ESR Study of an Interstitially Trapped Copper Ion in a Crystal of L-Alanine

It has been found that copper ions are trapped interstitially in crystals of L-alanine grown from a solution containing copper chloride. The ESR absorption, which was studied at 9 and 23 GHz, showed a superhyperfine structure from a single 14N, suggesting that the Cu2+ is bonded to a single nitrogen atom. This result is in contrast to the case of copper chelate compounds of amino acids in which the Cu2+ is bonded to a pair of nitrogen atoms, in addition to a pair of oxygen atoms. The g tensor, the hfs tensor, and the 14N super-hfs tensor were determined, and the possible position of the Cu2+ ion in the crystal was discussed. The tensors showed no evidence of temperature dependence between room temperature and 4.2°K.