Ultra bright dimeric or polymeric dyes with spacing linker groups

A compound having the following structure (IIB):

• or a stereoisomer, salt or tautomer thereof, wherein:
• G is, at each occurrence, independently a reactive functional group capable of forming a covalent bond with a complementary reactive group, the reactive functional group is selected from the group consisting of:
• an aldehyde, oxime, hydrazone, alkyne, amine, azide, acylazide, acylhalide, nitrile, nitrone, sulfhydryl, disulfide, sulfonyl halide, isothiocyanate, imidoester, activated ester, ketone, α, β-unsaturated carbonyl, alkene, maleimide, a-haloimide, epoxide, aziridine, tetrazine, tetrazole, phosphine, biotin and thiirane;
• L1a is, at each occurrence, independently an alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene or heteroatomic linker;
• L2 and L3 are, at each occurrence, independently an optional alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene or heteroatomic linker;
• R1 is, at each occurrence, independently H, alkyl or alkoxy;
• R2 and R3 are each independently OH, SH, alkyl, alkoxy, alkylether, heteroalkyl, —OP(═Ra)(Rb)Rc, Q or L′;
• R4 is, at each occurrence, independently OH, SH, O−, S−, ORd, SRd;
• R5 is, at each occurrence, independently oxo, thioxo or absent;
• Ra is O or S;
• Rb is OH, SH, O−, S−, ORd or SRd;
• Rc is OH, SH, O−, S−, ORd, OL′, SRd, alkyl, alkoxy, alkylether, alkoxyalkylether, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether or thiophosphoalkylether;
• Rd is a counter ion;
• Q is, at each occurrence, independently a moiety comprising a reactive group, or protected analogue thereof, capable of forming a covalent bond with an analyte molecule, targeting moiety, a solid support or a complementary reactive group Q′;
• L′ is, at each occurrence, independently a linker comprising a covalent bond to Q, a linker comprising a covalent bond to a targeting moiety, a linker comprising a covalent bond to an analyte molecule, a linker comprising a covalent bond to a solid support, a linker comprising a covalent bond to a solid support residue, a linker comprising a covalent bond to a nucleoside;
• m is, at each occurrence, independently an integer of zero or greater, wherein at least one occurrence of m is an integer of one or greater;
• n is an integer of one or greater;
• and
• z is an integer from 2 to 100.