Synthesis of 4-[N-methyl-4-pyridinio]-phenolate (POMP) and negative solvatochromism of this model molecule in view of nonlinear optical applications

4-[N-Methyl-4-pyridinio]-phenolate or [4-(phenyloxido)-N-methylpyridinium, POMP] has been synthesized via Suzuki cross-coupling reaction. POMP undergoes a strong negative solvatochromism (blue shift) as the solvent polarity increases and behaves qualitatively as the famous empirical polarity parameter ET(30). However, it should be noted that the previously published theoretical investigations of POMP revealed unexpected difficulties in the interpretation of its structure. Interestingly, it is confirmed here in the sense that the experimental transition energy in nonpolar solvents seems by far less important than predicted by different computational methods. Therefore, POMP is highly prospective for (i) the comprehension of betaines solvatochromism, (ii) the development of new molecules with large first and second hyperpolarizabilities useful for doping polymers, the aim being to elaborate efficient processable materials for quadratic optics.