New optical brightening agents and photographic materials which contain in at least one layer these brightening agents are provided. The compounds have the general formula ##STR1## wherein R.sub.1 and R.sub.3 are hydrogen or methyl, R.sub.2 and R.sub.4 are alkyl R.sub.5 is hydrogen, alkyl, aryl, aralkyl, X is --NH--, --O-- or --S--, L.sub.1 and L.sub.2 are alkylene oxide chains and M.sup..sym. is a hydrogen or an alkali metal cation.These brightening agents enhance the brightness in the white areas of photographic print materials.