Weak intramolecular interactions in perchlorate salts of Λ-β₁-[Co(R,R-picchxn)(R-aa)]₂⁺ [picchxn=N,N′-di(2-picolyl)-1,2-diaminocyclohexane; AA=phenylalaninato(1−), tyrosinato(1−)] and their diastereoisomeric equilibration in solution