Reactions of the bis(bidentate) Schiff-bases N,N'-bis(6-alkyl-2-pyridylmethylene)ethane-1,2-diamine (where alkyl = H, Me, Pr-i) (L) with tetrakis(acetonitrile)copper(I) hexafluorophosphate and silver(I) hexafluorophosphate afforded, respectively, the double-stranded, dinuclear metal helicates [T4-(R*,R*)]-(+/-)-[M2L2](PF6)(2) (M = Cu, Ag). The helicates were characterized by H-1 and C-13 NMR spectroscopy, conductivity, microanalysis, and single-crystal X-ray structure determinations on selected compounds. Intermolecular ligand exchange and intramolecular inversion rates for the complexes were investigated by H-1 NMR spectroscopy. Reversible intermolecular ligand exchange between two differently substituted helicates followed first-order kinetics. The rate constants (k) and corresponding half-lives (t(1/2)) for ligand exchange for the dicopper(I) helicates were k = (1.6-1.8) x 10(-6) s(-1) (t(1/2) = 110-120 h) in acetone-d(6), k = 4.9 x 10(-6) s(-1) (t(1/2) = 40 h) in dichloromethane-d(2), and k > 2 x 10(-3) s(-1) (t(1/2) < 5 min) in acetonitrile-d(3). Ligand exchange for the disilver(I) helicates occurred with k > 2 x 10(-3) s(-1) (t(1/2) < 5 min). Racemization of the dicopper(I) helicate by an intramolecular mechanism was investigated by determination of the coalescence temperature for the diastereotopic isopropyl-Me groups in the appropriate complex, and Delta G(double dagger) >> 76 kJ mol(-1) was calculated for the process in acetone-d(6), nitromethane-d(3), and dichloromethane-d(2) with Delta G(double dagger) = 75 kJ mol(-1) in acetonitrile-d3. Complete anion exchange of the hexafluorophosphate salt of a dicopper(I) helicate with the enantiomerically pure Delta-(-)-tris(catecholato)arsenate(V) ([As(cat)(3)](-)) in the presence of Dabco gave the two diastereomers (R,R)-[Cu2L2]{Delta-(-)-[As(cat)(3)]}(2) and (S,S)-[Cu2L2]{Delta-(-)-[As(cat)(3)]}(2) in up to 54% diastereomeric excess, as determined by H-1 NMR spectroscopy. The diastereomerically and enantiomerically pure salt (R,R)-[Cu2L2){Delta-(-)-[As(cat)(3)]}(2) crystallized from the solution in a typical second-order asymmetric transformation. The asymmetric transformation of the dicopper(I) helicate is the first synthesis of a diastereomerically and enantiomerically pure dicopper(I) helicate containing achiral ligands.