Photophysical characteristics of C60-threoninen (n = 1–4) complexes: DFT study.

[Display omitted] • Modifying C 60 using threonine decreases the excitation degeneration and redshifts low-lying and excited states. • Calculated ISC rate constants for S 1 → T 1 transitions indicate a fairly effective process of saturation the triplet state. • Calculated IC rate constants for S 1 → S 0 two orders of magnitude less than for ISC marking that IC cannot compete with ISC. • The main source of the IC process is the anharmonic C-H vibrations of hydrogens bound to fullerene. DFT calculations showed that disruption of the π network of the fullerene due to the addition of up to four threonines does not affect the efficiency of saturation of the T 1 state by intersystem crossing compared to pure C 60. Internal conversion from S 1 to the ground state does not compete with intersystem crossing to T 1 state. The regulating of C-H vibrations associated with hydrogens bound to fullerene may govern the quantum yield of the triplet state saturation. Resulting phosphorescence lifetimes high enough to guarantee a high probability of quenching the triplet state by molecular oxygen. [ABSTRACT FROM AUTHOR]