Solvent Effects on Proton Nmr Chemical Shifts of Macrocyclic and Nonmacrocyclic Compounds Employed with N-H Functional Group

The proton nmr spectra for six compounds: 6-ethyldibenzo[b, i]-1,4,8,11-tetraazacyclotetradeca-4,6-diene (1), dibenzo[b, i]-1,4,8,11-tetraazacyclotetradecane, l,3-bis(2-arninophenylamino)propane, 1,4,8,11-tetraazacyclotetradecane(cyclam), N-ethylaniline and diethylamine, were measured in twelve solvents. Every proton signal is shifted to higher fields in toluene-d8 and benzene-d6 than in cyclohexane-d12 solution. On the other hand, the proton signals for the secondary amines are shifted to low fields in polar solvents. Proton signals for methylene and/or methyl groups are not shifted. The amine signal for 1 (arom.) shows a small shift in every solvent. There is no appreciable interaction between the amine proton and solvent because the amine proton is in the inner space of 1. The amine signals, except for 1 (arom.), have an increasing down-field shift in the following order: toluene-d8, benzene-d6, cyclohexane-d12, dichloromethane-d2, chloroform-d, nitromethane-d3, acetonitrile-d3, acetone-d6, tetrahydrofuran-d8, N,N-dimethylformamide-d7, dimethyl sulfoxide-d6, pyridine-d5. These results and solvent effects are discussed.