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

Abstract

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 (phi(F) = 0.19) with m-CPBA gives selective S-dioxidation (phi(F) = 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 = 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; Cu(2+) addition resulted in smooth absorption decreases which were modeled to support 1:1 substrate: M(2+) binding; for Hg(2+) 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 Br(2) 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.