A fluorochrome compound represented by: or a salt thereof, wherein: X 1 and X 2 each independently are selected from the group consisting of C(CH 2 K 1)(CH 2 K 2), O, S, and Se, wherein K 1 and K 2 each independently are selected from the group consisting of H and C 1 -C 20 alkyl; wherein K 1 and K 2 together can optionally form part of a cyclic ring; R 1 and R 2 each independently are selected from the group consisting of H, C 1-20 alkyl, alkylaryl, and -R 9 T 1, wherein Rg is independently selected from the group consisting of C 1 -C 20 alkyl, aryl, alkylaryl, and -(CH 2 -O-CH 2) y CH 2, wherein y is an integer selected from 1 to 100, and T 1 is a linker moiety capable of forming a covalent bond with a biomolecule and is selected from the group consisting of -NH 2, -OH, -SH, -SO 3 H, carboxyl, -COCl, - O R 13, -CONHNH 2, substituted and unsubstituted N-hydroxysuccinimido esters, substituted and unsubstituted N-hydroxysulfosuccinimido esters, nitro- or fluoro-phenol esters, -NCS, -CHO, azide, -COCH 2 l, phthalamido, and maleimide, wherein R 13 is selected from the group consisting of H, alkyl and aryl; X 3 is selected from the group consisting of H, halogen, -T 2 R 10,-T 2 R 9 T 1, and -R 9 T 1, wherein T 2 is selected from the group consisting of S, O, and NR', R 10 is selected from the group consisting of H, C 1-20 alkyl, aryl, arylalkyl; X 4 and X 5 each independently are selected from the group consisting of (CK 1 K 2) i and NR', wherein i is an integer selected from 1 to 7, and R' is selected from the group consisting of H and alkyl; W 1 and W 2 each represent nonmetal atoms as part of an aryl moiety; n 1 and n 2 each independently are selected from 0 to 4; R 3, R 4, R 5 and R 6 each independently are selected from the group consisting of H, halogen, carboxylate, carboxylic acid, carboxylic ester, amine, amide, sulfonamide, hydroxyl, O-alkyl, S-alkyl, alkyl, sulfonic acid, sulfonate, a phosphoryl, SO 2 NR 7 -Q-CHR 8 -[(CH 2) m -Y-(CH 2) p - k] h (CH 2) d T 1, and -R 9 T 1, wherein R 7 independently is selected from the group consisting of C 1 -C 20 alkyl, aryl, alkylaryl, R 8 independently is selected from the group consisting of H, C 1 -C 20 alkyl, aryl, alkylaryl and arylalkyl; R 7 and R 8, when taken in combination, optionally form a 4-, 5-, 6- or 7-member, optionally substituted, saturated or unsaturated ring, Q independently is selected from the group consisting of a bond, carbonyl, C 1 -C 6 alkyl, and C 1 -C 6 cycloalkyl, Y independently is selected from the group consisting of a bond, -SO 2 NR 1 -, -O-, -COO-, and -CONR'-, h is an integer selected from 0 to 70, k is 0 or 1, d is an integer from 0 to 12, m is an integer from 0 to 12, and p is an integer from 0 to 12. X 1 and X 2 each independently are selected from the group consisting of C(CH 2 K 1)(CH 2 K 2), O, S, and Se, wherein K 1 and K 2 each independently are selected from the group consisting of H and C 1 -C 20 alkyl; wherein K 1 and K 2 together can optionally form part of a cyclic ring; R 1 and R 2 each independently are selected from the group consisting of H, C 1-20 alkyl, alkylaryl, and -R 9 T 1, wherein Rg is independently selected from the group consisting of C 1 -C 20 alkyl, aryl, alkylaryl, and -(CH 2 -O-CH 2) y CH 2, wherein y is an integer selected from 1 to 100, and T 1 is a linker moiety capable of forming a covalent bond with a biomolecule and is selected from the group consisting of -NH 2, -OH, -SH, -SO 3 H, carboxyl, -COCl, - O R 13, -CONHNH 2, substituted and unsubstituted N-hydroxysuccinimido esters, substituted and unsubstituted N-hydroxysulfosuccinimido esters, nitro- or fluoro-phenol esters, -NCS, -CHO, azide, -COCH 2 l, phthalamido, and maleimide, wherein R 13 is selected from the group consisting of H, alkyl and aryl; R 13 is selected from the group consisting of H, alkyl and aryl; X 3 is selected from the group consisting of H, halogen, -T 2 R 10,-T 2 R 9 T 1, and -R 9 T 1, wherein T 2 is selected from the group consisting of S, O, and NR', R 10 is selected from the group consisting of H, C 1-20 alkyl, aryl, arylalkyl; X 4 and X 5 each independently are selected from the group consisting of (CK 1 K 2) i and NR', wherein i is an integer selected from 1 to 7, and R' is selected from the group consisting of H and alkyl; W 1 and W 2 each represent nonmetal atoms as part of an aryl moiety; n 1 and n 2 each independently are selected from 0 to 4; R 3, R 4, R 5 and R 6 each independently are selected from the group consisting of H, halogen, carboxylate, carboxylic acid, carboxylic ester, amine, amide, sulfonamide, hydroxyl, O-alkyl, S-alkyl, alkyl, sulfonic acid, sulfonate, a phosphoryl, SO 2 NR 7 -Q-CHR 8 -[(CH 2) m -Y-(CH 2) p - k] h (CH 2) d T 1, and -R 9 T 1, wherein R 7 independently is selected from the group consisting of C 1 -C 20 alkyl, aryl, alkylaryl, R 8 independently is selected from the group consisting of H, C 1 -C 20 alkyl, aryl, alkylaryl and arylalkyl; R 7 and R 8, when taken in combination, optionally form a 4-, 5-, 6- or 7-member, optionally substituted, saturated or unsaturated ring, Q independently is selected from the group consisting of a bond, carbonyl, C 1 -C 6 alkyl, and C 1 -C 6 cycloalkyl, Y independently is selected from the group consisting of a bond, -SO 2 NR 1 -, -O-, -COO-, and -CONR'-, h is an integer selected from 0 to 70, k is 0 or 1, d is an integer from 0 to 12, m is an integer from 0 to 12, and p is an integer from 0 to 12.