An Electron Spin Resonance Study of n-Doped TCNQ and 2:1 TCNQ Complex Salts

Complex 2:1 7,7,8,8-tetracyanoquinodimethand (TCNQ) salts of quinoline, 2-methylquinoline, 4-methylquinoline, and 7-methylquinoline were made. Their ESR spectra were observed and their magnetic susceptibilities and resistivities were determined. A new donor, 1,4-dimethyl-1,4-dihydro-s-tetrazine(DMDHT), was tried with TCNQ as acceptor. Magnetic susceptibility, resistivity, and ESR g-value measurements were made on the resulting complex. A complex of DMDHT(+)/C104(-) was made and an intense ESR singlet was observed. The ESR absorption of doped TCNQ was relatively constant from 350K to 100K. A possible explanation for this observed behavior is an excited state triplet 0.02 eV above the valence band of TCNQ. The lack of an observed doublet is explained with the 'almost-localized' electron model. As ESR kinetic study of the high temperature decomposition of TCNQ indicated more than one species resulting from decomposition. (Modified author abstract)