Patent ID: 7371877

Claim:
A compound represented by the following general formula (IB) or a salt thereof: wherein Ar 11 and Ar 12 each independently represents a hydrogen atom or an aryl group having at least one iodine atom as a substituent, said aryl group being selected from the group consisting of an anthracenyl group, a naphthalenyl group and a phenyl group, and provided that Ar 11 and Ar 12 do not simultaneously represent a hydrogen atom; L 11 and L 12 each independently represents a divalent bridging group whose main chain contains 6 or more carbon atoms, selected from the group consisting of —(CH 2 ) n —O—, —(CH 2 ) m —S—CH 2 —, —(CH 2 ) m —(C═O)O—, —(CH 2 ) m —(C═O)NH—, —(CH 2 ) m —O(C═O)—, —(CH 2 ) m —NH(C═O)—, —(CH 2 ) p —NH(C═O)—(CH 2 ) 2 —O—, —(CH 2 )—CH 2 —CH═CH—(CH 2 ) q —O—, —(CH 2 ) m —CH(CH 3 )—O—and —CH 2 CH═CH(CH 2 ) 8 —, wherein n represents an integer of 6 to 30; m represents an integer of 5 to 29; p represents an integer of 4 to 28; and q represents an integer of 3 to 27; R 11 represents a hydrogen atom or an alkyl group containing 2 to 20 carbon atoms and having a functional group containing at least one heteroatom as a substituent, said functional group being selected from the group consisting of an amino group (including a quaternary ammonium group), a hydroxyl group, an alkoxyl group, an acylamino group, an aminocarbonyl group, a carboxyl group, a sulfoxy group, a thiol group, a thioether group, an alkoxycarbonyl group, an aryloxycarbonyl group and an acyloxy group.