o-hydroxyphenyl-triazine derivatives with formyl substituents were surveyed for the excited state intramolecular proton transfer (ESIPT).The occurrence of ESIPT was confirmed by well-separated emission bands for the derivatives.A low energy change from enol to keto in the excited state explains ESIPT for the derivatives. o-hydroxyphenyl-triazine derivatives with formyl substituents were surveyed for the excited state intramolecular proton transfer (ESIPT). The occurrence of ESIPT was confirmed by well-separated emission bands for the derivatives. A low energy change from enol to keto in the excited state explains ESIPT for the derivatives.