Tuning the Electronic Excitation of Meta Nitrophenolate Anions to the Biological Transparency Window by Amino Substitution
Year: 2025
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide Nitrophenolate anions are molecules that release nitric oxide (NO) after electronic excitation. This class of molecules is particularly interesting for potential applications in skin cancer treatment, which requires the use of wavelengths in the biological transparency window. Among the various isomers, meta NP – ( m NP – ) has the lowest excitation energy with a band origin at 625 nm. Here, using cryogenic photodissociation spectroscopy, we studied the effect on the electronic spectroscopy of m NP – of methyl and amino electron-donating groups at the ortho position relative to NO 2 . Unlike the bare m NP – anion, all compounds exhibit broad photodissociation spectra, revealing significant geometric changes between the S 0 and S 1 (ππ NO2 *) states. While methyl substitution causes a blue shift of the absorption band maximum, amino-substituted mNP – anions show large red shifts, with the absorption band starting below 800 nm for 4NH 2 m NP –, i.e ., in the biological transparency window, while still leading to NO photorelease. The spectral shifts induced by the substituents are interpreted by comparison with coupled-cluster calculations performed in the ground state and the first excited state. These electron-donating groups in the ortho position relative to NO 2 perturb the electronic properties of m NP – through opposing steric and electrostatic effects.
Language: English
Subfield: Physical and Theoretical Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W4415812798