Vibrational Strong Coupling of Organometallic Complexes

Strong coupling of optical and molecular vibrational states to form polariton states is a promising route toward the modification of molecular bond properties without changing the constituent atoms or formal bonding structure. The transition from weak to strong coupling of ligand vibrational modes of aqueous organometallic complex ions to microfluidic FabryPerot cavity modes is demonstrated using the Fe(CN)(6)(4-) ion as a model system. It was found that the complex can exhibit tunable strong vibrational coupling while dissolved in solution at moderate concentrations, with a lower limit of approximately 15 mM, due to its large molar extinction coefficient and narrow resonance bandwidth. Combining the exquisite fluid control of microfluidic devices with the ability to modify ligand bond properties of transition metal complexes via vibrational strong coupling may lead to novel methods for the examination of catalytic reaction mechanisms and provide a new means for tailoring catalyst molecules.