Synthesis, optical properties and supramolecular order of π-conjugated 2,5-di(alcoxy)phenyleneethynylene oligomers

Versatile Bisethynyl[60]fulleropyrrolidine Scaffolds for Mimicking Artificial Light‐Harvesting Photoreaction Centers

“…Among the synthetic methods to functionalize C 60 , [24][25][26][27] the 1,3-dipolar cycloaddition of azomethine ylides [23,28,29] to yield [60]fulleropyrrolidines that are formed across the 6-6 junction of the fullerene core is certainly one of the most attractive route for preparing covalent conjugates for materials science. This because [60]fulleropyrrolidines are known to be very stable under both oxidative and reductive conditions, and the retrocycloaddition reaction [30,31] is essentially observed under harsh conditions (heating to reflux in o-dichlorobenzene (ODCB) in the presence of a strong dipolarophile and a Lewis acid such as Cu(OTf) 2 ).…”

“…[3] Understanding these fundamental processes has prompted chemists to engineer artificial chemical assemblies that mimic them and might provide the basis for artificial solar-energy conversion devices. [4,5] In this context, C 60 and its derivatives are optimal components to be incorporated into artificial reaction centers because of the exceptional electron-accepting properties, the low-lying level of their excited states, their small reorganization energy, and their remarkable stability under light irradiation. [6,7] In particular, their use in donor-acceptor systems for photovoltaic devices has impressively expanded.…”

“…[6,7] In particular, their use in donor-acceptor systems for photovoltaic devices has impressively expanded. [8,9] To this end, a variety of [60]fullerene derivatives linked to electron-donating units such as, among others, porphyrins, [10][11][12][13][14] tetrathiafulvalenes (TTFs), [15] ferrocene, [16] phthalocyanines, [17] oligophenylenevinylenes, [18] and transition-metal complexes [19][20][21] have been prepared. The mechanisms of photoinduced electron and energy transfer have been elucidated by means of timeresolved spectroscopic methods, thus showing a strong intramolecular quenching of the excited singlet and triplet states of C 60 through the formation of charge-separated (CS) radical ion pairs.…”

“…[22] In this context, we have now designed and synthesized a novel fullerene scaffold that features geometrical constraints that afford a hierarchical and spatial organization of the chromophores (Figure 1). In particular, by exploiting the 1,3-dipolar cycloaddition on C 60 , [23] we have prepared tetrads that bear a chromophoric antenna (an oligo(p-phenyleneethynylene) derivative, OPE) directly attached the nitrogen atom of [60]fulleropyrrolidine and two photoactive electron-donor moieties (i.e., ferrocene (Fc) and phenothiazine (PTZ)) rigidly attached to the a carbon of the same pyrrolidine ring ( Figure 1) through an acetylene spacer. A full account of the electrochemical and photophysical properties of conjugates 1-4 along with those of the corresponding reference compounds 7-10 ( Figure 2) is reported, which shows the occurrence of a charge-separated state that lives for 250 ns for molecule 4.…”

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Abstract: Fullerene-based tetrads, triads, and dyads are presented in which [60]fulleropyrrolidine synthons are linked to an oligo(p-phenyleneethynylene) antenna at the nitrogen atom and to electron-donor phenothiazine (PTZ) and/or ferrocene (Fc) moieties at the a carbon of the pyrrolidine cycle through an acetylene spacer. Cyclic voltammetry and UV/ Vis absorption spectra evidence negligible ground-state electronic interactions among the subunits.

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