Chiral metal complexes. 50.* X-ray structure of the DNA probe Δ-α-[N,N′-dimethyl-N,N′-di(2-picolyl)-1R,2R- diaminocyclohexane]-[S-phenylalaninato(1-)]cobalt(III) perchlorate hydrate

The complex salt Δ-α-[Co(R,R-picchxnMe₂)(S-phe)](ClO₄) ₂· H₂O, where R,R-picchxnMe₂ = N,N′-dimethyl-N,N′-di(2-picolyl)-1R,2R-diaminocyclohexane and S-phe is the monovalent anion of S-phenylalanine, has been prepared and its structure determined by single-crystal X-ray methods. Δ-α-[Co(R,R-picchxn Me₂)(S-phe)](ClO₄)₂ · H₂O is orthorhombic, space group P2₁2₁2₁ with a= 10.208(1), b=16.804(1), c= 19.194(3)Å, V= 3292.5ų, Z = 4, D_c = 1.542 and D_m= 1.49Mgm^-3. The structure was refined to R = 0.046 for 3554 independent reflections with I > 2σ(I). As is the case with the R-phe analogue, the phenyl ring of the coordinated aminoacidate is not in the extended conformation, but lies adjacent to one of the pyridyl rings of the coordinated tetradentate. The attractive intramolecular π-π interaction which stabilises this conformation is analogous to that which serves to stabilise the stacking of parallel base pairs in DNA.