Synthesis and third-order nonlinear properties of D-A-D structure acridone derivatives

Six acridone derivatives with 2,7-bis-substituted D-A-D structures were designed and synthesized. Z-scan technology and DFT theoretical calculations studied the influence of the structure on the nonlinear optical properties. The ultraviolet–visible spectrum of compound YB3 with bis-(diphenylamino)phenyl substitution shows an ultraviolet maximum absorbance at 364 nm. This wavelength is red-shifted by 44 nm compared to compound YB1 with bis-(methoxyphenyl) substitution (at 320 nm). This change is interpreted as a strengthened electron supply and expanded conjugate system by the electron-donating bis-(diphenylamino)phenyl substitution groups. Cyclic voltammetry and DFT calculations show that the dihedral angle between electron-donating group and electron-withdrawing group (The dihedral angle is defined by two atoms on each side of the bond between the donor and the acceptor for a total of four connected carbon atoms.) should be as small as possible. Structure (2,7-bis-(4-(diphenylamino)phenyl)-10-dodecylacridin-9(10H)-one (YB3) shows the optimal third-order NLO behavior with a second-order NLO hyperpolarizability γ of 8.665 × 10^–33 esu, which is 1.6 times higher than that of YB1 (γ = 5.136 × 10^–33 esu), and 1.7 times that of YA4 with bis-(4-(-di-(4-methoxyphenyl)amino)phenyl) 2,7-substitution of the 10-dodecylacridin-9(10H)-one. Graphical abstract: [Figure not available: see fulltext.].