A compound of formula: wherein: B is -CH 2 CH 2 -, -CH CH 2 -, - trans -CH=CH-, -C≡C-, phenyl, optionally substituted with one or more R 8 R 2 is -H or -(C 1 -C 6)alkyl; R 3 is -CH 3, CH 2 R 7, COOR 12, -CHO-, -CH 2 OR 12,-CH 2 SH, -CH 2 NH 2, -CH 2 N 3,-CH 2 NH, -CH=N, -CH=N(NH 2), -CH 2 F,-CH 2 Cl,-CH 2 Br, -CH (C 6 H 5),-CH (C 6 H 4 R 8) or -CH 2 OP 2 OR 4; R 4 is -H, -CH 3, -(CH 2) 2 N(CH 3) 3 +, or -phenyl, optionally substituted with one or more R 8; each R 5 is independently -H; -(C 1 -C 10)alkyl, -(C 2 -C 10)alkenyl, or -(C 2 -C 10)alkynyl, each of which is unsubstituted or substituted with one or more R 9; -halo; -OH; -NO 2; -C OH; -C NH 2; -C NHR 7; -C N-CH 2 -R 7; -OR 10; -C R 10; -C CF 3; -C NR 10; -C R 10; -OC R 10; -C OR 10; or -N(R 10) 2; R 6 is -H, -(C 1 -C 16)alkyl, -(C 2 -C 16)alkenyl, -(C 2 -C 16)alkynyl, each of which, other than -H, is unsubstituted or substituted with one or more R 9; R 7 is -five-membered monocyclic N-, O- or S-based heterocycle; or a -six-membered monocyclic N-, O- or S-based heterocycle; each of which can be unsubstituted or substituted with one or more R 9; R 8 is -(C 1 -C 6)alkyl; -C R 10; -halo, -NO 2, -OH; -NH 2; -NH(R 10), or -N(R 10) 2; R 9 is -halo; -OH; -C (R 10); -CF 3; -NH 2; -NH(R 10); or -N(R 10) 2; or -phenyl, unsubstituted or substituted with one or more -R 8; R 10 is -(C 1 -C 6)alkyl; R 12 is -H, -(C 1 -C 20)alkyl, -(C 2 -C 20)alkenyl, glucose or galactose; a is an integer from 0 to 26; b is 0 or 1; c is 0 or 1; e is 0 or 1; f is an integer from 0 to 20; X is -C -, -C -, -CH(R 10)-, -C(=NH)-, or -N -; Y is -N -, -O-, -C -, -CH(R 10)-, -CH 2 C -, or -CH 2 CH(R 10)-; and M - is a counter anion. B is -CH 2 CH 2 -, -CH CH 2 -, - trans -CH=CH-, -C≡C-, phenyl, optionally substituted with one or more R 8 R 2 is -H or -(C 1 -C 6)alkyl; R 3 is -CH 3, CH 2 R 7, COOR 12, -CHO-, -CH 2 OR 12,-CH 2 SH, -CH 2 NH 2, -CH 2 N 3,-CH 2 NH, -CH=N, -CH=N(NH 2), -CH 2 F,-CH 2 Cl,-CH 2 Br, -CH (C 6 H 5),-CH (C 6 H 4 R 8) or -CH 2 OP 2 OR 4; R 4 is -H, -CH 3, -(CH 2) 2 N(CH 3) 3 +, or -phenyl, optionally substituted with one or more R 8; each R 5 is independently -H; -(C 1 -C 10)alkyl, -(C 2 -C 10)alkenyl, or -(C 2 -C 10)alkynyl, each of which is unsubstituted or substituted with one or more R 9; -halo; -OH; -NO 2; -C OH; -C NH 2; -C NHR 7; -C N-CH 2 -R 7; -OR 10; -C R 10; -C CF 3; -C NR 10; -C R 10; -OC R 10; -C OR 10; or -N(R 10) 2; R 6 is -H, -(C 1 -C 16)alkyl, -(C 2 -C 16)alkenyl, -(C 2 -C 16)alkynyl, each of which, other than -H, is unsubstituted or substituted with one or more R 9; R 7 is -five-membered monocyclic N-, O- or S-based heterocycle; or a -six-membered monocyclic N-, O- or S-based heterocycle; each of which can be unsubstituted or substituted with one or more R 9; R 8 is -(C 1 -C 6)alkyl; -C R 10; -halo, -NO 2, -OH; -NH 2; -NH(R 10), or -N(R 10) 2; R 9 is -halo; -OH; -C (R 10); -CF 3; -NH 2; -NH(R 10); or -N(R 10) 2; or -phenyl, unsubstituted or substituted with one or more -R 8; R 10 is -(C 1 -C 6)alkyl; R 12 is -H, -(C 1 -C 20)alkyl, -(C 2 -C 20)alkenyl, glucose or galactose; a is an integer from 0 to 26; b is 0 or 1; c is 0 or 1; e is 0 or 1; f is an integer from 0 to 20; X is -C -, -C -, -CH(R 10)-, -C(=NH)-, or -N -; Y is -N -, -O-, -C -, -CH(R 10)-, -CH 2 C -, or -CH 2 CH(R 10)-; and M - is a counter anion.