Compound and labeled biological substance using the same

A compound comprising:

• at least two phosphor moieties;
• and
• a structure represented by General Formula (I),
• in the formula, X1 to X3 represent —O—, —S—, >NR1, or >CR2R3,
• R1 to R3 represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, -(L-O)gRE, an acyl group, —NR8R9, or —OR10,
• R8 to R10 represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an aryl group, a heteroaryl group, or -(L-O)gRE, where L represents an alkylene group, RE represents a hydrogen atom or an alkyl group, and g is 1 to 24,
• La and Lb represent a single bond or a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, —O—, —S—, >C═O, >NRA, >S═O, >S(═O)2, and >P(═O)ORB, where RA and RB represent a hydrogen atom or a substituent,
• n is an integer of 2 or more,
• provided that a structure parenthesized in ( )n has at least any one of >NR1 or >CR2R3, and at least one of R1, R2, or R3 contained in the structure parenthesized in ( )n is a group including -(L-O)gRE, and/or at least one of La or Lb is a group having, as a substituent, a group including -(L-O)gRE,
• the -(L-O)gRE in R1 to R3, La, L, and L4, which include -(L-O)gRE, is not bonded to at least any one of a phosphor or a biological substance, and
• * represents a bonding site.