1,8‐Bis(dimethylamino)4,5‐dihydroxynaphthalene, a Natural, Intramolecularly Protonated “Proton Sponge” with Zwitterionic Structure

Not the expected structure 1, but the zweitterionic isomer 2 is found in crystals and solutions of the title compound. Molecules of 2 in the crystal form a type of belt, in which the positive part of the wzeitterion faces the negative part of its neighbor. This belt is coordinated to a corresponding second belt, in which the zwitterions are oriented in the opposite direction. This very interesting crystal packing prompts further studies of anisotropic crystal properties.