Patent ID: 8067602

Claim:
A compound having the structure of the following general formula I: wherein n is 1, 2 or 3; X is C(CH 3 ) 2 , O, S or Se; R 1 and R 2 are each independently selected from at least one of the following: H, OH, C 1-18 a 1 kyl, C 1-6 alkyl-OR 5 , C 1-18 alkylsulfo, phenyl and halogen; R 3 and R 4 are each independently selected from at least one of the following: C 1-18 alkyl-COOR 6 and benzyl, wherein said benzyl is optionally substituted with one or more substituents selected from at least one of the following: halogen, hydroxyl, sulfhydryl, cyano, nitro, alkyl, aryl, alkoxy, heterocyclyl, haloalkyl, amino, alkylamino, amido and carboxyl, provided that R3 and R4 are not simultaneously benzyl or simultaneously C 1-18 alkylCOOR 6 , R 5 is C 1-18 alkyl or H; R 6 is C 1-18 alkyl, H or phenyl, wherein said phenyl is optionally substituted with one or more substituents selected from at least one of the following: halogen, hydroxyl, sulfhydryl, cyano, nitro, alkyl, aryl, alkoxy, heterocyclyl, haloalkyl, amino, alkylamino, amido and carboxyl; and Y − is an anion.