Fluorescent Sensing of Guanine and Guanosine Monophosphate with Conjugated Receptors Incorporating Aniline and Naphthyridine Moieties

Ethyne-linked naphthyridine–aniline conjugated molecules are selective sensors of decylguanine in dichloromethane and guanosine monophosphate in water (K_ass = 16 000 M^–1). The 2-acetamido-1,8-naphthyridine moiety binds with guanine in a DAA–ADD triply hydrogen-bonded motif. The aniline moiety enhances an electron-donating effect, and the substituent is tuned to attain extra hydrogen bonds, π–π stacking, and electrostatic interactions. The proposed binding modes are supported by a Job plot, ESI-MS, ¹H NMR, UV–vis, and fluorescence spectral analyses.