Benzothiazole dyes

A composition comprising a compound of Formula (I):

• or a salt thereof, wherein:
• n is 1-4;
• m is 0-4;
• X is oxygen or sulfur;
• R1 is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, or substituted or unsubstituted heteroaryl;
• R2 is, independently for each occurrence, halo, —OR5, —SR5, —N(R5)2, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl;
• wherein two adjacent R2 groups may combine to form a fused substituted or unsubstituted aryl, a fused substituted or unsubstituted heteroaryl, a fused substituted or unsubstituted carbocyclyl, or a fused substituted or unsubstituted heterocyclyl;
• R3 is substituted or unsubstituted alkyl;
• R4 is, independently for each occurrence, halo, —NO2, —OR6, —SR6, —N(R6)2, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl;
• R5 is, independently for each occurrence, hydrogen, substituted or unsubstituted alkyl, nitrogen protecting group when attached to a nitrogen, oxygen protecting group when attached to an oxygen, or a sulfur protecting group when attached to a sulfur, or when R2 is —N(R5)2, two instances of R5 may be joined to form a substituted or unsubstituted heterocyclyl or a substituted or unsubstituted heteroaryl;
• and
• R6 is, independently for each occurrence, hydrogen, substituted or unsubstituted alkyl, nitrogen protecting group when attached to a nitrogen, oxygen protecting group when attached to an oxygen, or a sulfur protecting group when attached to a sulfur.

A method of detecting the presence or absence of an analyte in a test sample, comprising contacting the test sample with a compound of Formula (I):

• or a salt thereof, in the presence of an energy (E1) and detecting emission of an energy (E2) from the sample, wherein:
• n is 1-4;
• m is 0-4;
• X is oxygen or sulfur;
• R1 is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, or substituted or unsubstituted heteroaryl;
• R2 is, independently for each occurrence, halo, —OR5, —SR5, —N(R5)2, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl;
• wherein two adjacent R2 groups may combine to form a fused substituted or unsubstituted aryl, a fused substituted or unsubstituted heteroaryl, a fused substituted or unsubstituted carbocyclyl, or a fused substituted or unsubstituted heterocyclyl;
• R3 is substituted or unsubstituted alkyl;
• R4 is, independently for each occurrence, halo, —NO2, —OR6, —SR6, —N(R6)2, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl;
• R5 is, independently for each occurrence, hydrogen, substituted or unsubstituted alkyl, nitrogen protecting group when attached to a nitrogen, oxygen protecting group when attached to an oxygen, or a sulfur protecting group when attached to a sulfur, or when R2 is —N(R5)2, two instances of R5 may be joined to form a substituted or unsubstituted heterocyclyl or a substituted or unsubstituted heteroaryl;
• and
• R6 is, independently for each occurrence, hydrogen, substituted or unsubstituted alkyl, nitrogen protecting group when attached to a nitrogen, oxygen protecting group when attached to an oxygen, or a sulfur protecting group when attached to a sulfur.