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The Beckmann rearrangement has been predominantly studied for the synthesis of amide and lactam. By strategically using the in situ generated Appel's salt or Mitsunobu's zwitterionic adduct as the dehydrating agent, a series of Beckmann rearrangement and following cascade reactions have been developed herein. The protocol allows the conversion of various ketoximes into amide, thioamide, tetrazole and imide products in modular procedures. The generality and tolerance of functionalities of this method have been demonstrated.

Catechol pollutants (CATPs) serving as chelating agents could coordinate with many metal ions to form various CATPs-metal complexes. Little information is available on the effects of complexation of metal ions on CATPs degradation. This work presents a systematical study of •OH-mediated degradation of catechol and catechol-metal complexes over the whole pH range in advanced oxidation processes (AOPs). Results show that the pH-dependent complexation of metal ions (Zn2+, Cu2+, Ti4+ and Fe3+) promotes the deprotonation of catechol under neutral and even acidic conditions. The radical adduct formation (RAF) reactions are both thermodynamically and kinetically favorable for all dissociation and complexation species, and OH/ O− group-containing C positions are more vulnerable to •OH attack. The kinetic results show that the complexation of the four metal ions offers a wide pH range of effectiveness for catechol degradation. At pH 7, the apparent rate constant (kapp) values for different systems follow the order of catechol+Ti4+ ≈ catechol+Zn2+ > catechol+Cu2+ > catechol+Fe3+ > catechol. The mechanistic and kinetic results would greatly improve our understanding of the degradation of CATPs-metal and other organics-metal complexes in AOPs. The toxicity assessment indicates that the •OH-based AOPs have the ability for decreasing the toxicity and increasing the biodegradability during the processes of catechol degradation.

Two pairs of enantiomeric diarylheptanoid-phenylpropanoid adducts bearing a cyclohexenone core, (±)-saccardianones A and B (1 and 2), an alkaloidal diarylheptanoid-phenylpropanoid adduct bearing a 4-piperidone core, (±)-saccardianine A (3), a pair of enantiomeric dimeric diarylheptanoid alkaloids bearing a tetrahydropyridine core, (±)-saccardianine B (4), and a suspected degradation product, saccardianine C (5), in addition to a known diarylheptanoid, platyphyllenone (6), were isolated from the leaves of Pellacalyx saccardianus. Their chemical structures were elucidated based on detailed analyses of the NMR and MS data. The structure of (±)-(1) was also confirmed by X-ray diffraction analysis. Compounds (±)-2 and 6 exhibited selective cytotoxicity towards the AsPC-1 and PANC-1 pancreatic cancer cell lines, respectively.

Photocatalytic sustainable fuel production attracted extensive attention because of the urgent need of the society to shift from fossil fuels to solar fuels. Herein, the synthesis of hexagonal rosettes of g-C3N4 with an efficient performance toward hydrogen evolution and hydrogen peroxide production as the two kinds of solar fuels were reported. The hexagonal rosettes of g-C3N4 were simply fabricated via controlled solid-state polymerization of three-dimensional hexagonal rosettes of cyanuric acid-melamine adduct at 500 °C. The hexagonal rosettes of g-C3N4 showed an amorphous nature with an extremely high surface area of 400 m2 g−1. Also, the as-obtained catalyst demonstrated remarkable photocatalytic activity in hydrogen production of 1285 μmol g−1 h−1 and hydrogen peroxide production of 150 μmol g−1 h−1. The mechanism for the polymerization process of the cyanuric acid-melamine (CM) complex to hexagonal rosettes of g-C3N4 was thoroughly described employing electron microscopy tools. This study identified that the CM complex condensation is accomplished via a dehydration process by producing a highly condensed and active structure of g-C3N4, which is different from the previously reported condensation mechanism of the melamine and its derivatives performed through a deamination process.

A simple and economical method for modifying chitosan based on non-catalytic direct condensation reaction between chitosan and phenolic acids “Gallic and Caffeic acids” has been developed to produce condensation adduct resins RI and RII. The resins structure and morphology were confirmed by physical and chemical tools such as FTIR, SEM, EDX, XRD elemental analysis, TGA, water regain, dissociation in acidic medium, and point of zero charge. The new resins were evaluated as silver ions adsorbents. Factors affecting adsorption, as well as kinetics, equilibrium, and thermal properties of adsorption, were studied using conventional equations. The new resins showed more efficient removal of toxic silver ions from the aqueous medium than parent chitosan polymer. The maximum adsorption capacity amounted to 67.5, 300, and 278 mg/g with removal efficiency reaching 22.5%, 100%, and 92.66% for chitosan, RI, and RII; respectively at pH 6.5 and initial silver concentration 300 mg/L. The new resins showed spontaneous chemisorption toward silver ions with exothermic nature for RI, and endothermic nature for RII. The new condensation adduct resins showed good re-use ability reaching 83% and 67% for RI and RII; respectively, by using 0.01 M nitric acid solution.

Most studies on SO2 capture using ionic liquids (ILs) have been carried out under mild conditions (e.g., about 1 bar of SO2 and 20–40 °C). However, these ILs only exhibit a fraction of their original SO2 uptake under harsher conditions, i.e., much lower SO2 partial pressure and evidently higher temperature (e.g., ≤0.2 mbar of SO2 and ≥110 °C). In this work, we screen 127 reported ILs for multi-molar SO2 absorption under the harsher conditions, covering nearly all the chemical space explored of the SO2 capturing IL. A unique cooperative anion-SO2 interaction mode with two forms (the insertion adduct and the ringed adduct) has been identified for branched anions, where SO2 acts as both acid and base to attack different reactive sites on anions. The simulated Langmuir isotherms further help screen out potential sorbents (amino-based branched singly charged anions with an Al atom as the center and carboxyl-based divalent anions) with both high overall capacity and high per-cycle absorption capacity. The energies of the reacting orbitals of the anions are linearly correlated to their SO2 binding energies. This work provides new insights for the design of task-specific ILs under harsh conditions.

Three sesquiterpene-based meroterpenoids psiguamers A–C (1–3) with new skeletons were isolated from Psidium guajava leaves. Compounds (±)-1 and (±)-2 were two pairs of humulene-derived meroterpenoids bearing a rare methylated benzoylphloroglucinol unit, while 3 was an unprecedented adduct of bicyclogermacrene and methylated benzoylphloroglucinol. Their structures were determined based on comprehensive analyses of spectroscopic data, calculated electronic circular dichroism (ECD) spectra, total synthesis, and X-ray crystallographic data. The biomimetic synthesis of (±)-1 and (±)-2 was achieved. Compound (+)-1 exhibited cytotoxic activities against five human tumor cell lines (HCT-116, HepG2, BGC-823, A549, and U251), with IC50 values of 2.94, 9.01, 6.45, 5.42, and 5.33 μmol/L, respectively.

Although C5H4 isomers are detected in flames, they are not thoroughly incorporated into detailed chemical kinetics models (DCKMs). Here we use RRKM/ME modelling to simulate C5H4 + H reactions on a C5H5 potential energy surface. Kinetic studies indicate that C3H3 + C2H2 is the main fate but fall-off from the initial adduct isomer back to C5H4 + H cannot be ignored at relevant combustion temperatures of 900 to 2000 K. Calculated rate coefficient expressions were incorporated into a DCKM for a toluene flame, along with updates to other relevant reactions from the recent literature, particularly the open-chain 1-vinylpropargyl radical, l-C5H5. Obtained species mole fractions were found to be in good agreement with published experimental data for a low-pressure toluene flame, with a significant improvement in predicted concentration of the cyclopentadienyl radical. The presented DCKM will allow for further reactions of C5Hx species such as 1-vinylpropargyl to be included in combustion simulations.

A novel Zn-based metal–organic framework Zn (dobdc) (datz) [Zn2(H2dobdc) (datz)2·1.5DMF] with plentiful hydrogen bond donors (HBD) groups was facilely synthesized from mixed ligands. The dual activation of metal Zn sites and HBD groups for epoxides by forming Zn–O adduct and hydrogen bonds facilitated the ring-opening of epoxide substrate, which is critical for the subsequent CO2 fixation. Also, the existence of micropores and N-rich units in Zn (dobdc) (datz) afforded affinity towards CO2, which is beneficial to further improvement on catalytic CO2 conversion performance. Satisfactorily, Zn (dobdc) (datz)/Bu4NBr system was proved efficient heterogeneous catalyst for the CO2 cycloaddition with epoxides, and 98% propylene carbonate yield was obtained under mild conditions (80 °C, 1.5 MPa and solvent-free). In addition, Zn (dobdc) (datz)/Bu4NBr exhibited remarkable versatility to different epoxides and could be completely recycled over six runs with high catalytic activity. The highly stable, easily recycle and solvent-free Zn-based MOF reported here displays eco-friendly and efficient performance to CO2 conversion.

The antipyrine linked E allylic ester (BH-AP) ONO tridentate was synthesized, using acetate of Baylis-Hillman Adduct (BH) and antipyrine (AP) through SN2′ allylic substitution reaction. The newly synthesized ligand was characterized using IR and NMR spectroscopy. The ligand BH-AP was analyzed using UV–Visible and fluorescence techniques for its selective metal ion recognition properties. The emission spectroscopy exhibited the sensitivity and selectivity of the sensor for Zn2+ ion by significantly quenching the fluorescence intensity upon excitation at 268 nm. The 1:1 ratio binding stoichiometry and the binding constant value of 4.5796 × 10−6 M−1 were obtained for the ligand BH-AP with Zn2+ion. The appropriate combination of materials-AP, Zn2+and pH found to be suitable for NOR logic gate application.

Oxazolidinones and α-hydroxyl ketones are two series of fine chemicals that have been generally utilized in biological, pharmaceutical, and synthetic chemistry. Herein, a AgNO3/ionic liquid (IL) catalytic system was developed for the simultaneous synthesis of these compounds through the atom-economical three-component reactions of propargyl alcohols, 2-aminoethanols, and CO2. Notably, this system behaved excellent catalytic activity with the lowermost metal loading of 0.25 mol%. Meanwhile, it is the first reported metal-catalyzed system that could efficiently work under atmospheric CO2 pressure and be recycled at least five times. Evaluation of the green metrics proved the AgNO3/IL-catalyzed processes to be relatively more sustainable and greener than the other Ag-catalyzed examples. Further mechanistic investigations revealed the derivative active species of N-heterocyclic carbene (NHC) silver complexes and CO2 adducts generated during the process. Subsequently, their reactivity in this reaction was assessed for the first time, which was finally identified as beneficial for the catalytic activity.

The tenfold lowering in binding energy for TU-Tyrosine in immobilized urease (Kb: 4.7 × 103) with respect to the native enzyme (Kb: 6.5 × 104) begets easy desorption of thiourea (TU) by glucose (GL) with an eventual formation of a more strong TU- GL adduct; that rejuvenates the kit-material ready for the subsequent cycle(s). The sorption-desorption heeds fluorescence turn-off and turn-on in DCM for selective sensing of TU- GL pair at their respective linear range of concentration 2.5–26.1 ppm and 2.36–11.57 ppm. The process was found to be static (KSV ≥ 2.25 × 103 L mol−1), exothermic (ΔH: -0.08 kJ mol−1), spontaneous (ΔG: -21.1 kJ mol−1) and marginally entropy gaining (ΔS: 0.07 kJ mol−1 K−1). The ‘bulk material’ (200 ± 20 μm) brilliantly preconcentrates TU with an enrichment factor of 106.2 after its selective extraction at near-neutral pH from a large volume sample (800 mL) of low concentration (30 ppm). A very dilute solution (0.05 mmol L−1) of GL at minimum volume (6 mL) acts as a stripping agent and provides a longer life (200 cycles with good extraction efficiency) to the material. The method was found to be efficient in the analysis of fruit juice as a real sample.

Diels-Alder reaction is a useful method for modifying the surface of carbon materials. In this work, we functionalized activated carbon with a large number of carboxyl groups using the Diels-Alder reaction. Polyaromatic structure of activated carbon acted as a diene for addition of maleic anhydride (MA) that acted as a dienophile. Upon hydrolysis of the anhydride group in the adduct, vicinal carboxyl groups were formed. The formation of carboxyl groups by Diels-Alder reaction was proved by FTIR, solid-state 13C NMR, CO and CO2 evolution from TPD and Boehm titration. Titration results showed that the number of carboxyl groups increased from 0.09 mmol g−1 to 3.06 mmol g−1. DFT calculation showed that the concave site of the armchair edge on carbon surface was the most favorable for the Diels-Alder addition. The formation of exo-adduct was preferred with a reaction energy (ΔE) of −24 kJ mol−1. The synthesized catalyst was tested for acid-catalyzed hydrolysis of cellobiose. The catalyst showed higher activity than a catalyst prepared by oxidation in the presence of air.

Aggregation of saturated mesocyclic diamine 1,4-diazacycloheptane (dach) or piperazine (pipz) and diversiform carboxylic acids with mono- or di-carboxyls yields a series of novel binary supramolecular adducts via two-point molecular recognition. All the supramolecular assemblies were obtained by solvent evaporation method from different media. X-ray single-crystal diffraction analyses reveal that these supramolecular moieties present 1D chain motif, 2D flat, corrugated sheet structures and 3D CdSO4, pillar-layered networks through carboxylate-amide N–H⋯O, as well as its proton transfer form N+–H⋯O−, carboxyl head to tail O–H⋯O, and extended hydrogen-bonding interactions. Their compositions and structures were also confirmed by Fourier transform infrared (FT-IR) spectroscopy. Thermal stability of these binary crystalline adducts has been investigated by thermogravimetric analysis (TGA), suggesting similar thermal stabilities.

The effects of metalation process by inorganic compounds containing Au, Pt and Ru on protein structure and on conformation and flexibility of the residues involved in the metal compound binding have been here investigated by analysing 204 structures of protein/metallodrug adducts and the corresponding metal-free forms. The overall structure of the proteins is not significantly affected by the metal label. 162 non-redundant protein residues involved in Au, Pt and Ru coordination have been identified. In the metal-free protein structures these residues often belong to α-helical regions and show low flexibility. They do not necessarily belong to outer layers of the protein structure. In the majority of the adducts, the side chains of these residues adopt a conformation that is similar to that observed in the metal-free protein. The metal coordination reduces their solvent accessible surface area without altering their overall flexibility. These results could be useful for the prediction of residues able to bind Au, Pt and Ru compounds.

Xenobiotic electrophiles can form covalent adducts that may impair protein function, damage DNA, and may lead a range of adverse effects. Cumulative neurotoxicity is one adverse effect that has been linked to covalent protein binding as a Molecular Initiating Event (MIE). This paper describes a mechanistic in silico chemical screening approach for neurotoxicity based on Hard and Soft Acids and Bases (HSAB) theory. We evaluated the applicability of HSAB-based electrophilicity screening protocol for neurotoxicity on 19 positive and 19 negative reference chemicals. These reference chemicals were identified from the literature, using available information on mechanisms of neurotoxicity whenever possible. In silico screening was based on structural alerts for protein binding motifs and electrophilicity index in the range of known neurotoxicants. The approach demonstrated both a high positive prediction rate (82-90 %) and specificity (90 %). The overall sensitivity was relatively lower (47 %). However, when predicting the toxicity of chemicals known or suspected of acting via non-specific adduct formation mechanism, the HSAB approach identified 7/8 (sensitivity 88 %) of positive control chemicals correctly. Consequently, the HSAB-based screening is a promising approach of identifying possible neurotoxins with adduct formation molecular initiating events. While the approach must be expanded over time to capture a wider range of MIEs involved in neurotoxicity, the mechanistic nature of the screen allows users to flag chemicals for possible adduct formation MIEs. Thus, the HSAB based toxicity screening is a promising strategy for toxicity assessment and chemical prioritization in neurotoxicology and other health endpoints that involve adduct formation.

Phosphatidylserine decarboxylases (PSDs) catalyze the conversion of phosphatidylserine (PS) to phosphatidylethanolamine (PE), a critical step in membrane biogenesis and a potential target for development of antimicrobial and anti-cancer drugs. PSD activity has typically been quantified using radioactive substrates and products. Recently, we described a fluorescence-based assay that measures the PSD reaction using distyrylbenzene-bis-aldehyde (DSB-3), whose reaction with PE produces a fluorescence signal. However, DSB-3 is not widely available and also reacts with PSD's substrate, PS, producing an adduct with lower fluorescence yield than that of PE. Here, we report a new fluorescence-based assay that is specific for PSD and in which the presence of PS causes only negligible background. This new assay uses 1,2-diacetyl benzene/β-mercaptoethanol, which forms a fluorescent iso-indole-mercaptide conjugate with PE. PE detection with this method is very sensitive and comparable with detection by radiochemical methods. Model reactions examining adduct formation with ethanolamine produced stable products of exact masses (m/z) of 342.119 and 264.105. The assay is robust, with a signal/background ratio of 24, and can readily detect formation of 100 pmol of PE produced from Escherichia coli membranes, Candida albicans mitochondria, or HeLa cell mitochondria. PSD activity can easily be quantified by sequential reagent additions in 96- or 384-well plates, making it readily adaptable to high-throughput screening for PSD inhibitors. This new assay now enables straightforward large-scale screening for PSD inhibitors against pathogenic fungi, antibiotic-resistant bacteria, and neoplastic mammalian cells.

Targeting redox vulnerability of cancer cells by pro-oxidants capable of generating reactive oxygen species (ROS) has surfaced as an important anticancer strategy. Due to the intrinsic narrow therapeutic window and other dangerous side effects of ROS generation, it is highly needed and challenging to develop pro-oxidative anticancer agents (PAAs) with high selectivity for generating ROS in cancer cells. Herein we report a hydrogen peroxide (H2O2)-activated Cu(II) pro-ionophore strategy to develop naphthazarin (Nap) as such type of PAAs based on the H2O2-mediated conversion of boronate to free phenol. The boronate-protected Nap (PNap) can exploit increased levels of H2O2 in HepG2 cells to in situ release Nap followed by its efflux via conjugation with reduced glutathione (GSH), allowing that the Nap-GSH adduct works as a Cu(II) ionophore to induce continuously GSH depletion via a reduction-dependent releasing of Cu(I) by GSH. This strategy endows PNap with the unprecedented ability to hit multi-redox characteristics (increased levels of H2O2, GSH and copper) of HepG2 cells, leading to ROS generation preferentially in HepG2 cells along with their selective death.

The major problem identified in carbon-based mixed cation perovskite solar cells (PSCs) is the selection of a suitable solvent for single-step solution-processed perovskite deposition in order to promote their scalable production. Herein we report a detailed study on the selection of appropriate solvent for the one-step deposition of cesium-formamidinium lead iodide (Cs0.1FA0.9PbI3) perovskite via Lewis acid-base adduct approach for fully printable mesoporous PSCs with mesoporous TiO2/ZrO2/C architecture. Highly reproducible Cs0.1FA0.9PbI3 solar cells were fabricated via adducts of PbI2 with eco-friendly dimethyl sulfoxide (DMSO). The best cells fabricated with the above approach yielded a photoconversion efficiency (PCE) of 12.33% for a small area device (active area: 0.09 cm2) and 10.1% for a large area device (active area 0.7cm2). The average power conversion efficiency for 62 PSCs was found to be 10.5% under an AM 1.5G illumination. Finally, the mixed cation perovskite in carbon architecture using the Lewis acid-base adduct approach is remarkably stable, with less than 1% change from the initial PCE after 1800h of storage under dark ambient conditions (25 °C, 60–70% RH).

Tuberculosis has attracted increased attention worldwide due to its high morality and its resistance to treatment with traditional antibacterial drugs. The l,d-transpeptidase LdtMt2 confers resistance to traditional β-lactams and is considered a target for anti-Tuberculosis treatment. Carbapenems are proposed to inhibit Mycobacterium tuberculosis by repressing the activity of LdtMt2. The interaction mechanisms between LdtMt2 and carbapenems have been revealed by LdtMt2-carbapenem adduct structures along with various biochemical assays. Interestingly, the lack of the 1-β-methyl group in imipenem may be related to its high binding ability to LdtMt2. However, there is limited evidence on the interaction mode of LdtMt2 and panipenem, another carbapenem lacking the 1-β-methyl group. Herein, we identified the biochemical features of panipenem binding to LdtMt2. We further suggest that the presence of the 1-β-methyl group in carbapenems is indeed related to the ligand affinity of LdtMt2 and that the presence of the Y308 and Y318 residues in LdtMt2 stabilized the conformation of the LdtMt2-carbepenem adduct. Our research provides a structural basis for the development of novel carbapenems against L,D-transpeptidases.

Covalent or non-covalent heterogeneous multimerization of molecules associated with extracts from biological samples analyzed via LC-MS is quite difficult to recognize/annotate and therefore the prevalence of multimerization remains largely unknown. In this study, we utilized 13C labeled and unlabeled Pichia pastoris extracts to recognize heterogeneous multimers. More specifically, between 0.8% and 1.5% of the biologically-derived features detected in our experiments were confirmed to be heteromers, about half of which we could successfully annotate with monomeric partners. Interestingly, we found specific chemical classes such as nucleotides to disproportionately contribute to heteroadducts. Furthermore, we compiled these compounds into the first MS/MS library that included data from heteromultimers to provide a starting point for other labs to improve the annotation of such ions in other metabolomics data sets. Then, the detected heteromers were also searched in publicly accessible LC-MS datasets available in Metabolights, Metabolomics WB, and GNPS/MassIVE to demonstrate that these newly annotated ions are also relevant to other public datasets. Furthermore, in additional datasets (Triticum aestivum, Fusarium graminearum, and Trichoderma reesei) our developed workflow also detected 0.5% to 4.9% of metabolite features to originate from heterodimers, demonstrating heteroadducts to be present in metabolomics studies at a low percentage.

The reaction of chloral or dichloro(phenyl)acetaldehyde N-arylsulfonylimines with cyclopentadiene, depending on the reaction conditions, affords either Diels–Alder adducts, 2-arylsulfonyl-2-azabicyclo[2.2.1]hept-5-enes, or unexpectedly new amidoalkylated derivatives of cyclopentadiene, N-[(cyclopentadienyl)(polychloromethyl)methyl]arenesulfonamides.

(±)-Magoilgomer A [(±)-1] and magoilgomer B (2) were identified from the bark of Magnolia officinalis var. biloba. (+)-1 and (−)-1 were a pair of novel biphenyl derivatives featuring three C6-C3 subunits. 2 was an unprecedented adduct containing magnolol and honokiol. These three oligomers possessed new parallel mode which should be biosynthesized from the coupling of three or four C6-C3 subunits. The structures of (±)-1 and 2 were elucidated based on the spectroscopic data analyses and electronic circular dichroism (ECD) calculations. 2 exhibited neuroprotective effects of oxygen glucose deprivation-induced SK-N-SH cell injury.

An adduct of ZnII pivalate with N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene has been prepared and characterized by X-ray diffraction analysis, NMR spectroscopy and DFT calculations. The compound preserves mononuclear structure in solution and does not switch the coordination mode from normal to abnormal.

The novel hexamethylenetetramine benzilic acid (HMTBA) adduct single crystal was synthesized by slow evaporation solution growth technique. The HMTBA crystal was confirmed by single crystal XRD and Further, the structure was investigated by various spectroscopic techniques such as FT-IR, UV–Vis, 1H, 13C NMR, Powder XRD spectroscopy and Z-scan studies. Thermal properties of the HMTBA was studied by using thermo-gravimetric analysis (TGA) and it was stable up to 187.6 °C. In addition, the newly synthesized HMTBA adduct was studied for biological application.

We found recently that benzohydroxamic acid (BHA) could detoxify the chlorinated quinoid carcinogens via an unusual Lossen rearrangement reaction. However, it is not clear what would happen when the nitrogen hydrogen of BHA was substituted with methyl and other alkyl groups. Here we show that N-methyl benzohydroxamic acid (N-MeBHA, a simple model compound for the classic iron-chelator deferoxamine, which is a typical N-alkyl trihydroxamic acid) could react with 2,5-dichloro-1,4-benzoquinone (DCBQ) to form a relatively stable initial carbon-oxygen bonding conjugation intermediate CBQ-O-N-MeBHA. However, the major final product was identified, unexpectedly, as a carbon-nitrogen bonding conjugate CBQ(OH)-N(CH3)-COAr, which is the rearranged isomer of CBQ-O-N-MeBHA. Interestingly, a new 18-line nitrogen-centered radical and a carbon-centered quinone ketoxy radical were observed by the ESR spin-trapping method, which was further confirmed by HPLC-MS and 15N-isotope labeling methods. We further found that both new DNA adducts and DNA strand breaks could be produced by the reactive nitrogen-centered radical. Taken together, we propose that the reaction between DCBQ and N-MeBHA was not via the Lossen rearrangement, but rather through a novel radical homolysis and recoupling pathway. Analogous results were observed for other chlorinated quinones and N-alkyl hydroxamic acids including the widely-used trihydroxamate iron-chelating drug deferoxamine. This represents the first report of unexpected radical pathway for the reaction between chlorinated quinones and N-alkyl hydroxamic acids under normal physiological conditions, which may have broad biological and environmental significance for future study of carcinogenic chloroquinones and hydroxamic acid drugs.

Rapid detection of trace level amphetaminic drug compounds in urine is essential to monitor consumption of these abuse drugs by athletes. In this work, the amphetaminic drug compounds were spiked in human urine and analyzed using headspace – dielectric barrier discharge (DBD) ionization-mass spectrometry method. In the headspace method, the urine spiked drug compound was treated with alkali solution, thus the free base amphetaminic molecules were released into the gas phase. The gaseous molecules were then ionized by the DBD ion source placed in front of the mass spectrometer inlet under ambient condition. This method provided comparable sensitivity with the solid-phase microextraction (SPME) in analysis of the amphetaminic compounds where no derivatization or adduct formation was required. The present method also facilitated the sensitivity enhancement with about one order of magnitude in urine compared to standard solution. Carbonate alkali solution showed the highest sensitivity for detection of the drug compounds in urine and the sensitivity was enhanced by using NH3. The limits of detection (LODs) of the various amphetaminic molecules were found to be in the range of 0.10–0.80 ng/mL for standard solutions while those for urine were in the range of 0.04–0.40 ng/mL. The analytical figures of merit of this method were evaluated under ambient condition using suitable internal standard. Results suggested the suitability of this method for analytical routine work in detection of amine-based drugs in doping test and/or in forensic laboratories. A mechanism of enhanced sensitivity by the ammoniated carbonate alkali solution in urine is also discussed. Keywords: Amphetaminic drugs, Headspace method, Ambient mass spectrometry, Urine analysis, Enhanced sensitivity

The globally increasing demands for polymer materials stimulate the significantly intense attention focused on the Lewis pair polymerization (LPP) of various polar vinyl monomers catalyzed by Lewis pairs (LPs) composed of Lewis acid (LA) and Lewis base (LB). According to the degree of interaction between LA and LB, LPs could be divided into classical Lewis adduct (CLA), interacting Lewis pair (ILP) and frustrated Lewis pair (FLP). Regulation of the Lewis basicity, Lewis acidity, and steric effects of these LPs has a significant impact on the polymer chain initiation, propagation and termination as well as chain transfer reaction during polymerization. Compared with other polymerization strategies, LPP has shown several unique advantages towards the polymerization of polar vinyl monomers such as high activity, control or livingness, mild conditions, and complete chemo- or regioselectivity. We will comprehensively review the recent advances achieved in the LPP of polar vinyl monomers according to the classification of the employed LPs based on different LAs, by highlighting the key polymerization results, polymerization mechanisms as well as the currently unmet challenges and the future research directions of LPP chemistry.

An immobilized p-sulfonic acid calix[4]arene was synthesized on the surface of silica-coated Fe3O4 nanoparticles. Due to the combination of the magnetic recovery and the acid properties, it acted as a robust, safe and environmentally friendly catalyst for the one-pot synthesis of Biginelli adducts under microwave irradiation and solvent-free conditions. A series of Biginelli adducts were obtained in moderate to excellent yields, and most importantly, the catalyst could be easily recovered by an external magnet and reused five times without significant loss of catalytic activity (ca. 80% yield for all reuses using 0.64 mol% of the catalyst). Keywords: Fe3O4 nanoparticles, p-sulfonic acid calix[4]arene, Magnetic acid catalyst, Biginelli adducts

The promising biomedical applications of silver complexes stimulated the researchers to test these compounds against cancer. The present research work was designed to achieve this goal. In this work, a series of 5-methyl benzimidazole based N-Heterocyclic carbene ligands and respective silver(I) complexes were synthesized and tested on cancer cell lines to assess their anticancer activity. Unsymmetrically substituted benzimidazole was found unique in its reactivity and generation of a single product during NHC ligand formation was only possible after two successive alkylations with same alkyl halide. The corresponding Ag(I)-NHC adducts were obtained by in situ deprotonation of the NHC ligands. Synthesized compounds were characterized by various physcio-chemical and spectroscopic methods. Single crystal X-ray diffraction study of complex 7 revealed its mononuclear structure. Preliminary in vitro anticancer study of azolium salts and respective Ag(I)-NHC complexes against human breast cancer (MDA-MB-231), colon cancer (HCT-116) and normal endothelial cells (EA.hy926) cells revealed that all the compounds are more cytotoxic to cancer cells than normal cells and the complexes are relatively more potent compared to the corresponding NHC ligands. It was found that increased chain length and presence of methyl substituent on benzimidazole ring enhance the biopotency of Ag(I)-NHC complexes. The synthesized compounds were further studied for pro-apoptotic mechanism of action via Rhodamine 123 test. The tested compounds were found to induce apoptosis via extrinsic mitochondrial pathway. Keywords: Metallodrugs, Unsymmetrical, Deprotonation, Cell lines

Mass spectrometry-based approaches enable us to capture changes in the metabolome in biological systems with high sensitivity and resolution. But global MS-based profiling of the bile acids (BAs) submetabolome is still a challenging task. Particularly for unconjugated BAs, the collision-induced dissociation (CID) fragment ions showed low ion intensities which were insufficient for analysis. This study is aimed at the development of an anion attachment MS-based approach for pseudotargeted profiling of the BAs submetabolome. We demonstrated that anion attachment MS with the combination use of ammonia fluoride (NH4F) and formate could provide stable anionic adduct ([M + HCOO]−) with good MS responses for unconjugated BAs. A mechanistic study revealed that the underlying rationale is due to the NH4F-induced approximate matching of attractions between BAs and anion for the 24-carboxyl hydrogen. This 24-carboxyl hydrogen regioselectivity is useful to screen for potential unconjugated BAs from the biological matrix. The stability and regioselectivity of anion attachment allowed the establishment of SRM transitions for unconjugated BAs for the first time. To profile conjugated BAs that come from the conjugation of glycine or taurine at 24-carboxyl hydrogen, specific precursor/fragment ion transitions were used for the detection. Finally, SRM-based UPLC-MS/MS method was developed for the pseudotargeted profiling of the BAs submetabolome with good linearity (r2 > 0.995) and high sensitivity (0.20–1.37 ng mL−1 for LLOQ). With this method, a total of 83 BAs, covering 45 unconjugated BAs and 38 conjugated BAs, were successfully determined in different biosamples from experimental colitis mice. The BAs metabolism homeostasis was disrupted by colitis, characterized by the decreased BAs levels in serum and excessive BAs accumuation in the gall bladder and colon. Overall, the present anion attachment MS-based approach is sufficiently sensitive and robust to comprehensively measure various BAs.

The mechanisms of the tandem sequential [4 + 2]/[3 + 2] and [3 + 2]/[4 + 2] cycloaddition sequences involving an ester, cyclooctatetraene (COTE), and cyclic and acyclic nitrones for the formation of a diverse range of isoxazolidine derivatives and other synthetic precursors are reported. A thorough exploration of the PES has characterized several regio-, stereo- and enantio-selective mechanistic channels involved in these reactions. A perturbation molecular orbital (PMO) analysis been employed to rationalize the results. It has also been found that the initial electrocyclic ring closure of the COTE is the rate-determining step in the tandem sequential [4 + 2]/[3 + 2] addition sequence. The thermolytic breakdown of the tandem adducts to subsequent monocyclic, bicyclic and tricyclic adducts occurs generally with very high activation barriers making it an inconvenient synthetic approach. The different reactivity of all the three double bonds present in the dipolarophile is reported. Finally, the mechanistic possibilities of [3 + 2]/[4 + 2] addition sequences involving the same reaction components in the case of cyclic and acyclic nitrones are explored extensively. The results suggest a novel and convenient routes for obtaining products of high selectivity with less energetic requirements. In some instances, new cycloadducts hitherto unreported are obtained.

International audience; Mycobacterial KGD, the thiamine diphosphate (ThDP)-dependent E1o component of the 2-oxoglutarate dehydrogenase complex (OGDHC), is known to undergo significant conformational changes during catalysis with two distinct conformational states, previously named as the early and late state. In this work, we employ two phosphonate analogues of 2-oxoglutarate (OG), i.e. succinyl phosphonate (SP) and phosphono ethyl succinyl phosphonate (PESP), as tools to isolate the first catalytic steps and understand the significance of conformational transitions for the enzyme regulation. The kinetics showed a more efficient inhibition of mycobacterial E1o by SP (Ki 0.043 ± 0.013 mM) than PESP (Ki 0.88 ± 0.28 mM), consistent with the different circular dichroism spectra of the corresponding complexes. PESP allowed us to get crystallographic snapshots of the Michaelis-like complex, the first one for 2-oxo acid dehydrogenases, followed by the covalent adduction of the inhibitor to ThDP, mimicking the pre-decarboxylation complex. In addition, covalent ThDP-phosphonate complexes obtained with both compounds by co-crystallization were in the late conformational state, probably corresponding to slowly dissociating enzyme-inhibitor complexes. We discuss the relevance of these findings in terms of regulatory features of the mycobacterial E1o enzymes, and in the perspective of developing tools for species-specific metabolic regulation.

The isomeric structures formed by the interaction of PF5 and PCl5 with up to four water molecules were theoretically examined by employing the MP2 method and the aug-cc-pVDZ basis set. The additional effects of surrounding water molecules were approximated by employing the polarized continuum solvation model (PCM) within a self-consistent reaction field treatment. The calculations indicate that the global minimum resulting from the interaction of PF5 and one H2O molecule corresponds to the PF5–H2O adduct and remains the most stable isomer after addition of second and third H2O, whereas the presence of fourth H2O molecule renders the PF5OH−/H3O+/2H2O structure the most stable. On the contrary, the interaction of PCl5 and a single H2O molecule leads to the global minimum structure corresponding to the PCl3 O phosphoryl chloride with two HCl moieties attached. The lowest energy isomers resulting from the interaction of PCl5 with two, three, and four H2O molecules indicate the tendency of PCl3 O to subsequent replacement of the Cl ligands with OH groups resulting in formation of H3PO4 (with five surrounding HCl fragments) when the number of available H2O molecules is sufficient. The presence of the competitive isomers containing H3O+ fragments in the case of the PCl5 interacting with water molecules is also predicted and discussed.

A new 1:1 organic molecular adduct 2-aminopyrimidine: 3-nitrophthalic acid (APNP) was successfully synthesized and single crystals were grown by slow solvent evaporation technique at room temperature. The formation of the molecular adduct was confirmed by single crystal XRD analysis, which further reveals that the crystal belongs to the monoclinic crystal system with a centrosymmetric space group, P21/n. FT-IR spectrum was recorded to identify the functional groups present in the molecular adduct. The purity and stoichiometry of the molecular adduct were confirmed by CHN analysis. The presence of different kinds of protons and carbon atoms in the molecular adduct was confirmed by 1H and 13C NMR spectroscopic studies respectively. UV–Vis–NIR spectroscopic study was carried out to identify the transparency window of APNP crystal. The TG/DTA analyses were carried out simultaneously to establish the thermal stability of the adduct crystal. The computational studies including optimization of molecular geometry, natural bond orbital (NBO) and HOMO-LUMO analyses were performed by density functional theory at the B3LYP method at 6–21g basis set level using Gaussian 09 software. Hirshfeld surface analysis was carried out to know the influence of hydrogen bonding on the molecular properties of the adduct crystal. The third order nonlinear susceptibility of the APNP salt was established by the Z-Scan study. Moreover, the APNP crystal was subjected to antimicrobial activity against various bacterial and fungal species. In addition, the antioxidant activity of APNP adduct was evaluated by DPPH assay method.

A series of complexes ( 1 – 9 ) were synthesized by the reaction of halide bridged metal precursors with the three pyrazine thiourea ligands L1 , L2 and L3 to yield cationic as well as neutral complexes and characterized by various spectroscopic techniques. The cationic complexes are represented by the general formula [(arene)M(L)Cl] + , where L = L1 , L2 and L3 , arene = p -cymene, Cp* and M = Ru, Rh and Ir. All the cationic complexes were isolated with chloride/PF 6 as the counter ion. Reactions of rhodium and iridium dimers with L2 yielded neutral complexes 5 and 6 with the general formula [(arene)M(L)Cl 2 ]. The neutral complexes 5 and 6 were further reacted with NaN 3 to yield azido complexes 10 and 11 . These complexes were, in turn, reacted with acetylene derivatives to yield triazolo complexes 12 – 15 where only a few triazolo complexes of Cp* have been reported. X-ray diffraction studies revealed the complexes having a typical piano stool geometry around the metal center with the thiourea adducts binding to the metal center in a chelating (N, S) manner. Furthermore, the complexes 1 – 9, as well as the ligands were screened for potential anti-bacterial agents out of which complexes 3 and 5 exhibited anti-bacterial activity. Colorimetric sensing studies showed the agglomeration of the silver NPs upon addition of the ligands while the complexes were unresponsive.

Sialylglycoconjugates play biologically important roles in nature. The labile nature of the sialic acid residue in matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) analysis demands additional modification processes of the carboxylate group to avoid in-source or post-source decay. This paper reports a versatile and high-sensitivity matrix system, aniline derivative/2,5-dihydroxybenzoic acid/alkali metal salt, for MALDI-MS analysis of sialyloligosaccharides and sialylglycoconjugates without any modifications. A simple adduct ion signal was obtained from the femtomole range of the analytes tested with the new matrix system by MALDI-MS in reflectron mode. Besides, the laser power-dependent in-source decay and post-source decay pattern of the sialylated analytes with this matrix system allows a pseudo MS3 strategy for in-depth sequencing studies of the analytes. (C) 2019 The Author. Published by Elsevier B.V.

We explored the approach of using an analog of E−64, a well-known and hydrophilic cysteine cathepsin (CC) inhibitor, as a potent cysteine cathepsin-trapping agent (CCTA) to improve the tumor retention of low-molecular-weight, receptor-targeted radiopharmaceuticals. The synthesized hydrophilic CCTA-incorporated, NTSR1-targeted agents demonstrated a substantial increase in cellular retention upon uptake into the NTRS1-positive HT-29 human colon cancer cell line. Similarly, biodistribution studies using HT-29 xenograft mice revealed a significant and substantial increase in tumor retention for the CCTA-incorporated, NTSR1-targeted agent. The intracellular trapping mechanism of the CCTA-incorporated agents by macromolecular adduct formation was confirmed using multiple in vitro and in vivo techniques. Furthermore, utilization of the more hydrophilic CCTA greatly increased the hydrophilicity of the resulting NTSR1-targeted constructs leading to substantial decreases in most non-target tissues in contrast to our previously reported dipeptidyl acyloxymethyl ketone (AOMK) constructs. This work further confirms that the CCTA trapping approach can make significant improvements in the clinical potential of NTSR1-and other receptor-targeted radiopharmaceuticals.

A specific liquid chromatography–tandem mass spectrometry (LC-ESI-MS/MS) assay was developed and validated for simultaneous determination of two active metabolites of isosorbide dinitrate (ISDN), namely, isosorbide 2-mononitrate (IS 2-MN) and isosorbide 5-mononitrate (IS 5-MN). A simple protein precipitation extraction technique was employed using 13C6 isosorbide 5-mononitrate as the internal standard. The two isomers were separated on a chiral column and mass detection was carried out by electrospray ionization (ESI) in negative multiple reaction monitoring (MRM) mode (ESI -ve). As neutral organic nitrates do not ionize well in ESI ion source, adduct formation of IS 2-MN and IS 5-MN were evaluated. Acetate adduct ions of IS 2-MN and IS 5-MN were well ionized and fragmentable in the negative mode by liquid chromatography electrospray ionization/tandem mass spectrometry. These acetates adduct ions, of IS 2-MN and IS 5-MN were selected as parent mass for quantitation. The method was developed and validated in rat and human plasma with K2EDTA as an anticoagulant. This simultaneous quantitation method was shown to be linear over a working range of 25.0 ng/mL to 5050 ng/mL and 12.4 ng/mL to 2500 ng/mL for IS 2-MN (r2 > 0.99) and IS 5-MN (r2 > 0.99), respectively, in rat and human plasma. Sensitivity was determined as 25.0 ng/mL for IS 2-MN and 12.4 ng/mL for IS 5-MN in rat and human plasma. Inter- and intra-day accuracy and precision were within ±15% in both method validations. This validated method was subsequently applied to a pharmacokinetic (PK) study of ISDN in rat after oral administration.

Atmospheric pressure gas chromatography (APGC) coupled to quadrupole time-of-flight (QTOF) and electron ionization mass spectrometry together with commercial library search are two complementary techniques for non-target screening of volatile and semi-volatile compounds. Optimization was first conducted to achieve easier search of correspondent peaks between the two systems. Analytical strategy for the determination of volatile and semi-volatile compound with different identification confidence levels was then proposed and applied to food contact grade polypropylene (PP) samples. Identification was found to be much easier and less time-consuming especially when correspondent peak was found in the two systems with the help of library search, exact mass of precursor and fragment ions as well as Kovats Index (KI). The behavior of APGC-QTOF-MS was also further investigated. Apart from the M+. ion and the well-known adduct [M + H](+) others such as [M-3H + O](+), [M-3H + 2O](+) and [M-H + 3O](+) were also observed for n-alkanes. Besides, new reaction products were found, formed by diol compounds (1-Monostearoylglycerol, 2-Monostearoylglycerol and NX 8000K) and silanediol dimethyl, which would be a transformation product of the silicone base septum or the methyl 5% phenyl polysiloxane based column. These new compounds were only detected in APGC-MS-QTOF as EI-GC-MS was not enough sensitive for this purpose.

Hydroxyphenyl-pyranoanthocyanins are one of the pyranoanthocyanins found in red wines and some fruit juices. Since they have a fourth ring (pyran or ring D) which provides higher color intensity and exceptional stability toward pH variations in comparison to their anthocyanin precursors, these molecules are one of the most important candidates as natural colorants especially for low- and medium-acidic food and beverages. However, their isolation and characterization are difficult due to their very low concentration. In this study, we co-cultured recombinant E. coli strains to synthesize pyranoanthocyanins with improved titers and yields. To accomplish this task, firstly we engineered 4-vinylphenol and 4-vinylcatechol producer modules then we co-cultured each one of these strains with cyanidin-3-O-glucoside producer recombinant cells to obtain pyranocyanidin-3-O-glucoside-phenol (cyanidin-3-O-glucoside with vinylphenol adduct) and pyranocyanidin-3-O-glucoside-catechol (cyanidin-3-O-glucoside with vinylcatechol adduct). By optimizing the co-culture conditions, we were able to significantly increase final titers and yields, allowing our co-culture approach to easily outperform production of pyranoanthocyanins from red wine. Finally, we demonstrate that the produced pyranoanthocyanins are far more stable than the starting plant-produced cyanidin 3-O-glucoside.

A new method coupling molecularly imprinted polymer thin-films (MIP thin-films) with desorption electrospray ionization mass spectrometry (DESI-MS) has been developed for indirect analysis of thiophene compounds in water. MIP thin-films were prepared on non-porous glass slides using a simple drop-casting fabrication method. The resulting films were used for indirect quantitative analysis of thiophene compounds in water by sorbing thiophene oxidation products (sulfones) to MIP films, then interrogating the MIP surface by DESI-MS. Oxidation of thiophenes to sulfones in water was achieved by reaction with a mixture of H2O2/formic acid at 65 °C for 2 h. DESI source parameters were optimized, and the optimal spray solvent composition was found to be MeOH:H2O (95:5 v/v) containing 0.5 mM NaCl. Among all sulfones formed, the protonated ion and sodium adduct signals were observed only for dibenzothiophene sulfone. The method was applied to dibenzothiophene in seawater, yielding a limit of detection at 3 ng L−1 and relative standard deviations (RSDs) below 8.0%. DESI-MS response was linear (R2 = 0.9841) over the range studied 0.1–10 μg L−1. With limited sample handling and ease of sample processing, many samples can be processed simultaneously making the method suitable for high throughput of screening environmental waters for dibenzothiophene and has the potential for detection its sulfone-metabolite.

To clarify the thermal hazards of acrylic acid runaway polymerization, the amount of energy release and the products in each event of the polymerization sequence were investigated. The thermal hazard was analyzed using accelerating rate calorimetry (ARC), Karl-Fisher titration, and thermogravimetry-differential thermal analysis-mass spectrometry (TG-DTA-MS). The present study revealed that acrylic acid generates water, which increases the impact of tank destruction when the tank filling level is more than 15%. In addition, the Michael addition reaction of acrylic acid induces the monomer to polymerize due to its exotherm and produce Michael adducts, which generate larger amounts of gases and water than does the monomer. Therefore, the accumulation of Michael adducts increases the frequency of crack initiation in the tank, as well as the potential for tank destruction, due to the presence of monomer and water in the tank at a lower filling level than in the case of monomer alone. The present study determined that the accumulation of Michael adducts is the worst case scenario for accidents caused by acrylic acid.

A new polar phosphinoferrocene ligand, viz. 1’-(diphenylphosphino)ferrocene-1-phosphonic acid (H2L), was prepared by hydrolysis of the corresponding phosphonate ethyl ester. However, the compound is relatively unstable, gradually decomposing upon prolonged storage, ultimately affording phosphine oxide H2LO. When the phosphine moiety was protected (e.g., in phosphine oxide H2LO and adduct H2L·BH3), no decomposition was observed. An alternative approach to prepare more stable H2L surrogates by converting the phosphonic acid into ammonium salts (dabcoH)(HL) and [(OHCH2CH2)2NH2](HL) (dabco = 1,4-diazabicyclo[2.2.2]octane) resulted in no significant stabilisation. H2L reacted with [PdCl2(cod)] (cod = cycloocta-1,5-diene), producing the bis(phosphine) complex, trans-[PdCl2(H2L-κP)2]. When mixed with Pd(II)-acetylacetonate (acac) complexes with ortho-metallated auxiliary ligands, [(LCY)Pd(acac)] (LCY = 2-[(dimethylamino-κN)methyl]phenyl-κC1 and 2-[(methylthio-κS)methyl]phenyl-κC1), H2L gave rise to bis-chelate complexes of the [(LCY)Pd(HL-κ2O,P)] type. H2L, the ammonium salts featuring the HL− anion, and all Pd(II) complexes were structurally characterised by single-crystal X-ray diffraction analysis. Variations in phosphonate P-O bond lengths observed in the crystal structures were rationalised by DFT computations.

Mass spectrometric analysis of lignin for developing biomaterials requires advances of characterization techniques. Positive ion mass spectrometry of lignin model compounds using lithium has recently been explored as a viable alternative to current negative mode techniques. To date, little is known about the impact of lithium adduct ion formation on relative response factors of lignin and lignin decomposition products. In this contribution, we report estimates of lithium cation basicity for synthetic monolignols H, G and S using Cooks’ kinetic method on a linear quadrupole ion trap mass spectrometer. Optimized geometries and interaction energies have also been calculated by DFT methods to quantify the electrostatic cation coordination. Based on a combination of experimental and computational evidence, lithium appears to preferentially bind to the phenol and methoxy substituents on the aromatic ring of monolignols. The strength of this interaction increases with the number of methoxy substituents (S > G > H). This work serves as a basis of understanding for future work in developing lithium adducted lignin mass spectrometric analytical methods.

Furans bearing epoxy enolsilane units via a tether that incorporates a nitrogen heteroatom, undergo intramolecular (4 + 3) cycloadditions to generate bis-heteroatomic polycyclic adducts having piperidine moieties in their frameworks. The cycloadducts, ultimately derived from furfural, a renewal chemical feedstock, are obtained with up to 4:1 dr and with ee retained from the epoxide.

Capitalizing on the nucleophilic addition of hydrazine toward the central cyclobutenyl core and affinity of aldehydes to hydrazine group, two water-soluble squaraine dyes (SQOH and SQPY) were synthesized as sensitive colorimetric and fluorescent chemosensors for aldehydes. The color change from blue to colorless and back to blue these sensors underwent was readily observed, even by the naked eyes. The response was fast (less than 1 s) and the detection limit for formaldehyde as an example was about 60 μM. In contrast to the previous nucleophilic attack to squaraines and the other amine references studied, this work underwent a whole ON-OFF-ON sensing circle based on the characteristics of hydrazine. Meanwhile, the different photophysical properties of the two squaraines related to their different structures were also demonstrated. Importantly, a possible sensing mechanism is proposed suggesting these types of dyes hold great potential in the area of rapid, sensitive, and convenient detection of aldehydes.

The 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic polychlorinated dibenzo-p-dioxin. The OH –initiated oxidation of TCDD has been studied using the density functional, canonical transition state, and canonical Rice-Ramsperger-Kassel-Marcus theories. The kinetic data were corrected for quantum tunneling by the Wigner and Eckart models. All OH addition and hydrogen atom abstraction channels were thermodynamically exergonic. The kinetic and thermodynamic data analysis at the reliable level MPWB1K/MG3S//M06-2X/MG3S indicate that the addition of OH to the carbon atom adjacent to the oxygen atom in dioxin ring leads to the formation of predominant adduct. The calculated bimolecular rate constant for the formation of predominant adduct was ~5.97–6.75 × 10−13 cm3 molecule−1 s−1, its branching ratio was ~0.955, and the overall rate constant for the OH –initiated oxidation of TCDD was ~6.25–7.08 × 10−13 cm3 molecule−1 s−1. The atmospheric lifetime of TCDD determined by OH was ~8.17–9.26 days indicating the TCDD can be categorized as medium lifetime organic pollutant.

Conventional urea is lost due to its high water solubility and microbial transformations which results low agriculture productivity and environmental pollution. To solve these problems, rosin adduct-coated controlled release urea fertilizer (RA-CRUF) was prepared. Properties of rosin adduct with maleic anhydride were optimized during synthesis by varying the reaction temperature (120, 140 and 160 °C), reaction time (2, 4, 6 h) and coating repeats (3, 6, 9 cycles). Twenty different rosin adduct compositions were coated by spraying of rosin adduct on urea to prepare RA-CRUF. The best optimized response of urea release for RA-CRUF was 510.00 mg L−1 in water at optimized values of coating repeats (6.79 cycles), reaction time (4.71 h) and reaction temperature (137.39 °C). The Fourier Transformed Infrared Spectroscopy confirmed the reaction of rosin with maleic anhydride at wavenumber 1780 cm−1 and 1856 cm−1 correspond to carbonyl of cyclic anhydride group. The optical microscopy analysis of surface and cross view of RA-CRUF showed a high homogeneity of coating surface. The cumulative urea release was 41.76% and 47.23% for RA-CRUF compared 100% and 82.6% for conventional urea in clay loam texture and loam texture soils respectively. RA-CRUF effect on growth performance of maize plant showed healthy growth and increase in chlorophyll contents up to 51.11 mg g−1 (clay loam texture soil) and 87.55 mg g−1 (loam texture soil).

Multiphotochromic systems are of immense importance for promising applications nowadays, while it remains a formidable challenge to develop a compound containing various photoswitches with spectral complementarity. Herein, we describe a novel multiphotochromic system based on a first generation donor-acceptor Stenhouse adduct (DASA) and an aurone, in which all physicochemical properties of two photoswitches are preserved and four isomers are selectively reachable with three different wavelengths of light sources (365 nm, 430 nm, 585 nm) and a thermal relaxation process in an orthogonal manner. Multi-addressable behavior of the system could be beneficial for potential applications such as logic devices and photo-printing.