Direct electrochemical synthesis of metal complexes of phthalocyanines and azomethines as model compounds: advantages and problems of this method versus traditional synthetic techniques

A comparison of traditional and electrochemical synthetic techniques for obtaining metal complexes of azomethine and phthalocyanine is reported. It is shown that the electrochemical method affords azomethinic coordination compounds free of anions of precursors and with higher yields at ambient temperature. Electrolysis in a solid phase of phthalonitrile using a high-surface platinum cathode leads to metal-free phthalocyanine and metal phthalocyaninates at 0–25°C. The typical problems of the electrosynthetic procedures in different conditions are discussed in detail.     

Development of a new traceless aniline linker for solid-phase synthesis of azomethines. Application to parallel synthesis of a rod-shaped liquid crystalline library

A new traceless linker was developed to synthesize a library of 42 compounds possessing an azomethine linkage using combinatorial solid-phase parallel synthesis. The loading of the substrates on a solid support and cleavage from the solid support were performed by an imine synthesis and by imine-exchanged process under mild conditions, respectively. Thioesters with a hydroxy group on the central core exhibited liquid crystalline properties with the widest transition temperatures in the library.     

Studies of bimetallic carboxylates: their synthesis, characterization, biological activity and X-ray structure

Ten novel diorganotin dicarboxylates containing germanium in the carboxylate ligand have been synthesized and their structures have been characterized by IR, Mössbauer and multinuclear NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopies and X-ray diffraction. Also, the twodiastereotopic protons of the methylene group which are directly attached to the chiral center in these compounds have been successfully analyzed for the first time. The resulted ABX system gives three coupling constants and three chemical shifts. The single crystal X-ray analysis of precursor (p-CH₃C₆H₄)₃GeCH(p-CH₃C₆H₄)CH₂COOH revealed the dimeric structure of the molecule through H-bonding between carboxylic acid groups in a conventional manner. The results of their biological activity suggest that the materials have potential to be used as drugs.     

Conjugated 4-methoxybipyrrole thiophene azomethines: synthesis, opto-electronic properties, and crystallographic characterization

In the search of functional materials with improved electrochromic properties, thiophenes and asymmetric bipyrroles have been conjugated with azomethine units. 4-Methoxy-2,2'-bipyrroles 3-6 were first synthesized by a general route from 4-hydroxyproline and converted subsequently to dialdehydes 8-15, which underwent condensations with different aminothiophenes to provide azomethine conjugates 14-18 and 20-22. The crystallization and X-ray analysis of 20 showed the heterocycles and azomethine bonds were all co-planar with the heterocycles adopting an anti-parallel arrangement. These configurations result in extended conjugation and enhanced opto-electronic properties of the azomethines. Oxidation potential (E(pa)) was tailored by modification of the substitution pattern of the terminal thiophenes and central pyrroles of the azomethines. The combined low E(pa) and extended azomethine degree of conjugation resulted in stark color transitions occurring between their neutral and oxidized states. Reversible color formation was induced both electrochemically and by doping/de-doping with trifluoroacetic acid/triethylamine.     

Dioxidouranium isothiosemicarbazone coordination compounds: synthesis,characterization, crystal structure,and thermal behavior

Five uranium complexes with UO₂L′(solv) formula (L′: prepared by condensation reaction between 2-hydroxyacetophenon S-pentyl isothiosemicarbazone (H₂L) and 5-bromosalicylaldehyde (Sal); solv: ethanol (1), 2-propanol (2), 2-butanol (3), ethylene glycol (4), 1,2-propanediol (5)) were synthesized through template reactions between H₂L, Sal, and UO₂(CH₃COO)₂?2H₂O for 1 and recrystallization of 1 in appropriate solvents for the other complexes. The compounds are characterized by melting point, elemental analyses, FT-IR, ¹H NMR, ¹³C NMR, TGA, and X-ray crystallography. Molecular structures of the obtained crystals, determined by X-ray diffraction analysis, showed that the complexes have distorted pentagonal bipyramidal geometry. In all complexes, the bianionic tetradentate ligand (N₂O₂) with phenolic oxygens (O3, O4), thioamidic and azomethine nitrogen donor atoms is coordinated to the metal center in equatorial positions and the solv molecules occupied the fifth equatorial site and finally linear UO₂ is located in axial position. The thermal behavior of the complexes was studied with TGA and DTG data and the results revealed three weight loss stages. The Coats–Redfern method is used for all degradation steps to determine kinetic parameters.     

Microwave assisted synthesis,characterization and biological evaluation of palladium and platinum complexes with azomethines

Reactions of 3-acetyl-2,5-dimethylthiophene with thiosemicarbazide and semicarbazide hydrochloride resulted in the formation of new heterocyclic ketimines, 3-acetyl-2,5-dimethylthiophene thiosemicarbazone (C₉H₁₃N₃OS₂ or L¹H) and 3-acetyl-2,5- dimethylthiophene semicarbazone (C₉H₁₃N₃OS or L²H), respectively. The Pd(II) and Pt(II) complexes have been synthesized by mixing metal salts in 1:2 molar ratios with these ligands by using microwave as well as conventional heating method for comparison purposes. The authenticity of these ligands and their complexes has been established on the basis of elemental analysis, melting point determinations, molecular weight determinations, IR, ¹H NMR and UV spectral studies. These studies showed that the ligands coordinate to the metal atom in a monobasic bidentate manner and square planar environment around the metal atoms has been proposed to the complexes. Both the ligands and their complexes have been screened for their antimicrobial activities. The antiamoebic activity of both the ligands and their palladium compounds against the protozoan parasite Entamoeba histolytica has been tested.     

The synthesis and spectral characterization of novel nitrodiene compounds from thiols

Novel S-, S,S- and S,O-substituted nitrodiene compounds were synthesized from the reactions of 2-nitro-pentachloro-1,3-butadiene (1) and various thiols in different solvent media. The N,S-substituted nitrodienes also were achieved by the reactions of S-substituted nitrodienes with using morpholine, piperidine and piperazine derivatives. All of the new compounds were characterized by elemental analysis, UV-VIS, FT-IR, ¹H-NMR, NMR and mass spectroscopy.     

Organocadmium aminoalcoholates: synthesis, structure, and materials chemistry

The novel methylcadmium aminoalkoxides MeCd(dmae) (Hdmae = dimethylaminoethanol), MeCd(bdmap) [Hbdmap = 1,3- bis-(dimethylamino)-propan-2-ol], and MeCd(tdmap) [tdmap = 1,3- bis(dimethylamino)-2-(dimethylaminomethyl)-propan-2-ol] have been synthesized and structurally characterized. MeCd(dmae) (1) forms a tetrameric heterocubane with a Cd4O4 core, while MeCd(bdmap) (2) is trimeric and MeCd(tdmap) (3) is a dimer. Only in the case of MeCd(dmae) are all the ligand donors fully utilized. In solution, MeCd(tdmap) undergoes a Schlenk equilibrium, with Me2Cd and Cd(tdmap)2 evident at 218 K. The structure and solution-state chemistry of Cd(tdmap)2 (5) have been independently studied and, in the solid-state, found to exist as a dimer whose coordination number at cadmium (CN = 6) is greater than in the organocadmium complexes (CN = 4, 5). MeCd(tdmap) has been used as a single-source precursor for CdO films by LPCVD with a glass substrate temperature of only 140 degrees C. Evidence is also presented for the formation of a heterometallic precursor, [(MeZn)(MeCd)(tdmap)2] (6), which has been used to deposit films of CdO mixed with ZnO by LPCVD at 140 degrees C. The structure of Me4Cd4(tdmap)2Cl2 (4), obtained serendipitously, is also included. Crystal data: 1, C20H52Cd4N4O4, FW 862.26, triclinic, P1, a = 11.47560(10), b = 13.55400(10), c = 21.5966(2) A, alpha = 99.7869(4), beta = 90.7476(4), gamma = 98.7823(4) degrees, V = 3268.82(5) A(3), Z = 4; 2, C27H67Cd3N6O3, FW 861.07, triclinic, P1, a = 11.4148(2), b =13.1886(2), c = 14.3139(3) A, alpha = 102.1962(10), beta = 108.3064(10), gamma = 100.8446(10) degrees, V = 1923.09(6) A(3), Z = 4; 3, C22H54Cd2N6O2, FW 659.51, monoclinic, P2(1)/n, a = 10.2912(1), b = 13.46930(1), c = 11.79130(1) A, beta = 112.8051(1) degrees, V = 1506.59(2) A(3), Z = 2; 4, C24H60Cd4Cl2N6O2, FW 985.28, monoclinic, P2(1)/c, a = 10.89780(10), b = 20.3529(2), c = 16.5317(2) A, beta = 94.8550(10) degrees, V = 3653.61(7) A(3), Z = 4; 5, C40H96Cd2N12O4, FW 1034.09, orthorhombic, P2(1)cn, a = 12.33290(10), b = 14.25060(10), c = 29.9003(2) A, V = 5255.01(7) A(3), Z = 4.     

Searching for new host compounds: synthesis and characterization of novel crown ether-functionalized dendrimers

Novel lipophilic dendrimers as host compounds, that is, 7-15, containing crown ether moieties with different sizes as the core, surrounded by first, second or third generation poly(aromatic ether) wedges, were synthesized by the use of bis(bromomethyl)-substituted crown ethers and Fréchet-type poly(benzyl ether) dendrons as building blocks. The compounds were fully characterized.     

Novel thiophene-based cycloruthenated compounds: synthesis, characterization, and reactivity

The reactions between a series of thiophene-based imines with [(η(6)-C(6)H(6))RuCl(μ-Cl)](2), in a basic medium, and in MeCN give a family of ruthenacycles of stoichiometry [Ru(C^N)(NCMe)(4)]PF(6) (C^N = orthometalated thiopheneimine). In these species, the C-H activation process is produced in most cases at the thiophene ring. When two C-H bonds are competing (thiophene vs aryl), the cyclometalation can be driven regioselectively to the thiophene unit or to the aryl ring as a function of the location of the iminic C=N bond. Cyclometalation can also be oriented to positions 2 or 3 of the thiophene depending on the situation of the imine in the heterocycle (3 or 2, respectively). In all studied cases, the η(6)-C(6)H(6) ligand was substituted by acetonitrile. The X-ray structures of two representative complexes have been determined. These thiophene-based metallacycles react with iodine under very mild conditions affording, after hydrolysis, substituted 3-iodo-2-formyl(benzo)thiophenes or substituted 2-iodo-3-formyl(benzo)thiophenes, as a function of the organometallic precursor.     

p-Hydroquinone-metal compounds: synthesis and crystal structure of two novel VV-p-hydroquinonate and VIV-p-semiquinonate species

Reaction of the p-hydroquinone derivative H2Na4bicah.4H2O with either VIVOSO(4).3H2O and NaVVO3 in equivalent quantities or with NaVVo3 yields the tetranuclear VIVO2+ macrocycle-semiquinonate compound Na6[(VIVO)4-(mu2-O)2[mu2-bicas.(-5)-N,O,O,O]2].Na2SO(4).20H2O (1.Na2SO(4).20H2O) and the dinuclear cis-VVO2(+)-hydroquinone species Na4[(VVO2)2[mu2-bicah(-6)-N,O,O,O]].11H2O (2.11H2O) respectively. Compounds 1.Na2SO(4).20H2O and 2.11H2O were characterized by X-ray structure analysis and ab initio calculations.     

Lithium 2,3-dihydro-1-benzothiophene-1,1-dioxide: synthesis, characterization, DFT calculations, and reactivity toward aldehydes and azomethines

The sulfonyl carbanion derived from 2,3-dihydro-1-benzothiophene-1,1-dioxide and its lithium salt has been investigated by DFT calculations. NMR and IR spectroscopic analyses showed that the lithium sulfonyl carbanion exists in solution as a monomer in equilibrium with a dimer. The lithium carbanion was treated with aldehydes and azomethynes to give chiral hydroxy and amino derivatives. The stereochemistry of the products and the diastereoselectivity of the reaction were investigated.     

Metal-free and transition-metal tetraferrocenylporphyrins part 1: synthesis, characterization, electronic structure, and conformational flexibility of neutral compounds

H(2)TFcP [TFcP = 5,10,15,20-tetraferrocenyl porphyrin(2-)] was prepared by a direct tetramerization reaction between pyrrole and ferrocene carbaldehyde in the presence of a BF(3) catalyst, while the series of MTFcP (M = Zn, Ni, Co and Cu) were prepared by a metallation reaction between H(2)TFcP and respective metal acetates. All compounds were characterized by UV-vis and MCD spectroscopy, APCI MS and MS/MS methods, high-resolution ESI MS and XPS spectroscopy. Diamagnetic compounds were additionally characterized using (1)H and (13)C NMR methods, while the presence of low-spin iron(ii) centers in the neutral compounds was confirmed by M?ssbauer spectroscopy and by analysis of the XPS Fe 2p peaks, revealing equivalent Fe sites. XPS additionally showed the influence on Fe 2p binding energies exerted by the distinct central metal ions. The conformational flexibility of ferrocene substituents in H(2)TFcP and MTFcP, was confirmed using variable-temperature NMR and computational methods. Density functional theory predicts that alpha,beta,alpha,beta atropisomers with ruffled porphyrin cores represent minima on the potential energy surfaces of both H(2)TFcP and MTFcP. The degree of non-planarity is central-metal dependent and follows the trend: ZnTFcP < H(2)TFcP approximately CuTFcP < CoTFcP < NiTFcP. In all cases, a set of occupied, predominantly ferrocene-based molecular orbitals were found between the highest occupied and the lowest unoccupied, predominantly porphyrin-based molecular orbitals. The vertical excitation energies of H(2)TFcP were calculated at the TDDFT level and confirm the presence of numerous predominantly metal-to-ligand charge-transfer bands coupled via configurational interaction with expected intra-ligand pi-pi* transitions.     

Design, synthesis and cytotoxic activities of novel hybrid compounds between dihydrobenzofuran and imidazole

A series of novel hybrid compounds between dihydrobenzofuran and imidazole has been prepared and evaluated in vitro against a panel of human tumor cell lines. The results suggest that substitution of the imidazolyl-1-position with an electron-donating dihydrobenzofuran, and the imidazolyl-3-position with a naphthylacyl or electron-rich phenacyl group, were vital for modulating cytotoxic activity.     

Allyl strontium compounds: synthesis, molecular structure and properties

The synthesis and attempted isolation of neutral bis(allyl)strontium [Sr(C(3)H(5))(2)] (1) resulted in the isolation of potassium tris(allyl)strontiate K[Sr(C(3)H(5))(3)] (2). In situ generated 1 shows a pronounced Br?nsted basicity, inducing polymerisation of THF. Ate complex 2 crystallises as [K(THF)(2){Sr(C(3)H(5))(3)}(THF)](∞) (2·(THF)(3)). The salt-like solid state structure of 2·(THF)(3) comprises a two-dimensional network of (μ(2)-η(3):η(3)-C(3)H(5))(-) bridged potassium and strontium centres. Synthesis of allyl complexes 1 and 2 utilised SrI(2), [Sr(TMDS)(2)] (3) (TMDS = tetramethyldisilazanide), and [Sr(HMDS)(2)] (HMDS = hexamethyldisilazanide) as strontium precursors. The solid state structure of previously reported [Sr(TMDS)(2)] (3) was established by X-ray single crystal analysis as a dissymmetric dimer of [Sr(2)(TMDS)(4)(THF)(3)] (3·(THF)(3)) with multiple Si-HSr agostic interactions. The presence of ether ligands (THF, 18-crown-6) influenced the Si-HSr resonances in the NMR spectra of the amido complex 3.     

The synthesis,characterization, and electrochemistry of molecular cobaloxime/organocobaloxime: catalysts for cycloaddition of carbon dioxide and epoxides

The new cobaloxime (1), organocobaloxime (2), and their intramolecular hydrogen (O–H?O) bridges replaced by Cu(II)-containing multinuclear cobaloximes (3–10) were synthesized and characterized by elemental analysis, ¹H and ¹³C NMR spectra, FT-IR spectra, UV–vis spectra, LC-MS spectra, molar conductivity measurements, melting point measurements, and magnetic susceptibility measurements. Their electrochemical properties were investigated using cyclic voltammetric techniques in DMSO solution. The cobaloxime or organocobaloxime (1, 2) were used as precursors, replacing intramolecular O–H?O bridges, forming multinuclear complexes (3–10). Then, these compounds were used as homogeneous catalysts for cyclic carbonate synthesis from carbon dioxide (CO₂) and epoxides. In the catalytic experiments, dimethyl amino pyridine (DMAP) was used as co-catalyst, since DMAP was a more active base with higher yield compared to other Lewis bases. It is not necessary to use solvent according to catalytic test results, important in green chemistry.     

Biogenic synthesis of silver nanoparticles using Echium vulgare: Characterisation,quantitative analysis of bioactive compounds,antioxidant activity and catalytic degradation

Nanotechnology has a great significance owing to its large variety of applications. Silver nanoparticles (AgNPs@Ev) were produced using water extract of Echium vulgare aerial part by a simple, nontoxic, eco-friendly method. The spectroscopic study identified the structure of AgNPs@Ev. The absorption was detected as 460 nm by UV/Vis spectrophotometer. TEM analysis presented the morphology of nanostructures and particle size was calculated as 9.55 nm. XRD pattern showed the structure to be face-centered cubic unit cell. EDS analysis verified the presence of elemental silver. DLS and zeta potential analyses were executed by Zetasizer. The stability of nanostructures was revealed by the zeta potential analysis (−3.1 mV). The degradation performance of AgNPs@Ev on methylene blue was evaluated by UV/Vis spectrophotometer and 64% of methylene blue was degraded after 40 h. Quantitative analysis of natural compounds was performed by HPLC and isoquercitrin (1.32 mg/g extract), naringin (1.15 mg/g extract) were detected as major products. Antioxidant activity of extract and nanoparticles were achieved. AgNPs@Ev exhibited excellent DPPH, ABTS, and FRAP activities (IC₅₀, 6.8 μg/mL), (IC₅₀, 2.3 μg/mL), (5.3 μmol/g sample) respectively.