Aromatic Precursors Research Articles

Aromatic Structures Govern the Formation of Chlorinated Byproducts in Dichlorine Radical Reactions.

Radical-induced disinfection byproduct (DBP) formation is drawing attention with increasing applications of advanced oxidation processes (AOPs). Cl2•- represents one of the extensively generated radicals in AOPs, whose behavior in DBP formation remains unknown. In this study, we found that aromatic structures serve as the main DBP precursors in Cl2•- reactions by employing diverse groups of model compounds. At a typical Cl2•- exposure of 1.2 × 10-9 M·s, the sum concentrations of 7 regulated aliphatic DBPs (e.g., trichloromethane, chloroacetic acids) are ∼0.10 to 0.48 μM for aromatic precursors and <0.05 μM for aliphatic ones. The DBP formation mechanisms from Cl2•- reactions involved the formation of chlorinated aromatics, radical-induced oxygen incorporation followed by ring cleavage, and the interactions of Cl2•- with ring-cleavage intermediates. In reacting with DOM, Cl2•- reactions produced much fewer aliphatic DBPs (5% of the total organochlorine vs 40% for chlorination) and chloroacetic acids dominated the aliphatic DBPs (usually trihalomethane for chlorination), which can be well interpreted by the precursors and mechanisms proposed. This work comprehensively reveals the precursors, formation patterns, and mechanisms of DBPs during the less-studied Cl2•- reactions, highlighting the importance of eliminating the aromatic structures of DOM before the AOPs.

Mechanistic Insights into the Evolution of Graphitic Carbon from Sulfur Containing Polar Aromatic Feedstock.

In the realm of carbon fiber research, a variety of structural configurations is noted, comprising crystalline, noncrystalline, and semicrystalline forms. Recent investigations into this domain have revealed an array of intriguing phases of carbon, among which amorphous graphite is the most notable for its unique mechanical, thermal, and electrical properties that arise from its inherent topological disorders. In this study, we utilized the ReaxFF molecular dynamics (MD) simulations to investigate the carbonization and graphitization processes involved in the production of amorphous graphite from benzothiophene, a sulfur-containing polar aromatic precursor. We developed C/H/S ReaxFF force field parameters to describe the high-temperature chemistry of benzothiophene. Our investigation reveals the reaction mechanisms, providing critical insights into the underlying chemical processes toward the formation of amorphous graphite and the structural characteristics of the end products. The formation of volatile gaseous molecules and their continuous elimination led to the development of noncontinuous layered graphite structures analogous to amorphous graphite consisting of pentagons, hexagons, and heptagons. These findings offer unprecedented insights into the carbonization and graphitization processes of sulfur-containing heavy-end aromatic feedstock. This knowledge lays the groundwork for advancing synthesis methods and developing amorphous graphite materials with specific properties.

One-pot bioconversion of lignin to 4-vinylphenol derivatives

Lignin, the largest renewable aromatic resource in nature, is a promising feedstock to produce aromatic fine chemicals. The bioconversion of lignin into 4-vinylphenol derivatives (4VPs) is a sustainable route to promote both lignin valorization and bioeconomy. However, challenges such as heterologous lignin and an inefficient synthetic pathway for 4VPs restrict the bioconversion performance. In this work, microbial cell factories were designed to valorize lignin into 4VPs, emphasizing an atom-economic route. Rewriting endogenous pathways and heterogeneously expressing phenolic acid decarboxylases successfully produced 4VPs from lignin-derived aromatic precursors. Enzymatic kinetics revealed that the screened phenolic acid decarboxylases possessed outstanding catalytic activity against lignin derivatives. A biphasic glyceryl tributyrate/water system was developed for efficient in situ extraction of 4VPs, successfully removing the product-feedback inhibition effect. Accordingly, the microbial cell factory produced the record titers of 4-vinylphenol, 4-vinylguaiacol and 4-vinylsyringol at 235.3, 203.0 and 35.8 g/L, respectively, with the productivity of 3.0, 2.7, and 0.8 g/L/h. The microbial cell factory was further engineered to simultaneously convert three-type aromatic of lignin into 4VPs through a one-pot bioconversion. The microbial cell factory also exhibited the remarkable bioconversion capacity of actual lignin hydrolysate by producing 12.4 g/L and 2.3 g/L of 4-vinylphenol and 4-vinylguaiacol, respectively. The molecular mechanism suggested that corresponding polymers were successfully produced and displayed good thermal stability. Overall, the microbial cell factory demonstrated an impressive capacity to convert lignin derivatives and achieve record titers of 4VPs, showcasing its potential to revolutionize lignin valorization and the production of functional polystyrene materials.

One-step solvothermal synthesis of nitrogen-doped carbon dots with efficient red emission from conjugated perylene for multiple applications

Despite its significance for applications related to plant growth, the development of carbon dots (CDs) with bright red emissions still faces multiple obstacles. Herein, red emission hydrophobic carbon dots (RH-CDs) featuring one emission peak centered at 594 nm and a shoulder emission peak at 630 nm with a quantum yield of 34 % and a wide full width at half maximum (FWHM) of 100 nm (580 nm–680 nm) were synthesized by adopting large conjugated perylene anhydride and aromatic amine precursors under solvothermal conditions. Density functional theory calculations support the method of using larger conjugated systems and higher graphite N doping to increase red emissions from CDs. With a post-surface functionalization strategy, polyvinylpyrrolidone (PVP)-modified RH-CDs (QY = 12 %) were utilized as an anti-counterfeiting ink for information printing. Moreover, both blue-red light-emitting diodes (LEDs) and light conversion poly (methyl methacrylate) (PMMA)-CDs film were fabricated with emission spectra that are consistent with the absorption spectra of plants, suggesting that the prepared RH-CDs may have widespread application potential as a stable fluorescent material in plant growth.

Evolving dual-trait EPSP synthase variants using a synthetic yeast selection system

The enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) functions in the shikimate pathway which is responsible for the production of aromatic amino acids and precursors of other essential secondary metabolites in all plant species. EPSPS is also the molecular target of the herbicide glyphosate. While some plant EPSPS variants have been characterized with reduced glyphosate sensitivity and have been used in biotechnology, the glyphosate insensitivity typically comes with a cost to catalytic efficiency. Thus, there exists a need to generate additional EPSPS variants that maintain both high catalytic efficiency and high glyphosate tolerance. Here, we create a synthetic yeast system to rapidly study and evolve heterologous EPSP synthases for these dual traits. Using known EPSPS variants, we first validate that our synthetic yeast system is capable of recapitulating growth characteristics observed in plants grown in varying levels of glyphosate. Next, we demonstrate that variants from mutagenesis libraries with distinct phenotypic traits can be isolated depending on the selection criteria applied. By applying strong dual-trait selection pressure, we identify a notable EPSPS mutant after just a single round of evolution that displays robust glyphosate tolerance (Ki of nearly 1 mM) and improved enzymatic efficiency over the starting point (~2.5 fold). Finally, we show the crystal structure of corn EPSPS and the top resulting mutants and demonstrate that certain mutants have the potential to outperform previously reported glyphosate-resistant EPSPS mutants, such as T102I and P106S (denoted as TIPS), in whole-plant testing. Altogether, this platform helps explore the trade-off between glyphosate resistance and enzymatic efficiency.

Self-Exfoliating Benzotristriazine Macrocyclic Network: A New 2D Material for High-Performance Electrochemical Energy Storage.

Aza-fused aromatic π-conjugated networks are an important class of 2D graphitic analogs, which are generally constructed using aromatic precursors. Herein, the study describes a new synthetic approach and electrochemical properties of a self-exfoliating benzotristriazine 2D network (BTTN) constructed using aliphatic precursors, under relatively mild conditions. The obtained BTTN exhibits a nanodisc-like morphology, the self-exfoliation tendency of which is ascribed to the presence of structurally different macrocycles with high electronic repulsion between the layers. The benzotristriazine repeat units of BTTN is electroactive and holds higher carbon/nitrogen ratio when compared with the conventional graphitic aza-fused π-conjugated networks. The self-exfoliated BTTN nanodiscs show excellent electrochemical energy storage of 485 and 333 F g-1 at 1 A g-1 in three-electrode and two-electrode measurements, respectively. BTTN in a symmetric coin-cell architecture exhibits a high specific energy value of 46Wh kg-1 at a power density of 1kW kg-1 and shows excellent cyclic stability of 96% for 10000 and 90% for 30000 charge-discharge cycles at a higher current density of 5 A g-1, surpassing the device performance of most of the reported all-organic pseudocapacitive 2D networks.

Preparation of a high-performance synthetic pitch from aromatic hydrocarbons containing N/Cl

The preparation of a synthetic pitch from aromatic monomers could easily regulate structure orientation at the molecular level, which would be useful in fabrication. An isotropic synthetic pitch was prepared by a chlorine- and/or nitrogen-induced substitution polymerization reaction method using aromatic hydrocarbon precursors containing Cl and N, which for this study were chloromethyl naphthalene and quinoline. This method was verified by investigating the structural changes under different synthesis conditions, and the synthesis mechanism induced by aromatics containing Cl was also probed. The result shows that the pyridinic N in quinoline contains a lone pair of electrons, and is an effective active site to induce the polymerization reaction by coupling with aromatic hydrocarbons containing Cl. The reaction between such free radicals causes strong homopolymerization and oligomerization. A higher reaction temperature and longer reaction time significantly increased the degree of polymerization and thus increased the softening point of the pitch. A linear molecular structure was formed by the Cl substitution reaction, which produced a highly spinnable pitch with a softening point of 258.6 °C, and carbon fibers with a tensile strength of 1 163.82 MPa were obtained. This study provides a relatively simple and safe method for the preparation of high-quality spinnable pitch.

Isotopologues of potassium 2,2,2-trifluoroethoxide for applications in positron emission tomography and beyond

The 2,2,2-trifluoroethoxy group increasingly features in drugs and potential tracers for biomedical imaging with positron emission tomography (PET). Herein, we describe a rapid and transition metal-free conversion of fluoroform with paraformaldehyde into highly reactive potassium 2,2,2-trifluoroethoxide (CF3CH2OK) and demonstrate robust applications of this synthon in one-pot, two-stage 2,2,2-trifluoroethoxylations of both aromatic and aliphatic precursors. Moreover, we show that these transformations translate easily to fluoroform that has been labeled with either carbon-11 (t1/2 = 20.4 min) or fluorine-18 (t1/2 = 109.8 min), so allowing the appendage of complex molecules with a no-carrier-added 11C- or 18F- 2,2,2-trifluoroethoxy group. This provides scope to create candidate PET tracers with radioactive and metabolically stable 2,2,2-trifluoroethoxy moieties. We also exemplify syntheses of isotopologues of potassium 2,2,2-trifluoroethoxide and show their utility for stable isotopic labeling which can be of further benefit for drug discovery and development.

Mechanisms and high-value applications of phthalate isomers degradation pathways in bacteria.

Phthalate isomers are key intermediates in the biodegradation of pollutants including waste polyethylene terephthalate (PET) plastics and plasticizers. So far, an increasing number of phthalate isomer-degrading strains have been isolated, and their degradation pathways show significant diversity. In this paper, we comprehensively review the current status of research on the degrading bacteria, degradation characteristics, aerobic and anaerobic degradation pathways, and degradation genes (clusters) of phthalate isomers, and discuss the current shortcomings and challenges. Moreover, the degradation process of phthalate isomers produces many important aromatic precursor molecules, which can be used to produce higher-value derivative chemicals, and the modification of their degradation pathways holds good prospects. Therefore, this review also highlights the current progress made in modifying the phthalate isomer degradation pathway and explores its potential for high-value applications.

Increasing the interlayer spacing and generating closed pores to produce petroleum coke-based carbon materials for sodium ion storage

Petroleum coke (PC) is a valuable precursor for sodium-ion battery (SIB) anodes due to its high carbon content and low cost. The regulation of the microcrystalline state and pore structure of the easily-graphitized PC-based carbon is crucial for creating abundant Na+ storage sites. Here we used a precursor transformation strategy to increase the carbon interlayer spacing and generate abundant closed pores in PC-based carbon, significantly increasing its Na+ storage capacity in the plateau region. This was achieved by introducing a large number of oxygen functional groups through mixed acid treatment and then using high-temperature carbonization to decompose the oxygen functional groups and rearrange the carbon microcrystallites, resulting in a transition from open to closed pores. The optimized samples provide a large reversible capacity of 356.0 mAh g−1 at 0.02 A g−1, of which approximately 93% is below 1.0 V. Galvanostatic intermittent titration (GITT) and in-situ X-ray diffraction (XRD) analysis indicate that the sodium storage capacity in the low voltage plateau region involves a joint contribution of interlayer insertion and closed pore filling processes. This study presents a comprehensive method for the development of high-performance carbon anodes using low-cost and highly aromatic precursors.

Oxygen-driven closing pore formation in coal-based hard carbon for low-voltage rapid sodium storage

The coal-derived hard carbon is considered a promising anode material for sodium-ion batteries (SIBs) due to its ample resources, low cost, and unique pore structure. However, the ordered carbon microstructure of this material leads to inferior sodium storage capacity and low initial Coulombic efficiency (ICE). Herein, we propose a strategy to inhibit over-graphitization and promote the formation of closed pores during subsequent carbonation processes through oxygen-driven carbon sheets development. The formation mechanism of closed pores in coal-based hard carbon has been systematically established, and its contribution to the capacity of the low-voltage plateau in hard carbon anode for SIBs has been explained. In-situ characterizations demonstrate that the presence of abundant closed pores and moderate graphitization provides sufficient active sites for Na+ ion pore-filling. The closed pore structure ensured the realization of a high plateau capacity, resulting in a high reversible capacity of 303.1 mA h g−1, which was significantly higher than that of the open-pore dominant carbon (161.1 mA h g−1). This study offers innovative perspectives on designing high-performance carbon anodes with closed porosity, utilizing cost-effective and highly aromatic precursors.

Production of non-natural 5-methylorsellinate-derived meroterpenoids in Aspergillus oryzae.

Fungal meroterpenoids are diverse structurally intriguing molecules with various biological properties. One large group within this compound class is derived from the aromatic precursor 3,5-dimethylorsellinic acid (DMOA). In this study, we constructed engineered metabolic pathways in the fungus Aspergillus oryzae to expand the molecular diversity of meroterpenoids. We employed the 5-methylorsellinic acid (5-MOA) synthase FncE and three additional biosynthetic enzymes for the formation of (6R,10'R)-epoxyfarnesyl-5-MOA methyl ester, which served as a non-native substrate for four terpene cyclases from DMOA-derived meroterpenoid pathways. As a result, we successfully generated six unnatural 5-MOA-derived meroterpenoid species, demonstrating the effectiveness of our approach in the generation of structural analogues of meroterpenoids.

Debottlenecking the L-DOPA 4,5-dioxygenase step with enhanced tyrosine supply boosts betalain production in Nicotiana benthamiana.

Synthetic biology provides emerging tools to produce valuable compounds in plant hosts as sustainable chemical production platforms. However, little is known about how supply and utilization of precursors is coordinated at the interface of plant primary and specialized metabolism, limiting our ability to efficiently produce high levels of target specialized metabolites in plants. L-Tyrosine is an aromatic amino acid precursor of diverse plant natural products including betalain pigments, which are used as the major natural food red colorants and more recently a visual marker for plant transformation. Here, we studied the impact of enhanced L-tyrosine supply on the production of betalain pigments by expressing arogenate dehydrogenase (TyrA) from table beet (Beta vulgaris, BvTyrAα), which has relaxed feedback inhibition by L-tyrosine. Unexpectedly, betalain levels were reduced when BvTyrAα was coexpressed with the betalain pathway genes in Nicotiana benthamiana leaves; L-tyrosine and 3,4-dihydroxy-L-phenylalanine (L-DOPA) levels were drastically elevated but not efficiently converted to betalains. An additional expression of L-DOPA 4,5-dioxygenase (DODA), but not CYP76AD1 or cyclo-DOPA 5-O-glucosyltransferase, together with BvTyrAα and the betalain pathway, drastically enhanced betalain production, indicating that DODA is a major rate-limiting step of betalain biosynthesis in this system. Learning from this initial test and further debottlenecking the DODA step maximized betalain yield to an equivalent or higher level than that in table beet. Our data suggest that balancing between enhanced supply ("push") and effective utilization ("pull") of precursor by alleviating a bottleneck step is critical in successful plant synthetic biology to produce high levels of target compounds.

Performance polyamides built on a sustainable carbohydrate core

Sustainably producing plastics with performance properties across a variety of materials chemistries is a major challenge—especially considering that most performance materials use aromatic precursors that are still difficult to source sustainably. Here we demonstrate catalyst-free, melt polymerization of dimethyl glyoxylate xylose, a stabilized carbohydrate that can be synthesized from agricultural waste with 97% atom efficiency, into amorphous polyamides with performances comparable to fossil-based semi-aromatic alternatives. Despite the presence of a carbohydrate core, these materials retain their thermomechanical properties through multiple rounds of high-shear mechanical recycling and could be chemically recycled. Techno-economic and life-cycle analyses suggest selling prices close to those of nylon 66 with a reduction of global warming potential of up to 75%. This work illustrates the versatility of a carbohydrate moiety to impart performance that can compete with that of semi-aromatic polymers across two important materials chemistries.

Oxygenated organic molecules produced by low-NOx photooxidation of aromatic compounds: contributions to secondary organic aerosol and steric hindrance

Abstract. Oxygenated organic molecules (OOMs) produced by the oxidation of aromatic compounds are key components of secondary organic aerosol (SOA) in urban environments. The steric effects of substitutions and rings and the role of key reaction pathways in altering the OOM distributions remain unclear because of the lack of systematic multi-precursor study over a wide range of OH exposure. In this study, we conducted flow-tube experiments and used the nitrate adduct time-of-flight chemical ionization mass spectrometer (NO3--TOF-CIMS) to measure the OOMs produced by the photooxidation of six key aromatic precursors under low-NOx conditions. For single aromatic precursors, the detected OOM peak clusters show an oxygen atom difference of one or two, indicating the involvement of multi-step auto-oxidation and alkoxy radical pathways. Multi-generation OH oxidation is needed to explain the diverse hydrogen numbers in the observed formulae. In particular, for double-ring precursors at higher OH exposure, multi-generation OH oxidation may have significantly enriched the dimer formulae. The results suggest that methyl substitutions in precursor lead to less fragmented OOM products, while the double-ring structure corresponds to less efficient formation of closed-shell monomeric and dimeric products, both highlighting significant steric effects of precursor molecular structure on the OOM formation. Naphthalene-derived OOMs however have lower volatilities and greater SOA contributions than the other-type of OOMs, which may be more important in initial particle growth. Overall, the OOMs identified by the NO3--TOF-CIMS may have contributed up to 30.0 % of the measured SOA mass, suggesting significant mass contributions of less oxygenated, undetected semi-volatile products. Our results highlight the key roles of progressive OH oxidation, methyl substitution and ring structure in the OOM formation from aromatic precursors, which need to be considered in future model developments to improve the model performance for organic aerosol.

Carbocation Mechanism Revelation of Molecular Iodine-Mediated Dehydrogenative Aromatization of Substituted Cyclic Ketones to Phenols.

Dehydrogenative aromatization (DA) of cyclic ketones is central to the development of functionalized aromatic precursors and hydrogen transfer-related technologies. Traditional DA strategies require precious metals with oxidants and are typically performed at high temperatures (100-150 °C) to overcome the high energy barrier of aliphatic C-H bond activation. Recently, a mild alternative approach based on I2 has been proposed to realize DA on substituted unsaturated cyclic ketones under ambient conditions. However, depending on the solvent, the product selectivity may vary between phenol ether and phenol, and the reaction mechanisms remain unclear. Herein, based on time-resolved proton nuclear magnetic resonance, DFT calculation, and mass spectrometric analyses, we established a unified mechanism to account for the product distribution. Through substrate scope and desorption electrospray ionization-mass spectrometry, we discovered the formation of a carbocation, which has been overlooked in previous studies. An expanded substrate scope study coupled with spectroscopic observation provided strong evidence to elucidate the formation mechanism and the location of the carbocation. With a renewed understanding of the mechanism, we achieved a phenolic product yield of 17-96% while controlling the selectivity. Moreover, some reactants could undergo DA in H2O, achieving 95-96% yield at below water-boiling temperature.

New Features of Laboratory-Generated EPFRs from 1,2-Dichlorobenzene (DCB) and 2-Monochlorophenol (MCP).

The present research is primarily focused on investigating the characteristics of environmentally persistent free radicals (EPFRs) generated from commonly recognized aromatic precursors, namely, 1,2-dichlorobenzene (DCB) and 2-monochlorophenol (MCP), within controlled laboratory conditions at a temperature of 230 °C, termed as DCB230 and MCP230 EPFRs, respectively. An intriguing observation has emerged during the creation of EPFRs from MCP and DCB utilizing a catalyst 5% CuO/SiO2, which was prepared through various methods. A previously proposed mechanism, advanced by Dellinger and colleagues (a conventional model), postulated a positive correlation between the degree of hydroxylation on the catalyst's surface (higher hydroxylated, HH and less hydroxylated, LH) and the anticipated EPFR yields. In the present study, this correlation was specifically confirmed for the DCB precursor. Particularly, it was observed that increasing the degree of hydroxylation at the catalyst's surface resulted in a greater yield of EPFRs for DCB230. The unexpected finding was the indifferent behavior of MCP230 EPFRs to the surface morphology of the catalyst, i.e., no matter whether copper oxide nanoparticles are distributed densely, sparsely, or completely agglomerated. The yields of MCP230 EPFRs remained consistent regardless of the catalyst type or preparation protocol. Although current experimental results confirm the early model for the generation of DCB EPFRs (i.e., the higher the hydroxylation is, the higher the yield of EPFRs), it is of utmost importance to closely explore the heterogeneous alternative mechanism(s) responsible for generating MCP230 EPFRs, which may run parallel to the conventional model. In this study, detailed spectral analysis was conducted using the EPR technique to examine the nature of DCB230 EPFRs and the aging phenomenon of DCB230 EPFRs while they exist as surface-bound o-semiquinone radicals (o-SQ) on copper sites. Various aspects concerning bound radicals were explored, including the hydrogen-bonding tendencies of o-semiquinone (o-SQ) radicals, the potential reversibility of hydroxylation processes occurring on the catalyst's surface, and the analysis of selected EPR spectra using EasySpin MATLAB. Furthermore, alternative routes for EPFR generation were thoroughly discussed and compared with the conventional model.

Systematic engineering enables efficient biosynthesis of L-phenylalanine in E. coli from inexpensive aromatic precursors

BackgroundL-phenylalanine is an essential amino acid with various promising applications. The microbial pathway for L-phenylalanine synthesis from glucose in wild strains involves lengthy steps and stringent feedback regulation that limits the production yield. It is attractive to find other candidates, which could be used to establish a succinct and cost-effective pathway for L-phenylalanine production. Here, we developed an artificial bioconversion process to synthesize L-phenylalanine from inexpensive aromatic precursors (benzaldehyde or benzyl alcohol). In particular, this work opens the possibility of L-phenylalanine production from benzyl alcohol in a cofactor self-sufficient system without any addition of reductant.ResultsThe engineered L-phenylalanine biosynthesis pathway comprises two modules: in the first module, aromatic precursors and glycine were converted into phenylpyruvate, the key precursor for L-phenylalanine. The highly active enzyme combination was natural threonine aldolase LtaEP.p and threonine dehydratase A8HB.t, which could produce phenylpyruvate in a titer of 4.3 g/L. Overexpression of gene ridA could further increase phenylpyruvate production by 16.3%, reaching up to 5 g/L. The second module catalyzed phenylpyruvate to L-phenylalanine, and the conversion rate of phenylpyruvate was up to 93% by co-expressing PheDH and FDHV120S. Then, the engineered E. coli containing these two modules could produce L-phenylalanine from benzaldehyde with a conversion rate of 69%. Finally, we expanded the aromatic precursors to produce L-phenylalanine from benzyl alcohol, and firstly constructed the cofactor self-sufficient biosynthetic pathway to synthesize L-phenylalanine without any additional reductant such as formate.ConclusionSystematical bioconversion processes have been designed and constructed, which could provide a potential bio-based strategy for the production of high-value L-phenylalanine from low-cost starting materials aromatic precursors.

First Principles Modelling of Growth of Hybrid Organic-Inorganic Films

Hybrid organic-inorganic materials fabricated with molecular layer deposition (MLD) are a special class of materials that are attracting great interest in many economically and socially relevant technological applications due to their diphasic and tunable organic-inorganic structure. Despite the growing interest in these hybrid materials, knowledge around relevant precursor chemistries and reaction mechanisms, as well as details of many determined experimental results are unknown. Density functional theory (DFT) has proven to be a powerful tool to investigate and understand the atomic level details of the precursor chemistry and address aspects of the MLD experiments.In our work, we use first principles DFT calculations to examine key steps in the mechanism of hybrid film deposition through MLD by modelling precursor-surface and precursor-precursor reactions. We explore the growth mechanism of aluminium and titanium containing hybrid films, namely alucones and titanicones. Both materials are of high interest for passivation layers in batteries. For alucones we investigate in detail the chemistry of the MLD process between the post-trimethylaluminium (TMA) pulse methyl-terminated Al2O3 surface with aromatic compounds with hydroxy and/or amino groups as reactive groups: hydroquinone (HQ), 4-aminophenol (AP) and p-phenylenediamine (PD). Double reactions of HQ, AP and PDA with the Al2O3 surface are explored in detail to assist the interpretation of the experimental findings regarding the differences found for hybrid films grown with aromatic and aliphatic organic precursors. DFT calculations show that in contrast to aliphatic organics, an upright configuration will be present for HQ, AP and PD so that the molecules are self-assembled in an upright configuration, which leads to thicker hybrid films. We predict that aromatic molecules are the best choice for stable hybrid films and their chemistry can be manipulated without degrading stability. [1]We also investigate in detail the chemistry between the most common titanium precursors, namely titanium tetrachloride (TiCl4) and tetrakis(dimethylamido)titanium (Ti(DMA)4), and ethylene glycol (EG) and glycerol (GL) as the organic precursors for the fabrication of titanicone films. We analyse the impact of the substrate on the initial MLD reactions in titanicone film growth using three different surface models: anatase TiO2, rutile TiO2 and Al2O3. This work highlights the role of the phase of TiO2 and Ti-containing precursors in production of titanicone films and provides motivation to develop a new rutile TiO2 based hybrid film suggesting that the desired film growth, flexibility and stability can be achieved. [2][1] A. Muriqi, M. Karppinen and M. Nolan, Role of terminal groups in aromatic molecules on the growth of Al2O3-based hybrid materials, Dalton Transactions, 2021, 50, 17583-17593. doi.org/10.1039/D1DT03195C.[2] Arbresha Muriqi and Michael Nolan, “Role of Titanium and Organic Precursors in Molecular Layer Deposition of “Titanicone” Hybrid Materials”, Beilstein Journal of Nanotechnology, 2022, 13, 1240–1255. doi.org/10.3762/bjnano.13.103.

Organocatalytic aromatization-promoted umpolung reaction of imines.

The umpolung functionalization of imines bears vast synthetic potential, but polarity inversion is less efficient compared with the carbonyl counterparts. Strong nucleophiles are often required to react with the N-electrophiles without catalytic and stereochemical control. Here we show an effective strategy to realize umpolung of imines promoted by organocatalytic aromatization. The attachment of strongly electron-withdrawing groups to imines could enhance the umpolung reactivity by both electronegativity and aromatic character, enabling the direct amination of (hetero)arenes with good efficiencies and stereoselectivities. Additionally, the application of chiral Brønsted acid catalyst furnishes (hetero)aryl C-N atropisomers or enantioenriched aliphatic amines via dearomative amination from N-electrophilic aromatic precursors. Control experiments and density functional theory calculations suggest an ionic mechanism for the umpolung reaction of imines. This disconnection expands the options to forge C-N bonds stereoselectively on (hetero)arenes, which represents an important synthetic pursuit, especially in medicinal chemistry.