Organic Substituents Research Articles

PNP Ligands in Cobalt‐Mediated Activation and Functionalization of White Phosphorus

AbstractTransition‐metal mediated white phosphorus activation is of high interest as an ecological alternative to P4 chlorination pathway to the practically useful phosphorus products. Herein, we report a facile approach for P4 activation, transformation and subsequent functionalization using cobalt complexes bearing PNP ligands. The use of N,N‐bis(diphenylphosphino)amine as a ligand allows one to transform P4 tetrahedron into a zig‐zag chain with the formation of complex [Co(Ph2PNHP(Ph2)PPPPP(Ph2)NHPPh2)]BF4 (4). The presence of organic substituent at nitrogen atom in PNP ligand enables one to obtain complexes with η1‐coordinated P4 molecule, which indicates a crucial role of N−H bond in transformation of white phosphorus tetrahedron. Additionally, complex 4 can readily be functionalized by means of the reaction with Ph2PCl leading to the formation of a new complex bearing unique P9‐ligand. The obtained results provide opportunities for facile construction of new polyphosphorus ligands in the coordination sphere of transition metal complexes.

The role of organic and inorganic substituents of roxarsone determines its binding behavior and mechanisms onto nano-ferrihydrite colloidal particles

The retention and fate of Roxarsone (ROX) onto typical reactive soil minerals were crucial for evaluating its potential environmental risk. However, the behavior and molecular-level reaction mechanism of ROX and its substituents with iron (hydr)oxides remains unclear. Herein, the binding behavior of ROX on ferrihydrite (Fh) was investigated through batch experiments and in-situ ATR-FTIR techniques. Our results demonstrated that Fh is an effective geo-sorbent for the retention of ROX. The pseudo-second-order kinetic and the Langmuir model successfully described the sorption process. The driving force for the binding of ROX on Fh was ascribed to the chemical adsorption, and the rate-limiting step is simultaneously dominated by intraparticle and film diffusion. Isotherms results revealed that the sorption of ROX onto Fh appeared in uniformly distributed monolayer adsorption sites. The two-dimensional correlation spectroscopy and XPS results implied that the nitro, hydroxyl, and arsenate moiety of ROX molecules have participated in binding ROX onto Fh, signifying that the predominated mechanisms were attributed to the hydrogen bonding and surface complexation. Our results can help to better understand the ROX-mineral interactions at the molecular level and lay the foundation for exploring the degradation, transformation, and remediation technologies of ROX and structural analog pollutants in the environment.

Synthesis, Structure, and Bonding Analysis of Lewis Base and Lewis Acid/Base‐Stabilized Phosphanylgallanes

AbstractPhosphanylgallane with hydrogen and halogen substituents (RXGa−PHR, R=organic substituent, X=halogen/hydrogen) are regarded as putative suitable precursors for accessing Ga=P doubly bonded species. Herein, we report on the synthesis, structure, and bonding analysis of a series of Lewis base‐ and Lewis acid/base‐stabilized phosphanylgallane bearing P−H and Ga−Cl/H substitution. To avoid oligomerization, the treatment of IDip.GaCl3 and (IDip)GaH2Cl (IDip=1,3‐bis(2,6‐diisopropylphenyl) imidazole‐2‐ylidene) with LiPHR or LiPHR(BH3) (R=Ph, Tip, Mes, NiPr2, NCy2) affords the corresponding Lewis base and Lewis acid/base coordinated H,Cl‐functionalized monomeric phosphanylgallane, respectively. The structure of these derivatives were determined by spectroscopic and X‐ray crystallographic analyses. The observed Ga−P bond lengths are comparable to those previously reported phosphanylgallane analogues. The nature of the CIDip‐Ga coordination bond was assessed with Energy Decomposition Analysis, suggesting a relatively stable adduct. Reactions of the phosphanylgallane with Brønsted bases were investigated.

Reactive Solubilization of Heterometallic Clusters by Treatment of (TrBi3)2− Anions (Tr=Ga, In, Tl) with [Mn{N(SiMe3)2}2

AbstractLowering the charge of Zintl anions by (element‐)organic substituents allows their use as sources of (semi)metal nanostructures in common organic solvents, as realized for group 15 anions or Ge94− and Sn94−. We developed a new strategy for other anions, using low‐coordinate 3d metal complexes as electrophiles. [K(crypt‐222)]+ salts of (TrBi3)2− anions dissolved in situ in Et2O and/or THF when reacted with [Mn(hmds)2]. Work‐up afforded soluble [K(crypt‐222)]+ salts of [{(hmds)2Mn}2(TlBi3)]2− (in 1), [{(hmds)2Mn}2(Bi2)]2− (in 2), and [{(hmds)Mn}4(Bi2)2]2− (in 3) (crypt‐222=4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane; Tr=Ga, In, Tl; hmds=N(SiMe3)2), representing rare cases of Zintl clusters with open‐shell metal atoms. 1 comprises the first coordination compound of the (TlBi3)2− anion, 2 features a diamond‐shaped {Pn2M2} unit, and 3 is a mixed‐valent MnI/MnII compound. The uncommon electronic structures in 1–3 and magnetic coupling were studied by comprehensive DFT calculations.

Reactive Solubilization of Heterometallic Clusters by Treatment of (TrBi3 )2- Anions (Tr=Ga, In, Tl) with [Mn{N(SiMe3 )2 }2

Lowering the charge of Zintl anions by (element-)organic substituents allows their use as sources of (semi)metal nanostructures in common organic solvents, as realized for group 15 anions or Ge9 4- and Sn9 4- . We developed a new strategy for other anions, using low-coordinate 3d metal complexes as electrophiles. [K(crypt-222)]+ salts of (TrBi3 )2- anions dissolved in situ in Et2 O and/or THF when reacted with [Mn(hmds)2 ]. Work-up afforded soluble [K(crypt-222)]+ salts of [{(hmds)2 Mn}2 (TlBi3 )]2- (in 1), [{(hmds)2 Mn}2 (Bi2 )]2- (in 2), and [{(hmds)Mn}4 (Bi2 )2 ]2- (in 3) (crypt-222=4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane; Tr=Ga, In, Tl; hmds=N(SiMe3 )2 ), representing rare cases of Zintl clusters with open-shell metal atoms. 1 comprises the first coordination compound of the (TlBi3 )2- anion, 2 features a diamond-shaped {Pn2 M2 } unit, and 3 is a mixed-valent MnI /MnII compound. The uncommon electronic structures in 1-3 and magnetic coupling were studied by comprehensive DFT calculations.

A Web Tool for Calculating Substituent Descriptors Compatible with Hammett Sigma Constants**

AbstractThe electron‐donating and ‐accepting power of organic substituents is an important parameter affecting many properties of parent molecules, most notably their reactivity and pKa of ionisable groups. These substituent properties are described by Hammett σ constants obtained by measuring ionization constants of substituted benzoic acids. Although values of the Hammett σ constants have been measured for the most common functional groups, data for many important substituents are not available. In the present study, a method to calculate substituent descriptors compatible with the Hammett σ constants using quantum‐chemically derived parameters is described. On this basis, a free web tool allowing to calculate electronic and hydrophobic substituent descriptors is made available at https://bitly.com/getsigmas.

Towards Hexagonal Planar Nickel: A Dispersion‐Stabilised Tri‐Lithium Nickelate

AbstractAdvancing the understanding of lithum nickelate complexes, here we report a family of homoleptic organonickelate complexes obtained by reacting Ni(COD)2and lithium aryl‐acetylides in the presence of the bidentate donor TMEDA. These compounds represent rare examples of low‐valent transition‐metals supported solely by organolithium ligands. Whilst the solid‐state structures indicate a hexagonal planar geometry around Ni0with Ni−Li bonds, bonding analysis via QTAIM, NCI, NBO and ELI methods reveals that the Ni−Li interactions are repulsive in nature, characterising these complexes as tri‐coordinated. London dispersion forces between TMEDA and the organic substituents on nickel are found to play a crucial role in the stabilisation and thus isolation of these complexes. Preliminary reactivity studies demonstrate that the homoleptic lithium nickelates undergo stoichiometric cross‐coupling with PhI to give dinickel clusters containing both anionic acetylide and neutral alkyne ligands.

Towards Hexagonal Planar Nickel: A Dispersion-Stabilised Tri-Lithium Nickelate.

Advancing the understanding of lithum nickelate complexes, here we report a family of homoleptic organonickelate complexes obtained by reacting Ni(COD)2 and lithium aryl-acetylides in the presence of the bidentate donor TMEDA. These compounds represent rare examples of low-valent transition-metals supported solely by organolithium ligands. Whilst the solid-state structures indicate a hexagonal planar geometry around Ni0 with Ni-Li bonds, bonding analysis via QTAIM, NCI, NBO and ELI methods reveals that the Ni-Li interactions are repulsive in nature, characterising these complexes as tri-coordinated. London dispersion forces between TMEDA and the organic substituents on nickel are found to play a crucial role in the stabilisation and thus isolation of these complexes. Preliminary reactivity studies demonstrate that the homoleptic lithium nickelates undergo stoichiometric cross-coupling with PhI to give dinickel clusters containing both anionic acetylide and neutral alkyne ligands.

Manipulating White‐Light Generation in Adamantane‐Like Molecules via Functional Group Substitution

AbstractCertain adamantane (Ad)‐like molecules, either clusters of the type [(R′T)4E6] with inorganic cores (R′=cyclic/aromatic organic substituent; T=Si, Ge, Sn; E=S, Se, Te) or adamantane derivatives [(R′C)4(CH2)6]=AdR′4, display extreme nonlinear optical properties, which can lead to white‐light emission when exposed to near infrared light. While previous studies have established some requirements for these compounds to generate white light, the ability to tailor this effect remains elusive. Here we evaluate the impact of a variety of inorganic and organic compounds with Ad‐like cores as well as various functional groups on white‐light generation (WLG). We show that polarization and electron density localization are influenced by the type of the functional group R in [(R‐PhSn)4S6] in particular, according to DFT computations. While these groups do not have a large impact on the maximum emission wavelengths, they do significantly affect the laser power threshold for the occurrence of WLG.

Dynamic Supramolecular Polymers Based on Zinc Bis(diorganophospate)s: Synthesis, Structure and Transformations in Solid State and Solutions.

The synthesis, structure and some properties of coordination polymers composed of linear zinc bis(diorganophospate)s (ZnDOPs) with a general formula of Zn[O2P(OR)2]2 (where R = CH3, C2H5, n-C4H9, or 2-ethylhexyl group) are described. Hybrid (co)polymers obtained by different procedures were characterized by means of powder XRD, DSC, SEM, TGA coupled with mass spectrometry of the evolved gases and rheological measurements, as well as FTIR and NMR techniques. The morphology, thermal transformations and solubility of ZnDOPs strongly depend on the type of organic substituent in the O2P(OR)2 ligands and the thermal history of the sample. Because of this, one can obtain highly crystalline rods, semicrystalline powders, as well as rubbery materials exhibiting a second-order transition below −50 °C. Polymeric chains formed by ZnDOPs undergo a reversible dissociation in polar organic solvents (e.g., methanol, DMSO), which allows for easy modification of their composition and physicochemical properties via a simple exchange of diorganophosphate anions. Some of the ZnDOPs were investigated as the latent curing agents for epoxides. On the basis of rheological and DSC studies, it is evident that ZnDOPs catalyze very effectively the cross-linking process within the 130–160 °C temperature range.

Curvature-Selective Nanocrystal Surface Ligation Using Sterically-Encumbered Metal-Coordinating Ligands.

Organic ligands are critical in determining the physiochemical properties of inorganic nanocrystals. However, precise nanocrystal surface modification is extremely difficult to achieve. Most research focuses on finding ligands that fully passivate the nanocrystal surface, with an emphasis on the supramolecular structure generated by the ligand shell. Inspired by molecular metal-coordination complexes, we devised an approach based on ligand anchoring groups that are flanked by encumbering organic substituents and are chemoselective for binding to nanocrystal corner, edge, and facet sites. Through experiment and theory, we affirmed that the surface-ligand steric pressures generated by these organic substituents are significant enough to impede binding to regions of low nanocurvature, such as nanocrystal facets, and to promote binding to regions of high curvature such as nanocrystal edges.

Biomimetic and osteogenic natural HAP coated three dimensional implant for orthopaedic application

The excellent biocompatible and osteogenesis ability of multifunctional three-dimensional (3D) polymeric scaffolds have a vital role in bone regeneration application. Our prime focus of the investigation is the synthesis of snail shell-derived hydroxyapatite coated poly[bis(carboxyphenoxy)phosphazene] (PCPP)/poly(ε-caprolactone) (PCL) 3D scaffold. Snail shells are utilized for hydroxyapatite (HAP) synthesis via a modified chemical precipitation method. The interconnected PCPP/PCL polymeric scaffold was fabricated by the conventional solvent-casting/particulate-leaching method. Bioceramic HAP was further coated on the scaffold by the dip-coating technique. The obtained natural HAP from Turritella duplicata has minerals and organic substituents which are essential for biomedical application. HAP reinforcement significantly increases the mechanical property, compressive strength, and porosity of the scaffolds. The SEM image depicted the homogenous dispersion of HAP over the scaffold surface. Mechanical studies of the 3D polymeric scaffold at the 2% TSS-HAP content demonstrated a significant increase in compressive strength with desired porous structure. It showed increasing compressive strength from 1.52 MPa to 2.18 MPa and porosity of 82.26% to 76.18%. Snail shell HAP grafted polymeric scaffold shows mineralization with the formation of bone-like apatite. The HAP grafted bioceramic/polymeric scaffold surface helps in the attachment and proliferation of MG-63 cells. It also explored the biocompatible property and antibacterial against gram-positive/gram-negative bacteria. Overall, the fabricated 3D implant has improved mechanical strength, optimum pore size, and interconnected structure, which helps in mineralization and cancellous bone tissue engineering applications.

Cross-Linked Luminescent Polymers Based on β-Diketone-Modified Polysiloxanes and Organoeuropiumsiloxanes.

Nowadays, luminescent materials attract wide attention due to their valuable characteristics and broad area of potential application. Luminescent silicone-based polymers possess unique properties, such as flexibility, hydrophobicity, thermal and chemical stabilities, etc., which allow them to be utilized in various fields, such as optoelectronics, solid-state lasers, luminescent solar concentrators, sensors, and others. In the present work, a metal-ligand interaction approach was applied to obtain new cross-linked luminescent polymers based on multiligand polysiloxanes with grafted β-diketone fragments and organoeuropiumsiloxanes containing various organic substituents. Organoeuropiumsiloxanes were utilized as a source of Eu3+ ions due to their compatibility with the silicon matrix. All synthesized polymers were fully characterized and their physicochemical, mechanical, self-healing, optical, and thermal properties were studied.

Local Structure of Amorphous Organotin Sulfide Clusters by Low‐Energy X‐Ray Absorption Fine Structure

The local structure of four amorphous organotin sulfide compounds exhibiting nonlinear optical (NLO) properties is investigated by low‐energy X‐ray absorption spectroscopy (XANES and EXAFS). The basic structural motif of a heteroadamantane cluster with different organic substituents is confirmed by the experiments and by comparison with computer simulations of the near‐edge structure. Essential information is obtained on a special role of the nonaromatic but electron‐rich cyclopentadienyl substituents, which are able to affect the structure of the heteroadamantane cluster core. The EXAFS fits also indicate a structural distinction between two groups within these compounds, which exhibit fundamentally different NLO responses: compounds that show a second harmonic generation can be described well using the single‐molecule approach, whereas the compounds exhibiting the generation of a supercontinuum manifest additional structural contributions.

Recent Progress on Designable Hybrids with Stimuli-Responsive Optical Properties Originating from Molecular Assembly Concerning Polyhedral Oligomeric Silsesquioxane.

In this review, we describe recent progress on stimuli-responsive hybrid materials based on polyhedral oligomeric silsesquioxane (POSS) and their applications as a chemical sensor. In particular, we explain the unique functions originating from molecular assembly concerning POSS-containing soft materials mainly from our studies. POSS has an inorganic cubic core composed of silicon-oxygen (Si-O) bonds and organic substituents at each vertex. Owing to intrinsic properties of POSS, such as high thermal stability, rigidity, and low chemical reactivity, various robust hybrid materials have been developed. From the numerous numbers of POSS hybrids, we herein focus on the environment-sensitive optical materials in which molecular assembly of POSS itself and functional units connected to POSS should be a key factor for expressing material properties. We also explain the mechanisms of chemical sensors originating from these stimuli-responsive optical properties. Stimuli-responsive excimer emission and pollutant detectors, nanoplastic sensors with the water-dispersive POSS networks, trans fatty acid sensors, turn-on luminescent sensors for aerobic condition and fluoride anion sensors are described. We also mention the mechanochromic polyurethane hybrids and the thermally-durable mechanochromic luminescent materials. The roles of the unique optical properties from soft materials composed of rigid POSS, which doesn't have significant light-absorption and emission properties in the visible region, are surveyed.

Key Features of TEMPO-Containing Polymers for Energy Storage and Catalytic Systems

The need for environmentally benign portable energy storage drives research on organic batteries and catalytic systems. These systems are a promising replacement for commonly used energy storage devices that rely on limited resources such as lithium and rare earth metals. The redox-active TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl) fragment is a popular component of organic systems, as its benefits include remarkable electrochemical performance and decent physical properties. TEMPO is also known to be an efficient catalyst for alcohol oxidation, oxygen reduction, and various complex organic reactions. It can be attached to various aliphatic and conductive polymers to form high-loading catalysis systems. The performance and efficiency of TEMPO-containing materials strongly depend on the molecular structure, and thus rational design of such compounds is vital for successful implementation. We discuss synthetic approaches for producing electroactive polymers based on conductive and non-conductive backbones with organic radical substituents, fundamental aspects of electrochemistry of such materials, and their application in energy storage devices, such as batteries, redox-flow cells, and electrocatalytic systems. We compare the performance of the materials with different architectures, providing an overview of diverse charge interactions for hybrid materials, and presenting promising research opportunities for the future of this area.

Half-salen Fe(III) covalently post-modified MIL-125(Ti)-NH2 MOF for effective photocatalytic peroxymonosulfate activation

In this work, an amino functionalized metal organic framework (MOF), MIL-125(Ti)-NH2, is modified by salicylaldehyde via Schiff-base reaction, and the grafted organic substituent is further coordinated with ferric ions to form a half-salen Fe(III) covalently functionalized MOF, MIL-125(Ti)-Sal-Fe. The as-prepared composite is evaluated by light-driven catalytic activation of peroxymonosulfate (PMS) for the degradation of tetracycline hydrochloride (TC). The results imply that the TC removal given by MIL-125(Ti)-Sal-Fe/PMS/light is >88.9% after 40 mins in a wide pH range from 3 to 9; still, the kinetic constant for the degradation reaction under the optimized condition is 0.03553 min−1, which is much higher than that of either decomposition conducted by MIL-125(Ti)-NH2 (0.01801 min−1) or salicylaldehyde modified MOF, MIL-125(Ti)-Sal (0.01987 min−1). The significant enhancement of the photocatalytic performance can be attributed to the ligand-to-metal charge transfer (LMCT) within the integrated half salen Fe(III) complex, highly accelerating the redox cycle from Fe(III) to Fe(II). Our study opens up a novel insight into the amelioration of MOF-based PMS activation.

New Ceramics Precursors Containing Si and Ge Atoms-Cubic Germasilsesquioxanes-Synthesis, Thermal Decomposition and Spectroscopic Analysis.

Compounds of the silsesquioxane type are attractive material precursors. High molecular weights and well-defined structures predestine them to create ceramics with a controlled composition at the molecular level. New molecular precursors of ceramic materials with the ratio of Si:Ge = 7:1 atoms were obtained. The influence of organic substituents on the thermal decomposition processes of germasilsesquioxanes was investigated. Some of the structures obtained are characterized by a high non-volatile residue after the thermal decomposition process. The introduction of the germanium atom to the structure of the silsesquioxane molecular cage reduces the thermal stability of the obtained structures.

Effect of organic linker substituent on catalytic activity of UiO-66 metal-organic framework in selective oxidation of propylene glycol: homolytic versus heterolytic activation of hydrogen peroxide

A family of isoreticular metal-organic frameworks, based on the UiO-66 structure with NH2-, OH-, HSO3-, and NO2-substituted terephthalic acid, are synthesized and tested as catalysts in liquid-phase oxidation of propylene glycol (PG) with hydrogen peroxide and compared with the catalytic performances of unsubstituted UiO-66. The obtained materials are characterized by X-ray diffraction, FT-IR, thermogravimetric analysis (TGA), nuclear magnetic resonance spectroscopy (1H NMR), and Fourier-transform infrared spectroscopy (FT-IR) of adsorbed CO and scanning electron microscopy (SEM) methods. Hydroxyacetone (HA) is the main product over all X-UiO-66 catalysts under the reaction conditions used. The nature of substituent drastically affects the PG conversion and the oxidant utilization efficiency. The presence of electron-withdrawing groups in the organic linker leads to preferential heterotic activation of H2O2, whereas the increase of electron density around Zr active sites, promoted by electron-donating groups, enhances the unproductive homolytic oxidant decomposition. The insertion of NO2 group results in almost double increase in the HA yield (15.5 vs. 8.8%) and hydrogen peroxide utilization efficiency (98 vs. 36%) in comparison with the reaction catalyzed by H-UiO-66. The NO2-UiO-66 can be recycled without the loss of the catalytic activity and preserves its structure after the catalytic cycle.

Excellent yield of a variety of silicon-boron radicals and their reactivity.

Herein we report stable silicon-boron radicals of composition LSi(NMe2)-B(Br)Tip (1), LSi(NMe2)-B(I)Tip (2) LSi(tBu)-B(I)Tip (3) [L = PhC(NtBu)2]. They were prepared in high yield using a one pot reaction of LSiR, X2BTip and KC8 in a 1 : 1 : 1 molar ratio (R = tBu, NMe2; X = Br, I). The reaction of the silicon-boron radical with Br2 and Se affords the dihalogenated compound LSi(tBu)-B(Br2)Tip (4) and oxidative addition product LSi(tBu)Se (5). All the compounds were characterized by single-crystal X-ray structural analysis, electron paramagnetic resonance (EPR) analysis, elemental analysis, multinuclear NMR spectroscopy, and mass spectrometry. Quantum chemical calculations show that the B-centered radicals 1-3 are stabilised by hyperconjugative interactions.