High-pressure Chemistry of Red Phosphorus and Ammonia

The chemistry of phosphorus is typically based on the white molecular form (P4). Although being harmful and toxic, particularly for aquatic organisms, white phosphorus is preferred for its reactivity over the red polymeric form (Pred), which is more stable and less toxic. Switching from white to red phosphorus would be of great importance for every industrial process involving organophosphorus compounds. However, the chemistry of red phosphorus is largely unexplored: investigating novel reactive pathways for Pred is of interest both from a fundamental and from an applicative point of view. In high-pressure conditions, two-photon (TP) absorption processes by near-UV wavelengths have been proved to be effective in inducing chemical reactivity on heterogeneous mixtures of Pred with water1 or ethanol.2 The efficiency of this processes is related to the dissociative character of the electronic excited states of the involved molecular systems. The generation of highly reactive species in high-density conditions is able to trigger chemical reactivity with Pred against simple recombination of the molecular fragments. Ammonia, a model system of fundamental interest in chemistry, which also features dissociative electronic excited states3, can be used to activate the formation of P-N bonds and introducing N functionalities in Pred at room temperature and in total absence of solvents, catalysts and radical initiators. Here we present the results of our study about the laser-induced high-pressure reactivity of red phosphorus and ammonia mixtures in different thermodynamic conditions corresponding to different ammonia phases. Pressure has been generated by means of DAC, using the UVML emission (centered at ~350 nm) line of an Ar+ laser as excitation source for the activation of TP absorption processes. The starting samples and the reaction products have been characterized by means of spectroscopic methods (FTIR and micro-Raman spectroscopy). References [1] M. Ceppatelli, R. Bini, M. Caporali, M. Peruzzini, Angew. Chem. Int. Ed. 52, 2313-2317 (2013) [2] M. Ceppatelli, S. Fanetti, R. Bini, J. Phys. Chem. C 117, 13129-13135 (2013) [3] J. Urbanek, P.Vöhringer, J. Phys. Chem B 118, 265-267 (2014).