PHOTOPHYSICAL PROPERTIES OF NITROGEN SUBSTITUTED FULLERENES

By arc vaporization of graphite in the presence of pyrrole vapor, prod ucts are formed containing nitrogen atoms substituted in the C-60 and C-70 cage accompanied by other carbonaceous clusters. Fractions which are rich in nitrogen were isolated by high performance liquid chromato graphy using a gel permeation column and characterized by optical abso rption, fluorescence, transient absorption, and time-resolved fluoresc ence measurements. Fluorescence spectra are attributed to intrinsic ex citation in the nitrogen doped species as well as to separated charges in the fragmented fullerenes. Transient absorption spectra at time de lays of 20 ns following excitation of the ground state molecules are a ttributed to delayed fluoresence. The average fluorescence lifetime of these molecules were determined to be 4 ns. These data, together with earlier studies from this laboratory of the mass spectra, absorption and fluorescence of fractions isolated by column chromatography, add f urther credence to the existence of stable nitrogen doped fullerenes.