AB-INITIO STUDIES OF PROTON SPONGES - 1,8-BIS(DIMETHYLAMINO)NAPHTHALENE

The structures of 1,8-bis(dimethylamino)naphthalene and Its protonated forms have been determined by ab initio geometry optimization. The title compound is found to possess C-2 symmetry in the gas phase, and the N(C10H6)N fragment is markedly nonplanar. Protonation causes the molecule to become more planar, as it approaches (without quite attaining) C-2 upsilon symmetry. Asymmetric protonation at one nitrogen is energetically preferred to the symmetric N...H...N bridged form. The predicted proton affinity is within a few kilojoules per mole of an experimental value. The changes in structure and the electron distribution are discussed in terms of the topology of the charge density rho and of del(2) rho, for this and related amines.