Original Ligand Research Articles

Efficient CsPbBr3 Perovskite Light-Emitting Diodes via Novel Multi-Step Ligand Exchange Strategy Based on Zwitterionic Molecules.

Perovskite nanocrystals have absorbed increasing interest, especially in the field of optoelectronics, owing to their unique characteristics, including their tunable luminescence range, robust solution processability, facile synthesis, and so on. However, in practice, due to the inherent instability of the traditional long-chain insulating ligands surrounding perovskite quantum dots (PeQDs), the performance of the as-fabricated QLED is relatively disappointing. Herein, the zwitterion 3-(decyldimethylammonio)propanesulfonate (DLPS) with the capability of double passivating perovskite quantum dots could effectively replace the original long-chain ligand simply through a multistep post-treatment strategy to finally inhibit the formation of defects. It was indicated from theexperimental results that the DLPS, as one type of ligand with the bimolecular ion, was very adavntageous in replacing long-chain ligands and further suppressing the formation of defects. Finally, the perovskite quantum dots with greatly enhanced PLQY as high as 98% were effectively achieved. Additionally, the colloidal stability of the corresponding PeQDs has been significantly enhanced, and a transparent colloidal solution was obtained after 45 days under ambient conditions. Finally, the as-fabricated QLEDs based on the ligand-exchanged PeQDs exhibited a maximum brightness of 9464 cd/m2 and an EQE of 12.17%.

Oligomeric Zinc Thiolates Tethering Multidentate Carboxylates for Nondestructive Aqueous Phase Transfer of Quantum Dots.

Functionalization of quantum dots (QDs) via ligand exchange is prone to debase their photoluminescence quantum yield (PL QY) owing to the unavoidable surface damage by excess reactants, and even worse in aqueous medium. Herein, the oligomeric zinc thiolate as the multidentate hydrophilic ligand featuring facile synthetic protocol is proposed. A simple reaction between ZnCl2 and 3-mercaptopropionic acid produces oligomeric ligands containing 3-6 zinc thiolate units, where the terminal moieties provide multidentate anchoring to the surface as well as hydrophilicity. 2D proton nuclear Overhauser effect spectroscopy (2D 1H NOESY) and X-ray photoelectron spectroscopy (XPS) reveal that the oligomeric zinc thiolate ligands adsorb on the surface via multidentate metal carboxylate bindings without destruction of molecular structure, regardless of partial dissociation of thiolate branches in aqueous phase. Enhanced binding affinity granted by the multidentate nature allows for the effective exchange of original surface ligands without considerable surface deterioration. The zinc thiolate-capped Cd-free aqueous QDs exhibit a high photoluminescence quantum yield of ≈90% and extended stability against long-term storage and photochemical stress.

Ligand Exchange of Quantum Dots: A Thermodynamic Perspective.

Colloidal quantum dots (QDs) consist of an inorganic core and organic surface ligands. Surface ligands play a dominant role in maintaining the colloidal stability of QDs and passivating the surface defects of QDs. However, the original ligands introduced in the synthetic process of QDs cannot meet the requirements for diverse applications; therefore, ligand exchanges with functional ligands are mandatory. Understanding the ligand exchange process requires a comprehensive combination of the concepts and techniques of surface chemistry. In this Perspective, the ligand exchange process is discussed in detail. Specifically, we elaborate on the thermodynamics that can reveal the feasibility and mechanism of ligand exchange. It depicts a critical physical picture of the surface of QDs along with the following ligand exchange.

A novel isatin Schiff based cerium complex: synthesis, characterization, antimicrobial activity and molecular docking studies

In this work, a novel isatin-Schiff base L2 had been synthesized through a simple reaction between isatin and 2-amino-5-methylthio-1,3,4-thiadiazole. The produced Schiff base L2 was then subjected to a hydrothermal reaction with cerium chloride to produce the cerium (III)-Schiff base complex C2. Several spectroscopic methods, including mass spectra, FT-IR, elemental analysis, UV–vis, 13C-NMR, 1H-NMR, Thermogravimetric Analysis, HR-TEM, and FE-SEM/EDX, were used to completely characterize the produced L2 and C2. A computer simulation was performed using the MOE software program to find out the probable biological resistance of studied compounds against the proteins in some types of bacteria or fungi. To investigate the interaction between the ligand and its complex, we conducted molecular docking simulations using the molecular operating environment (MOE). The docking simulation findings revealed that the complex displayed greater efficacy and demonstrated a stronger affinity for Avr2 effector protein from the fungal plant pathogen Fusarium oxysporum (code 5OD4) than the original ligand. The antibacterial activity of the ligand and its Ce3+ complex were applied in vitro tests against different microorganism. The study showed that the complex was found to be more effective than the ligand.

Co(II) Metal-Organic Complex: Fluorescence Performances and Loaded With Drug Vitamin B2 Hydrogels Against Recurrent Oral Ulcers.

A new coordination polymer (CP) based on Co(II), namely, {[Co3(L)2(4,4'-bipy)(DMA)2]·H2O}n(1) has been synthesized after reacting Co(NO3)2·6H2O with H3L ligand in the existence of N-donor ligand 4,4'-bipyridine (4,4'-bipy), via utilizing a flexible tricarboxylic acid ligand 5-((formic acid-3-sulfur)methyl)isophthalic acid (H3L) with -S-CH2- joint. Additionally, the excellent blue fluorescence properties of CP 1 were confirmed through fluorescence spectroscopy compared to the original ligand. Using natural polysaccharide hyaluronic acid (HA) and carboxymethyl chitosan (CMCS) as raw materials, HA/CMCS hydrogel was prepared by chemical synthesis method. Taking vitamin B2 as the drug model, we designed and synthesized gels loaded with vitamin B2 metal framework and evaluated their efficacy in the treatment of recurrent oral ulcer.

Synthesis, in vitro antioxidant, anticancer activity and molecular docking of new thiazole derivatives

Nitrogen and sulfur-containing heterocyclic aromatic derivatives play an enormous and important role in the field of medicine and in synthesis of pharmaceutically active compounds. In this study, a series of new 2-[1-(1,3-diphenyl-1H-pyrazol-4-yl)ethylidene]hydrazinyl)-4-methyl-5-aryldiazinyl)-thiazole derivatives (9a–d) was synthesized by an efficient and convenient method by reacting hydrazonoyl chloride derivatives (4) with carbothioamide derivative (3). The structures of these compounds were elucidated using elemental analyses, spectroscopic analyses (IR, NMR, Mass spectrometer) and computational measurements. Density functional theory (DFT) is performed to get the optimized structures with minimization Energy. The main goal of preparing these compounds is to evaluate their in vitro antioxidant and anticancer activities after studying their molecular docking. The docking was performed on compounds (9a–d) against tyrosine kinase (PDB ID: 2HCK). The results revealed that all docked compounds (9a-d) have a higher binding energy, ranging from −7.56 to −8,89 kcal/mol. compared to the original ligand quercetin, which was −5.92 kcal/mol. Moreover, the results of antioxidant and anticancer activity assay methods demonstrated that the tested derivatives (9a-d) exhibited potent antioxidant and anti-tumor activities against HepG2 cell lines.

A chromatographic method for determining the interaction between a drug and two target proteins by fabricating a dual-heterogeneous surface

Characterization of the drug-target interactions is pivotal throughout the whole procedure of drug development. Most of the current assays, particularly, chromatographic methods lack the capacity to reveal drug adsorption on the muti-target surface. To this end, we derived a reliable and workable mathematical equation for revealing drug bindings to dual targets on the heterogeneous surface starting from the mass balance equation. The derivatization relied on the correlation of drug injection amounts with their retention factors. Experimental validation was performed by determining the binding parameters of three canonical drugs on a heterogeneous surface, which was fabricated by fusing angiotensin receptor type I and type II receptors (AT1R and AT2R) at the terminuses of circularly permuted HaloTag (cpHaloTag) and immobilizing the whole fusion protein onto 6-bromohexanoic acid modified silica gel. We proved that immobilized AT1R-cpHalo-AT2R maintained the original ligand- and antibody-binding activities of the two receptors in three weeks. The association constants of valsartan, candesartan, and telmisartan to AT1R were (6.26±0.14) × 105, (9.66±0.71) × 105, and (3.17±0.03) × 105 L/mol. In the same column, their association constants to AT2R were (1.25±0.04) × 104, (2.30±0.08) × 104, and (8.51±0.06) × 103 L/mol. The patterns of the association constants to AT1R/AT2R (candesartan>valsartan>telmisartan) were in good line with the data by performing nonlinear chromatography on control columns containing immobilized AT1R or AT2R alone. This provided proof of the fact that the derivatization allowed the determination of drug bindings on the heterogeneous surface with the utilization of a single series of injections and linear regression. We reasoned that is simple enough to model the bindings of drug adsorption on commercially available adsorbents in fundamental or industrial fields, thus having the potential to become a universal method for analyzing the bindings of a drug to the heterogeneous surface containing multiple targets.

Screening for Q-markers of Antiviral Granules based on neuraminidase inhibitors and Effect-constituent index

BackgroundAntiviral granules (AG) is a classic traditional Chinese medicine commonly employed for influenza treatment. However, there is an urgent need to improve its quality control standards. PurposeThe quality markers (Q-markers), guided by the Effect-constituent Index (ECI), were screened through in vitro and in vivo component identification, molecular docking, and neuraminidase (NA) inhibition experiments. MethodsThe chemical components in AG underwent analysis using UPLC-Q-Orbitrap HRMS and GC–MS, and serum pharmacochemistry was employed to analyze the components absorbed into the bloodstream. Molecular docking was used to evaluate the affinity of the prototype components to NA, and the inhibitory activity of the candidate components was later confirmed through NA inhibitor experiments. Following this, a UHPLC-MS/MS method was developed to screen and quantify the Q-markers in 20 sample batches. Lastly, the ECI was formulated using a multi-index comprehensive evaluation method that combines composition, content, and activity. ResultsA total of 246 compounds were identified in AG, and 89 prototype components and 19 metabolic components were detected in the serum of the rats. Molecular docking revealed that the binding energy of 35 candidate active ingredients was better than that of the original ligand and the target protein. Among these candidate active ingredients, 12 candidate Q-markers demonstrated significant inhibitory effects in NA inhibition experiments, with IC50 values ranging from 0.954 to 3.408 mM. A UHPLC-MS/MS content determination method was established for the quantification of 11 Q-markers, including Forsythiaside A, Pogostone, Verbascoside, Mangiferin, 5-methoxy-8-hydroxypsoralen, Curcumenol, Luteolin-7-glucuronide, Kaempferol-3-O-rutinoside, Baicalin, Rutin, and Bergaptol, in 20 batches of samples. The ECI was calculated based on activity and content of these Q-markers. Pearson's correlation analysis of the NA inhibitory effect of the samples and the ECI resulted in an R value of 0.859, indicating a good correlation. Furthermore, this correlation coefficient surpassed those observed between the content of each Q-marker and the NA inhibitory effect. ConclusionThe Q-markers for treating influenza with AG have been successfully screened, and the ECI of AG has been constructed. These findings will provide beneficial strategies for improving the quality control level of AG.

Molecular Dynamics Simulation of Serotonin Transport Protein Complex with 6-Hydroxy-1-Methyl-1,2,3,4-Tetrahydro-β-Carboline Ligand from Chocolate (Theobroma cacao L.) Isolate

6-hydroxy-1-methyl1,2,3,4-tetrahydro-β-carboline (6OHMTHβC) is a chocolate derivate that has antidepressant potency. It can increase dopamine and serotonin secretion, which leads to mood improvement. This method was carried out using computational molecular docking simulations (in silico). The research design was computational-based exploratory descriptive. The results of molecular docking showed the lowest energy score and the backbone RMSD value ≤2Å. The procedure performed was 6AWP receptor docking without ligand, with native ligand (6OHMTHβC), and with reference ligand (fluvoxamine). This study also performed molecular docking simulations of 6OHMTHβC towards 6AWP to find compounds in the receptor binding pocket. This study also performed dynamics simulations and identified the molecular determinants using PyPLIF-HIPPOS and YASARA Structure software 20.1.24.10 with the Windows 10 operating system. This study succeeded in determining the stability of the dynamics simulation of the serotonin transport protein complex with the reference ligand 6OHMTHβC for 50 ns, and this result corresponds to the RMSD value and binding energy. The determination of binding energy (BE) was calculated from the BE calculation available at YASARA and Ubuntu. The binding energy value of the original ligand was -11.6590 kJ/mol, and the reference ligand was -83880 kJ/mol. The highest RMSD value of the original ligand was 1.39292Å, while the RMSD value of the reference ligand was 1.71072Å. The essential amino acid carried out was 438Ser with hydrogen bond interactions, so 6OHMTHβC was considered a competent antidepressant candidate.

Virtual screening and molecular dynamics simulation to identify potential SARS-CoV-2 3CLpro inhibitors from a natural product compounds library

Based on the crystal structure of the 3C-like protease/Nsp5 (PDB ID 6W63), virtual hits were screened from a natural product compounds database—containing 407270 natural products—by using the high-throughput virtual screening (HTVS) module of Discovery Studio software, and then filtering by “Lipinski’s rule of five” from the top 20 virtual hits. Two star-hits were selected by CDOCKER results and the protein-ligand interactions with the 3CLpro were analyzed. Finally, a 100 ns molecular dynamics simulation was carried out to verify the stability of the receptor-ligand complexes. We screened potent broad-spectrum non-covalent inhibitors that could bind to the SARS-CoV-2 3CLpro active binding site from the natural product compounds library through HTVS and molecular dynamics simulations methods. The LibDock scores and -CDOCKER energy value of the star-hits were higher than the original ligands (X77) bound to 3CLpro. CNP0348829 and CNP0474002, as star-hits, can bind stably to the active site of 3CLpro, which are promising candidate compounds for the treatment of SARS-CoV-2 and provide a theoretical basis for the development of antiviral drugs. The results of the present study may be useful in the prevention and therapeutic perspectives of COVID-19. However, further in vitro and in vivo validation tests are required in the future.

A singular shark bitter taste receptor provides insights into the evolution of bitter taste perception.

Many animal and plant species synthesize toxic compounds as deterrent; thus, detection of these compounds is of vital importance to avoid their ingestion. Often, such compounds are recognized by taste 2 receptors that mediate bitter taste in humans. Until now, bitter taste receptors have only been found in bony vertebrates, where they occur as a large family already in coelacanth, a "living fossil" and the earliest-diverging extant lobe-finned fish. Here, we have revisited the evolutionary origin of taste 2 receptors (T2Rs) making use of a multitude of recently available cartilaginous fish genomes. We have identified a singular T2R in 12 cartilaginous fish species (9 sharks, 1 sawfish, and 2 skates), which represents a sister clade to all bony fish T2Rs. We have examined its ligands for two shark species, a catshark and a bamboo shark. The ligand repertoire of bamboo shark represents a subset of that of the catshark, with roughly similar thresholds. Amarogentin, one of the most bitter natural substances for humans, also elicited the highest signal amplitudes with both shark receptors. Other subsets of ligands are shared with basal bony fish T2Rs indicating an astonishing degree of functional conservation over nearly 500 mya of separate evolution. Both shark receptors respond to endogenous steroids as well as xenobiotic compounds, whereas separate receptors exist for xenobiotics both in early- and late-derived bony vertebrates (coelacanth, zebrafish, and human), consistent with the shark T2R reflecting the original ligand repertoire of the ancestral bitter taste receptor at the evolutionary origin of this family.

Synthesis and Fluorescent Characteristics Study of Two Novel Co(II) Complexes.

In this work, two novel mixed-ligand CPs that has a compositions of [Co2(µ-Hdppa)2(phen)2(H2O)2] (1) and {[Co(µ-Hdppa)(µ-4,4'-bipy)(H2O)]·H2O}n (2) is achieved through reaction of cobalt salts with the 5-(3,4-Dicarboxylphenyl)picolinic acid (H3dppa) with various N-donor co-ligands (1,10-phenanthroline (phen) for 1 and 4,4'-bipyridine (4,4'-bipy) for 2). The structures and characteristics of these two complexes were fully examined via IR, TGA, and SXRD. Furthermore, their superior blue fluorescence properties compared to the original ligands were confirmed through fluorescence spectroscopy. These two complexes prepared in this study have enriched the choices for blue fluorescent materials.

In silico approaches for the identification of novel ULK1 inhibitors: pharmacophore model, molecular docking and molecular dynamics simulations

The serine/threonine kinase unc-51-like autophagy activating kinase 1 (ULK1) has been regarded as an attractive target for tumor therapy. In this study, in silico approaches, such as the pharmacophore-based virtual screening strategy, molecular docking and molecular dynamics (MD) simulations, were applied to develop novel potential ULK1 inhibitors. The pharmacophore models based on known aminopyrimidine ULK1 inhibitors were constructed to screen the dataset of 1.68 million compounds, which were obtained via screening the 2.30 million compounds in ChEMBL database by Lipinski’s rule of five. Seven novel compounds and 1 known ULK1 inhibitor stand out for the strong virtual biological activity by molecular docking, cluster analysis, Molecular Mechanics/Generalized Born Surface Area (MM/GBSA) calculation and Absorption Distribution Metabolism Excretion Toxicity (ADMET) prediction. Their results of MD included principal component analysis (PCA) and Free Energy Landscapes surface (FELs) indicated that the protein–ligand complex was stable in simulated trajectories of 100 ns. The binding free energy (BFE) calculations showed that a total of 6 novel compounds (CL130, CL834, CL961, CL966, CL163 and CL329) with the stable binding state and stronger BFE (−61.17 to −37.01 kcal/mol) than that of original ligand 3RF (−36.66 kcal/mol). With reference to the ULK1 inhibition of 3RF (IC50 = 160 nM), it can be inferred that these compounds could be used as a new type of potential ULK1 inhibitors and be worthy of further investigation for tumor treatments. Communicated by Ramaswamy H. Sarma

3D-QSAR and Molecular Docking Studies of Pyrimidine-based EGFR Inhibitors

Abstract: Epidermal growth factor tyrosine kinase receptor (EGFR) is expressed in a variety of tumors and has become a new target for anti-cancer drugs. In recent years, small molecule inhibitors targeting EGFR have been reported extensively. In this study, the structure–activity relationship of 119 pyrimidine EGFR inhibitors were studied based on comparative field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMISA). Performant models with high predictive ability were constructed (CoMFA model: q2 = 0.574, r 2 = 0.970, SEE = 0.163, F = 407.252; CoMSIA model: q2 = 0.575, r 2 = 0.968, SEE = 0.171, F = 286.102), according to which 9 new EGFR inhibitors were designed. MD simulation (100 ns) on the docked complex of compound N7 (the most active compound) shows that the small molecule binds with the protein stably. MM/PBSA calculation provided the binding free energy of the compound N7, -37.18 kcal·mol-1, lower than the original ligand. Newly designed molecules showed promising results in ADMET prediction. These results will provide valuable guidance for the design of novel EGFR inhibitors

Potential Application Values of Two Multicoloured Coordination Compounds as Multicolor Luminescent Materials.

Two Co(II)-based coordination compounds, namely {[Co(apc)2]·H2O}n (1) and [Co(apc)2(H2O)2] (2), have been successfully prepared via reaction of a multifunctional ligand 2-aminopyrimidine-5-carboxylic acid (Hapc) with Co(NO3)2·6H2O based on different reaction environments. Both compounds were studied via elemental analysis (EA), single crystal X-ray diffraction analysis (SC-XRD), thermogravimetric analysis (TG), powder X-ray diffraction (PXRD) and infrared spectroscopy (IR). Fluorescence spectroscopy was employed to analyze the fluorescence properties of the ligand and the two compounds. The results revealed that the two compounds exhibited green and blue fluorescence, surpassing the original ligand in terms of properties. Based on the distinct fluorescence colors of the two compounds, there is potential to create multicolored fluorescent materials by adjusting their material ratios. This prospect could further extend their applications in the field of fluorescent materials.

Shapeable sodium alginate aerogel beads incorporated with L-cysteine-modified defective UiO-67 for heavy metal ions removal

Threats caused by heavy metal ions have prompted people to develop porous and functionalized materials to remove them. Metal–organic frameworks (MOFs) show potential for heavy metal ions removal due to the high specific surface area, tunable pore size, flexible designability and favorable stability. However, the intrinsic microporous structure and powder form limit their applications. Herein, we designed a shapeable aerogel bead incorporated with L-cysteine-modified defective UiO-67 for Pb(II), Cd(II) and Cu(II) adsorption. The pristine UiO-67 powders were firstly modified by introducing the modulator (octanoic acid) and an extra ligand (2,2′-bipyridine-5,5′-dicarboxylic acid) to construct defects, both of them competed with the original ligand to coordinate to Zr clusters, resulting in an increased BET surface area (from 337.66 to 1,037.14 m2/g) and mesoporous ratio (from 34 % to 74 %) of the pristine UiO-67. Then, the graft of L-cysteine containing –COOH and –SH introduced more active adsorption sites. Moreover, the powder material was incorporated into sodium alginate aerogel beads which enhanced the recyclability and further improved the adsorption capacity for Pb(II), Cd(II) and Cu(II). These appealing advantages endow the adsorbent with quicker adsorption equilibrium (240 min), and outstanding removal capacities for Pb(II) of 661.2 mg/g, Cd(II) of 296.2 mg/g and Cu(II) of 326.4 mg/g. The chelation and ions exchange between the numerous functional groups including –COOH, –OH and –SH and the heavy metal ions are the main mechanisms for effective adsorption. This work provided a novel approach for the application of MOFs in environmental remediation.

Physics-Guided Deep Generative Model for New Ligand Discovery.

Structure-based drug discovery aims to identify small molecules that can attach to a specific target protein and change its functionality. Recently, deep learning has shown great promise in generating drug-like molecules with specific biochemical features and conditioned with structural features. However, they usually fail to incorporate an essential factor: the underlying physics which guides molecular formation and binding in real-world scenarios. In this work, we describe a physics-guided deep generative model for new ligand discovery, conditioned not only on the binding site but also on physics-based features that describe the binding mechanism between a receptor and a ligand. The proposed hybrid model has been tested on large protein-ligand complexes and small host-guest systems. Using the top-N methodology, on average more than 75% of the generated structures by our hybrid model were stronger binders than the original reference ligand. All of them had higher ΔGbind (affinity) values than the ones generated by the previous state-of-the-art method by an average margin of 1.88 kcal/mol. The visualization of the top-5 ligands generated by the proposed physics-guided model and the reference deep learning model demonstrate more feasible conformations and orientations by the former. The future directions include training and testing the hybrid model on larger datasets, adding more relevant physics-based features, and interpreting the deep learning outcomes from biophysical perspectives.

Thiadiazine-thiones as inhibitors of leishmania pteridine reductase (PTR1) target: investigations and in silico approach

Leishmaniasis is a widespread parasitic disease and is one of the major public health concerns in developing countries. Many drugs have been identified for leishmania as targets, but the potential toxicity and long-term treatment remain the most significant problems in terms of further development. The present study employed physicochemical investigations, structure-based virtual screening, ADMET analysis, molecular dynamics simulation, and MM-PBSA, to identify potential compounds for Leishmania. We evaluated 30,926 natural products from the NPASS database, and four potentials passed the pharmacokinetic ADMET studies and were verified using the molecular docking approach. Molecular docking results showed good binding interaction of the compounds with the active site of leishmania pteridine reductase enzyme PTR1, with compound TTC1 showing FRED and Autodock binding energies of −10.33 and −10.94, respectively, which were comparable with the antileishmania drugs of Allopurinol, Miltefosine and the original ligand, methotrexate. TTC1 compound was found to be favorable for hydrophobic interaction with PTR1. In addition, the physicochemical properties of the compounds were studied using the SwissADME web server. All compounds followed Lipinski’s rule of five and can be considered as good oral candidates. The analysis of the 100 ns molecular dynamics simulation results based on the best-docked TTC1 with PTR1 receptor demonstrates stable interactions, and the complex undergoes low conformational fluctuations. The average of the calculated binding free energy of the TTC1-1e7w complex is (−68.67 kJ/mol), and the result demonstrated that the TTC1 promoted stability to the Leishmania-PTR1 complex. The potential compounds can be further explored for their antileishmanial activity. Communicated by Ramaswamy H. Sarma

Unusual bi- and tetra-nuclear cobalt(II) bis(salamo)-based complex: Preparation, crystal structure and theoretical calculations and fluorescence properties

Two unusual bis(salamo)-based Co(II) complexes, [Co2(L)(OMe)]·2MeOH (1) and [Co4(L1)4(MeOH)4] (2) were designed and successfully prepared, and characterized structurally. The crystal structure analysis showed that complex 1 is composed of one fully deprotonated ligand (L)3− moity, two divalent Co(II) atoms and one bridge-coordinated methanol molecule, while complex 2 is an asymmetric homotetranuclear structure made up of four Co(II) atoms, four fully deprotonated (L1)2− units and four coordinated methanol molecules. It is noteworthy that the reaction of cobalt(II) nitrate with H3L produces complex 2. This complex is not obtained from the original ligand H3L but from a new ligand H2L1. Therefore, the phenomenon can be used to prepare metal(II/III) complexes with excellent structure. The molecular frontier orbitals HOMO and LUMO of H3L and complexes 1 and 2 were analyzed by DFT calculations, and the results showed that the energy gaps of the complexes were reduced due to the combination of the orbitals compared to the ligand. The reaction sites of H3L with Co(II) atoms were analyzed by ESP studies, and the results showed that the crystal structures of the complexes are consistent with the theoretical predictions. Hirshfeld surface analyses indicated the different interactions in the complexes, and revealed that the main contributions to the crystal stacking were from HH, CH and HO interactions. The interactions in the complexes were further explored by IRI research, the results exhibited that there are abundant interactions in complexes 1 and 2, which are important for their construction of supramolecules. The fluorescence strengths of complexes 1 and 2 are significantly lower compared to H3L, which can be attributed to the ligand to metal charge transition (LMCT).

Ligand Engineering of CsPbI3 Quantum Dots for Efficient Solar Cells

Perovskite quantum dots (PQDs) have gained significant attention due to their exceptional optical and electronic properties, rendering them promising materials for various optoelectronic applications, such as single-junction solar cells because of the multiple exciton generation effects. To improve the electrical properties of CsPbI3 PQDs, ligand engineering was explored by introducing short-chain ligands to exchange the original long-chain ligands on the PQD surface during the purification process. However, the short-chain ligands suffer from low solubility in the anti-solvent, resulting in insufficient ligand exchange. To address this issue, we developed an in-situ ligand exchange (ILE) strategy to promote the replacement of long-chain ligands with short-chain ones, leading to improved surface chemistry. In this work, 4-methoxyphenethylammonium iodide (CH3O-PEAI) was demonstrated as the short-chain ligand in the ILE strategy, thereby modifying halide vacancy trap states, and promoting carrier transportation and extraction. As a result, the ILE-CsPbI3-based solar cells achieved a higher power conversion efficiency of 14.4% with a high open circuit voltage (VOC) of 1.23 V and exceptional long-term durability due to higher hydrophobicity.