Ph$_3$AsO as a strong hydrogen-bond acceptor in cocrystals with hydrogen peroxide and gem-dihydroperoxides

Hydrogen-bonded cocrystals have attracted considerable attention as they allow fine-tuning of properties through the choice of hydrogen-bond donors and acceptors. In this study, triphenylarsine oxide (Ph$_3$AsO) is introduced as a strong hydrogen-bond acceptor molecule. Due to its higher Lewis basicity compared to triphenylphosphine oxide (Ph$_3$PO), it acts as a strong hydrogen-bond acceptor, which is demonstrated in six new cocrystals with H$_2$O$_2$ and gem-di(hydroperoxy)cycloalkanes. All cocrystals formed large, high-quality single crystals, which were analyzed by X-ray diffraction and IR spectroscopy. The cocrystal of Ph$_3$AsO with H$_2$O$_2$ shows prolonged stability without loss of oxidative power. In addition, the newly formed interactions were also present in solution and were detected by NMR spectroscopy. The higher electron-donating ability of Ph$_3$AsO compared to Ph$_3$PO was confirmed by competition experiments. Ph$_3$AsO exclusively binds H$_2$O$_2$, even in dilute aqueous solutions and in the presence of Ph$_3$PO. This study expands the range of hydrogen-bond acceptors and demonstrates that Ph$_3$AsO is a useful cocrystallizing tool in crystal engineering and a sensitive marker for hydrogen peroxide.