One-step synthesis and photochromic properties of a stable triangle terthiophene

A new photochromic compound based on the hexatriene backbone was prepared by one-step coupling. The photochromic backbone, composed of three thiophene ring, undergoes reversible ring-opening and ring-closing photoisomerization reactions when irradiated with ultraviolet and visible light, respectively. It exhibited fatigue resistance and thermally irreversible photochromic properties. The ring-open form exhibits appreciable fluorescence, while quenched by the ring-closed form.     

Aryl-substituted dithiafulvenes: synthesis,electronic properties,and redox reactivity

A series of aryl-substituted dithiafulvenes (DTFs) has been synthesized and characterized by single crystal X-ray diffraction analysis, UV–Vis absorption spectroscopy, and cyclic voltammetry. The studies indicate that the aryl-substituents not only affect the structures and electronic properties of the DTF derivatives, but also impose significant impact on their stability and reactivity when oxidized into radical cations.     

One-pot three-component synthesis, structure and redox properties of ferrocenyl isoxazoles

A consecutive coupling-cycloaddition sequence of acid chlorides, terminal alkynes, and in situ generated nitrile oxides furnishes ferrocenyl substituted redox active isoxazoles in moderate to good yields. The structure was unambiguously assigned by X-ray structure analyses and the electronic structure was elucidated by computational methods. Redox potentials of all representatives are strongly effected by the electronic nature of the bridging isoxazoloyl moiety.     

Design, synthesis and redox properties of two ferrocene-containing iron chelators

Two ferrocene-containing iron(III) chelators were synthesized from desferrioxamine B and kojic acid and their electronic absorption and electrochemical properties were studied in acetonitrile in the absence and presence of ferric ions. The results show a complex behavior arising from the occurrence of competing redox and complexation processes. Such systems are a first step toward the generation of chemosensors for the electrochemical detection of iron(III) in a solution.     

Catalytic properties of metal-containing oxidized coal catalysts in some redox reactions

An increased activity in some redox reactions was observed for some metal ions bound by ion-exchange to oxidized coals. The similarity of the catalytic properties of oxidized coals modified by Fe(III), Cu(II), Mn(II) and other cations has been established for various redox reactions: decomposition of H₂O₂, oxidation of some organic and inorganic substances by hydrogen peroxide and oxygen. The catalytic activity of the modified coals depends on how the modifying additive is bonded to the surface and the amount of the dopant. New methods for the practical use of catalysts with regulated activity are noted. Translated from Teoreticheskiya i éksperimental’naya Khimiya, Vol. 33, No. 4, pp. 256–260, 1997.     

Core-tetrasubstituted naphthalene diimides: synthesis, optical properties, and redox characteristics

2,3,6,7-tetrabromonaphthalene dianhydride has been synthesized by the bromination of naphthalene dianhydride with dibromoisocyanuric acid in excellent yield. The condensation of this dianhydride with 2,6-diisopropylaniline yielded the corresponding tetrabromo-substituted naphthalene diimide (NDI), which is a versatile precursor for the synthesis of core-tetrafunctionalized NDIs. Nucleophilic substitution of tetrabromo NDI with alkoxy, alkylthio, and alkylamino nucleophiles afforded a series of core-tetrasubstituted NDI chromophores that complete the series of previously reported di- and trifunctionalized NDI derivatives. The effects of electronic nature and number of core substituents on the optical and electrochemical properties of NDIs have been investigated by UV-vis and fluorescence spectroscopy and cyclic voltammetry. The absorption maxima (629-642 nm) of tetraamino NDIs are strongly bathochromically shifted compared to those of other core-functionalized NDIs.     

Design, synthesis and redox properties of a fluorene platform linking two different Bodipy dyes

Several new fluorophores have been prepared by grafting boradiazaindacene (red absorbing) and/or styrylboradiazaindacene (blue absorbing) units as terminal energy acceptors onto a fluorene-derived platform. In one case, an amino-bis(bipyridine) pocket has been attached to enable strong binding of transition metal ions. The stepwise syntheses were largely based on Pd-catalysed cross-coupling reactions. The electrochemistry of the dyes has been analysed by reference to the properties of the various synthetic intermediates, protonation of the tertiary amine site present in the bis(bipyridine) species enabling processes involving this centre to be distinguished from those associated with the boradiazaindacene (Bodipy) unit.     

One-step synthesis of PANI/Mn3O4 nanocomposites and evaluation of their electrochemical properties

In this paper, we have developed a simple, facile, and efficient approach to synthesize polyaniline/Mn₃O₄ (PANI/Mn₃O₄) nanocomposites using aniline as a reducer in the presence of KMnO₄ without any additives or templates. The morphology of the composites is characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results demonstrate that the tetrahedral Mn₃O₄ nanoparticles have uniform sizes and are finely dispersed in the PANI matrix. The crystallinity and chemical constituents of the composites are characterized by powder X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR) and UV-vis spectrophotometry. Moreover, cyclic voltammetry (CV) measurements are used to characterize the electrochemical properties of PANI/Mn₃O₄ nanocomposites. The developed materials give a pair of redox peaks and have better operation stability, which indicates that the composites show distinct electrochemical performance. So the PANI/Mn₃O₄ nanocomposites would have potential applications in bioanalysis, biodetection and so on.     

Electron-rich tetrathiafulvalene-triarylamine conjugates: synthesis and redox properties

By combining tetrathiafulvalenes (TTFs) and triarylamines, four TTF-triarylamine conjugates bridged by an annulated pyrrole ring were designed and synthesized by an N-arylation reaction. Electrochemical and photophysical investigations suggest that these novel conjugates possess very strong electron-donating ability with very high HOMO energy levels of around -4.70 eV; the HOMOs are mainly located on the TTF moiety. We observed significant electronic coupling between the TTF moieties and the triarylamine groups. However, no evidence for such electronic communication between end-capping TTF units (conjugates 5 and 7) or between two terminal triarylamine groups (conjugate 9) could be found. Differential scanning calorimetry (DSC) measurements together with PM3-optimized geometries suggest that conjugates 5 and 7, which adopt three-dimensional propeller-shaped structures, may easily pack and crystallize in the solid state because of the large rigid planar blades consisting of TTF and one of the phenyl rings of the triarylamine moiety. However, conjugate 9, with two bulky end-capping triarylamine groups, forms an amorphous material with a glass transition at 74.5 degrees C.     

One-step stereoselective synthesis and NMR chiral shift properties of a novel hexacoordinated phosphorus cation

[reaction: see text] Tropolone, binol, and PCl(5) react in CH(2)Cl(2) at reflux to generate in one step a novel C(2)-symmetric hexacoordinated phosphorus cation of configuration controlled by the binol ligand. It behaves as an efficient NMR chiral shift agent for chiral anionic phosphate and borate anions.     

Star-shaped pyrrole-fused tetrathiafulvalene oligomers: synthesis and redox, self-assembling, and conductive properties

A series of star-shaped pyrrole-fused tetrathiafulvalene (TTF) oligomers 1-3 was synthesized via an S(N)Ar reaction of fluorinated benzenes with the pyrrolyl sodium salts. Electrochemical and chemical oxidations of 1-3 revealed that a radical cation moiety on each TTF unit was successfully accumulated in all oligomers. Self-assembled structures of neutral and oxidized species were characterized by SEM and XRD, and their conductive properties of the iodine-doped 1-3 as well as an intermolecular mixed-valence ion radical salt were investigated.     

Macroreticular redox polymers. II. Further synthesis and properties of some redox polymers

A series of redox polymers was prepared by the addition of different redox groups to preformed, chloromethylated macroreticular styrene–divinylbenzene copolymers. These polymers contained the hydroquinone, hydroquinonesulfonic acid, methylhydroquinone, 2,5-dimethylhydroquinone, 2,5-dimethylhydroquinonesulfonic acid, 2,3,5-trimethylhydroquinone, tert-butylhydroquinone, chlorohydroquinone, benzyl mercaptan, anthraquinone, and the pyrogallol redox groups. Thus, a set of redox polymers is available having redox potentials that may range from approximately 150 to 700 mv.     

One-step synthesis of a new heterocyclophane family

New macrocyclic compounds having two benzoxazine subunits joined by two ethylene bridges have been prepared by Mannich condensation of the appropriate 4-hydroxyphenylethylamine with an excess of formaldehyde. This is a general method for synthesising a new family of heterocyclophanes.     

Coordination asymmetry in divanadium(V) compounds containing a V2O3 core: synthesis, characterization, and redox properties

A general protocol for the synthesis of micro-oxo divanadium(V) compounds [LOV(micro-O)VO(Salen)] (1-5) incorporating coordination asymmetry has been developed for the first time. One of the vanadium centers in these compounds has an octahedral environment, completed by tetradentate Salen ligand, while the remaining center has square pyramidal geometry, made up of tridentate biprotic Schiff-base ligands (L2-) with ONO (1-3) and ONS (4, 5) type donor combinations. Single crystal X-ray diffraction analysis, ESI-MS, and NMR (both 1H and 51V) spectroscopy have been used extensively to establish their identities. The V(1)-O(6)-V(2) bridge angle in these compounds, save 3, lie in a narrow range (166.20(9)-157.79(16) degrees) with the V2O3 core having a rare type of twist-angular structure, somewhat intermediate between the regular anti-linear and the syn-angular modes. For 3, however, the bridge angle is sufficiently smaller 117.92(8) degrees that it forces the V2O3 core to adopt an anti-angular geometry. The V(1)...V(2) separations in these molecules (3.7921(7)-3.3084(6) A) are by far the largest compared to their peers containing a V2O3 core. The molecules retain the binuclear structures also in solution as confirmed by NMR spectroscopy. Their redox behaviors appear quite interesting, each undergoing a one-electron reduction in the positive potential range (E1/2, 0.42-0.45 V vs Ag/AgCl) to generate a trapped-valence mixed-oxidation products [LVVO-(micro-O)-OVIV(salen)]1-, confirmed by combined coulometry-EPR experiments. The bent V-O-V bridge in these molecules probably prevents the symmetry-constrained vanadium d xy orbitals, containing the unpaired electron, to overlap effectively via the ppi orbitals of the bridging oxygen atom, thus accounting for the trapped-valence situation in this case.     

A kinetically stabilized ferrocenyl diphosphene: synthesis, structure, properties, and redox behavior

A new, stable ferrocenyl diphosphene [Tbt-P==P-Fc] (1) (Tbt=2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Fc = ferrocenyl) was synthesized by the dehydrochlorination reaction of the corresponding diphosphane, [Tbt-P(H)-P(Cl)-Fc] (8), with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in good yield. Diphosphene 1 is very stable in the solid state and also in solution. In the 31P NMR spectrum (C6D6), diphosphene 1 showed a low-fielded AB quartet at delta 501.7 and 479.5 ppm with the coupling constant 1J(PP)=546 Hz, which is characteristic of an unsymmetrically substituted trans-diphosphene. The molecular structure of 1 was established by X-ray crystallographic analysis, which showed a trans-diphosphene with a C-P-P-C torsion angle of 177.86(17) degrees . The phosphorus-phosphorus bond length of 1 [2.0285(15) A] which is considerably shorter than the typical P-P single-bond lengths (ca. 2.22-2.24 A) and within the range of reported P=P double-bond lengths (1.985-2.051 A) for diaryl diphosphenes, evidenced the P=P double-bond character of 1 in the solid state. In addition, the cyclic voltammograms of 1 showed reversible reduction and oxidation couples at -1.95 and +0.34 V versus SCE, respectively. The electrochemical results for 1 were reasonably supported by the DFT calculations, which suggested that the LUMO and HOMO orbitals should be mainly pi* orbital of the diphosphene moiety and d orbitals of the iron(II) atom, respectively.     

One-dimensional WO3 and its hydrate: One-step synthesis,structural and spectroscopic characterization

We report on a one-step hydrothermal growth of one-dimensional (1D) WO₃ nanostructures, using urea as 1D growth-directing agent and a precursor free of metals other than tungsten. By decreasing the pH of the starting solution, the size of the nanostructures was reduced significantly, this development being accompanied by the realization of phase pure hexagonal WO₃ nanorods (elimination of monoclinic impurity phase) and a red shift in optical absorption edge. Surface analyses indicated the presence of reduced tungsten species in the WO₃ nanostructures, which increased two-fold in a hydrated WO₃ phase obtained with further decrease in pH. We suggest that oxygen vacancies are responsible for this defect state in WO₃, while protons are responsible or contribute significantly to the same in the hydrated phase.     

One-step synthesis of a fluorescein derivative and mechanistic studies

We report a convenient method for the one-step synthesis of a fluorescein derivative under acidic conditions. Mechanistic studies indicate that the acid-promoted condensation of o-tolualdehyde and 4-chlororesorcinol to form the fluorescein derivative proceeds through a cyclization-oxidation pathway while an alternative oxidation-cyclization pathway remains possible.