Tetrathiafulvalene. XXII [1] Redox- und spektroskopische Eigenschaften von Tetrathiafulvalenen (TTF) und Tetraselenafulvalenen (TSF) sowie deren Mono- und Dikationen

Tetrathiafulvalenes. XXII. Redox- and Spectroscopic Properties of Tetrathiafulvalenes (TTF) and Tetraselenafulvalenes (TSF) and their Mono- and Dications The polarographic oxidation potential of TTF is decreased by alkyl- and increased by aryl-substituents. The oxidation potentials of arylated TTF can be correlated with σ⁺-constants (σ  0,1). TSF are weaker donors than the respective TTF. Alkyl substitution at TTF causes a bathocromic shift and aryl substitution a hypsochromic shift of the longest wavelength absorption band. In the mono- and dications of TTF a bathochromic shift of this absorption band is observed by alkyl- as well as aryl-substituents which is especially pronounced, when the molecule is planar.     

Eigenschaften der CT-Banden einiger EDA-Komplexe vom aπ-bπ-Typ

Properties of the CT-Bands of some aπ-bπ-Type EDA-Complexes CT-bands with two maxima exist in the visible range of the spectra of EDA-complexes between tetracyanoethylene (TCNE) and stilbene derivatives. The CT-bands in the long wave length range of TCNE-complexes are in a linear correlation with the band maxima of the corresponding chloranile (CA) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) complexes. Ionization energies of the donors calculated from band positions of TCNE-, CA- and TCNQ-complexes are in a good accordance. For long wave length maxima of double bands a linear coherence exists between the transition energy and the stability of complexes.     

Tetrathiafulvalene. XXVII [1] Darstellung und Eigenschaften cis- und trans-isomerer Dihydrophenanthreno-Tetrathiafulvalene

Tetrathiafulvalenes. XXVII. Syntheses and Properties of cis- and trans-Isomers of Dihydrophenanthreno-Tetrathiafulvalenes The synthesis of anellated tetrathiafulvalenes (TTF) 10a–c , 11a–b via the 1,3-dithiolium salt/triethylamin or 1,3-dithiole-2-thione/triethyl phosphite route is described. The dihydrophenanthreno-anellated TTFs 10a, b can be thermally transformed into the phenanthreno-anellated TTFs 11a, b . Only in the case of the dihydrophenanthreno-anellated TTF 10b (with “α-naphthyl structure”) the isolation of the cis- and trans-isomer was possible due to differences in the solubility. Starting from the pure cis- or trans-isomer the radical salts of 10b are reducible to a 1:1 mixture of the cis/trans stereo isomers. The spectroscopic, electrochemical, and conductivity properties of the synthesized TTFs and their complexes with iodine, TCNQ, and DDQ are described.     

Tetrathiafulvalene. XXIV. Gewinnung von cis- und trans- Isomeren bei Tetrathiafulvalenen (TTF)

Tetrathiafulvalenes. XXIV. Isolation of cis- and trans-Isomers of Tetrathiafulvalenes (TTF) The synthesis of naphthylsubstituted TTF permits in the case of the α-naphthyl-methylsubstituted TTF the isolation of the cis- and trans-isomer by reason of differences in the solubility. The spectroscopical and electrochemical properties of naphthylsubstituted TTF are described.     

Untersuchungen zur Photoleitfähigkeit von alkoxysubstituierten Oligo- und Poly(1,4-phenylenethenylen)en

Investigations on the Photoconductivity of Alkoxy Substituted Oligo- and Poly(1,4-phenyleneethenylene)s The photoreactivity and the photoconductivity of the mono- and dialkoxy substituted oligo- and poly(1,4-phenyleneethenylene)s 1/1′a-n were investigated in order to optimize the photoconducting properties of these materials. Increasing the length of the side chains enhances the average length of the main chain during the polycondensation and decreases the band gap till the limit of convergence is reached. The highest photoconductivity was observed for the 2,5-dipropyloxy system 1/1′j . Longer side chains render the charge transfer from chain to chain more difficult. The measurements were performed in dispersion layers and related to the industrial standard 3 . Compound 1m was also measured in a pure state as transparent film and compared to a poly(N-vinylcarbazole) film which shows a dye-sensitized photoconductivity. In both cases the optimized systems 1/1 ′ were markedly superior to the standards. The highest sensitivity could be observed for wavelengths λ lying close to the absorption maxima λ_max. The compounds 1/1 ′ have a high photostability on irradiation with visible light; however, they are rapidly destroyed by UV light (254 nm).     

DNA compaction by divalent cations: structural specificity revealed by the potentiality of designed quaternary diammonium salts

DNA interaction with quaternary diammonium dications, R(CH(3))(2)N(+)(CH(2))(n)N(+)(CH(3))(2)R, having various intercharge distances, lengths, and branching, and the chemical nature of the hydrophobic substituents were investigated by fluorescent microscopy and circular dichroism (CD) spectroscopy to reveal their structural specificity for binding to DNA. The conformational behavior of DNA was found to be highly sensitive to the structure of the dications with separated charges. The distance between two ammonium groups greatly influences the compaction activity of the dications. To explain this situation, we proposed a model that demonstrates that the charge density of the dication and the geometric fit between DNA phosphates and the ammonium groups in the dications play an important role in providing efficient DNA collapse. Elongation of the alkyl substituents (R) in the diammonium salts from ethyl to hexyl did not generate any significant alterations in the compaction activities, whereas the branching of substituents caused a drastic decrease in their compaction ability. Based on the results of CD spectroscopy, it was found that the ability of the dications to provoke a DNA transition from the B-form to A-form was also specific: it depended on their intercharge distances and was independent of the length of alkyl substituents.     

Tetrathiafulvalene. XXV [1]. Konjugativ verknüpfte polymere Tetrathiafulvalene (TTF)

Tetrathiafulvalenes. XXV. Conjugative Connected Polymeric Tetrathiafulvalenes (TTF) Syntheses and properties of a conjugative connected polymeric TTF (by tetrahydroanthracene units) and phenylene-bridged polymeric TTF are described. These polymers react with bromine, iodine or tetracyanoquinodimethane and form the radical cation salts, whose electrical conductivity is determined. The conjugatively connected polymeric radical cation salts show a higher conductivity than the twisted phenylene-bridged polymeric radical cation salts.     

Photochemie von Bis-2H-tetrazolen. III. Nachweis von Bisnitriliminen durch Tieftemperatur-UV-Spektroskopie und thermische Folgereaktionen durch Photolyse von Bis-2H-tetrazolen

Photochemistry of Bis-2H-tetrazoles. III. Detection of Bisnitrilimines through Low-Temperature-UV-Spectroscopy and Thermic Consecutive Reactions through Photolysis of Bis-2H-tetrazoles The photolysis of 2H-tetrazoles ( 1 ) leads to nitrilimines. Bis-2H-tetrazoles form correspondingly bisnitrilimines 2 . They were detected directly by the photolysis of bis-2H-tetrazoles ( 1 ) in an ethanol/ether glass at 95 K. The absorption maxima are depend in an expected manner on the substituents. In the presence of dipolarophiles the reaction of bis-2H-tetrazoles ( 1 ) at room temperature gives bis-Δ²-pyrazolines ( 3 ). These reactions can also be explained by a photoreaction of bis-2H-tetrazoles ( 1 ) to bisnitrilimines 2 at 95 K and subsequent cycloaddition above 150 K. Some bis-Δ²-pyrazolines ( 3 ) are described. The photolyses of bis-2H-tetrazoles ( 1 ) to the bisnitrilimines 2 proceed as one step eliminations of two molecules of nitrogen.     

Synthesen und Eigenschaften Mono- und diphenylsubstituierter Monothio-β-dicarbonylverbindungen und ihrer Nickel(II)chelate

Syntheses and Properties of Mono- and Disubstituted Monothio-β-dicarbonyl Compounds and their Nickel(II) chelates Reaction of phenylacetaldehyde with phosphorous oxichloride and dimethylformamide yielded 3-chloro-2-phenyl-propenal, which was converted into 2-phenyl-monothiomalonic dialdehyde 2 by treating with sodium sulfide nonahydrate. Furthermore the reactions of other mono- and diphenylsubstituted monothio-β-dicarbonyl compounds with aniline on the one side and nickel(II)acetate on the other side have been studied. It was shown, that compounds 1–6 react in different way with aniline yielding either sulfur free products or in case of 1 and 4 enaminothioketones, which are of interest as building blocks for syntheses. In contrast to this the nickel complexes of 1–6 indicates an one another similar, typical chelate structure, which have been elucidated by u.v.-vis-, i.r.- and x-ray photoelectron spectroscopy.     

Products of the Reaction Between Alcohols and Phosphorus Pentoxide. III. Identification by Infrared Spectrophotometry

The various compounds obtained by the reaction P₄O₁₀ + 4ROH (where R represents hydrocarbon radicals of various length and structure) were identified by infrared spectrophotometry of the fractions separated by column chromatography. The identification was made possible by a comparison between the relative values of the integrated absorption for the P = O, P-O-P, P-O-C and O-H bands with those of known standards. For the reaction of phosphorus pentoxide with ethanol, the compounds formed were found to be: mono-, di- and triethyl phosphate, mono-, (1, 2) di- and triethyl-pyrophosphate; (1, 3) di- and (1, 2, 3) triethyl triphosphate; mono- and diethyl trimetaphosphate. With other alcohols, only homologs of these compounds were found, but always fewer compounds. Uncertainty between possible isomers was resolved by identification of their acid hydrolysis products.     

Untersuchungen zur Sulfochlorierung von Paraffinen. III. 1H- und 13C-NMR-Spektren aliphatischer und cycloaliphatischer Mono- und Disulfochloride

Studies on the Sulphochlorination of Paraffins. III. ¹H- and ¹³C-N.M.R. Spectra of Aliphatic and Cycloaliphatic Mono- and Disulphonylchlorides Isomeric monosulphonylchlorides of propane, butane, and heptane as well as disulphonylchlorides of propane, butane, and pentane are measured ¹H- and ¹³C-n.m.r.-spectroscopically. Including several other aliphatic and cycloaliphatic sulphonylchlorides, the use of n.m.r. spectroscopy to identification and estimation of the composition of mono- and disulphonylchloride mixtures is discussed.     

A comparative study of gangliosides from the brains of various species

A comparison is made of the sialic acid and hexose content of crude gangliosides from the brains of 13 species, including mammals, a bird, and amphibian, a reptile and fish. The sialic acid content is relatively constant from species to species. Gangliosides are less abundant in tissues other than the brain. Four species (cat, dog, pig and sheep) were selected for the determination of their major ganglioside subfractions. The ganglioside subfractions were isolated (after extraction and partition dialysis) using descending thin layer chromatography. The population of ganglioside molecules varied from species to species. From dog and sheep a mono-, a di- and a trisialoganglioside were obtained; from cat a mono-, a di- and two trisialogangliosides; and from pig a mono- and two disialogangliosides. Each ganglioside subfraction was found to contain glucose, galactose and galactosamine in the ratio of approximately 1∶2∶1. The fatty acid moieties consisted of more than 80% stearic acid with lesser amounts of arachidic, palmitic and behenic acid. Sphingosine analyses indicated ratios of sphingosine to icosisphingosine of 7∶3 for the monosialo-, 1∶1 for the disialo- and 3∶7 for the trisialogangliosides.     

Untersuchungen zum UV/Vis-Spektralverhalten von Azofarbstoffen. XX. Zum unterschiedlichen Substituenteneinfluß auf die Absorptionsmaxima von Hydrazonen und Benzendiazoniumionen

Studies on UV/Vis Absorption Spectra of Azo Dyes. XX. On the Different Substituent Effects on the Absorption Maxima of Hydrazones and Benzenediazonium Ions PMO theory predicts that substituent effects on the absorption maxima of benzenediazonium ions are partly contrary to those in hydrazones. Therefore, it seemed likely that azo coupling products absorbing at shorter wavelengths than the parent diazonium ions should exist. This is confirmed experimentally. The hydrazones 4c and 5c absorb significantly hypsochromic than the diazonium ion 3c .     

Photochemical modulation of DNA conformation by organic dications

A group of azobenzene derivatives containing two quaternary ammonium groups with various intercharge distances between them was synthesised and used to control photochemically the conformation of genomic DNA by switching the distance between cationic ammonium groups in the dications. It was found that isomerisation of either dication from the trans form to cis resulted in an increase in the dication's efficiency for DNA compaction; this is associated with a decrease in intercharge distance between ammonium groups and leads to a better match of the binder's cationic groups to adjacent phosphate groups of DNA. Ammonium dications have several important advantages over the photosensitive surfactant type of diazobenzene reported earlier: they can be used at significantly lower (>100-fold) concentrations than photosensitive surfactants, and DNA conformation control can be performed over a broader concentration range of dications. The influence of intercharge distance in photosensitive dications on photo-induced DNA binding discrimination is discussed, and the molecular mechanism is proposed.     

The reversible oxidation of aromatic cation radicals to dications. Solvents of low nucleophilicity

Reversible behavior for both electron transfers for oxidation of aromatic compounds to cation radicals and dications was observed in several common electrolytic solvents. Nitriles, nitro compounds and dichloromethane can all be rendered essentially nucleophile free for voltammetric purposes simply by conducting the voltammetric measurements over neutral alumina shortly after the mixture has been stirred. Solvents containing trifluoroacetic acid and the corresponding acid anhydride are not only useful for voltammetry but can also be used to prepare stable solutions of cation radicals and dications. Equilibrium constants for the disproportionation of cation radicals to dications were calculated from the reversible electrode potentials and the effect of changes in the solvent system on the equilibrium constants is discussed.     

Partialsynthesen von Cardenoliden und Cardenolid-Analogen. VII. Synthese A/B-cis- und C/D-cis-verknüpfter Steroidmono- und -bis(α-methylen-γ-butyrolactone)

Partial Syntheses of Cardenolides and Cardenolide Analogues. VII. Synthesis of A/B-cis- and C/D-cis-linked Steroidal Mono- and Bis (α-methylene-γ-butyrolactones) The synthesis of A/B-cis- and C/D-cis-linked steroidal mono- and bis(α-methylene-γ-butyrolactones) 10–13 , 18 and 24 by Reformatsky-type reaction of 3β-acetoxy-14-hydroxy-5β, 14β-androstan-17-one( 6 ), 14-hydroxy-5β, 14β-androstane-3,17-dione ( 8 ), 3β-acetoxy-14-hydroxy-5β,14β-pregnan-20-one ( 17 ) and 14-hydroxy-5β,14β-pregnane-3,20-dione ( 23 ), respectively, with ethyl α-(bromomethyl)acrylate is described. All steroidal lactones exhibit strong inhibitory activity on the proliferation of Ehrlich ascites carcinoma cells in suspension culture. For inhibitory activity the lactone moiety at C-17 of the steroid molecule is more important than the lactone moiety at C–3 and C–20, respectively.     

Synthesis and physico-chemical properties of highly conjugated azo-aromatic systems. 4-(azulen-1-yl)-pyridines with mono- and bis azo-aromatic moieties at C3-position of azulene

Highly conjugated azo-aromatic systems have been prepared in high to moderate yields by linking mono- and bis-azo aromatic fragments to 4-(Rn-azulen-1-yl)-2,6-dimethyl-pyridine. The synthesized π-extended systems have been studied by NMR spectroscopy, UV-Vis and electrochemistry. Systematic increase of the conjugation along the azobenzene skeleton has affected the spectral properties of the azophenyl substituted 4-(azulen-1-yl)-pyridine. The synthesized compounds exhibit a bathochromic shift of the visible absorption maxima with the increase of the conjugating skeleton and introduction of an electron-withdrawing group. The electrochemical behavior revealed a high stability toward oxidation owing to the higher polarization induced by the azulenylpyridine moiety.     

Strained Mono- and Dications. On the Structures of [(CCH2)7H]2⊕ and [(CCH3)7CH3]2⊕ Dications

The reactions of alcohol 1 with HF-SbF₅ and of alcohol 8 with FSO₃H-SbF₅ at low temperatures afforded dications [(CCH₃)₇H]^2⊕ and [(CCH₃)₇CH₃]^2⊕, respectively. Both NMR (¹H and ¹³C) data and analysis of the products, obtained upon quenching of the cations, were used to discuss the possible structures of these cations. Both ions showed a remarkable NMR behaviour, viz. an equivalency of all methylgroups on the one hand and all skeleton carbon atoms on the other hand, indicating a high symmetry or a rapid (on the NMR time scale) process. Using model compounds the weighted average ¹³C-NMR chemical shifts of reasonable structures for the ions were calculated and compared with the experimentally obtained values. The conclusion is drawn that the former reaction presumably leads to dications 34 and 36 and the latter reaction to dication 51 .     

Electrochemical oxidation of hydrophobic compounds in aqueous micellar solutions and oil-in-water emulsions

The electrochemical oxidation of ferrocene (Fc) and tetrathiofulvalene (TTF) has been investigated in micelles and dodecane-in-water emulsions in order to compare the diffusional process involved in these systems. It is found that the diffusion coefficients of Fc and TTF, determined from the observed limiting currents at the rotating disc electrode, are governed by the solubilization equilibrium of the neutral substrates which are predominantly solubilized in the micelle or oil-droplet phase. In the emulsion, the cyclic voltammograms show that the current is controlled also by the rate constants of the substrate partition, which depend on the size of the emulsion droplets. The determination of the diffusion coefficients of Fc⁺ and TTF⁺, produced in situ by controlled potential electrolysis, showed that, except in SDS micellar solutions, the monocation radicals are solubilized mainly in the aqueous phase. As a result, the diffusion coefficients of the species involved in the redox system are different. In the case of TTF, the above results have a great influence upon the second oxidation step TTF⁺ → TTF²⁺. Indeed, the homogeneous solution reaction between TTF and the electrogenerated dication TTF²⁺ leads to the monocation TTF⁺ which diffuses more rapidly than its parent molecule TTF. The ratios of the two waves in cyclic and rotating disc electrode voltammetry show that the enhancement of the second wave depends mainly on the difference between the diffusion coefficients of TTF and TTF⁺ and that the nature of the solution or the size of the disperse phase has little influence upon the reaction rate of the homogeneous solution reaction.     

Synthesis and properties of tetrathiafulvalene-porphyrin assemblies

Two donor-σ-acceptor molecular systems incorporating tetrathiafulvalene (TTF) and tetraphenylporphyrin (TPP) units, TTF-TPP (dyad 1) and TTF-TPP-TTF (triad 2), were synthesized. Both dyad 1 and triad 2 and their synthetic intermediates have been characterized by ¹H nuclear magnetic resonance (¹H NMR) and mass spectrography (MS). Their ultraviolet and visible spectroscopy (UV-Vis) and cyclic voltammetry (CV) showed negligible intramolecular charge transfer interaction in their ground states. Their fluorescence intensity was strongly quenched compared with TPP, which implied the photoinduced electron transfer occurred from the TTF unit to the TPP unit in the excited state. On the other hand, their fluorescence intensity could be modulated by sequential oxidation of the TTF unit using chemical methods, which exhibited their potential application in fluorescence molecular switch.