Search

Triphenyl pyrazoline derivative, 1,3-diphenyl-5-{4-[2-(4-(phenylazo)phenoxy)ethyloxy]phenyl}-2-pyrazoline (compound III), was synthesized and its optical properties were studied by UV–VIS and fluorescence spectroscopies. The UV–VIS spectrum showed that the electronic transition bands of azobenzene and triphenyl pyrazoline groups were overlapped at ≈350 nm. The fluorescent emission band appeared at 450 nm, which was located at the range of n–π* transition band of azobenzene. It was found that the fluorescence intensity of pyrazoline moiety could be modulated by irradiation with UV and visible light due to the reversible trans–cis–trans photoisomerization reaction of azobenzene moiety. It indicated that the intramolecular electronic energy transfer from pyrazoline moiety to azobenzene one happened and the degree of energy transfer was determined by the content of cis-isomer of azobenzene moiety. [Copyright &y& Elsevier]

We have synthesized two new two-photon active dendritic molecules with tetraphenylmethane core with four phenothiazine-based arms. They show good solubility in organic solvents, including dichloromethane, chloroform, toluene and tetrahydrofuran. It is found that the two dendrimers display strong two-photon absorption and two-photon excited up-conversion fluorescence at 800 nm. • Two new phenothiazine-based dendrimers with tetraphenylmethane cores have been synthesized. • The dendritic molecules display two-photon absorption activity. • The two-photon absorption cross section increased with the increasing of the conjugation degree. [ABSTRACT FROM AUTHOR]

Three push–pull type azo dyes, 4′-{[(2-hydroxylethyl)methyl]amino}-4-nitroazobenzene (compound I), 1-[4-(4′-nitrophenyl)-azophenyl]-3,5-biphenyl-2-pyrazoline (compound II) and 1-[4-(4′-nitrophenyl)-azophenyl]-3-(3′-trifluoromethyl)-phenyl-5-phenyl-2-pyrazoline (compound III) were synthesized. The cis–trans isomerization process and polarized photoinduced birefringence of those azo dyes doped PMMA films were investigated. It was found that the rise and relaxation process of birefringence signals were fit with biexponential functions and the molecular structures have effects on their photo-induced birefringence. This suggests that the three films have similar storage speed when the laser intensity is high enough. Compound III, which has the biggest substituent, has the largest long-term storage ability and can even keep 90% of its saturated birefringence. [Copyright &y& Elsevier]

Highlights: [•] 2,1,3-Benzothiadiazole-cored H-shaped conjugated compounds were synthesized. [•] Two-photon absorption (TPA) and two-photon induced emission properties were investigated. [•] These compounds emit red light excited by the femtosecond pulsed laser of 820nm. [•] Strong electron donor, enlarged conjugation and branched structure favored the increasing of TPA. [ABSTRACT FROM AUTHOR]

Abstract: We compare the effects of fluorene–ethylene (FE) spacers on the photo-physical properties of fluorenone-based conjugated oligomers. The introduction of FE spacer could modulate the steady-state spectra and weaken the difference between donor-dependent spectral features. Meanwhile, the quantum chemical calculations exhibit that the electron transition mechanism modulated by FE unit is variable with the donor of oligomers. The FE π-spacer mainly rises the HOMO and facilitates the electron delocalization in the fluorene end-capped oligomer, while it lowers the LUMO and enhances the donor effect in the triphenylamine end-capped one. The time-resolved fluorescence measurement exhibits that the difference between donor-dependent excited state lifetimes of oligomers becomes less obvious after the introduction of FE units. Moreover, the nonlinear optical measurements show that the FE spacer is able to improve the two-photon fluorescence efficiency and enhance the two-photon absorption cross-section of oligomers simultaneously, but the difference in two-photon characteristics between oligomers with different donors is also decreased. [Copyright &y& Elsevier]

Abstract: Experimental and theoretical studies on the donor-dependent optical characteristics of two D–π–A–π–D type linear fluorenone-based conjugated oligomers are presented, where fluorene and triphenylamine act as the donors, respectively. Because of the strong electron-donating ability, the triphenylamine chromophores lead to red-shifts of spectral features, shorten the excited state lifetime, and enhance the two-photon fluorescence efficiency and two-photon absorption cross-section in comparison with fluorene groups. Quantum chemical calculations provide complementary information regarding the molecular structures and the frontier orbitals, which can provide a deep insight into the electronic structure and properties of oligomers. [Copyright &y& Elsevier]

Four new D-π-A type N,O -chelated BF 2 complexes (TCBOB , TCBTB , TCQB and TCPB) were synthesized. It was found that TCPB bearing the ligand of N -(1-pyridinyl)benzoamide shows gelation ability in methylcyclohexane, DCM/peteroleum ether, etc. The time-dependent UV–vis absorption and fluorescent emission spectral changes during the gel formation revealed that π-π interactions play important roles in the self-assembling processes. Particularly, the emission of the xerogel-based film of TCPB can be quenched by TFA (trifluoroacetic acid) vapor, and it showed high performance in the detection of TFA compared with the spin-coating films of TCBOB , TCBTB and TCQB. In addition, the BF 2 complexes exhibited reversible mechanofluorochromic behavior under the treatment of grinding/fuming or heating, and TCPB gave high-contrast mechanofluorochromism compared with others. XRD patterns in different solid states demonstrated that the external mechanical forces can induce the transformation from the crystalline to the amorphous states. Powder of TCPB was also used to image latent fingerprints on surface of glasses, and distinct fluorescent images were obtained. [Display omitted] • New BF 2 complexes were synthesized. • Gelation abilities and MFC properties of them were studied. • They were first used to detect LFP. [ABSTRACT FROM AUTHOR]