Shuai-Hua Wang

Low carbon steel with nanostructured surface layer induced by high-energy shot peening

The materials used in this work is a low carbon steel plate of 1.5 mm thick, its chemical compositions contain (mass, %) 0.11C, 0.24Si, 0.35Mn, 0.018P and 0.014S. The initial grain size of the low carbon steel is in the range of 20 ; 40 mm. Samples of 100 3 100 mm 2 were prepared for the HESP treatment. The principle of the HESP treatment used in the present work is similar to that of the USP method (9), but with a lower frequency (3 kHz) and bigger shots (diameter of 8 mm). The entire surface of the sample to be treated is peened by the flying shots with a high energy. The processing durations are 30, 60, 90 and 180 min, respectively. Surface structure of peened samples and structural evolution along the depth of the sample peened for 180 min were studied using X-ray diffraction (XRD) with CuKa radiation in a Rigaku D/max-2400 X-ray diffractometer. The average grain size and the mean microstrain were calculated from XRD line

Eu3+-doped Tb3+ metal–organic frameworks emitting tunable three primary colors towards white light

A new bifunctional tetrazolate-5-carboxylate ligand has been prepared and employed in assembling 2-D Eu(III)–Zn(II) and Tb(III)–Zn(II) isostructural heterometallic MOFs with a (3,6)-connected kgd topology. The ligand in Tb3+ MOFs not only shows an antenna effect to transfer absorbed energy to Tb3+ centers to emit characteristic luminescence but also maintains good blue luminescent properties. Further, we have realized a rational design strategy to construct a series of Eu3+-doped Tb3+ MOFs emitting tunable three primary colors (RGB: red–green–blue) towards white light with high color rendering index and favorable correlated color temperature.

Homochiral Zinc(II) Coordination Compounds Based on In-Situ-Generated Chiral Amino Acid–Tetrazole Ligands: Circular Dichroism, Excitation Light-Induced Tunable Photoluminescence, and Energetic Performance

We employed two pairs of new in-situ-generated chiral amino acid-tetrazole ligands in constructing homochiral Zn(II) coordination compounds: [Zn(tzet)]n (1a for (S)-tzet and 1b for (R)-tzet, H2tzet = N-[2-(1H-tetrazol-5-yl)ethyl]tryptophan) and [Zn(tzep)(H2O)2]·H2O (2a for (S)-tzep and 2b for (R)-tzep, H2tzep = N-[2-(1H-tetrazol-5-yl)ethyl]proline), which were hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Structural analysis reveals that 1 features a 2D homochiral framework generated by both tetrazolate and carboxylate bridges in tzet(2-) ligands. The isolated structure of 2 is stabilized by extensive hydrogen bonds, which leads to formation of a supramolecular 2D architecture. The absolute configuration induced at the nitrogen atoms of 1 and 2 is strictly related to the neighboring chiral carbon atoms by hydrogen-bond interactions. To further investigate their chirality, the combined experimental and theoretical analyses of circular dichroism spectra reveal the absolute configurations and nature of the Cotton effects. Solid-state excitation and emission spectra for 1 and 2 at room temperature were investigated with relevant density of states calculation, and tunable photoluminescence emission of 1 under different excitation wavelengths was discussed. As nitrogen-rich tetrazolate compounds, 1 and 2 possess higher enthalpies of combustion and may serve as a new family of promising energetic materials.

Structures and photoluminescence of zinc(II) coordination polymers based on in situ generated 1H-tetrazolate-5-propionic acid ligands

Hydrothermal reaction of ZnCl2, NCCH2CH2COONa and NaN3, in the absence/presence of auxiliary ligand 2,2′-bipy/4,4′-bipy, gave birth to three novel coordination polymers, namely, [Zn(tzp)]n (1), [Zn2(tzp)(N3)(OH)(2,2′-bipy)]n (2) and [Zn2(tzp)2(4,4′-bipy)]n (3) (H2tzp = 1H-tetrazolate-5-propionic acid). The tzp2− ligand was in situ generated through the [2 + 3] cycloaddition reaction of nitrile and azide, which was first untilized to synthesize coordination compounds. Polymer 1 behaves as a three-dimensional (3-D) network built up by the fusion of one-dimensional (1-D) pseudo-channels formed by the linkage of tzp2− ligands and tetrahedral Zn nodes. When the chelating 2,2′-bipy was introduced into the reaction system, a two-dimensional (2-D) puckered network 2 was constructed, where 1-D pseudo-channels, similar to those in 1, are bridged by azide ions in an end-on (EO) mode. Employment of the linear bridging 4,4′-bipy ligand as the auxiliary ligand resulted in the formation of an unusual 3-D polymer 3, where the connection of Zn and tzp2− produces a 2-D network, which are further joined by 4,4′-bipy. The tzp2− ligands in 1–3 show the flexible conformations and different coordination modes, with the tetrazolate group being the 1,4-N mode and the carboxylate group being the syn–anti, syn–syn and monodentate mode, respectively. The results suggest that the flexible nature of the tzp2− ligand as well as the introduction of auxiliary ligands is responsible for the formations of 1–3. Their photoluminescent properties and thermal stabilities have also been discussed.

Anion-directed self-assembly of Cu(II) coordination compounds with tetrazole-1-acetic acid: syntheses in ionic liquids and crystal structures

Reaction of tetrazole-1-acetic acid (1-Htza) with a Cu(II) salt in ionic liquids with different anions, [BMIM]X (BMIM = 1-butyl-3-methylimidazolium; X = Br−, BF4−, NTf2− (NTf2− = bis((trifluoromethyl)sulfonyl)amide)), afforded five Cu(II) coordination compounds, [Cu2(1-tza)4]Br·H3O·1/3H2O (1), [Cu2(1-tza)4]BF4·H3O·H2O (2), [Cu(μ2-Cl)(1-tza)(1-Htza)(H2O)]·0.5H2O (3), [CuCl(μ2-Cl)(1-Htza)2(H2O)]·H2O (4), and [CuCl2(1-Htza)2]·H2O (5). Single-crystal X-ray diffraction analyses reveal that 1–5 display various structures, and the 1-tza− ligand exhibits diverse coordination modes. Compounds 1 and 2 possess higher dimensional structures (a 2-D neutral Kagome topology network for 1 and a 3-D lvt-type topology framework for 2) with fully deprotonated 1-tza− ligands. Compounds 3–5 display lower dimensional structures (1-D, 1-D and 0-D for 3, 4 and 5, respectively) with partly or fully protonated 1-Htza. The anions of ionic liquids have significant influences on the final molecular architectures, which arise from different water miscibility of ionic liquids.

Hydrothermal syntheses, crystal structures and magnetic properties of four Mn(II) and Co(II) coordination polymers generated from new carboxylate-introduced 1,2,3-triazole ligands

A new carboxylate-introduced 1,2,3-triazole, 1-(3,5-dicarboxyphenyl)-4-carboxy-1H-1,2,3-triazole (H3dcpct), was synthesized by 1,3-dipolar cycloaddition of a terminal alkyne to azide in the presence of a Cu(II) salt. Hydrothermal reaction of H3dcpct and Mn(NO3)2·6H2O or Co(NO3)2·6H2O in different NaOH/H3dcpct molar ratios afforded four new coordination polymers [Mn(dcpt)(H2O)2]·0.25H2O 1, [Mn(dcpt)(H2O)] 2, [Co(dcpt)(H2O)2]·H2O 3 and [Co(H2O)6][Co2(dcpct)2(H2O)6]·2H2O 4 (H2dcpt = 1-(3,5-dicarboxyphenyl)-1H-1,2,3-triazole). The in situ hydrothermal decarboxylation of H3dcpct into H2dcpt in 1–3 was found and its possible mechanism is proposed. In 1 and 3, dcpt2− ligands bridge Mn(II) and Co(II) ions, respectively, to give two similar 2D layered structures with a (6,3)-connected network topology. Polymer 2 displays a whole achiral 3D open framework with both chiral and achiral channels in the same direction and possesses an unprecedented (3,6)-connected (4·82)(42·812·10) network topology. The structure of 4 features a 1D chained net, in which no decarboxylation occurred. Variable-temperature magnetic susceptibility data show that 1 exhibits a weak ferromagnetic interaction and 2 manifests an overall antiferromagnetic interaction between their respective Mn(II) ions, while 3 and 4 display an antiferromagnetic interaction between Co(II) ions and/or spin-orbital coupling. The thermal stabilities of all obtained polymers have also been examined.

Hydrothermal syntheses, crystal structures and physical properties of a new family of energetic coordination polymers with nitrogen-rich ligand N-[2-(1H-tetrazol-5-yl)ethyl]glycine

Hydrothermal reaction of N-(2-cyanoethyl)glycine and NaN3 with corresponding metal salts yielded three energetic coordination polymers: [Zn(tzeg)]n1 and [M(tzeg)(H2O)]n (M = Cd2+ for 2, Cu2+ for 3) (H2tzeg = N-[2-(1H-tetrazol-5-yl)ethyl]glycine), which were characterized by single-crystal X-ray diffraction. Nitrogen-rich tzeg2− ligand is a new in situ generated organic compound through [2 + 3] cycloaddition reaction of nitrile and azide, which adopts two different coordination modes in 1–3. Polymer 1 features an achiral 3D network built up by interweaving of left/right-handed helical channels. Isostructural 2 and 3 exhibit an achiral 2D network formed alternately by left/right-handed helical chains. As nitrogen-rich energetic materials, 1 and 3 possess higher enthalpies of combustion (ΔHc), which are −12.054 and −11.583 kJ g−1, respectively, than the classical energetic compounds 1,3,5-trinitro-1,3,5,-triazine (RDX, −9.6 kJ g−1) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX, −9.44 to −9.88 kJ g−1). The solid-state excitation and emission spectra for 1–3 were investigated at room temperature, which reveals ligand-centered luminescent emissions in the intensity order of 2 > 1 > 3. Variable-temperature magnetic susceptibility data show that 3 displays a weak antiferromagnetic interaction mainly resulting from magnetic exchange coupling between Cu2+ ions through double tetrazolato bridges.

Tetraalkylammonium cations as templates in the construction of two cadmium(II) metal–organic frameworks

Hydrothermal reaction of cadmium salts with HATZ in the presence of R4NBr (R = Et, Pr) led to two organic cation templated Cd(II) MOFs, (Et4N)[Cd6Br5(ATZ)8]·H2O (1) and (Pr4N)[Cd4Br5(ATZ)4] (2) (HATZ = 5-amino-tetrazolate, Et = ethyl and Pr = propyl), which are the first examples of tetraalkylammonium cations templated N-heterocyclic ligand based MOFs. These two MOFs have been fully characterized by single crystal X-ray diffraction, XRD, TGA, IR, elemental analysis, photoluminescence spectra and combustion heat measurement. The anionic frameworks of 1 and 2 are three- and two-dimensional, respectively. Topological analyses show that compound 1 exhibits an unprecedented binodal (4,10)-connected network, which is a subnet of the (12,12)-connected tcj net, and compound 2 is a 2-D uninodal four-connected network when the Cd6 clusters in these two MOFs are viewed as nodes. Moreover, compound 1 maybe have potential application as an energetic material due to its high enthalpy of formation.

Excitation wavelength-induced color-tunable and white-light emissions in lanthanide(III) coordination polymers constructed using an environment-dependent luminescent tetrazolate–dicarboxylate ligand

An alternative approach to fabricate color-tunable and white-light-emitting lanthanide(III) coordination polymers (LnCPs) is demonstrated by employing a selective light-emitting tetrazolate–dicarboxylate ligand, which displays different color emissions when coordinated to different lanthanide(III) ions. The emission colour of the obtained LnCPs can be modulated from orange to white by simply adjusting the excitation wavelengths. White-light emissions, with high color rendering index and favorable correlated color temperature, have been successfully realized in new 2D single-component Sm(III) and two-component Eu(III)-doped Gd(III) coordination polymers excited at specific excitation wavelengths.

Fluorescence and photochromic properties of a series of new Zn(II)/Cd(II) coordination compounds with a flexible semi-rigid tetrazole–viologen derivative

Photoluminescent coordination compounds have appealing applications in light-emitting and photoactive materials, but there exist some difficulties in the tuning and domination of luminescence by changing the structures. In this work, diverse luminescence was realized by the rational design and controllable construction of a series of Zn(II)/Cd(II) coordination compounds from an isolated binuclear moiety, a 1D zigzag chain, a 1D ladder-like chain and a 3D 3,4-connected topology network based on a flexible semi-rigid tetrazole–viologen ligand. Especially, the isolated binuclear compound shows an interesting photochromic molecular system that involves electron transfer from the N3− ions and Cl atoms to the tetrazole–viologen ligand and exhibits fluorescence and second-order nonlinear optical property variation upon ultraviolet light irradiation.