Search

Abstract Precise synthesis of polyoxometalates (POMs) is important for the fundamental understanding of the relationship between the structure and function of each building motif. However, it is a great challenge to realize the atomic-level tailoring of specific sites in POMs without altering the major framework. Herein, we report the case of Ce-mediated molecular tailoring on gigantic {Mo132}, which has a closed structural motif involving a never seen {Mo110} decamer. Such capped wheel {Mo132} undergoes a quasi-isomerism with known {Mo132} ball displaying different optical behaviors. Experiencing an ‘Inner-On-Outer’ binding process with the substituent of {Mo2} reactive sites in {Mo132}, the site-specific Ce ions drive the dissociation of {Mo2 *} clipping sites and finally give rise to a predictable half-closed product {Ce11Mo96}. By virtue of the tailor-made open cavity, the {Ce11Mo96} achieves high proton conduction, nearly two orders of magnitude than that of {Mo132}. This work offers a significant step toward the controllable assembly of POM clusters through a Ce-mediated molecular tailoring process for desirable properties.

Polyoxometalates (POMs) are known for their well-established catalytic properties, particularly in photocatalysis, and have made significant strides in achieving selective C(sp3)−H functionalization. However, due to the complexity of the POM structures, the reactivity and regioselectivity of POMs in organic conversions remain unclear. Here, the reactivity and regioselectivity of the C(sp3)–H trifluoromethylation of pyrrolidine via decatungstate anion/copper ([W10O32]4−/Cu) dual catalysis were theoretically investigated. Density functional theory (DFT) computations revealed that the β-regioselective activation of pyrrolidine occurs more readily than does α-regioselective activation; this is due to the reduction in activity of the ortho α-C–H bond by protonation. Furthermore, the reactivity of hydrogen atom transfer (HAT) catalysts for C(sp3)–H bond activation follows the order [W10O32]4− > amine radical cation > fluorescein. The outstanding reactivity of [W10O32]4− is attributable to its rigid structure and exposed active surface sites. We demonstrate a linear relationship between the steric volume of the protective group on pyrrolidine and the C–H bond selectivity catalyzed by [W10O32]4−. In other words, a larger steric volume of the protective group on pyrrolidine leads to easier attainment of a single Cβ–H bond activation product. We hope that this theoretical analysis will provide valuable guidance for obtaining high selectivity target products in experimental setups.

The synthesis of stable chiral porous organic cages and the study of their chiral self-sorting properties is challenging. Here, the authors report axially chiral porous aromatic cages with high stability and solvent-controlled chiral self-sorting.

Recently, non-fullerene-based organic solar cells (OSCs) have made great breakthroughs, and small structural differences can have dramatic impacts on the power conversion efficiency (PCE). We take ITIC and its isomers as examples to study their effects on the performance of OSCs. ITIC and NFBDT only differed in the side chain position, and they were used as models with the same donor molecule, PBDB-T, to investigate the main reasons for the difference in their performance in terms of theoretical methods. In this work, a detailed comparative analysis of the electronic structure, absorption spectra, open circuit voltage and interfacial parameters of the ITIC and NFBDT systems was performed mainly by combining the density functional theory/time-dependent density functional theory and molecular dynamics simulations. The results showed that the lowest excited state of the ITIC molecule possessed a larger ∆q and more hybrid FE/CT states, and PBDB-T/ITIC had more charge separation paths as well as a larger kCS and smaller kCR. The reason for the performance difference between PBDB-T/ITIC and PBDB-T/NFBDT was elucidated, suggesting that ITIC is a superior acceptor based on a slight modulation of the side chain and providing a guiding direction for the design of superior-performing small molecule acceptor materials.

Abstract Developing flexible electrodes with high active materials loading and excellent mechanical stability is of importance to flexible electronics, yet remains challenging. Herein, robust flexible electrodes with an encapsulated core‐multishell structure are developed via a spraying‐hydrothermal process. The multilayer electrode possesses an architecture of substrate/reduced graphene oxide (rGO)/bimetallic complex/rGO/bimetallic complex/rGO from the inside to the outside, where the cellulosic fibers serve as the substrate, namely, the core; and the multiple layers of rGO and bimetallic complex, are used as active materials, namely, the shells. The inner two rGO interlayers function as the cement that chemically bind to two adjacent layers, while the two outer rGO layers encapsulate the inside structure effectively protecting the electrode from materials detachment or electrolyte corrosion. The electrodes with a unique core‐multishell structure exhibit excellent cycle stability and exceptional temperature tolerance (−25 to 40 °C) for lithium and sodium storage. A combination of experimental and theoretical investigations are carried out to gain insights into the synergetic effects of cobalt‐molybdenum‐sulfide (CMS) materials (the bimetallic complex), which will provide guidance for future exploration of bimetallic sulfides. This strategy is further demonstrated in other substrates, showing general applicability and great potential in the development of flexible energy storage devices.

In the title compound, [Ni(C10H6NO3)2(H2O)4], the central NiII atom is located on an inversion center and coordinated in a slightly distorted octahedral geometry by two O atoms from two 2-oxo-1,2-dihydroquinoline-4-carboxylate ligands and four water molecules, all of which act as monodentate ligands. The crystal structure features an extensive network of intermolecular hydrogen-bonding interactions (O—H...O and N—H...O) and offset face-to-face π–π stacking interactions [centroid–centroid distances = 3.525 (3) and 3.281 (5) Å].

The external electric field has emerged as a powerful tool for building molecular switches with excellent properties. In this work, we investigate the impact of an external electric field on the transition between lithium salt and electride-like molecule conformations in Li@corannulene. Remarkably, the distance between the Li atom and the corannulene bottom displays a sharp increase under the influence of an external electric field strength of F-z = 110×10-4 a.u. As the external electric field strength increases, the Li atom brings about different directions of charge transfer (CT). The natural population analysis (NPA) charge and the molecular electrostatic potential (ESP) results show that the intermolecular CT occurs from the Li atom to the corannulene with the Fz ranging from 0 to 100 104 a.u. Interestingly, when the external electric field reaches Fz = 110×10-4 a.u., the CT is oriented from the corannulene to the Li atom. Moreover, electron localization function (ELF) basins are presented under an Fz of 110×10-4 a.u., which indicates that Li@corannulene exhibits electride-like (e-...[Li@corannulene]+ ) molecules and lithiation salt (Li+ [corannulene]) under an F-z of 0 to 100×10-4 a.u. Significantly, the differences in charge transfer also contribute to a significant improvement in hyperpolarizabilities (βtot) during the conformation transition from lithiation salt (Li+ [corannulene]) to electride-like (e-...[Li@corannulene]+ ) molecules. This study explores the potential of Li@corannulene as a promising second-order NLO material, and the external electric field provides an efficient strategy for designing and developing NLO switching devices. [ABSTRACT FROM AUTHOR]

The detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) is not only of great significance in the areas of biomedicine and neurochemistry but also helpful in disease diagnosis and pathology research. Due to their diverse structures, designability, and large specific surface areas, metal-organic frameworks (MOFs) have recently caught considerable attention in the electrochemical field. Herein, a family of heterometallic MOFs with amino modification, MIL-125(Ti-Al)-xNH2 (x = 0%, 25%, 50%, 75%, and 100%), were synthesized and employed as electrochemical sensors for the detection of AA, DA, and UA. Among them, MIL-125(Ti-Al)-75%NH2 exhibited the most promising electrochemical behavior with 40% doping of carbon black in 0.1 M PBS (pH = 7.10), which displayed individual detection performance with wide linear detection ranges (1.0-6.5 mM for AA, 5-100 μM for DA and 5-120 μM for UA) and low limits of detection (0.215 mM for AA, 0.086 μM for DA, and 0.876 μM for UA, S/N = 3). Furthermore, the as-prepared MIL-125(Ti-Al)-75%NH2/GCE provided a promising platform for future application in real sample analysis, owing to its excellent anti-interference performance and good stability. [ABSTRACT FROM AUTHOR]

Carbon nanorings have attracted substantial interest from synthetic chemists due to their unique topological structures and distinct physical properties. An intriguing p-conjugated double-nanoring structure, denoted as [8]CPP-[10]cyclacene, was constructed via the integration of [8]cycloparaphenylene ([8]CPP) into [10]cyclacene. Using the external electric field stimuli-responsiveness of [8]CPP-[10]cyclacene, directional charge transfer can be induced, resulting in the emergence of intriguing properties. The effects of the external electric field in three specific directions were explored, vertically in the [8]CPP unit (Fy), vertically in the [10]cyclacene unit (Fz), and horizontally along the double nanorings diameter (Fx). Interestingly, the external electric field vertically to the [10]cyclacene unit significantly enhanced the first hyperpolarizability (btot) compared to that vertically to the [8]CPP unit. Notably, [8]CPP-[10]cyclacene under Fx exhibited significantly larger the btot values (1.48 x 105 a.u.) than those of vertical Fy and Fz. This work opens up a wide range of nonlinear optics, making it a compelling area to explore in the field of carbon nanomaterials. [ABSTRACT FROM AUTHOR]

The geometrical structure, stability, the basis set effects, and the linear and nonlinear optical properties of neutral pie-conjugated [C.sub.4][H.sub.4]N. are determined. Conjugation and stability of the neutral [C.sub.4][H.sub.4]N. reduced after a rise in the spin multiplicity.

Two unprecedented self-penetrating networks containing the highest-stranded molecular braid and 9-fold meso helices were prepared by self-assembly of long V-shaped ligands and [d.sup.10] metal salts. The isolation of both the compounds confirms the aesthetic diversity of coordinative network chemistry and might provide new insights into the analysis and design of self-penetrating networks.

The tetra-(8-hydroxyquinolinato) boron complex (Bq) and 3,3',4,4'-benzophenone tetracarboxylic anion (BPTC) were intercalated into layered double hydroxides with an ion-exchange method. Elemental analyses, powder X-ray diffraction, FTIR spectra, and thermogravimetric analyses indicated that the hydrothermal treatment could improve the reaction process, purity and crystallinity of products.

The structures of silver(I) sulfonates incorporating neutral ligands are examined. The shows that the compound may be controlled by the secondary legands and the dimensionalities of the compound increase with the increase in coordination sites of the secondary legands.

The complexes of formulas Ln(pydc)(Hpydc) (Ln = Sm, Eu, Gd and H2pydc = pyridine-2,5-dicarboxylic acid), Ln(pydc)(bc)(H2O) (Ln = Sm, Gd and Hbc = benzenecarboxylic acid) are synthesized under hydrothermal conditions and characterized by elemental analysis, infrared (IR), TG analysis and single-crystal X-ray diffraction. The results show that the five three-dimensional nets are binodal with six- and three-connected nodes, the former of which exhibit a rutile-related topology that is unprecedented within coordination frames, and the latter two species display a distorted rutile topology.

Density functional theory was used to investigate the bonding character of arylimido molybdate derivatives. The investigation provides insight into polyanion-organoimido interactions.

Two tetra-nuclear YbIII-incorporated selenotungstate clusters, Keggin (C2H8N)6Na14[Yb4Se6W44O160(H2O)12]·40H2O (1) and Wells--Dawson (C2H8N)4Na14[Yb4Se6W45O159(OH)6(H2O)11]·38H2O (2), have been isolated through a pH-controlled assembly, which exhibit the first YbIII-containing polyoxotungstates with selenium heteroatoms. Their assemblies rely on the structure-directing effects of SeO32- anion templates to give rise to available Se-containing Keggin-/Wells--Dawson-type motifs. Both compounds were characterized by single-crystal X-ray diffraction, IR spectroscopy, power X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) as well as electrospray ionization mass spectrometry (ESI-MS). Furthermore, systematic magnetic studies revealed that 1 exhibits field-induced single-molecule magnetic behavior with a pre-exponential factor of τ0 = 6.60(7) x 10-8 s and a relaxation energy barrier of ΔE/kB = 39.44(2) K,while 2 only displays antiferromagnetic interactions between the ytterbium centers. [ABSTRACT FROM AUTHOR]

Support vector machines (SVMs), as a novel type of learning machine, has been very successful in pattern recognition and function estimation problems. In this paper we introduce least-squares (LS) SVMs to improve the calculation accuracy of density functional theory. As a demonstration, this combined quantum mechanical calculation with LS-SVM correction approach has been applied to evaluate the electronic excitation energies of 160 organic molecules. The newly introduced LS-SVM approach reduces the root-mean-square deviation of the calculated electronic excitation energies of 160 organic molecules from 0.32 to 0.11 eV for the B3LYP/6-31G(d) calculation. Thus, the LS-SVM correction on top of B3LYP/6-31G(d) is a better method to correct electronic excitation energies and can be used as the approximation of experimental results which are impossible to obtain experimentally. [ABSTRACT FROM AUTHOR]

An investigation of C36Xn (X=F,Cl,Br; n=2,4,6,12) formed from the initial C36 fullerene with D6h symmetry has been performed using the MP2 theory. Their equilibrium structures, reaction energies, strain energies, lowest unoccupied molecular orbital-highest occupied molecular orbital (LUMO-HOMO) gap energies, and aromaticities have been studied. The calculation results showed that those addition reaction were highly exothermic and C36Xn were more stable than C36. Moreover, from the view of thermodynamics it should be possible to detect C36X6. The LUMO-HOMO gap energies of C36Xn were higher than D6hC36 and the redox characteristics of C36Xn were weaker comparing to D6hC36. The analyses of π-orbital axis vector indicated that the chemical reactivity of C36 was the result of the high strain, and the nucleus independent chemical shifts research showed that the stabilities of the C36X6 were correlative with the conjugation effect. [ABSTRACT FROM AUTHOR]

The synthesis of protein-sized chiral [Fe.sub.168] cages with NbO-type topology is reported. The synthesis involved the introduction of L- and D-tartrate ligands into the [Fe.sup.3+]/formate/[Na.sup.+] systems that exhibited alcohol-guest sorption properties.

The simple one-step hydrothermal reaction of copper nitrate, benzentricarboxylate (BTC) and different Keggin polyoxometalates (POMs) are used to prepare a series of remarkable crystalline compounds [[[Cu.sub.2][(BTC).sub.4/3][([H.sub.2]O).sub.2]].sub.6][[H.sub.n]X[M.sub.12][O.sub.40]]*[([C.sub.4][H.sub.12]N).sub.2] (X = Si, Ge, P, As; M = W, Mo). The results have shown that the attributes of metal organic framework and well-dispersed level of POMs have allowed the enhancement of their catalytic properties.

The density functional theory (DFT) and ab initio HF method were employed to study the structural, electronic, and carrier transport properties of bathocuproine (BCP), which is typical hole/exciton-blocking material applied in organic light-emitting diodes (OLEDs). The results showed that the hole/exciton-blocking and electron-transport properties of BCP materials are attributed to significant roles of rigid planar structures, conjugate degrees, and substitute groups.

Six polyoxometalate (POM)-based hybrid materials are designed and prepared based on octamolybdate building blocks and copper-organic units at different pH values under hydrothermal conditions. The successful isolation of these species has provided clue for the supramolecular isomerism in POMs-based MOFs, which has helped in understanding the structure-property relationship of POMs-based MOFs.

Time-dependent density functional theory was employed to study the structural geometry, electronic spectra, and third-order nonlinear optical (NLO) properties of Fe[([[eta].sup.5]-[C.sub.55][X.sub.5]).sub.2] (X = CH, N, B). The results revealed that the short wavelength transitions are attributed to the [C.sub.50] moiety mixed charged transfer transitions of ferrocene itself and the long wavelength transitions are due to the unique charge transfer transition from ferrocene to [C.sub.50] moiety of this system.

The article discusses a new methodology, where in the catenation of the loop-containing 2D layers of rings with a 3D pcu skeleton is employed for the development of a new type of entangled framework. The obtained framework is shown to exhibit polycatenane, as well as polyrotaxane character because of the presence of nanosized polyoxoanions in it.

The flexible organic ligands 1,3-bis(1,2,4-triazol-1-yl)propane (btp), 1,4-bis(1,2,4-triazol-1yl)butane (btb) and 1,6-bis(1,2,4-triazol-1-yl)hexane (btx) are introduced into the Wells-Dawson polyoxometalates (POM) system, which has aimed at obtaining novel architectures of POM coordination polymers with a combination of flexibility and robustness. The structural analyses has shown that the length of flexible bis(triazole) ligands and metal ion coordination geometries have a synergic influence on the structures of this series.

Two unprecedented dinuclear tin compounds containing deprotonated [beta]-cyclodextrins are constructed by using different organotin and inorganotin precursors under solvothermal conditions. These compounds have displayed two dinuclear airscrew-like structures with different packing modes.

Quantum-chemical study is used for analyzing the electronic and optical properties of several platinum(II) dimers. These platinum dimers can be used as a new kind of third-order nonlinear optical material, which is due to their large-order polarizability value and high transparency.

The synthesis and structural studies of two copper compounds are described. The complexes exhibit a new type of supramolecular isomerism with a polythreaded topology based on octamolybdate building blocks.