Bingzhu Yin

Colorimetric and fluorometric dual-modal probes for cyanide detection based on the doubly activated Michael acceptor and their bioimaging applications

In this study, we synthesized CTB and CB probes based on doubly activated Michael acceptors to selectively detect cyanide (CN(-)) anions through a one-step condensation reaction of coumarinyl acrylaldehyde with the corresponding derivatives of malonyl urea (thiourea). Through the conjugated addition of CN(-) to the β-site of the Michael acceptor, both probes displayed colorimetric and fluorometric dual-modal responses that were highly reactive and selective. CTB generates an active fluorescent response, whereas CB displays a ratiometric fluorescent response. The fluorescent signal of the probes reached its maximum given only 1 CN(-) equivalent and the signal change was linearly proportional to CN(-) concentrations ranging from 0 to 5 μM with the detection limits 18 and 23 nM, respectively. The reaction rate of the probes is highly dependent on the methylene acidity of malonyl urea derivatives. Thus, the response rate of CTB to CN(-) is 1.2-fold faster than that of CB, and the response rate of CB to CN(-) is 1.2-fold faster than that of the previously examined CM. We then verified the highly reactive nature of the β-site of the probes through density functional reactivity theory calculations. In addition, according to proof-of-concept experiments, these probes may be applied to analyze CN(-) contaminated water and biomimetic samples. Finally, cell cytotoxicity and bioimaging studies revealed that the probes were cell-permeable and could be used to detect CN(-) with low cytotoxicity.

A high-performance ambipolar organic field-effect transistor based on a bidirectional π-extended diketopyrrolopyrrole under ambient conditions

A novel bidirectional π-extended 2,5-dihydro-1,4-dioxo-3,6-di-2-thienyl-1,4-diketopyrrolo[3,4-c]pyrrole derivative (DPP-2T) with the 4-(2,2-dicyanovinyl)phenyl group, (DPP-2T2P–2DCV), has been synthesized and characterized in order to achieve a high-performance organic semiconductor. The HOMO/LUMO energies of DPP-2T2P–2DCV were estimated to be −5.36 and −3.81 eV, respectively, based on their redox potentials, which were very similar to the other bidirectional π-extended DPP-2T analogue DPP-4T–2DCV. The calculated HOMO/LUMO values (HOMO: −5.43 eV, LUMO: −3.56 eV) based on the optimized geometry agreed well with the experimental values. DPP-2T2P–2DCV exhibits ambipolar TFT response with reasonably balanced electron and hole mobilities of 0.168 cm2 V−1 s−1 and 0.015 cm2 V−1 s−1 by solution process, respectively, which is the best result for solution processable DPP-based ambipolar small molecule semiconductors measured under ambient atmosphere.

A dual-selective fluorescent probe for GSH and Cys detection: Emission and pH dependent selectivity

A novel fluorescent probe 1 based on acridine orange was developed for the selective detection and bioimaging of biothiols. The probe exhibits higher selectivity and turn-on fluorescence response to cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) than to other amino acids. Importantly, the probe responds to GSH and Cys/Hcy with distinct fluorescence emissions in PBS buffer at pH of 7.4. The Cys/Hcy-triggered tandem SNAr-rearrangement reaction and GSH-induced SNAr reaction with the probe led to the corresponding amino-acridinium and thio-acridinium dyes, respectively, which can discriminate GSH from Cys/Hcy through different emission channels. Interestingly, Cys finishes the tandem reaction with the probe and subsequently forms amino-acridinium and Hcy/GSH induces SNAr reaction with the probe to form thio-acridiniums at weakly acidic conditions (pH 6.0), enabling Cys to be discriminated from Hcy/GSH at different emissions. Finally, we demonstrated that probe 1 can selectively probe GSH over Cys and Hcy or Cys over GSH and Hcy in HeLa cells through multicolor imaging.

Supramolecular helical nanofibers formed by an achiral monopyrrolotetrathiafulvalene derivative: water-triggered gelation and chiral evolution

Chiral nanostructures have attracted increasing attention, which would provide not only a better understanding of the bio self-assembly process, but also open a route for new applications. In this research study, the organogel formation and self-assembly of an achiral MPTTF-based molecule were investigated. It was found that the compound could not gelate any single solvent either through a heating and cooling process or by ultrasonic treatment, but formed certain ordered supramolecular self-assembled aggregates in pure DMF with left- (M) and right- (P) helicities. Interestingly, supramolecular gelation was triggered by adding a small amount of water in its DMF solution, and the structure of the fibers was almost entirely turned into right-handed helicity. The twisted superstructure was visualised by AFM, and CD was used to observe chirality within the assembly. Also, the investigation of UV-Vis spectra, FTIR and SAXS indicated that these supramolecular assemblies were induced by hydrogen bonding, π–π stacking and S⋯S interaction between the molecules. Furthermore, the formed organogel underwent a reversible gel–sol phase transition via a chemical redox reaction. This work sheds new light on the hierarchical transformation of chiral structures from achiral molecules by controlling the solvent composition and polarity.

Gel properties of T-shaped tetrathiafulvalene–pyridazine conjugates and F4TCNQ-induced morphological transformation

A new series of T-shaped organic π-conjugate organogelators, monopyridazine–TTFs, were synthesized and characterized. All of the gelators could gelate the aromatic solvents, such as benzene, toluene and chlorobenzene, and the length of the alkyl chain had a certain influence on the gelation behavior. Interestingly, the gelators could react with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) to form the charge-transfer complex organogels. FT-IR, UV-Vis, 1H NMR and CV experiments revealed that the cooperation of hydrogen bonding, π–π, and CT interactions was the main driving force for the formation of the native and CT gels. The FE-SEM images of the native gels reveal the characteristic gelation morphologies of fibrous structures, whereas the morphologies of CT complex gels show the amorphous block aggregates. XRD study of the native gel and the CT complex gel of 1b in DMF suggests that the molecules maintain lamellar and hexagonal columnar molecular packing models in the gel phase, respectively. Furthermore, the DMF gel of 1b could be destroyed only by the addition of the fluorine ions, while the toluene gel could be transformed into solution or suspension after adding halogen ions.

4,6,7,9,10,12-Hexahydro-1,3-dithiolo[4,5-f][1,4,9]oxadithia-cyclo-undecine-2-thione.

In the title molecule, C9H12S5O, the five-membered ring and attached S atom are essentially coplanar [mean deviation from the mean plane = 0.020 (1) Å]. The two S atoms belonging to the macrocycle deviate from this plane by 1.005 (1) and 1.337 (2) Å. In the crystal, π–π interactions link the molecules into centrosymmetric dimers with a short distance of 3.753 (5) Å between the centroids of the five-membered rings.

1,2-Bis(1,3-dithiol-2-yl­idene)hydrazine

The title molecule, C6H4N2S4, has a crystallographically imposed centre of symmetry located at the mid-point of the N—N single bond. The molecule is essentially planar: the two five-membered rings form a dihedral angle of 0.17 (6)°. The crystal packing exhibits short intermolecular S⋯S contacts of 3.549 (2) Å.