Microwave Detection of Wet Triacetone Triperoxide (TATP): Non-Covalent Forces and Water Dynamics

The water adducts of triacetone triperoxide (TATP) have been observed by using broadband rotational spectroscopy. This work opens a new way for the gas-phase detection of this improvised explosive. The observed clusters exhibit unusual water dynamics and rarely observed multicenter interactions. TATP-H₂ O is formed from the D₃ symmetry conformer of TATP with water lying close to the C₃ axis. Water rotation around this axis with a very low barrier gives rise to the rotational spectrum of a symmetric top. The main interaction of the monohydrate is a four-center trifurcated donor O_w -H⋅⋅⋅O hydrogen bond, not observed previously in the gas phase, reinforced by a weak four-center trifurcated acceptor C-H⋅⋅⋅O_w interaction. Surprisingly, all structural signatures show the weakness of these interactions. The complex TATP-(H₂ O)₂ is formed from the monohydrated TATP by the self-association of water.