The structures of the nitric oxide fluorescent probes for nitric oxide and their photo-physical properties.

Unreacted probe					Pr. no	Cinnoline product
λ abs a (nm)	λ em b (nm)	ε c × 103 M−1 cm−1	ϕ d	Structure		X or Z	λ abs a (nm)	λ em b (nm)	ε c × 103 M−1 cm−1	ϕ d	Relativee,f brightness
300	420	10.0	0.54		1	–OMe	395	488	14.0	0.09	3.0
300	420	11.0	0.47		2	–OH	395	490	13.2	0.67	20.0
310	415	9.0	0.27		3	–NMe2	415	510	14.3	0.02	0.7
300	390	14.4	0.003		4	—	450	550	16.2	0.003	0.1
310	415	9.9	0.24		5	—	425	508	20.8	0.62	29.3
300	415	9.5	0.1		6	—	447	535	11.3	0.36	9.3
350	450	9.9	0.02		7	–NHAc	433	535	13.0	0.08	2.3
330	445	8.0	0.04		8	–H	430	530	13.9	0.06	1.9
350	n.d.	3.5	n.d.g		9	–CN (NO550)	450	550	4.0	0.11	1.0
370	455	9.4	0.07		10	–NHAc (NO530)	445	530	20.1	0.5	23.0
355	450	10.3	0.02		11	–H	440	525	24.1	0.5	27.5
345	510	11.6	0.03		12	–CN	450	545	7.3	0.13	2.2
420	465	12.2	0.01		13	–NHAc (NO562)	470	562	15.5	0.35	12.3
350	425	11.3	0.01		14	H	466	555	16.9	0.24	9.3
390	515	12.4	0.02		15	CN	480	580	9.0	0.11	2.3

^aWavelength of maximum absorbance for the most bathochromic peak in the UV-vis spectrum.

^bWavelength of maximum emission for the largest peak in the emission spectrum when excited at the most bathochromic absorbance maximum.

^cAbsorptivity coefficient/1000.

^dQuantum efficiency.

^eBrightness relative to the cinnoline product of NO₅₅₀ (9), previously reported as AZO₅₅₀.

^fCinnoline brightness is defined as the product of the absorptivity coefficient and the quantum efficiency.

^gNO₅₅₀ does not fluoresce in 1 : 4 DMSO/50 mM PBS at pH 7.4. The blue values highlight the best performers' fluorescence properties in 1 : 4 DMSO/50 mM PBS at pH 7.4, of the probes and their cinnoline, or azo, products (hereafter denoted as “AZO-Probe Number”), produced from reaction with nitrite in acid.