Molecular Modeling Calculations Research Articles

Elucidation of Complexation Mechanism of Rosmarinic Acid and Berberine

Polyphenols are known to form complexes with various organic compounds. This ability can may change the chemical or physical properties of the compounds involved and may even affect their efficacy in the case of drugs. Our research revealed that mixing solutions of the polyphenol rosmarinic acid (RA) and berberine (Ber), a widely used and pharmacologically important isoquinoline alkaloid, resulted in the formation of a precipitate of the RA–Ber complex at a molar ratio of 1:1. This was confirmed using 1H NMR and Fourier Transform Infrared Spectroscopy. To elucidate the formation mechanism of the precipitate, the behavior of RA and Ber in an aqueous solution was examined using 1H NMR, indicating the formation of the RA–Ber complex at a molar ratio of 1:1, consistent with the results of precipitation. Additionally, we investigated the steric structure of the RA–Ber complex in an aqueous solution using molecular modeling calculations. These calculations suggested the existence of seven types different steric structures of the RA–Ber complex, primarily stabilized by π–π interactions. Based on these results, we concluded that mixing RA and Ber solutions in an aqueous environment results in the formation of RA–Ber complexes with seven types different steric structures at a molar ratio of 1:1. The precipitate forms because these complexes are less water-soluble than either RA or Ber alone.

An optimal global biochar application strategy based on matching biochar and soil properties to reduce global cropland greenhouse gas emissions: findings from a global meta-analysis and density functional theory calculation

Biochar has been extensively utilized to amend soil and mitigate greenhouse gas (GHG) emissions from croplands. However, the effectiveness of biochar application in reducing cropland GHG emissions remains uncertain due to variations in soil properties and environmental conditions across regions. In this study, the impact of biochar surface functional groups on soil GHG emissions was investigated using molecular model calculation. Machine learning (ML) technology was applied to predict the responses of soil GHG emissions and crop yields under different biochar feedstocks and application rates, aiming to determine the optimum biochar application strategies based on specific soil properties and environmental conditions on a global scale. The findings suggest that the functional groups play an essential role in determining biochar surface activity and the soil’s capacity for adsorbing GHGs. ML was an effective method in predicting the changes in soil GHG emissions and crop yield following biochar application. Moreover, poor-fertility soils exhibited greater changes in GHG emissions compared to fertile soil. Implementing an optimized global strategy for biochar application may result in a substantial reduction of 684.25 Tg year−1 CO2 equivalent (equivalent to 7.87% of global cropland GHG emissions) while simultaneously improving crop yields. This study improves our understanding of the interaction between biochar surface properties and soil GHG, confirming the potential of global biochar application strategies in mitigating cropland GHG emissions and addressing global climate degradation. Further research efforts are required to optimize such strategies.Graphical

Effects of Ring Functionalization in Anthracene-Based Cyclophanes on the Binding Properties Toward Nucleotides and DNA.

Supramolecular recognition of nucleobases and short sequences is an emerging research field focusing on possible applications to treat many diseases. Controlling the affinity and selectivity of synthetic receptors to target desired nucleotides or short sequences is a highly challenging task. Herein, we elucidate the effect of substituents in the phenyl ring of the anthracene-benzene azacyclophane on the recognition of nucleoside triphosphates (NTPs) and double-stranded DNA. We show that introducing phenyl rings increases the affinity for NTPs 10-fold and implements groove and intercalation binding modes with double-stranded DNA. NMR studies and molecular modeling calculations support the ability of cyclophanes to encapsulate nucleobases as part of nucleotides.

Preparation of T8 and double-decker silsesquioxane-based Janus-type molecules: molecular modeling and DFT insights

We present a methodology for the synthesis of inorganic-organic Janus-type molecules based on mono-T8 and difunctionalized double-decker silsesquioxanes (DDSQs) via hydrosilylation reactions, achieving exceptionally high yields and selectivities. The synthesized compounds were extensively characterized using various spectroscopic techniques, and their sizes and spatial arrangements were predicted through molecular modelling and density functional theory (DFT) calculations. Quantum chemical calculations were employed to examine the interactions among four molecules of the synthesized compounds. These computational results allowed us to determine the propensity for molecular aggregation, identify the functional groups involved in these interactions, and understand the changes in interatomic distances during aggregation. Understanding the aggregation behaviour of silsesquioxane molecules is crucial for tailoring their properties for specific applications, such as nanocomposites, surface coatings, drug delivery systems, and catalysts. Through a combination of experimental and computational approaches, this study provides valuable insights into the design and optimization of silsesquioxane-based Janus-type molecules for enhanced performance across various fields.

A new combined collector of sodium oleate and 1,12-dodecanediamine for efficient flotation separation of spodumene from feldspar

A new combined collector of NaOL and 1,12-Dodecanediamine (DA122) was used for efficient flotation of spodumene from feldspar. The disparities in mineral flotation efficacy between the combined collectors of NaOL/1,12-Dodecanediamine and NaOL/Dodecylamine (DDA), as well as the underlying mechanisms, were comprehensively analyzed by the measurements of flotation experiments, surface tension, adsorption amount measurement, structure and frontier molecular orbital analysis and adsorption model calculation. The results of mixed minerals micro-flotation indicate that the Li2O recovery of 91.64 % was achieved using NaOL and DA122 combined collector, which represents an 11.54 % increase in Li2O recovery compared to using the NaOL and DDA combined collector. NaOL and DA122 combined collector exhibits a lower critical micelle concentration (CMC) and the greater adsorption amount on the surface of spodumene. NaOL and DA122 combined collector demonstrates higher reactivity and adsorption energy on the surface of spodumene, resulting in higher hydrophobicity of spodumene because DA122 possesses stronger ability to lose electrons than DDA, thus leading to higher recovery of spodumene.

Molecular self-assembled helix peptide nanotubes based on some amino acid molecules and their dipeptides: molecular modeling studies.

The paper considers the features of the structure and dipole moments of several amino acids and their dipeptides which play an important role in the formation of the peptide nanotubes based on them. The influence of the features of their chirality (left L and right D) and the alpha-helix conformations of amino acids are taken into account. In particular, amino acids with aromatic rings, such as phenylalanine (Phe/F), and branched-chain amino acids (BCAAs)-leucine (Leu/L) and isoleucine (Ile/I)-as well as corresponding dipeptides (diphenylalanine (FF), dileucine (LL), and diisoleucine (II)) are considered. The main features and properties of these dipeptide structures and peptide nanotubes (PNTs), based on them, are investigated using computational molecular modeling and quantum-chemical semi-empirical calculations. Their polar, piezoelectric, and photoelectronic properties and features are studied in detail. The results of calculations of dipole moments and polarization, as well as piezoelectric coefficients and band gap width, for different types of helical peptide nanotubes are presented. The calculated values of the chirality indices of various nanotubes are given, depending on the chirality of the initial dipeptides-the results obtained are consistent with the law of changes in the type of chirality as the hierarchy of molecular structures becomes more complex. The influence of water molecules in the internal cavity of nanotubes on their physical properties is estimated. A comparison of the results of these calculations by various computational methods with the available experimental data is presented and discussed. The main tool for molecular modeling of all studied nanostructures in this work was the HyperChem 8.01 software package. The main approach used here is the Hartree-Fock (HF) self-consistent field (SCF) with various quantum-chemical semi-empirical methods (AM1, PM3, RM1) in the restricted Hartree-Fock (RHF) and in the unrestricted Hartree-Fock (UHF) approximations. Optimization of molecular systems and the search for their optimal geometry is carried out in this work using the Polak-Ribeire algorithm (conjugate gradient method), which determines the optimized geometry at the point of their minimum total energy. For such optimized structures, dipole moments D and electronic energy levels (such as EHOMO and ELUMO), as well as the band gap Eg = ELUMO - EHOMO, were then calculated. For each optimized molecular structure, the volume was calculated using the QSAR program implemented also in the HyperChem software package.

Competitive adsorption of exchangeable Al3+ on the surface of lignosulfonate contributes to reducing soil acidification while improving soil fertility: Findings from a density functional theory calculation

Soil acidification poses a significant threat to the healthy development of agriculture. Traditional soil amendment involving lime (L) has notable limitations. Therefore, developing alternative soil acidification amendment methods to address soil acidification holds significance. In this study, calcium lignosulfonate (LC) was introduced to different acidic purple soils to assess its efficacy in reducing soil acidity and enhancing soil fertility. The density functional theory (DFT) calculation was employed to analyze the potential interaction mechanisms of LC in decreasing soil acidity. The results indicated that the 2 ‰ LC addition improved the pH by 2.8 and the soil organic carbon by 26 % in poor-quality and extremely acidic purple soil (with an initial pH of 4.4) after a 40-day soil pot experiment. The findings from the Fourier Transform infrared spectroscopy (FTIR) and DFT calculation suggested that the competitive adsorption between Al3+ and Ca2+ on the surface functional groups (e.g., –SO3- and –OH) of LC contributes to the immobilization of soil exchangeable Al3+. These results validate the feasibility of LC as an alternative to lime application for amending extremely acidic soils and underscore its advantages for soil fertility enhancement. The results of the molecular model calculation extend the understanding of the key mechanisms of LC mitigating soil acidification. This study will highlight the potential of LC in agricultural applications and contribute to the development of more effective soil amendments to ensure cropland health and promote sustainable agriculture.

Synthesis, Docking, and DFT Studies on Novel Schiff Base Sulfonamide Analogues as Selective COX-1 Inhibitors with Anti-Platelet Aggregation Activity.

Selective COX-1 inhibitors are preferential therapeutic targets for platelet aggregation and clotting responses. In this study, we examined the selective COX-1-inhibitory activities of four newly synthesized compounds, 10-13, along with their abilities to inhibit platelet aggregation against ADP and collagen. The target compounds 10-13 were synthesized using the conventional method, sonication, and microwave-assisted methods. Microanalytical and spectral data were utilized to elucidate the structures of the new compounds 10-13. Additionally, a spectral NMR experiment [NOESY] was conducted to emphasize the configuration around the double bond of the imine group C=N. The obtained results revealed no observed correlation between any of the neighboring protons, suggesting that the configuration at the C=N double bond is E. Biological results revealed that all the screened compounds 10-13 might serve as selective COX-1 inhibitors. They showed IC50 values ranging from 0.71 μM to 4.82 μM against COX-1 and IC50 values ranging from 9.26 μM to 15.24 μM against COX-2. Their COX-1 selectivity indices ranged between 2.87 and 18.69. These compounds show promise as promising anti-platelet aggregation agents. They effectively prevented platelet aggregation induced by ADP with IC50 values ranging from 0.11 μM to 0.37 μM, surpassing the standard aspirin with an IC50 value of 0.49 μM. Additionally, they inhibited the platelet aggregation induced by collagen with IC50 values ranging from 0.12 μM to 1.03 μM, demonstrating superior efficacy compared to aspirin, which has an IC50 value of 0.51 μM. In silico molecular modeling was performed for all the target compounds within the active sites of COX-1 and COX-2 to rationalize their selective inhibitory activities towards COX-1. It was found that the binding interactions of the designed compounds within the COX-1 active site had remained unaffected by the presence of celecoxib. Molecular modeling and DFT calculations using the B3LYP/6-31+G (d,p) level were performed to study the stability of E-forms with respect to Z-forms for the investigated compounds. A strong correlation was observed between the experimental observations and the quantum chemical descriptors.

Photo‐Responsive TiO2‐Gold Nanoparticle‐Polymer Nanohybrid Exhibits Photothermal, Thermo‐Release, and Photocatalytic Effects

AbstractThe development of multi‐responsive nanohybrid systems that combine photothermia, thermo‐responsive effects and photocatalysis is a challenging topic in the research of multifunctional materials with a large field of applications. Here, we report the first example of a three‐components light‐responsive nanosystem consisting of titania, gold nanoparticles and poly‐N‐isopropylacrylamide (TiO2‐Au‐PNM). The hybrid nanostructure exhibited photothermal conversion effect upon green‐light excitation and capacity to entrap methylene blue and curcumin selected as cargo models. The formation of the nanohybrid–cargo adducts, the photothermal‐controlled cargo release triggered by green‐light irradiation (532 nm) and mediated by lower critical solution temperature (LCST), as well as the photocatalytic effect prompted by UV‐light excitation (300 nm) were demonstrated by spectroscopic techniques. The mechanism involved in the interaction of the polymeric component with the cargos was investigated by molecular modelling calculations.

Copper(II) Complexes with Isomeric Morpholine-Substituted 2-Formylpyridine Thiosemicarbazone Hybrids as Potential Anticancer Drugs Inhibiting Both Ribonucleotide Reductase and Tubulin Polymerization: The Morpholine Position Matters.

The development of copper(II) thiosemicarbazone complexes as potential anticancer agents, possessing dual functionality as inhibitors of R2 ribonucleotide reductase (RNR) and tubulin polymerization by binding at the colchicine site, presents a promising avenue for enhancing therapeutic effectiveness. Herein, we describe the syntheses and physicochemical characterization of four isomeric proligands H2L3-H2L6, with the methylmorpholine substituent at pertinent positions of the pyridine ring, along with their corresponding Cu(II) complexes 3-6. Evidently, the position of the morpholine moiety and the copper(II) complex formation have marked effects on the in vitro antiproliferative activity in human uterine sarcoma MES-SA cells and the multidrug-resistant derivative MES-SA/Dx5 cells. Activity correlated strongly with quenching of the tyrosyl radical (Y•) of mouse R2 RNR protein, inhibition of RNR activity in the cancer cells, and inhibition of tubulin polymerization. Insights into the mechanism of antiproliferative activity, supported by experimental results and molecular modeling calculations, are presented.

Effect of support type on the characteristics of polybutene polymers from C4 monomers employing supported ionic liquid/AlCl3 initiating systems

In order to assess the effect of support type on the characteristics of polybutene polymers, cyclohexyl imidazolium chloride ionic liquid was grafted onto the surface of various supports including boehmite, halloysite, palygorskite, and kaolinite. The furnished supported ionic liquids were employed alongside AlCl3/ethanol as initiating systems to polymerize C4 monomers, resulting in polybutene polymers. Overall, XRD, FTIR, TGA, SEM, EDS, and Elemental Mapping Analyses convinced the successful homogenous grafting of ionic liquid onto the surface of subjected supports. To obtain precious and essential information about molecular weight, dispersity, and microstructure of polymers, GPC, 1H NMR, and 13C NMR analyses were conducted. Among the four initiating systems, kaolinite supported ionic liquid demonstrated the most satisfying results, Yield = 88.2 %, Mn= 18104 g mol−1, Ð = 1.83, exo= 6.1 % and isobutylene content of 92.5 %. Hence, this supported ionic liquid was fully characterized via SEM, EDX, Elemental Mapping, XRD, FT IR and TGA analyses. To get deeper insight about the type and quantity of molecular interactions in the kaolinite supported ionic liquid, molecular modeling calculation was also considered. Beside efficiently balancing polymerization condition, implementing the AlCl3/ionic liquid initiating system promotes a more environmentally friendly polymerization approach by halving the amount of hazardous AlCl3 compared to the blank system including neat AlCl3 as the single co-initiator.

Computational and experimental approaches into molecular structure mechanism of ZQV coal and the COx gas releases during pyrolysis

Understanding the structural features of coal and its reactive behaviors in thermal processing is the fundamental to achieve high-efficiency utilization of coal. However, the molecular structural features and the evolution characteristics at atomic scales in thermal processing remain unclear in the microscopic views, particularly for the low-rank coals, which usually exhibits high oxygen content with a variety of oxygen-containing organic functional groups and gets lots of CO/CO2 release during pyrolysis. This research provides a comprehensive analysis of the ZaoQuan vitrinite (ZQV) bituminous coal's structural attributes and its pyrolysis-induced reactivity, which is crucial for optimizing the thermal conversion of low-rank coals. The structural parameters characteristics and molecular structures of ZQV have been revealed based on series of materials characterizations and molecular modeling calculations. The single molecular description of ZQV was conceptualized to be C209H132O41N2 under the average molecular approximation, and the particle models with size about 10 nm was also been obtained. Based on the built molecular models, reactive force field molecular dynamics (ReaxFF MD) simulations then provided insights into the dynamic behavior of molecular structures under pyrolysis conditions. Experimental validation corroborates the computational predictions, revealing a strong coherence between observed gas products and those derived from simulation data. Crucially, this study vividly captures the dynamic migration patterns of oxygen-containing groups during coal's thermal decomposition, thus contributing to the understanding of gasification processes. The release mechanisms for CO and CO2 are systematically dissected, proposing three and two distinct pathways respectively. These findings not only consolidate the molecular narrative of coal's structure and pyrolysis reactivity but also serve as a reliable foundation for interpreting the COx evolution of low-rank coals. Our integrated approach propels the scientific comprehension of coal pyrolysis and is anticipated to inform the development of more effective coal utilization pathways and thermal treatment technologies.

Antioxidant, antibacterial, and molecular docking of methyl ferulate and oleic acid produced by Aspergillus pseudodeflectus AUMC 15761 utilizing wheat bran

Secondary metabolites (SMs) are the primary source of therapeutics and lead chemicals in medicine. They have been especially important in the creation of effective cures for conditions such as cancer, malaria, bacterial and fungal infections, neurological and cardiovascular problems, and autoimmune illnesses. In the present study, Aspergillus pseudodeflectus AUMC 15761 was demonstrated to use wheat bran in solid state fermentation (SSF) at optimum conditions (pH 7.0 at 30 °C after 10 days of incubation and using sodium nitrate as a nitrogen source) to produce methyl ferulate and oleic acid with significant antioxidant and antibacterial properties. Gas chromatography-mass spectrometry (GC–MS) analysis of the crude methanol extract revealed eleven peaks that indicated the most common chemical components. Purification of methyl ferulate and oleic acid was carried out by column chromatography, and both compounds were identified by in-depth spectroscopic analysis, including 1D and 2D NMR and HR-ESI–MS. DPPH activity increased as the sample concentration increased. IC50 values of both compounds obtained were 73.213 ± 11.20 and 104.178 ± 9.53 µM, respectively. Also, the MIC value for methyl ferulate against Bacillus subtilis and Staphylococcus aureus was 0.31 mg/mL, while the corresponding MIC values for oleic acid were 1.25 mg/mL and 0.62 mg/mL for both bacterial strains, respectively. Molecular modeling calculations were carried out to reveal the binding mode of methyl ferulate and oleic acid within the binding site of the crucial proteins of Staphylococcus aureus. The docking results were found to be well correlated with the experimental data.

Binding of Acetylated Lysine by Using a Water Soluble Aryl Extended Calix[4]pyrrole.

Post-translational modifications of lysine in histones, as methylation and acetylation, have well established functions in epigenetics and are emerging as important actors in broader biological regulation. Currently, the detection of acetylated lysine (Kac) in water solution as free amino acid or protein residue remains challenging. Acetylated lysine is a neutral amino acid, and the lack of ion-dipole interactions causes the decrease in binding affinity displayed by synthetic molecular receptors with respect to the other lysine modifications. Here, we report molecular modeling calculations and 1H NMR experiments to investigate the binding properties of two different calix[4]pyrrole receptors towards Kac. Computational analyses reveal that tetra-aryl-extended calix[4]pyrrole (1) preferentially binds the cis-Kac conformer over the trans one due to steric considerations and more favorable interactions. Experimental 1H NMR titration experiments confirm the formation of a 1 : 1 complex between receptor 1 and cis-Kac, with a Ka exceeding 103 M-1. Conversely, the super-aryl-extended calix[4]pyrrole 2 is less efficient in binding Kac, due to unfavorable solvation/desolvation effects, as proven by 1H NMR experiments. Moreover, receptor 1 showed a higher affinity for Kac over other lysine modifications, such as methylated lysines.

Three-Dimensional Hydrogen-Bonded Porous Metal-Organic Framework for Natural Gas Separation with High Selectivity.

A 3D hydrogen-bonded metal-organic framework, [Cu(apc)2]n (TJU-Dan-5, Hapc = 2-aminopyrimidine-5-carboxylic acid), was synthesized via a solvothermal reaction. The activated TJU-Dan-5 with permanent porosity exhibits a moderate uptake of 1.52 wt% of hydrogen gas at 77 K. The appropriate BET surface areas and decoration of the internal polar pore surfaces with groups that form extensive hydrogen bonds offer a more favorable environment for selective C2H6 adsorption, with a predicted selectivity for C2H6/CH4 of around 101 in C2H6/CH4 (5:95, v/v) mixtures at 273 K under 100 kPa. The molecular model calculation demonstrates a C-H···π interaction and a van der Waals host-guest interaction of C2H6 with the pore walls. This work provides a strategy for the construction of 3D hydrogen-bonded MOFs, which may have great potential in the purification of natural gas.

γ-Cyclodextrins as Supramolecular Reactors for the Three-component Aza-Darzens Reaction in Water.

In recent decades, many efforts have been devoted to studying reactions catalyzed in nanoconfined spaces. The most impressive aspect of catalysis in nanoconfined spaces is that the reactivity of the molecules can be smartly driven to disobey classical behavior. A green and efficient three-component aza-Darzens (TCAD) reaction using a catalytic amount of γ-cyclodextrins (CDs) in water has been developed to synthesize N-phenylaziridines. CDs effectively performed this reaction in an environmentally friendly setting, achieving good yields. The same reaction was then performed using polymeric γ-CD such as a γ-cyclodextrin polymer crosslinked (GCDPC) with epichlorohydrin, a sponge-like macroporous γ-cyclodextrin-based cryogel (GCDC), and a γ-cyclodextrin-based hydrogel (GCDH). The homogeneous and heterogeneous catalyst recovery was then studied, and it was proved to be easily recycled several times without relevant activity loss. Water, as a unique and eco-friendly reaction medium, has been utilized for the first time, to the best of our knowledge, in this reaction. The inclusion of the reagents in CDs has been studied and rationalized by NMR spectroscopy experiments and molecular modeling calculations. The credit of the presented protocol includes good yields and catalyst reusability and precludes the use of organic solvents.

Assessment the exposure effects of polycarbonate with X-ray radiation using spectroscopic techniques and molecular modeling calculations

Assessment the exposure effects of polycarbonate with X-ray radiation using spectroscopic techniques and molecular modeling calculations

Development and Comprehensive Benchmark of a High-Quality AMBER-Consistent Small Molecule Force Field with Broad Chemical Space Coverage for Molecular Modeling and Free Energy Calculation.

Biomolecular simulations have become an essential tool in contemporary drug discovery, and molecular mechanics force fields (FFs) constitute its cornerstone. Developing a high quality and broad coverage general FF is a significant undertaking that requires substantial expert knowledge and computing resources, which is beyond the scope of general practitioners. Existing FFs originate from only a limited number of groups and organizations, and they either suffer from limited numbers of training sets, lower than desired quality because of oversimplified representations, or are costly for the molecular modeling community to access. To address these issues, in this work, we developed an AMBER-consistent small molecule FF with extensive chemical space coverage, and we provide Open Access parameters for the entire modeling community. To validate our FF, we carried out benchmarks of quantum mechanics (QM)/molecular mechanics conformer comparison and free energy perturbation calculations on several benchmark data sets. Our FF achieves a higher level of performance at reproducing QM energies and geometries than two popular open-source FFs, OpenFF2 and GAFF2. In relative binding free energy calculations for 31 protein-ligand data sets, comprising 1079 pairs of ligands, the new FF achieves an overall root-mean-square error of 1.19 kcal/mol for ΔΔG and 0.92 kcal/mol for ΔG on a subset of 463 ligands without bespoke fitting to the data sets. The results are on par with those of the leading commercial series of OPLS FFs.

New 5-Substituted SN38 Derivatives: A Stability Study and Interaction with Model Nicked DNA by NMR and Molecular Modeling Methods.

The new 5-substituted SN-38 derivatives, 5(R)-(N-pyrrolidinyl)methyl-7-ethyl-10-hydroxycamptothecin (1) and its diastereomer 5(S) (2), were investigated using a combination of nuclear magnetic resonance (NMR) spectroscopy and molecular modeling methods. The chemical stability, configuration stability, and propensity to aggregate as a function of concentration were determined using 1H NMR. The calculated self-association constants (Ka) were found to be 6.4 mM-1 and 2.9 mM-1 for 1 and 2, respectively. The NMR experiments were performed to elucidate the interaction of each diastereomer with a nicked decamer duplex, referred to as 3. The calculated binding constants were determined to be 76 mM-1 and 150 mM-1 for the 1-3 and 2-3 complexes, respectively. NMR studies revealed that the interaction between 1 or 2 and the nicked decamer duplex occurred at the site of the DNA strand break. To complement these findings, molecular modeling methods and calculation protocols were employed to establish the interaction mode and binding constants and to generate molecular models of the DNA/ligand complexes.

Study on the photoinitiation mechanism of carbazole-based oxime esters (OXEs) as novel photoinitiators for free radical photopolymerization under near UV/visible-light irradiation exposure and the application of 3D printing

In this work, twenty-two oxime esters bearing different functional groups and based on carbazole as the chromophore were designed and synthesized as Type I photoinitiators. Interestingly, all structures mentioned in this work have never been reported before (even for their synthesis). These oxime esters were found to have good light absorption properties in the UV–visible range, and especially at 405 nm which is a reference wavelength in photopolymerization. Noticeably, several structures showed better photoinitiation abilities than the benchmark photoinitiator i.e. diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), evidencing the interest of these structures. In order to investigate the photoinitiation mechanism of the two series of oxime esters differing by the position of the photocleavable groups, electronic absorption spectra were determined by molecular modeling and density functional theory calculations. Photopolymerization abilities of the different oxime esters and release of CO2 during the polymerization experiments were determined by Real-Time Fourier Transformed Infrared (RT-FTIR). Active free radicals were characterized by mean of Electron Spin Resonance Spin Trapping (ESR-ST) experiments. On the basis of these different complementary experiments, chemical mechanisms occurring during photopolymerization could be proposed. Experimental results showed that the decarboxylation reaction occurring subsequent to the photocleavage of oxime esters had a beneficial effect on the photoinitiation ability. Finally, 3D printed objects were successfully obtained by using oxime esters exhibiting the best photoinitiating abilities.