A Series of Lanthanide Coordination Polymers as Luminescent Sensors for Selective Detection of Inorganic Ions and Nitrobenzene.

Seven new lanthanide coordination polymers, namely [Ln(cpt)3H2O)]n(Ln = La (1), Pr (2), Sm (3), Eu (4), Gd (5), Dy (6), and Er (7)), which were synthesized under hydrothermal conditions using 4'-(4-(4-carboxyphenyloxy)phenyl)-4,2':6',4'-tripyridine (Hcpt) as the ligand. The crystal structures of these seven complexes were determined using single-crystal X-ray diffraction, and they were found to be isostructural, crystallizing in the triclinic P1- space group. The Ln(III) ions were nine-coordinated with tricapped trigonal prism coordination geometry. The Ln(III) cations were coordinated by carboxylic and pyridine groups from (cpt)- ligands, forming one-dimensional ring-chain structures. Furthermore, the luminescent properties of complexes 1-7 were investigated using fluorescent spectra in the solid state. The fluorescence sensing experiments demonstrated that complex 4 exhibits high selectivity and sensitivity for detecting Co2+, Cu2+ ions, and nitrobenzene. Moreover, complex 3 shows good capability for detecting Cu2+ ions and nitrobenzene. Additionally, the sensing mechanism was also thoroughly examined through theoretical calculations.

Enhancing Electrocatalytic Water Oxidation of NiFe-LDH Nanosheets via Bismuth-Induced Electronic Structure Engineering.

The design and synthesis of high-efficiency electrocatalysts are of great practical significance in electrocatalytic water splitting, specifically in accelerating the slow oxygen evolution reaction (OER). Herein, a self-supported bismuth-doped NiFe layered double hydroxide (LDH) nanosheet array for water splitting was successfully constructed on nickel foam by a one-step hydrothermal strategy. Benefiting from the abundant active sites of two-dimensional nanosheets and electronic effect of Bi-doped NiFe LDH, the optimal Bi0.2NiFe LDH electrocatalyst exhibits excellent OER performance in basic media. It only requires an overpotential of 255 mV to drive 50 mA cm-2 and a low Tafel slope of 57.49 mV dec-1. The calculation of density functional theory (DFT) further shows that the incorporation of Bi into NiFe LDH could obviously overcome the step of H2O adsorption during OER progress. This work provides a simple and effective strategy for improving the electrocatalytic performance of NiFe LDHs, which is of great practical significance.

Synthesis of block copolymer with cis-1,4-polybutadiene and isotactic-rich polystyrene using α-diimine nickel catalysts.

A series of styrene-butadiene di-block copolymers with high cis-1,4 unit content (greater than 92%) polybutadiene (PB) and isotactic-rich polystyrene (PS) (mmmm > 65%) was synthesized using α-diimine nickel catalysts (Ni-diimine). Four different Ni-diimine catalysts were synthesized via a complexing reaction between nickel (II) naphthenate and laboratory-made α-diimine ligands L1, L2, L3 and L4, which have different steric volume structures. The results indicate that the Ni-diimine catalyst prepared using the L4 ligand with a higher steric volume can effectively initiate the block polymerization of butadiene and styrene, and the resulting polymer has distinguished cis-1,4 structure unit PB and high isotactic-selective PS block. Differential scanning calorimetry and electrochemical performance tests show that these block copolymers with cis-1,4-regulated and isotactic-selective polymerization have advantages in terms of high-temperature and low-temperature resistance as well as corrosion resistance. Therefore, these copolymers are expected to be widely used in some harsh industrial environments.

A DFT/TDDFT Investigation on Fluorescence and Electronic Properties of Chromone Derivatives.

The development of quick and precise detection technologies for active compounds in vivo is critical for disease prevention, diagnosis and pathological investigation. The fluorescence signal of the fluorophore usually defines the probe's sensitivity to the chemical being examined. Many natural compounds containing flavone and isoflavone scaffolds exhibit a certain amount fluorescence, albeit with poor fluorescence quantum yields. Therefore, we used density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations to investigate the fluorescence characteristics of chromium-derived fluorophores in more depth. Different substituents are introduced at different positions of the chromone. As weak electron donor groups, alkyl and aromatic groups were discovered to have varying quantum yields on the fluorophore scaffold, and longer alkyl chains are favorable to enhance fluorescence quantum yield. In comparison to the amino group, substituted amino group can avoid group rotation, and the introduction of cyclic amines such as pyrrolidine and heterocyclic amines can improve optical characteristics. The electron-donating methoxy group at position 6 helps to increase the fluorescence quantum yield.

Ratiometric Sensing of Intracellular pH Based on Dual Emissive Carbon Dots.

Accurate monitoring of intracellular pH in living cells is critical for developing a better understanding of cellular activities. In the current study, label-free carbon dots (p-CDs), which were fabricated using a straightforward one-pot solvothermal treatment of p-phenylenediamine and urea, were employed to create a new ratiometric pH nanosensor. Under single-wavelength excitation (λex = 500 nm), the p-CDs gave dual emission bands at 525 and 623 nm. The fluorescent intensity ratio (I525/I623) was linearly related to pH over the range 4.0 to 8.8 in buffer solutions, indicating that the ratiometric fluorescence nanoprobe may be useful for pH sensing. In pH measurements, the p-CDs also demonstrated outstanding selectivity, reversibility, and photostability. Owing to the advantages outlined above, the nanoprobe was used to monitor the pH of HeLa cells effectively. The label-free CD-based ratiometric nanoprobe features comparatively easy manufacturing and longer excitation and emission wavelengths than the majority of previously reported CD-based ratiometric pH sensors, which is ultimately beneficial for applications in biological imaging.

Highly efficient red-emitting carbon dots as a "turn-on" temperature probe in living cells.

Nanothermometers, which can precisely detect the intracellular temperature changes, have great potential to solve questions concerning the cellular processes. Thus, the temperature sensors that provide fluorescent "turn-on" signals in the biological transparency window are of highly desirable. To meet these criteria, this work reported a new "turn-on" carbon dot (CD)-based fluorescent nanothermometry device for sensing temperature in living cells. The CDs that emit bright red fluorescence (R-CDs; λmax = 610 nm in water) were synthesized with o-phenylenediamine as carbon precursor via a facile solvothermal method. The R-CDs in water were almost nonfluorescent at 15 °C. As the temperature increased, the fluorescence intensity of R-CDs exhibited a gradual increase and the final enhancement factor was greater than 21-fold. The fluorescence intensity exhibited a linear response to temperature and a high-sensitive variation of ≈13.3 % °C-1 was detected within a broad temperature range of 28-60 °C. Moreover, the R-CD thermal sensors also exhibited high storage stability, excellent response reversibility and superior photo- and thermo-stability. Due to its good biocompatibility and "intelligent" response to external temperature, the nanothermometer could be applied for sensing temperature changes in biological media.

N-{2-[(2-chlorothieno[3,2-d]pyrimidin-4-yl)amino]ethyl}-3-methoxybenzamide: design, synthesis, crystal structure, antiproliferative activity, DFT, Hirshfeld surface analysis and molecular docking study.

The compound N-{2-[(2-chlorothieno[3,2-d]pyrimidin-4-yl)amino]ethyl}-3-methoxybenzamide (8) was synthesized by the condensation of 3-methoxybenzoic acid (7) with N1-(2-chlorothieno[3,2-d]pyrimidin-4-yl)ethane-1,2-diamine (6). This intermediate was prepared from methyl 3-aminothiophene-2-carboxylate (1) by the condensation with urea, chlorination with phosphorus oxychloride and then condensation with ethane-1,2-diamine. The crystal structure of the title compound was determined and the crystal of the title compound belongs to the tetragonal system, space group P4(3) with a = 9.4694(10) Å, b = 9.4694(10) Å, c = 18.886(3) Å, α = 90°, ß = 90°, γ = 90°. The optimized geometric bond lengths and bond angles obtained by using density functional theory (DFT) have been compared with X-ray diffraction values. The calculated HOMO and LUMO energies showed the character of the title compound. The molecular electrostatic potential (MEP) surface map of the related molecule was investigated with theoretical calculations at the B3LYP/6-311 + G(d,p) levels. A quantitative analysis of the intermolecular interactions in the crystal structures has been performed using Hirshfeld surface analysis. In addition, the title compound possesses marked inhibition against the proliferation of human colon cancer cell line HT-29 (IC50 = 1.76 µM), human lung adenocarcinoma cell line A549 (IC50 = 1.98 µM) and human gastric cancer cell line MKN45 (IC50 = 2.32 µM), displaying promising anticancer activitiy. The molecular docking studies revealed that the title compound may exhibit activity inhibiting PDB:3D15.Communicated by Ramaswamy H. Sarma.

A new type of zinc ion hybrid supercapacitor based on 2D materials.

Zinc ion hybrid supercapacitors (ZICs) are truly promising competitors in prospective extensive electrochemical energy storage fields due to their cost-effectiveness, environmentally friendly nature, inherent security, and satisfying gravimetric energy density. Thus, several investigation endeavors have been dedicated to the construction and exploitation of high-performance ZICs. However, the exploitation of ZICs is still in its preliminary stage and there are many problems that need to be overcome before their potential can be fully realized. Recently, 2D materials with a fascinating structure and intriguing features have attracted enormous attention for applications in ZICs with prominent improvement from charge storage capacity to reaction kinetics. In this article, the recent research progress in 2D materials and their composites in the pursuit of high-performance ZICs is systematically reviewed, focusing on the possible charge storage mechanism of ZICs. In addition, the influence of the structure of 2D materials and their composites on the electrochemical performance and the zinc ion storage mechanism is analyzed. Finally, the challenges and prospects of the application of 2D materials and their composites in high-performance ZICs are presented.

Correction: Formic acid catalyzed isomerization of protonated cytosine: a lower barrier reaction for tautomer production of potential biological importance.

Correction for 'Formic acid catalyzed isomerization of protonated cytosine: a lower barrier reaction for tautomer production of potential biological importance' by Lingxia Jin et al., Phys. Chem. Chem. Phys., 2017, 19, 13515-13523.

Formic acid catalyzed isomerization of protonated cytosine: a lower barrier reaction for tautomer production of potential biological importance.

Tautomerism in nucleotide bases is one of the possible mechanisms of DNA mutation. In spite of numerous studies on the structure and energy of protonated cytosine tautomers, little information is available on the process of their intra- and intermolecular tautomerizations. The catalytic ability of H2O, HCOOH, and the HCOOHH2O group to facilitate the tautomerism of the Cyt2t+ to CytN3+ isomer has been studied. It is shown that the activation free energies of tautomerism in the gas phase are 161.17, 58.96, 26.06, and 15.69 kJ mol-1, respectively, when the reaction is carried out in the absence and presence of H2O, HCOOH, or the HCOOHH2O group. The formation of a doubly hydrogen bonded transition state is central to lowering the activation free energy and facilitating the intramolecular hydrogen atom transfer that is required for isomerization. In the aqueous phase, although the solvent effects of water significantly decrease the activation free energy of intramolecular tautomerization, the isomerization of the Cyt2t+ to CytN3+ isomer remains unfavorable, and the HCOOH and HCOOHH2O group mediated mechanisms are still more favorable. Meanwhile, conventional transition state theory (CTST) followed by Wigner tunneling correction is then applied to estimate the rate constants. The rate constant with Wigner tunneling correction for direct tautomerization is obviously smaller than that of HCOOH-mediated tautomerization, which is the most plausible mechanism. Finally, another important finding is that the product complex (CytN3+HCOOH) is in the rapid tautomeric equilibrium with the reaction complex (Cyt2t+HCOOH) (τ99.9% = 3.84 × 10-12 s), which is implemented by the mechanism of the concerted synchronous double proton transfer. Its lifetime of the formed CytN3+HCOOH complex (τ = 8.33 × 10-9 s) is almost one order of magnitude larger than the time required for the replication machinery to forcibly dissociate a base pair into the monomers during DNA replication (several ns), which is further dissociated into the CytN3+ and HCOOH monomers. The results of the present study demonstrate the feasibility of acid catalysis for DNA base isomerization reactions that would otherwise be forbidden.

4-Hy-droxy-N'-[1-(2-hy-droxy-phen-yl)ethyl-idene]benzohydrazide.

In the title compound, C(15)H(14)N(2)O(3), there is an intra-molecular O-H⋯N hydrogen bond and the dihedral angle between the two aromatic rings is 13.9 (3)°. In the crystal structure, mol-ecules are stabilized by inter-molecular O-H⋯O and N-H⋯O hydrogen bonds.

N'-[1-(2-Hy-droxy-phen-yl)ethyl-idene]-2-meth-oxy-benzohydrazide.

There are two independent mol-ecules in the asymmetric unit of the title compound, C(16)H(16)N(2)O(3), in which the dihedral angles between the two aromatic rings are 13.0 (3) and 6.4 (3)°. Intra-molecular O-H⋯N and N-H⋯O hydrogen bonds are observed in both mol-ecules, forming S(6) rings in all cases.

Dibromido{2-[1-(cyclo-propyl-imino)-eth-yl]pyridine}-zinc(II).

In the title compound, [ZnBr(2)(C(10)H(12)N(2))], the Zn(2+) ion is coordinated by the N,N'-bidentate Schiff base ligand and two bromode ions in a distorted tetra-hedral arrangement. The dihedral angle between the pyridine and the cyclo-propyl rings is 95.4 (8)°.

Bis[2-(cyclo-pentyl-imino-meth-yl)-5-meth-oxy-phenolato]copper(II).

The title compound, [Cu(C(13)H(16)NO(2))(2)], is a mononuclear copper(II) complex derived from the Schiff base ligand 2-(cyclo-pentyl-imino-meth-yl)-5-meth-oxy-phenol and copper acetate. The Cu(II) atom is four-coordinated by the phenolate O atoms and imine N atoms from two Schiff base ligands, in a highly distorted square-planar geometry. The O- and N-donor atoms are mutually trans and the dihedral angle between the two benzene rings is 55.8 (3)°.

Bis{1-[3-(diethyl-ammonio)-propyl-imino-meth-yl]naphthalen-2-olato}nickel(II) dinitrate.

The asymmetric unit of the title compound, [Ni(C(18)H(24)N(2)O)(2)](NO(3))(2), consists of one half of the centrosymmetric nickel(II) complex cation and a nitrate anion. The Ni(II) atom, lying on an inversion center, is four-coordinated by the phenolate O atoms and imine N atoms of two Schiff base ligands, forming a square-planar geometry. The O- and N-donor atoms are mutually trans. In the crystal structure, the nitrate anions are linked to the complex cations by inter-molecular N-H⋯O hydrogen bonds.

{2-[2-(Isopropyl-amino)-ethyl-imino-meth-yl]-5-meth-oxy-phenolato}(thio-cyanato--κN)nickel(II).

In the title mononuclear complex, [Ni(C(13)H(19)N(2)O(2))(NCS)], the Ni(II) ion is coordinated by one phenolate O atom, one imine N atom, and one amine N atom of a 2-[2-(isopropyl-amino)-ethyl-imino-meth-yl]-5-meth-oxy-phenolate Schiff base ligand, and by one N atom of a thio-cyanate ligand, forming a slightly distorted square-planar geometry.

N'-(5-Bromo-2-hydr-oxy-3-methoxy-benzyl-idene)-4-hydr-oxy-3-methoxy-benzohydrazide dihydrate.

In the title compound, C(16)H(15)BrN(2)O(5)·2H(2)O, the dihedral angle between the two aromatic rings is 2.9 (2)° and an intra-molecular O-H⋯N hydrogen bond is observed. One of the water mol-ecule is disordered over two positions, with occupancies of 0.83 (3) and 0.17 (3). In the crystal structure, mol-ecules are linked into a three-dimensional network by inter-molecular O-H⋯O, O-H⋯(O,O), O-H⋯N and N-H⋯O hydrogen bonds. π-π inter-actions involving Br-substituted benzene rings, with a centroid-centroid distance of 3.552 (3) Šare also observed.

N'-(4-Hydr-oxy-3-methoxy-benzyl-idene)-4-methoxy-benzohydrazide monohydrate.

In the title compound, C(16)H(16)N(2)O(4)·H(2)O, the dihedral angle between the two aromatic rings is 19.6 (2)°. In the crystal structure, mol-ecules are linked into a three-dimensional network by inter-molecular N-H⋯O, O-H⋯N and O-H⋯O hydrogen bonds.

N'-(3-Eth-oxy-2-hydroxy-benzyl-idene)-4-hydr-oxy-3-methoxy-benzohydrazide monohydrate.

In the title compound, C(17)H(18)N(2)O(5)·H(2)O, the dihedral angle between the two aromatic rings is 7.86 (7)° and an intra-molecular O-H⋯N hydrogen bond is observed. In the crystal structure, mol-ecules are linked into a three-dimensional network by inter-molecular O-H⋯O and N-H⋯O hydrogen bonds.

4-Hydr-oxy-N'-(2-hydr-oxy-3-methoxy-benzyl-idene)benzohydrazide mono-hydrate.

In the title compound, C(15)H(14)N(2)O(4)·H(2)O, the dihedral angle between the two aromatic rings is 33.3 (5)°. The meth-oxy group is twisted slightly away from the attached benzene ring [C-O-C-C = 13.8 (9)°]. An intra-molecular O-H⋯N hydrogen bond is observed. In the crystal structure, the mol-ecules are linked into a two-dimensional network parallel to the (010) plane by inter-molecular N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds.