Compound and labeled biological substance using the same

A compound represented by General Formula (1),

• in the formula, R1 to R6 represent an alkyl group which may have a substituent or —(CH2—CH2—O)m—R21, where m is 1 to 50, and R21 represents an alkyl group which may have a substituent,
• R11 to R13 represent a hydrogen atom, an alkyl group, an aryl group, a heteroaryl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an amino group, or a halogen atom, where adjacent groups may be bonded to each other to form a 5-membered or 6-membered ring,
• R22 to R29 represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a sulfo group, a sulfonamide group, an alkoxycarbonyl group, an acyloxy group, a carbamoyl group, an acylamino group, a nitro group, or a halogen atom, where adjacent groups may be bonded to each other to form a fused ring,
• n is an integer of 1 to 3,
• provided that one selected from R1, R2, R5, and R22 to R25 and one selected from R3, R4, R6, and R26 to R29 are bonded through a linking group LL, the linking group LL represents a divalent linking group having 1 to 100 carbon atoms, provided that the linking group LL does not have any group selected from an aromatic hydrocarbon ring, a sulfo group, and a phosphono group,
• at least one of R1 to R6 and R22 to R29 contains a structure represented by —(CH2—CH2—O)m—, where m has the same meaning as m described above, and
• the compound represented by General Formula (1) is a neutral compound and contains at least one substituent capable of being bonded to a carboxy group or a biological substance.