Several recent publications recognise the probable existence of various types of ion-pairs in solvents such as N, N'-dimethyl formamide, (DMF), with polarity intermediate between water and hydrocarbons [l-3].
Equilibrium concentrations of solverzrseparated, solvent-shoed and conract ion pairs are visualised as existing in solutions of metal salts in DMF as a result of loose association between cation and anion meeting in the designated type of encounter [ 11. For a solvent as strongly solvating as DMF, contact encounters between cation and aniom probable and cationyanion interactions should mainly arise via association in solvertt-shared or s&enrsqara:ed ion pairs 12, 31. The twin objectives of our spectral studies on saturated solutions of various metal nitrites in DMF, results of which are summarised in table 1, were: fint, to establish the general features of the electronic absorption spectra of NO, in this solvent, as a prelude to photolysis experiments; and second, to obtain spectroscopic evidence for or against the occurrence of cation-anion interactions in these solutions.
Three general features were established for the electronic absorption by NOT at wavelengths greater Gun the transmittance cut-off of the solvent: (i) all