CIRCULAR DICHROISM OF SOME LESS STRAINED MODEL COMPOUNDS FOR ETHYLENEDIAMINETETRAACETATOCOBALTATE(3) ION

A series of model compounds for Co(EDTA)- have been prepared and resolved. This series includes the following complex ions: 1,3-propanediaminetetraacetatocobaltate(III), Co(1,3-PDTA)-, cis-bis(iminodiacetato)cobaltate(III), cis-Co(IDA)2-, and ethylenediaminetetrapropionatocobaltate(III), Co(EDTP)-. All of these complex ions have the same effective crystal field and general arrangement of chelate rings as Co(EDTA)-, but they have less strained chelate ring systems. The intensities of the visible absorption bands for these compounds are lower than those for Co(EDTA)-, but the net intensities of their CD bands are greater. The observed increase in rotational strength when the strain of the chelate ring system was decreased contradicts predictions of theoretical studies of optical activity of coordination complexes. © 1969, American Chemical Society. All rights reserved.