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Eu2+ was used to substitute Ca in the orthorhombic KCoO2-type layered CaTiN2 to form a Ca1−xEuxTiN2 solid solution, which showed a limited substitution around x = 0.35 with the tetragonality enhanced but the orthorhombic symmetry retained and inaccessibility for the end member EuTiN2. This was in contrast with the full solid solution Ca1−xSrxTiN2, which realized a structural transition from orthorhombic to tetragonal at x = 0.5, even though Eu2+ and Sr2+ ions have similar sizes. The Eu substitution for Ca reduced the dielectric permittivity of CaTiN2 owing to the reduced structural distortion arising from the enhanced tetragonality with the substitution. First-principle theoretical calculations on the total energies and formation energies considering the 4f electrons of Eu ions and the related magnetism were performed to understand the structural stability of the hypothetical EuTiN2. Compared with CaTiN2 and SrTiN2, EuTiN2 has much higher formation energies, making it inaccessible at high temperature. The evolutions of the experimentally observed and calculated lattice parameters of the Ca1−xEuxTiN2 solid solution showed a preference for the orthorhombic phase over the tetragonal phase for the hypothetical EuTiN2, revealing a different coordination chemistry of Eu2+–N to Eu2+–O through the comparison of the structural variations of ATiN2 and ATiO3 (A = Ca, Sr, Eu). [ABSTRACT FROM AUTHOR]

Due to their unique structure, abundant properties and potential applications, low-dimensional materials with covalently bonded building blocks through van der Waals (vdW) interactions have sparked widespread interest. Recently, the bulk phase NbS4 consisting of one-dimensional (1D) chains has been synthesized successfully, adding a new member to the group V metallic polychalcogenide family. In the present study, based on density functional theory calculations, we obtained a better understanding of the stability, mechanical properties, electronic structures, transport properties and optical performances of the bulk phase NbS4. Furthermore, the possibility of exfoliating 1D single-chain nanowires from the bulk phase was uncovered. Both bulk phase and 1D nanowires show dynamic, thermal, and mechanical stabilities. The bulk phase possesses an indirect band gap of 1.39 eV with high anisotropic carrier mobilities of 471.814 cm2 s−1 v−1 for electrons (along the b axis direction) and 546.92 cm2 s−1 v−1 for holes (along the a axis direction). The single-chain nanowire exhibits remarkable flexibility and can resist 24% tensile strain along the chain direction. The decreased dimension from the bulk phase to the individual 1D chain not only makes the band gap increase to 1.81 eV but also results in an indirect-to-direct band gap transition, indicating a strong quantum confinement effect. The 1D single-chain nanowire also shows high carrier mobilities of 111.91 cm2 s−1 v−1 for electrons and 316.63 cm2 s−1 v−1 for holes along the chain direction. In addition, both bulk phase and 1D nanowire display excellent visible light absorption performance along the chain direction and the absorption coefficients reach the order of 106 and 105 cm−1. These promising properties render quasi 1D NbS4 as candidate materials for nanoscale applications in high-performance optoelectronic and nanoelectronic devices. The predicted unconventional properties of NbS4 not only provide a meaningful complement to the fascinating quasi 1D material family, but also will attract extensive interest from a wide audience to explore unanticipated properties and design new nanoscale devices based on NbS4. [ABSTRACT FROM AUTHOR]

The development of information technology puts forward huge demand for electronic materials with high dielectric constants; first-principles calculations and simulations have been demonstrated as an efficient technique for screening and exploring novel dielectric materials. In the present study, first-principles calculations combined with density functional perturbation theory are employed to study the dielectric properties of two newly discovered layered nitrides SrHfN2 and SrZrN2 under strain. By analyzing the evolution of lattice distortion, dielectric constant, Born effective charge, and phonon modes along with the applied strain, we find that the biaxial strain and isotropic strain can effectively modulate the dielectric constant. The two nitrides SrHfN2 and SrZrN2 are dynamically stable up to biaxial tensile strains of 2.1% and 1.8%, and the dielectric constants have been enlarged to about 500 and 2000. Furthermore, the dielectric constant is dramatically enhanced by 15 (9) times to a maximum value of ∼2600 (2700) under an isotropic tensile strain of 1.2% (0.7%) for SrHfN2 (SrZrN2), which is mainly due to the softening of the lowest-frequency infrared-active phonon mode and the increasing octahedral distortion degree. Particularly, the ionic contribution of the dielectric constant shows very remarkable anisotropy and plays a dominant role in the change of the dielectric constant, whose in-plane components exhibit giant enhancement by 18 (10) times for SrHfN2 (SrZrN2). This work not only sheds light on the experimentally observed high dielectric constants of SrHfN2 and SrZrN2, but also provides an effective route to regulate the anisotropic dielectric constants by applied strain, which indicates promising applications in optical and electronic devices. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) layered palladium dichalcogenides PdX2 (X = S and Se) have attracted increasing interest due to their tunable electronic structure and abundant physicochemical properties. Recently, as the sister material of PdX2, PdSSe has received increasing attention and shows great promise for technological applications and fundamental research. In the present study, we focus on the layer-dependent geometry, electronic structure, and optical properties of PdSSe using first-principles calculations. The lattice shrinkage effect present in the 2D structure is suppressed with increasing number of layers. Attributed to the strong interlayer coupling interactions, the band gap decreases from 2.30 to 0.83 eV with increased thickness. Particularly, the dispersion of the band edges on the high symmetry path changes considerably from the monolayer to bilayer PdSSe, resulting in shifts of the conduction band minimum and valence band maximum. The multilayer PdSSe shows band convergence feature with multi-valley for the conduction band, which are maintained with reduced effective mass. Furthermore, the increasing number of layers drives a wider absorption range in the visible light region, and the light absorption capability increases from ∼10% to ∼30%. Meanwhile, the band edge positions of the multilayer PdSSe are more appropriate for photocatalytic water splitting. Our theoretical study reveals the enhanced valley convergence, conductivity and optical absorption performance of the few-layer PdSSe, which suggests its promising application in thermoelectric conversion, solar harvesting and photocatalysis. [ABSTRACT FROM AUTHOR]

Iridium oxides (iridates) provide a good platform to study the delicate interplay between spin–orbit coupling (SOC) interactions, electron correlation effects, Hund's coupling and lattice degrees of freedom. An overwhelming number of investigations primarily focus on tetravalent (Ir4+, 5d5) and pentavalent (Ir5+, 5d4) iridates, and far less attention has been paid to iridates with other valence states. Here, we pay our attention to a less-explored trivalent (Ir3+, 5d6) iridate, K0.75Na0.25IrO2, crystallizing in a triangular lattice with edge-sharing IrO6 octahedra and alkali metal ion intercalated [IrO2]− layers, offering a good platform to explore the interplay between different degrees of freedom. We theoretically determine the preferred occupied positions of the alkali metal ions from energetic viewpoints and reproduce the experimentally observed semiconducting behavior and nonmagnetic (NM) properties of K0.75Na0.25IrO2. The SOC interactions play a critical role in the band dispersion, resulting in NM Jeff = 0 states. More intriguingly, our electronic structure not only uncovers the presence of intrinsic in-gap states and nearly free electron character for the conduction band minimum, but also explains the abnormally low activation energy in K0.75Na0.25IrO2. Particularly, the band edge can be effectively modulated by mechanical strain, and the in-gap states feature enhanced band-convergence characteristics by 6% compressive strain, which will greatly enhance the electrical conductivity of K0.75Na0.25IrO2. The present work sheds new light on the unconventional electronic structures of trivalent iridates, indicating their promising application as a nanoelectronic and thermoelectric material, which will attract extensive interest and stimulate experimental works to further understand the unprecedented electronic structures and exploit potential applications of the triangular trivalent iridate. [ABSTRACT FROM AUTHOR]

In this work, four different bis(imidazole) ligands, namely 1,4-bis(1-imidazolyl)benzene (bib), 4,4′-bis(1-imidazolyl)biphenyl (bibp), 1,4-bis (imidazol-1-ylmethylene)benzene) (bimb) and 4,4′-bis(imidazol-1-yl)diphenyl ether (bidpe), were used as the second ligand to give rise to the structural diversity of a coordination polymer based on the cobalt-miipa (H2miipa = 5-(2-methylimidazol-1-yl) isophthalic acid) system. In compound 1, miipa2− coordinates to Co(II) atoms to form the Co-miipa 3D network. On introducing linear bis(imidazole) ligands with different lengths and rigidities into the Co(II)-miipa system, the obtained compounds 2–4 form similar three-fold interpenetrating 3D MOFs constructed from the Co(II)-miipa layers pillared by bis(imidazole) ligands. While introducing the V-shaped half-flexible bis(imidazole) ligands, the obtained compound 5 exhibits a 2D double-layered network built from the Co(II)-miipa 1D quadrangular prism linked by the bis(imidazole) ligand. Each 2D double layer is further interlocked with two neighboring ones to produce an interesting 3D framework. Significantly, CoNC-5 derived from a mixture of dicyandiamide (DCD) and compound 5 with a low void volume shows a superior electrocatalytic performance for the oxygen reduction reaction. The Eonset (0.974 V) and E1/2 (0.830 V) of CoNC-5 in O2-saturated 0.1 M KOH at 1600 rpm and 5 mV s−1 are superior to those of Pt/C (0.968 and 0.799 V). The JL value of CoNC-5 (JL = 5.29 mA cm−2) is higher than that of Pt/C (5.09 mA cm−2). [ABSTRACT FROM AUTHOR]

The urothermal reactions of Co(II)/Zn(II) salts with the diverse carboxylic acid and 1,3,5,-tris(1-imidazolyl)benzene(tib) ligands afforded three novel MOFs, namely, [Co3(tib)2(abdc)2(ox)]2·6H2O (1), [Co3O(tib)(abdc)2(DMI)]·2DMI·2H2O (2) and [Zn3I2(tib)2(napdc)2]·2DMI·2H2O (3), (H2abdc = 5-amino-1,3-benzenedicarboxylate, H2napdc = 1,4-naphthalene dicarboxylic acid and DMI = 1,3-dimethyl-2-imidazolidinone). In compounds 1 and 2, the Co(II) atoms are connected by polycarboxylate ligands to form two-dimensional (2D) layers that are pillared by tib ligands leading to the formation of 3D porous frameworks. In compound 3, the Zn(II) atoms are linked by tib ligands to form one-dimensional ribbon-like chains which are further connected by polycarboxylate ligands, making a 3D framework possible. Compound 1 can selectively adsorb unsaturated hydrocarbon molecules (C2H2 and C2H4) and saturated hydrocarbon molecules (C2H6 and CH4). Specifically, compound 1 has high IAST selectivity for acetylene and methane (0.50 : 0.50, v/v) at 273 K and 1 bar. DFT calculations reveal that the π-conjugated hexagonal carbon ring may be the primary adsorption site because there are π–π interactions between the unsaturated hydrocarbon molecules (C2H2 and C2H4) and the π-conjugated hexagonal carbon ring in the framework of compound 1. [ABSTRACT FROM AUTHOR]

The urothermal reactions of Co(II)/Zn(II) salts with the diverse carboxylic acid and 1,3,5,-tris(1-imidazolyl)benzene(tib) ligands afforded three novel MOFs, namely, [Co3(tib)2(abdc)2(ox)]2·6H2O (1), [Co3O(tib)(abdc)2(DMI)]·2DMI·2H2O (2) and [Zn3I2(tib)2(napdc)2]·2DMI·2H2O (3), (H2abdc = 5-amino-1,3-benzenedicarboxylate, H2napdc = 1,4-naphthalene dicarboxylic acid and DMI = 1,3-dimethyl-2-imidazolidinone). In compounds 1 and 2, the Co(II) atoms are connected by polycarboxylate ligands to form two-dimensional (2D) layers that are pillared by tib ligands leading to the formation of 3D porous frameworks. In compound 3, the Zn(II) atoms are linked by tib ligands to form one-dimensional ribbon-like chains which are further connected by polycarboxylate ligands, making a 3D framework possible. Compound 1 can selectively adsorb unsaturated hydrocarbon molecules (C2H2 and C2H4) and saturated hydrocarbon molecules (C2H6 and CH4). Specifically, compound 1 has high IAST selectivity for acetylene and methane (0.50 : 0.50, v/v) at 273 K and 1 bar. DFT calculations reveal that the π-conjugated hexagonal carbon ring may be the primary adsorption site because there are π–π interactions between the unsaturated hydrocarbon molecules (C2H2 and C2H4) and the π-conjugated hexagonal carbon ring in the framework of compound 1. [ABSTRACT FROM AUTHOR]

Emerging two-dimensional (2D) noble-metal dichalcogenide (NMDC) PdX2 (X = S and Se) materials crystallize in an unusual orthorhombic structure (2O phase) with unique pentagons and PdX4 planar squares as building blocks, and have attracted tremendous attention in recent years for their novel physical and chemical properties, as well as promising applications in the future. Motivated by the attractive properties and encouraging applications of PdX2 materials, we explore the 2O phase NMDC material PdSSe using particle swarm optimization algorithms combined with first-principles calculations. We not only uncover three stable low-energy bulk phases, but also predict two polymorphs of the 2D monolayer exfoliated from the bulk phases, exhibiting mechanical, dynamic, and thermal stabilities. Due to its novel puckered pentagonal structure, the PdSSe monolayer exhibits flexible mechanical properties with anisotropic Young's modulus and Poisson's ratio. The bandgaps of the two polymorphs of the 2D pentagonal PdSSe monolayer are 2.10 and 2.06 eV, and their band-edges perfectly straddle the redox potential of water. Furthermore, these materials possess excellent light absorption in the visible and ultraviolet regions, and the absorption coefficients reach the order of 106 cm−1. More importantly, the predicted materials exhibit highly desirable carrier mobilities and anisotropy, which can promote the separation of the photogenerated electrons and holes, and effectively reduce the probability of recombination, thus remarkably promoting photocatalytic water splitting. These excellent properties enable PdSSe monolayers as candidate materials for promising applications in high-performance optoelectronic and nanoelectronic devices. The predicted unconventional properties of PdSSe not only supply a meaningful complement to the fascinating NMDC materials of PdSe2 and PdS2, but also will attract extensive interest from a wide audience to explore unanticipated properties and design new functional devices based on PdSSe. [ABSTRACT FROM AUTHOR]

Different aromatic polycarboxylic acids are employed as auxiliary ligands to give rise to structural diversities in Co(II)-tpt (tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine) frameworks. By introducing various secondary aromatic polycarboxylate anions, namely, biphenyl-3,4′,5-tricarboxylic acid (H3bpt), 1,3,5-benzenetricarboxylic acid (H3btc) and 2,6-dimethyl pyridine-3,5-dicarboxylic acid (H2dmdcpy) into the Co(II)-tpt system (tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine), four new complexes [Co3(tpt)2(Hbpt)3]·0.5DMDP (1) (DMDP = N,N′ = dimethylpropyleneurea), [Co3(btc)2(tpt)(H2O)3]·3H2O (2), [Co2(btc)(tpt)2Cl]·DMDP·1.5H2O (3) and [Co(tpt)(dmdcpy)]·H2O (4) were obtained. Complexes 1 and 2 reveal amazing 3D networks in which the polycarboxylate ligands and Co(II) ions connect with each other to form regular 3D porous frameworks with 1D cylindrical channels partitioned by virtue of the tpt ligands. Complexes 3 and 4 exhibit unusual 3D frameworks constructed from the Co–polycarboxylate layers pillared by tpt ligands. In addition, compound 1 was chosen as a precursor to prepare Co, N-codoped porous carbon materials (denoted as CoNC) as an eletrocatalyst for oxygen reduction reactions. In particular, the effect of different nitrogen sources on the electrocatalytic performance of MOF derived carbon materials was investigated. We found that although different nitrogen-containing ligands have a certain effect on the electrocatalytic performance of the synthesized CoMOF derived carbon materials, the additional nitrogen source has a significant effect on it. CoNC-A derived from compound 1 exhibits greater limiting current density than that of a Pt/C catalyst, while CoNC-B derived from a mixture of compound 1 and dicyandiamide shows almost identical onset potential but remarkably more positive half-wave potential as well as higher limiting current density as compared to commercial Pt/C catalysts. [ABSTRACT FROM AUTHOR]

By introducing multiple molecule/intermolecular dynamic reversible hydrogen bonds into the polydimethylsiloxane elastomer system, a solid polymeric electrolyte with high ion conductivity (2.5 × 10−4 S cm−1) and a stable electrochemical window (>5 V) shows a fast self-healing speed. [ABSTRACT FROM AUTHOR]

Three 3D polymeric complexes containing polynuclear Co(II) units, [Co3(bpda)3(bib)2]·H2O (1), [Co5(OH)2(H2O)2(bpda)4(bib)2]·2H2O (2), and [Co2(OH)(bib)(bpt)]·H2O (3) (H2bpda = biphenyl-2,4′-dicarboxylic acid, H3bpt = biphenyl-3,4′,5-tricarboxylic acid, bib = 1,4-bis(1-imidazolyl)benzene), have been prepared by urothermal synthesis. Complex 1 exhibits an unusual (4,6)-connected 3D network based on binuclear Co(II) clusters and Co2+ centers bridged by bpda2− and bib ligands. Complex 2, containing a novel pentanuclear Co(II) cluster, features a porous 3D MOF with a regular nanosized tunnel. Complex 3 contains an interesting tetranuclear Co(II) cluster and displays an amazing 3D porous MOF built from double-layered 2D [Co2(μ3-OH)(bpt)3]n networks pillared by two rows of bib spacers. In the title complexes, polycarboxylate acids serve to construct and stabilize the polynuclear Co(II) clusters, while bis(imidazole)s help to expand the dimensionality of MOFs. Complexes 2 and 3 show antiferromagnetic properties. Compound 3 with high surface area, high yield, high purity, and high chemical stability was used as a precursor to fabricate Co,N-codoped porous carbon materials by simple carbonization under an Ar atmosphere. The catalytic properties of the Co,N-codoped porous carbon material derived from complex 3 (denoted as CoNC-3) as an ORR electrocatalyst were studied. CoNC-3 displays superior electrocatalytic performances for the ORR. [ABSTRACT FROM AUTHOR]

A complexone analog chemosensor, H2L, bearing chelating bis(2-pyridylmethyl) amine and alizarin groups was synthesized via the Mannich reaction. H2L chromically responds to OH−, F−, CH3COO−, and H2PO4− in DMF, CH3CN, and acetone, but not in CH3OH or H2O. The addition of F− ions to H2L selectively induces a significant and visible color change in acetonitrile and shifts both methylene proton signals upfield. H2L also exhibits visible responses to Mg2+, Sr2+, Ba2+, Tb3+, Cu2+, Co2+, Ni2+, Zn2+, Mn2+, Cd2+, and Fe3+ in solution. AlCl3 can form an Al : L = 2 : 3 complex that not only changes the color of the DMF solution, but also significantly increases its fluorescence intensity. The limit of fluorescence turn-on detection for AlCl3 in DMF is 2.7 × 10−8 M, which is an order higher than those of other anthraquinone sensors reported in the literature. NMR spectroscopy shows that hydroxyl is not deprotonated upon interacting with Al3+, but will be partially deprotonated in the presence of Zn2+. Contrary to the complexone, the H2L–Ce(iii) complex does not react chromically to F−. However, the H2L–NiCl2 complex responds chromically to F−, with higher sensitivity (LOD = 1.3 × 10−6 M F− in acetonitrile) than free H2L. The spectral changes in the presence of F− are similar to that of OH−; however, the spectrum shifts slightly to a longer wavelength and is more sensitive to both H2L and the H2L–NiCl2 complex. Moreover, 4% or less H2O in the solvent essentially has no influence on the F− sensitivity; however, high water content significantly decreases the F− sensitivity. The spectral changes of the Zn2+, Cu2+, Fe3+, Ce3+, and Ni2+ complexes in the presence of different NaOH concentrations were also investigated. [ABSTRACT FROM AUTHOR]

Two-dimensional dichalcogenides (2D TMDCs) have emerged as a class of materials that may impact on future nanoelectronic and optoelectronic technologies. Design and discovery of new TMDC materials with reduced dimensionality is a significant and particularly interesting subject. Here, we proposed a new 2D layered structure material PdSe2 realized via high pressure by first-principles simulations. We found PdSe2 undertaking structural phase transitions under pressure, from the monoclinic phase with a space group of I2/a to two similar 2D layered structure phases with monoclinic C2/m and hexagonal P3̅m1 space groups at 4.5 GPa and 17.5 GPa, respectively. Interestingly, a new type of 2D monolayer material PdSe2 can be cleaved from the monoclinic C2/m bulk phase, suggested by the small exfoliation energy of 33.85 meV Å−2 (0.54 J m−2). More importantly, the new 2D PdSe2 monolayer is not only confirmed to be both dynamically and thermally stable, but also possesses a moderate band gap of about 1.10 eV and excellent visible-light optical absorption, suitable for photovoltaic applications. Furthermore, the effective masses and carrier mobility of the electrons and holes display extraordinary anisotropy along different transport directions, indicating that the monoclinic monolayer PdSe2 is a promising 2D material to facilitate effective electron/hole separation in high-performance nanoelectronic devices. [ABSTRACT FROM AUTHOR]

As one of the most promising techniques for harvesting solar energy, solar-powered generation of steam has great potential for application in sterilization, desalination, and other industrial processes. Although various methods of solar-powered steam generation have been reported, it remains a challenge to develop solar steam generators with durability, portability, and high photothermal performance for practical use. In this study, a novel device composed of reduced graphene oxide and silk fabric (RGO–silk-fabric) was demonstrated for highly efficient, solar-driven generation of steam. The unique fabric structure of silk and the broadband absorption by RGO allowed the RGO–silk-fabric to exhibit high light absorption in the wavelength range of 300 to 2500 nm. Benefitting from the capillary effect and superb air permeability, the RGO–silk-fabric system with a thermal insulator (polyethylene foam) exhibited remarkably high photothermal performances (an evaporation rate of 1.48 kg m−2 h−1) under one sun irradiation (1 kW m−2), even with minimal RGO content. Moreover, the RGO–silk-fabric showed great washability, flexibility, and excellent mechanical strength for low-cost, durable, and portable solar-steam applications. The simple fabrication process and scalability of the RGO–silk-fabric are expected to promote widespread application of the approach in water purification and other industrial processes. [ABSTRACT FROM AUTHOR]

Four new Ni(ii) coordination polymers, namely, [Ni(HL)(bpe)(H2O)2]n·nH2O (1), [Ni2(L)(bpe)(μ3-OH)(H2O)]n·3nH2O (2), [Ni(L)(bpe)(H2O)]n·[Ni0.5(bpe)0.5(H2O)2]n·nH2O (3) and [Ni(HL)(bpe)(H2O)]n·3nH2O (4) based on flexible ligands 5-(3-carboxybenzyloxy)-isophthalic acid (H3L) and 1,2-bis(4-pyridyl)ethane (bpe) have been successfully synthesized under different conditions. Compounds 1 and 4 present two-dimensional sql layer structures, while compound 2 exhibits a three-dimensional structure based on a tetranuclear Ni(ii) cluster with (3,8)-connected tfz-d topology, and compound 3 consists of a 2D sql anionic layer and 1D linear cationic chains, which are further entangled to give an interesting 2D + 1D → 3D poly-pseudorotaxane framework. To determine the relationship between these diverse structures and external synthetic influence factors, we systematically change the molar ratios of the reactants, solvent and pH and study their effects. Furthermore, the structural transformation from compound 4 to 3 has also been investigated. [ABSTRACT FROM AUTHOR]

First-principles calculations based on density functional theory were performed to investigate the electrochemical properties of K1−xVOPO4 in potassium-ion batteries (KIBs). The material showed multiple phase transitions during K ion extraction, which began with a two-phase transition (0 ≤x≤ 0.5), followed by a solid-solution transition (0.5 ＜ x≤ 0.625), another two-phase transition (0.625 ＜ x≤ 0.75), and finally a solid-solution transition (0.75 ＜ x≤ 1). These processes resulted in a small total unit cell volume variation of 6.6%, which was beneficial for the cycle stability of KIBs. Density of states and Bader charge analysis revealed that both V and O participated in the charge transfer process, where V acted as the redox center of KVOPO4 contributing to the K storage capacity, and O acted as a charge transfer medium between V and K. The stepwise increased repulsion between V cations caused three voltage plateaus for K1−xVOPO4. In addition, the one-dimensional diffusion pathway for K ions with low energy barriers of 0.214–0.491 eV ensured high K ion mobility resulting in superior high rate capability. [ABSTRACT FROM AUTHOR]

Two related three-membered series of nonlinear aminophenylferrocene and diphenylaminoferrocene complexes were prepared and characterized by 1H and 13C NMR spectroscopy. The first series consists of 4-(diphenylamino)phenylferrocene (TPA-Fc, 1a), its dimethoxy-substituted tetraphenylphenylenediamine derivative (M2TPPD-Fc, 1c), and the triphenylamine-bridged bis(ferrocenyl) complex (Fc-TPA-Fc, 1b). The second series involves bis(4-methoxyphenyl)aminoferrocene (M2DPA-Fc, 1d), 4-methoxyphenylaminoferrocene (MPA-Fc) with N-phenyl-appended terminal TPA (1e), and the corresponding bis(MPA-Fc) complex with bridging TPA (1f). The structure of complex 1d was further confirmed by single crystal X-ray diffraction. Combined investigations, based on anodic voltammetry, UV-vis-NIR spectroelectrochemistry and density functional theory (DFT) calculations, were conducted to illustrate the influence of the integration of multiple redox-active components on the sequential oxidation of these complexes. The first anodic steps in 1a–1f are localized preferentially on the ferrocenyl units, followed by oxidation of the TPA or TPPD moieties (absent in 1d). Irreversible oxidation of the ferrocene-appended strong donor DPA/MPA units in 1d–1f terminates the anodic series. The one-electron oxidation of the triphenylamine-bridged diferrocenyl (1b) and bis(phenylaminoferrocenyl) (1f) complexes triggers their facile redox disproportionation to dicationic bis(ferrocenium) products. [ABSTRACT FROM AUTHOR]

The enhanced photocatalytic mechanisms for the hybrid AlN/MX2 (MX2 = MoSe2, WS2, and WSe2) nanocomposites are systematically investigated by density-functional-theory calculations. Our theoretical calculations study the photocatalytic performance of AlN/MX2 nanocomposites with the inclusion of the spin–orbit coupling (SOC) effect. The results demonstrate that the band gaps of the AlN/MX2 bilayers vary from 1.72 to 1.93 eV, covering the main region of the visible light. All of the AlN–MX2 bilayers exhibit prominent visible and UV light response compared to their individual constituents, implying their potential applications as excellent light-absorbers. The AlN–MX2 heterobilayers are excellent photocatalysts for splitting water into hydrogen due to the perfect fit of band edge positions with respect to water reduction and oxidation potentials. Particularly, AlN–WS2 has type-II band alignment. Besides, the applied small biaxial tensile strain can not only effectively tune the band edge positions, but can also trigger an indirect–direct band gap transition in AlN–MX2 bilayers maintaining the excellent optical properties. Therefore, the strained AlN–MX2 bilayers are expected to be more promising candidates for photocatalysis. Overall, our theoretical predictions point toward the prospective future of novel AlN–MX2 heterostructures for photocatalysis. [ABSTRACT FROM AUTHOR]

A Rh/Ni-catalyzed cascade sequence of allylamine isomerization and hydrophosphonylation to synthesize α-aminophosphonates has been disclosed. The reaction, which not only allows the generation of widespread valuable α-aminophosphonates under simple systems and mild conditions, but also enriches the process of olefin isomerization–addition both in catalytic systems and various reaction types. [ABSTRACT FROM AUTHOR]

Six novel Co(ii) coordination polymers, namely, [Co10L6(OH)2(H2O)9]·10.5H2O (1), [Co3L2(3-abpt)2]·4H2O (2), [Co3L2(4-azpy)2(H2O)2(EtOH)] (3), [Co3L2(4,4′-bipy)2(H2O)2(MeCN)] (4), [Co3L2(4,4′-bipy)2] (5), and [Co5L2(OH)2(ina)2(H2O)2] (6) (H3L = 2,2′-phosphinico-dibenzoic acid, 3-abpt = 4-amino-3,5-bis(3-pyridyl)-1,2,4-triazole, 4-azpy = 4,4′-azobispyridine, 4,4′-bipy = 4,4′-bipyridine, Hina = isonicotinic acid), have been hydrothermally synthesized and their magnetic properties have been characterized. The L3− anion displays six types of coordination modes in the compounds. Compound 1 exhibits a novel 1D ladder-like structure, which consists of non-centrosymmetric Co10 units. Compounds 2–4 comprise 2D networks assembled from Co3L2 chains and N-heterocyclic linkers. Compound 5 comprises a 3D framework built from six neighboring parallel Co3L2 ladders bridged by 4,4′-bipy linkers. Compound 6 features a 3D framework that exhibits pcu topology with the Schläfli symbol of (412·63) using a pentanuclear [Co5(OH)2]8+ cluster as the node. Variable-temperature magnetic susceptibility studies indicate that the six coordination polymers exhibit remarkable magnetic behavior such as spin-canted antiferromagnetism and spin glass, which were found to coexist in compound 6. [ABSTRACT FROM AUTHOR]

The growth patterns and electronic structures of Aun clusters (n = 1–16) supported on the monoclinic ZrO2(111) surface were investigated using a DFT+U approach. We found that the supported Aun clusters prefer quasi-planar structures and lay flat on the ZrO2 surface. This result agrees well with the experimental results. Both orbital overlap and dispersion interactions contribute to the interaction between the Aun cluster and the ZrO2 surface. Electrons were transferred from the ZrO2 surface to the Aun cluster. Small energy gaps between unoccupied states in the Aun clusters and occupied states in the ZrO2 surface were found, especially for the supported Aun clusters with odd n, which may indicate that more electrons are excited from the ZrO2 surface to the Aun cluster even under visible-light irradiation. In other words, the ZrO2 support may be involved in the photocatalytic process when Aun/ZrO2 is used as a photocatalyst. [ABSTRACT FROM AUTHOR]

A series of ruthenium(ii) complexes [{RuCl(CO)(PMe3)3(–CH=CH–)}nX], 1a–1c (1a: n = 3, X = 3,3′′-dimethyl-2,2′:3′,2′′-terthiophene; 1b: n = 2, X = 2,2′-bithiophene; 1c: n = 2, X = 2,3-bis(3-methylthiophen-2-yl)benzothiophene) and [{Cp*(dppe)2Ru(–C≡C–)}3X], 1d (X = 3,3′′-dimethyl-2,2′:3′,2′′-terthiophene), were prepared and characterized by 1H, 13C and 31P NMR. Their redox, spectroscopic and bonding properties were studied with a range of spectro-electrochemical methods in combination with density functional theory calculations. The first two anodic steps observed for 1a and 1d are largely localized on the lateral frameworks of the molecular triangle, the direct conjugation between them being precluded due to the photostable open form of the dithienyl ethene moiety. The third anodic step is then mainly localized on the centerpiece of the triangular structure, affecting both bithiophene laterals. The experimental IR and UV-vis-NIR spectroelectrochemical data and, largely, also DFT calculations account for this explanation, being further supported by direct comparison with the anodic behavior of reference diruthenium complexes 1b and 1c. [ABSTRACT FROM AUTHOR]

A homochiral three-dimensional framework material, [Cu7(4-bpt)6(CN)(H2O)] (1) (4-bpt = 3,5-bis(4-pyridyl)-1,2,4-triazole), has been successfully synthesized by solvothermal reaction, which is generated through an unusual spontaneous asymmetrical crystallization from achiral precursors, and its photocatalytic properties in degradation of organic dyes are also investigated. [ABSTRACT FROM AUTHOR]

The first Cu-catalyzed cascade sp3 C–H bond oxidative functionalization of the 2-ethylazaarenes has been developed. The two different sp3 C–H bonds in 2-ethylazaarenes are selectively oxidized and four new types of bonds (C=O, C=N, C–C, C–O) are constructed in one operation. Starting from the simple substrates and cheap nitro source, this reaction provides an efficient approach to produce new kinds of isoxazolines. [ABSTRACT FROM AUTHOR]

By using the K2PdCl4/K2Pt(CN)4 cyanogel with a three-dimensional (3D) backbone structure as a reaction precursor, corallite-like Pt-Pd alloy nanostructures (Pt-Pd CANs) are facilely obtained by a simple NaBH4 reduction method; these exhibit superior electrocatalytic activity and stability for the ethanol oxidation reaction (EOR). [ABSTRACT FROM AUTHOR]

The hydrothermal reaction of silver nitrate and 2,2'-phosphinico-dibenzoic acid (H3L) with different metal to ligand ratios under hydrothermal conditions yielded two unusual complexes with the formulae of [Ag(H2L)]n (1) and [Ag3(L)]n (2). Both complexes were well characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopic and fluorescence studies. Complex 1 crystallizes in a centrosymmetric Pbcn space group and presents a two-dimensional (2D) layer structure through silver(I)-aromatic interaction, whereas complex 2 adopts a noncentrosymmetric Iba2 space group, in which the different coordination modes of the four groups around the phosphorus atom in the L3-ligand occurs. Both complexes display green emissions, assigned as the ligand-to-metal charge-transfer character. [ABSTRACT FROM AUTHOR]

The electronic structure and conductance of substitutionally edge-doped zigzag silicene nanoribbons (ZSiNRs) are investigated using the nonequilibrium Green's function method combined with the density functional theory. Two-probe systems of ZSiNRs in both ferromagnetic and antiferromagnetic states are considered. Doping effects of elements from groups III and V, in a parallel or antiparallel magnetic configuration of the two electrodes, are discussed. By switching on and off the external magnetic field, we may convert the metallic ferromagnetic ZSiNRs into insulating antiferromagnetic ZSiNRs. In the ferromagnetic state, even- or odd-width ZSiNRs exhibit a drastically different magnetoresistance. In an odd-width edge-doped ZSiNR a large magnetoresistance occurs compared to that in a pristine ZSiNR. The situation is reversed in even-width ZSiNRs. These phenomena result from the drastic change in the conductance in the antiparallel configuration. [ABSTRACT FROM AUTHOR]

Seven coordination polymers, namely [Mn(4-cptpy)2]n (1), [Co(4-cptpy)2]n (2), [Mn3(4-cptpy)6(H2O)]n. 2nH2O (3), [Co(4-cptpy)(HCOO)(H2O)]n'nDMF (4), [Zn2(4-Hcptpy)2Cl4]n.2nC2H5OH.nH2O (5), [Co4- (3-cptpy)4(HCOO)4(H2O)2]n (6), and [Mn(3-cptpy)2]n (7) (4-Hcptpy = 4-(4-carboxyphenyl)-4,2':6',4"-terpyridine; 3-Hcptpy = 4-(4-carboxyphenyl)-3,2':6',3"-terpyridine), have been synthesized under hydro- (solvo)thermal conditions and structurally characterized. A general solvothermal method is proposed for preparing carboxylate complexes in DMF solution without any basic additive. 1 and 2 possess isostructural 3D metal-organic frameworks containing nanosized cavities. 3 is a beautiful 2D coordination polymer assembled by flower-like Mn3(4-cptpy)6(H2O) subunits. 4 and 6 both display 2D polymeric networks constructed from 4/3-cptpy- ligands, in which the formate ligands originate from the hydrolysis of DMF. 5 is a 1D 21 helical chain polymer. 7 shows a 2D network with a (3.6) two-nodal kgd topology. 4/3-Hcptpy ligands display seven types of coordination modes. The zinc complex 5 emits strong violet luminescence. 1 and 2 are both thermally stable below 440 °C and exhibit antiferromagnetic interactions. [ABSTRACT FROM AUTHOR]

Solvothermal syntheses afforded two new MOFs {[Zn2(L1)(btmbb)(H2O)4]·2H2O}n (1) and [Zn2(L1)(btmbb)2]n (2) [5,5′-(1,4-phenylenebis(methylene))bis(oxy)diisophthalic acid (H4L1), and 4,4′-bis((1H-1,2,4-triazol-1-yl)methyl)biphenyl (btmbb)]. Single crystal X-ray analyses reveal that compound 1 shows an example of a 2D non-interpenetrating network, while compound 2 is a 2D polythreading interpenetrating structure, in which two layered networks interpenetrate in a (2D/2D) parallel fashion. The different conformation of the flexible ligand might be the main factor resulting in these non-interpenetrated/interpenetrated structures. The powder X-ray diffraction, thermal stabilities, and the photoluminescence of 1–2 have also been investigated. [ABSTRACT FROM AUTHOR]

A 2D tri-layer compound {[Co8(tbip)6(H2O)9(OH)4]·12(H2O)}n(1) (H2tbip = 5-tert-butyl isophthalic acid) consisting of novel heptacobaltate clusters and single cobalt centers bridged by tbip2−ligands has been hydrothermally synthesized. The complex represents a rare example of a homometallic coordination polymer built up from both heptanuclear metal clusters and single metal centers simultaneously. The magnetic investigation reveals that the complex exhibits the overall predominance of antiferromagnetic coupling between magnetic centers. [ABSTRACT FROM AUTHOR]

Three inorganic–organic compounds based on [MoxOy]n−chains, [Ag4(3-pttz)2Mo3O10] (1) (3-pttz = 5-(3-pyridyl) tetrazolate), [Ag4(2-pttz)2Mo4O13] (2) (2-pttz = 5-(2-pyridyl) tetrazolate), and [Ag4(pzttz)2Mo4O13] (3) (pzttz = 5-(pyrazinyl) tetrazolate), have been self-assembled, accompanied by in situformation processes of the 5-substituted tetrazolate ligands under hydrothermal condition. Compound 1features a 3D framework composed of [Mo3O10]2−chains cross-linked by [Ag4(3-pttz)2]2+belts. Compounds 2and 3reveal the 3D structures based on [Mo4O13]2−chains pillared by silver tetrazolate polymeric chains. The three title compounds represent the first three examples that the tetrazolate ligands are introduced into the backbones of the [MoxOy]n−anion chains. [ABSTRACT FROM AUTHOR]

Five novel hybrid compounds, [Mo8O26Cu2(4-abpt)2]n·4nH2O (1), (4-H2abpt)2[Mo8O26] (2), [Mo8O26Cu2(3-abpt)2(H2O)2]n(3), [MoO4Cu(3-abpt)(H2O)]n(4), and [Mo6O19Co(3-abpt)2]n·4nH2O (5) were prepared by reacting MoO3/(NH4)6Mo7O24with 4-amino-3,5-bis(3/4-pyridyl)-1,2,4-triazole (3/4-abpt) and corresponding metal salts. Compound 1is a 2D coordination polymer containing extended γ-[Mo8O26]4−and [Cu2(4-abpt)2]4+ribbons. Compound 2is a supramolecular hybrid aggregate composed of H-bond linking β-[Mo8O26]4−and 4-H2abpt2+. Compound 3exhibits a 2D rectangular network constructed by isolated β-[Mo8O26]4−clusters and [Cu2(3-abpt)2]4+. In compound 4, each MoO42−anion links two Cu(ii) ions to form a S-type [CuMoO4]nchain, which is further linked by bidentate 3-abpt to form a 2D wave-like network. In complex 5, unprecedented cyclic [Mo6O19]2−cluster links two neighbouring hexamolybdates and two Co(ii) ions to form a 2D [CoMo6O19]nnetwork, which is further pillared by tetradentate 3-abpt to generate a 3D metal–organic framework. These compounds are thermally stable under 250 °C. The composites of the final residues were analyzed by PXRD. [ABSTRACT FROM AUTHOR]

Biodegradable copolymers with molecule inclusion ability was prepared by introduction of β-cyclodextrin into poly(aspartic acid) matrices. The ibuprofen loading and dissolution properties of poly(aspartic acid)–β-cyclodextrin were investigated. [ABSTRACT FROM AUTHOR]

A low cost and environmentally benign process for tetrabutyl titanate-controlled ring-opening polymerization of -caprolactone at ambient temperature of 10–40 °C is introduced affording poly(-caprolactone) with pre-designed molecular weights and narrow molecular weight distribution. [ABSTRACT FROM AUTHOR]

Eu 2+ was used to substitute Ca in the orthorhombic KCoO 2 -type layered CaTiN 2 to form a Ca 1- x Eu x TiN 2 solid solution, which showed a limited substitution around x = 0.35 with the tetragonality enhanced but the orthorhombic symmetry retained and inaccessibility for the end member EuTiN 2 . This was in contrast with the full solid solution Ca 1- x Sr x TiN 2 , which realized a structural transition from orthorhombic to tetragonal at x = 0.5, even though Eu 2+ and Sr 2+ ions have similar sizes. The Eu substitution for Ca reduced the dielectric permittivity of CaTiN 2 owing to the reduced structural distortion arising from the enhanced tetragonality with the substitution. First-principle theoretical calculations on the total energies and formation energies considering the 4f electrons of Eu ions and the related magnetism were performed to understand the structural stability of the hypothetical EuTiN 2 . Compared with CaTiN 2 and SrTiN 2 , EuTiN 2 has much higher formation energies, making it inaccessible at high temperature. The evolutions of the experimentally observed and calculated lattice parameters of the Ca 1- x Eu x TiN 2 solid solution showed a preference for the orthorhombic phase over the tetragonal phase for the hypothetical EuTiN 2 , revealing a different coordination chemistry of Eu 2+ -N to Eu 2+ -O through the comparison of the structural variations of ATiN 2 and ATiO 3 (A = Ca, Sr, Eu).

Due to their unique structure, abundant properties and potential applications, low-dimensional materials with covalently bonded building blocks through van der Waals (vdW) interactions have sparked widespread interest. Recently, the bulk phase NbS 4 consisting of one-dimensional (1D) chains has been synthesized successfully, adding a new member to the group V metallic polychalcogenide family. In the present study, based on density functional theory calculations, we obtained a better understanding of the stability, mechanical properties, electronic structures, transport properties and optical performances of the bulk phase NbS 4 . Furthermore, the possibility of exfoliating 1D single-chain nanowires from the bulk phase was uncovered. Both bulk phase and 1D nanowires show dynamic, thermal, and mechanical stabilities. The bulk phase possesses an indirect band gap of 1.39 eV with high anisotropic carrier mobilities of 471.814 cm 2 s -1 v -1 for electrons (along the b axis direction) and 546.92 cm 2 s -1 v -1 for holes (along the a axis direction). The single-chain nanowire exhibits remarkable flexibility and can resist 24% tensile strain along the chain direction. The decreased dimension from the bulk phase to the individual 1D chain not only makes the band gap increase to 1.81 eV but also results in an indirect-to-direct band gap transition, indicating a strong quantum confinement effect. The 1D single-chain nanowire also shows high carrier mobilities of 111.91 cm 2 s -1 v -1 for electrons and 316.63 cm 2 s -1 v -1 for holes along the chain direction. In addition, both bulk phase and 1D nanowire display excellent visible light absorption performance along the chain direction and the absorption coefficients reach the order of 10 6 and 10 5 cm -1 . These promising properties render quasi 1D NbS 4 as candidate materials for nanoscale applications in high-performance optoelectronic and nanoelectronic devices. The predicted unconventional properties of NbS 4 not only provide a meaningful complement to the fascinating quasi 1D material family, but also will attract extensive interest from a wide audience to explore unanticipated properties and design new nanoscale devices based on NbS 4 .