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Boron functional groups are often introduced in place of aromatic carbon–hydrogen bonds to expedite small-molecule diversification through coupling of molecular fragments 1 – 3 . Current approaches based on transition-metal-catalysed activation of carbon–hydrogen bonds are effective for the borylation of many (hetero)aromatic derivatives 4 , 5 but show narrow applicability to azines (nitrogen-containing aromatic heterocycles), which are key components of many pharmaceutical and agrochemical products 6 . Here we report an azine borylation strategy using stable and inexpensive amine-borane 7 reagents. Photocatalysis converts these low-molecular-weight materials into highly reactive boryl radicals 8 that undergo efficient addition to azine building blocks. This reactivity provides a mechanistically alternative tactic for sp 2 carbon–boron bond assembly, where the elementary steps of transition-metal-mediated carbon–hydrogen bond activation and reductive elimination from azine-organometallic intermediates are replaced by a direct, Minisci 9 -style, radical addition. The strongly nucleophilic character of the amine-boryl radicals enables predictable and site-selective carbon–boron bond formation by targeting the azine’s most activated position, including the challenging sites adjacent to the basic nitrogen atom. This approach enables access to aromatic sites that elude current strategies based on carbon–hydrogen bond activation, and has led to borylated materials that would otherwise be difficult to prepare. We have applied this process to the introduction of amine-borane functionalities to complex and industrially relevant products. The diversification of the borylated azine products by mainstream cross-coupling technologies establishes aromatic amino-boranes as a powerful class of building blocks for chemical synthesis. Selective borylation of azines—nitrogen-containing aromatic heterocycles used in the synthesis of many pharmaceuticals—is made possible by forming a radical from an aminoborane using a photocatalyst.

Carbon-based polynuclear clusters are designed and investigated for geometric, electronic, and nonlinear optical (NLO) properties at the CAM-B3LYP/6-311++G(d,p) level of theory. Significant binding energies per atom (ranging from −162.4 to −160.0 kcal mol−1) indicate excellent thermodynamic stabilities of these polynuclear clusters. The frontier molecular orbital (FMOs) analysis indicates excess electron nature of the clusters with low ionization potential, suggesting that they are alkali-like. The decreased energy gaps (EH-L) with increased alkali metals size revael the improved electrical conductivity (σ). The total density of state (TDOS) study reveals the alkali metals’ size-dependent electronic and conductive properties. The significant first and second hyperpolarizabilities are observed up to 5.78 × 103 and 5.55 × 106 au, respectively. The βo response shows dependence on the size of alkali metals. Furthermore, the absorption study shows transparency of these clusters in the deep-UV, and absorptions are observed at longer wavelengths (redshifted). The optical gaps from TD-DFT are considerably smaller than those of HOMO-LUMO gaps. The significant scattering hyperpolarizability (βHRS) value (1.62 × 104) is calculated for the C3 cluster, where octupolar contribution to βHRS is 92%. The dynamic first hyperpolarizability β(ω) is more pronounced for the EOPE effect at 532 nm, whereas SHG has notable values for second hyperpolarizability γ(ω).

Sunscreens, a primary defense against ultraviolet (UV) radiation, use UV filters to mitigate the harmful effects of UVA and UVB radiation, including DNA damage, skin aging, and cancer. However, organic UV filters like benzophenones, oxybenzone, sulisobenzone, and PABA are persistent pollutants, posing environmental risks due to their incomplete removal by conventional wastewater treatment. This study investigates the encapsulation of hazardous UV filters inside a stable belt[14]pyridine nanobelt to facilitate their removal through host-guest interactions. The higher values of interaction energies (E int ) of the designed host-guest complexes ranging from − 13.70 to −26.11 kcal/mol, ensure the stability of the complexes. Frontier molecular orbital (FMO) analysis reveal the significant role of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the host nanobelt towards the HOMO and LUMO of complexes, which is confirmed via density of states (DOS) analysis. Natural bond orbital (NBO) analysis determines the direction of charge transfer, i.e., from the host towards guest species in all complexes. The highest magnitude of NBO charge is observed for sulisobenzone@belt complex, i.e., 0.022|e|. Electron density difference (EDD) analysis visually illustrate the accumulation of charge density over the guest in all the complexes, i.e., a validation of the direction of charge transfer predicted via NBO analysis. The results of non-covalent interaction index (NCI) and quantum theory of atoms in molecules (QTAIM) analyses reveal that the host-guest complexes are stabilized via van der Waals interactions, and a greater number of bond critical points (BCPs) are found for sulisobenzone@belt i.e., 15. Moreover, the recovery time decreases with increasing temperature and is highest for the complex with greater E int i.e., 1.4 10 7 s (at 298 K) for oxybenzone@belt complex. Overall, the study aims to design stable host-guest complexes for effective encapsulation of harmful UV filters, in order to reduce their harmful effects.

. The present article applies the idea of Caputo-Fabrizio time fractional derivatives to magnetohydrodynamics (MHD) free convection flow of generalized Walters’-B fluid over a static vertical plate. Free convection is caused due to combined gradients of temperature and concentration. Hence, heat and mass transfers are considered together. The fractional model of Walters’-B fluid is used in the mathematical formulation of the problem. The problem is solved via the Laplace transform method. Exact solutions for velocity, temperature and concentration are obtained. The physical quantities of interest are examined through plots for various values of fractional parameter: α , Walters’-B parameter Γ , magnetic parameter M , Prandtl number Pr, Schmidt number Sc , thermal Grashof number Gr and mass Grashof number Gm . As a special case, the published results from open literature are recovered.

Here, the encapsulation behavior of Cucurbit[7]uril (CB[7]) is studied for six organic UV filters, i.e., benzophenone, homosalate, oxybenzone, dioxybenzone, sulisobenzone, and para aminobenzoic acid (PABA) using density functional theory (DFT). The thermodynamic stability of the designed systems is ensured by the values of interaction energies ranging from − 11.78 to -20.42 kcal/mol, with the highest value observed for dioxybenzone@CB[7]. Non-covalent interaction (NCI) analysis highlights the prevalence of van der Waals interactions in host-guest complexes, supported by quantum theory of atoms in molecule (QTAIM) analysis. The values of interaction energies of individual bonds in QTAIM analysis fall below 3 kcal/mol confirming the van der Waals interactions between the host and guest species. Frontier molecular orbital (FMO) and density of states (DOS) analyses indicate decreased energy gaps in the complexes compared to bare species, while natural bond orbital (NBO) analysis reveals charge transfer from host to guests with the highest observed for oxybenzone@CB[7] (-0.019|e|). Recovery time and desorption energy analysis highlight dioxybenzone@CB[7] as the most strongly adsorbed complex, while benzophenone@CB[7] being the least. The analysis also suggest a decrease in recovery time with increasing temperature (i.e., least for benzophenone@belt complex, i.e., 2.7 10 −6  s at 400 K). These findings illustrate CB[7] as an efficient host for encapsulating organic UV filters, offering a promising approach for reducing their negative ecological consequences.

Continuous studies are being carried out to explore new methods and carrier surfaces for target drug delivery. Herein, we report the covalent triazine framework C6N6 as a drug delivery carrier for fluorouracil (FU) and nitrosourea (NU) anti-cancer drugs. FU and NU are physiosorbed on C6N6 with adsorption energies of −28.14 kcal/mol and −27.54 kcal/mol, respectively. The outcomes of the non-covalent index (NCI) and quantum theory of atoms in molecules (QTAIM) analyses reveal that the FU@C6N6 and NU@C6N6 complexes were stabilized through van der Waals interactions. Natural bond order (NBO) and electron density difference (EDD) analyses show an appreciable charge transfer from the drug and carrier. The FU@C6N6 complex had a higher charge transfer (−0.16 e−) compared to the NU@C6N6 complex (−0.02 e−). Frontier molecular orbital (FMO) analysis reveals that the adsorption of FU on C6N6 caused a more pronounced decrease in the HOMO-LUMO gap (EH-L) compared to that of NU. The results of the FMO analysis are consistent with the NBO and EDD analyses. The drug release mechanism was studied through dipole moments and pH effects. The highest decrease in adsorption energy was observed for the FU@C6N6 complex in an acidic medium, which indicates that FU can easily be off-loaded from the carrier (C6N6) to a target site because the cancerous cells have a low pH compared to a normal cell. Thus, it may be concluded that C6N6 possesses the therapeutic potential to act as a nanocarrier for FU to treat cancer. Furthermore, the current study will also provide motivation to the scientific community to explore new surfaces for drug delivery applications.

Numerous issues with pharmacokinetics and water solubility of current anticancer drugs have hindered the development of chemotherapy, resulting in significant side effects and patient resistance to multiple therapies. Nanomedicine revolutionized cancer treatment by introducing nanocarriers to enhance drug delivery. This study investigates the use of benzimidazolone capsules as nanocarrier for drug delivery of flutamide (FLT) and gemcitabine (GB) (FLT@Cap and GB@Cap). Numerous structural and electrical parameters demonstrate that both drugs interact well with nanocapsules and are easily transported to the targeted site. Using complexation energy analysis, quantum theory of atoms in molecules (QTAIM), non-covalent interactions (NCI), natural bond orbital (NBO), frontier molecular orbital (FMO), and density of states (DOS) analyses, the drug delivery of flutamide (FLT) and gemcitabine (GB) via benzimidazolone capsule is described. FLT@Cap and GB@Cap exhibit strong drug-capsule interaction, with adsorption energies of -42.18 and − 51.59 kcal/mol, respectively. QTAIM and NCI analysis validate the non-covalent interactions between FLT, GB, and capsule. To comprehend the shifting of electron density from drug to surface, NBO analysis is utilized. After complexation, (E H−L ) which describes the HOMO-LUMO energy gap is reduced, and the perturbations in the electronic parameters are estimated using FMO analysis. The results indicate a high degree of selectivity for FLT and GB on the surface of the benzimidazolone capsule.

The toxicity of transition metals, including copper(II), manganese(II), iron(II), zinc(II), hexavalent chromium, and cobalt(II), at elevated concentrations presents a significant threat to living organisms. Thus, the development of efficient sensors capable of detecting these metals is of utmost importance. This study explores the utilization of two-dimensional nitrogenated holey graphene (C2N) nanosheet as a sensor for toxic transition metals. The C2N nanosheet’s periodic shape and standard pore size render it well suited for adsorbing transition metals. The interaction energies between transition metals and C2N nanosheets were calculated in both gas and solvent phases and were found to primarily result from physisorption, except for manganese and iron which exhibited chemisorption. To assess the interactions, we employed NCI, SAPT0, and QTAIM analyses, as well as FMO and NBO analysis, to examine the electronic properties of the TM@C2N system. Our results indicated that the adsorption of copper and chromium significantly reduced the HOMO–LUMO energy gap of C2N and significantly increased its electrical conductivity, confirming the high sensitivity of C2N towards copper and chromium. The sensitivity test further confirmed the superior sensitivity and selectivity of C2N towards copper. These findings offer valuable insight into the design and development of sensors for the detection of toxic transition metals.

Zigzag molecular nanobelts have recently captured the interest of scientists because of their appealing aesthetic structures, intriguing chemical reactivities, and tantalizing features. In the current study, first-row transition metals supported on an H6-N3-belt[6]arene nanobelt are investigated for the electrocatalytic properties of these complexes for the hydrogen dissociation reaction (HDR). The interaction of the doped transition metal atom with the nanobelt is evaluated through interaction energy analysis, which reveals the significant thermodynamic stability of TM-doped nanobelt complexes. Electronic properties such as frontier molecular orbitals and natural bond orbitals analyses are also computed, to estimate the electronic perturbation upon doping. The highest reduction in the HOMO–LUMO energy gap compared to the bare nanobelt is seen in the case of the Zn@NB catalyst (4.76 eV). Furthermore, for the HDR reaction, the Sc@NB catalyst displays the best catalytic activity among the studied catalysts, with a hydrogen dissociation barrier of 0.13 eV, whereas the second-best catalytic activity is observed for the Zn@NB catalyst (0.36 eV). It is further found that multiple active sites, i.e., the presence of the metal atom and nitrogen atom moiety, help to facilitate the dissociation of the hydrogen molecule. These key findings of this study enhance the understanding of the relative stability, electronic features, and catalytic bindings of various TM@NB catalysts.

Purpose - The aim of this empirical study is to explore the factors that affect the capital structure of manufacturing firms and to investigate whether the capital structure models derived from Western settings provide convincing explanations for capital structure decisions of the Pakistani firms. Design/methodology/approach - Different conditional theories of capital structure are reviewed (the trade-off theory, pecking order theory, agency theory, and theory of free cash flow) in order to formulate testable propositions concerning the determinants of capital structure of the manufacturing firms. The investigation is performed using panel data procedures for a sample of 160 firms listed on the Karachi Stock Exchange during 2003-2007. Findings - The results suggest that profitability, liquidity, earnings volatility, and tangibility (asset structure) are related negatively to the debt ratio, whereas firm size is positively linked to the debt ratio. Non-debt tax shields and growth opportunities do not appear to be significantly related to the debt ratio. The findings of this study are consistent with the predictions of the trade-off theory, pecking order theory, and agency theory which shows that capital structure models derived from Western settings does provide some help in understanding the financing behavior of firms in Pakistan. Practical implications - This study has laid some groundwork to explore the determinants of capital structure of Pakistani firms upon which a more detailed evaluation could be based. Furthermore, empirical findings should help corporate managers to make optimal capital structure decisions. Originality/value - To the authors' knowledge, this is the first study that explores the determinants of capital structure of manufacturing firms in Pakistan by employing the most recent data. Moreover, this study somehow goes to confirm that same factors affect the capital structure decisions of firms in developing countries as identified for firms in developed economies. [PUBLICATION ABSTRACT]