Contribution of Aggregate States and Energetic Disorder to a Squaraine System Targeted for Organic Photovoltaic Devices

Squaraine dyes have significant potential for use in organic photovoltaic devices because their chemical and packing structure tunability leads to a broad solid state panchromaticity. Nevertheless, broadening of the spectrum does not always give rise to increasing power conversion efficiencies. Furthermore, the same processing strategy used to make devices from different squaraines does not lead to the same optimized performance. In this work, by varying the environmental conditions of a set of anilinic squaraines, we demonstrate that spin-cast thin films are made up of a complex set of states, with each state contributing differently to the overall device efficiency. We demonstrate crystallochromy in that small changes in the packing structure give rise to dramatically different absorption spectra. Through a remarkable comparison between squaraines in poly­(methyl methacrylate) solid solution and squaraine:PC₆₀BM blends, we also show long-range and orientational disorder broadening, which distorts the ability to correlate qualitative spectroscopic assessment with an understanding of the device mechanism. We conclude that a full quantitative assessment of the populations of each excited state must be carried out in order to make progress toward an improved understanding of each state’s contribution to charge transfer at the bulk heterojunction interface

Pyrrolobenzodiazepine Dimer Antibody–Drug Conjugates: Synthesis and Evaluation of Noncleavable Drug-Linkers

Three rationally designed pyrrolobenzodiazepine (PBD) drug-linkers have been synthesized via intermediate <b>19</b> for use in antibody–drug conjugates (ADCs). They lack a cleavable trigger in the linker and consist of a maleimide for cysteine antibody conjugation, a hydrophilic spacer, and either an alkyne (<b>6</b>), triazole (<b>7</b>), or piperazine (<b>8</b>) link to the PBD. In vitro IC₅₀ values were 11–48 ng/mL in HER2 3+ SK-BR-3 and KPL-4 (<b>7</b> inactive) for the anti-HER2 ADCs (HER2 0 MCF7, all inactive) and 0.10–1.73 μg/mL (<b>7</b> inactive) in CD22 3+ BJAB and WSU-DLCL2 for anti-CD22 ADCs (CD22 0 Jurkat, all inactive at low doses). In vivo antitumor efficacy for the anti-HER2 ADCs in Founder 5 was observed with tumor stasis at 0.5–1 mg/kg, 1 mg/kg, and 3–6 mg/kg for <b>6</b>, <b>8</b>, and <b>7</b>, respectively. Tumor stasis at 2 mg/kg was observed for anti-CD22 <b>6</b> in WSU-DLCL2. In summary, noncleavable PBD-ADCs exhibit potent activity, particularly in HER2 models