(2-Chloro-3-(2,2-dicyanoethenyl)-2-cyclopentene-1-ylidene)-2,2-dicyanoethane pyridinium salt 124522-11-8 AB 633 Albumin blue 633 Propanedinitrile, ((2-chloro-3-(2,2-dicyanoethenyl)-2-cyclopenten-1-ylidene)methyl)-, compd. with pyridine (1:1)