The syntheses and characterization of the macrobicyclic hexaamine chromium(III) complexes of diamsar (1,8-diamino-3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane) and sar (3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane) ligands (1–3) are reported. The complexes were isolated as stable, paramagnetic, and monomeric salts. crystallized in the space group P21/c, (Z = 4, a = 9.474 (2) A, b = 13.331 (3) A, c = 18.221 (5) A, β = 92.756 (0)°) with the octahedral cation in the C3-lel conformation and an average Cr-N distance of 2.070 (3) A. The complexes are high-spin d3 with room-temperature magnetic moments near the spin-only value of 3.87 μB• The aqueous electrochemistry exhibits a quasi-reversible Cr(III/II) couple below -1 V for each complex and a further irreversible Cr(II/0) reduction near -1.6 V; the chromium(II) complexes are not stable in the coulometric time scales (minutes). The Cr(III) electronic spectra show the expected spin-allowed absorption bands of 4T2g4A2gand 4T1g4A2g origin as well as weak spin-forbidden bands of 2Eg, 2Tlg4Agorigin in the visible region. The first of these (4T2gtransition) is split by -400 cm-1and is relatively high in intensity, and the splitting is probably due to the lowered symmetry (D3). Cr(sar)3+ and Cr(diamsar)3+ emit rather strongly at 77 K 0.02), but give no detectable emission above 273 K. Photodecomposition of Cr(diamsar)3+ is ~ 104-fold smaller than that of the Cr(en)33+ ion, and possible reasons for this are discussed.