Synthesis and DNA binding studies of Ni(II), Co(II), Cu(II) and Zn(II) metal complexes of N1,N5-bis[pyridine-2-methylene]-thiocarbohydrazone Schiff-base ligand

The thiocarbohydrazone Schiff-base ligand with a nitrogen and sulphur donor was synthesized through condensation of pyridine-2-carbaldehyde and thiocarbohydrazide. Schiff-base ligands have the ability to conjugate with metal salts. A series of metal complexes with a general formula [MCl2(H2L)]·nH2O (MNi, Co, Cu and Zn) were synthesized by forming complexes of the N1,N5-bis[pyridine-2-methylene]-thiocarbohydrazone (H2L) Schiff-base ligand. These metal complexes and ligand were characterized by using ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FT-IR), 1H and 13C NMR spectroscopy and mass spectroscopy, physicochemical characterization, CHNS and conductivity. The biological activity of the synthesized ligand was investigated by using Escherichia coli DNA as target. The DNA interaction of the synthesized ligand and complexes on E. coli plasmid DNA was investigated in the aqueous medium by UV-Vis spectroscopy and the binding constant (Kb) was calculated. The DNA binding studies showed that the metal complexes had an improved interaction due to trans-geometrical isomers of the complexes than ligand isomers in cis-positions.     

Syntheses of dibenzo[b,e][1,4]dioxin derivatives via iron complexes, and further functionalizations via directed metallation

Double nucleophilic aromatic substitution reactions between (cyclopentadienyl)(η⁶-1,2-dichlorobenzene)iron(1 + ) salts and substituted 1,2benzenediols have been carried out under mild conditions to prepare [η⁶-dibenzo[b,e][1,4]dioxin]iron(1 + ) complexes functionalized in the 1- or 2-position with an alkyl, aldehyde, carboxylic acid, methoxycarbonyl, carboxamide, or hydroxy group. 3-Methyl- and 4-methyl-(η⁶-1,2-dichlorobenzene)iron complexes were treated with substituted 1,2-benzenediols to effect functionalization of both aromatic rings of the heterocycle. The dibenzodioxin ligands were liberated routinely by irradiation with ultraviolet light. Directed deprotonation of the free functionalized dibenzodioxins with an alkyllithium reagent followed by quenching with a variety of electrophiles yielded further derivatives, including two new isoindolone systems.     

Synthesis of new derivatives of 1,5,9,13-tetraaza[16]annulene using 2-substituted vinamidinium salts

New 7,15-dibromo-, 7,15-di(bromomethyl)-, and 7,15-di[4-(bromomethyl)phenyl]-1,5,9,13-tetraaza[16]annulene derivatives are synthesized via the condensation reaction of 2-substituted vinamidinium salts [2-substituted 3-(dimethylamino)-N,N-dimethyl-2-propen-1-aminium salts] with 1,8-diaminonaphthalene in acetonitrile/acetic acid. The ultraviolet spectral behavior of these compounds is examined in DMSO.     

Reinvestigation of the jutz synthesis of benzo [e] pyrene and benzo [a] pyrene derivatives from benzanthrene

Base-catalyzed reactions of benzanthrene with “vinamidinium salts” ($\text{2a-c}$ ) followed by thermal electrocyclic ring closure are regiospecific affording only benzo [e] pyrene derivatives, contrary to previous claims.     

Investigation of the reactions of fluorinated isatins and N-acetylisatins with thiocarbohydrazide: Synthesis of a novel spiro system: 2-oxo-1′,2′,4′,5′-tetrahydrospiro[3H-indole-3,3′-1,2,4,5-tetrazine]-6′-thione

A novel system 2-oxo-1′,2′,4′,5′-tetrahydrospiro[3H-indole-3,3′-1,2,4,5-tetrazine]-6′-thione has been synthesized by the treatment of fluorinated isatins with thiocarbohydrazide in aqueous ethanolic medium. Under exactly similar conditions, N-acetylisatin gave exclusively thiocarbohydrazone. The spiro product, on treatment with acetic acid, gave fluorinated isoindigo. Characterization of these products have been done by elemental analyses, ir, pmr and mass spectral studies.     

Efficient One-Pot Synthesis of Substituted Pyrido[2,3-d]pyrimidines from Vinamidinium and Chloropropeniminium Salts

A novel and efficient one-pot preparation of 6-substituted pyrido-[2,3-d]pyrimidines by cyclocondensation of 6-amino-1,3-dimethyluracil with symmetrical vinamidinium salts under basic conditions has been developed. Regioselectivity was observed with an unsymmetrical chloropropeniminium salt.     

Novel cyclopalladated imino-thiophenes: synthesis and reactivity toward alkynes and carbon monoxide

ortho-palladated complexes based on thiophene and benzothiophene ligands 1a and 1b have been synthesized by direct C-H activation under mild conditions. These species were fully characterized, including single-crystal X-ray diffraction analysis. The reactions of these novel complexes with internal alkynes afforded a variety of thieno[3,2-c]pyridinium salts substituted at the 6- and 7-positions. The thiophene-based complex 2a also reacts with carbon monoxide, in the presence of different alcohols, forming the corresponding esters by tandem alkoxycarbonylations. This latter reaction can be exploited for the unexpected, but straightforward, formation of the monomeric bis-cyclometallated complexes 6a and 6b from 2a or 2b, whose syntheses do not require the employment of transmetallating agents. The structures of these monomeric palladacycles were also fully elucidated by means of X-ray diffraction studies.     

Reaction of aldimine anions with vinamidinium chloride: three-component access to 3-alkylpyridines and 3-alkylpyridinium salts and access to 2-alkyl glutaconaldehyde derivatives

N-tert-Butylimino derivatives of aldehydes were deprotonated with LDA and reacted with vinamidinium chloride to give 2-alkylaminopentadienimine derivatives, which were isolated as their corresponding hydrochloride in 68-81% yield. Reaction of these derivatives with ammonium acetate or salts of primary amines, in n-butanol at 80 degrees C, afforded the corresponding 3-alkylpyridines or 3-alkylpyridinium salts in high yield. Alkaline hydrolysis of 2-alkylaminopentadieneimine derivatives allowed a practical accesss to potassium salts of 2-alkylglutaconaldehyde.     

Ring contraction of thia(seleno)diazine rings into pyrazoles in the reaction of 3-aryl-10-methyl-2H-1,3,4-thia(seleno)diazino[3, 2-a]benzimidazolium salts with bases

Reaction of 3-aryl-10-methyl-2H-1,3,4-thiadiazino[3,2-a]benzimidazolium salts with triethylamine led to ring contraction of the thiadiazine ring to a pyrazole ring with the formation of a mixture of derivatives of 3-mercaptopyrazolobenzimidazole and di(pyrazolo[1,5-a]benzimidazolyl-3) disulfide. The disulfides were formed exclusively when these salts react with ethanolic alkali. The reaction with potassium carbonate in acetic anhydridegave3-acetylthiopyrazolo[1,5- a]benzimidazoles. 2-Aryl-4- alkylpyrazolo[1, 5- a]benzimidazoles were formed by heating thiadiazino[3,2-a]benzimidazolium salts in formamide and by treating selenodiazino[3,2-a]benzimidazolium salts with potassium carbonate in acetic anhydride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1698–1705, 1992.     

Areneruthenium(II) 4-acyl-5-pyrazolonate derivatives: coordination chemistry, redox properties, and reactivity

Areneruthenium(II) molecular complexes of the formula [Ru(arene)(Q)Cl], containing diverse 4-acyl-5-pyrazolonate ligands Q with arene = cymene or benzene, have been synthesized by the interaction of HQ and [Ru(arene)Cl(micro-Cl)]2 dimers in methanol in the presence of sodium methoxide. The dinuclear compound [{Ru(cymene)Cl}2Q4Q] (H2Q4Q = bis(4-(1-phenyl-3-methyl-5-pyrazolone)dioxohexane), existing in the RRuSRu (meso form), has been prepared similarly. [Ru(cymene)(Q)Cl] reacts with sodium azide in acetone, affording [Ru(cymene)(Q)N3] derivatives, where Cl- has been replaced by N3-. The reactivity of [Ru(cymene)(Q)Cl] has also been explored toward monodentate donor ligands L (L = triphenylphosphine, 1-methylimidazole, or 1-methyl-2-mercaptoimidazole) and exo-bidentate ditopic donor ligands L-L (L-L = 4,4'-bipyridine or bis(diphenylphosphino)propane) in the presence of silver salts AgX (X = SO3CF3 or ClO4), new ionic mononuclear complexes of the formula [Ru(cymene)(Q)L]X, and ionic dinuclear complexes of the formula [{Ru(cymene)(Q)}2L-L]X2 being obtained. The solid-state structures of a number of complexes were confirmed by X-ray crystallographic studies. Their redox properties have been investigated by cyclic voltammetry and controlled potential electrolysis, which, on the basis of their measured RuII/III reversible oxidation potentials, have allowed the ordering of the bidentate acylpyrazolonate ligands according to their electron-donor character and are indicative of a small dependence of the HOMO energy upon the change of the monodentate ligand. This is accounted for by DFT calculations, which show a relevant contribution of acylpyrazolonate ligand orbitals to the HOMOs, whereas that from the monodentate ligand is minor.     

Chiral phosphine-phosphite ligands in the highly enantioselective rhodium-catalyzed asymmetric hydrogenation.

We have investigated a series of enantiopure phosphine-phosphite ligands (P(1)-P(2) = ligands 1-4) in the rhodium-catalyzed asymmetric hydrogenation reaction. Intermediate [Rh(P(1)-P(2))(cod)]BF(4) and [Rh(P(1)-P(2))(5)]BF(4) complexes (cod = 1,5-cyclooctadiene; 5 = methyl acetamidoacrylate ester) were observed by (31)P[(1)H] NMR. The [Rh(P(1)-P(2))(cod)]BF(4) complexes were precursors to active catalysts of the asymmetric hydrogenation reaction of several prochiral dehydroamino acid derivatives under mild reaction conditions (1 bar of hydrogen and 20 degrees C). The enantiomeric excess reached up to 99%.     

Lanthanum(III) chloride complexes with heterocyclic Schiff bases

Condensation of 2-amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene with carbonyl compounds such as isatin, o-hydroxyacetophenone or benzoin in 1:1 ratio in ethanol medium yielded three distinctly different heterocyclic Schiff bases viz. 2-(N-indole-2-one)amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene (ISAT), 2-(N-o-hydroxyacetophenone)amino- 3-carboxyethyl-4,5,6,7-tetrahydro-benzo[b]thiophene (HAAT) or 2-(N-benzoin)amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene (HBAT) respectively. These ligands formed well defined complexes with lanthanum(III) chloride under suitable conditions. The ligands and the complexes have been characterized on the basis of elemental analyses, molar conductance measurements, UV-visible, IR and proton NMR spectral studies. Kinetics and mechanism of the thermal decomposition of the ligands and the metal complexes have been studied using non-isothermal thermogravimetry. Kinetic parameters were calculated for each step of the decomposition reactions using Coats-Redfern equation. The rate controlling process for all the ligands and complexes is random nucleation with the formation of one nucleus on each particle (Mampel equation). Relative thermal stabilities of the ligands and the metal complexes have been compared.     

Mononuclear, dinuclear, and hexanuclear goldI complexes with (aza-15-crown-5)dithiocarbamate

The reactions of sodium (aza-15-crown-5)dithiocarbamate with [AuClL] precursors lead to mono-, di-, or hexanuclear derivatives depending on L. The homoleptic hexanuclear gold(I) cluster [Au6(S2CNC10H20O4)6] is formed by displacement of the chloride and isocyanide ligands in [AuCl(CN(2,6-Me2C6H3))]. X-ray diffraction studies show a novel geometry in gold cluster chemistry where the six gold atoms display a cyclohexane-like geometry in a chair conformation with Au-Au-Au angles of 117.028(9) degrees, two short gold-gold distances of 2.9289(5) A, and bidentate bridging dithiocarbamate ligands. The molecular structure shows a crown of gold atoms surrounded by crown ethers. This derivative luminesces at 569 nm at room temperature in the solid state. A dinuclear isomer [Au2(S2CNC10H20O4)2] had been reported previously and was obtained by reaction with [AuCl(SMe2)]. The mechanism to obtain the hexanuclear derivative involves a mononuclear intermediate [Au(S2CNC10H20O4)(CNR)] for which the X-ray structure shows a short gold-gold distance of 3.565 A with the two molecules in an anti configuration. Phosphine gold(I) mononuclear derivatives [Au(S2CNC10H20O4)(PR3)] (R = Me, Ph, both characterized by X-ray diffraction) and dinuclear diphosphine derivatives [{Au(S2CNC10H20O4)}2(mu-P-P)] (P-P = dppm, bis(diphenylphosphinomethane); dppp, 1,3-bis(diphenylphosphinopropane); and dppf, 1,1'-bis(diphenylphosphinoferrocene)) are also reported. In the mononuclear complexes, the molecular structure confirms that the dithiocarbamato ligand is mainly acting as monodentate, with a second longer Au-S distance of 3.197 (PMe3), 2.944(4) (PPh3), and 2.968 A (CNR). Three phosphine complexes are emissive at 562 (PMe3), 528 (PPh3), and 605 nm (dppm), at 77 K. X-ray diffraction studies of the dppm derivative show gold-gold intramolecular contacts of 3.0972(9) A (3.2265(10) A for a second independent molecule) and basically monodentate coordination of the dithiocarbamato ligands. All the complexes extract sodium and potassium salts from aqueous solutions. The diphosphine derivatives are noticeably better extractors than the monophosphino derivatives, mainly for potassium salts.     

Evaluation of diimine ligand exchange on Cu(I)

Four ligands have been prepared, 8,8-dimethyl-6,7,9-trihydropyrido[1,2-b]acridine and three 4,4',6,6'-tetrasubstituted derivatives of 2,2'-bipyrimidine where the substituents are methyl, phenyl, and p-tolyl. The corresponding [CuL(2)](+) salts of these ligands evidence nonequivalent NMR signals that allow an estimation of the ligand exchange barrier in both acetonitrile and chloroform solution. Lower barriers are found in the former solvent and attributed to solvent participation in the exchange process. Corresponding differences in the oxidation potentials of the complexes are explained in a similar manner. The electronic absorption properties of the complexes are also consistent with the steric and electronic properties of the ligands. [Cu(2c)(2)](PF(6)), where 2c = 4,4',6,6'-tetraphenyl-2,2'-bipyrimidine, was analyzed by X-ray diffraction and found to crystallize in the space group Pccn with a = 14.761(2) A, b = 15.007(2) A, c = 24.407(4) A, and Z = 4. The internal and external phenyl rings are disposed quite differently, with the internal rings interacting strongly with the orthogonal ligand.     

新型Schiff碱双核配合物的合成及光谱特征

首次报道了新型Schiff碱双核配合物-双[N,N"-亚烃基-2,2'(苯亚甲基)二(3,4-二甲基吡咯-5醛缩亚胺)]合双锰及双铁配合物的合成方法及光谱特征。     

Copper(I)-Fesulphos Lewis Acid catalysts for enantioselective Mannich-type reaction of N-sulfonyl imines

[reaction: see text] Copper(I) complexes of Fesulphos ligands are efficient chiral Lewis acid catalysts in the Mannich-type addition of silyl enol ethers of ketones, esters, and thioesters to N-(2-thienyl)sulfonyl aldimines. The corresponding optically active beta-amino carbonyl derivatives were obtained in good yields (58-91%) and with moderate to good enantioselectivity (61-93% ee). Removal of the N-activating group was achieved under mild conditions by simple treatment of the products with Mg in methanol.     

Iridium(III) Complexes with [−2, −1, 0] Charged Ligand Realized Deep-Red/Near-Infrared Phosphorescent Emission

A series of [−2, −1, 0] charged-ligand based iridium(III) complexes of [Ir(bph)(bpy)(acac)] ( 1 ), [Ir(bph)(2MeO-bpy)(acac)] ( 2 ), [Ir(bph)(2CF₃-bpy)(acac)] ( 3 ), [Ir(bph)(bpy)(2^tBu-acac)] ( 4 ) and [Ir(bph)(bpy)(CF₃-acac)] ( 5 ), which using biphenyl as dianionic ligand [−2], acetylacetone (or its derivatives) as monoanionic ligand [−1], and 2,2′-bipyridine (or its derivatives) as neutral ligand [0] were designed and synthesized. The chemical structures were well characterized. All of the ligands have simple chemical structures, thus further making the complexes have excellent thermal stability and are easy to sublimate and purify. Phosphorescent characteristics with short emission lifetime were demonstrated for these emitters. Notably, all of the complexes exhibit remarkable deep red/near infrared emission, which is quite different from the reported [−1, −1, −1] charged-ligand based iridium(III) complexes. The photophysical properties of these complexes are regularly improved by introducing electron-donating or -withdrawing groups into [−1] or [0] charged-ligand. The related organic light-emitting diodes exhibited deep red/near infrared emission with acceptable external quantum efficiency and low turn-on voltage (<2.6 V). This work provides a new idea for the construction of new type phosphorescent iridium(III) emitters with different valence states of [−2, −1, 0] charged ligands, thus offering new opportunities and challenges for their optoelectronic applications.     

Synthesis of paramagnetic tetranuclear rhodium and iridium complexes with the 2,6-pyridinedithiolate ligand. Redox-induced degradation to diamagnetic triiridium compounds

The tetranuclear complexes [M4(mu-PyS2)2(diolefin)4] [PyS2 = 2,6-pyridinedithiolate; M = Rh, diolefin = cod (1,5-cyclooctadiene) (1), tfbb (tetrafluorobenzo[5,6]bicyclo[2.2.2]octa-2,5,7-triene) (2); M = Ir, diolefin = cod (3), tfbb (4)] exhibit two one-electron oxidations at a platinum disk electrode in dichloromethane at potentials accessible by chemical reagents. The rhodium tetranuclear complexes were selectively oxidized to the monocationic complexes [Rh4(mu-PyS2)2(diolefin)4](+) (1(+), 2(+)) by mild one-electron oxidants such as [Cp2Fe](+) or [N(C6H4Br-4)3](+) and isolated as the PF6(-), BF4(-), and ClO4(-) salts. Silver salts behave as noninnocent one-electron oxidants for the reactions with the rhodium complexes 1 and 2 since they give sparingly soluble coordination polymers. The complex [Ir4(mu-PyS2)2(cod)4](+) (3(+)) was obtained as the tetrafluoroborate salt by reaction of 3 with 1 molar equiv of AgBF4, but the related complex 4(+) could not be isolated from the chemical oxidation of [Ir4(mu-PyS2)2(tfbb)4] (4) with AgBF4. Oxidation of 3 and 4 with 2 molar equiv of common silver salts resulted in the fragmentation of the complexes to give the diamagnetic triiridium cations [Ir3(mu-PyS2)2(diolefin)3](+). The molecular structure of [Ir3(mu-PyS2)2(cod)3]BF4, determined by X-ray diffraction methods, showed the three metal atoms within an angular arrangement. Both 2,6-pyridinedithiolate tridentate ligands bridge two metal-metal bonded d(7) centers in pseudo octahedral environments and one d(8) square-planar iridium center. An interpretation of the EPR spectra of the 63-electron mixed-valence paramagnetic tetranuclear complexes suggests that the unpaired electron is delocalized over two of the metal atoms in the complexes 1(+)-3(+).     

Dinuclear gold(I) complexes of bridging bidentate carbene ligands: synthesis, structure and spectroscopic characterisation

Eight dinuclear Au(i)-carbene complexes have been synthesized from various imidazolium-linked cyclophanes and related acyclic bis(imidazolium) salts, by treatment of the imidazolium salts with [Au(i)(SMe(2))Cl] in the presence of a carboxylate base. Single crystal structural studies showed that the Au(i)-carbene compounds contain dinuclear (AuL)(2) cations in which a pair of gold(i) centres are linked by a pair of bridging dicarbenoid ligands. Interestingly, the structural studies revealed short AuAu contacts of 3.0485(3)[Angstrom] and 3.5425(6)[Angstrom] in two of these complexes. NMR studies showed that the (AuL)(2) cations constructed from the cyclophane-based ligands retain a relatively rigid structure in solution, whilst those of the non-cyclophane ligand systems are fluxional in solution. The electronic absorption and emission spectra of the complexes in solution at room temperature were recorded and the complex with the shortest AuAu contact was found to emit intensely at 400 nm and more weakly at 780 nm upon excitation at 260 nm. The compounds with longer AuAu separations were not emissive under these conditions.     

Chiral N-phosphino sulfinamide ligands in rhodium(I)-catalyzed [2+2+2] cycloaddition reactions

The combination of cationic rhodium(I) complexes with N-phosphino tert-butylsulfinamides (PNSO) ligands is efficient for catalytic intra- and intermolecular [2+2+2] cycloaddition reactions. PNSO ligands are a new class of chiral bidentate ligands, which have the characteristic of combining the easily accessible sulfur chirality with the coordinating capacity of phosphorous. Cycloaddition of open-chained and macrocyclic E-enediynes with these chiral complexes have proved to be highly efficient in terms of yields, giving moderate enantiomeric excesses of the corresponding cyclohexadiene derivatives. In addition Rh(I)/PNSO complexes catalyzed the intermolecular cycloaddition of diynes with monoalkynes in mild reaction conditions and short reaction times.