Density Functional Theoretical Study Research Articles

Synthesis, antioxidant, DNA interaction, electrochemical, and spectroscopic properties of chromene-based Schiff bases: Experimental and theoretical approach

Two chromene-based Schiff base ligands were synthesized by the condensation of 5-hydroxy-2,2-dimethyl-2H-chromene-6-carbaldehyde with 2-aminodiphenylamine and 1,8-diaminonaphthalene: (E)-2,2-dimethyl-6-(((2-(phenylamino)phenyl)imino)methyl)-2H-chromen-5-ol (2) and (E)-6-(((8-aminonaphthalen-1-yl)imino)methyl)-2,2-dimethyl-2H-chromen-5-ol (3). The compounds were characterized by Fourier transform infrared (FT-IR), absorption (UV-Vis) and nuclear magnetic resonance (NMR) spectroscopies, in addition to mass spectrometry (MS) analyses; the results of which were rationalized using density functional theoretical (DFT) calculations. Antioxidant activity of the Schiff bases was determined using the DPPH free radical scavenging and CUPric Ion Reducing Antioxidant Capacity (CUPRAC) assays. Compound 3 (IC50 = 14 μM) showed greater free radical scavenging ability than compound 2 (35 μM), and was also more effective than ascorbic acid and Trolox. DFT studies indicate that the HAT mechanism is favored over SET for DPPH scavenging. Both compounds exhibited stronger Cu(II) ion reducing capacity than Trolox and ascorbic acid with Trolox equivalent activity coefficient (TEAC) values of 2.0 and 1.6 for compounds 2 and 3, respectively. Furthermore, DNA cleavage and binding properties were determined using gel electrophoresis, UV-Vis spectroscopy, and cyclic voltammetry. The compounds showed copper-mediated cleavage of plasmid DNA and strong binding to DNA, with binding constants on the order of 104 M−1. The strength of DNA binding was verified by molecular docking analysis using two DNA models: a B-DNA dodecamer (-8.4 to -9.3 kcal/mol) and a hexamer (-7.8 to -7.9 kcal/mol). Overall, the chromene Schiff bases show promise as antioxidant and DNA binding agents.

Cholesterol-Based B-Ring 2H-Pyran: Synthesis and Reaction Mechanism by Using Density Functional Theoretical Study

Abstract: The steroidal B-ring 2H-pyran 2 is synthesized by reacting steroidal B-ring α,β- unsaturated ketone 1 and 2-cyano-N-methylacetamide by refluxing for 18 h in methanol in the presence of a catalyst, i.e., chitosan. The product is obtained with a yield of 67%. The structure of the final product 2 is confirmed by utilizing IR, Mass, 13C and 1H NMR spectra. The reaction mechanism of the steroidal pyran ring formation is explored in this paper. The reaction pathway is described by using FMO analysis and relative energies of starting material, intermediate, and transition states, calculated by using the theoretical method, i.e., DFT with B3LYP/6-31G(d). It is found that two intermediates are formed throughout the reaction, which undergo a respective transition state (TS1 and TS2). The energy barrier of each step of the reaction is also calculated. It is also concluded that the reaction is endothermic. The green synthetic method reported in this study would be very useful for the synthetic and medicinal chemists involved in the synthesis of biologically important pyran ring-containing heterocyclic compounds.

Water assisted self-assembly of Cu(II)(pyridine-3-carboxylate)2(H2O)4 coordination complexes and pH dependent growth of microtubes around the crystals – X-ray crystallographic, FESEM, spectroscopic and DFT studies

Water assisted self-assembly of the Cu(II)(pyridine-3-carboxylate)2(H2O)4 coordination complex has been characterized through the X-ray crystallographic structural analysis and density functional theoretical studies. The pH dependent growth of microtubes around the crystal was observed within seven days after the formation of the parent crystal. The shape and morphology of the micro-rods obtained at difference pH values have been investigated using FESEM analysis. Fourier transform infrared (FTIR) spectroscopy, UV–Vis spectroscopy and Raman Spectroscopy have been carried out to characterize the synthesized compound.

Synthesis, structure, preliminary antimicrobial and antimalarial studies of 1,1′-(piperazine-1,4-diyl)bis(2-phenylethan-1-one) and its lanthanide, Ce(III), Pr(III), and Nd(III) complexes

A dione ligand, 1,1′-(piperazine-1,4-diyl)bis(2-phenylethan-1-one) derived from the reaction of phenylacetylchloride with piperazine and the lanthanides, Ce(III), Nd(III), and Pr(III) complexes of general formula [LnL(NO3)2]NO3 were synthesized. The compounds were characterized by conventional NMR, Mass Infra-Red and UV–vis spectroscopic techniques, melting point, elemental analysis, conductivity, thermogravimetric analysis, magnetic susceptibility, and single X-ray structure determination of the ligand. In vitro, antimicrobial studies indicated that the ligand is active against Staphylococcus aureus, Bacillus Sublitis, Salmonella typhi, and Streptococcus pneumonae. The Ce(III) and Pr(III) complexes were active against all the microorganisms except A. Niger and Pseudomonas aeruginosa whereas the Ce(III) complex showed activity against Staphylococcus aureus, Bacillus Sublitis, and Streptococcus pneumonae. The In vivo anti-plasmodial assay of infected rats indicated that the ligand and Nd(III), Pr(III) complexes have high antiplasmodial potency in comparison to the antimalarial medicine Artesunate. In corroboration with findings on the enhanced antimicrobial properties of the complexes, binding energies from molecular docking correlated strongly with the inhibition zone diameter for Staphylococcus aureus and density functional theoretical studies suggest the presence of the metals account for the improved properties in the following order: Nd(III) > Pr(III) > Ce(III).

Continuously tunable the phase transition behavior of VO2 by T-doping and the formation of T-T chain (T = Ta, Nb)

Vanadium dioxide (VO2), a typical strongly correlated transition metal oxide, undergoes a fascinating reversible metal-insulator transition (MIT) at 340 K, attracting increasing interest from both scientific and technological perspectives. Nevertheless, achieving a rational regulation of the phase transition temperature (Tc) and gaining a deeper understanding of the modulation mechanism, as well as clarifying the relationship between the dopants and Tc in VO2, remain significant ongoing challenges. In this work, we present a density functional theoretical study on the structural and electronic properties of T-doped (T = Ta, Nb) VO2. The results demonstrate that the introduction of T (T = Ta, Nb) atoms tends to drive the R phase structure towards a dimerized monoclinic-like structure, while the uniformly aligned V–V chains exhibit alternating short and long V–V dimerization feature. Notably, the R phase VO2 appears to be more susceptible to structural perturbations. Moreover, T (T = Ta, Nb) doping concentration, compressive strain and the numbers of T-T chain cause curious changes in the structural evolution and electronic structures of VO2, acting as effective modulation methods for tuning the phase transition temperature. In addition, the Tc of VO2 could be significantly reduced when the concentration of T (T = Ta, Nb) dopant is less than 6.3%. The current results offer valuable insights into the mechanism of the doping driven MIT in T-doped (T = Ta, Nb) VO2, and contribute to a deeper understanding of the relationship between the dopants and phase transition temperature, further providing valuable insights into its metal-insulator transition behavior.

New visible-light-driven Bi2MoO6/Cs3Sb2Br9 heterostructure for selective photocatalytic oxidation of toluene to benzaldehyde

Herein, new Bi2MoO6/Cs3Sb2Br9 heterostructure (BiMo/CSB) was investigated for the first time as a visible-light-driven photocatalyst for C(sp3)–H bond activation using molecular oxygen as a green oxidant and toluene as a model substrate. The optimized BiMo/CSB photocatalyst exhibited enhanced toluene oxidation activity (2,346 μmol g-1h−1), which was almost two- and five-fold that of pristine CSB (1,165 μmol g-1h−1) and BiMo (482 μmol g-1h−1), respectively. The improved photocatalytic performance was essentially attributed to the formation of staggered band energy lineup in the BiMo/CSB hybrid, which promoted S-scheme charge transfer across the BiMo/CSB heterointerface as supported by ultraviolet photoelectron spectroscopy (UPS), density functional theoretical (DFT), time-resolve photoluminescence (TRPL), and photoelectrochemical studies. Spin–trapping electron paramagnetic resonance (EPR) and radical scavenging studies revealed that photoinduced hole, molecular oxygen, and superoxide radical are key active species in this photocatalytic system. The developed BiMo/CSB catalyst provided good selectivity toward benzaldehyde product (94–98 %), presumably due to the inhibiting effect of benzyl alcohol on benzaldehyde oxidation. No significant change in structure and morphology was observed for the spent catalyst, however small negative shift of Sb 3d and Bi 4f binding energy was found suggesting partial reduction of Sb3+ and Bi3+. This work not only provides a new visible-light-driven photocatalyst for C(sp3)–H bond activation but also opens the doors for exploitation of the conversion and functionalization of this inert bond toward the production of high value-added organic chemicals.

Insights into the mechanism in electrochemical CO2 reduction over single-atom copper alloy catalysts: A DFT study

Copper single-atom alloy catalysts (M@Cu SAAs) have shown great promise for electrochemical CO2 reduction reaction (CO2RR). However, a clear understanding of the CO2RR process on M@Cu SAAs is still lacking. This study uses density functional theoretical (DFT) calculations to obtain a comprehensive mechanism and the origin of activity of M@Cu SAAs. The importance of the adsorption mode of M@Cu is revealed: key intermediates either adsorbed in the adjacent hollow site around Cu atoms (AD mode) or adsorbed directly on the top site of M (SE mode). AD mode generally exhibits finely tuned binding strengths of key intermediates, which significantly enhances the activity of the catalysts. Increasing the coverage of ∗CO on the M@Cu with SE mode leads to relocation of the active site, resulting in improved activity of C2 products. The insights gained in this work have significant implications for rational design strategy toward efficient CO2RR electrocatalysts.

Ultrafast excited state dynamics of isocytosine unveiled by femtosecond broadband time-resolved spectroscopy combined with density functional theoretical study.

Isocytosine, having important applications in antivirus and drug development, is among the building blocks of Hachimoji nucleic acids. In this report, we present an investigation of the excited state dynamics of isocytosine in both protic and aprotic solvents, which was conducted by a combination of methods including steady-state spectroscopy, femtosecond broadband time-resolved fluorescence, and transient absorption. These methods were coupled with density functional and time-dependent density functional theory calculations. The results of our study provide the first direct evidence for a highly efficient nonradiative mechanism achieved through internal conversion from the ππ* state of the isocytosine keto-N(3)H form occurring within subpicoseconds and picoseconds following photo-excitation. Our study also unveils a crucial role of solvent, particularly solute-solvent hydrogen bonding, in determining the tautomeric composition and regulating the pathways and dynamics of the deactivation processes. The deactivation processes of isocytosine in the solvents examined are found to be distinct from those of cytosine and the case known for isocytosine in the gas phase mainly due to different tautomeric forms involved. Overall, our findings demonstrate the high photo-stability of isocytosine in the solution and showcase the remarkable effect of covalent modification in altering the spectral character and excited state dynamics of nucleobases.

Combined Experimental and Theoretical Insights on Selectivity of Rare Earth Elements with Tetra‐2‐ethylhexyl Diglycolamide

AbstractA diglycolamide based extractant namely tetra‐2‐ethylhexyl diglycolamide [TEHDGA] has been synthesized and characterized for extraction of rare earths from coal fly ash (CFA). The formation rare earth‐TEHDGA complex in the organic phase was determined from slope analysis method. The same structure was further corroborated by the density functional theoretical calculation. Furthermore, DFT approach was adopted to explain the relative stability of rare earth complex with TEHDGA over other matrix elements like Fe, Ca, Al, Mg of CFA by determining their free energy of extraction. The calculated selectivity trend from the free energy of extraction is obtained after consideration of 1 : 3 stoichiometry for Europium – the representative of all rare earth elements. Thus the correct selectivity order was established from a combined experimental and density functional theoretical studies.

Role of curvature in acridone for 1 O2 oxidation of a natural product homoallylic alcohol: A novel iso-hydroperoxide intermediate.

A density functional theoretical (DFT) study is presented, implicating a 1 O2 oxidation process to reach a dihydrobenzofuran from the reaction of the natural homoallylic alcohol, glycocitrine. Our results predict an interconversion between glycocitrine and an iso-hydroperoxide intermediate [R(H)O+ -O- ] that provides a key path in the chemistry which then follows. Formations of allylic hydroperoxides are unlikely from a 1 O2 'ene' reaction. Instead, the dihydrobenzofuran arises by 1 O2 oxidation facilitated by a 16° curvature of the glycocitrine ring imposed by a pyramidal N-methyl group. This curvature facilitates the formation of the iso-hydroperoxide, which is analogous to the iso species CH2 I+ -I- and CHI2 + -I- formed by UV photolysis of CH2 I2 and CHI3 . The iso-hydroperoxide is also structurally reminiscent of carbonyl oxides (R2 C=O+ -O- ) formed in the reaction of carbenes and oxygen. Our DFT results point to intermolecular process, in which the iso-hydroperoxide's fate relates to O-transfer and H2 O dehydration reactions for new insight into the biosynthesis of dihydrobenzofuran natural products.

Synthesis, Spectral, Redox and Theoretical Studies of Stable Nonaromatic Dicarba Dithia Hexaphyrin(2.0.1.1.1.0)s with Two Inverted Thiophenes.

A series of dicarba dithia hexaphyrin(2.0.1.1.1.0)s containing two p-phenylene rings, two thiophene rings, and two pyrrole rings connected via five meso carbons were synthesized by condensing the key precursor, hexapyrrane, which was prepared over a sequence of steps, with the appropriate aromatic aldehyde under acid catalytic conditions followed by alumina chromatographic purification. Detailed one-dimensional (1D) and two-dimensional (2D) NMR studies revealed that the two thiophene rings were inverted and facing outward from the macrocyclic core. Interestingly, one of the inverted thiophene rings adopts a normal orientation in the protonated derivatives of macrocycles generated by addition of trifluoroacetic acid to the appropriate macrocyclic solution. The spectroscopic studies support the non-aromatic nature of macrocycles, and the macrocycles exhibit a distinct sharp band at ∼425 nm along with a broad band in the range of 550-1000 nm, which experienced a red shift with a clear color change in the protonated derivatives. The redox studies showed lower oxidation potentials, indicating their electron-rich nature. The density functional theoretical (DFT) studies showed that the hexaphyrins adopt oval-shaped structures, and time-dependent-DFT (TD-DFT) studies parallelly matched the experimental observations of macrocycles.

First-principles density functional theoretical study on the structures, reactivity and spectroscopic properties of (NH) and (OH) Tautomer's of 4-(methylsulfanyl)-3[(1Z)-1-(2-phenylhydrazinylidene) ethyl] quinoline-2(1H)-one

The tautomerizations mechanism of 4-(methylsulfanyl)-3[(1Z)-1-(2-phenylhydrazinylidene) ethyl] quinoline-2(1H)-one were inspected in the gas phase and ethanol using density function theory (DFT) M06-2X and B3LYP methods. Thermo-kinetic features of different conversion processes were estimated in temperature range 273–333 K using the Transition state theory (TST) accompanied with one dimensional Eckert tunneling correction (1D-Eck). Acidity and basicity were computed as well, and the computational results were compared against the experimental ones. Additionally, NMR, global descriptors, Fukui functions, NBO charges, and electrostatic potential (ESP) were discussed. From thermodynamics analysis, the keto form of 4-(methylsulfanyl)-3-[(1Z)-1-(2 phenylhydrazinylidene) quinoline-2(1H)-one is the most stable form in the gas phase and ethanol and the barrier heights required for tautomerization process were found to be high in the gas phase and ethanol ~ 38.80 and 37.35 kcal/mol, respectively. DFT methods were used for UV–Vis electronic spectra simulation and the time-dependent density functional theory solvation model (TDDFT-SMD) in acetonitrile compounds.

Enhancement of Fluorescence Mediated by Silver Nanoparticles: Implications for Cell Imaging.

In this study, we report the surface enhanced fluorescence (SEF) of a biologically important organic dye, fluorescein (FL), by silver nanoparticles (Ag NPs) in an aqueous medium and its implications for human cell imaging. The as-synthesized Ag NPs were characterized by dynamic light scattering (DLS), zeta potential, transmission electron microscopy (TEM), and UV-vis absorption spectroscopic studies. The interaction and aggregation of FL dye with Ag NPs and a cationic surfactant, namely, cetyltrimethylammonium bromide (CTAB), were explored by UV-vis absorption and steady-state and time-resolved fluorescence spectroscopic methods. The distance-dependent fluorescence enhancement of FL due to Ag NPs in the solution was also theoretically correlated by three-dimensional finite-difference time-domain (3D-FDTD) simulation. The plasmonic coupling between neighboring NPs facilitated the augmentation of the local electric field, thereby producing various "hotspots" that influence the overall fluorescence of the emitter. J-type aggregates of FL in the presence of the CTAB micelles and Ag NP mixed solution were confirmed by electronic spectroscopy. The density functional theoretical (DFT) study revealed the electronic energy levels associated with different forms of FL dye in the aqueous solution. Most interestingly, the Ag NP/FL mixed system used in fluorescence imaging of human lung fibroblast cells (WI 38 cell line) showed a significantly stronger green fluorescence signal compared to that of FL after an incubation period of only 3 h. This study confirms that the Ag NP mediated SEF phenomenon of the FL dye is also manifested in the intracellular medium of human cells giving a brighter and more intense fluorescence image. The cell viability test after exposure to the Ag NP/FL mixed system was confirmed by the MTT assay method. The proposed study may have an implication as an alternate approach for human cell imaging with higher resolution and more contrast.

Structural, spectroscopic, electronic, Hirshfeld, QTAIM and biological predications of a hybrid 2,6-dichloropurine compound: A detailed density functional theoretical study

Extensive research into the optimized structure, spectroscopic and biological properties of 2,6-dichloropurine (6DCP) was conducted using IR/Raman and NMR techniques, as well as theoretically using the DFT approach with B3LYP, CAM-B3LYP, and PBEPBE function levels at 6-311++G(d, p) basis set. The computational results from DFT approaches such as geometrical, IR/Raman and NMR spectra were compared with the experimental results. All our theoretical calculations were in good agreement with observed data. The electronic HOMO-LUMO, H-bonding and strong conjugative interactions across different molecular entities are discussed to reveal the accompanying pharmaceutical intermediate. The molecular properties such as chemical reactivity descriptors, mapped ESP, dipole moment, mean polarizability, and first order hyperpolarizability of the title molecule were calculated by quantum mechanical calculations. The high value of the electronic dipole moment and polarizability estimate for the 6DCP molecule may improve its biological activity. The NBO study has enabled researchers to investigate hyper-conjugate interactions, intramolecular bonding, and strong H-bonding interactions. Strong H-bonding interaction energies of 120.47 kcal/mol have been performed at the DFT/PBEPBE level.

Optimization of the adsorption of lead (II) by hydroxyapatite using a factorial design: Density functional theory and molecular dynamics

Hydroxyapatite (HAp) synthesized through a wet chemical procedure was used to adsorb lead (II) from an aqueous solution. HAp was characterized using Fourier transform infrared, X-ray diffraction, Brunauer–Emmett–Teller analysis, and scanning electron microscopy. The removal of Pb+2 was investigated using the factorial design approach to investigate the efficiency of different Pb+2 concentrations, adsorption contact time, and HAp mass. The greatest Pb+2 removal (98.94%) was obtained at a starting concentration of 50 mg/L, a contact period of 15 min, and a pH of 8. At 323 K, the isothermal adoption module was fitted to the Langmuir isotherms with a regression coefficient (R2) of 0.96. The thermodynamic calculations revealed that the adsorption process was exothermic, spontaneous, and predominantly dominated by chemisorption. Furthermore, the maximum adsorption capacity (Qmax) at equilibrium was 90.18 mg/g, and the adsorption kinetics was specified by a pseudo-second-order kinetic model. Density functional theory and theoretical studies showed that the results of the experiment were correlated by the observation of a much higher negative Eads value for the lead ion adsorbate molecules as they attached to the surface of the adsorbent.

Fluorenone Appended Colorimetric Sensor for Cascade Detection of Fluoride and Calcium Gluconate with Applications in Solid State and Logic Gate Systems

AbstractA novel fluorenone derived Schiff base chemosensor (1) has been synthesized as a colorimetric sensor for fluoride (F−) ions in CH3CN and characterized by various analytical techniques. The chemosensor 1 perceived high selectivity for F− ion detection in the presence of other anions along with naked eye color change from yellow to orange‐red with quantitative detection limit of 900 nM. The UV‐vis changes, density functional theoretical (DFT) calculations and 1H NMR titration studies pointed to F− ion induced deprotonation of −OH of sensor 1 that has been proposed to be responsible for the observed absorption as well as color changes. The sensor 1 has also been efficiently applied for the solid state concentration dependent naked eye detection of F− ions in the form of filter paper strips and smartphone applications. The in‐situ generated 1‐F− complex was further utilized for cascade recognition of calcium gluconate (CG). The reversible and reproducible changes produced by the addition of F− ions and CG enabled 1 to be used as “INHIBIT” molecular logic system and “SET/RESET” memorized device at the molecular level.

Smart bio-nano interface derived from zein protein as receptors for biotinyl moiety

Proteinaceous, tunable nanostructures of zein (prolamine of corn) were developed as biotinyl-specific receptors using a molecular imprinting technique. Sacrificial templates, such as latex beads (LB3) and anodized alumina membrane (AAM), have been used to control nanostructural patterns in biotin-imprinted zein (BMZ). Briefly, a methanolic solution of the zein-biotin complex was drop cast upon a self-organized LB3 and AAM templates on Au/quartz surfaces. Subsequent dissolution of these sacrificial templates affords highly oriented, predetermined, and uniformly grown hyperporous (300 nm) and nanowires (150 nm) motifs of zein (BMZ-LB3 and BMZ-AAM), as shown by scanning electron microscopy (SEM). Selective extraction of biotin molecular template cast-off site-selective biotin imprints within these zein nanostructures complementary to biotinyl moieties. Alternatively, biotin-imprinted zein nanoparticles (BMZ-Np) and thin film (BMZ-MeOH) were prepared by coacervation and drop casting methods, respectively. Density functional theoretical (DFT) studies reveal strong hydrogen-bonded interaction of biotin with serine and glutamine residues of zein. Quartz crystal microbalance (QCM) studies show remarkable sensitivity of the hyperporous-BMZ-LB3 and nanowires of BMZ-AAM towards biotin derivative (biotin methyl ester) by five (24.75 ± 1.34 Hz/mM) and four (18.19 ± 0.75 Hz/mM) times, respectively, higher than the BMZ-MeOH. Enhanced permeability features of the zein nanostructures, when templated with LB3, enable the QCM detection of biotin- or its derivatives down to 12.9 ng mL−1 from dairy products (Kefir). The outcome of this study shall be a key aspect in interfacing biological materials with micro-/nano-sensors and electronic devices for detecting pertinent analytes using sustainably developed biopolymer-based nanostructures.

CO2 hydrogenation to formic acid on Pd-Cu nanoclusters: a DFT study.

Carbon dioxide (CO2) hydrogenation to formic acid is a promising method for the conversion of CO2 to useful organic products. The interaction of CO2 with hydrogen (H2) on PdmCun (m + n = 4, 8 and 13) clusters to form formic acid (HCOOH) has been explored using density functional theoretical (DFT) calculations. Pd2Cu2, Pd4Cu4 and 13-atom Pd12Cu clusters are found to be the most stable among all of the PdmCun (m + n = 4, 8 and 13) clusters with binding energies of -1.75, -2.16 and -2.40 eV per atom, respectively. CO2 molecules get adsorbed on the Pd2Cu2, Pd4Cu4 and Pd12Cu clusters in an inverted V-shaped way with adsorption energies of -0.91, -0.96 and -0.44 eV, respectively. The hydrogenation of CO2 to form formate goes through a unidentate structure that rapidly transforms into the bidentate structure. To determine the transition state structures and minimum energy paths (MEPs) for CO2 hydrogenation to formic acid, the climbing image nudge elastic band (CI-NEB) method has been adopted. The activation barriers for the formation of formic acid from formate on Pd2Cu2 and Pd4Cu4 are calculated to be 0.79 and 0.68 eV, respectively whereas that on the Pd12Cu cluster is 1.77 eV. The enthalpy for the overall process of CO2 hydrogenation to formic acid on the Pd2Cu2, Pd4Cu4 and Pd12Cu clusters are found to be 0.83, 0.48 and 0.63 eV, respectively. Analysis of the density of states (DOS) spectra show that the 4d orbital of Pd, the 3d orbital of Cu, and the 2p orbitals of C and O atoms are involved in the bonding between CO2 molecules and the Pd2Cu2 clusters. The CO2 adsorption on the PdmCun (m + n = 4 and 8) clusters has also been explained in terms of the charge density distribution analysis.

Dual Responsive Optical Sensor for The Detection of Zn2+and Al3+: Supportive Single‐Crystal X‐ray Structure of its Ni(II) Complex and DFT Studies

AbstractA tripodal pentadentate mono‐imine derivative, 2‐({2‐[bis‐(2‐amino‐ethyl)‐amino]‐ethylimino}‐methyl)‐phenol (L2) is employed for ‘turn on’ fluorescence recognition of Zn2+and Al3+at two different wavelengths. Chelation‐enhanced fluorescence (CHEF) assisted inhibition of excited‐state intramolecular proton transfer (ESIPT) is proposed as the sensing mechanism. The1HNMR, mass, IR spectral data, Jobs experiment and single crystal X‐ray structure of the [Ni(II)‐L2] complex (N1) strongly support the structure of L2 and its interaction with Zn2+and Al3+. Density functional theoretical (DFT) studies indicate higher stability of the Zn2+and Al3+adducts over free L2. The recognition of Zn2+and Al3+at two different emission wavelengths allows to construct a binary logic gate. Moreover, L2 is useful for determination unknown concentration of Al3+in real water samples. The complex N1 catalyses the catechol oxidation reaction.

Aggregation Behavior of Nitrilotriacetamide (NTAmide) Ligands in Thorium(IV) Extraction from Acidic Medium: Small-Angle Neutron Scattering, Fourier Transform Infrared, and Theoretical Studies.

Two tripodal amides obtained from nitrilotriacetic acid with n-butyl and n-octyl alkyl chains (HBNTA(LI) and HONTA(LII), respectively) were studied for the extraction of Th(IV) ions from nitric acid medium. The effect of the diluent medium, i.e., n-dodecane alone and a mixture of n-dodecane and 1-decanol, onto aggregate formation were investigated using small angle neutron scattering (SANS) studies. In addition, the influence of the ligand structure, nitric acid, and Th(IV) loading onto ligand aggregation and third-phase formation tendency was discussed.The LI/LII exist as monomers (aggregarte radius for LI: 6.0 Å; LII:7.4 Å) in the presence of 1-decanol, whereas LII forms dimers (aggregarte radius for LII:9.3 Å; LI does not dissolve in n-dodecane) in the absence of 1-decanol. The aggregation number increases for both the ligands after HNO3 and Th(IV) loading. The maximum organic concentration (0.050 ± 0.004 M) of Th(IV) was reached without third-phase formation for 0.1 M LI/LII dissolved in 20% isodecanol +80% n-dodecane. The interaction of 1-decanol with LII and HNO3/Th(IV) with amidic oxygens of LI/LII results in shift of carbonyl stretching frequency, as shown by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) studies. The structural and bonding information of the Th-LI/LII complex were derived from the density functional theoretical (DFT) studies. The molecular dynamics (MD) simulations suggested that the aggregation behavior of the ligand in the present system is governed by the population of hydrogen bonds by phase modifier around the ligand molecules. Although the theoretical studies suggested higher Gibbs free energy of complexation for Th4+ ions with LI than LII, the extraction was found to be higher with the latter, possibly due to the higher lipophilicity and solubility of the Th-LII aggregate in the nonpolar media.