The absorption maximum of SM4.15 was greater than that of SM4.16 guided by the electron‐donating strength of the aryl group pentafluorophenyl> p ‐trifluoromethylphenyl and the other compounds also showed a trend SM4.14 > SM4.13 > SM4.12 > SM4.11 guided by the electron donating strength of the aryl counterpart which is N,N ‐dibutylaminophenyl> p ‐butoxyphenyl> p ‐butylphenyl>phenyl.
1
—
—