Patent ID: 8383830

Claim:
A compound having the general formula I: wherein R 1 and R 2 are each independently selected from at least one of the following: C 1-18 alkylCOOR 6 , C 1-18 alkylOR 6 and benzyl, wherein said benzyl is optionally substituted with at least one of the following: a substituent selected from halogen, hydroxyl, sulfhydryl, cyano, nitro, alkyl, aryl, alkyloxy, heterocyclyl, haloalkyl, amino, alkylamino, amido and carboxyl, provided that R 1 and R 2 are not all simultaneously benzyl; R 6 in each occurrence is independently selected from at least one of the following: C 1-18 alkyl or phenyl, wherein said phenyl is optionally substituted with a substituent selected from at least one of the following: halogen, hydroxyl, sulfhydryl, cyano, nitro, alkyl, aryl, alkyloxy, heterocyclyl, haloalkyl, amino, alkylamino, amido and carboxyl; X is CH 2 , C(CH 3 ) 2 , O, S or Se; Y is are each independently selected from R 3 , R 4 and R 5 are each independently selected from at least one of the following: H, halogen, cyano, hydroxyl, C 1-18 alkyl, C 1-18 alkylsulphonyl, sulphonyl and C 1-5 alkylCOOR 7 ; R 7 is H or C 1-6 alkyl; and Z − is an anion.