TABLE 2.

Photophysical Properties in THF

Compound	λabs (nm)	λema (nm)	Φfb
1a	631	647	0.70
1b	630	647	0.72
1c	629	648	0.70
1d	632	651	0.65
2a	640	658	0.70
2b	638	657	0.74
2c	636	659	0.67
2d	641	662	0.65
2e	650	674	0.26

^aSymmtrical dyes 1a–d and rotaxanes 2a–e were excited at 580 nm and emission was monitored in the 600–750 nm region for estimating Φ_f.

^bFluorescence quantum yields (error limit ± 5 %) were determined for using 4,4-[bis(N,N-dimethylamino)phenyl] squaraine dye as the standard (Φ_f = 0.70 in CHCl₃) Molar absorptivities were typical of squaraine dyes 1a–d having log ε = 5.4, squaraine rotaxanes 2a–e having log ε = 5.6.