Novel aluminum-BODIPY dyads: intriguing dual-emission via photoinduced energy transfer

Abstract

Three novel BODIPY-based heterodinuclear complexes, [salen(3,5-Bu-t)(2)Al-(OC6H4-BODIPY)] (6), [salen(3,5-Bu-t)(2)Al-(OC6F2H2-BODIPY)] (7), and [(mq)(2)Al-(OC6H4-BODIPY)] (8) (salen = N,N'-bis(salicylidene)ethylenediamine,BODIPY = 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene, and mq = methyl-8-quinolinolato) were prepared and characterized by multinuclear NMR spectroscopy. The specific structures of 6-8 were also determined by single crystal X-ray analysis. In particular, the salen-based heterodinuclear complexes 6 and 7 exhibited higher thermal stability (T-d5 = 309 and 306 degrees C, respectively) than that of the closely related mononuclear aluminum or BODIPY compounds, except for 8. The UV/vis absorption and PL spectra for 6 and 7 indicated a significant photoinduced energy transfer from the aluminum-salen moiety to the BODIPY group in an intramolecular manner. Theoretical calculations revealed independent transition states of the aluminum-salen moiety or the BODIPY group in the Al-III-BODIPY dyads, further supporting these experimental results