NMR chemical shifts in cuprous salts: The magnetic moment of Cu

An extensive study has been made of chemical shifts of the ⁶³Cu resonance in a number of cuprous salts. The observed trend in chemical shifts for the cuprous halides is in disagreement with theoretical ionicity estimates of either Pauling or Phillips. This trend has been explained by taking into account the relative importance of π bonding for the different halides. On the basis of the present data, CuBr is the most suitable Knight shift reference compound. The measurements indicate μ = 2.2206 nm for ⁶³Cu and μ = 2.3791 nm for ⁶³Cu for reference moment, without diamagnetic correction.