1,8-Bis(dimethylaminomethyl)naphthaiene: a new proton sponge

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Abstract
1,8-bis(dimethylaminomethyl)naphthalene (DMAMN), which exhibits the features of a proton sponge, has been synthesized. 1H 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 π-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 P21/c with a= 10.938(3), b= 11.829(3), c= 12.497(3)Åβ= 90.40(3)° and Z= 4. The intramolecular [NHN]+ hydrogen bond length is 2.642(3)Å.

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