On the first triplet state of benzotriazole-like ultraviolet stabilizers

A benzotriazole-like ultraviolet stabilizer (Tinuvin-327) is shown to exhibit phosphorescence. The triplet responsible for the phosphorescence, which is centred at 720 nm, is that for the transferred form of the compound. This triplet deactivates the triplet manifold in a highly efficient manner, thus endowing this type of compound with a high stability.