1,9-Bis(N,N-dimethylaminomethyl)dipyrromethanes in the synthesis of porphyrins bearing one or two meso substituents

A synthesis of 5,15-disubstituted zinc-porphyrins has been developed that employs condensation of a 1,9-bis(N,N-dimethylaminomethyl)dipyrromethane+a dipyrromethane in refluxing ethanol containing zinc acetate followed by oxidation with DDQ. The N,N-dimethylaminomethylation of the dipyrromethane was achieved via Eschenmoser's reagent (N,N-dimethylmethyleneammonium iodide) in CH₂Cl₂ at room temperature. The synthesis is compatible with diverse substituents (e.g., alkyl, aryl, ester, acetal) and enables rapid synthesis of trans-AB-, A₂-, and A-porphyrins. The synthesis of >40 zinc porphyrins has been surveyed; 13 zinc porphyrins were isolated in yields of 5-20% without detectable scrambling.     

Deposition of zinc hydroxide films using weak organic bases

Chemical deposition of zinc hydroxide (obtained by deposition with N,N′-dimethylformamide from alkaline solutions) on glass substrates is studied. The morphology and structure of the films are investigated. The films are shown to consist of zinc hydroxide and zinc oxide that are formed at different steps of the deposition process.     

Reductive coupling of aromatic N,N-acetals using zinc and chlorotrimethylsilane

The reductive coupling of aromatic N,N-acetals and N,O-acetal activated by chlorotrimethylsilane proceeded smoothly in the presence of zinc to give the corresponding diamines in good yields.     

Anion-exchange separation of cadmium in organic solvent-nitric acid media

The anion-exchange separation of cadmium from zinc and aluminium in organic solvent-nitric acid mixtures was studied. The distribution coefficients of the 3 elements in various 90% organic solvcnt-10% 5 N nitric acid media were determined for Dowex I-X8 resin. A 90% ethanol-10% 5 N nitric acid medium was most satisfactory for the quantitative separation of cadmium from zinc and aluminium. The method was applied to the analysis of some copper and aluminium base alloys. Methyl glycol or acetic acid could be used instead of ethanol. Both cadmium and zinc were strongly adsorbed from a 90% propionc acid-10% 5 N nitric acid medium; separation was then effected by gradient elution.     

Reduction of indolo[2,3-b]quinoxalines

Reduction of indolo[2,3-b]quinoxalines with zinc in the presence of an anhydride gave N,N-diacyl trapped 6,11-dihydroindolo[2,3-b]quinoxalines in 43-92% yields. When the reduction with zinc was performed in TFA/TFAA, an unexpected ring opened product was isolated in 49% yield. The structure of this product could be identified as 1,2-dihydro-1-trifluoroacetyl-3-[(2-trifluoroacetylamino)phenyl]quinoxaline.     

Synthesis,thermal, spectral and biological properties of zinc(II) 4-hydroxybenzoate complexes

New zinc(II) 4-hydroxybenzoate complex compounds with general formula [Zn(4-OHbenz)₂L_n]·xH₂O, where 4-OHbenz = 4-hydroxybenzoate; L = isonicotinamide, N-methylnicotinamide, N,N-diethylnicotinamide, thiourea, urea, phenazone, theophylline, methyl-3-pyridylcarbamate; n = 2, 3; x = 0–3, 5, were synthesized and characterised by elemental analysis, thermal analysis and IR spectroscopy. The thermal behaviour of the prepared compounds was studied by TG/DTG and DTA methods in argon atmosphere. The thermal decomposition of hydrated compounds started with dehydration. During the thermal decomposition, organic ligand, carbon monoxide, carbon dioxide and phenol were evolved. The final solid product of the thermal decomposition was zinc or zinc oxide. The volatile gaseous product, solid intermediate products and the final product of thermal decomposition were identified by IR spectroscopy, mass spectrometry, qualitative chemical analyses and X-ray powder diffraction method. The antimicrobial activity of zinc(II) carboxylate compounds was tested against various strains of bacteria, yeasts and filamentous fungi (S. aureus, E. coli, C. parapsilosis, R. oryzae, A. alternata, M. gypseum). The presence of zinc in complexes led to the increase in their antimicrobial activity in comparison with free 4-hydroxybenzoic acid.     

Synthesis and Structure of Bis(Ethylenediamine-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Di-3-Propionato)Zinc Dihydrate

Bis(ethylenediamine-N,N-di-3-propionato)zinc dihydrate [Zn(EDDP)]₂ ? 2H₂O is prepared from dichloro(ethylenediamine-N,N-di-3-propionato)zinc in the presence of silver(I) oxide. The prepared complex is studied by X-ray diffraction and spectroscopic methods. A molecule of the complex has a centrosymmetric dimeric structure. Zn atoms have trigonal-bipyramidal coordination formed by the nitrogen atoms of primary and tertiary amino groups, two oxygen atoms of propionic groups of one EDDP molecule, and one oxygen atom of the other.     

Coordination steric effect of N,N-dimethylformamide, N,N-dimethylacetamide and N-methyl-2-pyrrolidone on the assembly of coordination polymers

Three coordination polymers 1, 2 and 3 have been synthesized in DMF (N,N-dimethylformamide), DMA (N,N-dimethylacetamide) and NMP (N-methyl-2-pyrrolidone), respectively. In 1, DMF solvent molecule coordinates to zinc ion as an ancillary ligand, and 1D chain structure is obtained. 2 and 3 are isostructural, in which solvent molecules, DMA and NMP, do not coordinate to zinc ions, and 1D double stranded chain structures are formed. The coordination steric hindrance of the solvents is suggested as the decisive factor of the assemblies. Crystallography and thermoanalysis reveal that 2 and 3 are more stable and also include more guest solvent molecules than 1.     

Zinc mediated reductive dimerization and cyclization of α,β-unsaturated ketones in the presence of a catalytic amount of mercury(II) chloride

The zinc mediated reductive dimerization and cyclization of α,β-unsaturated ketones gives functionalized cyclopentanols in good yield in the presence of a catalytic amount of mercury(II) chloride in N,N-dimethylformamide as solvent at room temperature. The reaction is regio- and stereo-selective producing 3,4-trans-diarylcyclopentanols selectively.     

Ladders,rings and cubes as structural motifs in three new zinc(II) azide complexes: Synthesis,spectral and structural characterization

Three new zinc(II) azide complexes, namely {[Zn₂(N₃)₄(py-tetrazole)₂](py-tetrazole)}_n (1), {[Zn₂(N₃)₄(3-OHpy)] · 2H₂O}_n (2) and [Zn(N₃)₂(pym)]_n (3), where py-tetrazole = tetrazolo[1,5-a]pyridine, 3-OHpy = 3-hydroxypyridine and pym = pyrimidine, have been synthesized by the hydrothermal methods and structurally characterized. The ligand py-tetrazole was obtained through the interaction of 2-chloropyridine with the azide ion under hydrothermal condition. The structure of 1 consists of a ladder-like arrangement of 1D double chain zinc(II) azide. In the coordination chain, each zinc atom binds di-EO azide bridges connecting another zinc atom in opposite chain, and two EO bridges, one on each side, and the fifth position is occupied by a N atom of py-tetrazole ligand. The structure of 2 features 2D sheets composed of tetranuclear zinc(II) ring and octanuclear zinc(II) ring interconnected by EO azide bridges. The 2D carrying into 3D supramolecular network by the help of several hydrogen bonding interactions. The 3-OHpy molecule acts in the tautomeric keto-form as O,O-bidentate bridging ligand. Complex 3 features distorted octahedral geometry around each zinc center, N,N′-bidentate pyrimidine ligand and EE azido bridges leading to 3D network structure. The IR spectra are measured and discussed. Complex 2 only exhibits photoluminescence properties whereas the other two complexes do not luminesce at room temperature.     

Synthesis, characterization and X-ray structural determination of a stable dication derived from symmetrical ortho-aminophenyl diamine and 2-pyridinecarboxaldehyde

N,N′-Bis(2-aminophenyl)-1,2-ethanediamine is synthesized from 1,2-diaminoethane and 1-chloro-2-nitrobenzene in the presence of sodium carbonate and the product reduced by zinc dust and ammonium chloride. A novel stable dication is synthesized by reaction of N,N′-bis(2-aminophenyl)-1,2-ethanediamine and 2-pyridinecarboxaldehyde in the presence of manganese chloride in methanol. The X-ray structural analysis shows formation of the dication.     

Supramolecular triads bearing porphyrin and fullerene via ‘two-point’ binding involving coordination and hydrogen bonding

Supramolecular triads composed of fullerene (C₆₀) as primary electron acceptor, zinc porphyrin (ZnP) as primary electron donor, and either a ferrocene (Fc), or N,N-dimethylaminophenyl (DMA), or N,N-diphenylaminophenyl (DPA) entity as a second electron donor were constructed via a ‘two-point’ binding motif involving axial coordination and hydrogen bonding. The B3LYP/3-21G(*) optimized structures revealed disposition of the three entities of the triads in a triangular fashion. The redox behavior of the different components was studied using cyclic voltammetry in o-dichlorobenzene containing 0.1 M (n-C₄H₉)₄NClO₄. The oxidation potentials of the second electron donor followed the trend: Fc<DMA<DPA, and the free-energy calculations suggested the possibility of the occurrence of sequential hole transfer in these triads. Efficient electron transfer from the excited singlet state of zinc porphyrin to the fullerene entity was observed in all of the studied triads in o-dichlorobenzene. Longer charge-separated states were observed for zinc porphyrin with a carboxylic acid compared with that having an amide group. The ratios of the experimentally determined forward to reverse electron transfer rates, k_CS/k_CR were evaluated to be 10³ for triads formed by zinc porphyrin with a carboxylic acid, suggesting charge stabilization in these triads.     

An efficient synthesis of furyl sulfonamides from the reaction of furan with in situ generated N-tosyl imines

Treatment of an aldehyde and furan with N-sulfinyl-p-toluenesulfonamide/zinc chloride leads to the formation of furyl sulfonamides via an in situ generated N-tosyl imine intermediate. In one case, a novel 4-tosylamino-5,6-dihydro-4H-3-oxa-benz[e]azulene was obtained by intramolecular aromatic substitution of the activated imine at the 3-position of the furan ring.     

Tandem enantioselective conjugate addition-Mannich reactions: efficient multicomponent assembly of dialkylzincs, cyclic enones and chiral N-sulfinimines

A convenient access to enantiopure β-amino ketones through a multicomponent reaction of dialkyl zinc reagents, cyclic enones and chiral N-tert-butanesulfinimines is disclosed. Four diastereoisomers can be selectively obtained by the appropriate choice of the chiral ligand (L or ent-L) and the chiral N-sulfinimine (R_S or S_S). The protocol is particularly efficient when enolisable N-sulfinimines are used.     

Zinc chloride catalyzed three-component Ugi reaction: synthesis of N-cyclohexyl-2-(2-hydroxyphenylamino)acetamide derivatives

The ability of zinc chloride as a catalyst to promote the three-component Ugi reaction of 2-aminophenols, aliphatic or aromatic aldehydes, and cyclohexyl isocyanide in methanol at room temperature is described. The N-cyclohexyl-2-(2-hydroxyphenylamino) amide products are obtained in high yields. When N,N-dimethylformamide dimethyl acetal and triethyl orthoformate, as two new components of the three-component Ugi reaction are used instead of the aldehyde the reaction gives N-cyclohexyl-2-(dimethylamino)-2-(2-hydroxyphenylamino)acetamide and N-cyclohexyl-2-(2-hydroxyphenylamino)-2-ethoxyacetamide derivatives, respectively.     

Antibacterial and antifungal activity of metal(II) complexes of acylhydrazones of 3-isatin and 3-(N-methyl)isatin

Cobalt(II), nickel(II), copper(II) and zinc(II) complexes of 2-thiophenecarbonyl hydrazone of 3-isatin (H₂L¹) and 2-furoic hydrazones of 3-isatin (H₂L²) and 3-(N-methyl)isatin (HL³), with general composition [M(L)₂] · nX, where X is ethanol or/and water, were synthesised and characterised. The molecular structure of HL³ showed that it crystallised in the keto form, which is also the more abundant tautomer for the three hydrazone ligands in solution. The three ligands behave as κ²-O,N donors in the cobalt(II) and zinc(II) complexes. The X-ray crystal structure of pseudotetrahedral [Zn(HL¹)₂] · 1.75MeOH confirmed the O,N coordination mode of the two monodeprotonated ligands in their keto forms. Secondary interactions of zinc ions with the O atoms of each isatin keto residue provoke a substantial distortion towards a square pyramidal form. The interaction of the isatin keto residues is stronger in the three nickel(II) complexes where the three acylhydrazones can be considered as κ³-O,N,O donors.     

Nucleophilicity of heteroaromatic N-oxides in coordination with Zn(II) tetraphenylporphyrinate and in the substitution reactions

Linear correlations have been revealed between thermodynamic and kinetic parameters of the nucleophilic substitution and coordination reactions of zinc(II) tetraphenylporphyrinate with heteroaromatic Noxides in different solvents. Complex formation of zinc(II) tetraphenylporphyrinate with n-donor ligands in chloroform can serve as model system in spectroscopy studies of nucleophilicity and basicity of the compounds capable of the n,ν type complexes formation.     

Novel peripherally functionalized seco-porphyrazines: synthesis, characterization and spectroscopic evaluation

Co-macrocyclizations of 2,3-dipropylmaleonitrile and 2,3-di-(4-(methoxycarbonyl)phenyl)maleonitrile, respectively, with N,N′-dibenzyl-N,N′-di-(11-tetrahydropyranyloxy-3,6,9-trioxo-undecyl))maleonitrile and N,N,N′,N′-tetramethylmaleonitrile were used to prepare derivatives of the 4,5-diamino-porphyrazine systems including the zinc(II) complexes. Subsequent oxidation of the macrocycles with potassium permanganate gave the corresponding seco-porphyrazines. These were shown to be efficient sensitizers for the production of singlet oxygen (Φ_Δ=0.15-0.57) by the determination of their photophysical properties.     

N-(2-Alkoxyphenyl)-substituted double rhodanine indoline dyes for zinc oxide dye-sensitized solar cell

The effect of N-(2-alkoxyphenyl) group in double rhodanine indoline dye on the performance of zinc oxide dye-sensitized solar cell was examined. Both J_sc and V_oc were improved by introducing long alkoxy group due to prevention of H-aggregates formation and inhibition of electron recombination from zinc oxide surface to electrolyte.     

Synthesis and crystal structures of dinuclear zinc complexes with the 1,3-bis(2-pyridylmethyl)acetamidinato ligand

The reaction of an equimolar mixture of N,N′-bis(2-pyridylmethyl)acetamidine (1) and di(tert-butyl)phosphane with dimethylzinc yields dinuclear bis(methylzinc) bis(2-pyridylmethyl)acetamidinate di(tert-butyl)phosphanide (2). A similar protocol allows the preparation of bis(alkylzinc) bis(2-pyridylmethyl)acetamidinate tert-butylamide [zinc-bound methyl (3) or trimethylsilylmethyl group (4)]. The reactions of 3 and 4 with diphenylsilane lead to the formation of insoluble dimeric bis(alkylzinc) N,N′-bis(2-pyridylmethyl)acetamidinate hydrides [zinc-bound methyl (5) or trimethylsilylmethyl group (6)]. These zinc hydrides decompose once dissolved under formation of elemental zinc thus hampering catalytic applications. Molecular structures of [(1)ZnCl₂] as well as of the zinc complexes 2 to 6 are discussed.