A Diaminoterephthalate–C60 Dyad: A New Material for Optoelectronic Applications

Abstract

Diaminoterephthalate was used for the first time as a chromophore in a dyad with [60]fullerene. The synthesis was accomplished from the benzyl methyl diester by hydrogenolytic cleavage of the benzyl group, re-esterification with a benzyl alcohol with protected formyl function, deprotection of the latter and final 1,3-dipolar cycloaddition with C 60 and sarcosine via the azomethine ylide.In order to mimic natural photosynthesis and to understand fundamental photoinduced electron and energy transfer processes, many photosynthetic models have been constructed and investigated in the past few decades. 1 Among the energy-and electron-accepting moieties, fullerene (C 60 ) has become the most promising one due to its unique physical and chemical properties. For example it can be easily ligated to dyes and other larger molecular entities by cycloaddition reactions. Several dye-fullerene conjugates, so called dyads, have been prepared in the past years. 2 We have recently prepared and investigated a related compound, a triad consisting of a carotenoid as electrondonating, C 60 as electron-accepting moieties, and a porphyrin derivative as the central chromophore. 3 The multistep, low-yielding synthesis of this compound was quite a challenge, 4 which is mainly attributed to the construction and two-fold unsymmetric derivatization of the porphyrin core. Therefore, a more straightforward synthetic route to a dyefullerene conjugate was pursued and a diaminoterephthalate derivative was selected as the chromophore. We have recently introduced diaminoterephthalates as colored molecular scaffolds bearing up to four sites for orthogonal functionalization. 5 Furthermore, diaminoterephthalates show promising fluorescence properties, 6 which can bewith prerequisite functionalization -switched on by a chemical reaction and can therefore be used as 'turn-on' probes for biochemical applications. 7 In particular, we suggested dyad 6 as a distinguished molecular model for spectroscopic investigations of electron transfer processes on a femtosecond timescale. Prior to synthesis, computational studies on compound 6 were performed, which allowed us to attribute the absorption edge to a predominant pure transition between the highest occupied and the lowest unoccupied molecular orbitals, and to identify two distinct channels for electron transfer reactions in the dyad, namely one involving an indirect exciton and one attributed to a phonon-mediated mechanism driving an initial excitation of direct excitonic character. 8 We now report herein the optimized synthesis of compound 6, which is the first example of a diaminoterephthalate as chromophore in dyads for optoelectronic applications.

Structural Flexibility Slows Down Charge Transfers in Diaminoterephthalate-C60 Dyads

“…After cycloaddition, the initially formed species decarboxylates. The preparation of the short dyad DAT-L 1 -MPC 60 ( 1 ) was accomplished earlier by us from a mixed DAT methyl benzyl ester and was already published . The synthesis of the long dyad DAT-L 2 -MPC 60 ( 2 ) is reported in section 1 of the Supporting Information (SI) as well as additional details and NMR spectra.…”

Quantum modeling of ultrafast photoinduced charge separation

“…Porphyrins are by far the most common building blocks for electron donors and molecular sensitizers in artificial photosynth etic models [50]. However, other different chromophores, such as diaminoterephthalate, have been also proposed as molecular scaffolds for easier functionalization [51,52]. In particular, non-bonded dyads made of porphyrins and fullerenes were used to assess constrained DFT and TDDFT accuracy in describing excitation energies [53][54][55].…”

Diaminoterephthalate–α-lipoic acid conjugates with fluorinated residues

“…The chromophore, which is accessed from succinyl succinates and primary amines [6–7], can be regarded as a molecular scaffold [8], which can be orthogonally equipped with different functional units [9] by simple transformations. Thus, different applications in materials science [10] and life sciences [11–12] can be addressed by tailored functional DATs. As an example for an application in biochemistry, Fig.…”