All‐Fullerene Electron Donor–Acceptor Conjugates

The synthesis and characterization of a covalent all‐fullerene C₆₀‐Lu₃N@I_h‐C₈₀ electron donor–acceptor conjugate has been realized by sequential 1,3‐dipolar cycloaddition reactions of azomethine ylides on Lu₃N@I_h‐C₈₀ and C₆₀. To the best of our knowledge, this is the first time that two fullerenes behaving as both electron donor (Lu₃N@I_h‐C₈₀) and acceptor (C₆₀) are forming an electroactive dumbbell. DFT calculations reveal up to 16 diastereomeric pairs, that is, 8 with syn and 8 with anti orientation, with the anti‐RSSS isomer being the most stable. Spectroelectrochemical absorption and femtosecond transient absorption experiments support the notion that a C₆₀^??‐Lu₃N@I_h‐C₈₀^?+ charge‐separated state is formed. Spin conversion from the charge‐separated singlet state C₆₀^??‐Lu₃N@I_h‐C₈₀^?+ into the corresponding triplet state is facilitated by the heavy‐atom effect stemming from the Lu₃N‐cluster, which, in turn, slows down the charge recombination by one order of magnitude.     

Dibenzoarsepins: Planarization of 8π‐Electron System in the Lowest Singlet Excited State

Dibenzo[b,f]arsepins possessing severely distorted cores compared to those of other heteropins were synthesized. These derivatives exhibited dual photoluminescence in the green‐to‐red region (500–700 nm) and the near‐ultraviolet region (<380 nm), which could be attributed to the planarization of the arsepin core in the lowest singlet excited (S₁) state. The computational approach for the assessment of the aromatic indices revealed that the dibenzoarsepins studied show aromaticity (8π system) in the S₁ states in line with Baird's rule. The lone pair electrons of the arsenic atoms play a crucial role in the aromaticity in the S₁ states.