Cationic Ir(III) complexes with one diimine and biscyclometalating ligands are attracting great interests as broadband reverse saturable absorbers because the heavy-atom effect of Ir facilitates the intersystem crossing and makes direct transition from the ground state to the triplet excited state possible. Both features increase the population of the triplet excited state and thus enhance the triplet excited-state absorption, which is critical for reverse saturable absorption (RSA) of nanosecond laser pulses. In addition, the excited-state properties of these complexes can be readily tuned by variation of the diimine or cyclometalating ligand -conjugation. In order to obtain Ir(III) complexes with weak broadband ground-state absorption, but strong excited-state absorption in the visible to the near-IR region, we designed and synthesized a variety of heteroleptic cationic Ir(III) complexes with varied -conjugation on the diimine or the cyclometalating ligands. We found that extending the -conjugation of the diimine ligand via benzannulation on the diimine ligand exhibited dramatically different effects on the ground-state and excited-state absorption and on the triplet excited-state lifetime depending on the site of benzannulation.

报告人简介：Prof. Wenfang Sun is the James Meier Senior Professor and the Water F. and Verna Gehrts Presidential Professor at the Department of Chemistry and Biochemistry, North Dakota State University (NDSU). She received her B.S. degree in 1990 from Wuhan University, China; and her Ph.D. degree in Organic Chemistry from the Institute of Photographic Chemistry, Chinese Academy of Sciences in 1995. She has published 107 peer-reviewed journal papers and 23 conference full papers. She received numerious awards, including the NSF CAREER Award (2005-2011), the NDSU Fred Waldron Award for Outstanding Research (2012), the NDSU Walter F. and Verna Gehrts Professorship (2011), the NDSU Bison Ambassadors Apple Polisher Honoree (2009), the NDSU Featured Faculty (2006), and the 2nd-Class Chinese Academy of Sciences Natural Science Award (2002).