Photochemical dynamics of Mg+-acetaldehyde: C–H vs. C–C bond activation pathways

We have investigated the chemical dynamics of Mg+-acetaldehyde bimolecular complexes following Mg+-centered (3p←3s) excitation. Non-reactive dissociation to Mg+ is the dominant decay channel. However, excitation in the 3pσ(A′)←3sσ(A′) band also results in reactive dissociation to MgH+, MgCHO+, and MgCH3+ products, showing a clear σ-like electronic orbital alignment preference for chemical quenching. Isotope substitution shows reaction involves a direct attack on the aldehydic C–H or C–C bonds; the relative product branching indicates that the probabilities for C–H and C–C bond cleavage are comparable.