Ligand field properties of the peptide nitrogen: The sharp-line electronic spectrum of mer-di(3-aminopropyl)amine(glycylglycinato-O,N,N′)-chromium(III)

Abstract

An Angular Overlap Model calculation was used to fit the electronic spectrum, particularly the sharp-line positions, of [Cr(dpt)(glygly)]ClO 4·0.5C 4H 6N 2O 2·2.5H 2O [dpt = di(3-aminopropyl)amine, H 2glygly = glycylglycine] at 77 K. An e π value of 502 cm −1 for the peptide nitrogen indicates that it is a weak net π-donor to chromium(III), presumably because donation from the filled π-orbital and back-donation to the empty π-antibonding orbital are almost in balance.