Dianiline Squaraine Dyes: Synthetic and Non-Synthetic Applications

Dianiline squaraine dyes, vibrantly colored compounds, are renowned for their physical and analytical chemistry applications. These dyes have a core structure consisting of a cyclobutenedione ring with two aniline derivatives attached in a 1,3 configuration, creating a stabilizing electron transfer effect between donor and acceptor groups. This unique electronic profile enables dianiline squaraine dyes to absorb and emit light in the near-infrared spectrum. Traditionally, these compounds are extensively employed in biological imaging, photodynamic therapy, non-linear optics, photovoltaics, and ion-sensing. Despite possessing multiple sites of potential reactivity, few reported studies examine the use of squaraine dyes as synthetic building blocks. This thesis explores the development of squaraine scaffolds with versatile, functional groups as readily available starting materials for building more complex small molecules and leveraging their inherent reactivity to design chemically-driven analytical protocols. To date, the applications of squaraine dyes have been successfully extended towards: (1) the development of squaraine dyes as colorimetric chemodosimeters for trace transition metals, (2) accessing highly functionalized NHC-Squaraines via an NHC-mediated dearomative skeletal rearrangement of squaraine dyes, (3) the development of proline bound 1,3-semisquaraine as a catalyst in Brønsted acid catalysis, (4) the design of proline bound 1,3-squaramide as chiral transition metal-ligand in enantioselective catalysis.