Five new 1,4,7-triazacyclononane-derived compounds, sodium 3-(4,7-dimethyl-1,4,7-triazacyclononan-1-yl) propionate (Na[L-Me2R']) as well as the enantiopure derivatives (S)-1-(2-methylbutyl)-4,7-dimethyl-1,4,7-triazacyclononane (S-L-Me2R' ), SS-trans-2,5,8-trimethyl-2,5,8-triazabicyclo[7.4.0(1,9)]tridecane (SS-L-BMe3), (S)-1-(2-hydroxypropyl)-4,7-dimethy)-4,7-triazacyclononane (S-L-Me2R), and (R)-1-(2-hydroxypropyl)-4,7-dimethyl-1,4,7-triazacyclononane (R-L-Me2R), have been synthesized. Reaction of manganese dichloride with the chiral macrocycles S-L-Me2R and R-L-Me2R in aqueous ethanol gives, upon oxidation with hydrogen peroxide, the brown dinuclear Mn(III)-Mn(IV) complexes which are enantiomers, [Mn-2(S-L-Me2R)(2)(mu-O)(2)](3+) (S,S-1) and [Mn-2(R-L-Me2R)(2)(mu-O)(2)](3+) (R,R-1). The single-crystal X-ray structure analyses of [S,S-1][PF6](3)center dot 0.5(CH3)(2)CO and [R,R-1][PF6](3)center dot 0.5(CH3)(2)CO show both enantiomers to contain Mn(III) and Mn(IV) centers, each of which being coordinated to three nitrogen atoms of a triazacyclononane ligand and each of which being bridged by two oxo and by two chiral hydroxypropyl pendent arms of the macrocycle. The enantiomeric complexes S,S-1 and R,R-1 were found to catalyze the oxidation of olefins, alkanes, and alcohols with hydrogen peroxide. In the epoxidation of indene the enantiomeric excess values attain 13%. The bond selectivities of the oxidation of linear and branched alkanes suggest the crucial step in this process to be the attack of a sterically hindered high-valent manganese-oxo species on the C-H bond.