Bidirectional Electron Transfer Capability in Phthalocyanine–Sc₃N@<i>I</i>_<i>h</i>–C₈₀ Complexes

To activate oxidative and/or reductive electron transfer reactions, <i>N</i>-pyridyl-substituted Sc₃N@<i>I</i>_<i>h</i>–C₈₀ (<b>4</b>) and C₆₀ (<b>3</b>) fulleropyrrolidines have been prepared and axially coordinated to electron-rich (<b>1</b>) or electron-deficient (<b>2</b>) Zn­(II)­phthalocyanines (Zn­(II)­Pcs) through zinc-pyridyl, metal–ligand coordination affording a full-fledged family of electron donor–acceptor ensembles. An arsenal of photophysical assays as they were carried out with, for example, <b>1</b>/<b>4</b> and <b>2</b>/<b>4</b> show unambiguously that a Zn­(II)­Pc-to-Sc₃N@<i>I</i>_<i>h</i>–C₈₀ photoinduced electron transfer takes place in the former ensemble, whereas a Sc₃N@<i>I</i>_<i>h</i>–C₈₀-to-Zn­(II)­Pc electron transfer occurs in the latter ensemble. To the best of our knowledge, this is the first time that a fullerene-based molecular building block shows an electron transfer dichotomy, namely acting both as electron-acceptor or electron-donor, and its outcome is simply governed by the electronic nature of its counterpart. In light of the latter, the present work, which involves the use of Sc₃N@<i>I</i>_<i>h</i>–C₈₀, one of the most abundant and easy-to-purify endohedral metallofullerenes, is, on one hand, a paradigmatic change and, on the other hand, an important milestone <i>en-route</i> toward the construction of easy-to-prepare molecular materials featuring switchable electron transfer reactivity

Energy Level Tuning of Non-Fullerene Acceptors in Organic Solar Cells

The use of non-fullerene acceptors in organic photovoltaic (OPV) devices could lead to enhanced efficiencies due to increased open-circuit voltage (<i>V</i>_OC) and improved absorption of solar light. Here we systematically investigate planar heterojunction devices comprising peripherally substituted subphthalocyanines as acceptors and correlate the device performance with the heterojunction energetics. As a result of a balance between <i>V</i>_OC and the photocurrent, tuning of the interface energy gap is necessary to optimize the power conversion efficiency in these devices. In addition, we explore the role of the charge transport layers in the device architecture. It is found that non-fullerene acceptors require adjusted buffer layers with aligned electron transport levels to enable efficient charge extraction, while the insertion of an exciton-blocking layer at the anode interface further boosts photocurrent generation. These adjustments result in a planar-heterojunction OPV device with an efficiency of 6.9% and a <i>V</i>_OC above 1 V

Self-Assembly, Host–Guest Chemistry, and Photophysical Properties of Subphthalocyanine-Based Metallosupramolecular Capsules

Four new subphthalocyanine-based capsules have been synthesized and characterized. These supramolecular systems have been successfully employed for the encapsulation of fullerenes and probed by a wide range of characterization methods, including NMR, UV–vis and fluorescence spectroscopy, electrospray ionization mass spectrometry, and electrochemistry. Furthermore, the binding constants of the host guest complexes were estimated. Finally, the photophysical properties revealed that the subphthalocyanines undergo a transduction of singlet excited-state energy to the fullerene inside the cavity upon photoexcitation