A compound of general formula IIIa or general formula IIIb wherein each of R 1, R 2, R 5, and R 6 is the same or different and is independently selected from the group consisting of aliphatic, heteroaliphatic, sulfoalkyl, heteroaliphatic with terminal SO 3, a PEG group P-L-Z where P is selected from an ethylene glycol group, a diethylene glycol group, and a (poly)ethylene glycol group where the (poly)ethylene glycol group is (CH 2 CH 2 O) s where s is an integer from 3-6 inclusive, a sulfonamide group -L-SO 2 NH-P-L-Z, and a carboxamide group -L-CONH-P-L-Z; each of R 7 and R 8 is the same or different and is independently selected from H, SO 3, a PEG group P-L-Z where P is selected from an ethylene glycol group, a diethylene glycol group, and a (poly)ethylene glycol group where the (poly)ethylene glycol group is (CH 2 CH 2 O) s where s is an integer from 3-6 inclusive, a sulfonamide SO 2 NH-P-L-Z, or a carboxamide -CONH-P-L-Z; where L is selected from the group consisting of a divalent linear (-(CH 2) o -, o = 0 to 15), crossed, or cyclic alkane group optionally substituted by at least one atom selected from the group consisting of oxygen, substituted nitrogen, and/or sulfur; where Z is selected from the group consisting of H, CH 3, alkyl, a heteroalkyl group, NH 2, -COO -, -COOH, -COSH, CO-NH-NH 2, -COF, -COCl, -COBr, -COI, -COO-Su (succinimidyl/sulfosuccinimidyl), -COO-STP (4-sulfo-2,3,5,6-tetrafluorophenyl),-COO-TFP (2,3,5,6-tetrafluorophenyl), -COO-benzotriazole, -CO-benzotriazole, -CONR'-CO-CH 2 -I, -CONR'R", -CONR'-L-COO -, -CONR'-L-COOH, -CONR'-L-COO-Su, -CONR'-L-COO-STP, -CONR'-L-COO-TFP, -CONR'-L-CONR" 2, --CONR'-L-CO-NH-NH 2,-CONR'-L-OH, -CONR'-L-O-phosphoramidite, -CONR'-L-CHO, -CONR'-L-maleimide, and -CONR'-L-NH-CO-CH 2 -I; R' and R" is selected from the group consisting of H, aliphatic, and heteroaliphatic; X is selected from the group consisting of -OH,, -NH-NH 2, -NHS (hydroxysuccinimidyl/sulfosuccinimidyl), -O-TFP (2,3,5,6-tetrafluorophenoxy), -O-STP (4-sulfo-2,3,5,6-tetrafluorophenoxy), -NR-L-OH, -NR-L-NH-NH 2, -NR-L-CO 2 H, -NR-L-CO-NHS, -NR-L-CO-STP, -NR-L-CO-TFP, -NR-L-maleimide, and -NR-L-NH-CO-CH2-I, where R is -H, aliphatic, or heteroaliphatic; Kat is a number of Na +, K +, Ca 2+, ammonia, or other cation(s) needed to compensate the negative charge brought by the cyanine; m is an integer from 0 to 5 inclusive; p is an integer from 0 to 6 inclusive and n is an integer of 1 to 3 inclusive; with the proviso that at least one of R 1, R 2, R 5, R 6, R 7, and R 8 contains a PEG group, wherein the compound is covalently coupled to a biomolecule (B m) via X in general formula IIIa or the terminal -OH group in general formula IIIb. each of R 1, R 2, R 5, and R 6 is the same or different and is independently selected from the group consisting of aliphatic, heteroaliphatic, sulfoalkyl, heteroaliphatic with terminal SO 3, a PEG group P-L-Z where P is selected from an ethylene glycol group, a diethylene glycol group, and a (poly)ethylene glycol group where the (poly)ethylene glycol group is (CH 2 CH 2 O) s where s is an integer from 3-6 inclusive, a sulfonamide group -L-SO 2 NH-P-L-Z, and a carboxamide group -L-CONH-P-L-Z; each of R 7 and R 8 is the same or different and is independently selected from H, SO 3, a PEG group P-L-Z where P is selected from an ethylene glycol group, a diethylene glycol group, and a (poly)ethylene glycol group where the (poly)ethylene glycol group is (CH 2 CH 2 O) s where s is an integer from 3-6 inclusive, a sulfonamide SO 2 NH-P-L-Z, or a carboxamide -CONH-P-L-Z; where L is selected from the group consisting of a divalent linear (-(CH 2) o -, o = 0 to 15), crossed, or cyclic alkane group optionally substituted by at least one atom selected from the group consisting of oxygen, substituted nitrogen, and/or sulfur; where Z is selected from the group consisting of H, CH 3, alkyl, a heteroalkyl group, NH 2, -COO -, -COOH, -COSH, CO-NH-NH 2, -COF, -COCl, -COBr, -COI, -COO-Su (succinimidyl/sulfosuccinimidyl), -COO-STP (4-sulfo-2,3,5,6-tetrafluorophenyl),-COO-TFP (2,3,5,6-tetrafluorophenyl), -COO-benzotriazole, -CO-benzotriazole, -CONR'-CO-CH 2 -I, -CONR'R", -CONR'-L-COO -, -CONR'-L-COOH, -CONR'-L-COO-Su, -CONR'-L-COO-STP, -CONR'-L-COO-TFP, -CONR'-L-CONR" 2, --CONR'-L-CO-NH-NH 2,-CONR'-L-OH, -CONR'-L-O-phosphoramidite, -CONR'-L-CHO, -CONR'-L-maleimide, and -CONR'-L-NH-CO-CH 2 -I; R' and R" is selected from the group consisting of H, aliphatic, and heteroaliphatic; X is selected from the group consisting of -OH,, -NH-NH 2, -NHS (hydroxysuccinimidyl/sulfosuccinimidyl), -O-TFP (2,3,5,6-tetrafluorophenoxy), -O-STP (4-sulfo-2,3,5,6-tetrafluorophenoxy), -NR-L-OH, -NR-L-NH-NH 2, -NR-L-CO 2 H, -NR-L-CO-NHS, -NR-L-CO-STP, -NR-L-CO-TFP, -NR-L-maleimide, and -NR-L-NH-CO-CH2-I, where R is -H, aliphatic, or heteroaliphatic; Kat is a number of Na +, K +, Ca 2+, ammonia, or other cation(s) needed to compensate the negative charge brought by the cyanine; m is an integer from 0 to 5 inclusive; p is an integer from 0 to 6 inclusive and n is an integer of 1 to 3 inclusive; with the proviso that at least one of R 1, R 2, R 5, R 6, R 7, and R 8 contains a PEG group, wherein the compound is covalently coupled to a biomolecule (B m) via X in general formula IIIa or the terminal -OH group in general formula IIIb.