CHIRAL METAL COMPLEXES. PART 52.* THE STRUCTURES OF CO-CRYSTALLISED DIASTEREOISOMERIC DNA PROBES SHOWING INTRAMOLECULAR #pi#-#pi# INTERACTIONS

摘要

The structure of A-or t,2-(Co(R-picpnMe_2)(S-phe))(C1O_4)_2 centre dot H_2O where R-picpnMe_2 is N,N' dimethyl-3R-methyl-l ,6-di(2-pyridyl)-2,5-diazahexane and S-phe is the S-phenylalaninate anion has been determined to be orthorhombic, space group P2_12_12_1, with a=9.959(4), b= 15.919(7), c= 19.59(3)A, D_c= l.5l5Mgm~(-3) and Z=4. The structure was refined by least-squares methods to R = 0.050 for 2328 independent reflections with I> 2~I) for diffractometer data collected at 293 K. The cobalt atom has the expected octahedral coordination with the N4 tetradentate adopting #DELTA#-#alpha# topology and with the phenylalaninate ligand completing the coordination sphere. Two geometric isomers possible for the asymmetric complex, #alpha#1 and #alpha#2 (depending upon the relative mode of coordination of the aminoacidate relative to the trans orientation of the methyl group of the tetradentate), are observed to co-crystallise in a 1 to be 1 ratio. In these species, the phenyl ring is weakly bonded to one of the pyridyl rings of the tetradentate, as has been found in a number of congeners. The R-phe analogue has also been synthesised. The per-chlorate salt contains both possible isomers. NMR studies indicate that the #pi#-#pi# interaction observed in the solid state for #DELTA#-#alpha#_(1,2)-(Co(R-picpnMe_2)(S-phe))~(2+) is preserved in solution.