SYNTHESIS AND STRUCTURAL AND SPECTROSCOPIC STUDIES OF MANGANESE COMPLEXES OF PENDANT-ARM MACROCYCLES BASED ON 1,4,7-TRIAZACYCLONONANE - CRYSTAL-STRUCTURES OF THE MANGANESE(II) COMPLEX [MNLH3][MNCL4] AND OF THE MIXED-VALENCE MANGANESE(II)-MANGANESE(IV) HYDROGEN-BRIDGED DIMER [MNLH3LMN][PF6]3(LH3=N,N',N''-TRIS[(2S)-2-HYDROXYPROPYL]-1,4,7-TRIAZACYCLONONANE), AND OF THE MANGANESE(IV) MONOMER [MNL'][CLO4](L'H3=N,N',N''-TRIS(2-HYDROXYETHYL)-1,4,7-TRIAZACYCLONONANE)

The pendant-arm macrocyclic ligand N,N',N"-tris[(2S)-2-hydroxypropyl]-1,4,7-triazacyclononane (LH3) forms two types of manganese complexes. A mononuclear Mn(II) complex, [MnLH3][MnCl4] (1), is formed when the ligand is fully protonated. Under mildly basic conditions, partial deprotonation occurs and the mixed-valence Mn(II), Mn(IV) dimer [Mn(II)LH3LMn(IV)][PF6]3 (2) is produced. The crystal structures of both complexes have been determined: 1 is orthorhombic, space group P2(1)2(1)2(1), with a = 10.744 (2) angstrom, b = 14.186 (4) angstrom, c = 15.603(3) angstrom, and Z = 4; 2 is rhombohedral, space group R3, with a = 10.472 (1) angstrom, c = 36.637 (7) angstrom, and Z = 3. A notable feature of the structure of the dimer is that the Mn(II) and Mn(IV) halves have different geometries; the coordination around the Mn(II) is trigonal prismatic while that around Mn(IV) is pseudooctahedral. The absorption and CD spectra, the cyclic voltammetry, and the temperature-dependent paramagnetism of the mixed-valence species are reported. The analogous unmethylated ligand, N,N',N"-tris(2-hydroxyethyl]-1,4,7-triazacyclononane (L'H3)) forms a monomeric Mn(IV) complex, [MnL'][ClO4] (3), which has pseudooctahedral geometry. The crystal structure of 3 has also been determined: it is cubic, space group P2(1)3, with a = 14.761 (3) angstrom and Z = 8. The cations of 3 are arranged in pairs with weak contacts between the alkoxy atoms of one molecule and the methylene hydrogens of the other.