Activating Multistep Charge-Transfer Processes in Fullerene−Subphthalocyanine−Ferrocene Molecular Hybrids as a Function of π−π Orbital Overlap

Abstract

We have synthesized two different fullerene-subphthalocyanine-ferrocene conjugates. The molecules were designed so that the ferrocene unit is linked at the subphthalocyanine axial position through a phenoxy spacer while the C(60) is rigidly held close to the concave face of the macrocycle via a 3-fold C(3)-symmetrical anchoring. The Bingel trisaddition reaction leading to the final products proceeded with very high regioselectivities and full diastereoselectivity. The only difference between both systems is the length of the triple tether employed, which finely regulates the regioselectivity of the trisaddition reaction and the distance between the subphthalocyanine and the C(60) complementary π-π surfaces. Thus, when the tether is connected to the subphthalocyanine through a direct C-C bond, a short π-π distance of 3.25-3.30 Å was calculated. In contrast, when it is connected through a slightly longer C-O-C bond, the distance increases to 3.5-3.6 Å. This π-π distance has a strong influence on the ground-state electronic interactions between the subphthalocyanine and the C(60), as determined from electronic absorption and cyclic voltammetry measurements. In addition, fluorescence and time-resolved transient absorption experiments demonstrated that different mechanisms operate in the two systems after photoexcitation. Despite the similar HOMO-LUMO gaps, only when the two complementary π-π surfaces of the subphthalocyanine and the C(60) are held at a close distance, therefore showing a high degree of orbital overlap, is a multistep electron transfer process triggered, ultimately leading to the long-lived, spatially separated C(60) radical anion and ferrocenium radical cation pair. A full account of the synthesis, characterization, and studies of the ground- and excited-state electronic interactions occurring in these conjugates, as well as in their reference C(60)-subphthalocyanine and subphthalocyanine-ferrocene dyads, is presented in this article.

Effect of Spacer Connecting the Secondary Electron Donor Phenothiazine in Subphthalocyanine–Fullerene Conjugates in Promoting Electron Transfer Followed by Hole Shift Process

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Effect of Peripheral Substitution on the Performance of Subphthalocyanines in DSSCs

“…In recent years, research based on subphthalocyanines (SubPcs) has attracted great attention owing to their fundamental scientific importance and utility in a wide range of applications in fields such as nonlinear optics, OLEDs, photodynamic therapy, and photo‐electroactive systems . They have received considerable interest as an alternative active layer component in photovoltaic devices due to their strong absorption in the visible region (500–700 nm), low oxidation potential, and high electron mobility .…”

Theoretical investigation on icosahedral C60(FeCp)12: A hybrid of C60and ferrocene

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