Chitosan-based adsorptive membrane modified by carboxymethyl cellulose for heavy metal ion adsorption: Experimental and density functional theory investigations.

Low adsorption capacity and weak mechanical stability are the main drawbacks of chitosan (CS)-based adsorptive membranes for heavy metal ion removal. Polyvinyl alcohol (PVA) has been used to improve the mechanical stability of CS membranes, but adsorption capacity is disregarded. In the current study, the surface of the chitosan/polyvinyl alcohol (CP) membrane was modified using carboxymethyl cellulose (CMC) to increase its heavy metal ion adsorption capacity. Experimental and density functional theory (DFT) calculations were used to evaluate the heavy metal ion (As3+ and Cr3+) adsorption capabilities of CP and carboxymethyl cellulose-functionalized CP (CMC-CP) membranes. The batch adsorption process presented a higher heavy metal adsorption capacity of the CMC-CP membrane (As3+/CMC-CP = 234.78 mg/g and Cr3+/CMC-CP = 230.12 mg/g) compared to the CP membrane (As3+/CP = 89.02 mg/g and Cr3+/CP = 75.61 mg/g). The heavy metal/CMC-CP complexes confirmed higher adsorption energies (As3+/CMC-CP = -23.62 kcal/mol and Cr3+/CMC-CP = -23.21 kcal/mol) than the heavy metal/CP complexes (As3+/CP = -3.47 kcal/mol and Cr3+/CP = -2.92 kcal/mol). The electronic band structure was higher for CMC-CP (5.42 eV) compared to CP (4.43 eV). Experimental and theoretical findings were close, implying that the CMC-CP membrane has superior heavy metal adsorption capability than the CP membrane.

Theoretical design of transition metal-doped oxo-triarylmethyl as a disposable platform for adsorption of ibuprofen.

Emerging environmental contaminants have become a crucial environmental issue because of the highly toxic effluents emitted by factories. Ibuprofen (IBP), as a typical anti-inflammatory drug, is frequently detected in water sources. Therefore, its removal using various adsorbents has drawn great interest. Herein, the structural, electronic, energetic, and optical properties of pristine oxo-triarylmethyl (oxTAM) and transition metal-doped oxo-triarylmethyl (TM@oxTAM, TM = Sc, Ti, V, Cr, and Mn) for adsorption of the IBU drug were investigated using density functional theory (DFT) calculations implemented in Gaussian and VASP codes. Frontier molecular orbital (FMO), density of states (DOS), and electronic band structure results demonstrated that transition metal-doped oxTAM causes a significant reduction in the energy band gap (Eg) value of pristine oxTAM, with the highest decrease (30.14 %) in the case of Mn@oxTAM. It was found that transition metal doping onto oxTAM leads to an increase in the adsorption energies (1.20-2.64 eV) and charge density between transition metal and IBU. Natural bond orbital (NBO) analysis revealed that charge was effectively transferred from the IBU towards the transition metal, which was further analyzed by charge decomposition analysis (CDA). Furthermore, quantum theory of atoms in molecules (QTAIM), interaction region indicator (IRI), electron localization function (ELF), and radial distribution function (RDF) analyses revealed that the IBU is adsorbed on the Sc@oxTAM surface via covalent interactions, while electrostatic with partially covalent interactions are dominated in other IBU/TM@oxTAM complexes. The results suggest that TM doping on the oxTAM provides a new insight for developing photocatalyst-based covalent organic frameworks (COFs) to remove emerging pollutants in wastewater.

Corrigendum: Radical scavenging capacity, antibacterial activity, and quantum chemical aspects of the spectrophotometrically investigated iridium (III) complex with benzopyran derivative.

[This corrects the article DOI: 10.3389/fphar.2022.945323.].

Radical scavenging capacity, antibacterial activity, and quantum chemical aspects of the spectrophotometrically investigated iridium (III) complex with benzopyran derivative.

A comprehensive aqueous phase spectrophotometric study concerning the trace level determination of iridium (III) by its reaction with benzopyran-derived chromogenic reagent, 6-chloro-3-hydroxy-7-methyl-2-(2'-thienyl)-4-oxo-4H-1-benzopyran (CHMTB), is performed. The complexing reagent instantly forms a yellow complex with Ir (III) at pH 4.63, where metal is bound to the ligand in a ratio of 1:2 as deduced by Job's continuous variations, mole ratio, and equilibrium shift methods. The complex absorbs maximally at 413-420 nm retaining its stability for up to 4 days. An optimum set of conditions have been set with respect to the parameters governing the formation of the complex. Under the set optimal conditions, the Ir (III)-CHMTB complex coheres to Beer's law between 0.0 and 1.5 µg Ir (III) mL-1. The attenuation coefficient and Sandell's sensitivity are, respectively, 1.18×105 L mol-1 cm-1 and 0.00162 µg cm-2 at 415 nm. The correlation coefficient (r) and standard deviation (SD) were 0.9999 and ± 0.001095, respectively, whereas the detection limit as analyzed was 0.007437 µg ml-1. The interference with respect to analytically important cations and complexing agents has been studied thoroughly. It is found that the majority of the ions/agents do not intervene with the formation of the complex, thus adding to the versatility of the method. The results obtained from the aforesaid studies indicate a simple, fast, convenient, sensitive, and versatile method for microgram analysis of iridium (III) using CHMTB as a binding ligand. Furthermore, the studied complex is subjected to the evaluation of antibacterial and antioxidant capacity by employing the Agar Diffusion assay and DPPH. radical scavenging method, respectively. The results obtained from the mentioned assays reveal that the investigated complex possesses significant potency as an antibacterial and antioxidant agent. Finally, the computational approach through DFT of the formed complex confirmed the associated electronic properties of the studied complex.

A DFT study on the metal ion selectivity of deferiprone complexes.

In this work, systematic density functional theory (DFT) calculations were performed to study the interactions of various metal ions (Al3+, Fe3+, Co2+, Ni2+, Cu2+, and Zn2+) and the clinically useful chelating agent called deferiprone (DFP) at the M05-2X/6-31G(d) level of theory. The thermodynamic parameters of metal-deferiprone complexes were determined in water. Based on the obtained data, the theoretical binding energy trend is as follows: Al3+ > Fe3+ > Cu2+ > Ni2+ > Co2+ > Zn2+, confirming that [Al(DFP)3] has the most interaction energy. Moreover, Natural bond orbital analysis was employed to determine and analyze the natural charges on different atoms and charge transfer between the metal ions and ligands (oxygen atoms) as well as the interaction energy (E(2)) values. The calculated value of Æ©E(2) (donor-acceptor interaction energy) for [Al(DFP)3] complex is higher than other complexes, which is according to energy analysis. To confirm the type of effective interactions and bonding properties in the water, the quantum theory of atoms in molecules (QTAIM) analysis was applied. QTAIM analysis confirmed that the strongest M - O bond is found in the [Al(DFP)3] complex. The calculated topological properties at the bond critical points, such as the ratio of the kinetic energy density to the potential energy density, -G(r)/V(r), electronic energy density, H(r), confirm that M - O bonds in the Al-deferiprone complex are non-covalent, while in other complexes, they are electrostatic and partially covalent.

Investigation of Adsorption Tyrphostin AG528 Anticancer Drug Upon the CNT(6,6-6) Nanotube: A DFT Study.

OBJECTIVE: In the present study, the interaction between drug Tyrphostin AG528 and CNT(6,6-6) nanotube by Density Functional Theory (DFT) calculations in solvent water has been investigated for the first time. METHODS AND RESULTS: According to the calculations, intermolecular hydrogen bonds take place between an active position of the molecule Tyrphostin AG528 and hydrogen atoms of the nanotube which play an important role in the stability of complex CNT(6,6- 6)/Tyrphostin AG528. The non-bonded interaction effects of the molecule Tyrphostin AG528 with CNT(6,6-6) nanotube on the electronic properties, chemical shift tensors and natural charge have also been detected. The natural bond orbital (NBO) analysis suggested that the molecule Tyrphostin AG528 as an electron donor and the CNT(6,6-6) nanotube play the role of an electron acceptor at the complex CNT(6,6-6)/Tyrphostin AG528. CONCLUSION: The electronic spectra of the Tyrphostin AG528 drug and complex CNT(6,6-6)/Tyrphostin AG528 in solvent water were calculated by Time-Dependent Density Functional Theory (TD-DFT) for the investigation of adsorption effect of the Tyrphostin AG528 drug over nanotube on maximum wavelength. Then, the possibility of the use of CNT(6,6-6) nanotube for Tyrphostin AG528 delivery to the diseased cells has been established.

DFT investigation on the selective complexation of Fe3+ and Al3+ with hydroxypyridinones used for treatment of the aluminium and iron overload diseases.

The chelating agents for Al3+ and Fe3+ metal cations with therapeutic applications have been considered in the recent years. In designing of the hydroxypyridinones (HPOs) as the therapeutic chelating agents for iron and aluminium overload pathologies, quantum mechanical (QM) calculations are necessary for predicting the binding energies and thermodynamic parameters of the metal-HPO complexes. Three derivatives of the HPOs called 3-hydroxy-1,2-dimethylpyridin-4(1H)-one (DFP), 3-hydroxy-4(1H)-pyridinone (HOPO) and 5-hydroxy-2-(hydroxymethyl)pyridin-4(1H)-one (P1) were investigated for complexation with Fe3+ and Al3+ metal ions. Because of the maximum interaction between Fe3+ and HPOs, all HPOs form stable complexes with Fe3+ metal ion. Moreover, it was found that [Fe-P1]2+ is a more stable complex than [Fe-DFP]2+ and [Fe-3,4-HOPO]2+ in the gas phase and water, confirming that P1 is the strongest selective iron chelator. The more stability of [Fe-P1]2+ was attributed to an intramolecular hydrogen bond formation between the hydrogen atom of NH group and the oxygen atom of CH2OH chain. All complexes of the HPOs with Fe3+ and Al3+ were formed through the oxygen atoms of the CO and OH groups of the HPO. Natural bond orbital analysis showed that the interaction of the lone pair electrons of the oxygen atom of the chelator and antibonding orbitals of the Al3+ and Fe3+ are important in the complex formation. Topological parameters at the bond critical points confirmed the effective interaction between the Al3+ and Fe3+ metal ions and HPO as well as the nature of the metal-oxygen bonds.

A DFT study on the complex formation between desferrithiocin and metal ions (Mg2+, Al3+, Ca2+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+).

In recent years, Metal-chelating compounds, namely siderphores have been considered very much because of their crucial role in various fields of the environmental researches. Their importance lies in the fact that they are able to be bonded to a variety of metals in addition to iron. A theoretical study on the structures of desferrithiocin siderphore coordinated to Mg2+, Al3+, Ca2+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+ metal ions was carried out, using the CAM-B3LYP/6-31G(d) level of the theory in the water. In order to understand the factors which control the stability, reactivity and the strength of toxic metals excretion as well as microbial uptake of the metal-siderphore complexes, we examined the stability and binding energies of the desferrithiocin and various metal ions with different spin states. The binding affinity of desferrithiocin to Fe3+ (log ß2=23.88) showed that the desferrithiocin can scavenge the excess iron(III) from the labile sources. Also, the binding energy values were well described by addition of the dispersion-corrected D3 functional. Because of the importance of the charge transfer in the complex formation, donor-acceptor interaction energies were evaluated. Based on this analysis, an increase in the effective nuclear charge increases E(2) values. Vibrational analysis showed that the critical bonds (CO stretching and CH bending) are in the range of 1300-1800cm-1. Finally, some probable correlations between the complexation behavior and quantum chemistry descriptors have been analyzed.