Excited State Photophysical Properties of Curcumin and its Methoxy Derivative in Benzene

Atanu Barik, K. Indira Priyadarsini and Hari Mohan*

Radiation Chemistry and Chemical Dynamics Division, Bhabha Atomic Research Centre, Trombay, Mumbai- 400 085 (India)

Absorption and fluorescence spectra of curcumin (C) and its methoxy derivative (TMC) were recorded in benzene. The fluorescence quantum yields were determined using couamarin-153 as standard. On 355 nm picosecond (35 ps) laser excitation, the singlet-singlet absorption spectra of curcumin and TMC showed absorption band at 555 and 550 nm respectively. The triplet excited states were populated by intersystem crossing from the singlet excited states in benzene. The triplets exhibit a broad absorption band in 500-700 nm region. The triplet-triplet absorption spectra in benzene were also recorded by energy transfer from pulse radiolytically generated biphenyl triplet. The rates of intersystem crossing, non-radiative decay, extinction coefficients of the triplet excited states, their half-lives have been reported. The studies suggest that both curcumin and its methoxy derivative show similar photophysical properties in the excited state.

Curcumin, TMC; Photophysical Properties; Laser Flash Photolysis; Pulse; Radiolysis