Patent ID: 7709653

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, a halogen, and C 1-18 alkylsulfo, provided that R 1 and R 2 are not simultaneously H; R 3 and R 4 are each independently selected from at least one of the following: C 1-18 alkyl and C 1-18 alkylOR 5 , provided that R 3 and R 4 are not simultaneously alkyls when R 2 is a halogen; R 5 is a hydrogen atom, acyl or lower alkyl; and Y − is an anion.