 Naphthalimide-Fused Dipyrrins: Tunable Halochromic Switches and Photothermal NIR-II Dyes

Primary source: pubmed.ncbi.nlm.nih.gov/35174648/

Verified locator: Primary indexed abstract, PMID 35174648: first protonation changes conformation and chromophore/substituent coupling, with large halochromic shifts in selected derivatives.

Open-access primary full text: pmc.ncbi.nlm.nih.gov/articles/PMC9259717/ , DOI 10.1002/advs.202105886. Figures 3–4 and their captions identify acid titrations in dichloromethane using trifluoroacetic acid, with sulfuric acid used for some higher protonation stages. The results show derivative-dependent multistage spectral responses rather than a universal two-species aqueous titration.