Search

The diruthenium-based linear mixed valence complex trans -[Ru 2 (ap) 4 -NC-Ru(DMAP) 4 -CN-Ru 2 (ap) 4 ][PF 6 ] 2 (12+[PF6]2) (ap = 2-anilinopyridinate, DMAP = 4-dimethylaminopyridine) and its two-electron oxidation product 14+[PF6]4 have been synthesized and fully characterized. The investigation reveals that complex 12+ displays a single MMCT transition, whereas complex 14+ has three identified MMCT transitions (MMCT-1, MMCT-2 and MMCT-3) upon oxidation. Interestingly, MMCT-2 in complex 14+ might result from the transition from the Ru III -NC-Ru II -CN-Ru III component, which is composed of the central Ru II and its two neighboring Ru III atoms from the cluster RuVI2 units, to both the terminal Ru III atoms of the same cluster RuVI2 units, which is supported by the TDDFT calculations.

High-index faceted Pt nanoparticles with excellent electrocatalytic performances are promising to efficiently accelerate the oxygen reduction reactions in fuel cells. By adopting the hybrid grand canonical Monte Carlo reactive molecular dynamics (GCMC/RMD) simulations, we examined the oxygen adsorption on three 24-facet nanoparticles respectively enclosed by {310}, {311}, and {331} high-index facets. The site-dependent adsorption energies on each open-structure surface are calculated. Meanwhile, the adsorption ratios under various pressures and temperatures are presented. It is revealed that the adsorption capacity of these high-index faceted nanoparticles is considerably higher than that of the ones terminated by low-index facets. Moreover, oxygen adsorption exerts a significant impact on their thermodynamic behaviors.

To investigate MMCT excited states of MV complexes, two symmetrical tetranuclear cyanido-bridged localized MV complexes RuIICNRuIII,III2NCRuII have been designed and synthesized. The ultrafast time-resolved transient absorption (TA) spectroscopy experiment reveals that the MMCT rate of 1 and 2 is 0.18 × 1014 s-1 (τ = 5.7 × 10-14 s) and 0.29 × 1013 s-1 (τ = 3.46 × 10-13 s), respectively, which suggests that the MMCT rate or the lifetime of the MMCT excited state may be controlled by a slight change of the substituent group on the metal center.

A trinuclear cyanide-bridged luminescent compound, trans-RuII(DMAP)4(CN)2[(PY5Me2)Mn]2[PF6]4 (1-R), and its oxidation product, ferromagnetic trans-RuIII(DMAP)4(CN)2[(PY5Me2)Mn]2-[PF6]5 (1-O), were synthesized and fully characterized. This is the first example of a molecular material showing a redox-controlled transformation between fluorescence and ferromagnetism.

This report describes a new method for three-component difluoroalkylation and trifluoromethylthiolation/trifluoromethylselenolation of π-bonds via air-stable SCF 3 and SeCF 3 reagents as free-radical initiators of ethyl iododifluoroacetate. β-Proton elimination can be overcome effectively in this reaction system, and a broad substrate scope, including alkenes and alkynes, makes this approach practical and attractive.

A traditional doping technique plays an important role in the band structure engineering of two-dimensional nanostructures. Since electron interaction is changed by doping, the optical and electrochemical properties could also be significantly tuned. In this study, density functional theory calculations have been employed to explore the structural stability, and electronic and optical properties of B-doped phosphorene. The results show that all B-doped phosphorenes are stable with a relatively low binding energy. Of particular interest is that these B-doped systems exhibit an indirect band gap, which is distinct from the direct one of pure phosphorene. Despite the different concentrations and configurations of B dopants, such indirect band gaps are robust. The screened hybrid density functional HSE06 predicts that the band gap of B-doped phosphorene is slightly smaller than that of pure phosphorene. Spatial charge distributions at the valence band maximum (VBM) and the conduction band minimum (CBM) are analyzed to understand the features of an indirect band gap. By comparison with pure phosphorene, B-doped phosphorenes exhibit strong anisotropy and intensity of optical absorption. Moreover, B dopants could enhance the stability of Li adsorption on phosphorene with less sacrifice of the Li diffusion rate. Our results suggest that B-doping is an effective way of tuning the band gap, enhancing the intensity of optical absorption and improving the performances of Li adsorption, which could promote potential applications in novel optical devices and lithium-ion batteries.

SmI 2 -mediated reductive cyclization of β-arylthio ketones to generate thiochroman derivatives is not a generally observed process and the reported examples are limited to geminal disubstitution in the substrates. The results of the current study show that the cyclization also occurs when other substitution patterns are present, affording a general approach to dihydrothiochroman-ols in good yields and high degrees of diastereoselectivity. Besides, the halogen substitution on β-aryl is tolerated in most cases here although reductive dehalogenation has been reported to predominate in the reductive cyclization process. Dihydrothiochroman-4-ols were readily oxidized to thiochroman-4-ols in almost quantitative yields.

Bimetallic nanoparticles comprising noble metal and non-noble metal have attracted intense interest over the past few decades due to their low cost and significantly enhanced catalytic performances. In this article, we have explored the atomic structure and thermal stability of Pt-Fe alloy and core-shell nanoparticles by molecular dynamics simulations. In Fe-core/Pt-shell nanoparticles, Fe with three different structures, i.e., body-centered cubic (bcc), face-centered cubic (fcc), and amorphous phases, has been considered. Our results show that Pt-Fe alloy is the most stable configuration among the four types of bimetallic nanoparticles. It has been discovered that the amorphous Fe cannot stably exist in the core and preferentially transforms into the fcc phase. The phase transition from bcc to hexagonal close packed (hcp) has also been observed in bcc-Fe-core/Pt-shell nanoparticles. In contrast, Fe with the fcc structure is the most preferred as the core component. These findings are helpful for understanding the structure-property relationships of Pt-Fe bimetallic nanoparticles, and are also of significance to the synthesis and application of noble metal based nanoparticle catalysts.

Atomic-scale understanding of structures and thermodynamic stability of core-shell nanoparticles is important for both their synthesis and application. In this study, we systematically investigated the structural stability and thermodynamic evolution of core-shell structured Pd-Ni nanoparticles by molecular dynamics simulations. It has been revealed that dislocations and stacking faults occur in the shell and their amounts are strongly dependent on the core/shell ratio. The presence of these defects lowers the structural and thermal stability of these nanoparticles, resulting in even lower melting points than both Pd and Ni monometallic nanoparticles. Furthermore, different melting behaviors have been disclosed in Pd-core/Ni-shell and Ni-core/Pd-shell nanoparticles. These diverse behaviors cause different relationships between the melting temperature and the amount of stacking faults. Our results display direct evidence for the tunable stability of bimetallic nanoparticles. This study provides a fundamental perspective on core-shell structured nanoparticles and has important implications for further tailoring their structural and thermodynamic stability by core/shell ratio or composition controlling.

ZnO/GaN alloys have exceptional photocatalytic applications owing to their suitable band gaps corresponding to the range of visible light wavelength and thus have attracted extensive attention over the past few years. In this study, the structural stabilities and electronic properties of core/shell, biaxial, and super-lattice ZnO/GaN heterostructured nanowires have been investigated by means of first-principles calculations based on the density functional theory. The effects of the nanowire size, the GaN ratio, and strain have been explored. It is found that all studied heterostructured nanowires are less stable than pure ZnO nanowires, exhibiting larger sized wires with better structural stabilities and inversely proportional relationship between structural stability and the GaN ratio. Electronic band structures imply that all heterostructured nanowires are semiconductors with the band gaps strongly depending on the GaN ratios as well as mechanical strain. Particularly, for the biaxial and the super-lattice nanowires, their band gaps decrease firstly and then increase with the increasing GaN ratios. Electronic contributions to the valence band maximum (VBM) and the conduction band minimum (CBM) are discussed for exploiting the potential photocatalytic applications.

Nanosized noble metallic particles enclosed by high-index facets exhibit superior catalytic activity because of their high density of low-coordinated step atoms at the surface, and thus have attracted growing interest over the past decade. In this article, we employed molecular dynamics simulations to investigate the thermodynamic evolution of tetrahexahedral Rh nanoparticles respectively covered by {210}, {310}, and {830} facets during the heating process. Our results reveal that the {210} faceted nanoparticle exhibits better thermal and shape stability than the {310} and {830} faceted ones. Meanwhile, because the {830} facet consists of {210} and {310} subfacets, the stability of the {830} faceted Rh nanoparticle is dominated by the {310} subfacet, which possesses a relatively poor stability. Furthermore, the shape transformation of these nanoparticles occurs much earlier than their melting. Further analyses indicate that surface atoms with higher coordination numbers display lower surface diffusivity, and are thus more helpful for stabilizing the particle shape. This study offers an atomistic understanding of the thermodynamic behaviors of high-index-faceted Rh nanoparticles.

A microscopic understanding of the thermal stability of metallic core-shell nanoparticles is of importance for their synthesis and ultimately application in catalysis. In this article, molecular dynamics simulations have been employed to investigate the thermodynamic evolution of Au-CuPt core-shell trimetallic nanoparticles with various Cu/Pt ratios during heating processes. Our results show that the thermodynamic stability of these nanoparticles is remarkably enhanced upon rising Pt compositions in the CuPt shell. The melting of all the nanoparticles initiates at surface and gradually spreads into the core. Due to the lattice mismatch among Au, Cu and Pt, stacking faults have been observed in the shell and their numbers are associated with the Cu/Pt ratios. With the increasing temperature, they have reduced continuously for the Cu-dominated shell while more stacking faults have been produced for the Pt-dominated shell because of the significantly different thermal expansion coefficients of the three metals. Beyond the overall melting, all nanoparticles transform into a trimetallic mixing alloy coated by an Au-dominated surface. This work provides a fundamental perspective on the thermodynamic behaviors of trimetallic, even multimetallic, nanoparticles at the atomistic level, indicating that controlling the alloy composition is an effective strategy to realize tunable thermal stability of metallic nanocatalysts.

Treatment of trans-(Ph-tpy)Ru(PPh(3))(CN)(2) (Ph-tpy = 4'-phenyl-2,2':6',2''-terpyridine, PPh(3) = triphenylphosphine) with 2 equiv of Cp(dppe)Fe(NCCH(3))Br (dppe = bis(diphenylphosphino)ethane) in the presence of NH(4)PF(6) produced a trinuclear cyanide-bridged complex, trans-[Cp(dppe)Fe(CN)(Ph-tpy)Ru(PPh(3))(CN)Fe(dppe)Cp][PF(6)](2) (1[PF(6)](2)). Its one-electron oxidation product (1[PF(6)](3)) and two-electron-oxidation product (1[PF(6)](4)) were obtained by oxidation with (Cp)(2)FePF(6) and AgPF(6), respectively. Firstly, the crystal structures of the cyanide-bridged complexes with three stable states were fully characterized. The reversible electrochemistry measurement of 1(2)(+) shows the presence of a long range intervalence interaction between the external iron centres. Both 1(3)(+) and 1(4)(+) were considered to be Class II mixed valence complexes according to the classification of Robin and Day. Magnetic analysis indicated the presence of a moderately strong antiferromagnetic coupling between the two remote Fe(III) ions across the Fe-NC-Ru-CN-Fe array in 1(4)(+). This proves that the Ru(II)-dicyano complex is a bridging ligand that can transmit electro- and magneto-communication.

A novel 3-D coordination polymer with trimeric copper (I) unit, [Cu(3)(CN)(IN)(2)](n)(IN = isonicotinate), was hydrothermally synthesized by the reaction of Cu(NO(3))(2).3H(2)O with isonicotinic and terephthalic acids. The structure was characterized to be a twofold interpenetrated 3-D coordination network polymer with two-coordinated copper(I). It has a powder SHG efficiency about that of KDP.