Fluoride ion promoted NH deprotonation of dioxaPhlorin with NIR absorption vs. acid induced facile conversion to aromatic dioxaSapphyrin: Synthesis, spectroscopic and theoretical characterization

Synthesis, spectroscopic and solid state structural proof of hitherto unknown highly stable meso-pyrrole appended expanded dioxaphlorin is reported. The macrocycle was susceptible to NH deprotonation upon TBAF titration leading to NIR absorption with vivid colour change to the naked eye paving the way towards the application as a fluoride ion sensor. Contrarily, efficient conversion to aromatic dioxasapphyrin has been anticipated upon trifluoroacetic acid reaction owing to facile elimination of meso-appended pyrrole ring. The conformational preorganzation and anion induced conformational reorganization owing to the base promoted NH deprotonation are thoroughly investigated by various spectroscopic techniques and DFT level theoretical calculations.