Search

Organometallic reagents such as organolithium and Grignard reagents have long been esteemed in chemical synthesis for their exceptional reactivity. In contrast, the application of their sodium and potassium counterparts has been comparatively sluggish, notwithstanding their augmented reactivity stemming from their heightened ionic character. This inertia persists due to the constrained accessibility of these heavy alkali metal reagents. In this study, our focus was directed towards devising a convenient and pragmatic approach for fabricating heavy alkali metal-based reagents, particularly those grounded in potassium. Herein, we present a novel, direct method for generating stannylpotassium (Sn-K) reagents through the simple combination of readily available silylstannanes and t -BuOK. Subsequently, the generated Sn-K reagents were effectively harnessed for stannylative substitution of aryl halides, furnishing an array of arylstannanes straightforwardly under transition metal-free conditions. This application distinctly underscores the potential utility of highly reactive Sn-K species, hitherto sparingly tapped into within the realm of synthetic organic chemistry. Furthermore, our investigation confirms that Sn-K reagents manifest notably superior reactivity compared with their well-established stannyllithium (Sn-Li) counterparts. This heightened reactivity can be ascribed to the increasing ionic character of Sn-K, which was supported by computational experiments., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

Silylation of aryl and alkenyl triflates is found to occur readily with silylboronic esters as a silicon source under copper catalysis. The silyl moieties are exclusively installed into the organic frameworks through the preferential generation of a silylcopper species, wherein base-mediated direct borylation is totally suppressed. The combined use of tri- n -butylphosphine and 4,4'-diphenyl-2,2'-bipyridine as a ligand combination turned out to be indispensable for achieving the high catalytic activity.

The Lewis basicity of a μ 3 -oxo ligand for (μ 3 -O)[Rh(cod)] 3 (μ 4 -O)M (cod = 1,5-cyclooctadiene) complexes was controllable by metal species on the μ 4 -oxo ligand locating at the opposite site of the μ 3 -oxo ligand. Coordination of the μ 3 -oxo ligand of [(μ 3 -O){Rh(cod)} 3 (μ 4 -O){Au(PPh 3 )}][BF 4 ] (1) to [Au(PPh 3 )] + indicated sufficient Lewis basicity of the μ 3 -oxo ligand in 1 to form [{(Ph 3 P)Au}(μ 3 -O){Rh(cod)} 3 (μ 4 -O){Au(PPh 3 )}][BF 4 ] (2). In contrast, the addition of Li + to 1 induced elimination of the originally coordinated [Au(PPh 3 )] + due to the weak Lewis basicity of the μ 3 -oxo ligand for (μ 3 -O){Rh(cod)} 3 (μ 4 -O)Li(THF) 3 , in which a pentanuclear species, [{(Ph 3 P)Au}(μ 3 -O){Rh(cod)} 3 (μ 4 -O){Li(THF) 3 }][BF 4 ] (3), was assumed to be generated in situ before the dissociation of [Au(PPh 3 )] + .

An enzyme-fueled transient volume phase transition (TVPT) of hydrogels under out-of-equilibrium conditions is reported. The approach takes inspiration from the metabolic cycle, comprising nutrient intake and anabolism/catabolism followed by waste excretion. The incorporation of methacrylic acid and acrylated trypsin in a polymeric hydrogel allowed the TVPT of the gel to be fueled by lysozyme. With the intake of lysozyme as fuel, the construction/destruction of electrostatic cross-linkages induced transient shrinkage/swelling of the gel accompanied by the depletion of lysozyme activity. The system's transient response could be flexibly programmed by adjusting not only the fuel concentration but the chemical composition of materials. The lysozyme-fueled TVPT of the gel could be exploited to transient changes in the mechanical properties of the gel. Our work opens a route toward a new class of stimuli-responsive hydrogels for biomedical applications.

Direct, transition metal-free B(dan)-installation into organic frameworks has been developed. Heteroaryl-H bonds were transformable into the respective heteroaryl-B(dan) bonds through deprotonation. The resulting heteroaryl-B(dan) compounds, which are otherwise difficult to access, can undergo the direct Suzuki-Miyaura coupling. The method was demonstrated to apply to a silicon nucleophile, giving Lewis acidity-diminished stable silyl-B(dan) and -B(aam) in one pot.

Lewis acidity of organoboronates [B(pin), B(neop), B(cat), B(eg), B(nad)] and organoboronamides [B(dan), B(aam), B(mdan)] has been found to be unifiedly evaluated by computed ammonia affinity (AA), while other methods [LUMO energies, global electrophilicity index (GEI), fluoride ion affinity (FIA)] were only partially applicable. The relationships between the AA values and such structural characters including the B-X bond lengths, the X-B-X angles, and the changes in the B-X bond lengths in the formation of the ammonia adducts were also described., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Stabilization of low oxidation gold anions as aurate or auride by organic ligands has long been a synthetic challenge, owing to the proneness of low-valent gold centres to cluster. Despite being the most electronegative metal, isolable gold(I) aurate complexes have only been obtained from a few σ-withdrawing organo- and organo-main group ligands. Stabilization of highly-reduced gold complexes by π-modulating redox active ligands has only been achieved by cyclic (amino)(alkyl)carbene (CAAC), which is limited to 1e - -reduction to form neutral gold(0) complexes. This work reports a simple modular synthesis of a boron, nitrogen-containing heterocyclic carbene ( Cl BNC) at a gold(I) center through metal-assisted coupling between azadiboriridine and isocyanides. The anionic electrophilic Cl BNC ligand in the gold(I) complex [( Cl BNC)AuPMe 3 ] (3a and 3b) allows a 2e - -reduction to form the first η 1 -carbene aurate complex [(BNC)AuPMe 3 ]Li(DME) (5a, DME = dimethoxyethane). Single crystal crystallographic analysis and computational studies of these complexes revealed a highly π-withdrawing character of the neutral 4π B,N-heterocyclic carbene (BNC) moiety and a 6π weakly aromatic character with π-donating properties to the gold(I) fragment in its reduced form, showcasing the first cyclic carbene ligand that allows electronic tunability between π-withdrawing (Fischer-type)- and π-donating (Schrock-type) properties.

A new dimethyl(phenyl)silylborane having a naphthalene-1,8-diaminato (dan) substituent on the boron center, PhMe 2 Si-B(dan), was synthesized. Owing to the diminished boron Lewis acidity, it is highly stable toward air. Synthetic application of the silylborane to catalytic silylboration and silylation of alkynes is also described.

To use atomically precise metal nanoclusters (NCs) in various application fields, it is essential to establish size-selective synthesis methods for the metal NCs. Studies on thiolate (SR)-protected gold NCs (Au n (SR) m NCs) revealed that the atomically precise Au n (SR) m NC, which has a different chemical composition from the precursor, can be synthesized size-selectively by inducing transformation in the framework structure of the metal NCs by a ligand-exchange reaction. In this study, we selected the reaction of [Au 25 (SC 2 H 4 Ph) 18 ] - (SC 2 H 4 Ph = 2-phenylethanethiolate) with 4- tert -butylbenzenethiol ( t BuPhSH) as a model ligand-exchange reaction and attempted to obtain new metal NCs by changing the amount of thiol, the central atom of the precursor NCs, or the reaction time from previous studies. The results demonstrated that [Au 23 (SPh t Bu) 17 ] 0 , [Au 26 Pd(SPh t Bu) 20 ] 0 (Pd = palladium) and [Au 24 Pt(SC 2 H 4 Ph) 7 (SPh t Bu) 11 ] 0 (Pt = platinum) were successfully synthesized in a high proportion. To best of our knowledge, no report exists on the selective synthesis of these three metal NCs. The results of this study show that a larger variety of metal NCs could be synthesized size-selectively than at present if the ligand-exchange reaction is conducted while changing the reaction conditions and/or the central atoms of the precursor metal NCs from previous studies., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Generation of dihydrogen from water splitting, also known as water reduction, is a key process to access a sustainable hydrogen economy for energy production and usage. The key step is the selective reduction of a protic hydrogen to an accessible and reactive hydride, which has proven difficult at a p-block element. Although frustrated Lewis pair (FLP) chemistry is well known for water activation by heterolytic H-OH bond cleavage, to the best of our knowledge, there has been only one case showing water reduction by metal-free FLP systems to date, in which silylene (Si II ) was used as the Lewis base. This work reports the molecular design and synthesis of an ortho -phenylene linked bisborane-functionalized phosphine, which reacts with water stoichiometrically to generate H 2 and phosphine oxide quantitatively under ambient conditions. Computational investigations revealed an unprecedented multi-centered electron relay mechanism offered by the molecular framework, shuttling a pair of electrons from hydroxide (OH - ) in water to the separated proton through a borane-phosphonium-borane path. This simple molecular design and its water reduction mechanism opens new avenues for this main-group chemistry in their growing roles in chemical transformations., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Abiotic oligomeric ligands with a strong affinity for a target peptide sequence were isolated by affinity purification from a pool of 30-mer acrylic random ter-oligomers that were synthesized via a controlled radical polymerization process. Our results indicate that the oligomeric ligands with suitable sequence and/or stereochemical configurations for the target can be isolated from as-polymerized random co-polymers based on the affinity to the target. This process will be a powerful tool for the development of stable and inexpensive ligands that can be used to detect, neutralize and purify proteins with a target epitope sequence.

Isolation and structural characterization of hypervalent electron-rich pentacoordinate nitrogen species have not been achieved despite continuous attempts for over a century. Herein we report the first synthesis and isolation of air stable hypervalent electron-rich pentacoordinate nitrogen cationic radical ( 11-N-5 ) species from oxidation of their corresponding neutral ( 12-N-5 ) species. In the cationic radical species, the nitrogen centers adopt a trigonal bipyramidal geometry featuring a 3-center-5-electron hypervalent attractive interaction. The combination of single crystal X-ray diffraction analysis and computational studies revealed weak N-O interactions between the central nitrogen cation and oxygen atoms. This successful design strategy and isolation of air-stable pentacoordinate hypervalent nitrogen species allow further investigations on reactivity and properties resulting from these unusually weakly coordinating interactions in nitrogen compounds., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The coordination chemistry of our recently isolated bis(diphenylphosphinyl)-functionalized dipyrido-annulated NHC (N-heterocyclic carbene), dpa P2 -NHC, towards copper(i) and silver(i) has been studied. Based on dpa P2 -NHC, two dinuclear silver and copper complexes [2, (Ag 2 L 2 ) and 3, (Cu 2 L 2 )], two tetranuclear copper complexes {4, [Cu 4 L 2 (NCMe) 2 ] and 6, (Cu 4 LBr 4 )} and a pentanuclear copper complex [5, (Cu 5 L 2 Br 3 )] exhibiting strong intramolecular metal-metal interactions were achieved and characterized. All the complexes exhibited dynamic behavior in solution, in which the NMR coalescence of 2 was well resolved at low temperature (below 208 K) and dissociation for 2 was observed according to the calculated Eyring plot. Ag 2 L 2 (2) shows a similar coordination sphere to that of our previously reported gold complex Au 2 L 2 ; Cu 2 L 2 (3) features a rare μ 2 -bridging carbene and a terminal carbene; Cu 4 LBr 4 (6) is neutral and monomeric, in which four copper atoms were rigidly fixed by the tridentate dpa P2 -NHC ligand and bromide anions. All the complexes (2-6) were luminescent at room temperature, in which 4-6 provided phosphorescence at 77 K. Based on the comparison of the emission bands with dpa P2 -NHC, we conclude that the electronic transitions of 2-6 can be attributed to the ligand-centered (LC) transitions.

Structurally characterized hexacoordinate organophosphorus compounds remain rare due to their highly reactive nature and thermal instability. Herein we report the first synthesis of a pair of O-facial and O-meridional hexacoordinate oxaphosphates ( 5B and 5D ) obtained from the O-apical and O-equatorial β-hydroxyalkylphosphoranes 3 and 4 . This was achieved by using the bulky C 2 F 5 -groups on the ortho-substituted aryl backbone. Calculations of the relative energies of possible isomers indicate 5B and 5D are thermodynamic products. Although the mechanisms of their formation and the determining factor of stereo-selectivity are still unclear, their isolation and structure conformation contributes to a formulation of a viable strategy for diastereoselective synthesis of heteroleptic hexacoordinate organophosphates.

pK a tuning of Brønsted acids in synthetic nano-materials is of great importance for the design of ion exchange and bio-/molecular-separation media and polymer catalysis. It has been reported that hydrogel nanoparticles with carboxylic acids that show large and reversible pK a shifts in response to thermal stimuli can be prepared by copolymerization of N-isopropylacrylamide (NIPAm), acrylic acids (AAc) and N,N'-methylene bisacrylamide (BIS) via the proton imprinting polymerization process. However, the reported range of pK a shifts is limited to the range of 5.3 to 7.5. In this study, we report a procedure to prepare proton imprinted NPs that show pK a shifts in the tuned pK a range and demonstrate applications of the NPs. pK a values ranging from 4.3 to 8.7 were achieved by designing the structure of monomers containing carboxylic acids and applying the proton imprinting procedure. It was demonstrated that proton-imprinted NPs with different pK a values could be used for the reversible and selective protonation of target molecules which have specific pK a values. Our results establish the generality of the proton imprinting procedure and provide a guide for designing stable and inexpensive materials for sophisticated purification processes.

Due to the simplicity of their composition, the study of the superconducting properties of elemental substances holds significant importance for understanding the mechanisms of high-temperature superconductivity. This work involves simulated calculations to investigate the phase transition sequence and superconducting properties of Sr under pressure. The stability range of the Sr-IV phase C2/c was redefined, determining that it can extend up to 150 GPa, and the phase transition sequence of Sr under high pressure was studied. It was discovered that the d-electrons in the Sr-IV phase significantly contribute to the Fermi surface, a phenomenon closely related to the Van Hove singularity (VHS) near the saddle points. The increase in Tc of Sr under pressure is attributed to phonon softening and strong coupling resulting from the gradual overlap of VHS with the Fermi level, which is associated with the incomplete saturation of s–d electron transfer. Ultimately, the Tc of Sr reaches 17.65 K at 150 GPa, with a λ value of 1.26. This strong EPC is contributed by the interaction between d-electrons and medium-high-frequency phonons. This study extends new pathways for investigating the superconductivity of high-pressure phases of Sr and provides new insights for the theoretical study of elemental superconductors. [ABSTRACT FROM AUTHOR]

A triarylamine-functionalized terpyridine ligand formed a highly coordinated complex with europium tris(β-diketonate), which displayed reversible ''ON-OFF'' luminescence switching coupled with a ligand redox process of triarylamine/triarylaminium cations., (This journal is © The Royal Society of Chemistry 2012)

A simple method for specific colorimetric sensing of aqueous mercury(II) has been developed by using a gold nanoparticle supported by triethylene glycol ligand (Au:S-EG(3)). The unusual kinetic behavior of the sensing process of Hg(2+) and the TEM images of the Au core, as well as the electrospray ionization mass spectroscopic analysis of the analyte solution, have led us to propose a new color changing mechanism that involves ligand abstraction from a gold surface by Hg(2+).

An exceptional example of multiple C–H⋯π(alkyne) contacts has been discovered in the crystal packing of the syn-diastereomeric conformer of 1,2-di(7′-methoxynaphth-1′-yl)-3,6-di(4′′-n-propylphenylethynyl)benzene (syn-1). In contrast, the chiral crystal of anti-1, derived from a racemic mixture via spontaneous resolution, predominantly features conventional C–H⋯π(arene) contacts. The comprehensive analysis of the C–H⋯π contacts in the crystal packing of 1 was conducted using Hirshfeld surface, van der Waals crust, and quantum theory of atoms-in-molecules (QTAIM) methods. The electron density at the bond critical points (σBCP) along the bond path in the C–H⋯π contacts exhibits a moderate correlation with the dimensionless penetration index (pCH). This finding unveils the essentially identical characteristics of the C–H⋯π interactions, irrespective of the sp- and sp2-carbons. The C–H⋯π(alkyne) contacts are almost statistically populated within the range of pure van der Waals interactions, whereas the C–H⋯π(arene) contact exhibits a slight deviation from the criteria. The crystal structure of syn-1 exemplifies an exceptional formation of multiple C–H⋯π(alkyne) contacts, contrasting with the generally rare occurrence of C–H⋯π(alkyne) interactions. [ABSTRACT FROM AUTHOR]

New mixed metal clusters with M19 metal frameworks have been synthesized by NaBH4 reduction of Au(NO3)(PMe2Ph) together with AgNO3 in ethanol. Single crystal X-ray diffraction has revealed Au12Ag7 and Au17Ag2 metal skeletons for these clusters, which are best described in terms of bicapped pentagonal antiprismatic cages with a staggered-staggered M(5) ring configuration. These clusters connect the missing link between M13 icosahedral and M25 biicosahedral clusters providing a view of the cluster growth process. A TEM image of this cluster has been observed, which has clearly demonstrated single-sized nano-particles of less than 1.0 nm.

Thermolysis of gold(I) thiolate complex, [C14H29(CH3)3N][Au(SC12H25)2], at 180 degrees C for 5 h under an N2 atmosphere produces novel gold nanoparticles passivated by alkyl groups derived from the precursor complex, the TEM image of which shows spherical particles with average diameter 26 nm.

Prussian blue analogue (PBA) based aqueous batteries assembled with organic materials are an up-and-coming and promising technology for less demanding applications. By avoiding scarce, costly, and toxic transition metals (e.g. Ni/Co/Cu), the technology may become low-cost, more environmentally benign, and also safer than today's alternatives. Here we rely on a PBA using the FeII/III redox pair together with aqueous low-to-medium concentrated fluorine/perchlorate-free electrolytes and organic materials to create long-term performant cells. The performance in terms of capacity, coulombic efficiency, cell voltage, and energy density are all comparable with previously reported aqueous PBA-based batteries, while the cycling performance is substantially improved by practically implementing Le Chatelier's principle. Additionally, we investigate the redox process(es) and find no proof for any proton storage, but that both Na+ and Mg2+ likely are active, why we classify it as an aqueous Na/Mg-ion battery. [ABSTRACT FROM AUTHOR]

The accumulation of amyloid fibrils is characteristic of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease. Detecting these fibrils with fluorescent or radiolabelled ligands is one strategy for diagnosing and better understanding these diseases. A vast number of amyloid-binding ligands have been reported in the literature as a result. To obtain a better understanding of how amyloid ligands bind, we have compiled a database of 3457 experimental dissociation constants for 2076 unique amyloid-binding ligands. These ligands target Aβ, tau, or αSyn fibrils, as well as relevant biological samples including AD brain homogenates. From this database significant variation in the reported dissociation constants of ligands was found, possibly due to differences in the morphology of the fibrils being studied. Ligands were also found to bind to Aβ(1–40) and Aβ(1–42) fibrils with similar affinities, whereas a greater difference was found for binding to Aβ and tau or αSyn fibrils. Next, the binding of ligands to fibrils was shown to be largely limited by the hydrophobic effect. Some Aβ ligands do not fit into this hydrophobicity-limited model, suggesting that polar interactions can play an important role when binding to this target. Finally several binding site models were outlined for amyloid fibrils that describe what ligands target what binding sites. These models provide a foundation for interpreting and designing site-specific binding assays. [ABSTRACT FROM AUTHOR]

This study investigates the electrochemical modulation of luminescence color, i.e., electrofluorochromism, of an Eu complex in a polyether solvent. The electrofluorochromic (EFC) reaction of the Eu complex occurred via a reversible redox reaction between Eu3+ and Eu2+. Initially, the intrinsically stable Eu3+ complex showed intense red photoluminescence (PL) induced by f–f transitions. After the electrochemical reduction of Eu3+ to Eu2+, broad blue PL was observed attributed to the d–f transitions in the Eu2+ complex. This distinct blue luminescence from the Eu2+ complex was attributed to the effective stabilization of the Eu2+ state by the polyether solvent. The dynamic EFC reaction that changes the valence state of the Eu ion can be potentially applied to novel chemical sensors, security devices, and display devices. [ABSTRACT FROM AUTHOR]

Beta zeolites have been widely used in acid-catalyzed reactions because of their excellent properties. An in-depth study of the position, quantity, and distribution of beta zeolites substituted by Al is significant to understand the catalytic performance of the active site of zeolite catalysts. The distribution of Al in H-BEA and the structure of silanol nests in dealuminated BEA at different Si/Al ratios and synthesis temperatures were studied by the DFT method. T1, T2, T7, and T9 sites were chosen to be simulated. The synthesis temperature can change the distribution of Al and the proportion of T sites at different Si/Al ratios. The proportion of T7 and T9 is more than 70% at different Si/Al ratios of H-BEA and decreases with the synthesis temperature. T1 and T2 sites begin to appear when Si/Al < 20 and the proportion of T1 and T2 sites is less than 20%. When Si/Al < 8, the substitution energy of the AlSiAl structure, which has Si(2Al, 2Si) species, is obviously lower than that of the normal structure, which indicates that the Al–O–Si–O–Al species will appear in H-BEA. The Al(T7)Si(T5)Al(T9)Si(T5)Al(T7) and Al(T1)Si(T1)Al(T9) groups can not only stabilize H-BEA but also play an essential role in the formation of Si(2Al, 2Si) species. For dealuminated BEA zeolites, the silanol nest forms four hydrogen bonds through four silanols. The orientation of silanol groups in the silanol nest formed after dealumination at different T sites is different. The T7 and T9 sites in H-BEA are more likely to undergo dealumination. By contrast, the dealumination of the T1 and T2 sites is a challenge. [ABSTRACT FROM AUTHOR]

The pressure-induced amorphization (PIA) of ice and clathrate hydrates occurs at temperatures significantly below their melting and decomposition points. The PIA of type I clathrate hydrates containing methane and ethane as guest molecules was investigated using Raman and infrared (IR) spectroscopy. With isothermal compression at 100 K, methane hydrate (MH) underwent PIA at 2–3.5 GPa, whereas ethane hydrate (EH) underwent PIA at 4.0–5.5 GPa. The type I clathrate structure consists of small (512) and large (51262) cages. The Raman results revealed that the collapsed small and large cages in the amorphous forms of MH and EH were not distinguishable. The collapsed cages, including the methane and ethane molecules, were similar to the small and large cages, respectively. Their water networks were folded or expanded during the PIA process so that the cavity sizes of the collapsed cages were compatible with those of the guest molecules. Peaks in the IR spectra of crystalline MH assignable to the ro-vibrational transition of methane in large cages were observed in the C–H stretching wavenumber region below 40 K. The ro-vibrational IR band disappeared after amorphization, suggesting that the rotational motion of the methane molecule in the large cage was frozen by the collapse, as reported in previous dielectric spectroscopic and simulation studies. This study contributes to a better understanding of the changes in the local structure around guest molecules during PIA and the dynamics of the guest molecules. [ABSTRACT FROM AUTHOR]

In this feature article, an overview of the chemistry of pyramidanes, as a novel class of main group element clusters, is given. A general introduction sets the scene, briefly presenting the non-classical pyramidal geometry of tetracoordinate carbon, as opposed to the classical tetrahedral configuration. Pyramidanes, as the simplest organic compounds possessing a pyramidal carbon atom, are then discussed from both computational and experimental viewpoints, to show the theoretical predictions on the stability and thus the feasibility of pyramidanes has finally culminated in the isolation of the first stable representatives of the pyramidane family featuring heavy main group elements at the apex of the square pyramid. Synthetic strategies towards pyramidanes, as well as their peculiar structural features, non-classical bonding situations, and specific reactivity, are presented and discussed in this review. [ABSTRACT FROM AUTHOR]

Mid-infrared microspectroscopy is a non-invasive tool for identifying the molecular structure and chemical composition at the scale of the probe, i.e. at the scale of the beam. Consequently, investigating small objects or domains (commensurable to the wavelength) requires high-resolution measurements, even down to the diffraction limit. Herein, different protocols and machines allowing high-resolution measurements in transmission mode (aperture size (i.e., beam size) from 15 × 15 μm to 3 × 3 μm) are tested using the same sample. The model sample is a closed cavity containing a water–air assemblage buried in a quartz fragment (fluid inclusion). The spectral range covers the water stretching band (3000–3800 cm−1), whose variations are followed as a function of the distance to the cavity wall. The experiments compare the performance of one focal plane array (FPA) detector associated with a Globar source with respect to a single-element mercury cadmium telluride (MCT) detector associated with a supercontinuum laser (SCL) or a synchrotron radiation source (SRS). This work also outlines the importance of post-experimental data processing, including interference fringe removal and Mie scattering correction, to ensure that the observed spectral signatures are not related to optical aberrations. We show that the SCL and the SRS-based setups detect specific spectral features along the quartz boundary (solid surface), invisible to the FPA imaging microscope. Additionally, the broadband SCL thus has the potential to substitute at the laboratory scale the SRS for conducting diffraction-limited high-resolution measurements. [ABSTRACT FROM AUTHOR]

Two adamantane-bearing macrocycles (1, 2) with pyromellitic diimide or naphthalenediimide units were utilized as host molecules to elucidate the intermolecular interactions between the oxygen atoms of guest ketones and the electron-deficient π-surface of aromatic diimide moieties. Crystallization of 1 in acetone gave crystal 1a with acetone. Guest acetone molecules were captured within the cavity of 1, where C＝O⋯π contacts between the oxygen atoms of acetone and the pyromellitic diimide units were observed. From the molecular electrostatic potentials on the Hirshfeld surfaces, it was clarified that lone pair⋯π interactions predominantly contributed to the C＝O⋯π contacts. Crystallization of a dichloromethane solution of macrocycles and other ketones furnished crystals 1b with cyclopentanone, 1c with 3-oxetanone and dichloromethane, and 2a with cyclopentanone. The orientation of the carbonyl groups of ketones within the macrocycles in crystals 1b and 2a was similar to that in crystal 1a, whereas 3-oxetanone was positioned on the exterior of 1 in crystal 1c. [ABSTRACT FROM AUTHOR]

Development of a mild, robust and metal-free catalytic approach for silyl transfer of silylboranes is critical for the advancement of modern organosilicon chemistry given their powerful capacity in the construction of C–Si bonds. Herein, we wish to disclose a visible light-induced organophotocatalytic strategy, where methanol association with boron atoms enables the photocatalytic generation of silyl radicals. Notably, the protocol is capable of accommodating a wide range of radial acceptors through slightly tuning the reaction conditions, which allows the formation of various types of C–Si bonds. The preparative power of the transformations has been further highlighted in a number of complex settings, including late-stage functionalization and radical cascade reactions. Furthermore, this technology could be extended to the construction of C–B, C–S and C–Sn bonds, thus offering a versatile platform for bond activation and connection of main group elements. The green aspect of the reaction has also been demonstrated by using Brij-30/water as a reaction solvent or sunlight as an alternative energy source. [ABSTRACT FROM AUTHOR]

The solvent of the oral liquid formulations of traditional Chinese medicine is mainly water, but the variation of the absorption band of water in the infrared (IR) spectrum was often ignored in previous studies. In this study, the FT-IR spectra of the oral solution for Xiao'er Xiaoji Zhike Oral Liquid (XXZOL) were collected and, using second order derivatives, the OH stretching vibrational band was decomposed into three Gaussian components, whose frequencies were related to the hydrogen bond distance and whose amplitudes were related to the amount of the three types of bound water, differing in structure. Three characteristic peaks at 3400 cm−1, 3200 cm−1 and 3050 cm−1 in the high-wavenumber region of FT-IR spectra of XXZOL were identified, and the dynamic mechanism of the change in its water structure was investigated by two-dimensional (2D) correlation analysis using temperature as a perturbation factor. The specificity of the three characteristic peaks was also validated with pure water and different XXZOL samples. In conclusion, this research has identified three peaks which could be attributed to XXZOL water species and the dynamics of the three peaks were elucidated. It provides a novel idea for the examination of the state of water and solvation dynamic of the oral liquid system of traditional Chinese medicine in the future. [ABSTRACT FROM AUTHOR]

The surface melting of macro-crystals and melting of nano-crystals for Al, Cu and Ag pure components are modeled in comparison with literature data. The relevant temperatures of surface premelting and melting are calculated. The corresponding temperature-dependent equilibrium thickness of the liquid melted layer is obtained as well, which tends to infinity when the temperature is at the bulk melting point. Furthermore, the size-dependent melting behaviors for Al, Cu and Ag are investigated and the corresponding critical size is determined using a home-made code. The melting point depression with particle size is also demonstrated in the present work. As illustrated in the size-dependent phase diagram, the temperatures of both the solidus and liquidus decrease and they merge with the decrease in the radius. [ABSTRACT FROM AUTHOR]

Chemical bond lengths and angles are characteristic structural parameters of a molecule. Similarly, the frequencies of the vibrational modes and the NMR chemical shifts are unique "chemical fingerprints" specific to a compound. These are the basic parameters describing newly obtained compounds and enabling their identification. Intramolecular hydrogen bonding significantly influences the physicochemical properties of macrocyclic compounds with a porphyrin-like structure. This work presents the verification for correlations between geometric and spectroscopic parameters related to hydrogen bonds in this type of macrocyclic compounds. In particular, such relationships were investigated for a large group of porphyrin, porphycene, and dibenzotetraaza[14]annulene derivatives and a group of other macrocycles with similar structure. A very strong linear correlation was found only between the vibrational frequencies of the NH groups involved in a hydrogen bond and the length of this bond, which applied to all macrocyclic compounds of this type. Several other relationships were found between spectroscopic (IR, Raman, NMR) and geometric (X-ray) parameters, highlighting differences and similarities between different families of macrocycles. Apart from providing a better understanding of the nature of hydrogen bonds and their characteristics in porphyrin-like macrocyclic compounds, these relationships will facilitate the identification of new macrocycles and the extrapolation of their spectroscopic properties. [ABSTRACT FROM AUTHOR]

Supramolecular gels with aggregation-induced emission (AIE) are recognized as excellent chemosensors. The combination of gelators and metal ions gives rise to a synergistic effect, which induces functional behaviors of anions and amino acids. The 3,4,5-tris(hexadecyl) benzoyl hydrazine functionalized naphthalimide gelator (G) with multi self-assembly driving forces was devised and synthesized. G could self-assemble into a stable supramolecular organogel (OG) in cyclohexanol solution with blue-green AIE. Notably, the OG could coordinate with different metal ions through coordination bonds to form a series of metallogels (OGMs). In addition, these metallogels (OGMs) could selectively sense various anions (I−, N3−, CN−) and amino acids (L-Trp and L-His) via synergistic coordination interaction between target ions/amino acids and pre-assembling metal ions in OGMs. Therefore, a six-membered anion and amino acid sensor array based on supramolecular metallogels (OGMs) was successfully constructed. Moreover, anion/amino acid responsive films based on supramolecular metallogels (OGMs) were prepared, which could be used as fluorescence anti-counterfeiting and encryption materials. Therefore, the supramolecular metallogels will be of great application value in the detection of anions and amino acids and as smart materials. [ABSTRACT FROM AUTHOR]

Glaucoma, a ruinous group of eye diseases with progressive degeneration of the optic nerve and vision loss, is the leading cause of irreversible blindness. Accurate and timely diagnosis of glaucoma is critical to promote secondary prevention and early disease-modifying therapies. Reliable, cheap, and rapid tests for measuring disease activities are highly required. Brain-derived neurotrophic factor (BDNF) plays an important role in maintaining the function and survival of the central nervous system. Decreased BDNF levels in tear fluid can be seen in glaucoma patients, which indicates that BDNF can be regarded as a novel biomarker for glaucoma. Conventional ELISA is the standard method to measure the BDNF level, but the multi-step operation and strict storage conditions limit its usage in point-of-care settings. Herein, a one-step and a portable glaucoma detection method was developed based on the lateral flow assay (LFA) to quantify the BDNF concentration in artificial tear fluids. The results of the LFA were analyzed by using a portable and low-cost system consisting of a smartphone camera and a dark readout box fabricated by 3D printing. The concentration of BDNF was quantified by analyzing the colorimetric intensity of the test line and the control line. This assay yields reliable quantitative results from 25 to 300 pg mL−1 with an experimental detection limit of 14.12 pg mL−1. The LFA shows a high selectivity for BDNF and high stability in different pH environments. It can be readily adapted for sensitive and quantitative testing of BDNF in a point-of-care setting. The BDNF LFA strip shows it has great potential to be used in early glaucoma detection. [ABSTRACT FROM AUTHOR]

A new dimethyl(phenyl)silylborane having a naphthalene-1,8-diaminato (dan) substituent on the boron center, PhMe2Si–B(dan), was synthesized. Owing to the diminished boron Lewis acidity, it is highly stable toward air. Synthetic application of the silylborane to catalytic silylboration and silylation of alkynes is also described. [ABSTRACT FROM AUTHOR]

Scandium (Sc) is the lightest non-main-group element and transforms to a host–guest (H–G) incommensurate structure under gigapascal (GPa) pressures. While the host structure is stable over a wide pressure range, the guest structure may exist in multiple forms, featuring different incommensurate ratios, and mixing up to generate long-range "disordered" guest structures. Here, we employed the recently developed global neural network (g-NN) potential and the stochastic surface walking (SSW) global optimization algorithm to explore the global potential energy surface of Sc under various pressures. We probe the global minima structure in a system made of hundreds of atoms and revealed that the solid-phase transition between Sc-I and H-G Sc-II phases is fully reconstructive in nature. Above 62.5 GPa, the pressure will further destabilize the face-centered tetragonal (fct, Sc-IIa) guest structure to a body-centered tetragonal phase (bct, Sc-IIb), while sustaining the host structure. The structural transition mechanism of this work will shed light on the nature of the complex H–G structural modifications in compressed metals. [ABSTRACT FROM AUTHOR]

Predicting behaviour of hydrogen bonds with varying temperature, in particular-correlating donor–acceptor distances in the O–HO hydrogen bonds with the frequencies of O–H stretching vibrations is important for understanding dynamics of biomolecules and phase transitions in crystals. A commonly used correlation suggested earlier in the literature is based on statistical analysis of different compounds [A. Novak, Structure and Bonding, 1974, 18, 177; K. Nakamoto, M. Margoshes, R. E. Rundle, J. Am. Chem. Soc., 1955, 77, 6480]. The present study is a rare example when correlations between geometry and energy parameters have been found for selected individual hydrogen bonds in the same crystalline compound at multiple temperatures. The properties of several types of O–HO hydrogen bonds in bis(dl-serinium) oxalate dihydrate and dl-alaninium semi-oxalate monohydrate have been studied by a combination of variable-temperature single-crystal X-ray diffraction and polarized Raman spectroscopy. The changes in the hydrogen bonds geometry could be compared with the changes of the corresponding spectral modes. The correlation suggested by Novak is roughly followed, better for medium and weak, than for short hydrogen bonds. Fine details of spectral changes differ for individual bonds. The way how H-bonds are affected by cooling depends on their environment in the crystal structure. Short O–HO hydrogen bonds in bis(dl-serinium) oxalate dihydrate expand or remain almost unchanged on cooling, whereas in dl-alaninium semi-oxalate monohydrate all strong H-bonds are compressed under these conditions. The distortion of individual hydrogen bonds on temperature variations is correlated with the anisotropy of lattice strain. [ABSTRACT FROM AUTHOR]

The structural changes of Fe3O4 nanoparticle electrodes in Li ion batteries during charging–discharging cycles have been investigated using in situ X-ray absorption spectroscopy (XAS). Chemometric methods viz., Principal Component Analysis (PCA) and Multivariate Curve Resolution-Alternate Least Square (MCR-ALS) have been used for analysis of the in situ XANES data during the charge–discharge cycle, which help to identify the various species formed during the lithiation–delithiation of Fe3O4. The concentration variation of the different species has also been determined and the detailed intercalation–conversion mechanism of the Fe3O4 electrodes during the first discharge has been established. Subsequently, the first charge and second discharge cycles were also studied to apprehend the difference in redox reaction between the first discharge and subsequent cycles. The above studies clearly identify the four species involved in the whole intercalation–conversion process of Fe3O4 electrode of a Li ion battery and also indicate the irreversibility of the conversion reaction in subsequent cycles which may be one of the reasons for capacity fading of these electrodes. The above results have also been corroborated with density functional theory (DFT)based ab inito calculations. [ABSTRACT FROM AUTHOR]

Thermoelectric (TE) materials are promising candidates for solving today's energy problem owing to their ability to directly convert waste heat into electricity via the Seebeck effect. One of the most efficient TE materials known is Zn4Sb3. To understand its high efficiency, a novel composite crystal structure model for β- and γ-phases of Zn4Sb3 is constructed using a (3 + 1)-dimensional ((3 + 1)-D) superspace group approach. This (3 + 1)-D model is expressed as [Zn3+δSb][Sb]p with the superspace group of R3¯m(00γ)0s. The [Zn3+δSb] and [Sb] subsystems have same a- and b-axis lengths but a different c-axis length. The (3 + 1)-D model contains four atomic sites: a Zn(1) normal site, an interstitial Zn (Zni) site and an Sb(1) site in the [Zn3+δSb] subsystem and an Sb(2) site in the [Sb] subsystem, which is different from a conventional 3D model containing additional Zni sites. The crystal structures of β- and γ-Zn4Sb3 are investigated via powder and synchrotron X-ray diffraction (XRD) measurements. The XRD patterns are well analysed by the (3 + 1)-D model. The occupancies of Zn(1), Sb(1) and Sb(2) sites are 100%, whereas the Zni occupancy changes depending on the heating time during the preparation of β-Zn4Sb3. Moreover, electronic density of states (DOS) of β-Zn4Sb3 with and without Zni is calculated based on the (3 + 1)-D model, demonstrating a close relationship between the DOS and the Zni occupancy. The calculated TE properties, such as Seebeck coefficient, electrical conductivity and power factor, also depend on the Zni occupancy. [ABSTRACT FROM AUTHOR]