The use of KBr pellets as an interference-free matrix for performing time-resolved infrared (TR-IR) measurements on samples in their crystalline state is described and demonstrated. Step-scan Fourier transform
infrared time-resolved spectroscopy (S2FT-IR TRS) is used to measure the infrared (IR) absorption difference (ΔA, excited state minus ground state) spectra of the long-lived charge-transfer
excited states of polypyridine Ru(II) and Pt(II) complexes pressed into KBr pellets. A comparison of the difference spectra measured for the metal-to-ligand charge-transfer (3MLCT) state of the
Ru(II) complex in a KBr pellet vs. acetonitrile (ACN) solution is used to validate the technique. The Pt(II) complex could not be analyzed in solution because of its extremely poor solubility. Thus, these
results illustrate one of the significant advantages of performing TR-IR measurements on solid KBr sample pellets.
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