The use of pincer ligands to access non‐VSEPR geometries at main‐group centers is an emerging strategy for eliciting new stoichiometric and catalytic reactivity. As part of this effort, several ...different tridentate trianionic substituents have to date been employed at a range of different central elements, providing a patchwork dataset that precludes rigorous structure–function correlation. An analysis of periodic trends in structure (solid, solution, and computation), bonding, and reactivity based on systematic variation of the central element (P, As, Sb, or Bi) with retention of a single tridentate triamide substituent is reported herein. In this homologous series, the central element can adopt either a bent or planar geometry. The tendency to adopt planar geometries increases descending the group with the phosphorus triamide (1) and its arsenic congener (2) exhibiting bent conformations, and the antimony (3) and bismuth (4) analogues exhibiting a predominantly planar structure in solution. This trend has been rationalized using an energy decomposition analysis. A rare phase‐dependent dynamic covalent dimerization was observed for 3 and the associated thermodynamic parameters were established quantitatively. Planar geometries were found to engender lower LUMO energies and smaller band gaps than bent ones, resulting in different reactivity patterns. These results provide a benchmark dataset to guide further research in this rapidly emerging area.
A longitudinal study of strained p‐block triamides: A comprehensive analysis of periodic trends in structure, bonding, and reactivity for geometry constrained triamide complexes of P, As, Sb, and Bi is reported. In this homologous series, the central element can adopt either a bent or planar geometry and the preferred orientation in the solid and solution phases (as well as computationally) have been mapped. Additionally, the influence of geometry on reactivity has been elucidated.
Tetraarylmethanes and adamantanes are important rigid covalent connectors that play a four‐way scaffolding role in molecular and materials chemistry. We report the synthesis of a new tetravalent ...phosphaza‐adamantane cage, (PNSiMe3)4(NMe)6 (2), that shows high thermal, air, and redox stability due to its geometry. It nevertheless participates in covalent four‐fold functionalization reactions along its periphery. The combination of a robust core and reactive corona makes 2 a convenient inorganic scaffold upon which tetrahedral molecular and macromolecular chemistry can be constructed. This potential is demonstrated by the synthesis of a tetrakis(bis(phosphine)iminium) ion (in compound 3) and the first all P/N poly(phosphazene) network (5).
The synthesis of a new air‐stable and thermally robust tetrahedral tetravalent inorganic cage, (PNSiMe3)4(NMe)6 has been achieved. This cage allows four‐fold functionalization reactions on its periphery to give unprecedented molecular and macromolecular constructs. This utility is shown by the synthesis of a tetrakis(bis(phosphine)iminium) ion and the first all P/N polyphazene network material.
Amorphous Quantum Nanomaterials Kohle, Ferdinand F. E.; Hinckley, Joshua A.; Li, Songying ...
Advanced materials (Weinheim),
February 1, 2019, Letnik:
31, Številka:
5
Journal Article
Recenzirano
Odprti dostop
In quantum materials, macroscopic behavior is governed in nontrivial ways by quantum phenomena. This is usually achieved by exquisite control over atomic positions in crystalline solids. Here, it is ...demonstrated that the use of disordered glassy materials provides unique opportunities to tailor quantum material properties. By borrowing ideas from single‐molecule spectroscopy, single delocalized π‐electron dye systems are isolated in relatively rigid ultrasmall (<10 nm diameter) amorphous silica nanoparticles. It is demonstrated that chemically tuning the local amorphous silica environment around the dye over a range of compositions enables exquisite control over dye quantum behavior, leading to efficient probes for photodynamic therapy (PDT) and stochastic optical reconstruction microscopy (STORM). The results suggest that efficient fine‐tuning of light‐induced quantum behavior mediated via effects like spin‐orbit coupling can be effectively achieved by systematically varying averaged local environments in glassy amorphous materials as opposed to tailoring well‐defined neighboring atomic lattice positions in crystalline solids. The resulting nanoprobes exhibit features proven to enable clinical translation.
Chemically tuning the local amorphous silica environment in dye‐encapsulating nanoparticles (Cornell dots) over a range of compositions, in contrast to lattice parameters or symmetry of crystalline solids, can be used to exquisitely control the quantum behavior of dye π‐electron systems, leading to ultraefficient probes for photodynamic therapy and super‐resolution optical microscopy.
Catenation is common for the light main‐group elements whereas it is rare for the heavy elements. Herein, we report the first example of a neutral molecule containing a Bi4 chain. It is prepared in a ...one‐step reaction between bismuth trichloride and bis(diisopropylphosphino)amine in methanol suspension. The same reaction carried out in dichloromethane gives quite different products. All products have been characterized spectroscopically and using single‐crystal X‐ray analysis.
Get coordinated! The reaction between bismuth trichloride and bis(diisopropylphosphino)amine in methanol suspension results in the formation of a neutral molecule exhibiting bismuth catenation (see figure).
Ultrasmall fluorescent silica nanoparticles (SNPs) and core–shell SNPs surface functionalized with polyethylene glycol (PEG), specific surface ligands, and overall SNP size in the regime below 10 nm ...are of rapidly increasing interest for clinical applications, because of their favorable biodistribution and safety profiles. Here, we present an aqueous synthesis methodology for the preparation of narrowly size-dispersed SNPs and core–shell SNPs with size control below 1 nm, i.e., at the level of a single atomic layer. Different types of fluorophores, including near-infrared (NIR) emitters, can be covalently encapsulated. Brightness can be enhanced via addition of extra silica shells. This methodology further enables synthesis of <10 nm sized fluorescent core and core–shell SNPs with previously unknown compositions. In particular, the addition of an aluminum sol gel precursor leads to fluorescent aluminosilicate nanoparticles (ASNPs) and core–shell ASNPs. Encapsulation efficiency and brightness of highly negatively charged NIR fluorophores is enhanced, relative to the corresponding SNPs without aluminum. Resulting particles show quantum yields of ∼0.8, i.e., starting to approach the theoretical brightness limit. All particles can be PEGylated providing steric stability. Finally, heterobifunctional PEGs can be employed to introduce ligands onto the PEGylated particle surface of fluorescent SNPs, core–shell SNPS, and their aluminum-containing analogues, producing ligand-functionalized <10 nm NIR fluorescent nanoprobes. In order to distinguish these water-based-synthesis-derived materials from the earlier alcohol-based modified Stöber process derived fluorescent core–shell SNPs referred to as Cornell dots or C dots, the SNPs and ASNPs described here and synthesized in water will be referred to as Cornell prime dots or C′ dots and AlC′ dots. These organic–inorganic hybrid nanomaterials may find applications in nanomedicine, including cancer diagnostics and therapy (theranostics).
In the present work, our aim is to decipher the cationic ordering in the octahedral and tetrahedral sheets of two Al‐rich synthetic materials, namely, phlogopites of nominal composition ...K(Mg3‐xAlx)Al1+xSi3‐xO10(OH)yF2‐y and lepidolites in the system trilithionite–polylithionite with composition K (LixAl3‐x)Al4‐2xSi2xO10(OH)yF2‐y, by directly probing the aluminium distribution through 27Al and 17O magic‐angle spinning, multiple‐quantum magic‐angle spinning, and 27Al‐27Al double‐quantum single‐quantum nuclear magnetic resonance (NMR) experiments. Notably, 27Al‐27Al double‐quantum single‐quantum magic‐angle spinning NMR spectra, recorded at 9.34 and/or 20.00 T, show the spatial proximity or avoidance of the Al species inside or between the sheets. In both studied minerals, the ensemble of NMR data suggests a preference for 4Al in the tetrahedral sheet to occupy position close to the 6Al of the octahedral sheets.
27Al and 17O MAS and MQMAS along with 27Al‐27Al DQ‐SQ MAS NMR experiments are used to decipher the aluminium preferential ordering in phlogopite and lepidolite synthetic minerals.
Mesoporous silica nanoparticles (MSNs) have recently attracted a lot of interest for future nanotheranostic applications because of their large surface-area and high biocompatibility. However, ...studies to date of MSNs are confined to >10 nm particle sizes which may result in unfavorable biodistribution characteristics for in vivo experiments and hence limit their clinical applications. Here we provide a full account of a synthesis approach to ultrasmall sub-10 nm mesoporous silica nanoparticles with narrow size distributions and homogeneous porous particle morphology. Key features enabling this structure control are (i) fast hydrolysis, (ii) slow condensation, and (iii) capping of particle growth by addition of a PEG-silane at different time-points of the synthesis. Variation of synthesis conditions including monomer/catalyst concentrations, temperature, and time-point of PEG-silane addition leads to synthesis condition-particle structure correlations as mapped out by a combination of results from data analysis of dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. Results establish precise control over average particle diameter from 6 to 15 nm with increments below 1 nm. Solid state nuclear magnetic resonance (NMR) measurements, zeta-potential measurements, and thermogravimetric analysis (TGA) were conducted to reveal details of the particle surface structure. Long-term particle stability tests in deionized (DI) water and phosphate buffered saline (PBS) 1X buffer solution were performed using DLS demonstrating that the PEGylated particles are stable in physiological environments for months. Fluorescent single pore silica nanoparticles (mC dots) encapsulating blue (DEAC) and green (TMR) dyes were synthesized and characterized by a combination of DLS, TEM, static optical spectroscopy, and fluorescence correlation spectroscopy (FCS) establishing probes for multicolor fluorescence imaging applications. The ultraprecise particle size control demonstrated here in particular for sizes around and below 10 nm may render these particles an interesting subject for further fundamental studies of porous silica particle formation mechanisms as well as for sensing, drug delivery, and theranostic applications.
An extended π‐system containing two 3cumulene fragments separated by a p‐carboquinoid and stabilized by two capping N‐heterocyclic carbenes (NHCs) has been prepared. Mono‐ and bis(imidazolidinium ...ethynyl) cations have also been synthesized from the reaction of an NHC with phenylethynyl bromide or 1,4‐bis(bromoethynyl)benzene. Cyclic voltammetry coupled with synthetic and structural studies showed that the dication is readily reduced to a neutral, singlet bis‐1,4‐(3cumulene)‐p‐carboquinoid as a result of the π‐accepting properties of the capping NHCs.
Accumulating cumulenes: Two‐electron reduction of a bis(imidazolidinium ethynyl) dication derived from an N‐heterocyclic carbene (NHC) and 1,4‐bis(bromoethynyl)benzene gave the extended bis‐1,4‐(3cumulene)‐p‐carboquinoid 1 with no change in the overall distance between the NHC moieties. Cyclic voltammetry coupled with synthetic and structural studies showed that the π‐accepting properties of the capping NHCs may play a role in the reduction of the dication.
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