Chiral metal complexes part 52. The structures of co-crystallised diastereoisomeric DNA probes showing intramolecular pi-pi interactions

The structure of Delta-alpha(1,2)-[Co(R-picpnMe(2))(S-phe)](ClO4)(2). H2O w here R-picpnMe(2) is N,N'-dimethyl-3R-methyl-1,6-di(2-pyridyl)-2, and S-phe is the S-phenylalaninate anion has been determined to be orthorhombic, spa ce group P2(1)2(1)2(1), with a = 9.959(4), b = 15.919(7), c = 19.59(3)Angst rom, D-c = 1.515 Mgm(-3) and Z = 4. The structure was refined by least-squa res methods to R = 0.050 for 2328 independent reflections with I > 2 alpha( I) for diffractometer data collected at 293 K. The cobalt atom has the expe cted octahedral coordination with the N4 tetradentate adopting a-a topology and with the phenylalaninate ligand completing the coordination sphere. Tw o geometric isomers possible for the asymmetric complex, alpha(1) and alpha (2) (depending upon the relative mode of coordination of the aminoacidate r elative to the Irans orientation of the methyl group of the tetradentate), are observed to co-crystallise in a 1 : 1 ratio. In these species, the phen yl ring is weakly bonded to one of the pyridyl rings of the tetradentate, a s has been found in a number of congeners. The R-phe analogue has also been synthesised. The perchlorate salt contains both possible isomers. NMR stud ies indicate that the pi-pi interaction observed in the solid state for Del ta-alpha(1,2)-[Co(R-picpnMe(2))(S-phe)](2+) is preserved in solution.