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

Abstract

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‐H2O 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 Ow‐H⋅⋅⋅O hydrogen bond, not observed previously in the gas phase, reinforced by a weak four‐center trifurcated acceptor C−H⋅⋅⋅Ow interaction. Surprisingly, all structural signatures show the weakness of these interactions. The complex TATP‐(H2O)2 is formed from the monohydrated TATP by the self‐association of water.

How Aromatic Fluorination Exchanges the Interaction Role of Pyridine with Carbonyl Compounds: The Formaldehyde Adduct

“…Fourier transform microwave (FTMW) spectroscopy in combination with supersonic‐jet techniques [26–28] is particularly suited to study weakly bound molecular complexes, allowing to explore their structure, intermolecular interactions, and dynamics [24,29,30] . The structural data obtained from this technique have shown the fundamental differences between interactions like the C−H⋅⋅⋅π bond in benzene⋅⋅⋅H 2 O [19,20] or corannulene⋅⋅⋅H 2 O [31] and the lone pair⋅⋅⋅π‐hole contact responsible for the formation of C 6 F 6 ⋅⋅⋅H 2 O [16] .…”

“…In the same way, one could compare the differences between the O−H⋅⋅⋅N hydrogen bond, forming pyridine⋅⋅⋅H 2 O, [21] the lone pair⋅⋅⋅π‐hole contact observed in C 5 F 5 N⋅⋅⋅H 2 O [17] or the n →π* interaction dominating the pyridine⋅⋅⋅H 2 CO adduct [24] . Furthermore, the rotational spectrum shows the rich intermolecular dynamics associated with the internal rotation and other intermolecular vibrations of the adduct, ranging from free rotation in C 6 F 6 ⋅⋅⋅H 2 O [16] or corannulene⋅⋅⋅H 2 O [31] to hindered rotations as occur in pyridine⋅⋅⋅H 2 O [21] or triacetonetriperoxyde⋅⋅⋅H 2 O [30] …”

“…Fourier transform microwave (FTMW) spectroscopy in combination with supersonic‐jet techniques[ 26 , 27 , 28 ] is particularly suited to study weakly bound molecular complexes, allowing to explore their structure, intermolecular interactions, and dynamics. [ 24 , 29 , 30 ] The structural data obtained from this technique have shown the fundamental differences between interactions like the C−H⋅⋅⋅π bond in benzene⋅⋅⋅H 2 O[ 19 , 20 ] or corannulene⋅⋅⋅H 2 O [31] and the lone pair⋅⋅⋅π‐hole contact responsible for the formation of C 6 F 6 ⋅⋅⋅H 2 O. [16] In the same way, one could compare the differences between the O−H⋅⋅⋅N hydrogen bond, forming pyridine⋅⋅⋅H 2 O, [21] the lone pair⋅⋅⋅π‐hole contact observed in C 5 F 5 N⋅⋅⋅H 2 O [17] or the n →π* interaction dominating the pyridine⋅⋅⋅H 2 CO adduct.…”

“… [24] Furthermore, the rotational spectrum shows the rich intermolecular dynamics associated with the internal rotation and other intermolecular vibrations of the adduct, ranging from free rotation in C 6 F 6 ⋅⋅⋅H 2 O [16] or corannulene⋅⋅⋅H 2 O [31] to hindered rotations as occur in pyridine⋅⋅⋅H 2 O [21] or triacetonetriperoxyde⋅⋅⋅H 2 O. [30] …”

Perfluorination of Aromatic Compounds Reinforce Their van der Waals Interactions with Rare Gases: The Rotational Spectrum of Pentafluoropyridine-Ne

“…This technique makes possible the unambiguous discrimination between different isomers, including tautomers, conformers, or isotopomers. The spatial mass distribution of such species has unique spectroscopic constants and distinct individual rotational spectra, a key feature that makes FTMW techniques powerful tools [ 6 ] in cases where other techniques may struggle. Complexes generated in supersonic expansions are isolated species that can be characterized in absence of intermolecular forces existing in condensed phases.…”