Optical Effects of <i>S</i>-Oxidation and M^<i>n</i>+ Binding in <i>meso</i>-Thienyl Dipyrrin Systems and of Stepwise Bromination of 4,4-Difluoro-8-(2,5-dibromo-3-thienyl)-4-bora-3<i>a</i>,4<i>a</i>-diaza-<i>s</i>-indacene

We report 16 novel species and 8 molecular structures in studying how meso-thienyl-substituted dipyrrole oxidation, bromination, and metal ion binding impart optical changes, as monitored by UV−vis absorption/emission spectroscopy. Treatment of 4,4-difluoro-8-(3-benzothienyl)-4-bora-3a,4a-diaza-s-indacene (ϕF = 0.19) with m-CPBA gives selective S-dioxidation (ϕF = 0.006). Results of titrations of transition metal- and “scorpionate”-like dipyrrin species varied under room temperature treatment of m-CPBA. Ni-(thienyl-dipyrrin)n (n = 2) degraded significantly in the presence of m-CPBA, whereas related species (M = Cu, Fe, Co; n = 2, 3) were inert. meso-Thienyl group properties were revealed through the use of 3,4,4-triphenyl-8-(thienyl)-4-bora-3a,4a-diaza-s-indacene; Cu2+ addition resulted in smooth absorption decreases which were modeled to support 1:1 substrate:M2+ binding; for Hg2+ 1:2 substrate:M2+ binding was found. Treatment of 4,4-difluoro-8-(2,5-dibromo-3-thienyl)-4-bora-3a,4a-diaza-s-indacene with Br2 gave red-shifted UV−vis absorption band features that grow with increasing dipyrrin bromination. Structures of the di- and tetra-substituted bromination products were obtained.