Hydroxyl Proton Research Articles

Получение новых замещённых имидазолоновых производных на основе 1-(2-оксо-2-фенилэтилиден) пирроло[3,2,1-ij]хинолин-2-онов

This work demonstrates the possibility of obtaining new biologically active molecules containing a privileged imidazolone fragment by the Brønsted acid-catalyzed reaction of 1,3-dimethylurea with 1-(2-oxo-2-phenylethylidene)pyrrolo[3,2,1-ij]quinolin-2-ones. The presence of an active oxoylidene system in ones makes it possible to introduce these compounds into cyclization reactions with various binucleophilic agents. The choice of such an N,N-binucleophile as 1,3-dimethylurea allowed us to obtain a number of new 1-(oxoimidazolyl)pyrrolo[3,2,1-ij]quinolin- 2-ones in a process carried out at reflux in acetonitrile and a tenfold excess of 1,3-dimethylurea via p-toluenesulfonic acid catalysis. It has been found that 1-(oxoimidazolyl)pyrrolo[3,2,1-ij]quinolin-2-ones in solution undergo keto-enol tautomerism. This is evidenced by the duplication of characteristic proton signals and the presence of the hydroxyl group proton signal in the region of 4.95 ppm in the 1H NMR spectrum of the obtained compounds. Also, based on the experimental data, we have presented a possible reaction mechanism. It is assumed that the reaction proceeds through consistent intermolecular addition of 1,3-dimethylurea to 1-phenacylidenepyrrolo[3,2,1-ij]quinolin-2-ones with intramolecular cyclization, followed by elimination of a water molecule.

Catalytic ozonation of atenolol by Mn-Ce@Al2O3 catalysts: Efficiency, mechanism and degradation pathways

The aim of this study is to investigate the degradation efficiency and mechanism of atenolol (ATL) by catalytic ozonation with Al2O3 supported manganese-cerium mixed oxides (Mn-Ce@Al2O3), prepared by the impregnation-calcination method. The Mn-Ce@Al2O3 with 0.2 wt% manganese and 0.2 wt% cerium exhibited superior catalytic performance, resulting in complete ATL degradation and 63% mineralization. Mn-Ce solid solution on the surface significantly increased the specific surface area (279.5 m2/g). High amount of Ce3+, Mn3+ and high density of surface-active oxygen were contained on the surface of the catalyst, which facilitates the formation of oxygen vacancies and promotes the electron transfer in the catalyst. Combined with the low charge transfer resistance, surface protonated hydroxyl group, which was the active site of 0.2Mn-Ce@Al2O3, was more likely to adsorb ozone and decompose it into reactive oxygen species. O2·− and •OH were found to be the dominant active radicals for ATL degradation and mineralization that followed first-order kinetics. 17 intermediates were identified and 3 main degradation pathways were summarized, in order to provide reference for the complete mineralization of ATL.

The regulation of electron distribution on Fe Lewis acidic sites within silicon skeleton and its contribution to Ketoprofen ozonation

Lewis acid site was vital center for activating O3 during catalytic ozonation process. Herein, we proposed a strategy to enhance the Lewis acid strength of Fe-MCM-48 (FeM) by fluorination. Fluorinated Fe-MCM-48 (FFeM) exhibited the better catalytic ozonation efficiency towards Ketoprofen (KET), a kind of nonsteroidal anti-inflammatory drug. 87.4 % TOC removal was obtained by F2.5Fe0.8M/O3 process, but only 27.5 % and 52.7 % were found by sole ozonation and Fe0.8M/O3 processes, respectively. Comparative characterizations, experiments and DFT calculations showed that fluorinated FFeM was regular sphere with three dimensional duct channel and large SBET. Doping of F reduced particle size, implanted electron withdrawing Si-F group and formed the electron poor center around Fe atom, which enhanced Lewis acid strength of FFeM. Protonated hydroxyl groups on Lewis acid sites were the main active sites for O3 activation. Greater amount of O3 were absorbed on the surface of FFeM and the greater O3 utilization rate, •OH and •O2– generation rates were obtained by FFeM/O3 process. Common anions such as Cl−, SO42− and NO3– and Humic acids (HA) had little effect on KET removal but inhibited TOC removal in FFeM/O3 process. •OH, •O2– and Fe(IV) = O oxidation were accounted for KET degradation. 16 kinds of intermediates generated from KET degradation and 4 pathways were deduced.

Selective incorporation of 5-hydroxytryptophan blocks long range electron transfer in oxalate decarboxylase.

Oxalate decarboxylase from Bacillus subtilis is a binuclear Mn-dependent acid stress response enzyme that converts the mono-anion of oxalic acid into formate and carbon dioxide in a redox neutral unimolecular disproportionation reaction. A π-stacked tryptophan dimer, W96 and W274, at the interface between two monomer subunits facilitates long-range electron transfer between the two Mn ions and plays an important role in the catalytic mechanism. Substitution of W96 with the unnatural amino acid 5-hydroxytryptophan leads to a persistent EPR signal which can be traced back to the neutral radical of 5-hydroxytryptophan with its hydroxyl proton removed. 5-Hydroxytryptophan acts as a hole sink preventing the formation of Mn(III) at the N-terminal active site and strongly suppresses enzymatic activity. The lower boundary of the standard reduction potential for the active site Mn(II)/Mn(III) couple can therefore be estimated as 740 mV against the normal hydrogen electrode at pH4, the pH of maximum catalytic efficiency. Our results support the catalytic importance of long-range electron transfer in oxalate decarboxylase while at the same time highlighting the utility of unnatural amino acid incorporation and specifically the use of 5-hydroxytryptophan as an energetic sink for hole hopping to probe electron transfer in redox proteins.

Theranostic Cancer Treatment Using Lentinan-Coated Selenium Nanoparticles and Label-Free CEST MRI.

Selenium nanoparticle (SeNP)-based nanotherapeutics have become an emerging cancer therapy, while effective drug delivery remains a technical hurdle. A theranostic approach, through which imaging companions are integrated with SeNPs, will allow image-guided drug delivery and, therefore, is highly desirable. Traditional methods require the chemical conjugation of imaging agents to the surface of nanoparticles, which may impede the later clinical translation. In this study, we developed a label-free strategy in which lentinan-functionalized SeNPs (LNT-SeNPs) are detected using MRI by the hydroxyl protons carried on LNT molecules. The in vitro phantom study showed that LNT and LNT-SeNPs have a strong CEST signal at 1.0 ppm apart from the water resonance, suggesting an in vivo detectability in the µM concentration range. Demonstrated on CT26 colon tumor cells, LNT-SeNPs exert a strong anticancer effect (IC50 = 4.8 μM), prominently attributed to the ability to generate intracellular reactive oxygen species. However, when testing in a mouse model of CT26 tumors, administration of LNT-SeNPs alone was found unable to deliver sufficient drugs to the tumor, leading to poor treatment responses. To improve the drug delivery, we co-injected LNT-SeNPs and TNF-α, a previously reported drug that could effectively damage the endothelial cells in the tumor vasculature, thereby increasing drug delivery to the tumor. Our results revealed a 75% increase in the intratumoral CEST MRI signal, indicating a markedly increased delivery efficiency of LNT-SeNPs when combined with TNF-α. The combination therapy also resulted in a significantly enhanced treatment outcome, as revealed by the tumor growth study. Taken together, our study demonstrates the first label-free, SeNP-based theranostic system, in which LNT was used for both functional surface coating and CEST MRI signal generating. Such a theranostic LNT-SeNP system is advantageous because it requires chemical labeling and, therefore, has high biocompatibility and low translatable barriers.

Bioassay Analysis and Molecular Docking Study Revealed the Potential Medicinal Activities of Active Compounds Polygonumins B, C and D from Polygonum minus (Persicaria minor).

Polygonumins B, C and D, derivative compounds of polygonumins A, were isolated from the stem of Polygonum minus. Based on NMR results, the structure of polygonumins derivatives is comprised of four phenylpropanoid units and a sucrose unit, with a similar structure to polygonumins A. However, the structural differences between polygonumins B (1), C (2) and D (3) can be distinguished based on the existence of methoxy, ethanoyl and hydroxyl groups and protons which bind to C-4, C-4′ and C-3″. Interestingly, these bioactive compounds showed various medicinal properties based on our investigation on antioxidant, anticholinesterase and anti-HIV-1 protease activities. The IC50 value of DPPH and ABTS (antioxidant activities) was in the following descending order: polygonumins B > polygonumins C > polygonumins A > polygonumins D. In addition, almost similar pattern of antioxidant activity was observed for anti-acetylcholinesterase activity based on its IC50 value in descending order: polygonumins B > polygonumins C > polygonumins D > polygonumins A. On the other hand, polygonumins C and D showed inhibition of HIV-1 protease activity more than the positive control, pepstatin A. Finally, molecular docking studies on AChE and BChE proteins were carried out in order to gain insight into the mode of interactions between these compounds and the active residues for both enzymes. These remarkable findings indicate that these compounds have potential to be developed as targeted drugs for Alzheimer’s disease or as anti-HIV drugs.

Enabling Characterisation of the NAD+ Biosynthesis Pathway via in vitro CEST MRI

AbstractBackgroundThe Chemical Exchange Saturation Transfer (CEST) MRI properties of six metabolites required for synthesis of coenzyme nicotinamide adenine dinucleotide (NAD+) and to evaluate the potential for clinical imaging of altered NAD+ regulation in neurodegenerative disordersMethodCEST images of metabolites in the NAD+ biosynthesis pathway were acquired at physiological temperature with high‐field MRI (9.4T) running a modified magnetisation transfer (MTR) prepared RARE sequence over a range of saturation powers and frequency ofsets, for pH values 5.5‐7.4. CEST data were fitted using spline interpolation, the exchange rate was calculated, and frequency specific MTR maps were generated using pixelwise analysis.ResultTryptophan, nicotinamide, nicotinic acid (NA), nicotinamide riboside (NR), nicotinamide mononucleotide (NMN) and NADH were evaluated. At pH 7.4, all molecules exhibited CEST contrast between 0.1 and 0.9 ppm, originating from the OH hydroxyl proton. NADH exhibited up to 15% CEST contrast in a B1 field of 2.4µT from its fast‐exchanging amine groups at 2 and 3 ppm, and showed a positive dependence of CEST efciency on pH. Tryptophan exhibited three independent peaks at 0.7, 2.6, and 5.4 ppm corresponding to pH 6.7, 5.5 and 7.4. NMN showed high CEST contrast at 0.7ppm originating from its phosphorous OH enabling higher CEST efciency due to enhanced charge delocalisation (Fig.1).ConclusionThis in vitro feasibility study demonstrates signal detection and characterization of NAD+ biosynthesis pathway precursor molecules over precise temperature, concentration and physiological pH ranges. All molecules exhibited a peak at 0.7 from the hydroxyl group with NMN showing highest CEST efficiency due to phosphate charge delocalisation. NADH showed a peak at 2 and 3ppm from amine group protons and a dependency on temperature and pH.

Crystal structure of a pre-chemistry viral RNA-dependent RNA polymerase suggests participation of two basic residues in catalysis.

The nucleic acid polymerase-catalyzed nucleotidyl transfer reaction associated with polymerase active site closure is a key step in the nucleotide addition cycle (NAC). Two proton transfer events can occur in such a nucleotidyl transfer: deprotonation of the priming nucleotide 3'-hydroxyl nucleophile and protonation of the pyrophosphate (PPi) leaving group. In viral RNA-dependent RNA polymerases (RdRPs), whether and how active site residues participate in this two-proton transfer reaction remained to be clarified. Here we report a 2.5 Å resolution crystal structure of enterovirus 71 (EV71) RdRP in a catalytically closed pre-chemistry conformation, with a proposed proton donor candidate K360 in close contact with the NTP γ-phosphate. Enzymology data reveal that K360 mutations not only reduce RdRP catalytic efficiency but also alter pH dependency profiles in both elongation and pre-elongation synthesis modes. Interestingly, mutations at R174, an RdRP-invariant residue in motif F, had similar effects with additional impact on the Michaelis constant of NTP (KM,NTP). However, direct participation in protonation was not evident for K360 or R174. Our data suggest that both K360 and R174 participate in nucleotidyl transfer, while their possible roles in acid-base or positional catalysis are discussed in comparison with other classes of nucleic acid polymerases.

The Effect of Temperature and Thermodynamic Parameters on the Ionization Constants of Some Imines Derived from Vanillin with substituted aniline

This work presents a method for the preparation of imine compounds including Schiff bases derived from vanillin with aniline, o-nitroaniline, o-tolidene and o-chloroaniline. Compounds' structures of the prepared compounds were confirmed by physical methods like melting point, infrared spectroscopy (IR), electronic spectroscopy (U.V), and nuclear magnetic resonance spectroscopy (NMR).
 The ionization constants of the imine nitrogen proton Ka1 and the phenol hydroxyl group proton Ka2 were determined using the spectrometric titration method at five temperatures including 293,298,303,308 and 313K in a buffer solution medium. The thermodynamic of ionization for imines confirm that ionization reactions in these imines are accompanied by an increase of parameters ∆Gº and ∆Hº. These mean that ionization reactions in these imines are non-spontaneous and endothermic respectively. ∆Sº values of ionization reactions estimated have a negative and a positive signs.

Engineered disorder in CO2 photocatalysis

Light harvesting, separation of charge carriers, and surface reactions are three fundamental steps that are essential for an efficient photocatalyst. Here we show that these steps in the TiO2 can be boosted simultaneously by disorder engineering. A solid-state reduction reaction between sodium and TiO2 forms a core-shell c-TiO2@a-TiO2-x(OH)y heterostructure, comprised of HO-Ti-[O]-Ti surface frustrated Lewis pairs (SFLPs) embedded in an amorphous shell surrounding a crystalline core, which enables a new genre of chemical reactivity. Specifically, these SFLPs heterolytically dissociate dihydrogen at room temperature to form charge-balancing protonated hydroxyl groups and hydrides at unsaturated titanium surface sites, which display high reactivity towards CO2 reduction. This crystalline-amorphous heterostructure also boosts light absorption, charge carrier separation and transfer to SFLPs, while prolonged carrier lifetimes and photothermal heat generation further enhance reactivity. The collective results of this study motivate a general approach for catalytically generating sustainable chemicals and fuels through engineered disorder in heterogeneous CO2 photocatalysts.

Stereo-Recognition of Hydrogen Bond and Its Implications for Lignin Biomimetic Synthesis.

The hydrogen bond (H-bond) is essential to stabilizing the three-dimensional biological structure such as protein, cellulose, and lignin, which are integral parts of animal and plant cells; thus, stereo-recognition of the H-bond is extremely attractive. Herein, a methodology combining the variable-temperature 1H NMR technique with the density functional theory was established to recognize the underlying H-bonding patterns in lignin diastereomers. This method successfully classified the intramolecular and intermolecular H-bonds with slope values varying between 50.2-201.5 and 221.9-655.4, respectively, from the natural logarithm of the hydroxyl proton chemical shift versus the inverse of the temperature plot. Moreover, this slope was found to be correlated with the interaction distance between the H-bond donor and acceptor. Finally, it was proposed that the stereo-preferential formation of the β-O-4 structure (erythro vs threo form) during lignin biomimetic synthesis was probably influenced by their intramolecular H-bonding patterns, thus making it easier to reach thermodynamic equilibrium.

Assessment of cellulose interactions with water by ssNMR: 1H->13C transfer kinetics revisited

To evaluate cellulose interactions with water, 1H->13C polarization transfer kinetics during Variable Contact Time CP-MAS NMR spectroscopy were studied and modelled using cellulose of different origins. The increase in the temporal resolution of the plot relating signal intensity to contact-time made it possible to compare different physical models for use in fitting the kinetic curve. These models involve combinations of variables, such as proton spin diffusions, that require a better understanding of their physicochemical and structural bases. To that end, hydrogen interactions were modulated by adding water, first by varying cellulose water content, second by exchanging hydroxyl protons with D2O, and last by varying the spinning rate.The results demonstrate that this approach makes it possible to probe interactions of polysaccharides with structural water, as well as to follow the evolution of the proton-proton interactions during hydration through spin diffusion times.

Dual-Peak Lorentzian CEST MRI for antiretroviral drug brain distribution.

Spatial-temporal biodistribution of antiretroviral drugs (ARVs) can now be achieved using MRI by utilizing chemical exchange saturation transfer (CEST) contrasts. However, the presence of biomolecules in tissue limits the specificity of current CEST methods. To overcome this limitation, a Lorentzian line-shape fitting algorithm was developed that simultaneously fits CEST peaks of ARV protons on its Z-spectrum. This algorithm was tested on the common first line ARV, lamivudine (3TC), that has two peaks resulting from amino (-NH2) and hydroxyl (-OH) protons in 3TC. The developed dual-peak Lorentzian function fitted these two peaks simultaneously, and used the ratio of -NH2 and -OH CEST contrasts as a constraint parameter to measure 3TC presence in brains of drug-treated mice. 3TC biodistribution calculated using the new algorithm was compared against actual drug levels measured using UPLC-MS/MS. In comparison to the method that employs the -NH2 CEST peak only, the dual-peak Lorentzian fitting algorithm showed stronger correlation with brain tissue 3TC levels, signifying estimation of actual drug levels. We concluded that 3TC levels can be extracted from confounding CEST effects of tissue biomolecules resulting in improved specificity for drug mapping. This algorithm can be expanded to measure a variety of ARVs using CEST MRI.

Adsorption behavior of rhamnolipid modified magnetic Co/Al layered double hydroxide for the removal of cationic and anionic dyes

In the present research, magnetic rhamnolipid-Co/Al layered double hydroxide (MR-LDH) was synthesized to uptake methylene blue (MB) and reactive orange 16 (RO16) from aqueous solution. The main parameters, including pH, adsorbent dosage, contact time, and initial analyte concentration, were optimized to achieve the best adsorption efficiency. Accordingly, the elimination of MB on MR-LDH is improved in the basic medium due to the electrostatic interactions between the negative charge of MR-LDH and the positive charge of MB dye. In contrast, the acidic medium (pH = 3) was favored for RO16 adsorption because of hydrogen bonding between the protonated form of azo dye and protonated hydroxyl groups at the surface of MR-LDH. The calculated maximum adsorption capacities for MB and RO16 were 54.01 and 53.04 mg/g at 313 K, respectively. The Langmuir model, which assumes monolayer adsorption on the adsorbent surface, provides the best explanation for the adsorption of both dyes (R2 = 0.9991 for MB and R2 = 0.9969 for RO16). Moreover, the pseudo-second-order kinetic model best described the adsorption process for MB (R2 = 0.9970) and RO16 (R2 = 0.9941). The proposed adsorbent maintains stable adsorption performance for four consecutive cycles. After each adsorption process, MR-LDH is easily separated by an external magnet. The findings show that MR-LDH was found to be an excellent adsorbent for the removal of both cationic and anionic organic dyes from aqueous solutions.

Proton Self-Enhanced Hydroxyl-Enriched Cerium Oxide for Effective Arsenic Extraction from Strongly Acidic Wastewater.

Acid recycling and arsenic recovery from strongly acidic wastewater are goals of the metallurgical industry to reduce carbon emissions. In this study, arsenic was recovered using a hydroxyl-enriched CeO2 adsorbent, and the adsorption mechanism in a strongly acidic solution was investigated. The adsorption capacities of 88.59 mg/g for As(III) and 126.211 mg/g for As(V) at pH 1.0 are the highest reported values to date. It is revealed that the hydroxyl groups on the CeO2 surface can buffer hydrogen ions, and the isoelectric point of the material can be reduced to pH 1.52. The binding energy of arsenic is -1.25 eV for the hydroxyl-enriched CeO2 and -2.24 eV for CeO2 without hydroxyl groups. Additionally, the protonated hydroxyl groups reduce the oxidation energy of As(III) and promote the adsorption of arsenic by forming new active sites in the strongly acidic solution. Nearly 98.11% of arsenic (initial concentration is 886.8 mg/L) is removed within 24 h without pH adjustment, indicating the feasibility of hydroxyl-enriched CeO2 for recovering arsenic and acid. This work investigated the adsorption and proton-enhanced oxidation mechanism of arsenic by hydroxyl-enriched CeO2 in strongly acidic wastewater.

Recovery of indium from sulfate solutions with D2EHPA in the presence of organic proton-donor additives

Di(2-ethylhexyl)phosphoric acid (D2EHPA, HR) is widely used for solvent extraction of indium from acidic leaching solutions, but indium stripping from the loaded organic phase is difficult because of the high affinity of indium for the extractant. Adding proton-donor additives (HA) to the D2EHPA solution is a way to achieve high stripping efficiency for indium. In this work, monocarboxylic acids, aliphatic alcohols, and phenol derivatives were used as additives. Nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy of the organic phases confirm the formation of intermolecular associates (H-complexes) between all additives and D2EHPA. In the case of alcohols and substituted phenols, the interaction of oxygen atoms of alcohols or phenols with the proton of the hydroxyl group of D2EHPA is predominant, while in the case of monocarboxylic acids, an interaction between the hydroxyl proton of the acid and the PO group of D2EHPA mainly occurs. Despite the high In distribution ratio with D2EHPA (100−1000), in all cases investigated the introduction of additives into the organic phase led to an antagonistic extraction effect, however it facilitated efficient In stripping from the loaded organic phase. This effect depends significantly on the type and structure of the additive. Indium extraction in the presence of additives decreases in the series 4-bromophenol >4-t-butylphenol > octanol, 2-ethylhexanol >4-nitrophenol >2-nitrophenol >2,6-di-t-butylphenol, octanoic acid > Versatic 10. Extraction systems containing D2EHPA and 2-ethylhexanol can be used to recover indium from various industrial solutions, in particular, from those derived from lead‑zinc production and from liquid crystal display panel wastes.

Regulating the excited state behaviors of 2-benzooxazol-2-yl-4,6-di-tert-butyl-phenol fluorophore by solvent polarity: A theoretical simulation

• The enhanced hydrogen bonding provides the impetus to promote the ESIPT reaction. • Photo-induced increased electronic densities around N atom plays vital roles in attracting hydroxyl proton. • Non-polar solvents are more favorable for the ESIPT behavior of BDTBP compound. In view of the unique luminescent characteristics, ESIPT materials have attracted lots of eyes. Given promising highly efficient green-emitting material, 2-benzooxazol-2-yl-4,6-di- tert -butyl-phenol (BDTBP) reveals important properties in designing Schiff base optical sensors. In this work, solvent dependent excited state behavior and ESIPT process of BDTBP has been explored theoretically. Analyses of chemical structural variations and infrared (IR) vibrational spectra in both S 0 and S 1 state, the enhanced intramolecular hydrogen bonding interactions could be clearly found that promotes ESIPT tendency. Particularly, BDTBP in nonpolar solvents with stronger hydrogen bond reveals the easier PT tendency. Paying attention to the changes of HOMO and LUMO orbitals, it could be found the charge transfer happens in the excited-state molecules, the reorganization of charge densities should be conducive to promoting the ESIPT process. Simulated potential energy curves indicated the ultrafast ESIPT reaction occurs for BDTBP fluorophore, which could be regulated and controlled via solvent polarity.

Assessment of cellular responses in three-dimensional cell cultures through chemical exchange saturation transfer and 1 H MRS.

Metabolic responses to physiological changes have been detected using chemical exchange saturation transfer (CEST) imaging in clinical settings. Similarly to other MRI techniques, the CEST technique was based originally on phantoms from buffer solutions and was then further developed through animal experiments. However, CEST imaging can capture certain dynamics of metabolism that solution phantoms cannot model. Cell culture phantoms can fill the gap between buffer phantoms and animal models. In this study, we used 1 H NMR and CEST in a B0 field of 9.4 T to investigate HEK293T cells from two-dimensional (2D) cultures, three-dimensional (3D) cultures, and 3D cultures seeded with cell spheroids. Two CEST dips were observed: the magnitude of the amine dip at 2.8 ppm increased during the incubation period, whereas the hydroxyl dip at 1.2 ppm remained approximately the same or modestly increased. We also observed a CEST dip at 2.8 ppm from the 2D culture responding dramatically to doxorubicin treatment. By cross-validating with pH values and the concentrations of amine and hydroxyl protons extracted through 1 H NMR, we observed that they did not correspond to an increase in the amine pool. We believe that the denaturation or degradation of proteins from the fetal bovine serum increased the size of the amine pool. Although 3D culture conditions can be further improved, our study suggests that 3D cultures have the potential to bridge studies of solution phantoms and those on animals.

Synthesis and Enzymatic Degradation of Sustainable Levoglucosenone-Derived Copolyesters with Renewable Citronellol Side Chains.

Recently, a renewable five-membered lactone containing citronellol (HBO-citro) was synthesized from levoglucosenone (LGO). A one-pot two-step pathway was then developed to produce a mixture of 5- and 6-membered Lactol-citro molecules (5ML and 6ML, respectively) from HBO-citro. Proton nuclear magnetic resonance (1H NMR) of a mixture of 5ML and 6ML at varying temperatures showed that the chemical shifts of the hydroxyls, as well as the 5ML:6ML ratio, are temperature-dependent. Indeed, a high temperature, such as 65 °C, led to an up-field shielding of the hydroxyl protons as well as a drop in the 5ML:6ML ratio. The monomers 5ML and 6ML were then engaged in polycondensation reactions involving diacyl chlorides. Renewable copolyesters with low glass transition temperatures (as low as −67 °C) and cross-linked citronellol chains were prepared. The polymers were then hydrolyzed using a commercial lipase from Thermomyces lanuginosus (Lipopan® 50 BG). A higher degradation rate was found for the polymers prepared using Lactol-citro molecules, compared to those obtained by the polycondensation reactions of diacyl chlorides with Triol-citro—a monomer recently obtained by the selective reduction of HBO-citro.

ESIPT-Active 8-Hydroxyquinoline-Based Fluorescence Sensor for Zn(II) Detection and Aggregation-Induced Emission of the Zn(II) Complex.

A D−π–A type quinoline derivative, 2-(((4-(1, 2, 2-triphenylvinyl)phenyl)imino)methyl)quinolin-8-ol (HL), was synthesized and structurally characterized. The five-membered ring formed by the O–H···N hydrogen bond in HL contributed to the excited-state intramolecular proton transfer (ESIPT) behavior of HL, which was further verified by theoretical computations. Upon coordination with Zn2+, the hydroxyl proton in HL was removed, resulting in the inhibition of ESIPT. In the meanwhile, the formed Zn2L4 complex displayed aggregation-induced emission (AIE) character in THF/H2O mixtures, which is conducive to the fluorescence enhancement in aqueous media. Structure analysis suggested that the origin of the AIE characteristic was attributed to restriction of intramolecular rotations along with the formation of J-aggregates. Based on ESIPT coupled with AIE, HL could recognize Zn(II) in aqueous media via an orange fluorescence turn-on mode. Benefitting from the AIE property, chemosensor HL was successfully applied to fabricate test strips for rapid sensing of Zn(II) ions.