Table 1. Spectral Properties of HDyes^a.

										intra-	extra-
name	X	R1	R2	λabs [nm]	λem [nm]	ε [104 (M cm)−1]	ΦF	D0.5	turn-on	cellular application
o-TzR (26)	O	H	H	557	583	5.52	0.003	-	95	-	-
				(557)	(582)	(7.41)	(0.447)
o-TzSiR	SiMe2	H	H	652	671	2.16	0.007	-	45	-	-
HD555 (27)	O	H	CO2H	555	581	5.10	0.004	17	113/123b	+	+
				(556)	(583)	(10.0)	(0.571)	(19)
HD5Slx	O	CO2H	H	561	588	7.70	0.007	-	45	-	+
HD653 (28)	SiMe2	H	CO2H	653d	676d	4.86d	0.022d	60	50b	+	+
				(652d)	(674d)	(5.92d)	(0.477d)	(63)
HD654x	SiMe2	CO2H	H	654	673	12.5	0.007	-	33	-	+
sb-HD656 (29)	SiMe2	H	CH2OH	656c	676c	11.4c	0.026c	-	9.0c	+	+
				(656c)	(677c)	(10.4c)	(0.310c)

^aAll measurements were performed in phosphate-buffered saline (PBS pH 7.4) and turn-on experiments with 15 eq BCN unless noted otherwise. Properties of respective BCN cycloadducts of the dyes listed in parentheses (see Figure S9 for all structures and Figure S10 for spectra). The assignment of the substituents refers to the general structure in Figure 1a.

^b10 eq of EGFP–HaloTag–BCN.

^cSodium phosphate buffer pH 3.5.

^d50 mM SDS in PBS pH 7.4.