Experimental and theoretical structural parameters of the glycine (C) over dot H2-NH2 radical

An experimental and theoretical analysis is reported for the geometrical structure and unpaired spin density of the CH2-NH2 radical produced in a gamma-irradiated single crystal of glycine at room temperature. Geometrical parameters obtained by using the two-center dipole approximation indicate that the radical is not planar at the carbon site. Ab initio calculations were performed in order to estimate the structural parameters and unpaired spin density of the radical (C) over dot H-2-NH2 in an anisotropic matrix. A good agreement was obtained between the calculated and observed values. Using the Saturation Recovery (SR) method in the temperature range 190-290 K we have obtained a set of spin lattice relaxation times, attributed to the reorientation of the amino group of the NH3-(C) over dot H-COO- radical, simultaneously produced in gamma-irradiated solid glycine with (C) over dot H-2-COO- and (C) over dot H-2-NH2 radicals. (C) 1999 Elsevier Science B.V. All rights reserved.