•A new chemosensor based on rhodamine-azacrown derivative is reported.•The sensor responds to Al3+ and Fe3+ with a simple 1:1 mode in aqueous solutions.•The detection limit of Fe3+ is 1.2 × 10−8 M in aqueous solution.•The sensor selectively responds to Al3+ with a 1:2 complex form in acetonitrile.•The detection limit of Al3+ is 5.9 × 10−7 M in acetonitrile.A rhodamine-azacrown derivative (2-(2-(1,4-dioxa-7,13-dithia-10-azacyclo- pentadecan-10-yl)ethyl)-3′,6′-bis(diethyl amino)spiro[isoindoline-1,9′-xanthen]-3-one) responded to Al3+ and Fe3+ in ethanol–water solutions (20/80, v/v, pH = 7.0) and selectively responded to Al3+ in acetonitrile. In addition, it bound to the cation with a simple 1:1 mode in aqueous solutions and 2:1 mode in acetonitrile. The association constants (logKa) of the sensor for Fe3+ and Al3+ were obtained to be 6.5 and 3.6 in ethanol–water, and the corresponding detection limits were calculated to be 1.2 and 8.6 × 10−8 M, respectively, while the association constant (logKa) for Al3+ was 3.9 with a detection limit of 5.9 × 10−7 M in acetonitrile under our experimental conditions. Nuclear magnetic resonance and other investigations indicated that in acetonitrile the existence of the second Al3+ shifted the binding location of the first Al3+, which led to the spirolactam ring-open and fluorescence formation. The mechanisms for the sensor to Al3+ and Fe3+ in different solvents are discussed in detail.

A lanthanide-based luminescent probe [EuL] for Zn2+ was synthesized utilizing a DO3A ring as the Eu3+ chelator and a DPA moiety as the Zn2+ chelator. A quinoxaline functioned as both the linker and antenna. The two nitrogen atoms in quinoxaline are involved in the Eu3+ and Zn2+ binding, respectively. It gave an excitation at 336 nm for [EuL], which was longer than the reported values of this type of probes at present. Moreover, the titration studies provided a dissociation constant (Kd) of 55 nM for [EuL] while the competition investigation indicated that [EuL] had an affinity comparable to that of TPA (Kd 0.014 nM).

•Two T1-weighted MRI contrast agents have been synthesized and characterized.•The rigid linkages improved the relaxivity of the agents.•The complexes exhibited high thermodynamic stability and kinetic inertness.Two macrocyclic chelating MRI agents (Gd-DO3A)3–TAB and (Gd-DO3A)2–DAB have been successfully synthesized by appending three and two Gd-DO3A moieties upon the acetylbenzene derivatives, respectively. The longitudinal relaxivity of (Gd-DO3A)3–TAB measured at 20 MHz, 37 °C and pH 7.0 is 6.1 mMGd−1 s−1, 74% higher than that of the mononuclear clinical agent [Gd(DOTA)(H2O)]−. A 30% or 16% increase in relaxivity was observed upon addition of 0.72 mM bovine serum albumin (BSA) or 10-fold of diamagnetic ion La3+. More importantly, the thermodynamic stability and kinetic inertness of (Gd-DO3A)3–TAB are comparable to or better than that of [Gd(DTPA)(H2O)]2−. The luminescence lifetime study on the corresponding (Eu-DO3A)3–TAB analog demonstrated that the agent had one inner-sphere water coordinated to the Eu3+ center within the complex. The cytotoxicity study indicated that the toxicity of the agent was low with IC50 = 18 mM. In addition, the characterization of its dinuclear analog (Gd-DO3A)2–DAB has also been investigated.(Gd-DO3A)3–TAB possessed higher water proton relaxivity, high thermodynamic and kinetic stability, and low toxicity, which facilitate the further development of clinical applicable multinuclear MR contrast agents.

Three chemosensors for Zn2+ were designed and synthesized based on the chromophore of the blue fluorescent protein (BFP). Among them, IMMPI (4-((1H-imidazol-2-yl)methylene)-1-methyl-2-phenyl-1H-imidazol-5(4H)-one) contained one BFP chromophore unit, which sequestered Zn2+ with nitrogen in the two imidazole rings, while Di-IMMPI-a and Di-IMMPI-o contained two IMMPI units that were connected together using an alkane and a methoxy chain, respectively. All three molecules selectively interacted with Zn2+ with a 1:1 mode. Di-IMMPI-a had a dissociation constant <0.03 μM for Zn2+, more than 30 folds stronger than that of IMMPI. The fluorescences of IMMPI, Di-IMMPI-a, and Di-IMMPI-o were turned on upon the binding of Zn2+, accompanied by the quantum yields enhancing from <0.002 to 0.352, 0.451, and 0.194, respectively. Fluorescence images showed that Di-IMMPI-a responded to Zn2+ in cell cytosol. Our work demonstrated the potentiality for the development of practical Zn2+ sensors based on the isolated BFP chromophores without the proteinframe.Highlights► Three chemosensors for Zn2+ were designed based on the chromophore of BFP. ► IMMPI contains two imidazole rings as the chromophore of BFP. ► Di-IMMPI-a and Di-IMMPI-o contain two IMMPI units. ► IMMPIs (IMMPI, Di-IMMPI-a and Di-IMMPI-o) bound to Zn2+ with high affinity and selectivity. ► Di-IMMPI-a is the most sensitive fluorescent Zn2+ chemosensor based on GFP and its derivatives at present.

Two di-nuclear non-ionic MRI contrast agents, (Gd-DO3A)2-BMQX and (Gd-DO3A)2-BMP, have been designed and synthesized by fusing the DO3A units together with a quinoxalinyl or pyrazinyl moiety. They have improved longitudinal relaxivities of 5.23 and 5.16 mM Gd−1 s−1, respectively, at 20 MHz magnet, 37 °C and pH 7.0. In addition, they possess high thermodynamic stability and kinetic inertness. The cytotoxicity studies indicated that the toxicity of these two agents were low. All these properties satisfy the requirements for clinical applications.

A simple, metal- and ligand-free procedure for the Ullmann-type C–O coupling reactions has been achieved by allowing aryl bromides to react with a variety of phenols in the presence of t-BuOK. Moderate to excellent yields of O-arylation products are obtained under mild conditions in a short time. In addition, two examples of C–N coupling reactions are also reported. A benzyne mechanism is proposed according to the experiment data.

Single-walled carbon nanotubes (SWCNTs) are aligned by using a ferroelectric liquid crystal (FLC) named [4-(3)-(S)-methyl-2-(S)-chloropentanoyloxy)]-4′-nonyloxy-biphenyl. The scanning electron microscope (SEM) is utilized to investigate the alignment of the SWCNTs in the smectic A phase. Fourier Transform Infrared spectroscopy (FTIR) and Raman spectroscopy are utilized to investigate the interaction between these two species. The SEM images show that SWCNTs can be well aligned along the smectic layers. A new peak appears at 1702 cm–1 in the FTIR spectra in the SWCNT hybrids, which indicate that charge transfer occurring from the hexagonal rings of the SWCNTs to the C═O groups of the FLC molecules that contact directly with the SWCNTs. To our knowledge, this is the first time we observe the charge transfer effect by FTIR. Similarly, a new peak at 763 cm–1 is also found in the Raman spectrum of the SWCNT hybrid that results from the charge transfer effect between the SWCNTs and the C–Cl groups of the FLC. The π–π stacking and charge transfer effect together make the SWCNTs align unidirectionally along the smectic layers instead of in the direction of the molecular long axis.

In order to investigate the structural and dynamical properties of ferroelectric liquid crystal (FLC) in different phases a model compound [4-(3)-(S)-methyl-2-(S)-chloropentanoyloxy)]-4′-nonyloxy-biphenyl (3M2CPNOB) is synthesized. High resolution transmission electron microscopy (HR-TEM) is applied to observe the morphology of 3M2CPNOB and temperature-dependent solid state 13C NMR to record 13C chemical shifts at different phases. A liquid nitrogen quenching method is used to maintain the conformation of the mesophases for HR-TEM experiments. TEM images show that all the smectic A (SmA), smectic C* (SmC*) and crystalline phases have lamellar morphology. The interplanar distances in the crystalline phase are smaller than those in SmA and SmC* phases because of denser arrangement of the molecules. Both 13C chemical shifts and line shape vary with different phases. The experimental results suggest that SmC* phase as an intermediate occurs in the anisotropy transition process from SmA to crystalline phase, the helical structure of the SmC* phase unwinds in the magnetic field and the conformations of the SmA and isotropic phase are very similar.

The volatile compositions of Melia azedarach were studied by headspace solid-phase microextraction (HS-SPME). The result was compared with that obtained by soxhlet extraction (SE) and ultrasonic extraction (UAE). 79 compounds were identified in this study, among which 64 compounds were first reported. The experimental parameters including fiber type (PDMS, PDMS-DVB and CAR-PDMS), desorption time, extraction temperature and time were investigated. 37 compounds were obtained by HS-SPME, including curcumene (33.25%), α-cadinol (11.16%), α-muurolene (8.72%), copaene (5.04%), β-bisabolene (3.41%), and α-selinene (2.97%). The result suggested that the HS-SPME method is a powerful analytic tool and complementary to traditional methods for the determination of the volatile compounds in Chinese herbs.Highlights► HS-SPME, SE and UAE methods are used to study the volatile compositions of Melia azedarach. ► The HS-SPME method is first used with simple, fast and solvent-free merits. ► 79 compounds are identified, among which 64 compounds are first reported. ► 37 compounds are identified by the HS-SPME alone.

Two GFP analogues o-HBDI and o-HBMO have been designed and synthesized. The former shows no fluorescence while the latter shows strong fluorescence due to the formation of an intramolecular hydrogen-bond. At low temperatures, both molecules have strong fluorescence.

Two GFP analogues o-HBDI and o-HBMO have been designed and synthesized. The former shows no fluorescence while the latter shows strong fluorescence due to the formation of an intramolecular hydrogen-bond. At low temperatures, both molecules have strong fluorescence.