Calix[4]arenes with electroactive tetrathiafulvalene and quinone units: metal-ion-promoted electron transfer

Metal-ion-promoted electron transfer was observed for compounds 1 and 2 based on the absorption and ESR spectral studies. These results imply that spatially adjacent arrangement of TTF and quinone units in 1 and 2 due to the calix[4]arene platform is favorable for the intramolecular electron transfer.     

New heterocyclic tetrathiafulvalene compounds with an azobenzene moiety: photomodulation of the electron-donating ability of the tetrathiafulvalene moiety

New heterocyclic TTF compounds 1a-c and 2 with an azobenzene moiety were described. The oxidation potential of 1a could be reversibly modulated by alternating UV and visible light irradiation. As a result, a molecular switch with UV/visible light as the inputs and the electrochemical signal as the output was achieved. Moreover, it was found that the influence of the azobenzene photoisomerization on the electronic property of the TTF unit became stronger with shorter spacers in compounds 1a-c.     

The synthesis of some substituted macrocyclic polyether-diester compounds with the malonyl moiety

A series of seven substituted macrocyclic polyether-diester compounds containing the malonyl moiety have been prepared.     

Donor-acceptor-donor triads incorporating tetrathiafulvalene and perylene diimide units: synthesis, electrochemical and spectroscopic studies

Three donor-acceptor-donor triads 1-3 consisting of tetrathiafulvalene units attached to perylene diimides by flexible and rigid spacers were synthesized and characterized. UV/vis spectroscopic and cyclic voltammetric results indicate that they all show negligible intramolecular charge transfer interaction in their ground states. As compared to the reference compound 21, triads 1-3 display reduced fluorescence and their fluorescence lifetimes are shortened, which is probably owing to the photoinduced electron transfer interactions between the PI units and TTF units. The different photophysical behaviors between 1 and 2 (and 3) might be due to their difference in the spatial separation of TTF and PI units. It is preliminarily found that the steric hindrance of the groups attached to TTF units can affect their photostability.     

The synthesis of macrocyclic ether-esters,thioether-esters,and ether-thiolesters with the oxalyl moiety

A new series of macrocyclic polyether-diesler compounds ( 3-12 ) have been prepared by treating various oligoethylene glyeols or mercaplans with oxalyl chloride. The compounds prepared were: 1,4,7,10,13-pentaoxacyclopentadecane-2,3-dione ( 3 ), 1,4,7,1 3-tetraoxa-10-thiacyclopenta-decane-2,3-dione ( 4 ), 1,4,10-lrioxa-7,13-dithiacyclopenladecane-2,3-dione ( 5 ), 1,4,7,10,13,16-hexaoxacyclooctadecane-2,3-dione ( 6 ), 1,4,7,10,13, 16-hexaoxacyclooctadecane-2,3,11,12-tetra-one ( 7 ), 1,4,10,13-tetraoxa-7,16-dithiacyclooctadecane-2,3,11,12-tetraone ( 8 ), 7,16-dioxa-1,4, 10,13-letralhiacyclooctadecane-2,3,11,12-tctraone ( 9 ), 1,4,7,10,13,16-hexathiacyclooctadecane-2,3,11,12-tetraone ( 10 ), 1,4,7,10,13,16,19-heptaoxacyclohencicosane-2,3-dione (11), and 1,4,7, 10,13,16,19,22-octaoxacyclolelracosane-2,3,14,15-letraone ( 12 ).     

Redox responsive molecular tweezers with tetrathiafulvalene units: synthesis, electrochemistry, and binding properties

Several new molecular tweezers with tetrathiafulvalene (TTF) arms as well as mono-TTF derivatives bearing 3,5-di-tert-butylbenzylthio groups to provide enhanced solubility were prepared starting from a bis-cyanoethyl-protected tetrathiafulvalene derivative. The X-ray crystallographic analysis of 3 and 7a showed highly distorted TTF groups and absence of close TTF-TTF contacts in the crystalline state. Comparative cyclic voltammetry (CV) measurements demonstrated that through space distance-dependent TTF-TTF interactions take place in the TTF-containing molecular tweezers, leading to electronic pairing with formation of mixed valence [TTF]₂⁺ species and splitting of the first oxidation wave. TTF-containing molecular tweezers were successfully tested as receptors for several electron-deficient substances.     

pi conjugation across the tetrathiafulvalene core: synthesis of extended tetrathiafulvalene derivatives and theoretical analysis of their unusual electrochemical properties

A series of extended tetrathiafulvalene (TTF) derivatives bearing one or two 1,4-dithiafulven-6-yl substitutents has been prepared. The new compounds present remarkable electrochemical singularities compared with other TTF derivatives, which are strongly affected by the nature of the substitution on the lateral heterocycle(s). This unusual electrochemical behaviour follows a square-scheme sequence and is attributed to structural changes upon oxidation of the pi-donating molecules. Digital simulations of the electrochemical data have been used to reach the values of the kinetic and thermodynamic constants involved in the square scheme. Theoretical calculations establish an important contribution of a highly delocalised resonant form involving a tetravalent sulphur in oxidised species, which could justify the occurrence of an electrochemical behaviour distinct from that of TTF. Finally, third-order susceptibilities chi 3 of two of these systems, for which electron-donating and electron-withdrawing substituents coexist and are conjugated through the TTF pi system, are given.     

Binaphthalene molecules with tetrathiafulvalene units: CD spectrum modulation and new chiral molecular switches by reversible oxidation and reduction of tetrathiafulvalene units

By combining the features of binaphthalene and tetrathiafulvalene (TTF), compounds 1-4 were designed for studies of chiral molecular switches. Absorption and CD spectral studies clearly indicate that the CD spectra resulting from axial chiral binaphthalene units can be modulated through the redox reactions of TTF units, which means new chiral molecular switches can be established on the basis of binaphthalene molecules with TTF units. The reference compound 5, which has one TTF unit rather than two as in the case of compounds 1, 3, and 4, failed to show such property, hinting that the presence of two or more TTF units is required for the realization of CD spectrum modulation. In addition, the manner of the CD spectrum modulation has been found to be dependent on the way TTF units are linked to the binaphthalene skeleton, in terms of the linker length, the positions for substitution, and the number of TTF units.     

Squash inhibitors: from structural motifs to macrocyclic knottins

In this article, we will first introduce the squash inhibitor, a well established family of highly potent canonical serine proteinase inhibitors isolated from Cucurbitaceae. The squash inhibitors were among the first discovered proteins with the typical knottin fold shared by numerous peptides extracted from plants, animals and fungi. Knottins contain three knotted disulfide bridges, two of them arranged as a Cystine-Stabilized Beta-sheet motif. In contrast to cyclotides for which no natural linear homolog is known, most squash inhibitors are linear. However, Momordica cochinchinensis Trypsin Inhibitor-I and (MCoTI-I and -II), 34-residue squash inhibitors isolated from seeds of a common Cucurbitaceae from Vietnam, were recently shown to be macrocyclic. In these circular squash inhibitors, a short peptide linker connects residues that correspond to the N- and C-termini in homologous linear squash inhibitors. In this review we present the isolation, characterization, chemical synthesis, and activity of these macrocyclic knottins. The solution structure of MCoTI-II will be compared with topologically similar cyclotides, homologous linear squash inhibitors and other knottins, and potential applications of such scaffolds will be discussed.     

A low-molecular-mass gelator with an electroactive tetrathiafulvalene group: tuning the gel formation by charge-transfer interaction and oxidation

A new low-molecular-mass gelator with one TTF and one urea group is described. It was found that the gel formation can be tuned by formation of CT complexes and oxidation.     

Approaches to the synthesis of cytochalasans. Part 7. Synthesis of some building blocks for the construction of the macrocyclic moiety

The synthesis of ethyl (2E, 4E, 8R)-8-methyl-10-[(2H-tetrahydropyran-2-yl)oxy]-2,4-decadienoate ( 11 ), methyl (2E, 8R)-8-methyl-10-[(2H-tetrahydropyran-2-yl)oxy]-2-decenoate ( 16 ), synthons for the construction of the macrocyclic moieties of the cytochalasins A, B and F, and of (3R)-[7-(1,3-dioxolan-2-yl)-3-methylheptyl]triphenyl-phosphonium bromide ( 24 ), a C₈-building block for deoxaphomin, proxiphomin and protophomin is described. In all instances (+)-(R)-pulegone ( 5 ) served as starting material.     

Cryptands and bismacrocycles with cyanuric and isocyanuric units: synthesis and structural investigations

Hay synthesis of cryptands and bismacrocycles starting from tripodands with cyanuric and isocyanuric cores is reported. The structure of the compounds is revealed by X-ray diffraction, NMR spectrometry and MS investigations. DNMR experiments carried out with bismacrocycles indicated the flipping of the rings and the free-energy barrier for the conformational process could be determined in one case.     

新型缺电子联吡啶大环化合物的模板合成

通过富电子对苯二酚醚链衍生物和缺电子联吡啶间的模板效应, 成功地合成了一种新型联吡啶大环化合物, 利用元素分析、核磁共振和质谱等手段对新化合物进行了表征。     

Recent methods for the synthesis of (E)-alkene units in macrocyclic natural products

(E)-Alkene units are frequently found in macrocyclic natural products. Among the reactions that form the double bond during the cyclization, the classical Horner-Emmons coupling is still frequently used with success. During the last decade, ring-closing metathesis has emerged as a very powerful tool for the synthesis of large rings, but the E/Z selectivity, which is rarely predictable, depends on many factors which will be discussed in this review. The best solution might be a two-step procedure involving ring-closing alkyne metathesis (RCAM) followed by stereoselective reduction of the macrocyclic alkyne unit to the corresponding E double bond.     

Triphenylamine-based electroactive compounds: synthesis,properties and application to organic electronics

This review is devoted to low and high molecular mass electroactive materials containing triphenylamine (TPA) structural units. It is shown that by appropriate selection of C–C coupling methods, it is possible to obtain solution-processable, electroactive materials of tunable donor–acceptor properties, suitable for the use as active layers in p-channel or ambipolar field effect transistors, as hole-transporting layers and as electroluminophores in organic light-emitting diodes. Other applications involve their use as components of bulk heterojunctions in organic solar cells and dye-sensitized solar cells. Since TPA-based materials exhibit high electrochemical reversibility, they can also be technologically exploited as solution-processable electrochromic materials.     

Ring-closing metathesis of olefinic peptides: design, synthesis, and structural characterization of macrocyclic helical peptides

Heptapeptides containing residues with terminal olefin-derivatized side chains (3 and 4) have been treated with ruthenium alkylidene 1 and undergone facile ring-closing olefin metathesis (RCM) to give 21- and 23-membered macrocyclic peptides (5 and 6). The primary structures of peptides 3 and 4 were based upon a previously studied heptapeptide (2), which was shown to adopt a predominantly 3(10)-helical conformation in CDCl(3) solution and an alpha-helical conformation in the solid state. Circular dichroism, IR, and solution-phase (1)H NMR studies strongly suggested that acyclic precursors 3 and 4 and the fully saturated macrocyclic products 7 and 8 also adopted helical conformations in apolar organic solvents. Single-crystal X-ray diffraction of cyclic peptide 8 showed it to exist as a right-handed 3(10)-helix up to the fifth residue. Solution-phase NMR structures of both acyclic peptide 4 and cyclic peptide 8 in CD(2)Cl(2) indicated that the acyclic diene assumes a loosely 3(10)-helical conformation, which is considerably rigidified upon macrocyclization. The relative ease of introducing carbon-carbon bonds into peptide secondary structures by RCM and the predicted metabolic stability of these bonds renders olefin metathesis an exceptional methodology for the synthesis of rigidified peptide architectures.     

Cyclopropylcarbinyl radicals as three-carbon insertion units: easy synthesis of C-15 macrocyclic ketones by three-carbon ring expansion

Thermal isomerization of cyclic 3-cyclopropyl ketones under FVP conditions at 620 °C provides a new and convenient route to δ,ε-unsaturated cycloalkanones. The synthetic potential of this novel three-carbon ring expansion has been demonstrated by the synthesis of (±)-muscone from inexpensive C-12 starting material.     

Addition reaction of azido-exTTFs to C60: synthesis of fullerotriazoline and azafulleroid electroactive dyads

[structure: see text] The addition reaction of azido-exTTFs to C(60) affords electroactive fullerotriazoline and azafulleroid dyads, which behave as amphoteric redox systems. Fluorescence experiments and transient absorption spectroscopy reveal that excitation of the fullerene moiety leads to radical pair lifetimes that are 2 orders of magnitude higher than those previously reported for related fullerotriazolines.