Table 1.

Photophysical properties of analogues 1–2 dissolved in 1X PBS buffer and in 1,4-dioxane.

compound	solvent	λmax, abs / nm	λmax, em / nm	Stokes shift / nm	ε / L mol−1 cm−1	Φem	brightness (ε·Φem)	polarity sensitivitya
1a tCO	dioxane	357	442	85	7400	0.46	3400	6
	1X PBS	355	460	105	6800	0.24	1600
1b (8-MeO)tCO	dioxane	360	449	89	4800	0.38	1800	5
	1X PBS	361	486	125	4000	0.05	200
1c (7-MeO)tCO	dioxane	358	449	91	2700	0.37	1000	2
	1X PBS	360	487	127	3000	0.05	150
1d (8-Cl)tCO	dioxane	366	417	51	8500	0.49	4200	2
	1X PBS	361	455	94	5600	0.35	2000
1e (7-Cl)tCO	dioxane	363	446	83	8700	0.46	4000	4
	1X PBS	357	456	99	6700	0.35	2300
1f (7-F)tCO	dioxane	366	452	86	2700	0.41	1100	5
	1X PBS	360	462	102	1800	0.17	300
1g tetCO	dioxane	362	438	76	6700	0.43	2900	7
	1X PBS	361	434	73	5300	0.27	1400
2a tC	dioxane	369	472	103	4300	0.34	1500	3
	1X PBS	377	503	126	4700	0.09	400
2b (8-MeO)tC	dioxane	372	490	118	3800	0.28	1100	7
	1X PBS	379	538	159	3800	0.01	40
2c (7-MeO)tC	dioxane	372	477	105	2200	0.27	600	7
	1X PBS	379	508	129	2000	0.05	100

^[a]Expressed as the slope of Stokes shift plotted against solvent polarity as measured using the Dimroth-Reichardt E_T(30) scale. Units are 10¹ cm⁻¹/(kcal·mol⁻¹).