Table 2 Photophysical properties of the dyads and triads in air-equilibrated toluene solutions

	λ_abs (nm)^a	λ_em (nm)^b	τ_F (ps)^c	E_FRET,theor^d	E_FRET,exp^e	Slope log-log plot^f	FR^g
NOMe/Napht	489	493	5.5	0.999	0.999	3.80 ± 0.45	97%
**asyNOMe/Napht**	489	493	3.1	0.999	0.999	3.17 ± 0.42	98%
DASA/Napht	571	499	4.1	0.999	0.999	3.78 ± 0.24	99%
NTPA/Napht	577	492	3.9	0.999	0.999	3.94 ± 0.27	96%
DASA/FRT	571	467	1.7	0.999	0.999	3.84 ± 0.16	97%
NOMe/Phtha	490	462	1.4	0.999	0.999	4.46 ± 0.39	97%

^a UV/vis absorption maximum of the colored form (PS_C).
^b Emission maximum of the 2PAP fluorophore.
^c Fluorescence lifetime of the quenched emission in PS_C−2PAP. Monoexponential decays, except for NOMe/Phtha, where an amplitude-averaged lifetime is given [τ₁ = 0.43 ps (71%) and τ₂ = 3.8 ps (29%)].
^d Theoretically expected FRET efficiency, based on the critical FRET radius R₀ and actual interchromophore distance R; see the Supplementary Information for details.
^e Experimentally observed FRET efficiency; E_FRET = 1 – τ_F(PS_C-2PAP)/τ_F(2PAP model).
^f Slope of the log-log plot of fluorescence intensity versus excitation intensity.
^g Fatigue resistance FR; shown is the percentage of the intact population after ten switching cycles.

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