Abstract: Three Y-type triphenylamine chromophores, N,N-Bis-{4-[1-(2-benzothiazolyl)-1,3-butadiene-4-yl]phenyl}aniline(BBtBPA), N,N-bis-{4-[2-(2-benzothiazolyl)vinyl]phenyl}aniline(BBtVPA), and N,N-bis-{4-[1-(3-cyano-2-dicyanomethylidene-5,5-dimethyl-2,5-dihydro-4-furyl)-1,3-butadiene-4-yl]phenyl}aniline(BCfBPA) and four dipolar ones, 1-(2-benzothiazolyl)-4-[4-(N,N-diphenyl)amino]phenyl-1,3-butadiene(BtAPB), 4-[2-(2-benzothiazolyl)vinyl]-N,N-diphenylaniline(BtVPA), 1-[(3-cyano-2-dicyanomethylidene-{5,5}-dimethyl-2,5-dihydro)-4-furyl]-4-[4-(N,N-diphenyl)-amino]-phenyl-1,3-butadiene(CfAPB) and 4-[2-(3-cyano-2-dicyanomethylidene-5,5-dimethyl-2,5-dihydro-4-furyl)vinyl]-N,N-diphenylaniline(CfVPA) were synthesized through Knoevenagel reaction, with variations in the electron acceptor substitutes and π-conjugated bridges. Absorption and fluorescence properties of these chromophores were investigated. Maxima absorption in dichloromethane were at 425 nm for BBtVPA, 443 nm for BBtBPA, and 613 nm for BCfBPA, respectively. The fluorescence maxima of BBtVPA and BBtBPA were at 516  and 558 nm, respectively. Compared with their dipolar analogues, the Y-type chromophores present about 30 nm bathochromic-shift of absorption maxima, along with slightly bathochromic-shift of fluorescence maxima. Static second-order polarizabilities β0 were obtained as 40×10-30 esu for BBtVPA, 64×10-30 esu for BBtBPA, and 238×10-30 esu for BCfBPA, respectively, by solvatochromic method based on the two-level model, while 0.9—2.8 times enhancement of β0 were observed compared with the dipolar chromophores. Besides, extension of π-conjugation and improvement of electron acceptor strength both increase the β value. Quantum chemical calculations were carried out to aid in better understanding of the structure-property relationship.

Key words: Y-type chromophore, Second-order polarizability, Solvatochromic effect, Fluorescence property; , Structure-property relationship