An analytical model to predict diffusion induced intermetallic compounds growth in Cu-Sn-Cu sandwich structures

A mass diffusion model is developed to describe the growth kinetics of Cu_6Sn_5 intermetallic compounds(IMC) in the Cu-Sn-Cu sandwich structure. The proposed model is based on the local interfacial mass conversation law where interfacial Cu/Sn reactions and atomic diffusion are considered. Theoretical analysis shows that the IMC thickness growth is proportional to the square root of the product of the diffusion coefficient and time. The proposed model can explain the polarity effect of electromigration on kinetics of IMC growth where all the parameters have clear physical meaning. The theoretical predictions are compared with experimental results and show reasonable accuracy.     

Tuning the Reactivities of the Heteronuclear [AlnV3−nO7−n]+ (n=1, 2) Cluster Oxides towards Methane by Varying the Composition of the Metal Centers

The thermal gas-phase reactions of [Al₂VO₅]⁺ and [AlV₂O₆]⁺ with methane have been explored by using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry complemented by high-level quantum chemical calculations. Both cluster ions chemisorbed methane as the major reaction channels at room temperature. [Al₂VO₅]⁺ could break only one C−H bond to liberate CH₃, whereas [AlV₂O₆]⁺ exhibited higher oxidizing ability such that it brings about the selective generation of formaldehyde. Mechanistic aspects are revealed and the crucial roles of the metal centers are discussed.     

Sulfonimidamides and Imidosulfuric Diamides: Compounds from an Underexplored Part of Biologically Relevant Chemical Space

Two novel solid reagents—1-sulfonimidoyl- and 1-sulfamimidoyl-3-methylimidazolium derivatives—for the synthesis of sulfonimidamides and imidosulfuric diamides, respectively, were developed. It is shown that these reagents are very effective in substitution reactions with various N- and O-nucleophiles; therefore, they significantly extend the accessibility to the chemical space covered by organosulfur(VI) compounds with S=N bonds. In addition, previously unknown imidosulfuric diamides with free imino nitrogen groups were prepared, and their physical and chemical properties were characterized (including molecular geometry, pK_a, Log P, microsomal stability, and reactivity towards typical electrophiles). Similar to other organosulfur(VI) derivatives with S=N bonds, these compounds can be considered as promising bioisosteres of amides, ureas, or sulfonamides.     

Divergent and Chemoselective Transformations of Thioamides with Designed Carbene Equivalents

The reactions of thioamides with ortho-nitro-substituted iodonium ylides proceeded under mild conditions to give enaminones or thiazoles, depending on the iodonium ylide used. This protocol allowed the use of protic solvents, including aqueous solutions, and therefore coupling reactions with complex molecules such as peptides or steroids were possible. A mild and efficient method for the synthesis of various iodonium ylides was established. DFT calculations suggested that the halogen bonding between a thioamide and iodonium ylide was important in this chemoselective coupling reaction. The potential use of enaminones conjugated with pharmaceuticals as prodrugs was also demonstrated.     

Heterotrimetallic Mixed-Valent Molecular Precursors Containing Periodic Table Neighbors: Assignment of Metal Positions and Oxidation States

A known trinuclear structure was used to design the heterobimetallic mixed-valent, mixed-ligand molecule [Co^II(hfac)₃−Na−Co^III(acac)₃] ( 1 ). This was used as a template structure to develop heterotrimetallic molecules [Co^II(hfac)₃−Na−Fe^III(acac)₃] ( 2 ) and [Ni^II(hfac)₃−Na−Co^III(acac)₃] ( 3 ) via isovalent site-specific substitution at either of the cobalt positions. Diffraction methods, synchrotron resonant diffraction, and multiple-wavelength anomalous diffraction were applied beyond simple structural investigation to provide an unambiguous assignment of the positions and oxidation states for the periodic table neighbors in the heterometallic assemblies. Molecules of 2 and 3 are true heterotrimetallic rather than a statistical mixture of two heterobimetallic counterparts. Trinuclear platform 1 exhibits flexibility in accommodating a variety of di- and trivalent metals, which can be further utilized in the design of molecular precursors for the NaMM′O₄ functional oxide materials.     

Ultrasound-assisted nanoscaled supramolecular coordination polymer as an efficient recyclable catalyst for photocatalytic degradation of dye pollutants

An ultrasound-assisted nanoscaled supramolecular coordination polymer (nanosized 1′ ) has been synthesized using a self-assembly reaction of K₃[Cu (CN)₄] and hexamethylenetetramine in the presence of Me₃SnCl under ambient conditions. Nanosized 1′ was examined using elemental analysis, Fourier transform–infrared, transmission electron microscopy, scanning electron microscopy and X-ray powder diffractions. It was structurally compared with the single crystal supramolecular coordination polymer ^∞₃[Cu₆(CN)₇(C₆H₁₂N₄)₂(OH₃)]; SCP 1. The photocatalytic activities of nanosized 1′ and SCP 1 toward different hazardous organic dyes were determined under ambient, UV-light irradiation and ultrasonic conditions. SCP 1 and nanosized 1′ as heterogeneous nanoparticles catalysts exhibited high catalytic activity for degradation of Congo Red, Methyl Violet 2B and Methylene Blue dyes. The effects of operational parameters on catalytic degradation process, identification of the degradation products and recycling of the catalyst were also investigated. SCP 1 and nanosized 1′ are recyclable heterogeneous catalysts and can be reused with efficient activities. The mechanism of degradation using different scavenger techniques iss proposed and discussed. The catalytic oxidation process is mainly caused by ^•OH radicals.     

An unprecedented transformation mode in aluminium oxazoline-amido-phenolate complexes

This paper describes the effect of solvent-induced synthetic routes of aluminium pendant oxazoline-amido-phenolate complexes. Treatment of ligand precursor L with AlMe₃ in a 1:1 ratio in diethyl ether yielded the four-coordinated complex (LAlMe)₂. Reaction of ligand precursor L with AlMe₃ in a 1:2 ratio in hexane generated the four-coordinated complex L(AlMe₂)₂. A novel transformation mode occurred from L(AlMe₂)₂ to (LAlMe)₂ when using diethyl ether or tetrahydrofuran as solvent. A density functional theory computational study also supports a plausible mechanism. All results were supported by spectroscopic data and in agreement with single-crystal X-ray diffraction structural analysis.     

Theoretical investigation into coordination and selectivity of uranyl-unilateral benzotriazole salophens (X = O/S) for R/S-triadimefons

The design of new uranyl-ligands (uranyl-Ls) is of great significance for the separation and utilization of uranium. In this paper, the triazole group was introduced into uranyl-salophen (uranyl-S) to form new asymmetric uranyl-unilateral benzotriazole salophen (uranyl-UBS); we further replaced two oxygen atoms of uranyl-UBS with two sulfur atoms to generate uranyl-unilateral benzotriazole thio-salophen (uranyl-UBTS) as a new receptor. Then, we comprehensively explored coordination models of uranyl-UBS and uranyl-UBTS with R/S-triadimefons (R/S-TDFs) enantiomers as the guests using density functional theory calculations at the B3LYP//RECP/6-311G** level; we then investigated enantioselectivity recognition of the new receptors to the guests R/S-TDFs. The results indicated that the uranium atoms of the receptors uranyl-S, uranyl-UBS and uranyl-UBTS could coordinate with the carbonyl oxygens in guests R/S-TDFs to form complexes of guest-receptors R/S-TDFs-uranyl-Ls that exhibited two stable V-shaped structures with quite different properties. It was found that the coordination ability to the guests R/S-TDFs is uranyl-UBTS > uranyl-UBS > uranyl-S, while the enantioselectivity for the guests is uranyl-UBTS > uranyl-S > uranyl-UBS and, when the receptor is the same, R-TDF has stronger coordination ability than S-TDF. These results provide information and theoretical supports for the experiments of asymmetric uranyl-UBS with R/S-TDFs, and produce a reference for further exploring the coordination characteristics of asymmetric uranyl-salophen with the triazole derivatives.     

Structural-Deformation-Energy-Modulation Strategy in a Soft Porous Coordination Polymer with an Interpenetrated Framework

To achieve unique molecular-recognition patterns, a rational control of the flexibility of porous coordination polymers (PCPs) is highly sought, but it remains elusive. From a thermodynamic perspective, the competitive relationship between the structural deformation energy (E_def) of soft PCPs and the guest interaction is key for selective a guest-triggered structural-transformation behavior. Therefore, it is vital to investigate and control E_def to regulate this competition for flexibility control. Driven by these theoretical insights, we demonstrate an E_def-modulation strategy via encoding inter-framework hydrogen bonds into a soft PCP with an interpenetrated structure. As a proof of this concept, the enhanced E_def of PCP enables a selective gate-opening behavior toward CHCl₃ over CH₂Cl₂ by changing the adsorption-energy landscape of the compounds. This study provides a new direction for the design of functional soft porous materials.     

Face-Directed Assembly of Molecular Cubes: In Situ Substitution of a Predetermined Concave Cluster

Systematic design and self-assembly of metal–organic polyhedra with predictable configurations has been a long-standing challenge in crystal engineering. Herein a concave polyoxovanadate cluster, [V₆O₆(OCH₃)₉(SO₄)₄]⁵⁻, which can be generated in situ under specific reaction conditions, is reported. Based on this cluster, a potential trivalent molecular building block, [V₆O₆(OCH₃)₉(SO₄)(CO₂)₃]²⁻, can be obtained by the bridging-ligand-substitution strategy and it possesses appropriate angle information for the design of molecular cubes. Utilizing the face-directed assembly of the trivalent molecular building block and a diverse set of tetratopic carboxylate linkers, a series of metal–organic cubes ( VMOC-1 – VMOC-5 ) with the same topology but different functionalities and dimensions were designed and constructed. An inclusion study using VMOC-3 shows that they are potential molecular receptors for selective capture of size-matching polycyclic aromatic hydrocarbon guest molecules.