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

The complex salt Delta-alpha-[Co(R,R-picchxnMe(2))(S-phe)](ClO4)(2). H2O, w here R,R-picchxnMe(2) = N,N'-dimethyl-N,N'-di(2-picolyl)-1R,2R-diaminocyclo hexane and S-phe is the monovalent anion of S-phenylalanine, has been prepa red and its structure determined by single-crystal X-ray methods. Delta-alp ha-[Co(R,R-picchxnMe(2))(S-phe)](ClO2)(4). H2O is orthorhombic, space group P2(1)2(1)2(1), with a = 10.208(1), b = 16.804(1), c = 19.194(3)Angstrom, V = 3292.5 Angstrom(3), Z = 4, D-c = 1.542 and D-m = 1.49 Mgm(-3). The struc ture was refined to R = 0.046 for 3554 independent reflections with I > 2 s igma(I). As is the case with the R-phe analogue, the phenyl ring of the coo rdinated aminoacidate is not in the extended conformation, but lies adjacen t to one of the pyridyl rings of the coordinated tetradentate. The attracti ve intramorecular pi-pi interaction which stabilises this conformation is a nalogous to that which serves to stabilise the stacking of parallel base pa irs in DNA.