Table 1. Electronic effect of R′ substituents on the relationship between the structure and photophysical properties of Seoul‐Fluors.^[a] .

Compound	R′	σp[b]	Eh[c]	λabs[d]	λem[e]	ΦF[f]
10	4‐NEt2	−0.72	−0.160	441	–	0.00
11	4‐NH2	−0.66	−0.169	419	546	0.03
12	4‐OH	−0.37	−0.200	413	572	0.12
13	4‐OMe	−0.27	−0.195	412	555	0.20
14	4‐Me	−0.17	−0.215	404	534	0.38
15	4‐H	0	−0.227	403	523	0.50
16	4‐F	0.06	−0.225	402	525	0.47
17	4‐CF3	0.54	−0.249	405	514	0.64
18	4‐CN	0.66	−0.247	398	512	0.63
19	3,4‐(CN)2	–	−0.262	402	500	0.72

[a] Measurements were made in methanol. [b] σ_p is the Hammett constant of the R′ substituent at the para position.9 [c] Calculated energy in hartree of the HOMO level of the phenyl moiety. [d] Longest absorption wavelength maximum. [e] The emission wavelength for excitation at the longest absorption wavelength maximum. [f] Absolute fluorescence quantum yield.