TY  - JOUR
AU  - Loru, Donatella
AU  - Sun, Wenhao
AU  - Nootebos, Hugo
AU  - Steber, Amanda L.
AU  - Ferrari, Piero
AU  - Schnell, Melanie
TI  - Probing the structure and dynamics of the heterocyclic PAH xanthene and its water complexes with infrared and microwave spectroscopy
JO  - Physical chemistry, chemical physics
VL  - 26
IS  - 39
SN  - 1463-9076
CY  - Cambridge
PB  - RSC Publ.
M1  - PUBDB-2024-05172
SP  - 25341-25351
PY  - 2024
AB  - To assess the presence of oxygen-containing polycyclic aromatic hydrocarbons (OPAHs) in the interstellar medium and understand how water aggregates on an OPAH surface, we present a comprehensive gas-phase spectroscopy investigation of the OPAH xanthene (C<sub>13</sub>H<sub>10</sub>O) and its complexes with water using IR-UV ion dip spectroscopy and chirped-pulse Fourier transform microwave spectroscopy. The far-infrared spectrum of xanthene shows weak features at 3.42, 3.43, and 3.47 μm, which have been suggested to partly originate from vibrational modes of PAHs containing sp<sup>3</sup> hybridized carbon atoms, in agreement with the molecular structure of xanthene. The high resolution of rotational spectroscopy reveals a tunneling splitting of the rotational transitions,  which can be explained with an out-of-plane bending motion of the two lateral benzene rings of xanthene. The nature of the tunnelling motion is elucidated by observing a similar splitting pattern in the rotational transitions of the singly-substituted <sup>13</sup>C isotopologues. The rotational spectroscopy investigation is extended to hydrates of xanthene with up to four water molecules. Different xanthene-water binding motifs are observed based on the degree of hydration, with O-H …π interactions becoming preferred over O-H …O<sub>xanthene</sub> interactions as the degree of hydration increases. A structural comparison with water complexes of related molecular systems highlights the impact of the substrate's shape and chemical composition on the arrangement of the surrounding water molecules.
LB  - PUB:(DE-HGF)16
C6  - pmid:39230416
UR  - <Go to ISI:>//WOS:001304182800001
DO  - DOI:10.1039/D4CP03030C
UR  - https://bib-pubdb1.desy.de/record/612159
ER  -