Monomers,dimers, and tetramers of 1- and 2-naphthoic acids

The absorption and emission spectra of 1- and 2-naphthoic acids and a number of their derivatives have been investigated. The S₁, T₁, and S₀ energy levels of solvent H-bonded monomers and internally H-bonded dimers are affected by the type of H-bonding, by periinteractions, by steric factors provided by substituent groups, and by solvent effects. The excimer fluorescence of 1-naphthoic acid has been detected and is the sole fluorescece of the crystal; it is attributed to a tetrameric sandwich complex of two dimers. The 1-naphthoic acid crystal also exhibits delayed excimer flurescence of a triplet-triplet annihilative type.