Combined experimental and theoretical insights into the solvent-dependent photochromic properties of nitrospiropyrans.

ABSTRACT: Spiropyrans exhibit reversible photochromism that strongly depends on solvent polarity; yet a quantitative understanding of this relationship remains incomplete. Here we combine detailed spectroscopic and kinetic experiments with ab initio calculations to investigate 5'-methoxy-1',3',3'-trimethyl-6-nitrospiro[chromene-2,2'-indoline] (SP). Ultraviolet irradiation at 368 nm populates the S₃ (¹ππ*) state, initiating the ring-opening reaction to the merocyanine (MC) form, which is subsequently followed by thermal ring-closing. Theoretical calculations indicate that photoexcited SP undergoes nonradiative relaxation to the S₁ charge-transfer state, from which the system reaches the ground state via a ring-opened conical intersection. Experimental kinetics studies have revea

SUBMITTER: Sobolewska A 

PROVIDER: S-EPMC12749598 | biostudies-literature | 2025 Nov

REPOSITORIES: biostudies-literature