Matrix effects and their role in the low-temperature photochemistry of (η-Aniline)Cr(CO)3

The low-temperature chemistry and photochemistry of (η6-Aniline)Cr(CO)3 was investigated by matrix isolation techniques in frozen CH4 or N2. The spectroscopic properties of the matrix changed both during the deposition process and also following annealing of the matrix to 40 K. These changes are explained by the elimination of lattice defects in the crystalline medium which forces haptotropic changes to (η6-Aniline)Cr(CO)3 producing (η2-N-Aniline)Cr(CO)3 and (η3-N-Aniline)Cr(CO)3 as identified by IR spectroscopy. These assignments are supported by DFT calculations which also provide estimates of the energetics of the haptotropic shift processes. The reduced hapticity species exhibit different photochemical properties compared to (η6-Aniline)Cr(CO)3. They undergo complete decarbonylation following irradiation at 436 nm.

Graphical abstractThe structure of (η-Aniline)Cr(CO)3 is changed by annealing the crystalline matrix in low temperature matrix isolation experiments. The reduced hapticity species produced in this process undergoes complete decarbonylation following low-energy irradiation. DFT calculations suggest that the singlet–triplet energy gap is smaller for the reduced hapticity species compared to (η6-Aniline)Cr(CO)3.Figure optionsDownload full-size imageDownload as PowerPoint slide