A1H,13C and15N NMR investigation of three substituted DMAN derivatives and their monoprotonated salts

We report a 1H, 13C and 15N NMR investigation of one symmetrically substituted 2,7-dichloro and two unsymmetrically substituted 2-chloro and 4-bromo DMAN [1,8-bis(dimethylamino)naphthalene] proton sponges and their protonated salts. From a consideration of the NMR data reported we conclude, that the most sensitive parameters for investigating compounds of this kind are 1J (15N–1H) and 15N and 1H chemical shifts for the nuclei in the [N8–H–N1]+ bridge. A further significant NMR parameter is 3J (1H–1H) for the bridging proton and the N(CH3)2 protons. An analysis of the values of 1J (15N–1H) for the studied compounds is consistent with the view that in the investigated system equilibrium between two tautomeric forms occurs. A study at temperatures between 27 and −40 °C, and a change of solvent, show that the values of the 15N chemical shifts and couplings 1J (15N–1H) and 3J (1H–1H) for the [N8–H–N1]+ bridge are essentially unchanged. This shows that the bonding arrangements of the bridge atoms are stable under these experimental conditions.