Achieving Closed-Loop Recycling of a Semi-Conjugated Polymer Through the Incorporation of Ester Linkers Along the Backbone

Design strategies to achieve degradation and ideally closed-loop recycling of organic semiconductors have attracted great interest in order to minimize the electronic waste (E-waste). In this work, three ester-incorporated monomers were synthesized by the names of Thiophene-Ester-Ethylene-Thiophene (TEET), Thiophene-Ester-Methylene-Thiophene (TEMT), and Thiophene-Ester-Thiophene (TET), which were co-polymerized via Stille polycondensation with a benzodithiophene (BnDT) π-conjugated unit to yield a series of ester-incorporated polymers: PBnDT-TEET, PBnDT-TEMT, and PBnDT-TET. While the ester-only linker can maintain some extended conjugation in PBnDT-TET, the other two ester linkers having conjugation breaking units result in isolated conjugated segments in PBnDT-TEET and PBnDT-TEMT, evidenced by UV-Vis and CV results. This yields an improved photovoltaic performance of PBnDT-TET compared to PBnDT-TEET. While all three polymers can depolymerize under methanolysis, the alternating co-polymer PBnDT-TEET demonstrates the highest recyclability potential with a single dimethyl ester-functionalized product with an excellent 92 % isolated yield, which can then be repolymerized to reobtain PBnDT-TEET with a 36 % yield. This work provides a framework towards achieving recyclable organic semiconductors to reduce E-waste. Although the incorporation of ester linkers allowed for closed-loop recycling, the low solar cell efficiency of PBnDT-TEET highlights the significant challenge in achieving both recycling and high device performance.

In-flow photooxygenation of aminothienopyridinones generates iminopyridinedione PTP4A3 phosphatase inhibitors

A continuous flow photooxygenation of 7-aminothieno[3,2-c]pyridin-4(5H)-ones to produce 7-iminothieno[3,2-c]pyridine-4,6(5H,7H)-diones has been developed, utilizing ambient air as the sole reactant. N-H Imines are formed as the major products, and excellent functional group tolerance and conversion on gram-scale without the need for chromatographic purification allow for facile late-stage diversification of the aminothienopyridinone scaffold. Several analogs exhibit potent in vitro inhibition of the cancer-associated protein tyrosine phosphatase PTP4A3, and the SAR supports an exploratory docking model.

Novel intramolecular π-π-interaction in a BODIPY system by oxidation of a single selenium center: geometrical stamping and spectroscopic and spectrometric distinctions

A new BODIPY system displaying an intramolecular π-π-interaction was synthesized and studied. When the selenium center was oxidized, the substituted phenyl group undergoes π-π stacking with one side of the BODIPY core. The oxidized form showed, not only a down-field shift in the NMR peak, but also splitting due to geometrical changes that arise when going from C_s to C₁. The compound was characterized by X-ray diffraction; DFT methods helped elucidate the influence of the unexpected π-π stack and its connection to the photophysical properties imparted by the Se oxidation.

Oxidative Transformation of a Tetrathia S-Confused Isophlorin into Porphyrin Cation

The synthesis and redox properties of first generation S-confused isophlorins are described. Despite structural resemblance to a confused porphyrin, spectroscopic and computational studies reveal weak paratropic ring current effects in these 20π macrocycles. They display redox properties atypical of parent tetrathia isophlorins. Experimental evidence supports the oxidation of an unstable 19π neutral radical, as a transient intermediate, for the formation of a unique 18π aromatic monocationic species. Spectroscopic and structural characterization revealed the substituent dependent macrocycle oxidation unfamiliar to the chemistry of antiaromatic isophlorinoids.