Cation- and Anion-Mediated Supramolecular Assembly of Bismuth and Antimony Tris(3-pyridyl) Complexes.
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ABSTRACT:
SUBMITTER: Garcia-Romero A
PROVIDER: S-EPMC8693195 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Abstract Strain induced by lattice distortion is one of the key factors that affect the photovoltaic performance via increasing defect densities. The unsatisfied power conversion efficiencies (PCEs) of solar cells based on antimony chalcogenides (Sb?Chs) are owing to their photoexcited carriers being self?trapped by the distortion of Sb2S3 lattice. However, strain behavior in Sb?Chs?based solar cells has not been investigated. Here, strain tuning in Sb?Chs is demonstrated by simultaneously replacing Sb and S with larger Bi and I ions, respectively. Bi/I codoped Sb2S3 cells are fabricated using poly[2,6?(4,4?bis(2?ethylhexyl)?4H?cyclopenta[2,1?b;3,4?b']dithiophene)?alt?4,7?(2,1,3?enzothiadiazole)] as the hole?transporting layer. Codoping reduced the bandgap and rendered a bigger tension strain (1.76 × 10?4) to a relatively smaller compression strain (?1.29 × 10?4). The 2.5 mol% BiI3 doped Sb2S3 cell presented lower trap state energy level than the Sb2S3 cell; moreover, this doping amount effectively passivated the trap states. This codoping shows a similar trend even in the low bandgap Sb2(SxSe1?x)3 cell, resulting in 7.05% PCE under the standard illumination conditions (100 mW cm?2), which is one of the top efficiencies in solution processing Sb2(SxSe1?x)3 solar cells. Furthermore, the doped cells present higher humidity, thermal and photo stability. This study provides a new strategy for stable Pb?free solar cells. Strain tuning in Sb?Chs was demonstrated by simultaneously replacing Sb and S with larger Bi and I ions, respectively. This strategy has been applied in Sb2(SxSe1–x)3 solar cells, and the champion cell exhibits a PCE of 7.05% under the standard illumination conditions (100 mW cm?2), which is one of the top efficiencies in solution processing Sb2(SxSe1–x)3 solar cells.
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Project description:Five zinc(II) coordination compounds, [ZnCl2(isn)2] (1), [ZnBr2(isn)2] (2), [Zn(NO3)2(H2O)(isn)2] (3), [Zn(CH3COO)2(isn)]2 (4) and [Zn(isn)4(H2O)2](ClO4)2 (5) (isn = isonicotinamide), were prepared by the reactions of the isonicotinamide (pyridine-4-carboxamide, isn) and corresponding zinc(II) salts. Their crystal structures were determined by the single-crystal X-ray diffraction method. The coordination environment of zinc(II) is tetrahedral in the compounds containing small halide anions (chloride, bromide), 1 and 2. An expansion of the zinc(II) coordination environment to the octahedral is observed in the presence of the monodentate and bridging nitrate ions in 3. The coordination environments of both zinc(II) ions in dimeric acetate complex 4 is also enlarged in the comparison with 1 and 2, one zinc(II) ion being octahedrally coordinated and the other being pentacoordinated. The zinc(II) ion in 5 also reaches higher coordination environment (octahedral), which is enabled by binding of additional water molecules, since the perchlorate ion is uncoordinated. The supramolecular amide-amide homosynthon R22(8) is preserved in the presence of halide, nitrate and acetate ions (1-4), but it is completely disrupted in the crystal packing of 5 due to the presence of the bulky perchlorate anion. Spectroscopic analysis of compounds 1-5 was performed by IR spectroscopy in the solid state and by 13C NMR spectroscopy in the DMSO solutions. The NMR data support a complete decomposition of 3 in the DMSO solution, but 1, 2, 4 and 5 remain unchanged in the solution. Thermal properties of the coordination compounds were also investigated by TGA and DSC methods.
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Project description:We report a novel example of supramolecular cages containing a Lewis acidic trigonal boron center. Self-assembly of the tris(pyridyl)borane donor 1 with diruthenium (2) or platinum (3), as an electron acceptor, furnished boron-containing trigonal prismatic supramolecular cages 5 and 6, which were characterized by 1H NMR and electrospray ionization time-of-flight mass spectroscopy and X-ray crystallography. The molecular structure of cage 5 was confirmed as a trigonal prismatic cage with an inner dimension of about 400 Å3. The fluoride binding properties of borane ligand 1 and Pt cage 6 were studied. UV/vis absorption titration studies demonstrated that the boron center of cage 6 undergoes strong binding interaction with the fluoride ion, with an estimated binding constant of 1.3 × 1010 M-2 in acetone based on the 1:2 binding isotherm. The binding was also confirmed by 1H NMR titration. Photoluminescence titration studies showed that cage 6 emitted borane-centered fluorescence (τ = 2.21 ns), which was gradually quenched upon addition of fluoride. When excess fluoride was added to a solution of 6, however, dissociation of the pyridyl ligand from the Pt(II) center was observed.
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Project description:Traditional micelle self-assembly is driven by the association of hydrophobic segments of amphiphilic molecules forming distinctive core-shell nanostructures in water. Here we report a surprising chaotropic-anion-induced micellization of cationic ammonium-containing block copolymers. The resulting micelle nanoparticle consists of a large number of ion pairs (?60,000) in each hydrophobic core. Unlike chaotropic anions (e.g. ClO4(-)), kosmotropic anions (e.g. SO4(2-)) were not able to induce micelle formation. A positive cooperativity was observed during micellization, for which only a three-fold increase in ClO4(-) concentration was necessary for micelle formation, similar to our previously reported ultra-pH-responsive behavior. This unique ion-pair-containing micelle provides a useful model system to study the complex interplay of noncovalent interactions (e.g. electrostatic, van der Waals, and hydrophobic forces) during micelle self-assembly.
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Project description:We construct a fluorescent supramolecular system (TPE-Q4 ⊂ DSP5) of excellent tolerance to a wide range of pH by the facile self-assembly of a new pillar[5]arene bearing disulfonated arms (DSP5) with an AIE-active tetraphenylethene-based tetratopic guest bearing four quaternary ammonium binding sites (TPE-Q4), which exhibits strong blue emission even in dilute aqueous solutions along with much higher quantum yield and longer fluorescence lifetime than TPE-Q4 itself. This appreciable property can be attributed to the supramolecular assembly-induced emission (SAIE) mechanism endowed by the host-guest inclusion complexation based on synthetic macrocycles. Remarkably, the enhanced fluorescence of the supramolecular assembly is quenched efficiently and exclusively by ferric ions in water with a high Stern-Volmer formula constant of 1.3 × 105 mol-1, demonstrating the excellent cation selectivity and visualized responsiveness in ion sensing and detection.
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Project description:The emergence of resistance to vancomycin and related glycopeptide antibiotics is spurring efforts to develop new antimicrobial therapeutics. High-resolution structural information about antibiotic-ligand recognition should prove valuable in the rational design of improved drugs. We have determined the X-ray crystal structure of the complex of vancomycin with N-acetyl-D-Ala-D-Ala, a mimic of the natural muramyl peptide target, and refined this structure at a resolution of 1.3 A to R and R(free) values of 0.172 and 0.195, respectively. The crystal asymmetric unit contains three back-back vancomycin dimers; two of these dimers participate in ligand-mediated face-face interactions that produce an infinite chain of molecules running throughout the crystal. The third dimer packs against the side of a face-face interface in a tight "side-side" interaction that involves both polar contacts and burial of hydrophobic surface. The trimer of dimers found in the asymmetric unit is essentially identical to complexes seen in three other crystal structures of glycopeptide antibiotics complexed with peptide ligands. These four structures are derived from crystals belonging to different space groups, suggesting that the trimer of dimers may not be simply a crystal packing artifact and prompting us to ask if ligand-mediated oligomerization could be observed in solution. Using size-exclusion chromatography, dynamic light scattering, and small-angle X-ray scattering, we demonstrate that vancomycin forms discrete supramolecular complexes in the presence of tripeptide ligands. Size estimates for these complexes are consistent with assemblies containing four to six vancomycin monomers.
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Project description:Supramolecular hydrogels have emerged as a class of promising biomaterials for applications such as drug delivery and tissue engineering. Self-assembling peptides have been well studied for such applications, but low molecular weight (LMW) amino acid-derived gelators have attracted interest as low-cost alternatives with similar emergent properties. Fluorenylmethyloxycarbonyl-phenylalanine (Fmoc-Phe) is one such privileged motif often chosen due to its inherent self-assembly potential. Previously, we developed cationic Fmoc-Phe-DAP gelators that assemble into hydrogel networks in aqueous NaCl solutions of sufficient ionic strength. The chloride anions in these solutions screen the cationic charge of the gelators to enable self-assembly to occur. Herein, we report the effects of varying the anions of sodium salts on the gelation potential, nanoscale morphology, and hydrogel viscoelastic properties of Fmoc-Phe-DAP and two of its fluorinated derivatives, Fmoc-3F-Phe-DAP and Fmoc-F5-Phe-DAP. It was observed that both the anion identity and gelator structure had a significant impact on the self-assembly and gelation properties of these derivatives. Changing the anion identity resulted in significant polymorphism of the nanoscale morphology of the assembled states that was dependent on the chemical structure of the gelator. The emergent viscoelastic character of the hydrogel networks was also found to be reliant on the anion identity and gelator structure. These results demonstrate the complex interplay between the gelator and environment that have a profound and often unpredictable impact on both self-assembly properties and emergent viscoelasticity in supramolecular hydrogels formed by LMW compounds. This work also illustrates the current lack of understanding that limits the rational design of potential biomaterials that will be in contact with complex biological fluids and provides motivation for additional research to correlate the chemical structure of LMW gelators with the structure and emergent properties of the resulting supramolecular assemblies as a function of environment.
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Project description:Bi2 Te3 based thermoelectric alloys have been commercialized in solid-state refrigeration, but the poor mechanical properties restrict their further application. Nanotwins have been theoretically proven to effectively strengthen these alloys and could be sometimes constructed by strong deformation during synthesis. However, the obscure underlying formation mechanism restricts the feasibility of twin boundary engineering on Bi2 Te3 based materials. Herein, thorough microstructure characterizations are employed on a series of Bi0.4 Sb1.6 Te3+ δ alloys to systematically investigate the twins' formation mechanism. The results show that the twins belong to the annealing type formed in the sintering process, which is sensitive to Te deficiency, rather than the deformation one. The Te deficiency combined with mechanical deformation is prerequisite for constructing dense nanotwins. By reducing the δ below -0.01 and undergoing strong deformation, samples with a high density of nanotwins are obtained and exhibit an ultrahigh compressive strength over 250 MPa, nearly twice as strong as the previous record reported in hierarchical nanostructured (Bi, Sb)2 Te3 alloy. Moreover, benefitting from the suppressed intrinsic excitation, the average zT value of this robust material could reach near 1.1 within 30-250 °C. This work opens a new pathway to design high-performance and mechanically stable Bi2 Te3 based alloys for miniature device development.
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Project description:Zn(II) complexes bearing tris[3-(2-pyridyl)-pyrazolyl] borate (Tppy) ligand (1-3) was synthesized and examined by spectroscopic and analytical tools. Mononuclear [TppyZnCl] (1) has a Zn(II) centre with one arm (pyrazolyl-pyridyl) dangling outside the coordination sphere which is a novel finding in TppyZn(II) chemistry. In complex [TppyZn(H2O)][BF4] (2) hydrogen bonding interaction of aqua moiety stabilizes the dangling arm. In addition, solution state behaviour of complex 1 confirms the tridentate binding mode and reactivity studies show the exogenous axial substituents used to form the [TppyZnN3] (3). The complexes (1-3) were tested for their ability to bind with Calf thymus (CT) DNA and Bovine serum albumin (BSA) wherein they revealed to exhibit good binding constant values with both the biomolecules in the order of 104-105 M-1. The intercalative binding mode with CT DNA was confirmed from the UV-Visible absorption, viscosity, and ethidium bromide (EB) DNA displacement studies. Further, the complexes were tested for in vitro cytotoxic ability on four triple-negative breast cancer (TNBC) cell lines (MDA-MB-231, MDA-MB-468, HCC1937, and Hs 578T). All three complexes (1-3) exhibited good IC50 values (6.81 to 16.87 μM for 24 h as seen from the MTS assay) results which indicated that these complexes were found to be potential anticancer agents against the TNBC cells.
| S-EPMC8659194 | biostudies-literature
Project description:The Sb(V) atom in the title compound, [SbCl2(C6H4Br)3], has an almost regular trigonal-bipyramidal geometry with the equatorial plane made up of three C atoms of the bromo-phenyl groups and the axial positions occupied by two Cl(-) ions in a trans configuration. In the crystal, C-H?Br hydrogen bonds link the mol-ecules into zigzag chains along the b-axis direction. Pairs of C-H?Cl hydrogen bonds further link mol-ecules into cyclic dimers with R2(2)(10) ring motifs, generating a three-dimensional network.
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