Photophysical studies of selected carbon-84 isomers, carbon-80 species, aqueous carbon-60 colloid, and a carbon-60-amino acid derivative

[摘要] Ground- and excited-state studies of ill-characterized fullerenes are presented. The first isomerically enriched study of C84;;s major isomers finds they differ significantly in T1 energies. Their T 1 lifetimes span two orders of magnitude, from 643 mus for D 2(IV) to 5 mus for D2d(II). The minor isomer, Cs(a), has a 127 mus T1 lifetime. Temperature-dependent decay kinetics and triplet-triplet spectra also show clear isomeric variations. These changes are remarkable, since they originate in subtle geometry differences. The C80{D5d} isomer lacks appreciable transient absorption. Its slow quenching of 1Deltag O 2 emission indicates C80{D5d};;s T1 state is within 1 kT (∼300 cm-1) of 7880 cm -1. O2-quenching experiments showed that Ho 3N C80 {Ih};;s T1 energy lies above 7880 cm-1. This incar quenches C 70 triplet states, and data suggest their T1 energies are similar. The ground-state optical behavior of n-C60 (aq) is dominated by scattering effects. This colloid;;s transient attenuation is primarily refractive. Redshifted 1Deltag O2 emission from the colloid indicates the polarizable C60 environment lowers electronic energy levels. The ;;bucky amino acid;; (BAA) shows derivatization-blueshifted transient absorption. This derivative has a T1 level substantially higher than 7880 cm-1, and is only a modest quencher of singlet oxygen.

[发布机构] Rice University