Nonadiabatic Effects in the Molecular Oxidation of Subnanometric Cu5 Clusters

8 pags., 4 figs. -- Published as part of The Journal of Physical Chemistry virtual special issue “Vincenzo Barone Festschrift”The electronic structure of subnanometric clusters, far off the bulk regime, is still dominated by molecular characteristics. The spatial arrangement of the notoriously undercoordinated metal atoms is strongly coupled to the electronic properties of the system, which makes this class of materials particularly interesting for applications including luminescence, sensing, bioimaging, theranostics, energy conversion, catalysis, and photocatalysis. Opposing a common rule of thumb that assumes an increasing chemical reactivity with smaller cluster size, Cu5 clusters have proven to be exceptionally resistant to irreversible oxidation, i.e., the dissociative chemisorption of molecular oxygen. Besides providing reasons for this behavior in the case of heavy loading with molecular oxygen, we investigate the competition between physisorption and molecular chemisorption from the perspective of nonadiabatic effects. Landau−Zener theory is applied to the Cu5(O2)3 complex to estimate the probability for a switching between the electronic states correlating the neutral O2 + Cu5(O2)2 and the ionic O2 − + (Cu5(O2)2)+ fragments in a diabatic representation. Our work demonstrates the involvement of strong nonadiabatic effects in the associated charge transfer process, which might be a common motive in reactions involving subnanometric metal structuresThis work has been partly supported by the Spanish Agencia Estatal de Investigacin (AEI) and the Fondo Europeo de Desarrollo Regional (FEDER, UE) under Grants PID2020- 117605GB-I00, MAT2016-75354-P, and PID2019-107115GBC21 as well as the Austrian Science Fund (FWF) under Grant P29893-N36. The CESGA supercomputer center (Spain) and the CTI-CSIC are acknowledged for having provided computational resourcesPeer reviewe