Giant analogues of tetrathiafulvalene in Langmuir and Langmuir–Blodgett films

Abstract

The behaviour of new giant tetrathiafulvalene (TTF) analogues has been studied at the gas/water interface and in Langmuir-Blodgett films. These compounds, denoted G-TTFC,, have a dihydro-TTF core which bears two conjugated side-arms with various alkyl chains (from methyl to octyl). Langmuir films of these compounds are quite stable versus time and are characterized by a collapse pressure that increases as the length of the alkyl chains decreases. The ability of these compounds to form Langmuir films should then be due to their extended TTF core. Except for G-TTFC1, transfer of the monolayer onto a solid substrate is easily done at low surface pressure. Doping of the LB films by iodine vapours changes their spectroscopic (EPR, electronic and vibrational) behaviour and leads to rather poor conducting films. Conductivity of G-TTFC4 films ( 0 R T Z 4 x S cm-') is two orders of magnitude lower than for G-TTFC2 ( o R T Z 4 x S cm-'), showing the influence of the molecular packing on the electrical properties of such films. Different results are obtained upon mixing these G-TTFC, compounds with pentadecyltetracyanoquinodimethane (C,,TCNQ) in various proportions, which gives rise to charge transfer complexes of adjustable stoichiometry. It is shown that these extended z-donor molecules give new insights on the redox processes that can lead to conducting films.

Core carbo‐mer of an Extended Tetrathiafulvalene: Redox‐Controlled Reversible Conversion to a carbo‐Benzenic Dication

“…This transformation was however found to not proceed cleanly, producing inseparable decarboxylation side products. Alternatively, however, 11 b could be obtained, in 42 % yield, by Wittig reaction of the [6]pericyclynedione 9 with the ylide of 10 b , prepared following a reported procedure (Scheme ) . Treatment of 11 b with SnCl 2 in DCM afforded the carbo ‐exTTF 8 b in 44 % yield as a dark crystalline powder giving green solutions in organic solvents.…”

Highly Functionalized Tetrathiafulvalenes: Riding along the Synthetic Trail from Electrophilic Alkynes

“…In the sulfur series, the preparation of 9 has been generalized to other diesters (E = CO 2 R) of acetylenedicarboxylic acid with long alkyl chain alcohols. This gave TTFs with suitable amphiphilic properties for Langmuir−Blodgett film formation 9 …”

“…A wide variety of R substituents are available for W and P , so that one may easily increase the solubility or the π-donating ability (or both) of the target molecules 115 − 122 . We can even prepare amphiphilic derivatives of 119 designed for LB films from a phosphonium salt 9 bearing long carboalkoxy chains (R = CO 2 C 8 H 17 ), Chart 13 …”

“…This gave TTFs with suitable amphiphilic properties for Langmuir-Blodgett film formation. 47 When DMAD is reacted with Bu 3 P-CS 2 at room temperature without any trapping of the ylid 10 first produced (Scheme 10), a further reaction occurs which gives rise to another ylid 11 whose formation is explained as resulting from a [2+2] cycloaddition of a second molecule of DMAD to the first ylid, followed by electrocyclic ring opening. 48 Carrying on their studies, Aitken et al 49 suggested a modification of the mechanism initially proposed (Scheme 11a) 41 for the direct formation of the TTF core when DMAD or methyl propiolate is reacted with Bu 3 P-CS 2 (Scheme 11b).…”

“…We can even prepare amphiphilic derivatives of 119 designed for LB films from a phosphonium salt 9 bearing long carboalkoxy chains (R ) CO 2 C 8 H 17 ), Chart 13. 47 Although the most powerful nucleophilic species are the phosphonate anions P, in all cases except for the tris(formyl) derivative 123 the easier to handle P-ylids W are reactive enough to achieve the required polyolefinations of the conjugated aldehydes. These reactions proceed in quite good yields (50-90%) if one considers that up to four olefinations are achieved in one step.…”