Nanographenes are a class of large polycyclic aromatic hydrocarbons (PAHs) with optical and electronic properties that arise from their extended π-conjugated systems. This internship focused on the multi-step organic synthesis of functionalized dibenzo[hi, st]ovalene (DBOV) precursors for optimization and use in biosensing. A Sonogashira coupling selectively installed a TIPS-alkyne at the C–I position of 4-bromo-2-chloro-1-iodobenzene (96% yield); subsequent borylation via selective lithium-halogen exchange gave the corresponding arylboronic acid (65%); and a Suzuki cross-coupling with 7-bromo-2-naphthaldehyde afforded a biaryl aldehyde intermediate (77%). A PtCl₂-catalyzed intramolecular cyclization of the TIPS-protected alkyne was then optimized by bypassing the deprotection step, attaining the chlorinated chrysene core, which was confirmed by mass spectrometry and NMR.
This synthetic groundwork became the basis of a biosensing project aimed at addressing the limitations of commercially available continuous glucose monitors (CGMs). Most commercial CGMs use enzyme-based sensors that degrade within 10–15 days due to denaturation and oxidative degradation. The only commercially available optical CGM (Senseonics Eversense) relies on UV/blue excitation (~380–470 nm) that limits tissue penetration and requires frequent fingerstick calibration during its first two weeks of use. To address this, a fluorescent glucose sensor was designed around DBOV, a red/near-infrared-emitting nanographene (~650 nm) whose emission falls within the tissue optical window (650–1350 nm), enabling lower-background readouts.
A novel proof-of-concept compound was constructed by incorporating 2-amino-6-bromonaphthalene as the Suzuki coupling partner in place of the naphthaldehyde, forming an aryl amine system (90% yield), followed by Miyaura borylation at the C–Cl position to install the arylboronic acid. Using an internal charge transfer (ICT) approach, upon binding glucose, the boron converts from trigonal planar sp² to tetrahedral sp³, losing its ability to withdraw electrons, which is expected to shift the emission. Initial qualitative fluorescence testing showed clear, glucose-dependent quenching under UV excitation, demonstrating glucose sensitivity in a smaller aromatic model of the DBOV target.