Preparation and Absorption and Circular Dichroism Spectra of Cobalt(III) Complexes withN,N,N′,N′-Tetrakis(2-aminoethyl)-1,2-ethanediamine, -1,3-propanediamine, -1,4-butanediamine, and -(R,R)-and -(R,S)- 2,4-pentanediamine

Cobalt(III) complexes of new sexidentate ligands,N,N,N′,N′-tetrakis(2-aminoethyl)-1,3-propanediamine (ttn), -1,4-butanediamine (ttmd), and -(R,R)- and -(R,S)-2,4-pentanediamine (tptn) were prepared and resolved except the RR-tptn complex which formed the Δ-isomer stereoselectively. The monocyano complexes of N,N,N′,N′-tetrakis(2-aminoethyl)-1,2-ethanediamine (ten) and ttn, in which the ligands act as a quinquidentate, were also prepared. Absorption and CD spectra of these complexes and the known [Co(ten)]3+ complex were compared with one another. The first d-d absorption bands of the sexidentate complexes, [Co(A)]3+ are shifted to smaller wave numbers in the order, ttn>ten>ttmd for A, but those of [Co(CN)(HA)]3+ are in the reverse order, ten>ttn. The d-d absorption bands of [Co(RS-tptn)]3+ which contains one axial methyl group show the remarkable red shift and the hyperchromic effect as compared with those of [Co(RR-tptn)]3+ with two equatorial methyl groups.