Study on second harmonic generation of 9-benzylidene-substituted-10-methyl-9,10-dihydroacridines

Eight 9-benzylidene-substituted-10-methyl-9,10-dihydroacridine derivatives were synthesized from acridine as starting material and were characterized by 1H-NMR, 13C-NMR, Ms and elemental analysis. The second harmonic generation (SHG) values of these compounds were determined in powder using Nd:YAG as a laser source, as compared with urea powder, and the values of second-order polarizabilities (betaxxx), the values of the composite magnitude (betaCTmicrog) of molecular hypersusceptibilities and their moment of these compounds were obtained by the solvatochromic method under ground state for everyone. The results showed that SHG value of 10 is higher than that of urea; the betaCTmicrog of 5 (107.8 x 10(-30) esu) is lower than that of 4-nitro-N,N-dimethylaniline (30 x 10(-30) esu); the betaCTmicrog of 7 (350.8 x 10(-30) esu) and 10 (244.6 x 10(-30) esu) are higher than that of 4-nitro-N,N-dimethylaniline; the betaCTmicrog of 8 (3553 x 10(-30) esu), 11 (1187 x 10(-30) esu) and 12 (1163 x 10(-30) esu) are much more higher than that of 4-nitro-N,N-dimethylaniline. The results demonstrated that this series of compounds possesses good second-order nonlinear optical (NLO) property. The regular relationship could not be obtained between electronegativity of substituents (R) attached to benzylidene ring and SHG values or betaCTmicrog values although the Rs are different in electronegativity and should make an effect on the extent of intramolecular electron-transfer and would consequently influence SHG or betaCTmicrog. The electron-withdrawing ability of R from benzylidene ring played an important role on lambdamax of these compounds.