Patent ID: 8920780

Claim:
Compounds of formula (I) R—N(CHO)—X—N(R 3 )—R (I) Formula (I) and salts or optical active isomers thereof, wherein X denotes a C 3 to C 8 straight or branched alkylene moiety optionally with one or two CH 2 moieties replaced by oxygen atoms, sulphur atoms or NR 1 groups and wherein the alkylene moiety optionally is substituted by up to six —OR 1 groups; R 1 denotes a hydrogen or a C 1 to C 4 straight or branched alkyl group; R 3 denotes a formyl moiety; and each R independently is the same or different and denote a triiodinated phenyl group further substituted by two groups R 2 wherein each R 2 is the same or different and denotes a hydrogen atom or a non-ionic hydrophilic moiety, provided that at least one R 2 group in the compound of formula (I) is a hydrophilic moiety.