David Kreher

Rigidified tetrathiafulvalene–[60]fullerene assemblies: towards the control of through-space orientation between both electroactive units

Our recent works on fused TTF–C60 dyads, (TTF)n–C60 polyads and C60–TTF–C60 dumbbell triads in which the acceptor C60 is doubly tethered to the donor tetrathiafulvalene through a rigidified cyclohexene ring are presented. This approach was developed in order to control the relative orientation as well as the distance between both donor and acceptor entities. Thereby, through-space interactions which are of great importance for photoinduced electron- and/or energy-transfer processes are expected to dominate because of the special topology of the molecules. The two linked C60 and TTF chromophores in such adducts are not only in close proximity but also have optimal orbital orientations, thus facilitating these through-space electronic interactions. These new C60-based assemblies were synthesized by [4 + 2] Diels–Alder cycloaddition nreactions. The different methodologies considered for their synthesis are discussed, their analytical, spectroscopic characterizations and electrochemical properties are also described. The selective electro-oxidation or reduction afforded the corresponding radical cation and radical anion which were characterized by EPR. These C60-based assemblies were studied for their nonlinear optical and optical limiting applications. Moreover, intramolecular photoinduced charge-separation and charge-recombination processes in a fused C60–TTF–C60 dumbbell triad which was designed to be soluble in organic solvents were investigated by time-resolved absorption and fluorescence techniques. Appreciable interaction between the C60 moiety and TTF moiety in the ground state was suggested by steady-state absorption spectra and the fluorescence spectra showed considerable interaction in the singlet excited state. The nanosecond transient absorption spectra ndisplayed the formation of the charge-separated radical pair C60–TTF˙+–C60˙−, characterized by a lifetime of ca. 20 ns in benzonitrile.

New versatile building blocks in tetrathiafulvalene (TTF) chemistry: 2,3-bis(bromomethyl) and tetrakis(bromomethyl)TTFs

Efficient syntheses of novel 2,3-bis(bromomethyl)TTF derivatives 1 and tetrakis(bromomethyl)TTF 2, prone to generate corresponding 2,3-dimethylene[2H]-TTF 3 and tetramethylene[4H]-TTF 4 respectively, are reported.

Novel [60]fullerene–TTF cyclohexene fused polyadducts: unprecedented tri- and tetra-Diels–Alder adducts of dimethylidene[2H]tetrathiafulvalenes with C60☆

Abstract The title compounds, which are formed in very low yields by treating 2,3-bis(bromomethyl)tetrathiafulvalenes with naked iodide in the presence of C 60 , can be obtained in much higher yields by successive similar treatments of the major adducts produced at each step. The electrochemical properties of the unprecedented tri- and tetra-TTF/C 60 assemblies are also presented.

The dumbbell bis Diels–Alder adduct between tetramethylidene[4H]tetrathiafulvalene and two C60

Abstract Dumbbell C 60 –TTF–C 60 was synthesized by a double cycloaddition of C 60 with the unprecedented tetramethylidene[4 H ]TTF generated in situ from tetrakis (bromomethyl)TTF.

Vibrational and electronic properties of [60]fullerene—tetrathiafulvalenes (TTFs) cyclohexene fused polyads

Abstract Extended spectral investigations of several new bis-linked tetrathiafulvalenes (TTFs) to [60]fullerene were performed. From UV–Vis–NIR–IR spectra, it was stated that charge distribution on the fullerene sphere and on the TTFs substituents is distinctly disturbed after the adduct formation. A particularly strong resonant effect was observed in the infrared spectra of the one of double-substituted fullerene molecules.

Photoinduced electron transfer processes of a fused C60–TTF–C60 dumbbell triad

Intramolecular photoinduced charge-separation and charge-recombination processes in a fused C60–TTF–C60 dumbbell triad molecule, which has been designed to be soluble in organic solvents thanks to the substitution of C60 with polyalcoxy ester groups, have been investigated in various solvents by time-resolved absorption and fluorescence techniques. Appreciable interaction between the C60-moiety and TTF-moiety in the ground state has been suggested by steady-state absorption spectra. The fluorescence spectra suggest also considerable interaction in the singlet excited state. The observed short fluorescence lifetimes of C60–TTF–C60 compared with methanofullerene in toluene, THF, and benzonitrile indicate that the charge-separation takes place via the singlet excited state of the C60-moiety, producing the ion-pair (C60–TTF˙+–C60˙−), which was confirmed with picosecond transient absorption spectra. The nanosecond transient absorption spectra at 1000 nm indicate the formation of C60–TTF˙+–C60˙−, which decays with a lifetime of 20 ns as an upper limit in benzonitrile. In THF and toluene, clear transient absorption bands of C60–TTF˙+–C60˙− were not observed within nanosecond laser pulse of ca. 6 ns duration, suggesting that C60–TTF˙+–C60˙− state presents a lifetime within 10 ns. These observations were compared with the reported data for C60–TTF dyads.

SPECTRAL STUDIES OF THE BIS -LINKED TETRATHIAFULVALENES (TTFs) TO [60]FULLERENE

ABSTRACT Results of the first extended spectral investigation of the bis-linked tetrathiafulvalene donors (TTFs) to [60]fullerene are reported. From UV-VIS-NIR-IR spectra it is stated that charge distribution on C60 moiety and on TTFs attachments is disturbed after the adduct formation.This redistribution depends not only on the nature of an attached molecular group but also on the number of bounded donors. In the infrared spectra of the bis-adducts, a particularly strong resonant effect was observed.

Tetrathiafulvalene-C60 based dyads by Diels-Alder reaction of bis(methylene) [2H]TTF and C60

Abstract Monoadducts of tetrathiafulvalenc (TTF) with C60 are synthesized by [4+2] Diels-Alder cycloaddition using corresponding 2,3-bis(methylene)dihydroTTF 1. These cycloadducts 2 are spectroscopically characterized and electrochemically studied.

New Tetrathiafulvalene (TTF) Derivatives Linked to Various Acceptors for Advanced Materials

Molecular assemblies resulting from the linking of TTF as an electron p-donor (D or D moiety) to various p-acceptors (A or A moiety) such as [60]fullerene (1) or quinones (2) are very attractive compounds. Depending of their kind of linking, they can be the subject of intramolecular charge transfer, or they are prone to undergo an intramolecular photoinduced electron transfer. Therefore, they are very useful either as nonlinear optic (NLO) chromophores (3), or for the realization of new artificial photosynthetic systems (4) and, as well as molecular dyads (5), they can be interesting as photovoltaic chromophores. Here are presented some preliminary results dealing with the synthesis and physicochemical properties of assemblies in which D belongs to the tetrathiafulvalene (TTF) series and A to the C60 fullerene series or to the benzoquinone series.