Photoinduced Electron Transfer in a Zinc Phthalocyanine–Fullerene Conjugate Connected by a Long Flexible Spacer

Abstract

A hexadodecyl‐substituted zinc phthalocyanine covalently linked through a flexible spacer to a fullerene—ZnPc−C60—has been investigated regarding electron transfer from the photoexcited, electron‐donating ZnPc to the electron‐accepting C60. While ground‐state interactions between electron donor and acceptor within ZnPc−C60 could not be detected via steady‐state absorption spectroscopy, clear proof for excited‐state interactions came from steady‐state fluorescence spectroscopy. To this end, the fluorescence in ZnPc−C60 is strongly quenched with quantum yields in THF as low as 0.05. Insight into excited‐state electron‐transfer deactivation within ZnPc−C60 came from time‐resolved femtosecond transient absorption spectroscopy. For example, upon exclusive excitation of the phthalocyanine within the ZnPc−C60 conjugate, a set of transients evolve featuring, on the one hand, the signature of the one‐electron oxidized ZnPc radical cation and, on the other hand, of the one‐electron reduced C60 radical anion. The analysis of the corresponding dynamics in chlorobenzene resulted in lifetimes for charge‐separation and charge‐recombination of 7.4 ps and 2.2 ns, respectively.

Synergy of Electrostatic and π–π Interactions in the Realization of Nanoscale Artificial Photosynthetic Model Systems

“…Besides the ground‐state bleaching (GSB) of the Soret‐ and Q‐band absorptions, new features arise at 422, 520, and 840 nm. These bands fit the values found in the literature for the one‐electron oxidized form of ZnPcs perfectly . At a voltage of −0.2 V vs. Ag‐wire, features of the one‐electron reduced forms of 1 and 2 are discernable (Figure S40 and S41, respectively).…”

“…At a voltage of −0.2 V vs. Ag‐wire, features of the one‐electron reduced forms of 1 and 2 are discernable (Figure S40 and S41, respectively). In particular, new features at 560–580, 820, and 960–980 nm arise, accompanied by GSB, which are also found in the literature upon reduction of ZnPcs . Comparing the GSB and evolving features during the first oxidation and reduction of 1 with 2 , we exclude any participation of the pyrenes in these redox processes.…”

Synergie von elektrostatischen und π‐π‐Wechselwirkungen für die Verwirklichung von künstlichen photosynthetischen Modellsystemen auf Nano‐Ebene

“…Bei einer Spannung von −0.2 V vs. Ag‐Draht sind die Merkmale der ersten reduzierten Form von 1 und 2 erkennbar (Abbildungen S40 und S41). Im Einzelnen treten neue Merkmale bei 560–580, 820, und 960–980 nm auf, welche ebenso in der Literatur zu finden sind und von der GZB begleitet werden . Vergleicht man die GZB und die entstehenden Merkmale während der ersten Oxidation und Reduktion von 1 und 2 , kann man eine Beteiligung der Pyrene in diesen Redoxprozessen ausschließen.…”

Distance‐Dependent Electron Transfer Kinetics in Axially Connected Silicon Phthalocyanine‐Fullerene Conjugates

“…[24] That is why donor-acceptor arrangements based on porphyrin/phthalocyanine and C 60 -fullerene, represent an outstanding majority. [25][26][27][28][29][30][31][32][33] In the context of donor-acceptor design, there are few examples of covalent multimodular artificial photosynthetic systems, where electron-acceptor units are arranged in the axial positions of a suitable porphyrinoid macrocycle, thus providing molecular systems that undergo photo-induced electron transfer processes in a very efficient way. [19,[34][35][36][37][38][39][40][41][42][43][44][45] One of the most versatile building-blocks is silicon phthalocyanine (SiPc), which can be easily functionalized at axial positions through a variety of functionalities.…”