1-methylimidazole Ligands Research Articles

Heteronuclear cadmium(II)/cobalt(III) cyanide coordination polymers with 1-methylimidazole and 1-ethylimidazole ligands: synthesis, characterization and catalytic activities

Two new heteronuclear Cd(II)/Co(III) compounds, {[Cd(1-meim)3Cd0.5(1-meim)Co(μ-CN)4(CN)2]}n (1) and {[Cd(1-etim)3Cd0.5(1-etim)2Co(μ-CN)3(CN)3]⋅H2O}n (2) (1-meim: 1-methylimidazole, 1-etim = 1-ethylimidazole), have been synthesized and characterized using elemental analysis, FT-IR and Raman spectroscopy, single-crystal X-ray diffraction techniques. The single crystal X-ray study shows that the compound 1 exhibited a 1D double chain structure and is further linked into 3D supramolecular architectures through CH⋅⋅⋅N and π⋅⋅⋅π interactions. Whereas the compound 2 displayed 2D network which is extended into a 3D supramolecular framework by OH⋅⋅⋅N hydrogen bonds and CH∙∙∙π interactions. In 1 and 2, each Co(III) ion is coordinated by six carbon atoms from cyanide ligands, thus showing an octahedral coordination geometry. Cd1 and Cd2 ions exhibited two different geometries, distorted trigonal bipyramidal and octahedral. Furthermore, phase purities, catalytic and thermal properties were investigated.

Full Equilibrium Picture in Aqueous Binary and Ternary Systems Involving Copper(II), 1-Methylimidazole-Containing Hydrazonic Ligands, and the 103-112 Human Prion Protein Fragment.

In this work, we describe two novel 1-methylimidazole N-acylhydyrazonic ligands and their interaction with copper(II) in solution. Binary systems constituted by each of these hydrazones and the metal ion were studied by potentiometric titrations. The magnitude of their affinities for zinc(II) was also determined for the sake of comparison. Additionally, a full evaluation of the copper(II) chelation profile of the new ligands in ternary systems containing a human prion protein fragment was performed. Mixed ligand complexes comprising the HuPrP103-112 fragment, copper(II) ions, and an N-acylhydrazone were characterized by potentiometry, ultraviolet-visible spectroscopy, and circular dichroism. Some of these species were also identified by electrospray ionization mass spectrometry and unequivocally assigned through their isotopic distribution pattern. To the best of our knowledge, this is the first report concerning the stability of ternary complexes involving a hydrazonic metal-protein interaction modulator, copper, and a peptide. The ability of N-acylhydrazones to prevent peptide oxidation was also examined. Both ligands can partially prevent the formation of the doubly oxidized product, a process mediated by copper(II) ions. Oxidative stress is considered an important hallmark of neurodegenerative diseases such as prion-related spongiform encephalopathies. In this context, active intervention with respect to the deleterious copper-catalyzed methionine oxidation could represent an interesting therapeutic approach.

Bis(1-methyl-imidazole)[meso-α,α,α,α-tetra-kis(o-nicotinamido-phen-yl)porphinato]iron(II)-1-methyl-imidazole-tetra-hydro-furan (1/1/1.5).

In the title compound, [FeII(C68H44N12O4)(C4H6N2)2]·C4H6N2·1.5C4H8O, the central FeII ion is coordinated by four pyrrole N atoms of the porphyrin core and two N atoms of the 1-methyl-imidazole ligands in the axial sites. One 1-methyl-imidazole and one and a half tetra-hydro-furan solvent mol-ecules are also present in the asymmetric unit. The complex exhibits a near planar porphyrin core conformation, in which the iron centre is slightly displaced towards the hindered porphyrin side (0.01 Å). The average Fe-Np (Np refers to the pyrrole nitro-gen atoms in the porphyrin) bond length is 1.990 (9) Å, and the axial Fe-NIm (NIm refers to the imidazole nitro-gen atoms) bond lengths are 1.993 (3) and 2.004 (3) Å. The dihedral angle between the two coordinated 1-methyl-imidazole planes is 56.6 (2)°. The dihedral angles between the 1-methyl-imidazole planes and the planes of the closest Fe-Np vector are 16.8 (2) and 39.8 (2)°. N-H⋯N and N-H⋯O inter-actions are observed in the crystal structure.

Antibacterial and cytotoxicity assay of two new Zn(ii)complexes: Synthesis, characterization, X-Ray structure, topology, Hirshfeld surface and thermal analysis

Nano-structures of two mononuclear Zn(II) complexes, [ZnL2Br2] (1) and [ZnL6].2(I) (2) L = 1-methyl imidazole ligand, were synthesized using a sonochemical method and characterized by infrared spectroscopy (IR), UV-Visible, X-Ray powder diffraction (XRPD), scanning electron microscopy (SEM) and elemental analyses. The single-crystal X-ray (SCXA) data of compounds 1 and 2 exhibited different coordination environment of the Zn2+ ions: distorted tetrahedral in 1 and distorted octahedral in 2. The topological analysis showed that compounds 1 and 2 present novel topology for net: 1.4M5–1 and 1.6M7–1, respectively. The thermal stability of compounds 1 and 2 was investigated through differential scanning calorimetry analyses (DSC) and thermal gravimetric analyses (TGA). Nanostructures of zinc(II) oxide was obtained by simultaneous calcination various zinc(II) complexes at 500 °C and, then, were characterized by IR, SEM and XRD. Moreover, the in vitro antibacterial activities of zinc(II) complexes was investigated against gram-positive (S. aureus) and gram-negative (E. coli) bacteria. The results exhibited appropriate antibacterial activities. MTT assay was used for cytotoxicity of the crystals and nanostructures of compounds 1 and 2.

A new sandwich type transition metal complex based on tungstobismuthates and 1-methylimidazole ligands exhibiting photocatalytic properties

A new sandwich-type transition metal complex based on tungstobismuthates and 1-methylimidazole ligands Na7(mim)2[{Na(H2O)2}3{CoII(mim)}3(BiIIIWVI9O33)2]·9H2O (1) (mim = 1-methylimidazole) has been successfully isolated in aqueous solution. The composition and structure were established by the single crystal X-ray diffraction analysis, elemental analysis, IR spectroscopy. Single-crystal X-ray diffraction and TG analyses indicate that compound 1 consists of two tri-vacant [α-B-BiIIIWVI9O33]9- units linked through three cobalt ions. All the CoII ions were sandwiched in the middle and bonded with terminal oxo atoms from [α-B-BiIIIWVI9O33]9- units as well as 1-methylimidazoles. Photocatalytic experiment indicates that compound 1 exhibit good catalytic activities for photodegradation of RhB under UV irradiation.

Six-coordinate nitrosyl complex of Co-meso-tetra-p-tolylporphyrin with a trans-1-methylimidazole ligand

Electron absorption and Fourier-transform IR spectroscopy was used to determine that the reaction of 1-methylimidazole (1-MeIm) with a nitrosyl complex of meso-tetra-p-tolylporphyrinate cobalt (Co(TTP)(NO)) at 210—240 K led to the formation of the six-coordinate complex (1-MeIm)Co(TTP)(NO), which was stable at low temperatures both in the solid state and in a solution of toluene. Based on the temperature dependence of the equilibrium constants, the thermodynamic parameters of complexation were calculated, which indicated a weak binding of the 1-methylimidazole ligand with the Co-porphyrin nitrosyl complex.

Single-molecule magnet behavior in a mononuclear dysprosium(iii) complex with 1-methylimidazole

Using 1-methylimidazole ligand and Dy(hfac)3·2H2O salt achieved a new single-molecule magnet of [Dy(hfac)3·(1-MeIm)2] with an energy barrier of 42.54 K.

Synthesis, crystal structure and spectroscopic properties of one-dimensional zinc(II)–cyanide complex with 1-methylimidazole, [Zn(μ-CN)(CN)(1-meim)]n

Abstract A new one-dimensional Zn(II)–cyanide complex with 1-methylimidazole ligand, [Zn(μ-CN)(CN)(1-meim)]n (1-meim: 1-methylimidazole) has been synthesized and characterized by spectral (FT-IR and Raman) methods, elemental analysis, thermal (TG, DTG and DTA) analysis and single crystal X-ray diffraction techniques. The complex crystallizes in the monoclinic system, P2 1 space group. The asymmetric unit contains one Zn(II), one 1-meim and two cyanide ligands. The coordination sphere of the Zn(II) ion exhibits a distorted tetrahedral geometry. In the crystal structure, the symmetry related zinc(II) atoms are bridged by the cyanide anions to form one dimensional chains running along the b-axis. Intermolecular C–H···N hydrogen bonds link the adjacent polynuclear chains forming two dimensional layers through the R 18 18 ( 2 ) $R_{18}^{18}(2)$ ring motifs, where the layers formed are oriented in parallel to (020).

Crystal structure of bis-(1-methyl-1H-imidazole-κN (3))(5,10,15,20-tetra-phenyl-porphyrinato-κ(4) N)iron(II)-1-methyl-1H-imidazole (1/2).

The title compound, [Fe(C44H28N4)(C4H6N2)2]·2C4H6N2, is a six-coordinate FeII–porphyrinate complex with the metal located on a center of inversion and coordinated by two axial 1-methyl­imidazole ligands; the complex crystallizes as a 1-methyl­imidazole disolvate. The 1-methyl­imidazole group bonded to the FeII atom [occupancy ratio 0.789 (4):0.211 (4)] and the unbound 1-methyl­imidazole mol­ecule [0.519 (4):0.481 (4)] were disordered. The average Fe—N(porphyrinate) bond length is 1.998 (3) Å and the axial Fe—N(imidazole) bond length is 1.9970 (12) Å. In the crystal, mol­ecules are linked into a three-mol­ecule aggregate by two weak C—H⋯N inter­actions.

Observation in the gas phase of the ligation of 1-methylimidazole to hemoprotein mimics.

Hemoprotein mimics, cobalt picket fence porphyrins have been prepared in the gas phase as neutral molecules for the first time. Their ligation properties have been studied with 1-methylimidazole and compared with those of other cobalt porphyrins, tetraphenyl porphyrin, and cobalt protoporphyrin IX chloride, in view of studying the sterical properties of the ligation. It is shown that the cobalt picket fence porphyrin can only accept one 1-methylimidazole ligand in contrast to less sterically crowded porphyrins like cobalt tetraphenylporphyrin that present two accessible ligation sites. The femtosecond dynamics of these ligated systems have been studied after excitation at 400 nm, in comparison with the unligated ones. The observed transients are formed in much shorter times, 30 fs for the ligated species, as compared to free species (100 fs), supporting the porphyrin to metal charge transfer nature of these transients. The similar decays of the ligated transients <1 ps reveal the absence of photodissociation of the cobalt-1-methylimidazole bond at this step of evolution.

Synthesis, spectroscopy, DFT and crystal structure investigations of 3-methoxy-2-hydroxybenzaldehyde S-ethylisothiosemicarbazone and its Ni(II) and Mo(VI) complexes

Four new compounds, 3-methoxy-2-hydroxybenzaldehyde S-ethylisothiosemicarbazone (H2L), (3-methoxy-2-hydroxybenzaldehyde S-ethyl-isothiosemicarbazonato-N,N′,O)-(1-methylimidazole)-nickel(II) (1), (3-methoxy-2-hydroxybenzaldehyde S-ethyl-isothiosemicarbazonato-N,N′,O)-(pyridine)-nickel(II) (2) and cis-dioxo-dimethylsulfoxide-(3-methoxy-2-hydroxybenzaldehyde S-ethyl-isothiosemicarbazonato-N,N′,O)-molybdenum(VI) (3), have been synthesized and characterized by molar conductivity, FT-IR, UV–Vis, 1H NMR, elemental analysis and X-ray crystal structures. The crystal structure of H2L reveals that the NH2 and S–R moieties are in cis positions with respect to each other, and the molecule adopts the Z configuration. The ligand is bonded to the central metals as a binegatively tridentate agent. The Ni(II) atom adopts square planar geometry with this ligand, with the 1-methylimidazole and pyridine ligands occupying the remaining position in complexes 1 and 2 respectively. The Mo(VI) center in complex 3 is six coordinated by the ligand, two oxido groups and one DMSO molecule. The Density Functional Theory approach has been successfully used for the investigation of the ground state, frequency assignment and natural bond analysis.

Structural, spectroscopic and magnetic properties of thiocyanate complexes of Mn(II), Ni(II) and Cu(II) with the 1-methylimidazole ligand

New [M(SCN)2(L)4] complexes, where M=Mn(II), Ni(II), Cu(II) and L=1-methylimidazole have been synthesized. The electronic structures of the complexes were calculated using the DFT method, and the descriptions of frontier molecular orbitals and the relocation of the electron density of the compounds were determined. The crystal field splitting, Racah repulsion and nephelauxetic parameters were determined from the electronic spectra of the complexes. The magnetic properties revealed almost ideal paramagnetism for all the complexes under study, evidenced by values close to zero for both the Curie–Weiss temperature and the imaginary part of the ac magnetic susceptibility.

Structure, dynamics and catalytic activity of palladium(II) complexes with imidazole ligands

Several palladium complexes of the type [Pd(im) 2Cl 2], [Pd(im) 3Cl]Cl, and [Pd(im) 4]Cl 2 (im = imidazole 1, 1-methylimidazole 2, 1,2-dimethylimidazole 3, 1-butylimidazole 4, 4a, 1-phenylimidazole 6, 1-phenylimidazoline 7, and 1-methylimidazoline 8) were prepared and structurally characterized. The square planar structure of two new complexes with the composition [Pd(im) 4]Cl 2 ( 2b, 4b) was confirmed by X-ray analysis. In solution, exchange of imidazole ligands leading to heteroleptic products was evidenced by ESI-MS studies. Two bis-ligated complexes, bearing 1-methylimidazole ( 2a) and 1-propoxymethylimidazole ( 5) ligands, were obtained in the reaction of palladium with imidazoles formed by deprotection of one nitrogen atom in the respective imidazolium halides. Catalytic Suzuki–Miyaura reactions were carried out using the obtained palladium complexes in isopropanol–water solution. High yields of the cross-coupling products were obtained at 40 and 60 °C when 2-bromotoluene, 4-bromotoluene, and 4-bromoanizole were used as substrates.

Influence of Steric Hindrance on the Core Geometry and Sulfoxidation Chemistry of Carboxylate-Rich Diiron(II) Complexes

The asymmetric terphenyl-2'-carboxylate ligand 3,5-dimethyl-1,1':3',1' '-terphenyl-2'-carboxylate, -O2CArPh,Xyl, was prepared in high yield. This ligand facilitates the assembly of the diiron(II) complexes [Fe2(micro-O2CArTol)2(O2CArPh,Xyl)2(THF)2] [2, -O2CArTol=2,6-di-p-tolylbenzoate], [Fe2(micro-O2CArTol)2(O2CArPh,Xyl)2(pyridine)2] (5), [Fe2(micro-O2CArPh,Xyl)2-(O2CArPh,Xyl)2(THF)2] (3), and [Fe2(micro-O2CArPh,Xyl)2(O2CArPh,Xyl)2(pyridine)2] (6), all of which have a windmill geometry. The iron-iron distance of 3.355[10] A in 6 is approximately 1 A shorter than that in the analogue [Fe2(micro-O2CArTol)2(O2CArTol)2(pyridine)2] (4) and similar to the approximately 3.3 A metal-metal separation at the active site of the reduced diiron(II) form of the soluble methane monooxygenase hydroxylase enzyme (MMOHred). A series of ortho-substituted picolyl-based ligands, 2-picSMe, 2-picSEt, 2-picStBu, 2-picSPh, 2-picSPh(Me3) (Ph(Me3)=mesityl), and 2-picSPh(iPr3) (Ph(iPr3)=2,4,6-triisopropylphenyl), were prepared and allowed to react with [Fe2(micro-O2CAr)2(O2CAr)2(THF)2] to produce [Fe2(micro-O2CAr)3(O2CAr)(picSR)] (7-13, Ar=ArTol or ArPh,Xyl) complexes in 45-87% yields. The substrates tethered to the pyridine N-donor ligands picSR, where R=Me, Et, tBu, or Ph, coordinate to one iron atom of the diiron(II) center by the nitrogen and sulfur atoms to form a five-membered chelate ring. The Fe-S distance be-comes elongated with increasing steric hindrance imparted by the R group. The most sterically hindered ligands, 2-picSPh(Me3) and 2-picSPh(iPr3), bind to the metal only through the pyridine nitrogen atom. The reactions of several of these complexes with dioxygen were investigated, and the oxygenated products were analyzed by 1H NMR spectroscopy and GC/MS measurements following decomposition on a Chelex resin. The amount of sulfoxidation product is correlated with the Fe...S distance. The ratio of oxidized to unoxidized thioether substrate varies from 3.5, obtained upon oxygenation of the weakly coordinated 2-picSPh ligand in 10, to 1.0, obtained for the bulky 2-picSPh(iPr3) ligand in 12, for which the iron-sulfur distance is >4 A. External thioether substrates were not oxidized when present in oxygenated solutions of paddlewheel and windmill diiron(II) complexes containing 1-methylimidazole or pyridine ligands, respectively.

Sandwich transitional metal complexes with tungstobismuthates and 1-methylimidazole ligands: Syntheses, structures and magnetic properties

Two novel sandwich-type coordination compounds of tungstobismuthate Na 9[{Na(H 2O) 2} 3{Co II(mim)} 3(Bi IIIW VI 9O 33) 2]·36H 2O ( 1) and Na 7H 2[{Na(H 2O) 2} 3{Mn II(mim)} 3(Bi IIIW VI 9O 33) 2]·21H 2O ( 2) (mim = 1-methylimidazole) have been synthesized in alkaline aqueous solution. Their composition and structures were established by elemental analyses, IR spectra, and single crystal X-ray diffraction. These two complexes consist of two tri-vacant [α-B-Bi IIIW VI 9O 33] 9− moieties linked through three Cu II or Mn II and three Na + ions. These Na + cations around the complex anion were bonded with some terminal and bridging oxo atoms from the complex anion and water molecules. In addition to tungstobismuthate ligands, 1-methylimidazoles also coordinate to sandwich transitional metal ions. Magnetic measurement indicates the existence of antiferromagnetic interaction between the trimeric transitional metal ions for 1 and 2.

Interactions of 1-Methylimidazole with UO2(CH3CO2)2 and UO2(NO3)2: Structural, Spectroscopic, and Theoretical Evidence for Imidazole Binding to the Uranyl Ion

The first definitive high-resolution single-crystal X-ray structure for the coordination of the 1-methylimidazole (Meimid) ligand to UO2(Ac)2 (Ac = CH3CO2) is reported. The crystal structure evidence is confirmed by IR, Raman, and UV-vis spectroscopic data. Direct participation of the nitrogen atom of the Meimid ligand in binding to the uranium center is confirmed. Structural analysis at the DFT (B3LYP) level of theory showed a conformational difference of the Meimid ligand in the free gas-phase complex versus the solid state due to small energetic differences and crystal packing effects. Energetic analysis at the MP2 level in the gas phase supported stronger Meimid binding over H2O binding to both UO2(Ac)2 and UO2(NO3)2. In addition, self-consistent reaction field COSMO calculations were used to assess the aqueous phase energetics of combination and displacement reactions involving H2O and Meimid ligands to UO2R2 (R = Ac, NO3). For both UO2(NO3)2 and UO2(Ac)2, the displacement of H2O by Meimid was predicted to be energetically favorable, consistent with experimental results that suggest Meimid may bind uranyl at physiological pH. Also, log(Knitrate/KAc) calculations supported experimental evidence that the binding stoichiometry of the Meimid ligand is dependent upon the nature of the reactant uranyl complex. These results clearly demonstrate that imidazole binds to uranyl and suggest that binding of histidine residues to uranyl could occur under normal biological conditions.

An unexpected chelate conformation in trans-[(R)-N,N'-bis(alpha-phenylsalicylidene)propane-1,2-diaminato(2-)]bis(1-methyl-1H-imidazole-kappaN3)cobalt(III) perchlorate.

The title compound, [Co(C29H24N2O2)(C4H6N2)2]ClO4, contains an optically active tetradentate Schiff base ligand in an equatorial plane and two 1-methylimidazole ligands at apical positions. The central N-C-C-N chelate ring of the Schiff base ligand has an envelope structure with a lambda conformation, which is different from the solution structure predicted from circular dichroism and 1H NMR spectra.

Synthesis and solid-state molecular structures of nitrosoalkane complexes of iron porphyrins containing methanol, pyridine, and 1-methylimidazole ligands

Nitrosoalkanes belong to the family of C-nitroso compounds and are known to bind to the iron center in heme proteins. We have prepared and characterized a series of new nitrosoalkane heme model complexes of the form (por)Fe(RNO)(L) (por=porphyrinato dianion; R=isopropyl; L=MeOH, pyridine, 1-methylimidazole) by infrared and 1H NMR spectroscopy and X-ray crystallography. Within the set of octaethylporphyrinato (OEP) compounds, the infrared stretching frequencies of the NO groups decrease in the order (OEP)Fe( i PrNO)(MeOH) · MeOH (1433 cm −1) > (OEP)Fe( i PrNO)(py) (1429 cm −1) > (OEP)Fe( i PrNO)(1-MeIm) (1423 cm −1), reflecting the increased backdonation of electron density in the 1-methylimidazole derivative. The molecular structures of the compounds as determined by crystallography reveal N-binding of the nitrosoalkane ligands to the formally ferrous metal centers.

NO Release from trans-[Ru(NH3)4L(NO)]3+Complexes Upon Reduction (L = 1-Methylimidazole or Benzoimidazole)

The synthesis, characterization and reactivity of trans-[Ru(NH3)4(L)NO](PF6)3(L = benzoimidazole or 1-methylimidazole in trans position to NO) are presented. 1H-n.m.r. spectroscopy data indicate that the benzoimidazole and 1-methylimidazole ligands are coordinated to RuII through carbon and nitrogen, respectively. The nitrosyl stretching frequencies [ν(NO) > 1900 cm−1] suggest that the coordinated nitrosyl has substantial NO+ character. The complexes undergo a single-electron reduction (E0≈−0.245 versus NHE), which involves the coordinated nitrosyl. Dissociation of NO in the reduced species is facilitated by the 1-methylimidazole ligand, which is not observed for the benzoimidazole species. The complex with 1-methylimidazole does not suffer hydroxide attack on the NO+, at least at pH values lower than 11.

(1-Methylimidazole)(N-salicylidene-rac-glutamato)copper(II)

The title racemic compound, [Cu(C12H11NO5)(C4H6N2)], adopts a square-planar copper(II) coordination mode with the tridentate N-salicylidenglutamato Schiff base dianion and the 1-methylimidazole ligand. Dimers of centrosymmetrically related molecules are formed. The theoretical investigation of the electronic structure of the title compound by the B3LYP method is presented.