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In this short review, we provide an overview of our efforts in developing a family of anodically coloring electrochromic (EC) molecules that are fully transparent and colorless in the charge neutral state, and that can rapidly switch to a vibrantly colored state upon oxidation. We employ molecules with reduced conjugation lengths to center the neutral state absorption of the electrochrome in the ultraviolet, as desired for highly transparent and colorless materials. Oxidation creates radical cations that absorb light in the visible and near infrared regions of the electromagnetic spectrum, thus providing a host of accessible colors. Combining a density functional theory (DFT) computational approach fed back to the synthetic effort, target molecules are proposed, synthesized and studied, directing us to develop a complete color palette based on these high contrast ACE molecules. Utilizing pendant phosphonic acid binding substituents in concert with high surface area mesoporous indium tin oxide (ITO) electrodes, the electrochromes can be distributed throughout the oxide film, bringing high extent of light absorption and color density. 

Abstract Conjugated polymers have received significant attention as potentially lightweight and highly tailorable alternatives to inorganic semiconductors, but their synthesis is often complex, produces toxic byproducts, and they are not typically designed to be degradable or recyclable. These drawbacks necessitate dedicated efforts to discover materials with design motifs that enable targeted and efficient degradation of conjugated polymers. In this vein, the synthetic simplicity of 1,4‐dihydropyrrolo[3,2‐b]pyrroles (DHPPs) is exploited to access azomethine‐containing copolymers via a benign acid‐catalyzed polycondensation protocol. Polymerizations involve reacting a dialdehyde‐functionalized dihydropyrrolopyrrole withp‐phenylenediamine as the comonomer usingp‐toluenesulfonic acid as a catalyst. The inherent dynamic equilibrium of the azomethine bonds subsequently enabled the degradation of the polymers in solution in the presence of acid. Degradation of the polymers is monitored via NMR, UV‐vis absorbance, and fluorescence spectroscopies, and the polymers are shown to be fully degradable. Notably, while absorbance measurements reveal a continued shift to higher energies with extended exposure to acid, fluorescence measurements show a substantial increase in the fluorescence response upon degradation. Results from this study encourage the continued development of environmentally‐conscious polymerizations to attain polymeric materials with useful properties while simultaneously creating polymers with structural handles for end‐of‐life management or/and recyclability. 

Abstract Four cross‐conjugated molecules based on the benzo[1,2‐d:4,5‐d’]bisoxazole (BBO) moiety have been synthesized from a common synthon. Theoretical studies indicated that these cruciforms had highly segregated HOMO and LUMO levels enabling semi‐autonomous tuning of the LUMO level from the HOMO through substitution along the 2,6‐axis. The experimental data confirms that the HOMO levels within these systems varied by 0.3 eV, whereas the LUMO levels varied by over 1.6 eV when the electron‐density along the 2,6‐axis was increased. The introduction of relatively electron‐deficient moieties along the 2,6‐axis resulted in a bathochromic shift in the absorption profiles concurrent with the stabilization of the LUMO. These substituents also prolonged the photoluminescent lifetimes owing to improved intramolecular charge transfer states between the 4,8‐ and 2,6‐ axis. The BBO cruciforms were evaluated as donor materials in organic solar cells (OSC)s, but the energy‐level mismatches and poor thin film morphology led to poor performance. These results indicate that benzobisoxazole cruciforms are a promising platform for the development of tunable materials for use in organic semiconductors, but improvements in the optical, electronic and film‐forming properties are needed to enable their use in efficient OSCs.