UV photo-uncaging of Ru(II)-polypyridyl bioconjugates in high vacuum

Ruthenium(II) polypyridyl complexes exhibit rich photophysics that, in solution, have been widely exploited in chemical applications ranging from catalysis to ligand release. Here, we extend this concept to the gas phase by investigating photo-uncaging and charge-state control of [(tpy)(acac)RuL]^n+/- complexes, where the leaving moiety L are simple pyridine derivatives - with or without a charged group - and pyridines conjugated to polypeptide cargoes such as insulin. We find that sequential absorption of two photons at 355 nm or 266 nm can drive efficient ligand loss. In the absence of solvent stabilization and under the high photon fluences accessible in molecular beam experiments, photo depletion becomes highly efficient, enabling practical optical manipulation relevant to mass spectrometry, gas-phase photochemistry, and molecular quantum optics.