Patent ID: 8323619

Claim:
Compounds of formula (I) R A —CO—N(R 2 )—(CR 1 2 ) n —N(R 5 )—R B Formula (I) and salts or optical active isomers thereof, wherein each R 1 independently are the same or different and denotes a hydrogen atom, a hydroxyl group, a C 1 to C 4 straight of branched alkyl group or a C 1 to C 4 straight of branched oxyalkyl group; R 2 denotes a hydrogen atom or a C 1 to C 4 straight of branched alkyl group; R 5 denotes a group of formula —CO—R 4 where R 4 denotes a hydrogen atom or a C 1 to C 4 straight of branched alkyl group optionally substituted by 1 to 4 hydroxyl moieties; R A and R B independently are the same or different and denote a triiodinated phenyl group; and n denotes a positive integer of 1 to 6.