Cobalt(II) complexes of 1,2-(diimino-4′-antipyrinyl)ethane and 4-N-(4′-antipyrylmethylidene)aminoantipyrine

Cobalt(II) complexes of the Schiff bases 1,2-(diimino-4-antipyrinyl)ethane (GA) and 4-N-(4-antipyrylmethylidene)aminoantipyrine (AA) have been prepared and characterised by elemental analysis, electrical conductance in non-aqueous solvents, i.r. and electronic spectra, as well as by magnetic susceptibility measurements. The complexes have the general formulae [Co(GA)X]X (X = ClO^– ₄ or NO₃ ^–), [Co(GA)X₂] (X = Cl^–, Br^– or I^–), [Co(AA)₂]X₂ (X = ClO₄ ^–, NO₃ ^–, Br^– or I^–) and [Co(AA)Cl₂]. GA acts as a neutral tetradentate ligand, coordinating through both carbonyl oxygens and both azomethine nitrogens. In the perchlorate and nitrate complexes of GA one anion is coordinated in a bidentate fashion, whereas in the halide complexes both anions are coordinated to the metal, generating an octahedral geometry around the Co ion. AA acts as a neutral bidentate ligand, coordinating through the carbonyl oxygen derived from the aldehydic moiety and the azomethine nitrogen. Both anions remain ionic in the perchlorate, nitrate, bromide and iodide complexes of AA, whereas both anions are coordinated to the metal ion in the chloride complex, resulting tetrahedral geometry around the Co ion.     

Preparation of (4′S) and (4′R)-Spiro(oxirane-2-4′-5α-cholestan-3′β-ol), Potent Inhibitors of 4-Methyl Sterol Oxidase

(4′R)- and (4′S)-Spiro(oxirane-2,4′-5α-cholestan-3′β-ol) (1) and (2) were made from (4′R)- and (4′S)-spiro(oxirane-2,4′-5α-cholestan-3-one) (8) and (9). Alkaline hydrogen peroxide oxidation of 4-methylene-5α-cholestan-3-one (7) gave compounds (8) and (9) as a readily separable (1:1) mixture. Reduction of (9) to (2) provided access to a compound which could not be made by other methods.     

CRYSTAL STRUCTURE AND LUMINESCENCE OF (4, 4′ -DIMETHYL-2, 2′ -BIPYRIDINE)-TRIS(BENZOATE)EUROPIUM(III)

Abstract

A mixed ligand europium complex, [Eu(BA)₃dmbpy]₂, has been prepared, where BA = benzoate and dmbpy = 4, 4′-dimethyl-2, 2′-bipyridine. The complex crystallizes in the tri-clinic system, space group P ^? ₁. Its structure has been determined using X-ray diffraction methods. The two europium ions in the molecule are held together by four carboxylate groups of benzoic acid and each europium ion is further bonded to one bidentate carboxylate group and one 4, 4′-dimethyl-2, 2′-bipyridine molecule. Excitation and luminescence spectra observed at 77 K show that the europium site in the crystal has low symmetry and changes of the chemical surroundings of the europium ion in the molecule depend mainly on the flexibility of 4, 4′-dime-thyl-2, 2′-bibyridine.     

The molecular and crystal structure of N-(4-n-butyloxybenzylidene)-4′-ethylaniline (4O.2) and N-(4-n-heptyloxybenzylidene)-4′-hexylaniline (7O.6)

Abstract

The molecular and crystal structure of N-(4-n-butyloxybenzylidene)-4′-ethylaniline (4O.2) and the homologue N-(4-n-heptyloxybenzylidene)-4′-hexylaniline (7O.6) have been solved (at room temperature) by direct methods. The crystals of both compounds belong to the triclinic system with space group P1 with two molecules per unit cell. 4O.2: a = 5·531(2), b = 7·592(3), c = 19·746(7) Å, α = 86·66(2), β = 88·15(2), γ = 90·29(2)° 7O.6: a = 5·420(2), b = 8·307(3), c = 28·057(7) Å, α = 91·69(2), β = 89·76(2), γ = 108·02(2)°. The structures were refined by full-matrix least-squares calculations to R = 0·036 for 2297 observed reflections for 4O.2 and to R = 0·037 for 2150 reflections for 7O.6. The conformations in the asymmetric units of the two compounds differ considerably: The planes of the two phenyl rings of 4O.2, forming the mesogenic core of the molecule, are twisted at 61·2° to each other and the butoxy group contains a gauche conformation. In contrast the heptoxy chain of 7O.6 forms an all trans-conformation which lies almost in one plane with the two coplanar phenyl rings. The hexyl group also exists in an extended form, in a plane which is rotated against the plane of the mesogenic unit. The packing in the crystalline state of the two homologues exhibits a layered structure along c*; in 4O.2 these layers are separated, but in 7O.6 they are interdigitated. The compensation of the dipole moments of the C?O?C and C?N?C bonds occurs similarly in both structures: molecular orientations parallel to the a, c-plane in which the long axes of the molecules points in the same direction are packed in antiparallel fashion along b*.     

Photoinduced isomerization of 4-(4′-dimethylaminostyryl) pyridine N-oxide

The effects of photoirradiation on the conformation state of 4-(4′-dimethylaminostyryl)pyridine N-oxide was studied by spectral (EAS, ¹H NMR, IR) and thermochemical methods. Trans→cis isomerization was found to proceed in 4-(4′-dimethylaminostyryl)pyridine N-oxide irradiated with light (λ ≤ 400 nm) in chloroform. The conversion of the trans form of 4-(4′-dimethylaminostyryl)pyridine N-oxide to the cis form depends on the time and intensity of irradiation. Maximum conversion was achieved when a photostationary mixture formed with a ratio of components trans:cis = 40:60. Further irradiation of the solutions of 4-(4′-dimethylaminostyryl)pyridine N-oxide in chloroform led to salification with HCl formed during the decomposition of CHCl₃.     

Synthesis and Crystal Structure of 1′-Methyl-4′- (4-chlorophenyl)-1H-indole-3-spiro-2′-pyrrolidine- 3′-spiro-4'-(2'-phenyloxazole)-2,5'(3H,4'H)-dione

The title compound (C26H20ClN3O3) has been synthesized by 1,3-dipolar cycloaddition reaction from isatin, sarcosine and (Z)-4-(4-chlorobenzylidene)-2-phenyloxazol-5(4H)-one through a one-pot procedure, and its structure was confirmed by IR, 1H NMR, elemental analysis and single-crystal X-ray diffraction analysis. The crystal belongs to the triclinic system, space group P1, with a = 9.3903(19), b = 11.398(2), c = 12.603(3) , α = 83.495(3), β = 68.988(3), γ = 67.178(3)°, V = 1160.1(4) 3, Z = 2, Mr = 457.90, Dc = 1.311 g/cm3, μ = 0.198 mm-1, F(000) = 476, the final R = 0.0489 and wR = 0.1144 for 3109 observed reflections with I > 2σ(I).     

Liquid crystalline phase transitions in hexakis(4-(4′-heptyloxy)biphenoxy)cyclotriphosphazene

Abstract

Hexakis(4-(4′-heptyloxy)biphenoxy)cyclotriphosphazene (HHCP) was synthesized from hexachlorocyclotriphosphazene and 4-heptyloxy-4′-hydroxybiphenyl. The mesogenicity of HHCP was studied by DSC, FTIR spectroscopy and polarizing microscopy. Enantiotropic smectic C and nematic phases were observed between 450 and 455 K and 455 and 456 K, respectively, on heating, and between 456 and 455 K (nematic) and 455 and 440 K (smectic C) on cooling from the isotropic liquid phase. The introduction of the heptyloxybiphenoxy groups as side chains into cyclotriphosphazene has generated the liquid crystalline phase. FTIR spectroscopy showed that the P=N and P-O-(C) stretching vibrations converted to lower frequencies from 1224 to 1210 cm^?1 and from 920 to 910cm^?1, respectively, at the crystalline (C)-S_c phase transition. This result suggests that the state of the cyclotriphosphazene ring dramatically changes near the C-S_c phase transition.     

Synthesis and Anti-HIV Activity of Trisubstituted (3′R, 4′R)-3′,4′- Di-O-(S)-camphanoyl-(+)-cis-khellactone (DCK) Analogs

In our prior studies,3′,4′-di-O-(S)-camphanoyl-(+)-cis-khellactone(DCK,1,Figure1)and its derivatives including mono-and di-substituted DCK analogs were identified as a novel class of potent anti-HIV agents1-4.Because of its high potency and efficient syn-thesis,4-methyl-DCK25was chosen as a drug candidate for preclinical studies.How-ever,the low solubility and poor oral bioavailability of4-methyl-DCK limited its further development.Because high molecular hydrophobicity might be one re…     

Molecular structure of 2,3-(4′-phenylacetyl)- and 2,3-(4′-diphenylacetyl)-benzo-15-crown-5

The conformational state of two benzo-crown ethers with substantially different physiological activity, 2,3-(4-phenylacetyl)- and 2,3-(4-diphenylacetyl)benzo-15-crown-5, was studied in crystals and solutions in CH₃CN and CCl₄ by x-ray crystallographic analysis, IR spectroscopy, and conformational calculations by the method of molecular mechanics. Transition from the crystalline state to solutions was found to be accompanied by a substantial change in the conformation of the macrocyclic ring of all the compounds studied. The nature of the substituent in the benzene ring and the polarity of the solvent have an influence on the conformational state of the macrocyclic ring of the free ligand, which, however, is not the determining factor in the change in the activity of the compounds. The COCCOC fragments of the macrocyclic framework are conformationally labile, readily passing from gauche to trans conformations and the reverse, which is promoted by the negligible energy barriers between the different conformations, determined in the work by a molecular mechanics method.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1819–1825, August, 1991.     

Bis-(4-methyl-4′-pentyl-2,2′-bipyridyl)(dicyano)iron(II): a versatile solvatochromic solvation probe

We report the preparation, characterisation, and solvatochromic behaviour of bis-(4-methyl-4-pentyl-2,2-bipyridyl)(dicyano)iron(II). This is the first compound whose solubility characteristics permit its use as a solvatochromic indicator over the complete range of solvents from water to paraffins.     

X-ray diffraction study of 1,5-bis-(4′,4′,4′-trifluoro-1′-methyl-3′-oxo-but-1′-enylamino)-3-oxapentane

Specific features of the molecular and crystal structures of 1,5-bis-(4′,4′,4′-trifluoro-1′-methyl-3′-oxo-but-1′-enylamino)-3-oxapentane are determined by single crystal XRD.     

Crystal and molecular structure of 4(3-acryloyloxy)octyloxy- and 4(3-acryloyloxy)hexyloxy-4′-cyanobiphenyls

The molecular and crystal structures of N≡C-C₆H₄-C₆H₄-O-(CH₂)₈-O-CO-CH=CH₂ (4(3-acryloyloxy)octyloxy-4′-cyanobiphenyl) (I) and N≡C-C₆H₄-C₆H₄-O-(CH₂)₆-O-CO-CH=CH₂ (4(3-acryloyloxy)hexyloxy-4′-cyanobiphenyl) (II) were determined by X-ray diffraction. The structures of I and II are stereotype. The space group of I and II is C2/c, Z = 8; lattice parameters I: a = 34.677(7)?, b = 9.452(2)?, c = 13.004(3) ?, β = 99.30(3)°; II: a = 30.858(6) ?, b = 9.504(2) ?, c = 13.082(2) ?, β = 92.78(3)°. The planar extended molecules I and II are packed in the unit cell to give clearly differentiated aliphatic and aromatic regions throughout the whole crystal. All intermolecular contacts are concentrated in the aromatic region. The molecular packing is very loose but the aromatic areas of I and II fully coincide. The only free parameter of the structure is the length of the aliphatic chain (CH₂)n (n = 8 and 6). According to DSC data, compound I possesses enantiotropic mesomorphism and II possesses monotropic mesomorphism.     

In situ synthesis and structure of FeCl4(4,4′-diethyl-4,4′-bipyh) (bipy = bipyridine)

A novel viologen(4,4′-bipyridinium)-based compound FeCl₄(4,4′-diethyl-4,4′-bipyH) (1) (bipy = bipyridine), in which 4,4′-diethyl-4,4′-bipyH (MQ ⁺) was generated in situ, is synthesized via the hydrothermal reaction and structurally characterized by single crystal X-ray diffraction. The crystal structure analysis reveals that the title compound features an isolated structure based on 4,4′-diethyl-4,4′-bipyH moieties and an iron atom terminally bound by four chlorine atoms. The 4,4′-diethyl-4,4′-bipyH moieties and (FeCl₄)^? anions are interconnected by hydrogen bonds to form a 3D supramolecular framework.     

Ionic-Liquid Salt-Mediated Synthesis of 4′-(Pyridyl)-terpyridines

One-pot reactions to produce isomeric 4′-(pyridyl) 2,2′:6′,2″-terpyridine under moderate conditions are described using imidazolium-based ionic liquid and quaternary ammonium-based molten salts as solvent media. The use of eutectic molten salts as a reaction media proved effective in sequential aldol and Michael addition reactions, leading to substituted terpyridines. The desired product was obtained in reasonable yield via a simple, one-pot reaction.     

Reentrant nematic phase in 4-alkyl-4′-cyanobiphenyl (nCB) binary mixtures

The appearance of reentrant nematic phase was identified in nCB/8CB (n = 1–6) binary mixtures using differential scanning calorimetry, small-angle X-ray diffraction and polarising microscopy with photomonitor. Phase diagrams can roughly be unified if plotted against the average number of alkyl chain length. Distinction was recognised for the phase boundaries between nematic and smectic A phases of even and odd n of the minor component nCB. The character of 8CB as ‘SmA former’ is briefly discussed.     

Stereochemistry of the asymmetric reduction of (1′s)-1,3-dimethyl-4(1′-phenylethylimino)piperidine

The stereochemistry of the asymmetric reduction of the imine obtained from 1,3-dimethylpiperidin-4-one and (S)--phenylethylamine has been studied. It is shown that hydride reduction of imine 1 by sodium borohydride in methanol is asymmetric and gives the cis and trans diastereomeric pair 1,3-dimethyl-4-(-phenyl-ethylamino) piperidine in the ratio 3:1. Using sodium in isopropanol gives only one trans diastereomeric pair.¹H NMR has been used to identify the stereochemical structure and diastereomer excess of the cis and trans isomers of 1,3-dimethyl-4-(-phenylethylamino)piperidine which had been separated by column chromatography.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 219–221, February, 1996.     

Microwave promoted one-pot synthesis of 3-(2′-amino-3′-cyano-4′-arylpyrid-6′-yl)coumarins

A facile procedure for the synthesis of 3-(2′-amino-3′-cyano-4′-arylpyrid-6′-yl)coumarins are being reported starting from 3- acetylcoumarin,aromatic aldehydes and malononitrile.The reactions were carded out on microwave irradiation in good yield with short time and easy work-up.The structures of all the compounds have been confirmed on the basis of their analytical,IR,~1H NMR, and mass spectral data.     

Photochemical and Picric Acid-Catalyzed Isomerization of 4-(4′-Dimethylaminostyryl)pyridine

Equilibrium photoisomerization of trans-DASP into cis-DASP occurs in a solution. In presence of picric and trifluoroacetic acids in acetonitrile, cis-DASP isomerizes into trans-DASPH⁺ cation. The reaction is inhibited by three molecules of PicOH. Acid-catalyzed mechanism of isomerization is confirmed by semiempirical calculation (PM3) of changes in standard heats of the separate steps.     

4，4′-联喹啉酸铅(II)配位聚合物

消旋轴手性配体(R，S)-4，4′-联二喹啉-3，3′-二甲酸乙酯(DBD) (1)与Pb(OAc)₂在吡啶催化水热140 ℃合成条件下合成一新颖的配位聚合物[Pb(BD)(pyridine)]_n (3)，荧光测量表明，该配位聚合物与有机配体一样，在390 nm附近展现紫色荧光。     

Incompatible reaction for (3-4-epoxycyclohexane) methyl-3′-4′-epoxycyclohexyl-carboxylate (EEC) by calorimetric technology and theoretical kinetic model

(3-4-Epoxycyclohexane) methyl-3′-4′-epoxycyclohexyl-carboxylate (EEC) is a typical epoxy resin (EP). In Asia, due to the unstable reactive natures of EP, various thermal hazard and runaway reaction incidents have been occasioned by EP in the manufacturing process, such as fire, explosion, and toxic release, resulting in loss of life as well financial catastrophes and social outcries. Certain catalysis substances, H₂SO₄, acetic acid, or NaOH, may accelerate the reaction or curing rate for EP. However, an incompatible reaction with these chemical substances may induce a thermal hazard, causing a runaway excursion during the last stage. We employed thermogravimetry (TG) to obtain thermal stability parameters under non-isothermal conditions to evaluate the runaway reactions for EEC. The experimental data were compared with kinetics-based curve fitting to assess thermally hazardous phenomena by optimizing curve fitting on the kinetic parameters. The aim of this study was to estimate the incompatible hazards for EEC, provide thermal hazard information in order to determine the optimum operation conditions, and diminish the likelihood of fire and explosion accidents incurred by EP.