Lone Pair Research Articles

On the Structure of Tl2Pb(SO4)2 and Crystal Chemistry of Thallium‐Containing Sulfates

AbstractSingle crystal of a thallium‐containing sulfate Tl2Pb(SO4)2 was prepared through hydrothermal crystallization starting from Tl2CO3, Pb(NO3)2 and H2SO4. The crystal structure was solved from single‐crystal X‐ray diffraction data: Tl2Pb(SO4)2 crystallizes in space group R m with lattice parameters of a=5.5955(2) Å, c=22.1001(9) Å, and Z=3, which is also corroborated by Rietveld refinement on X‐ray powder data. The crystal structure can be regarded as [Pb(SO4)2]2− sheets intercalated by double layers of Tl+ along the c‐axis. From a mineralogical perspective, Tl2Pb(SO4)2 belongs to the palmierite family and can further be classified within palmierite‐supergroup. Validation of the structure models was carried out utilizing various concepts including Bond Valence (BV), Charge Distribution (CD) and Madelung Part of Lattice Energy (MAPLE). Notably, a contrast in stereochemical activity of 6s2 lone electron pair (LEP) between Tl+ and Pb2+ is interpreted in terms of bonding behaviours as well as Wang‐Liebau Eccentricity (WLE) parameters. Moreover, an extensive investigation into the crystal chemistry of thallium‐containing sulfates was conducted for the first time, focusing on the coordination environment and bonding behaviour of Tl+ and corresponding WLE parameters. A comparative analysis of these structurally related compounds including Tl2Pb(SO4)2, Tl3H(SO4)2, TlBi(SO4)2, TlIn(SO4)2, TlRh(SO4)2, and TlAl(SO4)2 was delineated.

Hydrothermal synthesis, characterization of Co3Sb4O6F6 and carbon doped Co3Sb4O6F6 and their application towards photocatalytic dye degradation, adsorption, catalytic Knoevenagel condensation and bacterial disinfection

Single crystals of Co3Sb4O6F6 have been grown by employing hydrothermal techniques. Table sugar was utilized to prepare carbon-doped Co3Sb4O6F6. The objective was to employ Co(II)-based metal oxyfluoride comprising a stereochemically active lone pair element (Sb3+) and its carbon-doped analogues for the multifunctional applications. The impact of carbon doping on Co3Sb4O6F6 has been evaluated towards the changes in photocatalytic, catalytic, and adsorbent efficiency. The changes in carbon percentage affect the physical and chemical properties of the host material. A larger percentage of carbon doping turns the photocatalytic ability of the host material into an adsorbent for the removal of dye. The single crystal X-ray diffraction study reveals that Co3Sb4O6F6 crystallizes into cubic symmetry. However, powder X-ray diffraction study reveals the structural transformation in the carbon-doped Co3Sb4O6F6. It also reduces the band gap energy of the host material, and 4 wt% C@Co3Sb4O6F6 turns out to be an efficient photocatalyst. Large-scale carbon doping (15 wt%) appears to be an effective strategy to increase the surface charge and BET surface area, as consequences adsorption property develops in 15 wt% C@Co3Sb4O6F6/H2O2 for the elimination of methylene blue (MB). This favourable chemical adsorption process occurs with large maximum adsorption capacity (qmax = 58.41169 mg g-1), as evident from the Langmuir adsorption isotherm. Scavenger experiment confirms that the photocatalytic activities of the as-synthesised compounds were triggered by the active participation of the hydroxyl radical (.OH). The catalytic efficiencies of both parent and doped compounds are also established for the solvent-free Knoevenagel condensation reaction with 90 % yield at moderate temperature. Bacterial disinfection studies by the ‘Disc diffusion method’ confirm that Co3Sb4O6F6 shows better efficiency than the carbon doped compound against both Gram-positive and Gram-negative bacteria.

Novel binder-free vanadium-based molten salt (NMPV) with low-cost as anode materials of lithium-ion batteries

Molten salt NMPV material is synthesised using a one-step method and applied to binder-free anodes for lithium-ion batteries (LIBs). In this work, simple, low-cost and highly active coordination molten salt electrode materials (NMPV and NMPV-C) were prepared, which overcame the drawbacks of cumbersome and costly preparation of the existing electrode materials. NMPV is formed by the lone pair of electrons of N-methyl pyrrolidone (NMP) molecules coordinated with vanadium ion. The synergistic effect produced by these two and the excellent electrical conductivity and electrochemical properties of the molten salt material itself exhibits satisfactory lithium storage results. The discharge capacities of NMPV-C and NMPV in the second discharge cycle are 669 and 345 mAh g−1, respectively. After 100 cycles, the capacity is maintained at 923 and 549 mAh g−1, respectively. And the capacity retention is 137.97 % and 159.13 %, respectively. In addition, the NMPV-C electrode maintains a stable reversible capacity of 450 mAh g−1 at 2000 mAh g−1 after 220 cycles. Density-functional theory (DFT) calculations revealed that Li+ is more likely to attack H on methyl nitrogen, which is the optimal reaction site for NMPV since the lone pair of electrons of N effectively stabilises the carbon cation after the reaction of Li with H.

Transition State Stabilizing Effects of Oxygen and Sulfur Chalcogen Bond Interactions.

Non-covalent chalcogen bond (ChB) interactions have found utility in many fields, including catalysis, organic semiconductors, and crystal engineering. In this study, the transition stabilizing effects of ChB interactions of oxygen and sulfur were experimentally measured using a series of molecular rotors. The rotors were designed to form ChB interactions in their bond rotation transition states. This enabled the kinetic influences to be assessed by monitoring changes in the rotational barriers. Despite forming weaker ChB interactions, the smaller chalcogens were able to stabilize transition states and had measurable kinetic effects on the rotational barriers. Sulfur stabilized the bond rotation transition state by as much as -7.2 kcal/mol without electron-withdrawing groups. The key was to design a system where the sulfur -hole was aligned with the lone pairs of the chalcogen bond acceptor. Oxygen rotors also could form transition state stabilizing ChB interactions but required electron-withdrawing groups. For both oxygen and sulfur ChB interactions, a strong correlation was observed between transition state stabilizing abilities and electrostatic potential (ESP) of the chalcogen, providing a useful predictive parameter for the rational design of future ChB systems.

Vibrational Features of Oxyamines: A Comparative Study of N,N-Diethylhydroxylamine and N,N-Diethylacetyloxyamine.

The ability of oxyamines to undergo homolytic cleavage of the O-C bond, leading to the formation of stable radicals, is widely used in polymerization processes and to prevent oxidative stress in materials. We present a mid and near-infrared spectroscopy study on two model compounds, N,N-diethylhydroxyloxyamine (C4H11NO) and its acetyl derivative N,N-diethylacetyloxyamine (C6H13NO2) in the liquid phase. The analysis of the spectra is based on a complete exploration of the conformational space, coupled to harmonic and anharmonic calculations performed using the generalized second-order vibrational perturbation theory (GVPT2) formalism at the B3LYP-D3(BJ)/Def2-TZVP level of calculation and potential energy distribution analysis. In the most stable species out of 25, the three amine chains present an all-anti arrangement, with the carbonyl oxygen atom pointing towards the nitrogen lone pair. The simulated spectra are in overall good agreement with the experimental ones, and suitable for the assignment of the main observed bands. Furthermore, similarities and divergences between the two molecules are discussed.

Iodine-Rich Supramolecular Complexes of Chlorobismuthates(III): Unusual Lone Pair Activity and Features of Halogen Bonding in Crystals.

The first chrorobismuthate(III) supramolecular hybrids with halogen-bond-linked I2, (Py(CH2)2Py){[BiCl5](I2)} (1) and (Py(CH2)3Py){[BiCl5](I2)0.5} (2), were synthesized via the reaction between Bi2O3, I2, and salts of the corresponding cations in HCl. The compounds featured one- and two-dimensional (2D) supramolecular motifs built by I···Cl contacts; in the case of 1, Bi(III) is pentacoordinated due to the lone pair activity, which also interacted with I2 pi-orbitals, as confirmed by density functional theory (DFT) calculations. Both complexes exhibited moderate thermal stabilities and relatively narrow optical band gaps.

Light-Up Fluorescence and Circularly Polarized Luminescence in Achiral Interlocked Framework via Adaptive Lone Pair-π Interaction Confinement.

Interactions between lone pairs and aromatic π systems are significant across biology and self-assembled materials. Herein, employing an achiral confinement metal-organic framework (MOF) encapsulates guest molecules, it is successfully realized that lone pair (lp)-π interaction induces fluorescence "turn-on" and circularly polarized luminescence for the first time. The MOFs synthesized based on naphthalenediimide show nearly non-emissive, which can be light-up by introducing acetone or ester guests containing lone pairs-π interaction. Furthermore, the introduction of a series of lp-rich chiral esters induces supramolecular chirality as well as circularly polarized luminescence in achiral MOFs, while also observing chiral adaptability. This work first demonstrates the luminescence and chiral induction via lone pair electrons-π interactions, presenting a fresh paradigm for the advancement of chiroptical materials.

Isolation and Diverse Reactivity of an Unsymmetrical 1,2-Bis(silylene)-Stabilized Pentacarbonyl Chromium(0) Species.

The construction of the unsymmetrical 1,2-bis(silylene) pentacarbonyl chromium(0) complex 1 was achieved through the reaction of chlorosilylene with half an equivalent of K2Cr(CO)5. X-ray diffraction analysis of 1 confirms the formation of the Si-Si bond and the coordination of one of the silicon atoms to the Cr center. Density functional theory (DFT) calculations disclose that highest occupied molecular orbital (HOMO) mainly corresponds to the lone pair of electrons on the silicon atom and the σ-bonding interaction between two Si atoms. Based on its unique electronic structure, its diverse reactivity toward the transition metal compounds and small molecules was investigated in detail. The reactions of 1 with Fe2(CO)9 or CuCl yielded the 1,2-bis(silylene)-stabilized heterobimetallic complex 2 or oxidized product 3, respectively. Additionally, treatments of 1 with selenium, CO2, or Me3SiN3 led to the formation of the corresponding selenium-, oxo-, and nitrogen-bridged complexes 4-7. All compounds were characterized by multinuclear NMR spectroscopy and X-ray crystallography.

Theoretical Investigation of the Effects of Aldehyde Substitution with Pyran Groups in D-π-A Dye on Performance of DSSCs.

This work investigated the substitution of the aldehyde with a pyran functional group in D-π-aldehyde dye to improve cell performance. This strategy was suggested by recent work that synthesized D-π-aldehyde dye, which achieved a maximum absorption wavelength that was only slightly off the threshold for an ideal sensitizer. Therefore, DFT and TD-DFT were used to investigate the effect of different pyran substituents to replace the aldehyde group. The pyran groups reduced the dye energy gap better than other known anchoring groups. The proposed dyes showed facile intermolecular charge transfer through the localization of HOMO and LUMO orbitals on the donor and acceptor parts, which promoted orbital overlap with the TiO2 surface. The studied dyes have HOMO and LOMO energy levels that could regenerate electrons from redox potential electrodes and inject electrons into the TiO2 conduction band. The lone pairs of oxygen atoms in pyran components act as nucleophile centers, facilitating adsorption on the TiO2 surface through their electrophile atoms. Pyrans increased the efficacy of dye sensitizers by extending their absorbance range and causing the maximum peak to redshift deeper into the visible region. The effects of the pyran groups on photovoltaic properties such as light harvesting efficiency (LHE), free energy change of electron injection, and dye regeneration were investigated and discussed. The adsorption behaviors of the proposed dyes on the TiO2 (1 1 0) surface were investigated by means of Monte Carlo simulations. The calculated adsorption energies indicates that pyran fragments, compared to the aldehyde in the main dye, had a greater ability to induce the adsorption onto the TiO2 substrate.

Room-temperature ferroelectric, piezoelectric and resistive switching behaviors of single-element Te nanowires

Ferroelectrics are essential in memory devices for multi-bit storage and high-density integration. Ferroelectricity mainly exists in compounds but rare in single-element materials due to their lack of spontaneous polarization in the latter. However, we report a room-temperature ferroelectricity in quasi-one-dimensional Te nanowires. Piezoelectric characteristics, ferroelectric loops and domain reversals are clearly observed. We attribute the ferroelectricity to the ion displacement created by the interlayer interaction between lone-pair electrons. Ferroelectric polarization can induce a strong field effect on the transport along the Te chain, giving rise to a self-gated ferroelectric field-effect transistor. By utilizing ferroelectric Te nanowire as channel, the device exhibits high mobility (~220 cm2·V−1·s−1), continuous-variable resistive states can be observed with long-term retention (>105 s), fast speed (<20 ns) and high-density storage (>1.92 TB/cm2). Our work provides opportunities for single-element ferroelectrics and advances practical applications such as ultrahigh-density data storage and computing-in-memory devices.

Molecular Analysis of Changes in DNA Binding Affinity and Bending Extent Induced by the Mutations on the Aromatic Amino Residues in Cren7.

Proteins from Crenarchaeal organisms exhibit remarkable thermal stability. The aromatic amino acids in Cren7, a Crenarchaeal protein, regulate protein stability and further modulate DNA binding and its compaction. Specific aromatic amino acids were mutated, and using spectroscopic and theoretical approaches, we have examined the effect of the mutation on the structure, DNA binding affinity, and DNA bending ability of Cren7. The mutants were compared to the structure and function of wild-type (WT) Cren7. The reverse titration profiles were analysed by a noncooperative McGhee-von Hippel model to estimate affinity constant (Ka) and binding site size (n) associated with binding to the DNA. The biolayer interferometry (BLI) measurements showed that the binding affinity decreased at higher salt concentrations. For theoretical analysis of the extent of DNA bending, radius of gyration and bending angle were compared for WT and mutants. The time evolution of order parameters based on the translational and rotational motion of tryptophan residue (W26) was used for the qualitative detection of stacking interactions between W26 of Cren7 and DNA nucleobases. It was observed that the orientation of W26 in F41A favored the formation of a new lone pair-lone pair interaction between DNA and Cren7. Consequently, in thermostable proteins, the aromatic residues at the terminus maintain structural stability, whereas the residues at the core optimize the degree of DNA bending and compaction.

Spectroscopic, computational, docking, and cytotoxicity investigations of 5-chloro-2-mercaptobenzimidazole as an anti-breast cancer medication

The vibrations were attributed to 5-chloro-2-mercaptobenzimidazole using FTIR and FT-Raman spectroscopy. The optimized geometrical parameters, IR intensity, and the Raman activity of the vibrational bands were estimated using the Becke three-parameter Lee-Yang-Parr functional and the 6-311++G(d,p) level of theory. These findings are compared with the experimental data. The molecule’s HOMO-LUMO energy gap is found to be 4.418 eV. UV-Vis analysis reveals that the π→π* transition, which happens when electron density shifts from nitrogen, sulfur, and chlorine atoms in the molecule, to the electrons of the C-C bonds of the ring. Total density of states was used to assess the molecular orbital contributions. There are 47α and 47β electrons totaling 94 electrons in the DOS spectrum. NBO investigations indicate that a considerable stabilizing energy of 30.37 and 30.90 Kcal/mol was revealed by the lone pair transition of N1 and N3 atoms to π*(C7-C8) and π*(C4-C9). The more electrophilic region, as seen by the red zone in MEP mapping, lies in the vicinity of the nitrogen and sulfur atoms. The molecule’s hydrogen atoms are found in the blue nucleophilic area. The theoretical chemical shifts for 1H and 13C NMR ranged from 7.03 to 8.23 ppm and 113.10 to 207.31 ppm, respectively. The docking research showed that the molecule attached to protein 1AQU with a greater binding energy of −6.8 Kcalmol−1. The cytotoxicity of the sample was evaluated against a MCF-7 cell line (IC50 = 16.54 µg/ml) and exhibited a good breast cancer action. In addition, ADMET prediction has been used to estimate the medicinal applicability of the chemical.

Structure of N-acetoxy-N-benzyloxyurea

The crystal structure of N-acetoxy-N-benzyloxyurea has been studied by single crystal X-ray diffraction study. It has demonstrated that this compound is a typical anomeric amide. ON(1)O nitrogen atom has a pyramidal configuration; the sum of the bond angles centered on N(1) atom is 335.20 and this atom is sp3 hybridized. The N(2) nitrogen atom of the carbamoyl moiety (H2NC=O) has planar configuration. The N–OAc bond is somewhat elongated and the N–OBn bond is shortened due to the action of nO(Bn)*N–OAc anomeric effect. In the molecule of N-acetoxy-N-benzyloxyurea, the N–C amide bonds are nonequivalent, and the (AcO)(BnO)N–C(O) bond is longer that the H2N–C(O) bond. Evidently, that this difference in bond lengths is caused by the stronger conjugation between lone pair (Lp) of the N(2) atom and the C=O carbonyl compared to conjugation between the lone pair of N(1) atom and the C=O carbonyl. The overall analysis of the structural parameters on all known N-acyloxy-N-alkoxyureas had been done. In addition, the structural parameters of N-acetoxy-N-benzyloxyurea have been compared with the same structural parameters of N-benzyloxyurea and N-benzyloxy-N-methoxyurea.

Controlling Triboelectric Charge of MOFs by Leveraging Ligands Chemistry.

Metal-organic frameworks (MOFs) have emerged as promising materials for triboelectric nanogenerators (TENGs), but the effects of ligand choice on triboelectric charge remain underexplored. Hence, this paper demonstrates the effect of single, binary, and ternary ligands on TENG performance of cobalt/cerium-based (Co─Ce) bimetallic MOFs utilizing 2-methylimidazole (2Melm), terephthalic acid (BDC), and benzene tricarboxylic acid (BTC) as ligands. The detailed structural characterization revealed that varying ligand chemistries led to distinct MOF features affecting TENG performance. Single ligand bimetallic MOFs (designated as CoCe-2MeIm, CoCe-BDC, CoCe-BTC) has lower performance than binary ligand (designated as CoCe-2MeIm-BDC, CoCe-2MeIm-BTC, CoCe-BDC-BTC) and ternary ligand MOFs (designated as CoCe-2MeIm-BDC-BTC). Among all, the binary ligand MOF, CoCe-2MeIm-BTC, shows the best results (598V, 26.7µA) due to the combined effect of imidazole ring and (─COO─) groups. This is attributed to lone pairs on nitrogen atoms and a delocalized π-electron system in imidazole system in this material. CoCe-BTC has the lowest results (31V, 3.2µA) due to the bulkier nature of the electron-withdrawing (─COO─) groups and their impact on the π-electron system of the benzene ring. This study showcases the potential of ligand chemistry manipulation to control triboelectric charge and thereby enhance MOF-based TENG performance.

Low Valence Triel (I) Systems as Hydrogen Bond Acceptors and their Stability with Respect to Triel (III) Compounds.

A theoretical study of the complexes formed by carbene like Al(I), Ga(I), In(I) and Tl(I) compounds with hydrogen bond donors (HBD), XH (HCCH, HSH,HOH, HCN, HCl, HBr, HF, and HNC) have been carried out at MP2 computational level. The isolated triel(I) compounds show a negative region of the molecular electrostatic potential region associated with the triel atom suitable to interact with electron deficient groups. This region is associated to a lone pair based on the ELF analysis and to the location of the HOMO orbital. The complexes are similar to those found in nitrogen heterocyclic carbenes (NHC) with HBD. In addition, the oxidative addition reactions of those complexes to yield the corresponding valence III compounds have been characterized. The Al(III) compounds are much more stable than the corresponding Al(I) complexes. However, the stability of the triel(III) compounds decreases with the size of the triel atom and for the thallium derivatives, the Tl(I) complexes are more stable than the Tl(III) compounds in accordance with the number of the structures found in the CSD. The barrier of the TS connecting the triel(I) and triel(III) systems increases with the size of the triel atoms.

Synthesis, crystals structures, DFT, and anticancer activities of polycyclic heterocyclic quinones

In this work, we synthesized six polycyclic heterocyclic quinones (PHQs) and one unexpected product (compound 6). We verified all of their structures by 1HNMR, 13CNMR, and HRMS and obtained four crystal structures of the seven products. At first, we compared the crystal structures with crystal structures similar to those reported in the literature and explained their differences by conjugative effect, hyperconjugative effect, and electrostatic effect. Then, we compared the crystal structure of compound 6 with the calculated structure of compound 6. The natural bond orbital analysis showed that the calculated structure formed intramolecular hydrogen bonds, whereas the crystal structure formed intermolecular hydrogen bonds but not intramolecular hydrogen bonds. The main reason for this difference was not due to the atomic charge or the interatomic distance, but rather the energy levels of the orbitals of the lone-pair electrons. In crystal structures, the intermolecular interactions contained many weak interactions, and we used the hydrogen atom substitution (HAS) method to divide the total intermolecular interactions as several independent weak interactions and to calculate their energies. The HAS method was often successful if the substituted group did not have a strong effect on the electronic structure of the entire molecule, and we found examples in the calculations of energies of weak interactions of crystal structure of compound 6 and compound 3a. An unsuccessful example of the HAS method was the substitution of C = O group with CH2 group to eliminate the O…H-N hydrogen bond interaction from the total interaction. According to the HAS method, our calculations showed that the strength order of the weak interactions was as follows: π-π stacking > hydrogen bond > n-π stacking > σ-π stacking. For the hydrogen bond, the strength order was as follows: C = O…H-N > CCl…H-N > C-F…H-N. For n-π stacking interaction, the strength order was as follows: Cl-π > N-π > F-π. Finally, we selected five synthesized PHQs to test anticancer activities and some of them showed better anticancer activities than the positive control drugs.

Green Preparation of S, N Co-Doped Low-Dimensional C Nanoribbon/C Dot Composites and Their Optoelectronic Response Properties in the Visible and NIR Regions.

The green production of nanocomposites holds great potential for the development of new materials. Graphene is an important class of carbon-based materials. Despite its high carrier mobility, it has low light absorption and is a zero-bandgap material. In order to tune the bandgap and improve the light absorption, S, N co-doped low-dimensional C/C nanocomposites with polymer and graphene oxide nanoribbons (the graphene oxide nanoribbons were prepared by open zipping of carbon nanotubes in a previous study) were synthesized by one-pot carbonization through dimensional-interface and phase-interface tailoring of nanocomposites in this paper. The resulting C/C nanocomposites were coated on untreated A4 printing paper and the optoelectronic properties were investigated. The results showed that the S, N co-doped C/C nanoribbon/carbon dot hybrid exhibited enhanced photocurrent signals of the typical 650, 808, 980, and 1064 nm light sources and rapid interfacial charge transfer compared to the N-doped counterpart. These results can be attributed to the introduction of lone electron pairs of S, N elements, resulting in more transition energy and the defect passivation of carbon materials. In addition, the nanocomposite also exhibited some electrical switching response to the applied strain. The photophysical and doping mechanisms are discussed. This study provides a facile and green chemical approach to prepare hybrid materials with external stimuli response and multifunctionality. It provides some valuable information for the design of C/C functional nanocomposites through dimensional-interface and phase-interface tailoring and the interdisciplinary applications.

Theoretical investigation of the effects of diverse hydrogen-bonding characteristics on the 17O chemical shielding and electric field gradient tensors within the active sites of MraYAA bound to nucleoside antibiotics capuramycin, carbacaprazamycin, 3′-Hydroxymureidomycin A, and muraymycin D2

This study builds upon our prior researches and seeks to investigate and clarify the influences of various characteristics of hydrogen bonds (H-bonds) and charge transfer (CT) interactions, which were detected within the inhibitor binding pockets (labeled as the QM models I–IV) of MraYAA–capuramycin, MraYAA–carbacaprazamycin, MraYAA–3′-hydroxymureidomycin A, and MraYAA–muraymycin D2 complexes by QTAIM and NBO analyses from DFT QM/MM MD calculations, on the 17O chemical shielding (CS) and electric field gradient (EFG) tensors of carboxylate (Oδ), carbonyl (C═O), and hydroxyl (O–H) oxygens in these models. The 17O CS and EFG tensors of these three types of oxygens in QM models I–IV were calculated at the M06-2X/6-31G** level by including the solvent effects using the polarizable continuum model. From the computed 17O CS and EFG tensors in these models, it was found that the nuclear shielding, σiso, for carboxylate or carbonyl oxygen increases (shielding effect) as the H-bond length decreases and the percentage p-character of nOδ/nC═O lone pair partner in the CT interaction enhances. In contrast, the σiso (17O–H) decreases (deshielding effect) with a reduction in the H-bond length as well as with an enhancement in percentage s-character of the nOH lone pair/σ*O–H antibond. By reducing the H-bond length or by increasing p-character of the nOδ/nC═O lone pair, the 17Oδ/17O═C quadrupole coupling constant smoothly decreases, while the 17Oδ/17O═C asymmetry parameter smoothly increases. Moreover, these calculated parameters are in a good agreement with the experimental values. The information garnered here is valuable particularly for further understanding of empirical correlations between 17O NMR spectroscopic and H-bonding characteristics in the protein–ligand complexes.

Synergizing Steric Hindrance and Stacking Interactions To Facilitate the Controlled Assembly of Multiple 41 Metalla‐Knots and Pseudo‐Solomon Links

AbstractIn this work, a noncoplanar terphenyl served as a building block to synthesize a novel 3,3′‐substituted bipyridyl ligand (L1) which further reacted with binuclear half‐sandwich units A/B, giving rise to two aesthetic 41 metalla‐knots in high yields via a coordination‐driven self‐assembly strategy. Furthermore, given the inherent compactness of the 41 metalla‐knots, it creates favorable conditions for the emergence of steric repulsion. We focused on progressively introducing nitrogen atoms featuring a lone pair of electrons (LPEs) into ligand L1 to manipulate the balance of H⋅⋅⋅H/LPEs⋅⋅⋅LPEs steric repulsion during the assembly process, ultimately achieving controlled assembly from 41 metalla‐knots to the pseudo‐Solomon link and then to molecular tweezer‐like assembly facilitated by stacking interactions. All the assemblies were well characterized by solution‐state NMR techniques, ESI‐TOF/MS, and single‐crystal X‐ray diffraction. The evolutionary process of the topological architectures is equivalent to visualizing the synergistic effect of steric hindrance and stacking interactions on structural assembly, providing a new avenue for achieving the controlled synthesis of different topologies.

Synergizing Steric Hindrance and Stacking Interactions To Facilitate the Controlled Assembly of Multiple 41 Metalla-Knots and Pseudo-Solomon Links.

In this work, a noncoplanar terphenyl served as a building block to synthesize a novel 3,3'-substituted bipyridyl ligand (L1) which further reacted with binuclear half-sandwich units A/B, giving rise to two aesthetic 41 metalla-knots in high yields via a coordination-driven self-assembly strategy. Furthermore, given the inherent compactness of the 41 metalla-knots, it creates favorable conditions for the emergence of steric repulsion. We focused on progressively introducing nitrogen atoms featuring a lone pair of electrons (LPEs) into ligand L1 to manipulate the balance of H⋅⋅⋅H/LPEs⋅⋅⋅LPEs steric repulsion during the assembly process, ultimately achieving controlled assembly from 41 metalla-knots to the pseudo-Solomon link and then to molecular tweezer-like assembly facilitated by stacking interactions. All the assemblies were well characterized by solution-state NMR techniques, ESI-TOF/MS, and single-crystal X-ray diffraction. The evolutionary process of the topological architectures is equivalent to visualizing the synergistic effect of steric hindrance and stacking interactions on structural assembly, providing a new avenue for achieving the controlled synthesis of different topologies.