A novel, highly stable photochromic dyad 3 based on a perylene bisimide (PBI) fluorophore and a diarylethene (DAE) photochrome was synthesized and the optical and photophysical properties of this dyad were studied in detail by steady-state and time-resolved ultrafast spectroscopy. This photochromic dyad can be switched reversibly by UV-light irradiation of its ring-open form 3o leading to the ring-closed form 3c, and back reaction of 3c to 3o by irradiation with visible light. Solvent-dependent fluorescence studies revealed that the emission of ring-closed form 3c is drastically quenched in solvents of medium (e.g., chloroform) to high (e.g., acetone) polarities, while the emission of the ringopen form 3o is appreciably quenched only in highly polar solvents like DMF. The strong fluorescence quenching of 3c is attributed to a photoinduced electron- transfer (PET) process from the excited PBI unit to ring-closed DAE moiety, as this process is thermodynamically highly favorable with a Gibbs free energy value of 0.34 eV in dichloromethane. The electron-transfer mechanism for the fluorescence quenching of ring-closed 3c is substantiated by ultrafast transient measurements in dichloromethane and acetone, revealing stabilization of charge-separated states of 3c in these solvents. Our results reported here show that the new photochromic dyad 3 has potential for nondestructive read-out in write/ read/erase fluorescent memory systems
Non-destructive Photoluminescence Read-out by Intramolecular Electron Transfer in a Perylene Bisimide-Diarylethene Dyad
NATALI, Mirco;CHIORBOLI, Claudio;SCANDOLA, Franco;
2012
Abstract
A novel, highly stable photochromic dyad 3 based on a perylene bisimide (PBI) fluorophore and a diarylethene (DAE) photochrome was synthesized and the optical and photophysical properties of this dyad were studied in detail by steady-state and time-resolved ultrafast spectroscopy. This photochromic dyad can be switched reversibly by UV-light irradiation of its ring-open form 3o leading to the ring-closed form 3c, and back reaction of 3c to 3o by irradiation with visible light. Solvent-dependent fluorescence studies revealed that the emission of ring-closed form 3c is drastically quenched in solvents of medium (e.g., chloroform) to high (e.g., acetone) polarities, while the emission of the ringopen form 3o is appreciably quenched only in highly polar solvents like DMF. The strong fluorescence quenching of 3c is attributed to a photoinduced electron- transfer (PET) process from the excited PBI unit to ring-closed DAE moiety, as this process is thermodynamically highly favorable with a Gibbs free energy value of 0.34 eV in dichloromethane. The electron-transfer mechanism for the fluorescence quenching of ring-closed 3c is substantiated by ultrafast transient measurements in dichloromethane and acetone, revealing stabilization of charge-separated states of 3c in these solvents. Our results reported here show that the new photochromic dyad 3 has potential for nondestructive read-out in write/ read/erase fluorescent memory systemsI documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
