1,8-BIS(DIMETHYLAMINOMETHYL)NAPHTHALENE - A NEW PROTON SPONGE

1,8-bis(dimethylaminomethyl)naphthalene (DMAMN), which exhibits the features of a proton sponge, has been synthesized. H-1 NMR, infrared and X-ray diffraction studies on protonated DMAMN indicate the formation of intramolecular NHN+ hydrogen bonds which are a little weaker than those in protonated 1,8-bis(dimethylamino)naphthalene (DMAN). This is particularly apparent in the IR spectra of solid salts (appearance of an absorption above 2000 cm-1). One should emphasize that in CH3CN solution the intensity of the broad continuum for DMAMN.H+ is larger than that for DMAN.H+. In the latter case a pi-electron conjugation contributes, which in intramolecular hydrogen bonds reduces the transition moment of the protonic stretching vibrations. The structure of DMAMN nitrate was determined by X-ray diffraction. Crystals of DMAMN.HNO3 are monoclinic, space group P2(1)/c with a = 10.938(3), b = 11.829(3), c = 12.497(3) angstrom, beta = 90.40(3)-degrees and Z = 4. The intramolecular [NHN]+ hydrogen bond length is 2.642(3) angstrom.