Experimental and theoretical investigations of prifinium bromide: structural insights, spectroscopic features, topological aspects, and biological properties

Prifinium bromide (PB) was analyzed by experimentally and theoretically. The N3-C7 and C6-C7 bonds exceeded standard values due to hyperconjugation, and steric strain. A potential energy surface scan examined dihedral angles ϕ₁ (N3-C22-C23-H51) and ϕ₂ (C7-N3-C22-C23) to assess conformational stability. Vibrational spectra identified key stretching and deformation modes for C-N, C-H, C-C, CH₂, and CH₃ groups. Carbon and proton chemical shifts confirmed the molecular structure with strong correlation between experimental and theoretical values. Theoretical electronic spectra revealed six transitions (482–382 nm), with the most intense absorption at 473 nm (f = 0.0160) corresponding to the H-2 → L (99%) transition, along with the frontier molecular orbital (FMO) energy gap was 3.0501 eV. The most significant stabilization occurs during the π-π* transition from π(C20-C21) to π*(C16-C17) with an energy of 20.75 kJ/mol, while the quaternary nitrogen (-0.38751 e) accumulates electron density, and the bromine(-0.81746 e) exhibits strong electronegativity and electron withdrawing effects. PB did not meet Muegge’s rule, and its bioavailability score of 0.55 indicates moderate oral absorption, though poor solubility and low GI absorption may limit systemic exposure. Topological analyses were performed to highlight localized, delocalized, and weak interactions of PB. Molecular docking confirmed PB's anticholinergic potential, showing a binding affinity of -8.6 kcal/mol with the 5ZKC M2 muscarinic receptor.