Natural Bond Research Articles

‘We Hope He Will Be Dead by Tonight’: Shared Estrangement in the ICU of the Universitas Hospital

This article recounts the week in which the author and his four sisters spent waiting for their father to die, and suggests that intimacy or friendship viewed as ‘shared estrangement’ – a friendship or intimacy not rooted in sharing common ground – might provide a lens through which to consider the nature of the deep bond that developed between the author and his siblings during that week. Raising the possibility that the relationship between author and his sisters could in some ways be read as a <i>queer </i>one, not least because it demanded an openness to alterity and requireds attention and care, mutual trust, and, bizarre as it may sound, even betrayal, the author suggests that a deep bond slowly developed between the siblings during the week being described, not <i>despite</i> the prtofound differences between the siblings, but partly <i>because</i> of it.

Structure, Spectroscopy, and Theoretical insights on Co-crystals of 2,4-Diamino-6-Methyl-1,3,5-Triazine Bis(4-Aminobenzoic acid) Monohydrate as a promising anti-cancer agent

Co-crystals of 2,4-diamino-6-methyl-1,3,5-triazine bis (4-aminobenzoic acid) monohydrate (hereafter named DMTAB) have been grown from a slow solvent method at room temperature. Single crystal XRD reveals the centrosymmetric nature of the grown crystal with the P21/n space group. Hirshfeld Surface analysis has been performed to visualize and analyse the spatial distribution of intermolecular interactions in a molecular system. The presence of functional groups has been analysed with Fourier Transform Infrared and Raman studies. By employing NBO analysis, valuable insights into the nature of chemical bonds, electron delocalization, and the overall stability of molecular systems have been examined. Theoretical UV–Vis spectrum studies using Time-Dependent - Density Functional Theory (TD-DFT) in different solvents provide a valuable computational tool to predict and understand the electronic transitions of molecules. HOMO-LUMO analysis and density of states spectrum in different solvents further shed light on the electronic structure and reactivity of molecules in their surroundings. First-order hyperpolarizability calculations have been used to analyse the nonlinear optical response of a grown material. Molecular docking studies were conducted to anticipate the binding conformation of the DMTAB ligand with the relevant target proteins, specifically the ovarian cancer target (Rad6 ubiquitin-conjugated enzyme [PDB ID: 2YB6]) and breast cancer target (protein kinase CK2 [PDB ID: 6HNY].

Development and performance evaluation of re-crosslinkable preformed particle gel under high temperature and high salt conditions

Self-healable hydrogels have attracted significant interests in the fields of environmental protection, oil plugging and electronic sensors, etc. Benefiting from the synergistic contribution of hydrogen bonding and ligand chelation, in this work, we prepared a series of self-healable hydrogels via a simple and inexpensive approach, which overcame the limitations of the intrinsic nature of dynamic covalent bonds and non-covalent interactions under harsh conditions. Systematic study of the effect of temperature, salt concentration and particle size on the physicochemical performance of the re-crosslinking progress revealed that re-crosslinked gels using particles of 0.20–0.28 mm (in a solution with salt concentration of 10%) at 130 °C presented an elastic modulus of 62 Pa at a frequency of 10 Hz and remained elastic after 45 days of aging (elastic modulus: 18,170 Pa). Of particular interest, gel particles with a particle size of 0.125–0.28 mm can be reassembled at temperatures up to 150 °C or salt concentrations up to 20%, which is superior to a plethora of previous reports (self-healing temperature usually less than 130 °C, salt concentration <10%). Employment of the green inexpensive sodium D-gluconate instead of partial acrylamide makes the gel product a promising candidate material for oil plugging, targeting fractured reservoirs for consistent control.

Mechanism of formation water molecules and chemical bonds in Leptothrix materials

The provided study involves investigating chemical interactions in Leptothrix biomaterial through infrared spectroscopy. The analysis explores variations in chemical relationships based on the nature of chemical bonds and biomaterial coordinates. The primary chemical bonds identified in the biomaterial are associated with Fe-O vibrations and resonances of [OH] functional groups. Additionally, the study presents model representations detailing the formation mechanism of water molecules within the Leptothrix matrix. Model calculations for a two-vacancy cluster defect structure in Fe2O3 and Fe3O4 reveal lifetimes of 180 ps and 174 ps, respectively.

Unlocking Precision Docking for Metalloproteins.

Metalloproteins play a fundamental role in molecular biology, contributing to various biological processes. However, the discovery of high-affinity ligands targeting metalloproteins has been delayed due, in part, to a lack of suitable tools and data. Molecular docking, a widely used technique for virtual screening of small-molecule ligand interactions with proteins, often faces challenges when applied to metalloproteins due to the particular nature of the ligand metal bond. To address these limitations associated with docking metalloproteins, we introduce a knowledge-driven docking approach known as "metalloprotein bias docking" (MBD), which extends the AutoDock Bias technique. We assembled a comprehensive data set of metalloprotein-ligand complexes from 15 different metalloprotein families, encompassing Ca, Co, Fe, Mg, Mn, and Zn metal ions. Subsequently, we conducted a performance analysis of our MBD method and compared it to the conventional docking (CD) program AutoDock4, applied to various metalloprotein targets within our data set. Our results demonstrate that MBD outperforms CD, significantly enhancing accuracy, selectivity, and precision in ligand pose prediction. Additionally, we observed a positive correlation between our predicted ligand free energies and the corresponding experimental values. These findings underscore the potential of MBD as a valuable tool for the effective exploration of metalloprotein-ligand interactions.

Mechanistic Insights into the Selectivity for Arsenic over Phosphate Adsorption by Fe3+-Cross-Linked Chitosan Using DFT.

Fe3+-cross-linked chitosan exhibits the potential for selectively adsorbing arsenic (As) over competing species, such as phosphate, for water remediation. However, the effective binding mechanisms, bond nature, and controlling factor(s) of the selectivity are poorly understood. This study employs ab initio calculations to examine the competitive binding of As(V), P(V), and As(III) to neat chitosan and Fe3+-chitosan. Neat chitosan fails to selectively bind As oxyanions, as all three oxyanions bind similarly via weak hydrogen bonds with preferences of P(V) = As(V) > As(III). Conversely, Fe3+-chitosan selectively binds As(V) over As(III) and P(V) with binding energies of -1.9, -1, and -1.8 eV for As(V), As(III), and P(V), respectively. The preferences are due to varying Fe3+-oxyanion donor-acceptor characteristics, forming covalent bonds with distinct strengths (Fe-O bond ICOHP values: - 4.9 eV/bond for As(V), - 4.7 eV/bond for P(V), and -3.5 eV/bond for As(III)). Differences in pKa between As(V)/P(V) and As(III) preclude any preference for As(III) under typical environmental pH conditions. Furthermore, our calculations suggest that the binding selectivity of Fe3+-chitosan exhibits a pH dependence. These findings enhance our understanding of the Fe3+-oxyanion interaction crucial for preferential oxyanion binding using Fe3+-chitosan and provide a lens for further exploration into alternative transition-metal-chitosan combinations and coordination chemistries for applications in selective separations.

Novel Eu3+ doped mixed alkaline-earth zinc silico-aluminate glass for white-light-emitting diode, fingerprint, and security ink application

In this work, novel calcium strontium magnesium zinc silico-aluminate (CSrMZSAEux) glasses doped with varied concentrations of Eu2O3 (0.5, 1.0, 1.5, 2, 3, 4 and 5 mol%) were synthesized by an open-air melt quenching technique. The Raman and FTIR studies revealed that Eu3+ ions connected to both AlO4 and SiO4 units through non-bridging oxygen. The decrease in thermal stability from 158 to 141 °C with the gradual inclusion of Eu2O3 ions is showing modifier role of Eu3+ ions. The intense emission spectra (5D0→7Fi = 0-4 transitions) measured under 395 nm excitation wavelength, showed no concentration quenching within the studied dopant ions concentration. The high Judd-Ofelt parameter (Ω2 = 5.06 to 6.31 × 10−20 cm2) and red-to-orange emission intensity ratio (R = 3.627–4.102) have revealed the covalent nature of Eu-ligand bond and high color richness, respectively. Among all prepared glasses, the CSrMZSAEu5.0 glass showed high color purity (98.9%), correlated color temperature (<1000K), highest emission intensity and reasonable lifetime value (1387±16 μs). Further, the temperature-dependent photoluminescence demonstrated that the CSrMZSAEu5.0 glass has good emission thermal stability (⁓ 66% at 150 °C) with a high activation energy of 0.258 eV. Hence, the CSrMZSAEu5.0 glass can be used as red component for white-light-emitting diode, and red-light applications. Furthermore, the CSrMZSAEu5.0 glass composition is observed to be suitable for latent fingerprint and security ink applications.

Theoretical Investigation Non-covalent Interactions of N-(diphenylphosphinothioyl)-2-pyrazinecarboxamide

Abstract. Phosphine chalcogenides can form reliable and reproducible supramolecular synthons through noncovalent interactions that can be employed for designing high dimensional supramolecular architectures. Here, we systematically study the influence of non-covalent interactions in the fabrication of these synthons and the stability of the crystalline structure of (N2C4H3)C(O)NHP(S)(C6H5)2 (1) through non-covalent interactions (NCI) analysis, molecular Hirshfeld surfaces and the corresponding two-dimensional (2D) fingerprint plots. The theoretical studies were employed to further confirm the presence of these synthons by comparing the stabilization energies of the dimers and monomers. The nature and electronic structure of the phosphor-chalcogenid bond in (N2C4H3)C(O)NHP(E)(OC6H5)2(E = S(1), O(2), and Se (3)) have also been evaluated by QTAIM, NBO, MEP, and HOMO-LUMO energy gaps.

Control over Charge Separation by Imine Structural Isomerization in Covalent Organic Frameworks with Implications on CO2 Photoreduction.

Two-dimensional covalent organic frameworks (COFs) are an emerging class of photocatalytic materials for solar energy conversion. In this work, we report a pair of structurally isomeric COFs with reversed imine bond directions, which leads to drastic differences in their physical properties, photophysical behaviors, and photocatalytic CO2 reduction performance after incorporating a Re(bpy)(CO)3Cl molecular catalyst through bipyridyl units on the COF backbone (Re-COF). Using the combination of ultrafast spectroscopy and theory, we attributed these differences to the polarized nature of the imine bond that imparts a preferential direction to intramolecular charge transfer (ICT) upon photoexcitation, where the bipyridyl unit acts as an electron acceptor in the forward imine case (f-COF) and as an electron donor in the reverse imine case (r-COF). These interactions ultimately lead the Re-f-COF isomer to function as an efficient CO2 reduction photocatalyst, while the Re-r-COF isomer shows minimal photocatalytic activity. These findings not only reveal the essential role linker chemistry plays in COF photophysical and photocatalytic properties but also offer a unique opportunity to design photosensitizers that can selectively direct charges.

Two-Dimensional Room-Temperature Magnetism in Janus Mn2I3S3 and Cr2I3Se3 Monolayers with Tunable Magnetic Properties by Strain Engineering.

Exploring room-temperature intrinsic magnetism in two-dimensional (2D) materials for nanoscale spintronic devices has garnered significant interest. Achieving a high Curie temperature and substantial spin polarization in 2D ferromagnetic materials remains challenging. Drawing inspiration from the substantial enhancement of the Curie temperature observed in ferromagnetic CrIS monolayers by manipulating the covalent nature of Cr-S bonds, our study systematically delves into the electronic structure and magnetic properties of Janus M2X3Y3 (M = V, Cr, Mn, Fe, and Co; X = Cl, Br, I; Y = S, Se, and Te) monolayers through first-principles calculations. Our findings reveal that 15 kinds of these monolayers exhibit dynamic and thermodynamic stability while displaying diverse electronic and ferromagnetic characteristics. Notably, Mn2I3S3 demonstrates half-metallicity and in-plane magnetic anisotropy, while Cr2I3Se3 exhibits a half-semiconductor and perpendicular magnetic anisotropy. Consequently, Mn2I3S3 transforms from in-plane to perpendicular magnetic anisotropy through strain manipulation. Cr2I3Se3, under strain, transforms from a half-semiconductor to a bipolar magnetic semiconductor. The strong coupling caused by the M-Y bonds makes them have a Curie temperature higher than room temperature. The unique magnetic properties exhibited by the 2D Janus Mn2I3S3 and Cr2I3Se3 magnets hold promise for applications in spintronics. Our study provides a foundational understanding for future experimental explorations in this exciting research area.

Earnings News and Over‐the‐Counter Markets

ABSTRACTWe document significant increases in bond market liquidity around earnings announcements. These increases are attributed to decreased search and bargaining costs, which arise from the over‐the‐counter (OTC) nature of bond markets and outweigh increases in information asymmetry during these periods. Our evidence traces reductions in search and bargaining costs to two sources around earnings announcements: (1) improved access to dealers and (2) increased participation from institutional investors, who can more easily transact with multiple dealers. Overall, our findings highlight a novel channel through which firm‐specific information affects asset prices.

What is lignin - the evolution of views (review)

The review considers changes in ideas about the biosynthesis, structure and functions of lignin in plants, starting from early mentions and up to the present. Alternative points of view on the process of lignin biosynthesis, its spatial and supramolecular structure, and the nature of lignincarbohydrate bonds are presented. &#x0D; A special place in the review is occupied by the results of studies of lignin modification with the aim of reducing the content and changing the composition of monomer units by genetic engineering methods. Comparison of the structure of lignins isolated from transgenic and mutant trees, as well as herbaceous plants, showed that lignin biosynthesis is plastic and, in addition to canonical monolignols (coniferyl, synapic, and coumaric alcohols), other phenolic compounds can also participate in it.&#x0D; The study of the so-called "stress lignins" showed that lignin plays an important role in protecting plants from adverse environmental influences: mechanical damage, drought, low temperatures, pathogens, etc.&#x0D; The results of studies of the genetic modification of lignin made it possible to outline a program for directed modification of the biosynthesis process in order to obtain designer lignins, i.e. lignins with desired properties. This group also includes the so-called zip-lignins. They are distinguished by the presence of ester bonds between phenylpropane units.&#x0D; It is noted that, when conducting research in the field of genetic engineering, it is necessary to find a compromise between improving the processing of plant materials due to the modification of lignin and the viability of transgenic plants.

Aging Effects in Zr(Fe0.5V0.5)2 Tritides

We report an experimental study on the tritiding capabilities over a long period of the intermetallic compound Zr(Fe0.5V0.5)2. The study was carried out with the prospect of using the alloy as a chemical converter to reduce HTO. Two identical getter beds, containing 1 gram of alloy in powder form each, were used in the experiments. While one of them was exploited to determine the tritium isotherms of the virgin alloy, the other bed was loaded at 75% of stoichiometry with 354 Ci of tritium and left to age for 1500 days. The bed was then unloaded and the isotherms of the aged alloy were determined twice to check the repeatability. The main results of the work are that, while enthalpy and entropy changes for tritium dissolution at infinite dilution are practically the same for the fresh alloy and the aged alloy, they vary significantly when the isotherms are determined on the aged alloy at a large enough distance of time (one week). This behavior is ascribed to the He3 present in the interstitial sites. However, the fact that the solubility of the alloy decreases with aging suggests that the He3 present either in the interstitial sites or in bubbles subtracts sites for dissolution. Also to be stressed is that in the tritide-forming region, these thermodynamic values decrease with aging in a monotonic way. This different behavior is tentatively explained by invoking the nature of the tritium bond.

Ultrastable, Superrobust, and Recyclable Supramolecular Polymer Networks

AbstractSupramolecular polymer networks (SPNs), crosslinked by noncovalent bonds, have emerged as reorganizable and recyclable polymeric materials with unique functionality. However, poor stability is an imperative challenge faced by SPNs, because SPNs are susceptible to heat, water, and/or solvents due to the dynamic and reversible nature of noncovalent bonds. Herein, the design of a noncovalent cooperative network (NCoN) to simultaneously stabilize and reinforce SPNs is reported, resulting in an ultrastable, superrobust, and recyclable SPN. The NCoN is constructed by multiplying the H‐bonding sites and tuning the conformation/geometry of the H‐bonding segment to optimize the multivalence cooperativity of H‐bonds. The rationally designed H‐bonding segment with high conformational compliance favors the formation of tightly packed H‐bond arrays comprising higher‐density and stronger H‐bonds. Consequently, the H‐bonded crosslinks in the NCoN display a covalent crosslinking effect but retain on‐demand dynamics and reversibility. The resultant ultrastable SPN not only displays remarkable resistance to heat up to 120 °C, water soaking, and a broad spectrum of solvents, but also possesses a superhigh true stress at break (1.1 GPa) and an ultrahigh toughness (406 MJ m−3). Despite the covalent‐network‐like stability, the SPN is recyclable through activating its reversibility in a high‐polarity solvent heated to a threshold temperature.

Ultrastable, Superrobust, and Recyclable Supramolecular Polymer Networks.

Supramolecular polymer networks (SPNs), crosslinked by noncovalent bonds, have emerged as reorganizable and recyclable polymeric materials with unique functionality. However, poor stability is an imperative challenge faced by SPNs, because SPNs are susceptible to heat, water, and/or solvents due to the dynamic and reversible nature of noncovalent bonds. Herein, the design of a noncovalent cooperative network (NCoN) to simultaneously stabilize and reinforce SPNs is reported, resulting in an ultrastable, superrobust, and recyclable SPN. The NCoN is constructed by multiplying the H-bonding sites and tuning the conformation/geometry of the H-bonding segment to optimize the multivalence cooperativity of H-bonds. The rationally designed H-bonding segment with high conformational compliance favors the formation of tightly packed H-bond arrays comprising higher-density and stronger H-bonds. Consequently, the H-bonded crosslinks in the NCoN display a covalent crosslinking effect but retain on-demand dynamics and reversibility. The resultant ultrastable SPN not only displays remarkable resistance to heat up to 120 °C, water soaking, and a broad spectrum of solvents, but also possesses a superhigh true stress at break (1.1 GPa) and an ultrahigh toughness (406 MJ m-3 ). Despite the covalent-network-like stability, the SPN is recyclable through activating its reversibility in a high-polarity solvent heated to a threshold temperature.

Insight into the interaction of isochroman with bovine serum albumin: extensive experimental and computational investigations

The way therapeutic compounds interact with serum protein provides valuable information on their pharmacokinetics, toxicity, effectiveness, and even their structural-related information. Isochroman (IC) is a phytochemical compound obtained from the leaves of Olea europea plant. The derivatives of IC have various pharmacological properties including antidepressants, antihistamines, antiinflammation, anticonvulsants, appetite depressants, etc. The binding of small molecules to bovine serum albumin (BSA) is useful to ensure their efficacy. Thus, in this study, we have found out the binding mode of IC with BSA using several spectroscopic and in silico studies. UV and fluorescence spectroscopy suggested the complex formation between IC and BSA with a binding constant of 103 M−1. IC resulted in fluorescence quenching in BSA through static mechanism. The microenvironmental and conformational changes in BSA were confirmed using synchronous and three-dimensional studies. Site marker experiment revealed the IC binding in site-III of BSA. The influence of vitamins, metals and β-cyclodextrin (β-CD) on binding constant of IC–BSA complex was also examined. Circular dichroism spectra showed that α-helical of BSA decreased upon interaction with IC. Computational and experimental results were complimentary with one another and assisted in determining the binding sites, nature of bonds and amino acids included in the IC–BSA complex formation. Communicated by Ramaswamy H. Sarma

Preparation of a Compound with a SiII -SiIV -SiII Bonding Arrangement.

Herein, we report the synthesis of a rare bis-silylene, 1, in which two SiII atoms are bridged by a SiIV atom. Compound 1 contains an unusual SiII -SiIV -SiII bonding arrangement with SiII -SiIV bond distances of 2.4212(8) and 2.4157(7) Å. Treatment of 1 with Fe(CO)5 afforded a dinuclear Fe0 complex 2 with two unusually long Si-Si bonds (2.4515(8) and 2.4488(10) Å). We have also carried out a detailed computational study to understand the nature of the Si-Si bonds in these compounds. Natural bond orbital (NBO) and energy decomposition analysis-natural orbital for chemical valence (EDA-NOCV) analyses reveal that the Si-Si bonds in 1 and 2 are of an electron-sharing nature.

Inquire into Co-doped pyrite crystal structure modifications and implications for flotation behavior: A DFT study

Cobalt (Co), as a vital strategic resource, is applied widely in battery materials and alloy manufacturing. In minerals, Co is often doped into pyrite by lattice substitution. Co-doped pyrite is typically enriched by froth flotation. However, research on the flotation mechanisms of Co-doped pyrite is limited. Density functional theory was used to investigate the influence of Co doping on the crystal structure of pyrite. The difference in the hydrophobicity and collector adsorption of Co doping in pyrite was discussed. Co replaces Fe in pyrite through lattice substitution to form Co-pyrite. Co-doped pyrite shows increased conductivity and decreased covalent bonding nature of Co-S bonds compared with pyrite. Co doping enhances the surface hydrophobicity of pyrite. The electron transfer between butyl xanthate (BX) and Co-doped pyrite is more intense than that of pyrite. BX mainly interacts with the Co 3d orbitals of Co-doped pyrite through the S 3p orbitals. The interaction mode is bonding, and orbital hybridization occurs. Moreover, BX exhibits more stable adsorption on the surface of Co-doped pyrite than that on pyrite. The presence of water molecules has a minor promotional effect on the adsorption of BX.

First principle investigation of structural, electronic, optical and thermoelectric properties of Chalcogenide Sr2GeX4(X=S, Se)

The electronic and optical properties of ternary-type chalcogenides are of great interest for solar energy conversion applications. In this study, we investigated the optical, electronic, and transport properties of Sr2GeX4 (X = S and Se) materials using first-principles calculations based on density functional theory. We found that these materials have a robust covalent bond nature and substantial band gaps. The density of states calculations revealed that the Sr-s and Ge-s states play a predominant role, while the S-s and S-p states have a minor influence. The optical properties of the materials are anisotropic, and they have significant UV absorption. The positive Seebeck coefficient values suggest that holes are the primary charge carriers in both materials. The study also discussed various other crucial thermoelectric parameters, which collectively suggest the suitability of these materials for thermoelectric applications. Overall, this study provides valuable insights into the optoelectronic and thermoelectric properties of Sr2GeX4 materials, which could significantly contribute to the development of efficient optoelectronic devices.

Photocatalytic Reduction of CO2 into CO with Cyclometalated Pt(II) Complexes of N^C^N Pincer Dipyridylbenzene Ligands: A DFT Study.

In this work, density functional theory (DFT) calculations were employed to study the photocatalytic reduction of CO2 into CO using a series of Pt(II) square planar complexes with the general formula [Pt(5-R-dpb)Cl] (dpb = 1,3-di(2-pyridyl)benzene anion, R = H, N,N-dimethylaniline,T thiophene, diazaborinine). The CO2-into-CO conversion process is thought to proceed via two main steps, namely the photocatalytic/reduction step and the main catalytic step. The simulated absorption spectra exhibit strong bands in the range 280-460 nm of the UV-Vis region. Reductive quenching of the T1 state of the complexes under study is expected to be favorable since the calculated excited state redox potentials for the reaction with sacrificial electron donors are highly positive. The redox potentials reveal that the reductive quenching of the T1 state, important to the overall process, could be modulated by suitable changes in the N^C^N pincer ligands. The CO2 fixation and activation by the three coordinated Pt(II) catalytically active species are predicted to be favorable, with the Pt-CO2 bond dissociation energies D0 in the range of -36.9--10.3 kcal/mol. The nature of the Pt-CO2 bond of the Pt(II) square planar intermediates is complex, with covalent, hyperconjugative and H-bonding interactions prevailing over the repulsive electrostatic interactions. The main catalytic cycle is estimated to be a favorable exergonic process.