DFT Study of Molecular and Electronic Structure of Y, La and Lu Complexes with Porphyrazine and Tetrakis(1,2,5-thiadiazole)porphyrazine

Abstract

Electronic and geometric structures of Y, La and Lu complexes with porphyrazine (Pz) and tetrakis(1,2,5-thiadiazole)porphyrazine (TTDPz) were investigated by density functional theory (DFT) calculations and compared. The nature of the bonds between metal atoms and nitrogen atoms has been described using the analysis of the electron density distribution in the frame of Bader’s quantum theory of atoms in molecule (QTAIM). Simulation and interpretation of electronic spectra were performed with use of time-dependent density functional theory (TDDFT) calculations. Description of calculated IR spectra was carried out based on the analysis of the distribution of the potential energy of normal vibrations by natural vibrational coordinates.

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Synthesis of Fe3O4@chitosan@ZIF-8 towards removal of malachite green from aqueous solution: Theoretical and experimental studies

Discharges of dyes-containing wastewater from industries have created global concern. Removal of these substances from aqueous solution is very important and essential. Magnetic chitosan coated with ZIF-8 was prepared successfully and used to eliminate cationic dye malachite green in various conditions. To find the effectiveness of ZIF-8 towards malachite green removal, their surface interaction was investigated using density functional theory (DFT) calculations for the first time which the results show physisorption of malachite green on ZIF-8. The characteristics of adsorbent synthesized were evaluated using XRD, FTIR, FE-SEM, TEM and TGA analysis. In addition, the influence of different parameters on malachite green removal was investigated. The results showed that pH = 7, 40 mg of adsorbent dosage, 10 mg/L initial concentration, 40 min contact time and temperature of 25 °C were obtained as an optimum values for Fe₃O₄@chitosan@ZIF-8. The equilibrium data were in good agreement with the Langmuir model having maximum capacity (q_m) value of 3.282 mg/g. The experimental data revealed that the adsorption process obeyed to pseudo-second order kinetic model. It was concluded that Fe₃O₄@chitosan@ZIF-8 can be utilized as an efficient and effective adsorbent for removal of toxic malachite green dye from aqueous solution.

Phosphate sequestration by magnetic La-impregnated bentonite granules: A combined experimental and DFT study

To use the lanthanum hydroxide (La(OH)₃) as a low-cost, highly-efficient, and recyclable adsorbent, it could be embedded on a magnetic substance to improve its physical features and lower the overall cost. Herein, novel millimetric-size magnetic lanthanum-modified bentonite (La-MB) granules were fabricated for P sequestration, and the adsorption performance and mechanisms were systematic studied. The maximum capacity of P uptake by La-MB was up to 48.4 mg/g, which was higher than many previous reported La-based adsorbents. Moreover, the enhanced uptake of P was achieved over a wide pH range (3-9) and in the coexistence of common anions (Cl^-, NO₃^-, and SO₄^2-). Besides, the exhausted La-MB can be effectively regenerated by 5 mol/L NaOH with about 94.5% desorption efficiency and 60.8% uptake capacity remained during 5 cycles. The La-MB also exhibited excellent performance of anti-interference in two kinds of real wastewaters. The postsorption characterization and DFT calculations revealed that the electrostatic interaction and chemical precipitation jointly facilitated phosphate sequestration by La-MB during the rapid sorption phase, while ligand exchange and complexation reaction played more important roles than others during the slow sorption step. The electrostatic interaction not only effectively promoted the ligand exchange, and also further accelerated chemical precipitation via the formation of LaPO₄ during the whole process of phosphate uptake. Overall, millimetric La-MB is considered to have great potential for engineering application, and this work also provides new insights into the molecular-level mechanism of phosphate sequestration by La-MB.

Charge transfer and opto-electronic properties of some newly designed polycatenar discotic liquid crystal derivatives: a DFT study

Herein, we demonstrate effect of substituents on optoelectronic properties of discotic liquid crystals (DLCs) by using density functional theory (DFT) calculations at B3LYP/Lanl2Z level of theory. Three parent DLCs, namely, (1) benzene-1,3,5-triyl tris(3,5-dialkoxybenzoate), (2) N¹, N³, N⁵-tris(3-alkoxyphenyl)benzene-1,3,5-tricarboxamide, and (3) trialkyl 4, 4', 4″-(benzenetricarbonyltris (azanediyl)) tribenzoate benzoate and their -N and -S group derivatives of 1, 2, and 3, were investigated to observe the change in optoelectronic response of these systems. The frontier molecular orbital studies and electron affinity values indicate that the studied compounds are stable against the oxygen and moisture present in air. The calculated charge transfer integrals, electron, and hole mobility values revealed that parent DLCs and their derivatives can be employed as an effective n-type material for OLEDs; however, derivatives have enhanced charge transfer values compared with their parents. For better understanding of the thermochemistry and effect of substituents, frequency calculations were carried out. P₁-D₄ derivative having R = -NH-CO-CH₃ terminal group came out to be theoretically the most favored having the lowest ΔG value. Computed UV/visible spectroscopic analysis showed minimum absorbance and maximum transmittance for derivative P₂-D₁ having -S-NH₂ substituent. Molecular electrostatic potential surfaces mapped at potential range, i.e., - 8.531e-3esu to + 8.531e-3esu, describe electrophilic and nucleophilic characteristics. Introduction of electron donor groups enhanced electrical conductivity, excitation energy, and charge transfer integral, thus increasing optoelectronic properties of DLCs. However, these claims require further experimental verification.

Thermally Stable Nitrothiacalixarene Chromophores: Conformational Study and Aggregation Behavior

Achieving high thermal stability and control of supramolecular organization of functional dyes in sensors and nonlinear optics remains a demanding task. This study was aimed at the evaluation of thermal behavior and Langmuir monolayer characteristics of topologically varied nitrothiacalixarene multichromophores and phenol monomers. A nitration/azo coupling alkylation synthetic route towards partially O-substituted nitrothiacalixarenes and 4-nitrophenylazo-thiacalixarenes was proposed and realized. Nuclear magnetic resonance (NMR) spectroscopy and X-ray diffractometry of disubstituted nitrothiacalix[4]arene revealed a rare 1,2-alternate conformation. A synchronous thermal analysis indicated higher decomposition temperatures of nitrothiacalixarene macrocycles as compared with monomers. Through surface pressure/potential-molecular area measurements, nitrothiacalixarenes were shown to form Langmuir monolayers at the air–water interface and, through atomic force microscopy (AFM) technique, Langmuir–Blodgett (LB) films on solid substrates. Reflection-absorption spectroscopy of monolayers and electronic absorption spectroscopy of LB films of nitrothiacalixarenes recorded a red-shifted band (290 nm) with a transition from chloroform, indicative of solvatochromism. Additionally, shoulder band at 360 nm was attributed to aggregation and supported by gas-phase density functional theory (DFT) calculations and dynamic light scattering (DLS) analysis in chloroform–methanol solvent in the case of monoalkylated calixarene 3. Excellent thermal stability and monolayer formation of nitrothiacalixarenes suggest their potential as functional dyes.

Reactivity and Stability of Metalloporphyrin Complex Formation: DFT and Experimental Study

The interaction of three cationic porphyrins—meso-tetrakis (N-methylpyridinium-4-yl) porphyrin (TMPyP), meso-tetrakis (1,3-dimethylimidazolium-2-yl) porphyrin (TDMImP), and meso-tetrakis (1,2-dimethylpyrazolium-4-yl) porphyrin (TDMPzP)—with five heavy metals was studied computationally, and binding constants were calculated based on data obtained by an experimental method and compared. The reactivity and stability of their complexes formed with lead, cadmium, mercury, tin, and arsenic ions were observed in DFT global chemical reactivity descriptors: the electronic chemical potential (µ), chemical hardness (η), and electrophilicity (ω). The results show that M-TDMPzP has higher chemical hardness and lower electrophilicity compared to M-TMPyP and M-TDMImP, indicating the reaction of TDMPzP with metals will form a more stable complex. Specifically, Cd-TDMPzP complexes can stabilize the system, with a lower energy and electronic chemical potential, higher chemical hardness, smaller electrophilicity, and higher binding constant value compared to Pb-TDMPzP and Hg-TDMPzP. This result suggests that the interaction of the Cd²⁺ ion with TDMPzP will produce a stable complex.

Characterization and Evaluation of the Solubility and Oral Bioavailability of Rutin-Ethanolate Solvate

Rutin has many biological activities, but poor solubility and absorption limit its oral application. This study aimed to investigate the characterization of metastable rutin-ethanolate and its solubility and oral bioavailability. In this research, a soluble rutin/CH₃CH₂OH solvate (Form Π) was prepared by solvent crystallization. High-performance liquid chromatography, gas chromatograph, and ¹H-NMR showed that Form Π was formed by rutin and ethanol in a molar ratio of 1:1. The changes of Fourier transform infrared spectroscopy and ¹H-NMR spectrum and the density functional theory (DFT) calculation predicted hydrogen bond formation between 4'-O of rutin and -OH of ethanol. The results of morphology, solid state CP/MAS ¹³C-NMR, X-ray diffraction, and differential scanning calorimetry (DSC) revealed that Form Π is a novel polymorph that differs from Form Ι (rutin trihydrate). Form Π can be stored for a long time under sealed and dry conditions at 40°C but would gradually transform into Form Ι under humid conditions. Although Form Π is a new metastable polymorph relative to Form Ι, Form Π has better solubility and faster dissolution rate. Moreover, the bioavailability of Form Π was 2.04 times higher than that of Form Ι. This outcome implied that Form Π would be a prospective raw material of oral preparation.

In-silico prediction of novel drug-target complex of nsp3 of CHIKV through molecular dynamic simulation

Literature reported that nsp3 of CHIKV is an important target for the designing of drug as it involves in the replication, survival etc. Herein, about eighteen million molecules available in the ZINC database are filtered against nsp3 using RASPD. Top five hit drug molecules were then taken from the total screened molecules (6988) from ZINC database. Then, a one pot-three components reaction is designed to get the pyrazolophthalazine and its formation was studied using DFT method. Authors created a library of 200 compounds using the product obtained in the reaction and filtered against nsp3 of CHIKV based on docking using iGEMDOCK, a computational tool. Authors have studied the best molecules after applying the the Lipinski's rule of five and bioactive score. Further, the authors took the best compound i.e. CMPD178 and performed the MD simulations and tdMD simulations with nsp3 protease using AMBER18. MD trajectories were studied to collect the information about the nsp3 of CHIKV with and without screened compound and then, MM-GBSA calculations were performed to calculate change in binding free energies for the formation of complex. The aim of the work is to find the potential candidate as promising inhibitor against nsp3 of CHIKV.

Para-Selective Cyanation of Arenes by H-Bonded Template

The significance of site selective functionalization stands upon the superior selectivity, easy synthesis and diverse product utility. In this work, we demonstrate the para-selective introduction of versatile nitrile moiety, enabled by a detachable and reusable H-bonded auxiliary. The methodology holds its efficiency irrespective of substrate electronic bias. The conspicuous shift in the step energetics was probed by both experimental and computational mechanistic tools, which heralds the inception of para-deuteration. The synthetic impact of the methodology was highlighted with reusability of directing group and post synthetic modifications.

Synthesis, density functional theory study and in vitro antimicrobial evaluation of new benzimidazole Mannich bases

The tri-component synthesis of novel chiral benzimidazole Mannich bases, by reaction between benzimidazole, aqueous 30% formaldehyde and an amine, the biological evaluation and DFT studies of the new compounds are reported here. The ¹H-NMR, ¹³C-NMR, FTIR spectra and elemental analysis confirm the structures of the new compounds. All synthesized compounds were screened by qualitative and quantitative methods for their in vitro antibacterial activity against 4 bacterial strains. DFT studies were accomplished using GAMESS 2012 software and HOMO-LUMO analysis allowed the calculation of electronic and structural parameters of the chiral Mannich bases. The geometry of 1-methylpiperazine, the cumulated Mullikan atomic charges of the two heteroatoms and of the methyl, and the value of the global electrophilicity index (ω = 0.0527) of the M-1 molecule is correlated with its good antimicrobial activity. It was found that the presence of saturated heterocycles from the amine molecule, 1-methyl piperazine and morpholine, respectively, contributes to an increased biological activity, compared to aromatic amino analogs, diphenylamino-, 4-nitroamino- and 4-aminobenzoic acid. The planarity of the molecules, specific bond lengths and localization of HOMO-LUMO orbitals is responsible for the best biological activities of the compounds.

The mechanism of the reaction between MAO and TMA: DFT study of the electronic structure and characterization of transition states for [AlOMe]6, [AlOMe]9 and [AlOMe]16 cages

Methylaluminoxane (MAO) and trimethylaluminium (TMA) are relevant compounds in organometallic catalysis. Despite many published studies, aspects of their interaction persist an unsolved puzzle. Hence, in this work, we used quantum mechanic approaches based on density functional theory to study this topic. Our calculations revealed that interaction between MAO and TMA occurs initially by the formation of an intermediary Lewis adduct. In agreement with the latent acidity concept, the activation energy for the tensioned Al-O bond break is small, and changes with the local environment of the MAO cages. Breakage of bond belonging to two square faces requires between 4.20 and 5.80 kcal/mol, whereas square-hexagonal faces demand 0.61-9.43 kcal/mol. The products of this reaction present a terminal, acidic 3-coordinate aluminum atom, that can be capped by another TMA molecules. However, our computations suggest that entropic effects may prevent this reaction from occurring at all these sites in the MAO models studied. Additionally, we also characterize the inter/intramolecular methane elimination mechanism. These reactions are not feasible at room temperature but may occur at high temperatures.

DFT Study of Molecular and Electronic Structure of Ca(II) and Zn(II) Complexes with Porphyrazine and tetrakis(1,2,5-thiadiazole)porphyrazine

Electronic and geometric structures of Ca(II) and Zn(II) complexes with porphyrazine (Pz) and tetrakis(1,2,5-thiadiazole)porphyrazine (TTDPz) were investigated by density functional theory (DFT) calculations and compared. The perimeter of the coordination cavity was found to be practically independent on the nature of a metal and a ligand. According to the results of the natural bond orbital (NBO) analysis and quantum theory of atoms in molecules (QTAIM) calculations, Ca-N bonds possess larger ionic contributions as compared to Zn-N. The model electronic absorption spectra obtained with the use of time-dependent density functional theory (TDDFT) calculations indicate a strong bathochromic shift (~70 nm) of the Q-band with a change of Pz ligand by TTDPz for both Ca and Zn complexes. Additionally, CaTTDPz was synthesized and its electronic absorption spectrum was recorded in pyridine and acetone.

Synthesis of ZnO nanoparticle-anchored biochar composites for the selective removal of perrhenate, a surrogate for pertechnetate, from radioactive effluents

Pertechnetate (TcO₄-) is a component of low-activity waste (LAW) fractions of legacy nuclear waste, and the adsorption removal of TcO₄- from LAW effluents would greatly benefit the site remediation process. However, available adsorbent materials lack the desired combination of low cost, radiolytic stability, and high selectivity. In this study, a ZnO nanoparticle-anchored biochar composite (ZBC) was fabricated and applied to potentially separate TcO₄- from radioactive effluents. The as-synthesized material exhibited γ radiation resistance and superhydrophobicity, with a strong sorption capacity of 25,916 mg/kg for perrhenate (ReO₄-), which was used in this study as a surrogate for radioactive pertechnetate (TcO₄-). Additionally, the selectivity for ReO₄- exceeded that for the competing ions I-, NO₂-, NO₃-, SO₄^2-, PO₄^3-, Cu²⁺, Fe³⁺, Al³⁺, and UO₂²⁺. These unique features show that ZBC is capable of selectively removing ReO₄- from Hanford LAW melter off-gas scrubber simulant effluent. This selectivity stems from the synergistic effects of both the superhydrophobic surface of the sorbent and the inherent nature of sorbates. Furthermore, density functional theory (DFT) calculations indicated that ReO₄- can form stable complexes on both the (100) and (002) planes of ZnO, of which, the (002) complexes have greater stability. Electron transfer from ReO₄- on (002) was greater than that on (100). These phenomena may be because (002) has a lower surface energy than (100). Partial density of state (PDOS) analysis further confirms that ReO₄- is chemisorbed on ZBC, which agrees with the findings of the Elovich kinetic model. This work provides a feasible pathway for scale-up to produce high-efficiency and cost-effective biosorbents for the removal of radionuclides.

Catalyst-Free Regioselective [3+2] Cycloadditions of α,β-unsaturated N-arylnitrones with Alkenes to Access Functionalized Isoxazolidines: A DFT Study

The catalyst-free regioselective [3+2]-cycloaddition of α,β-unsaturated N-arylnitrones with alkenes are developed. The series of synthetically important functionalized isoxazolidines are prepared in good to excellent yields by step economic pathway under ligand and transition-metal-free conditions. The regioselective cycloaddition pathway supported by control experiment and computational study.

A coumarin-based turn-on chemosensor for selective detection of Zn(II) and application in live cell imaging

A 2-oxo-2H-chromene-3-carbohydrazide (CHB) was synthesized by the reaction of salicylaldehyde with diethyl malonate and hydrazine hydrate. The recognition behaviors of CHB to Zn²⁺ were investigated and the results showed that CHB exhibits well selectivity and sensitivity to Zn²⁺ with fast response in PBS (pH = 7.24, 60% DMF), the co-existed cations and anions could not interfere the recognition between CHB and Zn²⁺. Besides, the detection limit of CHB for Zn²⁺ was calculated to be 0.95 μM. Furthermore, DFT, EI-MS data and Job's plot were applied for determining the sensing mechanism of CHB with Zn²⁺ and the results showed that a type of 2:1 complex was formed between CHB and Zn²⁺ with the binding constant was 1.32 × 10⁴ M^-2. At last, probe CHB was successfully applied for the imaging of Zn²⁺ in living cells.

Mitochondria-targeting turn-on fluorescent probe for HClO detection and imaging in living cells

Hypochlorous/hypochlorite (HClO/ClO^-), one of the most important signal molecule, plays a crucial role in many cellular signaling pathways. It is reported that the HClO/ClO^- level in mitochondria is important to maintain the normal mitochondrial function. Herein, we present two simple fluorescent probes BAC and mitochondria-targeting fluorescent probe TACB for the detection of ClO^-. Probes BAC &TACB could be sensitively and selectivity detecting ClO^- at the nanomolar levels with the detection limit of 1.64 × 10^-9 M and 9.86 × 10^-8 M, respectively. Additionally, probes BAC &TACB with the response unit of CO moiety could selectively detect ClO^- over other various analytes such as anions, metal ions and OH, ¹O₂, H₂O₂. The response time of probe TACB for ClO^- (<20 s), implying that it could offer a real-time analytical assay of ClO^-. Finally, probe BAC was used for monitoring the ClO^- in HEK293T cells and probe TACB could be utilized to track the fluctuations of exogenous ClO^- levels in the mitochondria of Hela cells.

Anion Recognition by Neutral and Cationic Iodotriazole Halogen Bonding Scaffolds

A computational study of the iodide discrimination by different neutral and cationic iodotriazole halogen bonding hosts was carried out by means of Density Functional Theory. The importance of the size of the scaffold was highlighted and its impact observed in the binding energies and intermolecular X···I distances. Larger scaffolds were found to reduce the electronic repulsion and increase the overlap between the halide electron lone pair and the corresponding I-C antibonding orbital, increasing the halogen bonding interactions. Additionally, the planarity plays an important role within the interaction, and can be tuned using hydroxyl to perform intramolecular hydrogen bonds (IMHB) between the scaffold and the halogen atoms. Structures with IMHB exhibit stronger halogen bond interactions, as evidenced by the shorter intramolecular distances, larger electron density values at the bond critical point and more negative binding energies.

Density functional and experimental study of NO/O2 on zigzag char

In this paper, quantum chemistry computation (density functional theory) of multi-air-staged combustion was investigated in combination with experiment. It was found that the presence of oxygen in the combustion environment has a great influence on the surface chemistry of coal char. In the reaction pathway, the ring-opening reaction happens first, and is followed by NO adsorption. Afterwards, the ring-closure reaction takes place, leaving the nitrogen atom trapped in the inner char molecule. This reaction route effectively inhibits NO formation and achieves the aim of controlling NO emissions. In the staged combustion experiments, the consumption of O₂/NO was accompanied by an increase in the CO₂ concentration. The quantum chemistry computation successfully interprets the recent experimental trends displayed in multi-air-staged combustion.

Synthesis, DNA/BSA binding studies and in vitro biological assay of nickel(II) complexes incorporating tridentate aroylhydrazone and triphenylphosphine ligands

Two new nickel (II) triphenylphosphine complexes derived from tridentate aroylhydrazone ligands [H2L1 = 2-hydroxy-3-methoxybenzylidene)benzohydrazone and H2L2 = N'-(2-hydroxy-3-methoxybenzylidene)-2-hydroxybenzoylhydrazone] and triphenylphosphine were prepared and their molecular structures were determined by single crystal X-ray diffraction analysis. Both nickel(II) complexes showed slightly distorted square planar geometry with one tridentate aroylhydrazone ligand coordinated through ONO donor atoms and one triphenylphosphine ligand coordinated to the nickel center through the phosphorus atom. DNA interaction studies indicated that both complexes possessed higher affinity to herring sperm DNA (HS-DNA) than the corresponding free aroylhydrazone ligand. Molecular docking investigations showed that both complexes could bind to DNA through intercalation of the phenyl rings between adjacent base pairs in the double helix. Meanwhile, bovine serum albumin (BSA) binding studies revealed the complexes could effectively interact with BSA and change the secondary structure of BSA. Further pharmacological evaluations of the synthesized complexes by in vitro antioxidant assays demonstrated high antioxidant activity against NO· and O2˙- radicals. The anticancer activity of each complex was assessed through in vitro cytotoxicity assays (CCK-8 kit) toward A549 and MCF-7 cancer cell and normal L-02 cell lines. Significantly, the Ni(II) complex derived from H2L1 ligand was found to be more effective cytotoxic toward MCF-7cancerous cell with the IC50 value equaled 9.7 μM, which showed potent cytotoxic activity over standard drug cisplatin. AbbreviationsA549human lung carcinoma cellBSAbovine serum albuminCCK-8Cell Counting Kit-8DFTdensity functional theoryDNAdeoxyribonucleic acidDPPH˙2,2-diphenyl-1-picrylhydrazylH2L12-hydroxy-3-methoxybenzylidene)benzohydrazone N'-(2-hydroxy-3-methoxybenzylidene)-2-hydroxybenzoylhydrazoneH2L2N'-(2-hydroxy-3-methoxybenzylidene)-2-hydroxybenzoylhydrazoneHOMOhighest occupied molecular orbitalIC50the 50% activityL-02human normal liver cellLOMOlowest unoccupied molecular orbital (LUMO)MCF-7human breast carcinoma cellNO˙nitric oxideO2˙-superoxide anionSODsuperoxide dismutaseCommunicated by Ramaswamy H. Sarma.

Synthesis, Antiproliferative, and Antioxidant Evaluation of 2-Pentylquinazolin-4(3H)-one(thione) Derivatives with DFT Study

The current study was chiefly designed to examine the antiproliferative and antioxidant activities of some novel quinazolinone(thione) derivatives 6–14. The present work focused on two main points; firstly, comparing between quinazolinone and quinazolinthione derivatives. Whereas, antiproliferative (against two cell lines namely, HepG2 and MCF-7) and antioxidant (by two methods; ABTS and DPPH) activities of the investigated compounds, the best quinazolinthione derivatives were 6 and 14, which exhibited excellent potencies comparable to quinazolinone derivatives 5 and 9, respectively. Secondly, we compared the activity of four series of Schiff bases which included the quinazolinone moiety (11a–d). In addition, the antiproliferative and antioxidant activities of the compounds with various aryl aldehyde hydrazone derivatives (11a–d) analogs were studied. The compounds exhibited potency that increased with increasing electron donating group in p-position (OH > OMe > Cl) due to extended conjugated systems. Noteworthy, most of antiproliferative and antioxidant activities results for the tested compounds are consistent with the DFT calculations.

Exploring the potential of novel transition metal complexes derived from ONO donor type ligand: a quantum chemical study

In the present quantum chemical investigation, we predict several novel transition metal complexes which are designed using tridentate ONO donor type Schiff base ligand (2-((E)-((Z)-4-hydroxypent-3-en-2-ylidene) amino) phenol). The stable molecular geometries of newly designed metal complexes are obtained using density functional theory (DFT) methods. Several properties including geometrical parameters, energies of frontier molecular orbitals (FMOs), and interaction energies are calculated for optimized metal complexes. The more negative interaction energies illustrate more susceptibilities of the reaction of metal cations with ligand. The charge transfers from ligand to metals are observed in the d⁷ and d⁸ metal complexes while it is seen as backdonation of charge from metal to ligand in the d¹⁰ complexes. The quantum chemical characterizations are performed for calculating UV-visible spectra and IR frequencies for all the designed metal complexes. All designed metal complexes show multiple absorption peaks in UV region ranging from 184 to 376 nm, which are related to metal to ligand and ligand to metal charge transfer processes. The IR frequency analysis shows that the -C=N- stretching frequency of ligand in the region of 1650-1580 cm^-1 is decreased by between 50 and 100 cm^-1, which may assign the coordination of ligand with metal via nitrogen. Moreover, the investigations of nonlinear optical (NLO) polarizabilities among selected complexes show that these complexes may possess good potential for NLO applications. The most interesting results are found about the third-order NLO polarizabilities (γ_||) where the γ_|| amplitudes are found to be 60.01 × 10^-36, 56.48 × 10^-36, 90.04 × 10^-36, and 64.57 × 10^-36 esu for complexes 1, 2, 9, and 10, respectively. Thus, we believe that the present investigation may bring the newly designed metal complexes in the limelight of scientific interest for their practical realization in optical and nonlinear optical applications. Graphical abstract Several novel transition metal complexes are designed using tridentate ONO donor type Schiff base ligand as efficient NLO materials.

Ag-Bridged Z-Scheme 2D/2D Bi5FeTi3O15/g-C3N4 Heterojunction for Enhanced Photocatalysis: Mediator-Induced Interfacial Charge Transfer and Mechanism Insights

Heterojunction photocatalysts have attracted widespread interest in photocatalysis because of their high-efficiency interfacial charge-transfer characteristics of nanoarchitectures. In this study, Ag-bridged 2D/2D Bi₅FeTi₃O₁₅/ultrathin g-C₃N₄ Z-scheme heterojunction photocatalysts with powerful interfacial charge transfer has been synthesized via a facile ultrasound method coupled with a photoreduction strategy for efficient photocatalytic degradation of antibiotics. The morphology analysis displays that the bridged Ag nanoparticles were anchored on the interface of layered Bi₅FeTi₃O₁₅ and ultrathin g-C₃N₄ nanosheets. Owing to its unique 2D/2D ternary heterostructure, the Bi₅FeTi₃O₁₅/2%Ag/10% ultrathin g-C₃N₄ composite exhibited the best tetracycline degradation performance under visible-light and simulated solar irradiation. Meanwhile, the intermediates and degradation pathways were proposed by a liquid-phase mass spectrometry system. Characterizations and density functional theory studies together verify that the matched band structure of Bi₅FeTi₃O₁₅ and g-C₃N₄ could induce a superfast Z-scheme interfacial charge-transfer path. More importantly, bridged Ag nanoparticles in the 2D/2D heterojunction extended the light absorption range and prolonged the lifetime of photogenerated electron-holes induced by Bi₅FeTi₃O₁₅. This work affords a promising approach for designing multicomponent Z-scheme heterojunction photocatalysts for highly efficient photocatalytic application.

DFT investigation of role of N - H⋯O and N - H⋯π interactions in the stabilization of the hydrogen bonded complexes of anisole with aromatic amines

Theoretical investigations have been performed on hydrogen (H-) bonded complexes of two aromatic amines with anisole to investigate the effect of the methyl substituent on N - H⋯O and N - -H⋯π interactions. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses were done to elucidate the nature of H- bonding. In 1:1 complexes, the total interaction energy of N-methylaniline complex is higher than that of aniline complex. The existence of bond critical point between N-H of amine and oxygen of anisole confirms weak hydrogen bonding. The energy decomposition analysis showed the role of CT in stabilizing complexes.

Study of molecular structure and hydrogen bond interactions in dipfluzine-benzoic acid (DIP-BEN) cocrystal using spectroscopic and quantum chemical method

The purpose of this article is to predict the molecular structure of the cocrystal of dipfluzine-benzoic acid (DIP-BEN) through computational approach (DFT calculations) and validate it using vibrational spectroscopic studies. The molecular structure of the DIP-BEN cocrystal has been predicted by forming models on the basis of the active sites available to form H-bonds between dipfluzine (DIP) and benzoic acid (BEN). Conformational study has been performed and potential energy surface scans are plotted around the flexible bonds of the cocrystal molecule and three stable conformers have been obtained. Quantum theory of atoms in molecules (QTAIM) explains that all the interactions are medium and partially covalent in nature. Natural bond orbital analysis of the second order perturbation theory of the Fock matrix suggests that interactions LP (2) O2 → σ*(O74H75) and LP (2) F1 → σ* (O89H90) are responsible for the stabilization of the molecule. The HOMO and LUMO energies and electronic charge transfer (ECT) confirms that charge flows from BEN to DIP. Global reactivity descriptor parameters suggest that DIP-BEN cocrystal is softer, thus more reactive in comparison to DIP. Local reactivity descriptor parameter is used to predict reactive sites of the cocrystal. The experimental and theoretical results support the formation of cocrystal through strong hydrogen bond (O89H90⋯F1 and O74H75⋯O2) interactions present in cocrystal.

Understanding of the molecular mechanism of the phenylsulfenic acid elimination from nitroalkyl systems

The molecular mechanism of the phenylsulfenic acid elimination from nitroalkyl systems has been explored using M06-2X/6-31++G(d,p) theoretical level. It was found that independently of environment polarity as well as degree of screening of nitroalkyl moiety, these types of reactions proceed via one-step, polar mechanism with asynchronous transition state. According to actual state of knowledge this type of the mechanism should not be treated as "pericyclic". Simultaneously, all attempts for localization of stationary structures which can be related to the hypothetical, stepwise mechanism were not successful.