Xingliang Liu

Effects of cyano groups on the properties of thiazole-based β-ketoiminate boron complexes: aggregation-induced emission and mechanofluorochromism

A series of new thiazole-based β-ketoiminate boron complexes BF2-TT-CN, BPh2-TT-CN, BF2-TT and BPh2-TT, have been designed and successfully synthesized. These compounds show clear intramolecular charge transfer (ICT) from the electron donor (triphenylamine unit) to the electron acceptor (the β-iminoenolate boron moiety). It is particularly noteworthy that these compounds exhibit strong cyano-dependent aggregation-induced emission (AIE) and mechanofluorochromic (MFC) properties. In the cyano-substituted derivatives, BF2-TT-CN and BPh2-TT-CN, the high electron affinity of the cyano group confers stronger ICT properties relative to BF2-TT and BPh2-TT. In addition, the internal steric hindrance arising from the cyano group results in more twisted conformations, endowing BF2-TT-CN and BPh2-TT-CN with evident AIE characteristics and reversible mechanofluorochromism. The MFC behavior of BF2-TT-CN (from bright yellow to orange emission, λem from 542 to 599 nm) and BPh2-TT-CN (from bright yellow to orange emission, λem from 549 to 566 nm) is reversible by repeating the grinding-fuming process. However, BF2-TT and BPh2-TT, which lack cyano groups, exhibit no AIE and mechanofluorochromism, partly because of their relatively weak twisted configurations. Therefore, the introduction of the cyano group plays an important role in the strong ICT behavior and excellent mechanofluorochromic AIE properties of BF2-TT-CN and BPh2-TT-CN. These results will be of great help in understanding the AIE and MFC mechanisms and designing new MFC AIE materials.

Tetraphenylethene modified β-ketoiminate boron complexes bearing aggregation-induced emission and mechanofluorochromism

Two new tetraphenylethene modified β-ketoiminate boron complexes (TTPE-H and TTPE-CN) have been rationally designed and successfully synthesized. The two D–π–A type compounds exhibit typical twisted intramolecular charge-transfer (TICT) emission and evident aggregation-induced emission (AIE) characteristics, remarkable luminescence mechanochromism, and high solid state efficiency (up to 0.785 and 0.672). The mechanofluorochromic (MFC) behaviors of TTPE-H (from bright green to yellow-green emission, λem from 497 to 515 nm) and TTPE-CN (from bright yellow-green to yellow emission, λem from 525 to 565 nm) are reversible upon grinding and fuming treatments. From the X-ray diffraction and differential scanning calorimetry analyses, it was confirmed that the MFC properties of TTPE-H and TTPE-CN should be derived from a phase transition between crystalline and amorphous states. More interestingly, the compound TTPE-CN, which possesses a cyano group in the boron chelating ring, showed more contrast MFC behavior relative to TTPE-H. The reason is that the introduction of the cyano group can enhance the distortion degree of the molecule TTPE-CN because of steric hindrance.

β-Furan-Fused bis(Difluoroboron)-1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine Fluorescent Dyes in the Visible Deep-Red Region

Novel β-furan-fused bis(difluoroboron)-1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine (BOPHY) fluorescent dyes (F-BOPHY1-3) were prepared through an efficient process, and their structures were confirmed by (1)H NMR spectroscopy, (13)C NMR spectroscopy, MALDI-TOF HRMS, and element analysis. Their optical properties were then characterized by UV-vis absorption and photoluminescence (PL) spectroscopy. The UV-vis absorption and PL spectra of the dyes shifted to longer wavelengths relative to those of BOPHY because of the fusion of their furan rings, which extended π-conjugation of the molecules. All of the dyes exhibited large extinction coefficients (109700-12300 M(-1) cm(-1)), deep-red fluorescence emission (646-667 nm), moderate fluorescence quantum yields (0.30-0.45), as well as high chemical stability and photostability in solution. These advantageous properties show that these compounds are important to the design of efficient long-wavelength fluorescent dyes and are suitable for various applications in biotechnology and materials science.

A Ratiometric Fluorescent Sensor for Cd2+ Based on Internal Charge Transfer

This work reports on a novel fluorescent sensor 1 for Cd2+ ion based on the fluorophore of tetramethyl substituted bis(difluoroboron)-1,2-bis[(1H-pyrrol-2-yl)methylene]hydrazine (Me4BOPHY), which is modified with an electron donor moiety of N,N-bis(pyridin-2-ylmethyl)benzenamine. Sensor 1 has absorption and emission in visible region, at 550 nm and 675 nm, respectively. The long wavelength spectral response makes it easier to fabricate the fluorescence detector. The sensor mechanism is based on the tunable internal charge transfer (ICT) transition of molecule 1. Binding of Cd2+ ion quenches the ICT transition, but turns on the π − π transition of the fluorophore, thus enabling ratiometric fluorescence sensing. The limit of detection (LOD) was projected down to 0.77 ppb, which is far below the safety value (3 ppb) set for drinking water by World Health Organization. The sensor also demonstrates a high selectivity towards Cd2+ in comparison to other interferent metal ions.

Towards high visible light photocatalytic activity in rare earth and N co-doped SrTiO3: a first principles evaluation and prediction

The band structure and photocatalytic activity of RE (La, Ce, Pr or Nd) mono-doped and RE–N co-doped SrTiO3 for band gap reduction are studied systematically using first principles calculations. Based on the evaluation methods proposed by us previously, various RE–N co-doped cases with La–N, Ce–N, Pr–N and Nd–N co-doped in SrTiO3 are studied. By comprehensive comparison, the favourable co-doping dopants are obtained and the predicted Pr–N co-doped SrTiO3 shows that it may serve as an effective potential candidate photocatalyst for water splitting under visible light among the four types of RE–N co-doped cases. In addition, the f state electrons from the RE atom may have a greater contribution to the band structure narrowing of the RE–N co-doped SrTiO3.

A Cu2+-selective probe based on phenanthro-imidazole derivative

A novel fluorescent Probe 1, based on phenanthro-imidazole has been developed as an efficient chemosensor for the trace detection of copper ions (Cu2+). Probe 1 demonstrated sensitive fluorescence quenching upon binding with Cu2+ through 1:1 stoichiometric chelation. The detection limit for Cu2+ ions was projected through linear quenching fitting to be as low as 2.77 × 10−8 M (or 1.77 ppb). The sensing response was highly selective towards Cu2+ with minimal influence from other common metal ions, facilitating the practical application of Probe 1 in trace detection.

An aqueous fluorescent sensor for Pb 2+ based on phenothiazine-polyamide

A sensitive and selective fluorescent sensor for Pb2+ ion based on phenothiazine-polyamide was built (named sensor PP). Due to introducing of four diethanolamine groups to polyamide, this sensor was totally water soluble. PP could detect Pb2+ ion within 1u202fmin in the presence of other metal ions in aqueous solution, the detect limit was 9.11u202f×u202f10-8u202fM.

In situ green oxidation synthesis of Ti3+ and N self-doped SrTiOxNy nanoparticles with enhanced photocatalytic activity under visible light

A simple in situ green oxidation synthesis route was developed to prepare Ti3+ and N self-doped SrTiOxNy nanoparticles using TiN and H2O2 as precursors. X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) were used to characterize the crystallinity, structure and morphology. X-ray photoelectron spectroscopy (XPS) tests confirmed the presence of Ti3+ and N in the prepared SrTiOxNy nanoparticles. The resultant nanoparticles were shown to have strong absorption from 400 to 800 nm using UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The formation mechanism of the Ti3+ and N self-doped SrTiOxNy nanoparticles was also discussed. Under visible light irradiation, the obtained Ti3+ and N self-doped samples showed higher photocatalytic activity for the degradation of the model wastewater, methylene blue (MB) solution. The most active sample T-130-Vac, obtained at 130 °C under vacuum, showed a 9.5-fold enhancement in the visible light decomposition of MB in comparison to the commercial catalyst nano-SrTiO3. The sample also showed a relatively high cycling stability for photocatalytic activity.