Symmetry-directed photoinduced chemical reactions

GERMAN E. PIESLINGER; ALEJANDRO CADRANEL; LUIS M. BARALDO; PAOLA S. OVIEDO; DIRK GULDI

München

Congreso; Koordinationschemie-Treffen; 2019

Upon photoexcitation of the bimetallic ruthenium polypyridine complex [Ru(tpy)(bpy)(µ-CN)Ru(py)4Cl]2+, biexponential emission lifetimes are observed. By means of ultrafast vis-NIR transient absorption spectroscopy, the differential spectra of the two emitting MLCT states were obtained. One of these states, MLCTz, presents an intense NIR feature assigned to a photoinduced IVCT transition. The other emitting state, MLCTxy, is NIR silent. We concluded that in MLCTz the hole sits in an orbital parallel to the intermetallic axis, while in MLCTxy the hole is perpendicular. The symmetry of these excited states dictate their reactivities, as shown in the donor-acceptor complex trans-[Ru(tpy)(bpy)(µ-CN)Ru(py)4(µ-NC)Cr(CN)5]. Energy transfer from MLCTz to a Cr-centered state is observed to occur in 170 ps. In contrast, the symmetry of MLCTxy precludes its engagement in energy transfer events, and its lifetime is very similar to that in the absence of any acceptor.Literature:[1] A. Cadranel et al. Phys. Chem. Chem. Phys. 2017, 19, 2882?2893.[2] P. S. Oviedo et al. J. Phys. Chem. C 2019, DOI: 10.1021/acs.jpcc.8b09499.