Synthesis of bent [4]phenylene (cyclobuta[1,2-a:3,4-b']bisbiphenylene) and structure of a bis(trimethylsilyl) derivative: the last [4]phenylene isomer

The syntheses of the title compounds were accomplished by cobalt-catalyzed alkyne cyclotrimerizations using two strategies; the properties of the bent phenylene frame reflect the combined effects of benzocyclobutadienofusion of the component [3]phenylene substructures.     

Synthesis and thermal reaction of 2-[4-(4-ethynylphenoxy)phenylene]-3-phenylquinoxaline

2-[4-(4-Ethynylphenoxy)phenylene]-3-phenylquinoxaline was prepared by two routes and was thermally reacted at various temperatures. The intermediate reactants, the acetylene containing phenylquinoxaline, and its thermally induced reaction product were characterized by high pressure liquid chromatography and mass spectroscopy. The principal component in the 350° reaction product was a dimer from addition of an acetylene group to another.     

Hydrotris(3-mesitylpyrazolyl)borato-copper(I) alkyne complexes: synthesis, structural characterization and rationalization of their activities as alkyne cyclopropenation catalysts

The use of the bulky hydrotris(3-mesitylpyrazolyl)borate anionic ligand has allowed the synthesis of stable Tp(Ms)Cu(alkyne) complexes (alkyne = 1-hexyne, 1, phenylacetylene, 2, and ethyl propiolate, 3). The spectroscopic and structural features of these compounds and their relative reactivity have been examined, indicating the existence of a low π back-bonding from the copper(I) centre to the alkyne. Ligand exchange experiments have shown that terminal alkyne adducts are more stable than internal alkyne analogues. In good accordance with this, the previously reported alkyne cyclopropenation reaction catalysed by the Tp(x)Cu complexes can be rationalized and correlated with their relative stability.     

Isothiocyanato-calix[4]phyrin-(1,1,1,1): a useful intermediate for the synthesis of derivatised anion sensors

A calix[4]phyrin-(1,1,1,1) substituted with a 4-isothiocyanatophenyl group has been synthesised and used to attach the macrocycle to a solid support. The NCS group can also be used to further functionalise the calix[4]phyrin-(1,1,1,1) by reaction with amines and amino acids. Stability constants for anion binding by the calix[4]phyrin-(1,1,1,1) are reported and these show a clear ability to differentiate F(-) and HSO(4)(-) from Cl(-), Br(-), I(-) which can be detected by both NMR and UV-visible spectroscopy.     

A photochemical synthesis of 11H-benzo[a]carbazole

11H-Benzo[a]carbazole was prepared from 5-acetamido-1,2,3,4-tetrahydronaphthalene in four steps. A Goldberg arylation followed by hydrolysis afforded N-phenyl-1,2,3,4-tetrahydro-5-naphthylarnine ( 3 ). Photolysis of 3 produced 1,2,3,4-tetrahydro-11H-benzo[a]carbazole ( 4 ) which was converted to 11H-benzo[a]-carbazole by dehydrogenation with chloranil.     

Characterization of [Ni(py)4]Cl2 and its thermal decomposition

The stepwise thermal decomposition of [Ni(py)₄]Cl₂ was studied by means of a derivatograph. The stepwise mode of thermal decomposition allowed the preparation of new complexes. X-ray powder diffraction and IR methods were used to study the structures of the decomposition intermediates. [Ni(py)₄]Cl₂ was applied as a model substance. The decompositions of a great number of complex compounds of similar type have been reported, but only a few of them have been investigated structurally by single-crystal X-ray diffraction techniques due to the difficulty of obtaining large single-crystals.

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Zusammenfassung Die schrittweise thermische Zersetzung von [Ni(py)₄]Cl₂ wurde mit einem Derivatographen untersucht. Diese Methode ermöglicht die Darstellung neuer Komplexverbindungen. Zur Untersuchung der Struktur der intermediären Zersetzungsprodukte wurden ebenfalls XPD und IR-Spektroskopie angewandt. [Ni(py)₄]Cl₂ wurde als Modellsubstanz gewählt. Eine große Zahl ähnlicher Komplexverbindungen ist bekannt, aber nur von wenigen wurde die Kristallstruktur wegen der Schwierigkeiten, entsprechend große Einkristalle zu erhalten, durch Einkristall-Röntgendiffraktometrie bestimmt.

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[Ni(py)₄]Cl₄) . . , .

     

Characterization of [Ni(Py)4]Br2 and its thermal decomposition

The stepwise thermal decomposition of [Ni(Py)₄]Br₂ was studied by means of a derivatograph. By the introduction of a larger halide atom than Cl the degradation mechanism became simpler. The solid intermediates and the starting material was also analysed with X-ray powder diffraction methods and the unit-cell dimensions were calculated.

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Zusammenfassung Mittels eines Derivatographen wurde die stufenweise thermische Zersetzung von [Ni(Py)₄]Br₂ untersucht. Mit Einbringung eines größeren Halogenidatomes als Cl gestaltet sich der Abbaumechanismus einfacherer. Feste Zwischenprodukte und Ausgangsmaterialien wurden ebenfalls mittels Röntgenpulverdiffraktionsmethoden untersucht und die Gitterzellenkonstanten berechnet.

     

Diphenylmethylidenecyclobuta[a]cyclopropa[d]benzene: synthesis and spectral characterization

[reaction: see text] The first derivative of the novel and highly strained rocketene (cyclobuta[a]cyclopropa[d]benzene) 5, namely, the C4 diphenyl-substituted exocyclic alkene 8, has been prepared in 16% overall yield as a yellow oil with properties fully consistent with its highly strained nature.     

Enhanced fluorescence quenching in receptor-containing conjugated polymers: a calix[4]arene-containing poly(phenylene ethynylene)

A fluorescent poly(phenylene ethynylene) containing calix[4]arene-based receptor units has a sensitivity to quenching by the N-methylquinolinium ion that is over three times larger than that seen in a control polymer lacking calix[4]arenes.     

Nanoparticles of a new mercury(II) coordination polymer: synthesis,characterization, thermal and structural studies

Nanoparticles of a new Hg(II) one-dimensional coordination polymer, {[Hg(4-bpdb)I₂] _n , 4-bpdb?=?1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene} were synthesized by reaction of HgI₂ and 4-bpdb by a sonochemical method. The new nanoparticles were characterized by scanning electron microscopy, X-ray powder diffraction (XRD) and FT-IR spectroscopy; [Hg(4-bpdb)I₂] _n was structurally characterized by single crystal X-ray diffraction. This compound consists of one-dimensional polymeric units of [Hg(4-bpdb)I₂]. The thermal stability of [Hg(4-bpdb)I₂] _n was studied by thermal gravimetric (TG) and differential thermal analyses (DTA).     

K2[Te4O8(OH)10]: synthesis,crystal structure and thermal behavior

Dipotassium octaoxodecahydroxotetratellurate, K₂[Te₄O₈(OH)₁₀], has been prepared hydrothermally in acidic medium under autogenous pressure. It crystallizes in space group P2₁/c of the monoclinic system with Z=2 in a cell of dimensions a=5.592(1) Å, b=8.283(2) Å, c=16.255(3) Å, and β=99.62(3)°. The outstanding feature of the structure is a tetrameric [Te₄O₈(OH)₁₀]^2– anion built up from edge and corner sharing TeO₆ octahedra. These anions and K⁺ cations are held together by electrostatic interactions and by hydrogen bonds. The compound decomposes in two steps at 350 and 420 °C, corresponding to a water and an oxygen loss, respectively, and affording the mixed valence oxide K₂Te^VI₃Te^IVO₁₂.     

Preparation and photochemical properties of poly[2-(4-benzoylphenyl)-2-(4-propenoylphenyl)-propane] and its copolymer with styrene

2-(4-Benzoylphenyl)-2-phenyl propane ( 4 ) was prepared by benzoylation of 2,2-diphenylpropane ( 2 ). Acylation of ( 4 ) with 3-chloropropanoic chloride gave 2-(4-benzoylphenyl)-2-(4-propenoylphenyl)propane ( 5 ). A monomer 2-(4-benzoylphenyl)-2-(4-propenoylphenyl)propane ( 6 ) was prepared through dehydrochlorination of ( 5 ). The homopolymer of 6 (P6) and the copolymer with styrene ( P6 / S) were prepared by radical polymerization. Laser flash photolysis was employed to determine the absorption and emission spectra of transients, their lifetimes (τ) and the rate constant (k_q) of triplet quenching in benzene at laboratory temperature for 4 , P6 , and P6 / S. P6 exhibits a transient absorption maximum in a different spectral region than do the model 4 and copolymer P6/S . The products of k_q and τ determined by laser flash photolysis for these transients are higher than th Stern–Volmer constants based on inhibition of degradation. Degradation leading to formation of quenchers is the likely cause of this difference although crosslinking may also contribute. Irradiation of polymers ( P6 and P6/S ) at 366 nm leads to main chain scission with aquantum yield of 0.13 under N₂ for P6 and 0.03 for P6/S . In this bichromophoric structural unit, the benzophenone residue absorbs about 80–90% of the incident energy. Its triplet energy is about 5 kJ mol^?1 lower than that of the 1-(4-alkylphenyl)-2-propene-1-one chromophore. Different possible pathways of degradation are discussed namely the Norrish Type II reaction of the alkyl aryl ketone and direct reaction of triplet benzophenone with the main chain. In the mechanism favored the benzophenone triplet is proposed to be in equilibrium with the upper acetophenone-like chromophore from which the Norrish Type II reaction leading to chain fragmentation takes place.     

Polymeric organosilicon systems. XVII. Synthesis and photochemical and conducting properties of poly[o-and m-(disilanylene)phenylene]s

Poly[o-(tetramethyldisilanylene)phenylene] ( 2a ), poly[o-(1,2-dimethyldiphenyldisilanylene)-phenylene] ( 2b ), poly[m-(tetramethyldisilanylene)phenylene] ( 2c ), and poly[m-(1,2-dimethyldiphenyldisilanylene)phenylene] ( 2d ) were prepared by the sodium condensation reaction of the corresponding 1,2-and 1,3-bis (chlorosilyl)benzenes in toluene. Irradiation of thin films of 2a-2d in air resulted in a rapid decrease of absorption maxima in the ultraviolet region. The photolysis of 2b and 2d in benzene afforded photodegradation products with low molecular weights. When thin films of 2b and 2d were doped with antimony pentafluoride vapor, films which have conductivities of semi-conductor level were obtained. © 1993 John Wiley & Sons, Inc.     

Nanoparticles of a new zinc(II) coordination polymer: synthesis,characterization, thermal,and structural studies

Nanoparticles of a Zn(II) coordination polymer {[Zn(DADMBTZ)(CH₃COO)₂] _n , DADMBTZ?=?2,2′-diamino-5,5′-dimethyl-4,4′-bithiazole} were synthesized by reaction of Zn(NO₃)₂?·?4H₂O, CH₃COONH₄ and DADMBTZ by a sonochemical method. The nanoparticles were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. [Zn(DADMBTZ)(CH₃COO)₂] _n was structurally characterized by single-crystal X-ray diffraction. In this four-coordinate compound with nearly C₂ symmetry, DADMBTZ is bidentate. The metal lies in a pseudo-tetrahedral environment and is ligated by the two bithiazole ring nitrogen atoms and an oxygen from each of the two monodentate acetates; 2-D networks are formed via N–H···O hydrogen bonds. Thermal stability of [Zn(DADMBTZ)(CH₃COO)₂] _n was studied by thermal gravimetric and differential thermal analyses. A ZnO nanostructure was obtained by direct thermolyses at 500°C under air. The ZnO nanostructure was characterized by SEM, XRD, and FT-IR spectroscopy.