Experimental and Computational Anticorrosion Behaviors of Pyrazole s-Triazine/anilino-morpholino Derivatives for Steel in Acidic Solutions.

The corrosion inhibition of C-steel by two s-triazine/morpholino-anilino-pyrazole derivatives, namely, 4-(3,5-dimethyl-1H-pyrazol-1-yl)-6-morpholino-N-phenyl-1,3,5-triazin-2-amine (1) and N-(4-bromophenyl)-4-(3,5-dimethyl-1H-pyrazol-1-yl)-6-morpholino-1,3,5-triazin-2-amine (2) was investigated by impedimetric and potentiometric studies. It was found that (1) and (2) acted as cathodic-type corrosion inhibitors that retard the hydrogen evolution reaction. The percent corrosion inhibition, 98.5% for compound (2) (with bromo substituent) at 80 ppm, was slightly higher than 97.8% for (1) at 100 ppm. Thus, the replacement of a -H with -Br substituent increased the corrosion inhibition properties. Compound (2) exhibited Temkin isotherm adsorption, whereas compound (1) exhibited Langmuir adsorption. Scanning electron microscopy (SEM) analysis of the steel surface indicated that the inhibitors caused protection of the surface. The weight loss experiment also proved the decrease in the corrosion rate when inhibitors were added. The difference in inhibitory efficiency between compounds (1) and (2) was investigated by density functional theory (DFT) to study neutral and protonated species in gaseous and aqueous phases. The theoretical analysis demonstrated that compound (2) exhibited higher inhibitory activity on a metal surface compared to compound (1), aligning with the experimental results. The energy associated with the metal/adsorbate arrangement, represented by dE ads/dNi , was higher for (2) (-380.91 kcal mol-1) compared to (1) (-371.64 kcal mol-1). This indicated better adsorption of (2) over (1).

Bis(dimethylpyrazolyl)-aniline-s-triazine derivatives as efficient corrosion inhibitors for C-steel and computational studies.

4,6-Bis(3,5-dimethyl-1H-pyrazol-1-yl)-N-phenyl-1,3,5-triazin-2-amine (PTA-1), N-(4-bromophenyl)-4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazin-2-amine (PTA-2) and 4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-N-(4-methoxyphenyl)-1,3,5-triazin-2-amine (PTA-3) were synthesized and characterized. Their corrosion inhibition of carbon C-steel in 0.25 M H2SO4 was studied by electrochemical impedance. The inhibition efficiency (IE%) of triazine was superior due to the cumulative inhibition of triazine core structure and pyrazole motif. Potentiodynamic polarizations suggested that s-triazine derivatives behave as mixed type inhibitors. The IE% values were 96.5% and 93.4% at 120 ppm for inhibitor PTA-2 and PTA-3 bearing -Br and -OCH3 groups on aniline, respectively. While PTA-1 without an electron donating group showed only 79.0% inhibition at 175 ppm. The adsorption of triazine derivatives followed Langmuir and Frumkin models. The values of adsorption equilibrium constant K°ads and free energy change ΔG°ads revealed that adsorption of inhibitor onto steel surface was favoured. A corrosion inhibition mechanism was proposed suggesting the presence of physical and chemical interactions. Density functional theory computational investigation corroborated nicely with the experimental results. Monte Carlo simulation revealed that the energy associated with the metal/adsorbate arrangement dE ads/dN i, for both forms of PTA-2 and PTA-3 with electron donating groups (-439.73 and -436.62 kcal mol-1) is higher than that of PTA-1 molecule (-428.73 kcal mol-1). This aligned with experimental inhibition efficiency results.

Exploring the Sensing Potential of g-C3N4 versus Li/g-C3N4 Nanoflakes toward Hazardous Organic Volatiles: A DFT Simulation Study.

Ab initio calculations were performed to determine the sensing behavior of g-C3N4 and Li metal-doped g-C3N4 (Li/g-C3N4) quantum dots toward toxic compounds acetamide (AA), benzamide (BA), and their thio-analogues, namely, thioacetamide (TAA) and thiobenzamide (TAA). For optimization and interaction energies, the ωB97XD/6-31G(d,p) level of theory was used. Interaction energies (Eint) illustrate the high thermodynamic stabilities of the designed complexes due to the presence of the noncovalent interactions. The presence of electrostatic forces in some complexes is also observed. The observed trend of Eint in g-C3N4 complexes was BA > TAA > AA > TBA, while in Li/g-C3N4, the trend was BA > AA > TBA > TAA. The electronic properties were studied by frontier molecular orbital (FMO) and natural bond orbital analyses. According to FMO, lithium metal doping greatly enhanced the conductivity of the complexes by generating new HOMOs near the Fermi level. A significant amount of charge transfer was also observed in complexes, reflecting the increase in charge conductivity. NCI and QTAIM analyses evidenced the presence of significant noncovalent dispersion and electrostatic forces in Li/g-C3N4 and respective complexes. Charge decomposition analysis gave an idea of the transfer of charge density between quantum dots and analytes. Finally, TD-DFT explained the optical behavior of the reported complexes. The findings of this study suggested that both bare g-C3N4 and Li/g-C3N4 can effectively be used as atmospheric sensors having excellent adsorbing properties toward toxic analytes.

Transition Metal Sensing with Nitrogenated Holey Graphene: A First-Principles Investigation.

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.

Efficient Detection of Nerve Agents through Carbon Nitride Quantum Dots: A DFT Approach.

V-series nerve agents are very lethal to health and cause the inactivation of acetylcholinesterase which leads to neuromuscular paralysis and, finally, death. Therefore, rapid detection and elimination of V-series nerve agents are very important. Herein, we have carried out a theoretical investigation of carbon nitride quantum dots (C2N) as an electrochemical sensor for the detection of V-series nerve agents, including VX, VS, VE, VG, and VM. Adsorption of V-series nerve agents on C2N quantum dots is explored at M05-2X/6-31++G(d,p) level of theory. The level of theory chosen is quite adequate in systems describing non-bonding interactions. The adsorption behavior of nerve agents is characterized by interaction energy, non-covalent interaction (NCI), Bader's quantum theory of atoms in molecules (QTAIM), frontier molecular orbital (FMO), electron density difference (EDD), and charge transfer analysis. The computed adsorption energies of the studied complexes are in the range of -12.93 to -17.81 kcal/mol, which indicates the nerve agents are physiosorbed onto C2N surface through non-covalent interactions. The non-covalent interactions between V-series and C2N are confirmed through NCI and QTAIM analysis. EDD analysis is carried out to understand electron density shifting, which is further validated by natural bond orbital (NBO) analysis. FMO analysis is used to estimate the changes in energy gap of C2N on complexation through HOMO-LUMO energies. These findings suggest that C2N surface is highly selective toward VX, and it might be a promising candidate for the detection of V-series nerve agents.

Covalent Organic Framework (C6N6) as a Drug Delivery Platform for Fluorouracil to Treat Cancerous Cells: A DFT Study.

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.

An Integrated Experimental and Theoretical Studies on the Corrosion Inhibition of Carbon Steel by Harmal Extracts.

The corrosion inhibition effect of the three extracts from Harmal roots (HRE), leaves (HLE), and flowers (HFE) were studied for carbon steel corrosion inhibition in 0.25 M H2SO4 solution. The electrochemical impedance study indicated that the three types of extracts decreased corrosion effectively through a charge transfer mechanism. Harmal roots and leaf extracts showed inhibition values of 94.1% and 94.2%, while it was 88.7% for Harmal flower extract at the inhibitor concentration of 82.6 ppm. Potentiodynamic polarization data revealed that Harmal extracts acted through predominant cathodic type inhibition. Both the corrosion current density and corrosion rate decreased significantly in the presence of Harmal extracts compared to blank solution. The corrosion rate (mpy) value was 63.3, 86.1, and 180.7 for HRE, HLE, and HFE, respectively. The adsorption-free energy change ΔGads (kJ·mol-1) values calculated from the Langmuir adsorption isotherm plots were for HRE (-35.08), HLE (-33.17), and HFE (-33.12). Thus, corrosion inhibition occurred due to the adsorption of Harmal extract on the carbon steel surface via the chemisorption mechanism. Moreover, a computational investigation using B3LYP/6-311G++(d,p) basis set in both gaseous and aqueous phases was performed for the major alkaloids (1-8) present in the Harmal extract.

Radical hydroxymethylation of alkyl iodides using formaldehyde as a C1 synthon.

Radical hydroxymethylation using formaldehyde as a C1 synthon is challenging due to the reversible and endothermic nature of the addition process. Here we report a strategy that couples alkyl iodide building blocks with formaldehyde through the use of photocatalysis and a phosphine additive. Halogen-atom transfer (XAT) from α-aminoalkyl radicals is leveraged to convert the iodide into the corresponding open-shell species, while its following addition to formaldehyde is rendered irreversible by trapping the transient O-radical with PPh3. This event delivers a phosphoranyl radical that re-generates the alkyl radical and provides the hydroxymethylated product.

Synthetic endeavours towards oxasqualenoid natural products containing 2,5-disubstituted tetrahydrofurans--eurylene and teurilene.

2,5-Disubstituted tetrahydrofurans constitute the core skeleton of several natural products and are pivotal synthetic analogues of medicinal importance that exhibit remarkable bioactivities. Oxasqualenoid natural products are implicated as potent biologically active molecules, particularly with regard to demonstrating significant cytotoxicity. Characteristic features of oxasqualenoids containing tetrahydrofuran fragments include the presence of a cis- and/or trans-2,5-disubstituted pattern in tetrahydrofuran moieties, and molecular symmetry is often noticed as well. Given their unique structural features combined with their bioactivity, two representative examples from this class of natural products, eurylene and teurilene, have been briefly reviewed. Eurylene, with reported cytotoxicity against lymphocytic leukemia, contains two non-adjacent linked cis- and trans-2,5-disubstituted tetrahydrofuran rings and a combined total of eight stereogenic centres. It is a chiral molecule due to the lack of a C2 axis of symmetry. Teurilene shows a prominent cytotoxicity on KB cells and has three adjacently linked 2,5-disubstituted tetrahydrofurans. A distinctive achiral facet is observed in teurilene, despite having eight stereocentres, due to the presence of meso symmetry (Cs). The prime objective of this account is to describe a precise mechanistic insight for both cis- and trans-2,5-disubstituted tetrahydrofurans present in these natural products and to highlight the exciting challenges encountered during the installation of functionalities or structural motifs en route to their synthetic approaches.

Utility of thick smears of bone marrow aspirate in pyrexia of unknown origin.

OBJECTIVE: To determine the diagnostic efficacy of Giemsa stained thick smear of bone marrow aspirate for evidence of malaria in febrile individuals in whom the diagnosis was otherwise unknown. DESIGN: Descriptive case-series study. PLACE AND DURATION OF STUDY: This study was conducted at the Department of Medicine, Sandeman Provincial Hospital, Quetta, in the Balochistan province of Pakistan, between January 1994 and December 1998. SUBJECTS AND METHODS: A total of 80 patients were included in the study, who presented with history of fever for more than 3 weeks with splenomegaly and pancytopenia. The bone marrow specimens of all these patients were examined. The bone marrow was aspirated from the posterior superior iliac spine. Three sets of smears were made. One set of thin smears was stained by Leishman's stain after air-drying and the second set of thin smears was air-dried, fixed with 97% methanol and later stained with 5% Giemsa stain. The third set of smears was a thick smear stained unfixed with 5% Giemsa stain. A temperature of 37 degrees C and a pH of 7.2 was maintained during the staining process. The presence of malarial parasite in the bone marrow was determined. Besides, the degree of megaloblastic change in erythroid series and the bone marrow cellularity were evaluated. The results obtained were recorded and statistically analyzed. RESULTS: Of the 80 bone marrows examined, 32(40%) showed the presence of malarial parasites, 19(23.75%) showed haematological malignancies, 16(20%) showed bone marrow suppression while 12(15%) showed megaloblastic changes. One (1.25%) case showed Leishman-Donovan bodies. Out of 32 cases showing the presence of malarial parasite in bone marrow, only 5(15.6%) revealed parasites, i.e. Plasmodium falciparum gametocytes on thin smear while 32(100%) cases showed Plasmodium falciparum trophozoites and gametocytes on thick smear. The ratio was 1:6.4. These 32 patients were divided into two groups, one group having mild anaemia (>8 g/dL) and the other severe anaemia (Hb<8 g/dL). In this study 20 patients had mild and 12 had severe anaemia. Megaloblastic changes were seen in 15 cases. Hypocellularity was seen in 3 patients with falciparum malaria while 28 showed normocellularity. The marrow was hypercellular in one patient. CONCLUSION: In patients presenting with prolonged fever, splenomegaly and pancytopenia, the Giemsa stained thick smear of bone marrow aspirates for evidence of malarial parasites was far superior to thin smear in diagnosing Plasmodium falciparum malaria.