Paramagnetic Molecular Centers in γ-Irradiated Precipitates in the System${\rm AlCl}_{3}-{\rm DL}\text{-}\alpha \text{-Valine}-{\rm NaOH}$

Formation and stability of paramagnetic molecular centers were studied in${\rm AlCl}_{3}-{\rm NaOH}-{\rm DL}\text{-}\alpha \text{-valine}$ by ESR spectroscopy. In${\rm Al}_{3}({\rm OH})_{9}(\text{valine})_{1}\times 3{\rm H}_{2}{\rm O}$ γ-irradiated at room temperature the valine radical$ \smallmatrix\format\c\kern.8em&\c\kern.8em&\c\kern.8em&\c\kern.8em&\c\kern.8em&\c\kern.8em&\c\\ & {\rm CH}_{3} & & & {\rm NH}_{2} & & \\ & \backslash & **??** & **??** &| & & \\ & & {\rm \dot{C}} & - & {\rm C} & - & {\rm COOH} \\ & \diagup & **??** & **??** &| & & \\ & {\rm CH}_{3} & & & {\rm H} & & \\ & & & & & & \\ & & & & ({\rm I}) & &\endsmallmatrix $ was detected. The radical was formed by abstraction of a hydrogen atom from the valine molecule coupled to the aluminum hydroxide matrix. Stability of the radical depended critically on structural properties of the aluminum hydroxide matrix. In aluminum hydroxide with the ratio (Al)/(Valine) = 20, either no paramagnetic species were detected (irradiation in air) or a singlet at g = 2.008 of 1.8 mT linewidth was detected (irradiation in vacuum) at room temperature. Primary paramagnetic species (γ irradiation at 77 K) in${\rm Al}_{3}({\rm OH})_{9}({\rm Val})_{1}\times 3{\rm H}_{2}{\rm O}$ are chloride paramagnetic centers and the primary neutral valine radical$ \smallmatrix\format\c\kern.8em&\c\kern.8em&\c\kern.8em&\c\kern.8em&\c\\ & {\rm CH}_{3} & & & \\ & \backslash & **??** & & \\ & & {\rm CH} & - & {\rm \dot{C}}{\rm HCOOH}. \\ & \diagup & **??** & & \\ & {\rm CH}_{3} & & & \\ & & & & \\ & & & ({\rm II}) & \endsmallmatrix $ It was formed by abstraction of the NH₂ group from the valine molecule. With warming, this radical was not transformed to the radical (I).