J. Chen et al., 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes modified for extended conjugation and restricted bond rotations, J ORG CHEM, 65(10), 2000, pp. 2900-2906
Five new, constrained, aryl-substituted 4,4-difluoro-4-bora-3a,4a-diaza-s-i
ndacene (BODIPY) dyes (3f,g and 4h-j) were prepared and investigated to see
if they have more favorable fluorescence characteristics than the unconstr
ained systems 2 that were prepared in previous studies. Dye types 3 and 4 h
ave relatively rigid conformations caused by the heteroatom (3f and 3g) or
ethylene bridge (4h-j) linkers that preclude free rotation of the substitut
ed-benzene molecular fragments. In the event, the new dye types 3 and 4 hav
e longer lambda(max) (abs) (620-660 nm) and lambda(max) (fluor) (630-680 nm
) values than compounds 2, They also exhibit higher extinction coefficients
(>100 000 M (1) cm(-1) except for 3g). Their fluorescent quantum yields ar
e high (up to 0.72 for 4j), with the exception of compound 3g, which has a
quantum yield of only 0.05. The redox properties of dyes 3 and 4 have also
been examined.