VARIABLE-TEMPERATURE EPR STUDIES OF ILLINOIS NO 6 COAL TREATED WITH DONOR AND ACCEPTOR MOLECULES

Variable-temperature EPR studies of Illinois No. 6 coal, its pyridine extract, and samples of each after treatment with known donor and acce ptor molecules are reported. The purpose of the study was to explore t he origin of the EPR signals near g = 2 and to elucidate the nature of noncovalently bonded interactions in coal. Curie Law behavior is exhi bited for each sample, indicating that the EPR signals are dominated b y doublet state species. No evidence for thermally accessible, low-lyi ng triplet states, such as those found in some charge-transfer complex es, was found. Infrared spectroscopy suggests, however, that electron transfer from the coal does occur after treatment with electron accept ers such as TCNQ and TCNE. EPR studies of the Illinois No. 6 coal samp les after treatment with the known electron donor TTF revealed the for mation of the TTF radical cation.