Subphthalocyanines (SPcs) are 14 π-electron systems containing a central boron atom with an axial ligand. Much like their larger phthalocyanine (Pc) cousins, SPcs have intense electronic absorption and emission across the visible spectrum, warranting their study for a wide variety of applications, including fluorescence imaging of biological targets. Visibly emitting SPcs may well be applied as cell labelling probes as an <i>in vitro </i>tool, however application <i>in vivo </i>requires absorption and emission in the near-infrared (NIR) window of maximum tissue penetration; synthetic efforts are required to shift absorption into the NIR region. Herein we report a synthetic approach involving mixed cyclization of dinitrile derivatives, with varying aromaticity and heteroatom substitution, to produce low-symmetry SPcs with optical properties that are tunable by design. Intracellular fluorescence in MDA-MB-231 breast tumor cells was observed from SPcs and negative effects on cell viability were found to be mitigated by exchanging the axial ligand of boron. Low-symmetry SPcs show promise as standalone optical probes, but also as synthetic precursors to designer NIR absorbing Pcs via the Kobayashi ring expansion reaction.  Synthetic strategies, optical characterization, and initial tests of biocompatibility of new SPcs and Pc probes will be discussed.

Low-symmetry boron subphthalocyanines as fluorescent imaging probes and precursors for designer metallophthalocyanines

253rd National Meeting (2017)

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