Resonance Energy Transfer Emission Observed in Cocrystal of N,N′‐Bis(3‐imidazol‐1‐ylpropyl)naphthalenediimide with Cinnamic Acid

Abstract Cocrystal of N,N′‐bis(3‐imidazol‐1‐ylpropyl)naphthalenediimide with 3‐hydroxybenzoic acid has parallel stacks among naphthalenediimide rings (A) as ‐A−A‐A−A‐ like arrangement; whereas in packing of 5‐aminoisophthalate (D) salt of N,N′‐bis(3‐imidazol‐1‐ylpropyl) naphthalenediimide has stack of parallel aromatic rings in a manner like ‐A−D‐A−D‐. Parallel stacking patterns among the fluorescent aromatic rings of these adducts influence fluorescence. Fluorescence of solid sample of cocrystal with 3‐hydroxybenzoic acid or salt with 5‐aminoisophthalic acid of N,N′‐bis(3‐imidazol‐1‐ylpropyl)naphthalenediimide is quenched due to Dexter electron transfer. Cocrystal of N,N′‐bis(3‐imidazol‐1‐ylpropyl)naphthalenediimide with cinnamic acid is devoid of parallel stacks among fluorophoric aromatic rings. It shows emission at 547 nm through resonance energy transfer between donor and acceptor components. The original parent components have individual fluorescence emissions at comparable wavelengths but much shorter wavelengths than the wavelength of emission shown by the cocrystal.