Near-Unity Triplet Generation Promoted via Spiro-Conjugation

An intersystem crossing (ISC) rate constant of 1.0x10(11) s(-1) was previously registered with a spiro-bis-benzophenone scaffold. Triplet generation efficiency could be further enhanced by stabilizing the spiro-charge-transfer (CT) state and rationally designing spiro-compounds (SCTs) that consist of electron-rich diphenyl ether as the spiro-CT donor and electron-deficient dinaphthyl ketone as the spiro-CT acceptor. Through fine-tuning of the energy level between the CT and high energy triplet states, near-unity triplet generation quantum yield was achieved and the underlying ISC mechanism is revealed by using ultrafast spectroscopy and quantum chemical calculations. Potential triplet sensitizing application was demonstrated in SCTs. Our findings suggest that a spiro-bichromophoric molecular system with an enhanced spiro-charge transfer warrants efficient triplet generation and is a powerful strategy of heavy-atom-free triplet sensitizers with predictable ISC properties.

Automated summary

The study focuses on enhancing triplet generation efficiency and uncovering the mechanism of intersystem crossing by designing spiro-compounds. By fine-tuning the energy levels between spiro-charge transfer and high energy states, near-unity triplet generation quantum yield was achieved.