In this work, we investigate the influence of hydrogen donor groups and spacer chain length in N,N \(^{\prime }\) -substituted naphthalenediimides (NDIs) on fluoride binding affinity and redox behavior through combined experimental and theoretical approaches. UV-vis spectroscopy reveals that while benzylic substituents connected via methylene spacers minimally affect optical properties, they significantly modulate \(\pi\) -acidity and reduction potentials. Systematic titrations with \(\text {F}^-\) and the analysis of the absorbance profiles demonstrate that hydrogen donor groups enhance fluoride binding capacity, leading to multi-anion complexes with stoichiometries of 3-5 fluoride ions per NDI. However, binding affinity does not correlate directly with radical formation efficiency. Electronic structure calculations confirm the formation of stable NDI-fluoride complexes and reveal that direct electron transfer from \(\text {F}^-\) to NDIs is thermodynamically unfavorable ( \(\varvec{\Delta G=3.19-3.28}\) eV). Solvent-mediated pathways involving \(\text {DMSO}^{\bullet -}\) approach thermodynamic feasibility but face significant kinetic barriers ( \(\varvec{\Delta G^{\dagger }=1.03}\) eV). To reconcile these contradictions with experimental observations, we explore a photophysical mechanism based on low-lying \(\varvec{\text {p}\rightarrow \pi ^{*}}\) excited states in NDI-DMSO-fluoride complexes, which suggests that photoexcitation could drive barrierless electron transfer pathways with DMSO acting as a scavenger for reactive \(\text {F}^{\bullet }\) radicals. This work demonstrates the complex interplay between structural features, anion binding, and redox chemistry in NDI systems, while identifying key mechanistic uncertainties that warrant further investigation through experimental an theoretical studies. The findings have implications for rational design of NDI-based fluoride sensors and highlight the potential role of photochemical processes in anion-induced electron transfer reactions.
