Silicon-substituted rhodamine dyes and dye conjugates

A compound of formula (I), or a spirolactone form and/or salt thereof:

• wherein:
• R1 is methyl, C2-6 alkyl, vinyl, substituted vinyl,-L1-RA;
• R2 is methyl, C2-6 alkyl, vinyl, substituted vinyl,-L1-RA;
• or R1 and R2 form a ring together with the silicon to which they are attached;
• each L1 is independently a linker;
• each RA independently comprises a reactive ligand, a solubilizing functionality, a carrier molecule, or an antibody;
• R3 is —COOH, SO3−, H, R3a,-L1-RA;
• R3a is
• or —C(O)N(RN3) (RN4);
• RN3 is H, methyl, C2-6 alkyl, or —CH2-A where A is an aryl or heteroaryl substituted with at least one polar or charged group;
• RN4 is -L1-RA, or —(CH2CH2O)q—C(O)O—RB where q is 2, 3, 4, 5, or 6;
• R3b is —OH or —N(RN5)-L3a-RB;
• each L3a is independently a linker;
• RB comprises a reactive ligand, a solubilizing functionality, a carrier molecule, or an antibody;
• RN5 is H, methyl, or C2-6 alkyl;
• R4 is SO3, methyl, chloro, C2-6 alkyl, or H;
• E is SO3, methyl, chloro, C2-6 alkyl, or H;
• R5 is H, methyl, or C2-6 alkyl, or forms a ring with an RN1;
• R6 is H, methyl, or C2-6 alkyl, or forms a ring with an RN2;
• R7 is H, methyl, or C2-6 alkyl, or forms a ring with an RN1;
• R8 is H, methyl, or C2-6 alkyl, or forms a ring with an RN2;
• R9 is SO3″, methyl, chloro, C2-6 alkyl, or H;
• each RN1 is independently H, methyl, C2-4 alkyl, C(O) R10, —C(O) R13, or forms a ring with R5 or R7;
• each RN2 is independently H, methyl, C2-4 alkyl, C(O) R10, —C(O) R13, or forms a ring with R6 or R8;
• R10 is —C(O)—CF3 or —O—CH2-A1 where A1 is an aryl or heteroaryl optionally substituted with at least one R11;
• R11 is methyl, C2-6 alkyl, or —OR12;
• and
• R12 is H, methyl, acetyl (Ac), acetoxymethyl (AM), —PO32-, —PO3(AM)2, or a glycoside;
• R13 is
• where R15 is an oligopeptide, an amino acid sequence, or —OR′ where R′ is acetyl, AM, PO32-, PO3(AM)2, or a glycoside and AM is acetoxymethyl;
• further wherein (i) R2 is not methyl or C2-6 alkyl if R1 is methyl or C2-6 alkyl, or (ii) R3 is R3a or -L1-RA.