Ag6 Cu8 (C=CAr)14 (DPPB)2 : A Rigid Ligand Co-Protected Bimetallic Silver(I)-Copper(I) Cluster with Room-Temperature Luminescence.

Metal clusters have become increasingly important in various applications, with ligands playing a crucial role in their construction. In this study, we synthesized a bimetallic cluster, Ag6 Cu8 (C=CAr)14 (DPPB)2 (Ag6 Cu8 ), using a rigid acetylene ligand, 3,5-bis(trifluoromethyl)phenylacetylide. Through single-crystal structure characterization, we discovered that the butterfly-shaped Ag2 Cu2 motifs were subject to distortion due to steric hindrance imposed by the rigid ligand. These motifs assembled together through shared vertices and edges. Mass spectrometry analysis revealed that the primary fragments detected during electrospray ionization (ESI) testing corresponded to the Ag2 Cu2 motifs. Furthermore, we conducted a comprehensive investigation of the cluster's solution properties employing 31 P NMR, UV-vis absorption, and photoluminescent measurements. In contrast to previously reported Ag/Cu bimetallic clusters protected by flexible ligands, Ag6 Cu8 protected by rigid ligands exhibited intriguing room temperature fluorescence properties alongside excellent thermal stability. DFT calculations on Ag6 Cu8 and Ag6 Cu8 with the rigid aromatic ring removed revealed that the presence of the rigid aromatic ring can lower the electronic energy levels of the cluster, and reduce the energy gap from 4.05 eV to 3.45 eV. Moreover, the rigid ligand further suppressed the non-radiative transition process, leading to room temperature fluorescence emission.

Theoretical understanding of the effect of specifically adsorbed halide anions on Cu-catalyzed CO2 electroreduction activity and product selectivity.

Initial CO2 electroreduction into CO and its subsequent electroreduction pathways were selected to study the effect of specifically adsorbed halide anions X- (X = F, Cl, Br, I) on CO2 electroreduction activity and product selectivity at Cu(111)/H2O interfaces via DFT calculations. The calculated results show that the presence of halide anions can exert a notable effect on the CO2 adsorption characteristics and that chemically adsorbed CO2 molecules can be formed. Furthermore, the halide-anion-modified Cu(111)/H2O interfaces could significantly enhance the initial CO2 electroreduction into CO activity, which is regarded as the rate-determining step during CO2 electroreduction at clean Cu(111)/H2O interfaces. Analysis of the initial CO2 electroreduction and Volmer reaction pathways showed that the halide-anion-modified Cu(111)/H2O interfaces could suppress the HER and thus improve the CO2 electroreduction activity and product selectivity. It is speculated that the enhanced initial CO2 electroreduction activity at the F--, Cl--, Br--, and I--modified Cu(111)/H2O interfaces may originate from the decreased work functions and anion radical ·CO2- formations. Simultaneously, we concluded that dimer OCCO formations in the presence of halide anions were more favorable than CHO during CO electroreduction according to the order of I- > Br- > Cl- > F- and could result in the production of C2 product, suggesting an improved CO2 electroreduction product selectivity. The present analyses of electronic structure may explain the more favorable OCCO formations in the order of I- > Br- > Cl- > F-. The present understanding of this effect will provide an improved scientific guideline for the control of CO2 electroreduction pathways and design of more efficient electrocatalysts.

A comparative study of [Ag11(iPrS)9(dppb)3]2+ and [Ag15S(sBuS)12(dppb)3]+: templating effect on structure and photoluminescence.

Atomically precise silver clusters with tunable photoluminescence (PL) properties have attracted extensive attention due to their great value for basic science and future applications. Here, we report that the addition of a sulfido template into a triangular thiolated silver cluster [Ag11(iPrS)9(dppb)3]·2CF3SO3·CH3OH (Ag11, dppb = 1,4-bis(diphenylphosphino)butane), which is emissive at 660 nm under ambient conditions, produced another silver cluster [S@Ag15(sBuS)12(dppb)3]·CF3SO3·H2O (Ag15) that displays 716 nm emission with a 56 nm redshift aided by the ligand sec-butyl mercaptan. The sulfido template, which affects the geometrical and electronic structures, results in a redshift of Ag11 room-temperature PL as a result of opening up the template-to-metal charge transfer (TMCT) and disturbing the electronic transition between the metal core and ligands at the periphery.

Construction of Silver Clusters Capped by Zwitterionic Ethynide Ligands.

A zwitterionic ligand 3-(triethylammonio)propyne (TAP) has been employed to construct nine silver ethynide compounds for the first time. Single-crystal X-ray analyses reveal that compounds 1 and 2 are silver ethynide assemblies based on the Ag3 subunits and clusters 3-8 are small discrete clusters of Ag3, Ag6, Ag8, and Ag12, respectively, ligated by the bulky TAP ligand with different auxiliary ligands. In addition, upon acquiring the tripod-like tBuPO32-, a unprecedented 80 nuclei silver ethynide cluster was isolated and determined to be [(CF3CO2)5@Ag80(TAP)14(tBuPO3)16(CF3CO2)24]19+ by crystallography and thermogravimetric analysis. The C1 symmetry of Ag80 was deconstructed to be two [Ag40(TAP)7(tBuPO3)8(CF3CO2)12]12+ secondary building subunits arranged in a cross way, with five CF3CO2- trapped in the center. These results highlight that the elaborate selection of ethynide ligands is of great importance in the synthesis of novel silver ethynide clusters.

Controllable synthesis of porous tubular carbon by a Ag+-ligand-assisted Stöber-silica/carbon assembly process.

Herein, in this study, we utilized Ag+-ligand interactions for critically regulating the morphology of carbon by the Stöber-silica/carbon co-assembly method for the first time. Tetraethyl orthosilicate (TEOS) and resorcinol/formaldehyde (RF) assemble upon dictation by Ag+ and pyridyl-functionalized surfactants, producing porous carbon tubes (RF1) with a high surface area of 696 m2 g-1 and accessible mesopores ∼15 nm in size. Furthermore, when using tetrapropyl orthosilicate (TPOS) with a slower hydrolysis rate than that of TEOS, carbon tubes (RF2) with enhanced uniformity and a surface area as high as 2112 m2 g-1 are generated. Additionally, when using dopamine hydrochloride instead of RF as a carbon precursor, tubular polydopamine (TDA) with lengths of tens of microns is fabricated, which exhibits excellent catalytic activity toward oxygen reduction reactions in alkaline solutions due to its unique structural feature, a high surface area of 1350 m2 g-1, metallic silver remains of 8.3 wt%, and a rich nitrogen content of 3.6 wt%. This work sheds light on the engineering of a micellar soft template and synthesizing novel nanostructures by the extension of the Stöber method.

Support vector regression for high-resolution beach surface moisture estimation from terrestrial LiDAR intensity data.

Beach Surface Moisture (BSM) is a key attribute in the coastal investigations of land-atmospheric water and energy fluxes, groundwater resource budgets and coastal beach/dune development. In this study, an attempt has been made for the first time to estimate BSM from terrestrial LiDAR intensity data based on the Support Vector Regression (SVR). A long-range static terrestrial LiDAR (Riegl VZ-2000) was adopted to collect point cloud data of high spatiotemporal resolution on the Ostend-Mariakerke beach, Belgium. Based on the field moisture samples, SVR models were developed to retrieve BSM, using the backscattered intensity, scanning ranges and incidence angles as input features. The impacts of the training samples' size and density on the predictive accuracy and generalization capability of the SVR models were fully investigated based on simulated BSM-intensity samples. Additionally, we compared the performance of the SVR models for BSM estimation with the traditional Stepwise Regression (SR) method and the Artificial Neural Network (ANN). Results show that SVR could accurately retrieve the BSM from the backscattered intensity with high reproducibility (average test RMSE of 0.71% ± 0.02% and R2 of 0.98% ± 0.002%). The Radial Basis Function (RBF) was the most suitable kernel for SVR model development in this study. The impacts of scanning geometry on the intensity could also be accurately corrected in the process of estimating BSM by the SVR models. However, compared to the SR method, the predictive accuracy and generalization performance of SVR models were significantly dependent on the training samples' coverage, size and distribution, suggesting the need for the training samples of uniform distribution and representativeness. The minimum size of training samples required for SVR model development was 54. Under this condition, SVR performed similarly to ANN with a test RMSE of 1.06%, but SVR still performed acceptably (with an RMSE of 1.83%) even using extremely few training samples (only 16 field samples of uniform distribution), far better than the ANN (with an RMSE of 4.02%).

Theoretical insights into the electroreduction mechanism of N2 to NH3 from an improved Au(111)/H2O interface model.

An improved H coverage-dependent Au(111)/H2O electrochemical interface model is proposed in this paper, which is firstly used to study electroreduction mechanisms of N2 into NH3 at the thermodynamical equilibrium potential in cooperation with electronic structure analysis. The results show that the associative mechanism is more favorable on Au(111) and therein alternating and distal pathways may be able to parallelly occur in gas phase and the present simulated electrochemical interface. The initial N2 reduction into the N2H intermediate is the rate determining step, which may be able to be regarded as the origin of the observed experimentally high overpotential during N2 electroreduction. The presence of an electrochemical environment can significantly change the N2 reduction pathway and decrease the barrier of the rate determining step, which can be ascribed to the significant electron accumulation and interaction between N2 molecules and H2O clusters. The theoretical results display excellent consistency with the available experimental data, confirming the rationality of the present proposed electrochemical model. The comparison of the barrier between the hydrogen evolution reaction and rate determining step well explains why the activity of Au electrodes is usually unsatisfactory. Accordingly, a single descriptor can be proposed, in which an ideal electrocatalyst should be able to reduce the barrier for initial N2 electroreduction into N2H. In this way, N2 electroreduction pathways can be facilitated and the yield of NH3 can be enhanced. We believe that the present study can represent progress to study N2 electroreduction mechanisms from an improved electrochemical model.

Nestlike Silver(I) Thiolate Clusters with Tunable Emission Color Templated by Heteroanions.

Four silver thiolate clusters, [H3 O][(Ag3 S3 )(BF4 )@Ag27 (tBuS)18 (hfac)6 H2 O]⋅H2 O (1; hfac = hexafluoroacetylacetone), [(Ag3 S3 )(CF3 CO2 )@Ag30 (tBuS)16 (CF3 CO2 )9 (CH3 CN)4 ]⋅CF3 CO2 ⋅4 CH3 CN (2), [(Ag3 S3 )(MoO4 )@Ag30 (tBuS)16 (CF3 CO2 )9 (CH3 CN)4 ]⋅2 CH3 CN (3), and [(Ag3 S3 )(CrO4 )@Ag30 (tBuS)16 (CF3 CO2 )9 (CH3 CN)4 ]⋅4 CH3 CN (4), were isolated. They have similar nestlike structures assembled by an [Ag3 S3 ]3- template together with one of the BF4 - , CF3 CO2 - , MoO4 2- , or CrO4 2- anions. Interestingly, the solid-state emissions of 2-4 are dependent on the templating anions and are tunable from green to orange and then to red by changing the template from CF3 CO2 - to MoO4 2- and to CrO4 2- , and this may be correlated to the charge transfer between these templates to metal atoms. This work helps to understand the templating role of heteroanions and the relationship between structure and properties.

Density Functional Studies on Photophysical Properties of Boron-Pyridyl-Imino-Isoindoline Dyes: Effect of the Fusion.

In this work, to make out the aryl-fusion effect on the photophysical properties of boron-pyridyl-imino-isoindoline dyes, compounds 1-5 were theoretically studied through analyses of their geometric and electronic structures, optical properties, transport abilities, and radiative (k r) and non-radiative decay rate (k nr) constants. The highest occupied molecular orbitals of aryl-fused compounds 2-5 are higher owing to the extended conjugation. Interestingly, aryl fusion in pyridyl increases the lowest unoccupied molecular orbital (LUMO) level, while isoindoline decreases the LUMO level; thus, 4 and 5 with aryl fusion both in pyridyl and isoindoline exhibit a similar LUMO to 1. Compounds 4 and 5 show relatively low ionization potentials and high electron affinities, suggesting a better ability to inject holes and electrons. Importantly, the aryl fusion is conducive to the decrease of k IC. The designed compound 5 exhibits a red-shifted emission maximum, low λh, and low k IC, which endow it with great potential for applications in organic electronics. Our investigation provides an in-depth understanding of the aryl-fusion effect on boron-pyridyl-imino-isoindoline dyes at molecular levels and demonstrates that it is achievable.

Mechanistic insights into potential dependence of CO electrochemical reduction into C1 products based on a H coverage-dependent Cu(111)/H2O interface model.

A H coverage-dependent Cu(111)/H2O interface model incorporated with electronic structure analysis is employed to investigate the potential dependence of CO electroreduction into C1 products with the aim of solving the long dispute over CO2 electrocatalytic reduction mechanisms. The results indicate that CH4 formation mainly proceeds through CO, CHO, CH2O, CH2OH and CHx (x = 2 and 3) species at various applied potentials. CH3OH may be formed via a CH3O intermediate at high overpotential and the present study can confirm that CH3OH is only produced in a trace amount as detected in experiments. The high overpotential results in the formation of CH4, explaining the experimentally required high overpotential on Cu. The calculated energetics concludes that CO electroreduction into CHO may be a potential-limiting step, being regarded as the origin of the required high overpotentials for CO2 electroreduction in this paper. The electronic structure calculations show that more electronic transfer to the adsorbed H atoms occurs with increasing H coverage, which can be considered as the origin of the more negative electrode potentials. Interestingly, it is observed that the s orbital of the C atom in the valence shell of the adsorbed CO molecule gains more and more electrons, whereas the s orbital of the O atom gains less and less electrons, and even loses electrons with increasing H coverage, implying easier and easier proton transfer towards the C-center site. Thus, the easier occurrence of CO electroreduction may be ascribed to the more electron transfer into the s orbital of the C atom at high overpotential. We believe that the present study represents theoretical progress to systematically study potential-dependent CO2 electroreduction mechanisms on Cu electrodes.

tert-Butyl thiol and pyridine ligand co-protected 50-nuclei clusters: the effect of pyridines on Ag-SR bonds.

Constructing silver(i)-thiolate clusters from simple building blocks usually involves elusive self-assembly processes and remains a long-standing challenge. In this work, we report 6 silver(i)-thiolate clusters protected by pyridines, namely, [Ag3(tBuS)2(Py)(NO3)]n (Py = pyridine) (1), [Ag10(tBuS)6(Py)6(CF3CO2)4]·3Py (2), [Ag12(iPrS)6(Py)8(NO3)6]·2H2O (3), Ag12(iPrS)6(Py)8(CF3CO2)6 (4), Ag12(iPrS)6(4-ap)6(NO3)6 (4-ap = 4-aminopyridine) (5), and [Ag50S13(tBuS)20(Py)12]·4BF4·4Py·4CH3OH·2H2O (6). Single-crystal X-ray crystallography analysis reveals that six clusters are constructed by four types of structural blocks, including the PyAg(tBuS)2 monomer, Py2Ag2(tBuS)2 dimer, Py3Ag3(tBuS)3 trimer and (4-ap)6Ag6(iPrS)6 hexamer. Notably, cluster 6 consists of a rhombic dodecahedron S@Ag14 kernel with 12 interstitial S2- atoms encapsulated by 8 µ4-tBuS- ligands, as well as six unique butterfly-like (Py)2Ag6(tBuS)2 staple motifs composed of a Py2Ag2(tBuS)2 dimer and four silver ions. Moreover, it is found that pyridine ligands have important influence on the construction of silver thiolate clusters and their Ag-SR bond lengths.

An in Situ Template for the Synthesis of Tunable Hollow Carbon Particles for High-Performance Lithium-Sulfur Batteries.

Nanostructured materials with hollow interior voids are gaining great attention due to their fantastic geometries and unique physicochemical properties competent for many applications. However, the development of a fast approach to prepare the hollow structured particles remains challenging. Herein, a new and efficient in situ hard-template method was developed to synthesize hollow carbon nano- and microparticles using the as-prepared SiO2 particles as a hard template directly, without any separation, drying, or redispersion. In this way, the hollow carbon particles with tunable diameters and shell thickness can be synthesized readily, which is simpler and more efficient than the traditional ones. In addition, the universality of this strategy allows us to study the different behaviors of hollow carbon particles in lithium-sulfur batteries when the architectures of hollow particles (i.e., diameter, shell thickness, etc.) were changed. We believe that this in situ method is applicable for synthesizing other core-shell or hollow structured materials (e.g., metal oxide), and also, the high performance of hollow carbon particles in lithium-sulfur batteries and beyond can be further explored.

Mechanistic study on Cu-catalyzed CO2 electroreduction into CH4 at simulated low overpotentials based on an improved electrochemical model.

An improved CO coverage-dependent electrochemical model with explicit relaxed H2O molecules used in CO2 electroreduction is presented, which is firstly applied to Cu-catalyzed CO2 electroreduction into CH4 production at low overpotentials in this paper. The results show that the present defined CH2O and CHOH pathways via common intermediates CHO and CH2 may be able to occur parallelly at the present simulated low overpotential. The potential-limiting steps may be the formation of CO and its further electroreduction into CHO, which are considered as the origin of the observed experimentally high overpotential. The present study also explains why at electrochemical interfaces, only CH4 is observed experimentally on the Cu surface rather than CH3OH. The present results are found to be in excellent agreement with the available experimental data and partial theoretical analysis, further validating the rationality of the present employed methodology.

Hybrid Rare-Earth(III)/Bismuth(III) Clusters Assembled with Phosphonates.

tert-Butylphosphonic acid and rare-earth precursors are employed to construct four trinuclear rare-earth phosphonate clusters, RE3( tBuPO3)2(hfac)5(CH3OH)8]·2CH3OH (RE = Eu, Y, Pr, and Sm; hfac = hexafluoroacetylacetonate), which are composed of three RE3+ ions alternately bridged by two phosphonates. With the introduction of bismuth oxido diketonate, [Bi9O7(hfac)13], three different types of rare-earth/bismuth phosphonate clusters, Bi12RE2 (RE = Pr and Sm), Bi6Eu7, and Bi6Y9, are successfully obtained via variation of the reaction conditions, and they are the first reported examples of bismuth-oxo clusters encapsulated by cyclic rare-earth-oxo or rare-earth/bismuth-oxo phosphonate clusters, respectively. These clusters show obvious absorption in the UV region, and the Eu-containing clusters exhibit bright-red fluorescence.

A theoretical investigation on the thermally activated delayed fluorescence characteristics of the isomers of DTCBPy.

It has been reported that 3, 5-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)-phenyl)(pyridin-4-yl)meth (DTCBPy) is an efficient thermally activated delayed fluorescence (TADF) molecule. We designed a series of the isomeric molecules (2-5) of DTCBPy (1) by changing the position of nitrogen atom in the acceptor and the substituent position of donor units. The highest occupied molecular orbitals (HOMO) of 1-5 are all delocalized over the donor units, and the lowest unoccupied molecular orbitals (LUMO) are located on the acceptor unit. As expected from frontier molecular orbital analysis, the singlet-triplet energy splitting (ΔEST) values of 1-5 are in a small range from 0.087 to 0.147 eV, indicating the easy realization of reverse intersystem crossing from the lowest triplet to singlet excited states. However, the structural modification has a significant influence on the fluorescence radiative rate (kr), which varies from 3.49× 106 to 2.04 × 107 s-1 for 1-5. This work is expected to provide valuable information for synthesizing highly efficient TADF materials based on DTCBPy.

High-nuclearity silver ethynide clusters containing polynucleating oxygen donor ligands.

Polynucleating oxygen donor ligands as precursors have been employed to construct three high-nuclearity heterometallic ethynide clusters. Compound 2 consists of a Cl@Ag12 ethynide cluster capped by two trinuclear organooxotin phosphonate clusters [(nBuSn)3(µ3-O)(tBuPO3)3(OMe)(OH)2]2-. Compound 3 consists of a Ag8 ethynide cluster fused with a nonanuclear oxo-bismuth phosphonate cluster [Bi9O6(tBuPO3)9(tBuPO3H)]4-, while compound 4 is composed of two Cl@Ag15 ethynide clusters bridged by a hexanuclear oxo/hydroxo-bismuth phosphonate cluster [Bi6O4(OH)4(tBuPO3)6(hfac)2(CF3COO)2]10-.

High-Nuclearity Heterometallic tert-Butylethynide Clusters Assembled with tert-Butylphosphonate.

tert-Butylphosphonic acid and lanthanide precursors were employed to construct two high-nuclearity hybrid silver(I)-ytterbium(III) phosphonate clusters: compound 1 consists of a Ag16 ethynide cluster fused with a trinuclear hydroxoytterbium phosphonate cluster, whereas compound 2 is composed of two Ag16 ethynide clusters bridged by a hexanuclear oxo/hydroxoytterbium phosphonate cluster. Using transition-metal-substituted lacunary polyoxotungstates in place of the lanthanide reactant, new phosphonate-functionalized silver(I)-copper(II) ethynide clusters [Ag34 Cu6 (3) and Ag37 Cu6 (4)] and silver(I) ethynide clusters [Ag51 (5) and Ag72 (6)] were obtained. The structures of complexes 3-6 feature core-shell arrangements, in which silver(I)-copper(II) or silver(I) ethynide cluster shells stabilized by peripheral phosphonate ligands enclose different kinds of tungstate core templates.

A simple fluorescent probe for the fast sequential detection of copper and biothiols based on a benzothiazole derivative.

A simple benzothiazole fluorescent chemosensor was developed for the fast sequential detection of Cu2+ and biothiols through modulating the excited-state intramolecular proton transfer (ESIPT) process. The compound 1 exhibits highly selective and sensitive fluorescence "on-off" recognition to Cu2+ with a 1:1 binding stoichiometry by ESIPT hinder. The in situ generated 1-Cu2+ complex can serve as an "on-off" fluorescent probe for high selectivity toward biothiols via Cu2+ displacement approach, which exerts ESIPT recovery. It is worth pointing out that the 1-Cu2+ complex shows faster for cysteins (within 1min) than other biothiols such as homocysteine (25min) and glutathione (25min). Moreover, the compound 1 displays 160nm Stoke-shift for reversibly monitoring Cu2+ and biothiols. In addition, the probe is successfully used for fluorescent cellular imaging. This strategy via modulation the ESIPT state has been used for determination of Cu2+ and Cys with satisfactory results, which further demonstrates its value of practical applications.

Structure-Directing Role of Phosphonate in the Synthesis of High-Nuclearity Silver(I) Sulfide-Ethynide-Thiolate Clusters.

Phosphonate ligands as structure-directing components have been employed to construct four new high-nuclearity silver(I) sulfide-ethynide-thiolate clusters, in which silver(I) aggregates tBuC≡C⊃Ag3, tBuC≡C⊃Ag4, and 2tBuC≡C⊃Ag7 are bridged by tBuS- ligands to engender respective silver(I) ethynide-thiolate clusters functioning as integral shell components, which are supported by phosphonate ligands. In each silver(I) sulfide-ethynide-thiolate cluster, a different encapsulated silver sulfide cluster serves as a core template.

A new simple phthalimide-based fluorescent probe for highly selective cysteine and bioimaging for living cells.

A new turn-on phthalimide fluorescent probe has designed and synthesized for sensing cysteine (Cys) based on excited state intramolecular proton transfer (ESIPT) process. It is consisted of a 3-hydroxyphthalimide derivative moiety as the fluorophore and an acrylic ester group as a recognition receptor. The acrylic ester acts as an ESIPT blocking agent. Upon addition of cystein, intermolecular nucleophilic attack of cysteine on acrylic ester releases the fluorescent 3-hydroxyphthalimide derivative, thereby enabling the ESIPT process and leading to enhancement of fluorescence. The probe displays high sensitivity, excellent selectivity and with large Stokes shift toward cysteine. The linear interval range of the fluorescence titration ranged from 0 to 1.0×10-5M and detection limit is low (6×10-8M). In addition, the probe could be used for bio-imaging in living cells.