Symmetrically Backfolded Molecules Emulating the Self-Similar Features of Sierpinski Triangle

Novel branching motif in hierarchical self-similar molecules: we present an under-explored class of molecules featuring striking geometric resemblance to the famous fractal of Sierpinski triangle. Unlike the more traditional, starburst dendrimers, the centripetal-shaped Sierpinski molecules feature side branches symmetrically bent away from the growth direction of the main branch, thus contrasting the natural-tree shape. Molecule G3 exhibits three distinct levels of structural hierachy comprising the primary, secondary and tertiary branches, while the smaller G2 contains only features of the 1st and 2nd orders. In spite of the much larger conjugated backbone of G3, its UV-vis absorption remains little shifted in wavelength compared to G2, while the emission of G3 is curiously blue-shifted by over 50 nm from that of G2.