A naphthopyran-rhodamine based fluorescent and colorimetric chemosensor for recognition of common trivalent metal ions and Cu 2+ ions

•The naphthopyran and rhodamine dyad was prepared and well characterized.•The new dyad showed excellent photochromic performance.•The dyad solution displayed markedly fluorescent enhancement in the presence of trivalent metal ions.•The dyad showed the ability of colorimetric chemodosimeter for Cu2+ ions upon UV irradiation.•The dyad was successfully applied for photoprinting and UV strength measurement.