The present invention concerns novel 2-hydroxybenzophenone derivatives and metal complexes thereof of the formula: ##STR1## wherein Z.sub.1, Z.sub.2, Y.sub.1 and Y.sub.2 are each, independently, hydrogen or a substituent, at least one of Y.sub.1 and Y.sub.2 being a group ##STR2## wherein, R.sub.1 is alkyl R.sub.2 is hydrogen or a substituent andA is oxygen, sulphur or ##STR3## The compounds are useful for stabilizing organic material, e.g. plastics, against degradation under the influence of U.V. radiation.