Cu(catechol)2 is a low molecular weight, square-planar cupric complex with four oxygen donor atoms. Dilution of the sample from 3 to 0.4 mM has no effect on the line position and little effect on the lineshape of the CW-EPR spectrum, whereas easily detectable changes in the saturation-recovery signals are observed. Little changes in the saturation-recovery signals are observed upon dilution of the sample from 0.4 to 0.1 mM. The changes above 0.4 mM are interpreted in terms of dipole-dipole interactions between Cu(catechol)2 copper complexes. The results are relevant for the determination of the distance between two similar paramagnetic copper complexes. The saturation-recovery signals are best fit to at least double exponentials. The prefactor of the exponential function for the longer relaxation time, T1L, increases, and the prefactor for the shorter time, T1S, decreases as the pump width varies from 1 fs to 1 ms. The dependence of the relaxation time, T1L, on magnetic field at 16.7 K varies by less than 20% from the g region to the g region with little MI dependence in either direction.
Showing the most recent 10 out of 368 publications
