Scientists reveal why metal carbonyls fall apart at different speeds
Researchers used femtosecond spectroscopy to watch two similar molecules—iron and chromium carbonyls—break apart after light exposure, discovering they follow fundamentally different pathways. The finding could inform design of better catalysts and light-activated materials for industrial chemistry and renewable energy applications.
Originaltitel: Different Photodissociation Mechanisms in Fe(CO)<sub>5</sub> and Cr(CO)<sub>6</sub> Evidenced with Femtosecond Valence Photoelectron Spectroscopy and Excited-State Molecular Dynamics Simulations
<p>Measured and calculated time-resolved photoelectron spectra and excited-state molecular dynamics simulations of photoexcited gas-phase molecules Fe(CO)<sub>5</sub> and Cr(CO)<sub>6</sub> are presented. Samples were excited with 266 nm pump pulses and probed with 23 eV photons from a femtosecond high-order harmonic generation source. Photoelectron intensities are seen to blue-shift as a function of time from binding energies characteristic of bound electronic excited states via dissociated-state energies toward the energies of the dissociated species for both Fe(CO)<sub>5</sub> and Cr(CO)<sub>6</sub>, but differences are apparent. The excited-state and dissociation dynamics are found to be faster in Cr(CO)<sub>6</sub> because the repopulation from bound excited to dissociative excited states is faster. This may be due to stronger coupling between bound and dissociative states in Cr(CO)<sub>6</sub>, a notion supported by the observation that the manifolds of bound and dissociative states overlap in a narrow energy range in this system.</p>