A mixed metal complex of a compound of Formula I, or a salt thereof, wherein the mixed metals comprise a Group III-XII transition metal and a Group II metal: wherein X, R1, R2, R3, and R4 are as defined herein, is produced in a one step crystallization from a solution of the Group III-XII transition metal, the Group II metal, and a compound of Formula I. Methods for treatment of a pathological condition in a patient, for example, a pathological condition caused by the presence of oxygen-derived free radicals, comprise administering the mixed metal complex to the patient.