Adding diversity to ruthenium(II)–arene anticancer (RAPTA) compounds via click chemistry: The influence of hydrophobic chains

The application of click chemistry to develop libraries of organometallic ruthenium–arene complexes with potential anticancer properties has been investigated. A series of ruthenium–imidazole–triazole complexes, with hydrophobic tails, were prepared from a common precursor via click chemistry. The tail could be attached to the ligand prior to coordination to the ruthenium complex or following coordination, the former giving the product in superior yield. The complexes were screened for cytotoxicity in tumourigenic and non-tumourigenic cell lines, and while the compounds were only moderately cytotoxic, good selectivity for tumourigenic cells was observed.

ChemInform Abstract: The Inhibition of Zinc Corrosion by Bisaminotriazole and Other Triazole Derivatives.

Abstract The inhibition of zinc corrosion by various triazole derivatives was investigated with respect to dependence on pH, potential E , inhibitor concentration c Inh , zinc ion concentration c Zn 2+ , and exposure time t . Current potential curves and measurements of weight loss show that 3-amino-5-heptyl-1,2,4-triazole (AHT) is an excellent inhibitor of zinc corrosion in acid and weak alkaline solutions, while bisaminotriazole (BAT4) gives the best inhibition efficiency expecially at pH 9 and low inhibitor concentrations. Capacity potential curves and XPS-measurements show the formation of protective triazole layers with a maximum thickness of about 3 nm. The chemical analysis of insoluble zinc triazole complexes precipitated in solution yields a stoichiometric ratio of Zn 2+ and the triazole ring of 1 : 2. The presence of zinc triazole complex on the zinc surface is shown by XPS spectroscopy. The solubility, adsorbability and hydrophobicity of the triazole molecules and the stability of the zinc-triazole complexes are found to be the most important factors influencing the inhibition efficiency of the triazole derivatives under varying conditions.

Lipid-Packaged Linear Iron(II) Triazole Complexes in Solution: Controlled Spin Conversion via Solvophobic Self-Assembly

Linear Fe(II) 1,2,4-triazole complexes with lipid counteranions are newly developed. These complexes show sharp and reversible spin conversion in toluene, with temperatures significantly higher (by 20-100 K) than the spin crossover temperatures observed in the crystalline states. This is accounted for in terms of increased metal-ligand interactions in organic media, which is caused by solvophobic compaction of charged coordination chains. In atomic force microscopy, developed nanowires are observed for low spin (LS) complexes. On the other hand, fragmented nanostructures are seen for high spin (HS) complexes, indicating that the spin conversion in solution is governed by a self-assembly process. The lipid packaging of charged coordination chains thus provides powerful means to improve and regulate their functions via solvophobic self-assembly.