The Influence of Structural Isomerism on the Photophysical Properties of a Series of Donor-Acceptor 1-Naphthalenecarbonitrile Derivatives Possessing Amine Substituents

In an effort to probe the influence of structural isomerism on the excited-state properties of a naphthalene-based donor-acceptor (D-A) system, four 1-naphthalenecarbonitrile compounds with amine substituents in the 2-, 3-, and 4- positions were synthesized and their photophysical properties were examined. Specifically, the molecules 2-dimethylamino-1-naphthalenecarbonitrile (2DA), 2-(1-piperidinyl)-1-naphthalenecarbonitrile (2P), 3-dimethylamino-1-naphthalenecarbonitrile (3DA), and 4-(1-piperidinyl)-1-naphthalenecarbonitrile (4P) were studied. Substitution position of the amine donor has a significant impact on both the ground-state absorption and excited-state properties of the complexes in toluene solution. The energy, band shape, and extinction coefficient of the ground-state absorption spectra are highly dependent on substitution position of the amine donor. All of the derivatives exhibit fluorescence at room temperature. The fluorescence observed from 2DA, 2P, and 3DA demonstrates vibronic structure...