Bridging Atoms Research Articles

Boosting charge transfer of BiOBr/AgBr S-scheme heterojunctions via interface Br atom co-sharing for enhanced visible-light photocatalytic activity

Efficient interfacial charge transfer and robust interfacial interactions are crucial for achieving the superior spatial separation of carriers and developing efficient heterojunction photocatalysts. Herein, BiOBr/AgBr S-scheme heterojunctions are synthesized via the co-sharing of Br atoms using an ion-exchange approach, which involves the in-situ growth of AgBr nanoparticles on the surfaces of BiOBr nanosheets. It is revealed that successful construction of a high–quality interface with strong interactions via Br atom bridge between BiOBr and AgBr, which provided a rapid migration channel for charge carriers. In addition, in-situ XPS, Kelvin probe force microscopy, and electron spin resonance evaluations confirmed the establishment of an S-scheme charge-transfer pathway in this tightly contacted heterojunction, which could efficiently prevent the recombination of photogenerated carriers while retaining carriers with a high redox capacity. Finally, the photocatalytic test confirmed that the BiOBr/AgBr heterojunction showed excellent photocatalytic performance and wide applicability thanks to the construction of high quality heterojunction. Overall, this work highlights the importance of rational design of heterogeneous interfaces at the atomic level in photocatalysis, and contributes to rationally design BiOBr-based S-scheme heterojunctions photocatalytic materials with high quality atomic co-sharing interfaces.

Experimental and theoretical investigation on vibrational, electronic, and docking characteristics of 1-(3-nitro-phenyl)-5-phenyl-penta-2,4-dien-1-one (1NP5PP)

The 1-(3-nitro-phenyl)-5-phenyl-penta-2,4-dien-1-one (1NP5PP) molecule is subjected to detailed spectroscopic investigation by analyzing the spectra obtained by FT-IR and FT-Raman methods. The computational analysis were performed at DFT level using B3LYP/6-311++G(d, p) basis set. With the support of potential energy distribution the entire vibrational assignment was conducted. A frontier molecular orbital study reveals energy gap is small for the molecule. Molecular electrostatic potential surface shows that highest electronegative around oxygen atom in ethylenic bridge and electropositive region spreads through all the hydrogen atoms in the molecule. Natural bond orbital, nonlinear optical analysis, and Fukui function studies were conducted for the present molecule. The electron distribution and reactive site on the surface of the molecule were analyzed using electron localization function and localized orbital locator analysis. In molecular docking studies the interaction observed between MPRO and the 1NP5PP ligand shows the good degree of inhibition. The above mentioned analogy reflects that 1NP5PP has adequate biological properties.

Electronic Coupling in Triferrocenylpnictogens.

From a fundamental perspective, studies of novel mixed-valent complexes containing ferrocenyl units are motivated by the prospect of improving and extending electron transfer models and theories. Here, the series of triferrocenylpnictogens Fc3E was extended to the heavier analogues (E = As, Sb, and Bi), and the influence of the bridging atom was investigated with Fc3P as a reference. Electrochemical studies elucidate the effect of electrostatic contribution on the large redox splitting (ΔE 1) exhibited by the compounds and solvent stabilization in the case of Fc3As. Structural characterization of the triferrocenylpnictogens combined with spectroelectrochemical studies indicates weak electronic couplings in the related cations [Fc3E]+, suggesting a through-space mechanism.

(Invited) Sulfur Addition Reaction Onto Carbon Nanotubes

The surface chemistry of carbon nanotubes is of interest for material’s processing and modification of their electronic and optical properties. Here, we present a new sulfur addition reaction to single-wall and multi-wall carbon nanotubes. Depending on the reaction conditions, we find strong evidence of addition reaction, which produces covalent bonding between sulfur atoms and the nanotube surfaces. Raman, TEM, and photoemission results are consistent with the formation of covalent S-C bonds on the sidewalls. DFT calculations also support a formation of sulfur-carbon bonding and predict electronic and vibrational states that are in good agreement with the experimental results. Based on a comparison between theory and experiments, we propose a stable episulfide (GS) grafting, which consists of of a sulfur atom bridging two carbon atoms repeated over the nanotube surface.

Triphenylamine[3]arenes: Streamlining Synthesis of a Versatile Macrocyclic Platform for Supramolecular Architectures and Functionalities.

Triphenylamine[3]arenes (TPA[3]s), featuring [16]paracyclophane backbone with alternating carbon and nitrogen bridging atoms, were synthesized through a BF3 ⋅ Et2O-catalyzed cyclization reaction using triphenylamine derivatized monomers and paraformaldehyde. This molecular design yielded a series of TPA[3] macrocycles with high efficiency, with their facile derivatizations also successfully demonstrated. On account of the strong electron-donating properties of the TPA moieties, these TPA[3]s exhibit remarkable delayed fluorescence, and possess a significant affinity for iodine. Furthermore, their inherent three-fold symmetry rendered TPA[3]s as novel building blocks for the construction of extended frameworks and molecular cages. This advancement expands the versatility of discrete macrocycles into complex architectures, enhancing their applicability across a broad spectrum of applications.

Triphenylamine[3]arenes: Streamlining Synthesis of a Versatile Macrocyclic Platform for Supramolecular Architectures and Functionalities

AbstractTriphenylamine[3]arenes (TPA[3]s), featuring [16]paracyclophane backbone with alternating carbon and nitrogen bridging atoms, were synthesized through a BF3 ⋅ Et2O‐catalyzed cyclization reaction using triphenylamine derivatized monomers and paraformaldehyde. This molecular design yielded a series of TPA[3] macrocycles with high efficiency, with their facile derivatizations also successfully demonstrated. On account of the strong electron‐donating properties of the TPA moieties, these TPA[3]s exhibit remarkable delayed fluorescence, and possess a significant affinity for iodine. Furthermore, their inherent three‐fold symmetry rendered TPA[3]s as novel building blocks for the construction of extended frameworks and molecular cages. This advancement expands the versatility of discrete macrocycles into complex architectures, enhancing their applicability across a broad spectrum of applications.

Crystal structure, theoretical calculations, mechanoluminescence feature and antimicrobial activity based on a double-armed Salamo-type ligand and its trinuclear Cu(Ⅱ) complex

A double-armed salamo-type ligand H4L and its Cu(Ⅱ) complex have been designed and synthesized. The stoichiometric ratios of the prepared H4L and its Cu(Ⅱ) complex were structurally characterized by a variety of analytical and spectroscopic techniques, including elemental analysis, FT-IR, UV–visible, fluorescence spectroscopy, and X-ray crystal diffraction. The results showed that H4L is a linear molecule, while the Cu(Ⅱ) complex is a trinuclear structure with three copper atoms exhibiting different coordination modes due to varying coordination cavities and bridging atoms. The quantum chemical parameters and molecular structures of the H4L and the Cu(Ⅱ) complex have been theoretically calculated and studied. Using molecular electrostatic potential (MEP) and density functional theory (DFT) calculations to understand the selectivity of the H4L and the Cu(Ⅱ) complex chemistry and related reactions. Detailed energy level transitions of the H4L and the Cu(Ⅱ) complex can be determined through time-dependent density functional theory (TD-DFT) calculations. In studying the fluorescence properties of liquid and solid states, it was observed that increasing water content leads to the formation of excimer in both the H4L and its Cu(Ⅱ) complex, the ligand H4L shown good mechanoluminescence, but the Cu(Ⅱ) complex did not. We studied the antimicrobial effectiveness of the H4L and the Cu(Ⅱ) complex against E. coli., the Cu(Ⅱ) complex showed higher inhibition of the pathogenic microorganisms.

Bridging Atom Engineering for Low-Temperature Oxygen Activation in a Robust Metal-Organic Framework.

Achieving active site engineering at the atomic level poses a significant challenge in the design and optimization of catalysts for energy-efficient catalytic processes, especially for a reaction with two reactants competitively absorbed on catalytic active sites. Herein, we show an example that tailoring the local environment of cobalt sites in a robust metal-organic framework through substituting the bridging atom from -Cl to -OH group leads to a highly active catalyst for oxygen activation in an oxidation reaction. Comprehensive characterizations reveal that this variation imparts drastic changes on the electronic structure of metal centers, the competitive reactant adsorption behavior, and the intermediate formation. As a result, exceptional low-temperature CO oxidation performance was achieved with T25(Temperature for 25 % conversion)=35 °C and T100 (Temperature for 100 % conversion)=150 °C, which stands out from existing MOF-based catalysts and even rivals many noble metal catalysts. This work provides a guidance for the rational design of catalysts for efficient oxygen activation for an oxidation reaction.

Bridging Atom Engineering for Low‐Temperature Oxygen Activation in a Robust Metal–Organic Framework

AbstractAchieving active site engineering at the atomic level poses a significant challenge in the design and optimization of catalysts for energy‐efficient catalytic processes, especially for a reaction with two reactants competitively absorbed on catalytic active sites. Herein, we show an example that tailoring the local environment of cobalt sites in a robust metal–organic framework through substituting the bridging atom from −Cl to −OH group leads to a highly active catalyst for oxygen activation in an oxidation reaction. Comprehensive characterizations reveal that this variation imparts drastic changes on the electronic structure of metal centers, the competitive reactant adsorption behavior, and the intermediate formation. As a result, exceptional low‐temperature CO oxidation performance was achieved with T25(Temperature for 25 % conversion)=35 °C and T100 (Temperature for 100 % conversion)=150 °C, which stands out from existing MOF‐based catalysts and even rivals many noble metal catalysts. This work provides a guidance for the rational design of catalysts for efficient oxygen activation for an oxidation reaction.

Constructing Heteronuclear Bridging Atoms toward Bifunctional Electrocatalysis

Constructing Heteronuclear Bridging Atoms toward Bifunctional Electrocatalysis

Revealing the Singlet Fission Mechanism for a Silane-Bridged Thienotetracene Dimer.

Tetraceno[2,3-b]thiophene is regarded as a strong candidate for singlet fission-based solar cell applications due to its mixed characteristics of tetracene and pentacene that balance exothermicity and triplet energy. An electronically weakly coupled tetraceno[2,3-b]thiophene dimer (Et2Si(TIPSTT)2) with a single silicon atom bridge has been synthesized, providing a new platform to investigate the singlet fission mechanism involving the two acene chromophores. We study the excited state dynamics of Et2Si(TIPSTT)2 by monitoring the evolution of multiexciton coupled triplet states, 1TT to 5TT to 3TT to T1 + S0, upon photoexcitation with transient absorption, temperature-dependent transient absorption, and transient/pulsed electron paramagnetic resonance spectroscopies. We find that the photoexcited singlet lifetime is 107 ps, with 90% evolving to form the TT state, and the complicated evolution between the multiexciton states is unraveled, which can be an important reference for future efforts toward tetraceno[2,3-b]thiophene-based singlet fission solar cells.

Cori Ester as the Ligand for Monovalent Cations.

Gerty T. and Carl F. Cori discovered, during research on the metabolism of sugars in organisms, the important role of the phosphate ester of a simple sugar. Glucose molecules are released from glycogen-the glucose stored in the liver-in the presence of phosphates and enter the blood as α-D-glucose-1-phosphate (Glc-1PH2). Currently, the crystal structure of three phosphates, Glc-1PNa2·3.5·H2O, Glc-1PK2·2H2O, and Glc-1PHK, is known. Research has shown that reactions of Glc-1PH2 with carbonates produce new complexes with ammonium ions [Glc-1P(NH4)2·3H2O] and mixed complexes: potassium-sodium and ammonium-sodium [Glc-1P(X)1.5Na0.5·4H2O; X = K or NH4]. The crystallization of dicationic complexes has been carried out in aqueous systems containing equimolar amounts of cations (1:1; X-Na). It was found that the first fractions of crystalline complexes always had cations in the ratio 3/2:1/2. The second batch of crystals obtained from the remaining mother liquid consisted either of the previously studied Na+, K+ or NH4+ complexes, or it was a new sodium hydrate-Glc-1PNa2·5·H2O. The isolated ammonium-potassium complex shows an isomorphic cation substitution and a completely unique composition: Glc-1PH(NH4)xK1-x (x = 0.67). The Glc-1P2- ligand has chelating fragments and/or bridging atoms, and complexes containing one type of cation show different modes of coordinating oxygen atoms with cations. However, in the case of the potassium-sodium and ammonium-sodium structures, high structural similarities are observed. The 1D and 2D NMR spectra showed that the conformation of Glc-1P2- is rigid in solution as in the solid state, where only rotations of the phosphate group around the C-O-P bonds are observed.

High-Resolution Photoelectron Imaging of Cryogenically Cooled BiB2- and BiB3- Bismuth-Boron Clusters.

We report a high-resolution photoelectron imaging study of cryogenically cooled BiB2- and BiB3- clusters. Vibrational features are completely resolved for the ground-state detachment transitions, providing critical information about the structures of the anionic clusters and their corresponding neutrals. The electron affinities of BiB2 and BiB3 are accurately measured to be 2.174(1) and 2.121(1) eV, respectively. The B-B and Bi-B stretching frequencies are measured to be 1262 and 476 cm-1, respectively, in the ground state of BiB2. Three vibrational frequencies are measured for the ground state of BiB3: 1194 cm-1 (B-B stretching), 782 cm-1 (B-B stretching), and 339 cm-1 (Bi-B stretching). Both BiB2- and BiB3- and their neutral ground states are found to have planar C2v structures in which the Bi atom bridges two B atoms. BiB2- is found to have a triplet spin state (3B2), consistent with its complicated photoelectron spectra, whereas BiB3- is a doublet (2B1) and neutral BiB3 is closed shell (1A1). Both BiB2 and BiB3 consist of peripheral localized Bi-B and B-B σ bonds and delocalized π and σ bonds.

Postsynthetically Modified Alkoxide-Exchanged Ni2(OR)2BTDD: Synergistic Interactions of CO2 with Open Metal Sites and Functional Groups.

Postsynthetic modifications (PSMs) of metal-organic frameworks (MOFs) play a crucial role in enhancing material performance through open metal site (OMS) functionalization or ligand exchange. However, a significant challenge persists in preserving open metal sites during ligand exchange, as these sites are inherently bound by incoming ligands. In this study, for the first time, we introduced alkoxides by exchanging bridging chloride in Ni2Cl2BTDD (BTDD=bis (1H-1,2,3,-triazolo [4,5-b],-[4',5'-i]) dibenzo[1,4]dioxin) through PSM. Rietveld refinement of synchrotron X-ray diffraction data indicated that the alkoxide oxygen atom bridges Ni(II) centers while the OMSs of the MOF are preserved. Due to the synergy of the existing OMS and introduced functional group, the alkoxide-exchanged MOFs showed CO2 uptakes superior to the pristine MOF. Remarkably, the tert-butoxide-substituted Ni_T exhibited a nearly threefold and twofold increase in CO2 uptake compared to Ni2Cl2BTDD at 0.15 and 1 bar, respectively, as well as high water stability relative to the other exchanged frameworks. Furthermore, the Grand Canonical Monte Carlo simulations for Ni_T suggested that CO2 interacts with the OMS and the surrounding methyl groups of tert-butoxide groups, which is responsible for the enhanced CO2 capacity. This work provides a facile and unique synthetic strategy for realizing a desirable OMS-incorporating MOF platform through bridging ligand exchange.

2X-Rhodamine: A Bright and Fluorogenic Scaffold for Developing Near-Infrared Chemigenetic Indicators.

Chemigenetic fusion of synthetic dyes with genetically encoded protein tags presents a promising avenue for in vivo imaging. However, its full potential has been hindered by the lack of bright and fluorogenic dyes operating in the "tissue transparency" near-infrared window (NIR, 700-1700 nm). Here, we report 2X-rhodamine (2XR), a novel bright scaffold that allows for the development of live-cell-compatible, NIR-excited variants with strong fluorogenicity beyond 1000 nm. 2XR utilizes a rigidified π-skeleton featuring dual atomic bridges and functions via a spiro-based fluorogenic mechanism. This design affords longer wavelengths, higher quantum yield (ΦF = 0.11), and enhanced fluorogenicity in water when compared to the phosphine oxide-cored, or sulfone-cored rhodamine, the NIR fluorogenic benchmarks currently used. We showcase their bright performance in video-rate dynamic imaging and targeted deep-tissue molecular imaging in vivo. Notably, we develop a 2XR variant, 2XR715-HTL, an NIR fluorogenic ligand for the HaloTag protein, enabling NIR genetically encoded calcium sensing and the first demonstration of in vivo chemigenetic labeling beyond 1000 nm. Our work expands the library of NIR fluorogenic tools, paving the way for in vivo imaging and sensing with the chemigenetic approach.

Postsynthetically Modified Alkoxide‐Exchanged Ni2(OR)2BTDD: Synergistic Interactions of CO2 with Open Metal Sites and Functional Groups

AbstractPostsynthetic modifications (PSMs) of metal–organic frameworks (MOFs) play a crucial role in enhancing material performance through open metal site (OMS) functionalization or ligand exchange. However, a significant challenge persists in preserving open metal sites during ligand exchange, as these sites are inherently bound by incoming ligands. In this study, for the first time, we introduced alkoxides by exchanging bridging chloride in Ni2Cl2BTDD (BTDD=bis (1H‐1,2,3,–triazolo [4,5‐b],–[4′,5′‐i]) dibenzo[1,4]dioxin) through PSM. Rietveld refinement of synchrotron X‐ray diffraction data indicated that the alkoxide oxygen atom bridges Ni(II) centers while the OMSs of the MOF are preserved. Due to the synergy of the existing OMS and introduced functional group, the alkoxide‐exchanged MOFs showed CO2 uptakes superior to the pristine MOF. Remarkably, the tert‐butoxide‐substituted Ni_T exhibited a nearly threefold and twofold increase in CO2 uptake compared to Ni2Cl2BTDD at 0.15 and 1 bar, respectively, as well as high water stability relative to the other exchanged frameworks. Furthermore, the Grand Canonical Monte Carlo simulations for Ni_T suggested that CO2 interacts with the OMS and the surrounding methyl groups of tert‐butoxide groups, which is responsible for the enhanced CO2 capacity. This work provides a facile and unique synthetic strategy for realizing a desirable OMS‐incorporating MOF platform through bridging ligand exchange.

Influence of bridging atoms in copper-based coordination polymers for enhancing urease inhibition activity

By using different O-donor second auxiliary ligands, we have designed and synthesized two Cu-based CPs with different bridging atoms to operate as urease inhibitors which show excellent urease inhibitory activity.

Generation and reactivity of the fragment ion [B12I8S(CN)]- in the gas phase and on surfaces.

Gaseous fragment ions generated in mass spectrometers may be employed as "building blocks" for the synthesis of novel molecules on surfaces using ion soft-landing. A fundamental understanding of the reactivity of the fragment ions is required to control bond formation of deposited fragments in surface layers. The fragment ion [B12X11]- (X = halogen) is formed by collision-induced dissociation (CID) from the precursor [B12X12]2- dianion. [B12X11]- is highly reactive and ion soft-landing experiments have shown that this ion binds to the alkyl chains of organic molecules on surfaces. In this work we investigate whether specific modifications of the precursor ion affect the chemical properties of the fragment ions to such an extent that attachment to functional groups of organic molecules on surfaces occurs and binding of alkyl chains is prevented. Therefore, a halogen substituent was replaced by a thiocyanate substituent. CID of the precursor [B12I11(SCN)]2- ion preferentially yields the fragment ion [B12I8S(CN)]-, which shows significantly altered reactivity compared to the fragment ions of [B12I12]2-. [B12I8S(CN)]- has a previously unknown structural element, wherein a sulfur atom bridges three boron atoms. Gas-phase reactions with different neutral reactants (cyclohexane, dimethyl sulfide, and dimethyl amine) accompanied by theoretical studies indicate that [B12I8S(CN)]- binds with higher selectivity to functional groups of organic molecules than fragment ions of [B12I12]2- (e.g., [B12I11]- and [B12I9]-). These findings were further confirmed by ion soft-landing experiments, which showed that [B12I8S(CN)]- ions attacked ester groups of adipates and phthalates, whereas [B12I11]- ions only bound to alkyl chains of the same reagents.

Molecular dipole-modulated visible light photoredox reaction over conjugated polymers

The molecular dipoles of conjugated polymers (CPs) have a great influence on their intrinsic photophysical properties and are one of the key factors affecting the photocatalytic activity. Therefore, we developed a molecular dipole modulation strategy to regulate the configuration of conjugated polymers by changing the symmetry of the monomer molecules and the electronegativity of the bridging atoms to modulate the magnitude of the in-built electric field (IBEF). The optimized SHOP sample has a significant molecular dipole and thus the highest IBEF, which accelerates the dissociation of excitons into electron-hole pairs and facilitates the photocatalytic redox reaction. In addition, CH4 was the principal output of photocatalytic CO2 reduction by SHOP, producing a maximum yield of 743.4 μmol g−1 and a selectivity of 86.2%. On the other hand, SHOP also efficiently converts isochromane to isochroman-1-one in 96.2% yield, realizing a high economic value conversion of a representative substrate molecule. This proposed strategy offers guidance for designing novel CPs photocatalysts for photoredox reactions.

Low-dimensional compounds containing bioactive ligands. Part XXIII: A comprehensive study of the preparation and cytotoxic activities of zirconium(IV) complexes with 8-hydroxyquinoline and its derivatives

Nine zirconium(IV) complexes, [Zr(8-HQ)4]·DMF·H2O (1), [Zr(dClQ)4]·EtOH (2), [Zr(ClNQ)4]·EtOH (3a), [Zr(ClNQ)4]·DMF (3b), [Zr(BrQ)4] (4), [Zr(dBrQ)4]·DME (5), [Zr(2-MedBrQ)4]·2DMF (6), [Zr2Cl2(CQ)4µ2-O(DMF)2]·0.33DMF (7), and [Zr2Cl2(ClBrQ)4µ2-O(DMF)2]·DMF (8) (DME = 1,2-dimethoxyethane, H8-HQ = 8-hydroxyquinoline, HdClQ = 5,7-dichloro-8-hydroxyquinoline, HClNQ = 5-chloro-7-nitro-8-hydroxyquinoline, HBrQ = 7-bromo-8-hydroxyquinoline, HdBrQ = 5,7-dibromo-8-hydroxyquinoline, H2-MedBrQ = 2-methyl-5,7-dibromo-8-hydroxyquinoline, HCQ = 5-chloro-7-iodo-8-hydroxyquinoline, HClBrQ = 5-chloro-7-bromo-8-hydroxyquinoline), have been prepared and characterized by elemental, single crystal X-ray structure analysis and IR spectroscopy. Complexes 1 – 6 are mononuclear complexes with Zr(IV) atoms octacoordinated by four bidentate quinoline ligands. Complexes 7 and 8 are binuclear complexes in which two Zr(IV) atoms are coordinated by two bidentate quinoline, one DMF and one chloro ligands, and the seventh coordination place occupies an oxygen atom bridging both complex species. The stability of complexes soluble in a DMSO was verified by NMR spectroscopy. In vitro cytotoxic properties of complexes 1, 2, 4, 5, and 6, and corresponding ligands were studied against 8 cancer cell lines, and their selectivity was verified on BJ-5ta non-cancerous cell line. The most potent complexes are 1 and 4 with the smallest quinoline ligands.