exTTF Units Research Articles

Poly(exTTF): a novel redox-active polymer as active material for li-organic batteries.

The first polymer bearing exTTF units intended for the use in electrical charge storage is presented. The polymer undergoes a redox reaction involving two electrons at -0.20 V vs Fc/Fc(+) and is applied as active cathode material in a Li-organic battery. The received coin cells feature a theoretical capacity of 132 mAh g(-1) , a cell potential of 3.5 V, and a lifetime exceeding more than 250 cycles.

Synthesis and complexation study of new ExTTF-based hosts for fullerenes.

A new series of exTTF hosts has been synthesized for supramolecular binding study of fullerenes C60 and C70. Binding constants for C60 in chlorobenzene, toluene, toluene-CH2Cl2 and CS2 have been calculated for different hosts and a direct structure-affinity relationship has been established. As predicted, receptors with two exTTF moieties (1, 3 and 4) have demonstrated higher binding abilities toward C70 than C60. Depending on the linker used to attach the exTTF unit to the core of the host, different binding modes (1 : 1 and 2 : 1) have been obtained.

Self-assembly of a new C60 compound with a L-glutamid-derived lipid unit: formation of organogels and hierarchically structured spherical particles

A new C60-based low-molecular weight gelator (LMWG 1) with a L-glutamid-derived lipid unit was synthesized and characterized. LMWG 1 can gel toluene, p-xylene and benzene. Moreover, its gelation ability can be further enhanced by addition of an exTTF derivative (compound 2), for which the intermolecular interaction between the C60 unit in 1 and the exTTF unit in 2 is responsible based on the absorption and NOE difference 1H-NMR spectral studies. Additionally, gelation-induced CD signals are observed for the gel with LMWG 1 and that of LMWG 1 doped with compound 2. Further studies indicate that the self-assembly structures of LMWG 1 in the gel phases can be modulated by the addition of compound 2. In addition, the self-assembly of LMWG 1 in DMSO leads to spherical particles of several microns in size, and the surfaces of these spherical particles are hierarchically structured with nano-fibers. Moreover, the thin-film of spherical particles exhibits water-repellent hydrophobicity.

Hole‐Transfer Dyads and Triads Based on Perylene Monoimide, Quaterthiophene, and Extended Tetrathiafulvalene

Two families of dyad and triad systems based on perylene monoimide (PMI), quaterthiophene (QT), and 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene (extended tetrathiafulvalene, exTTF) molecular components have been designed and synthesized. The dyads (D1 and D2) are of the PMI-QT type and the triads (T1 and T2) of the PMI-QT-exTTF type. The two families differ in the saturated or unsaturated nature of the linker groups (ethynylene in D1 and T1, ethylene in D2 and T2) that bridge the molecular components. The dyads and triads have been characterized by electrochemical, photophysical, and computational methods. Both the experimental and the computational (DFT) results indicate that in the unsaturated systems strong intercomponent interactions lead to substantial perturbation of the properties of the subunits. In particular, in T1, delocalization is particularly effective between the QT and exTTF units, which would be better viewed combined as a single electronic subsystem. For the dyad systems, the photophysics observed following excitation of the PMI unit is solvent-dependent. In moderately polar solvents (dichloromethane, diethyl ether) fast charge separation is followed by recombination to the ground state. In toluene, slow conversion to the charge-separated state is followed by intersystem crossing and recombination to yield the triplet state of the PMI unit. The behavior of the triads, on the other hand, is remarkably similar to that of the corresponding dyads, which indicates that, after primary charge separation, hole shift from the oxidized QT component to exTTF is quite inefficient. This unexpected result has been rationalized on the basis of the anomalous (simultaneous two-electron oxidation) electrochemistry of exTTF and with the help of DFT calculations. In fact, although exTTF is electrochemically easier to oxidize than QT by around 0.6 V, the one-electron redox orbitals (HOMOs) of the two units in triad T2 are almost degenerate.

A New ex-TTF-Based Organogelator: Formation of Organogels and Tuning with Fullerene

A new ex-TTF-based organogelator with L-glutamide-derived lipid unit (compound 1) was synthesized and characterized. The resulting transparent organogels can be obtained with several organic solvents such as toluene, DMSO, and ethanol. It is interesting that its gelation ability can be further enhanced by addition of C(60). The (1)H NMR and absorption spectral studies indicate that the intermolecular interaction between the ex-TTF unit in 1 and C(60) may be responsible for this phenomenon. Further studies imply that the assembly structures in the gel phases in the absence and presence of C(60) may be different. Additionally, organogels can also be prepared with compound 1 and PCBM, and the corresponding xerogel was used to modify ITO electrode. A stable and rapid photocurrent was generated after exposure of the modified ITO electrode to light. This may provide an alternative way for photocurrent generation with high energy conversion efficiency.

Tripodal exTTF-CTV Hosts for Fullerenes

A receptor for fullerenes featuring three exTTF units linked to a CTV scaffold is described. The exTTF-CTV host forms remarkably stable complexes with both C(60) (log K(a) = 5.3 +/- 0.2) and C(70) (log K(a) = 6.3 +/- 0.6). Light-induced ESR spectra demonstrate that intracomplex PET processes take place in solution.

Large exTTF-Based Dendrimers. Self-Assembly and Peripheral Cooperative Multiencapsulation of C60

The convergent synthesis of large monodisperse dendrimers, up to the fourth generation, decorated in their periphery with pi-extended tetrathiafulvalene units is reported, and their redox and supramolecular properties are investigated. A number of experiments (MALDI-TOF, (1)H NMR at variable temperature and different concentration, DLS, AFM and SEM imaging) confirm the self-aggregation process of these dendrimers, despite the butterfly-like shape of the exTTF units, highly distorted from planarity, to form large supramolecular architectures in the gas phase, in solution, and on a mica surface. Dendrimers 5, 9, and 12 host a number of C60 molecules to form segregated arrays of donor and acceptor units which could give rise to valuable materials useful for the preparation of optoelectronic devices. UV-vis titration experiments demonstrate that complexation of C60 occurs in a positive cooperative manner. Cyclic voltammetry experiments show that the peripheral exTTF units are involved in multioxidation processes. The self-diffusion coefficients (D) of the dendrimers reported herein and the previously reported exTTF (1) and tweezer (2) have been calculated from their chronoamperograms at different concentrations and by the Cottrell equation and, where possible, by PFG-NMR. The calculated values for D demonstrate the decrease of this magnitude with increasing dendrimer size.

Thiolated π-Extended Tetrathiafulvalenes: Versatile Multifunctional π-Systems

Derivatives of 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene (ex-TTF) have been synthesized by a new synthetic methodology, viz., direct phosphite-mediated cross-couplings of anthraquinone with 1,3-dithiole-2-thione derivatives. These ex-TTFs bear one, two, or four cyanoethyl-protected thiol groups on the dithiole rings. Deprotection (NaOMe, MeOH, DMF, 20 degrees C) and trapping of the transient thiolates with electrophiles have afforded the new ex-TTF trimer 19, dimeric cyclophanes 22 and 25, the tetrakis(hydroxyethylthio) derivative 23, and the strained cyclophane 24. Solution redox properties have been studied by cyclic voltammetry. For compounds 19, 22, and 25 each ex-TTF unit behaves as an independent 2-electron redox system giving rise to a single, quasi-reversible 6-, 4-, and 4-electron wave, respectively. The Eox value for 24 (0 --> 2+ wave) is positively shifted by 290 mV compared to that of its precursor 15 due to the short bridge in 24 obstructing the conformational change which accompanies oxidation. X-ray crystal structures of 23.2.5MeOH, 23.1.5MeCN, 24.CH2Cl2, and 24.1.5CH2Cl2 show the saddle-shape folding (typical of ex-TTF derivatives), which in 24 is enhanced by the pentamethylene chain bridging the dithiole units. Both solvates of 23 show an unprecedented crystal packing motif due to hydrogen bonding.

Supramolecular Pseudo‐Rotaxane Type Complexes from π‐Extended TTF Dimer Crown Ether and C60.

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Electronic Interactions in a New π‐Extended Tetrathiafulvalene Dimer

The first pi-extended tetrathiafulvalene (exTTF) dimer in which the two exTTF units are covalently connected by 1,3-dithiole rings has been obtained in a multistep synthetic procedure involving the Ullmann cross-coupling reaction by using copper(I) thiophene-2-carboxylate (CuTC). The electronic spectrum reveals a significant electronic interaction between the exTTF units. The electrochemical study carried out by cyclic voltammetry in solution and in thin-layer conditions, and the electrochemical simulation and spectroelectrochemical (SEC) measurements confirm the electronic communication and show that the oxidation of dimer 14 occurs as two consecutive 2 e(-) processes D(0)-D(0)-->D(2+)-D(0)-->D(2+)-D(2+). Theoretical calculations, performed at the B3P86/6-31G* level, confirm the experimental findings and predict that 14(2+) exists as a delocalized D(.+)-D(.+) species in the gas phase and as a localized D(2+)-D(0) species in solution (CH(3)CN or CH(2)Cl(2)). Oxidation of 14(2+) forms the tetracation 14(4+) which is constituted by two aromatic anthracene units bearing four aromatic, almost orthogonal 1,3-dithiolium cations.

Supramolecular pseudo-rotaxane type complexes from π-extended TTF dimer crown ether and C 60

A new cyclophane-type crown ether endowed with two exTTF units forms supramolecular ensembles with different dibenzylammonium salts with a binding constant of K a∼50 M −1 determined by 1H NMR and fluorescence experiments. Cyclic voltammetry studies show the existence of electronic interaction between the exTTF units due to the flexible nature of the crown ether chains.

Synthesis and electron-donor ability of the first conjugated pi-extended tetrathiafulvalene dimers.

A series of novel conjugated homo (16a,b) and heterodimers (20) of pi-extended tetrathiafulvalenes with p-quinodimethane structures (exTTFs) linked by a conjugative vinyl spacer have been prepared by olefination Wittig-Horner reaction from the corresponding quinones (14, 19) and phosphonates (15a,b). The redox properties, determined by cyclic voltammetry, reveal a strong donor character and the presence of only one four-electron oxidation wave to form the tetracation species at oxidation potential values quite similar to those found for the related monomers. Theoretical calculations (PM3) show a planar central stilbene moiety and highly distorted exTTF units. The electronic spectra support as well as the electrochemical data and theoretical calculation the lack of significant communication between the exTTF units.

Probing charge separation in structurally different C60/exTTF ensembles.

The scope of the present work is to highlight the effects stemming from different C60/exTTF linkages (exTTF = 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene)-either via an anthracene unit or a dithiole ring. Particular emphasis is placed on photoinduced electron-transfer features. Therefore, we devised a new series of C60-exTTF ensembles, synthesized via 1,3-dipolar cycloaddition and Diels-Alder cycloaddition reactions, in which exTTF units are separated from C60 by two single bonds (3a-c, 4), one vinylene unit (5a), or two vinylene units (5b). The cyclic voltammetry reveals an amphoteric redox behavior with remarkably strong electron-donor ability of the trimethyl-substituted exTTF moiety in 4 and 5a,b. Steady-state and time-resolved photolytic techniques show that the fullerene singlet excited state in (3a-c, 4, and 5a,b) is subject to a rapid electron-transfer quenching. The resulting charge-separated states, that is C60*(-)-exTTF*+, were identified by transient absorption spectroscopy. We determined radical pair lifetimes of the order of 200 ns in benzonitrile. This suggests (i) that the positive charge of the exTTF*+ is delocalized over the entire donor rather than localized on one of the 1,3-dithiole rings and (ii) that linking exTTF via the anthracene or 1,3-dithiole ring has no appreciable influence. Increasing the donor-acceptor separation via implementing one or two vinylene units as spacers led to improved radical pair lifetimes (5a: tau = 725 ns; 5b: tau = 1465 ns).

Synthesis and Properties of Bingel‐Type Methanofullerene—π‐Extended‐TTF Diads and Triads.

Novel C(60)/pi-extended tetrathiafulvalene (exTTF) diads (12a-c) and triads [D(2)A (14a-c) and DA(2) (25, 27a-c)] have been synthesized by the Bingel cyclopropanation reaction of the respective exTTF-containing malonates and [60]fullerene. The reaction of exTTF-bismalonates with C(60) affords the respective C(60)-exTTF diads (26a-c) together with the triad C(60)-exTTF-C(60) (25, 27a-c) and a regioisomeric mixture of bisadducts (28b-c). Theoretical calculations (PM3) predict the favored geometry for triads 14a-c depending upon the orientation (up and down) of the 1,3-dithiole rings in the exTTFs, as well as the more stable regioisomers for the bisadducts 28. Cyclic voltammetry measurements reveal that C(60) and exTTF units do not intereact in the ground state. Compounds 26a-c and 27a-c are not electrochemically stable. A photoinduced electron transfer leading to the formation of the radical pair (C(60)(-)-exTTF(*+)) has been observed for compounds 14a-c.

Synthesis and properties of Bingel-type methanofullerene-pi-extended-TTF diads and triads.

Novel C(60)/pi-extended tetrathiafulvalene (exTTF) diads (12a-c) and triads [D(2)A (14a-c) and DA(2) (25, 27a-c)] have been synthesized by the Bingel cyclopropanation reaction of the respective exTTF-containing malonates and [60]fullerene. The reaction of exTTF-bismalonates with C(60) affords the respective C(60)-exTTF diads (26a-c) together with the triad C(60)-exTTF-C(60) (25, 27a-c) and a regioisomeric mixture of bisadducts (28b-c). Theoretical calculations (PM3) predict the favored geometry for triads 14a-c depending upon the orientation (up and down) of the 1,3-dithiole rings in the exTTFs, as well as the more stable regioisomers for the bisadducts 28. Cyclic voltammetry measurements reveal that C(60) and exTTF units do not intereact in the ground state. Compounds 26a-c and 27a-c are not electrochemically stable. A photoinduced electron transfer leading to the formation of the radical pair (C(60)(-)-exTTF(*+)) has been observed for compounds 14a-c.

Synthesis and properties of push–pull chromophores for second-order nonlinear optics derived from π-extended tetrathiafulvalenes (TTFs)

Novel π-extended tetrathiafulvalene (exTTF) derivatives connected to a p-nitrophenyl electron-accepting unit through a π-conjugated oligoenic spacer ( 14a– c – 16a– c ) show good second-order optical nonlinearities. The effect of the conjugation length of the oligoenic spacer and the presence of a thiophene ring in the π-conjugated bridge ( 20a– c ) have been theoretically (PM3) and/or experimentally (EFISH technique) studied. The redox properties of the novel compounds have been investigated by cyclic voltammetry (CV) and the CV data reveal the good donor ability of the exTTF unit. Although the energy of the intramolecular charge-transfer (ICT) band displayed by these compounds and their redox potentials are fairly insensitive to the nature of the conjugated spacer linking the donor and the acceptor moieties, an increase in their second order nonlinear optical responses is observed on increasing the conjugation lengths. Compounds 20a– c bearing a thiophene ring show a remarkable thermal stability with decomposition temperatures over 400°C. A new series of D-π-A compounds ( 23a– c ) bearing a 1,3-dithiol-2-ylidene donor unit has also been synthesized and studied.