Addition Of TFA Research Articles

Synergistic Electronic and Carbonyl Proximity Effects in Electrochemical Hydrogen Evolution Catalyzed by Tetrakis(ethoxycarbonyl)porphyrin Metal Complexes

Abstract Electrocatalytic properties of a series of tetrakis(ethoxycarbonyl)porphyrin (TECP) 3d-metal complexes, and the influence of ester groups on the hydrogen evolution reaction (HER), were investigated using trifluoroacetic acid in a 0.1 M [Bu4N]PF6 DMF solution. [Co(TECP)], [Ni(TECP)], and [Cu(TECP)] exhibited three redox couples, with reversibility decreasing at more negative potentials. The third reduction couple was predominantly ligand-centered. Upon addition of TFA, the second reduction waves became catalytic, increasing proportionally with TFA concentration, indicating that the molecular nature of the [M(TECP)] complexes plays a role in facilitating HER. Electrochemical and catalytic studies revealed that [Cu(TECP)] demonstrated the highest Faradaic efficiency (FE) of 98% and the lowest overpotential (0.7 V) while maintaining strong acid tolerance. [Co(TECP)] became effective at overpotentials exceeding 800 mV, suggesting the predominance of EECC pathway at more negative potential. The roles of the ester groups extended beyond a simple inductive effect, as confirmed by controlled potential electrolysis and spectroelectrochemical analyses. The superior HER activity of [Cu(TECP)] compared to [Cu(TPrP)] and [Cu(TPP)] highlights the contribution of the carbonyl groups to catalytic performance. This work underscores the importance of ester groups placement within the porphyrin framework and suggests that meso-ester groups can influence both the stability and catalytic performance, paving the way for further investigations

Synthesis and luminescent properties of a linear difluorene pyrazine (D-A-D) derivative as a selective indicator for a reversible acid-base vapour sensor

We have synthesized a structure in which pyrazine is the core structure and fluorene derivatives are attached to both sides. Photo physical investigations such as aprotic solvents (Hexane to DMF) were carried out. A redshift was revealed from non-polar aprotic solvents to polar aprotic solvents. The luminescence intensity was gradually decreased, which is incredibly more complex towards changes in the solvent polarization than their UV/Vis absorption spectra. The compound showed a redshift from 445 nm to 473 nm when slowly increasing the water fraction (fw) from 0 to 30 %. Also, rising water fraction (fw > 40–90 %) effectively attenuated the instantaneous emission intensity was observed. At the same time, the intensity of the emission peak was reduced due to the TICT effect on fluorene and pyrazine rings due to enhanced solvent polarity. In addition, optically reversible acidofluorochromic properties were performed experimentally in both solvent and solid phases. For the acidic substances TFA and HF, which contain fluorine, new redshift peaks from 425 nm and 503 nm were observed upon reaction with the PDF solution, and the emission intensity was extinguished by more than 90 % and 60 %, respectively. Upon addition of TFA up to 1500 equal, the PDF mixture suffered from 50 % lower energy absorption intensity. The 1H NMR spectrum confirmed the proposed mechanism (TFA/TEA, ON-OFF-ON). Therefore, the present work presents a novel approach to fabricating ON-OFF-ON active-pull pyrazine scaffolds that can be used in DSEgens, referred to as “ON-OFF-ON” fluorescent sensors, for multifunctional applications.

Highly emissive tridentate fluorophores based on bis-imidazo[1,2-α]pyridine for deep-blue photoluminescence with CIE y ≤ 0.08

Imidazo[1,2-α]pyridine-based multifunctional derivatives have been widely utilized in pharmaceuticals, chemical sensing, bioimaging, optoelectronics, and other fields. Through incorporation of different substituents at the C4 position of central pyridine ring, nine tridentate imidazo[1,2-α]pyridine derivatives 4a-i have been synthesized and fully characterized. The influence of substituents on the luminescence of 4a-i was systematically investigated by spectroscopic methods, which was in accordance with density functional theory calculations and electrochemical measurement. In CH2Cl2, all compounds exhibited strong near-UV to deep-blue emission and retained CIE y coordinates ≤0.08, with maximum emission band located at 378–450 nm and photoluminescence quantum yields in the range of 15%–94%. Meanwhile, compound 4f exhibited a positive acidochromism in CH2Cl2 upon addition of TFA, accompanied with the dual change of colorimetric and fluorometric determination, indicating its potential application for the development of pH sensor. Moreover, the high decomposition temperatures of 4a-i ranging from 289 °C to 450 °C indicated that these compounds showed good thermal stability. On the basis of their excellent photophysical and thermal properties, the electroluminescence performance of 4f were further evaluated with a maximum EQE of 3.14% and CIE coordinate (0.16, 0.08), which could be utilized as promising novel blue organic light-emitting material.

A white light emitting single halochromic hydrazine bridged bis(3-pyrrolyl BODIPY) fluorophore.

In search of white light emitting fluorophores, a hydrazine bridged Schiff base compound, bis(3-pyrrolyl BODIPY), was synthesized by condensing readily available α-formyl 3-pyrrolyl BODIPY with hydrazine hydrate in CH3OH under reflux for 5 h followed by recrystallization. Bis(3-pyrrolyl BODIPY) was thoroughly characterized by HR-MS, 1D and 2D NMR, and X-ray crystallography. The X-ray structure revealed that the 3-pyrrolyl BODIPY units in the dyad were arranged trans to each other with respect to the hydrazine moiety. Bis(3-pyrrolyl BODIPY) showed absorption bands in the region of 390-705 nm and exhibited multiple fluorescence bands in the region of 395-720 nm at different excitation wavelengths. The protonated derivative of bis(3-pyrrolyl BODIPY) generated by the addition of TFA to its CH2Cl2 solution showed significant changes in the optical properties and generated white fluorescence under UV light with specific emission bands observed in blue, green, and red regions, indicating that bis(3-pyrrolyl)BODIPY is a single white light emitting halochromic fluorophore under acidic conditions. DFT and TD-DFT studies justify the structural and electronic properties of the protonated derivative of bis(3-pyrrolyl BODIPY) exhibiting white light emission.

Synthesis and Studies of Di(p-Benzi)Decaphyrin and Di(9,10-Anthracenyl)Decaphyrin.

Two novel macrocycles, di(p-benzi)decaphyrin and di(9,10-anthracenyl)decaphyrin have been synthesized by condensing appropriate p-phenylene based pentapyrrane or 9,10-anthracenyl based pentapyrrane with pentafluorobenzaldehyde under acid catalyzed conditions. The pentapyrrane precursors were synthesized over sequence of steps starting with commercially available 1,4-dibromobenzene and 9,10-dibromoanthracene. The decaphyrin macrocycles were freely soluble in common organic solvents and characterized and studied by HR-MS, 1D and 2D NMR, absorption, cyclic voltammetry and computational techniques. The 1 H NMR spectra of both decaphyrins were almost similar with very few resonances, indicating their symmetrical nature in solution and the position of chemical shifts of various protons supports nonaromatic nature of decaphyrins. The DFT optimized structures revealed that both decaphyrins showed a doubly twisted figure of eight conformation and the p-phenylene rings in di(p-benzi)decaphyrin and anthracenyl rings in di(9,10-anthracenyl)decaphyrin did not participate in π-delocalization with rest of the respective decaphyrin macrocycle. Both decaphyrins showed sharp intense band in the region of 400-500 nm and a broad band in the region of 600-900 nm. The absorption bands of di(p-benzi)decaphyrin were significantly red shifted compared to di(9,10-anthracenyl)decaphyrin. The protonated derivatives of decaphyrins generated by addition of TFA to the toluene solution of decaphyrins showed distinct changes in colour and absorption spectral bands. The redox studies indicated that both decaphyrins are electron rich and undergo easier oxidations. The electrochemical and computational studies revealed that HOMO-LUMO energy gap was less in di(p-benzi)decaphyrin compared to di(9,10-anthracenyl)decaphyrin supporting the bathochromic shifts of absorption bands in di(p-benzi)decaphyrin. TD-DFT studies were in agreement with the experimental observations.

Y-shaped novel AIEE active push-pull quinoxaline derivatives displaying acidochromism and use towards white light emission by controlled protonation

A series of novel Y-shaped push-pull quinoxaline derivatives 2a-2f with quadrupolar and tripodal arrangement having quinoxaline as an electron acceptor (A) and biphenyl and phenyl as an electron donor (D), was designed, synthesized and characterized. Single crystal XRD studies depicted the twisted conformation for quadrupolar quinoxaline derivative 2a. All compounds displayed positive solvatochromism upon increasing solvent polarity from toluene to DMSO. Further, the aggregation studies confirmed the presence of aggregation induced emission enhancement (AIEE) characteristics. Quadrupolar derivatives 2a and 2f displayed nearly five-fold emission enhancement while tripodal derivatives 2b-2e displayed much lesser emission enhancement on aggregation in THF-water mixture. The photophysical studies were also explored in the presence of acid. Visual colour changes from colourless to light yellow or red under day light, and emission change from violet or indigo to green were observed in solution upon addition of TFA. The spectral and visible colour changes were reversed upon addition of TEA. A controlled protonation of tripodal derivative 2c in chloroform solution caused white photoluminescence and thus may have potential application in white light emitting diodes.

Multitasking with Chemical Fuel: Dissipative Formation of a Pseudorotaxane Rotor from Five Distinct Components.

A 3-fold completive self-sorted library of dynamic motifs was integrated into the design of the pseudorotaxane-based rotor [Zn(2·H+)(3)(4)]2+ operating at k298 = 15.4 kHz. The rotational motion in the five-component device is based on association/dissociation of the pyridyl head of the pseudorotaxane rotator arm between two zinc(II) porphyrin stations. Addition of TFA or 2-cyano-2-phenylpropanoic acid as a chemical fuel to a zinc release system and the loose rotor components 2-4 enabled the liberated zinc(II) ions and protons to act in unison, setting up the rotor through the formation of a heteroleptic zinc complex and a pseudorotaxane linkage. With chemical fuel, the dissipative system was reproducibly pulsed three times without a problem. Due to the double role of the fuel acid, two kinetically distinct processes played a role in both the out-of-equilibrium assembly and disassembly of the rotor, highlighting the complex issues in multitasking of chemical fuels.

Azulichlorins and Benzocarbachlorins Derived Therefrom.

Acid-catalyzed condensation of azulidipyrrane aldehydes with a dihydrodipyrrin carbaldehyde afforded the first examples of azulichlorins. These macrocyclic products were isolated in a monoprotonated form, and the free bases proved to be somewhat unstable. The monocations were strongly diatropic, and proton NMR spectroscopy showed the internal C-H at ca. -2 ppm. Addition of TFA gave the related dications, but these exhibited significantly reduced aromatic ring currents. Reaction of an azulichlorin with tert-butyl hydroperoxide and KOH in dichloromethane/methanol gave a benzocarbachlorin and two related aldehydes. The UV-vis spectrum for the benzocarbachlorin showed a split Soret band at 414 and 430 nm, together with a strong chlorin-like absorption at 684 nm. The proton NMR spectrum indicated that the carbachlorin is strongly aromatic and the internal C-H was observed at -4.64 ppm. Addition of TFA afforded a C-protonated dication with a significantly increased diatropic ring current. The proton NMR spectrum, NICS calculations, and AICD plots indicated that the system favors a 22π electron delocalization pathway that runs through the fused benzo unit. Addition of TFA to the benzocarbachlorin aldehydes primarily led to the formation of monocations, and the generation of C-protonated dications was no longer favored due to the presence of electron-withdrawing formyl moieties.

One‐Pot Synthesis and Photophysical Studies of Styryl‐Based Benzo[f]pyrazolo[3,4‐b]quinoline and Indeno[2,1‐b]pyrazolo[4,3‐e]pyridines

A new family of extended π‐conjugated dihydrobenzopyrazoloquinoline (DBPQ) and dihydroindenopyrazolopyridine (DIPP) molecules were synthesized, and their photophysical and electrochemical properties were studied. The DBPQ derivatives showed significantly higher molar absorption coefficients, and their absorption and emission wavelengths were red‐shifted with respect to those of the corresponding DIPP derivatives in chloroform solution. Dyes with no substitution and methoxy, nitro, and fluoro‐substituted derivatives showed poor dependence on solvent polarity. At the same time, DBPQ and DIPP derivatives with dimethylamino groups exhibited strong solvatochromism in the emission spectra. Due to the presence of a vinyl link with a cylindrical π‐cloud on the donor (dimethylamino group) molecule, they showed efficient positive solvatochromism with high quantum yields on increasing solvent polarity from non‐polar to polar solvents. Aggregation‐induced emission (AIE) properties were also investigated. AIE studies show that the emission of DBPQ and DIPP derivatives in the presence of THF/H2O mixture increased due to aggregation. However, DBPQ and DIPP derivatives were still strongly emissive in the solid state. Dimethylamino substituted derivatives exhibited acidochromism, which was caused by the addition of TFA and pTsA leading to prominent red‐shifts in the emission spectra owing to the protonation at the pyridine segment.

Synthesis of Selenium and Tellurium Core-Modified Azuliporphyrinogens and Benziporphyrinogens and Corresponding Carbaporphyrinoids.

The synthesis of selenium and tellurium core-modified carbaporphyrinogens was carried out by the reaction of functional selenophene/tellurophene diols with azulene or a benzitripyrrane in the presence of acid. The products were obtained in moderate yields and were characterized by using 1H and 13C NMR, UV-vis, FT-IR, CV, and HRMS spectroscopic techniques. Further, oxidation of the obtained core-modified carbaporphyrinogens in the presence of DDQ in CHCl3 afforded the corresponding carbaporphyrins in good yields. Benziporphyrins showed no indication of a ring current or macrocyclic aromaticity as confirmed by using proton NMR spectroscopy, but the addition of TFA gave rise to the formation of weakly diatropic dications.

Using Bispyrene Fluorescence Probe for Determining the Multiple States of Organogel

AbstractA bispyrene fluorescence probe with the cavitand linkage (compound 1) was synthesized, which was proved to be a versatile platform due to the ability of adopting two spatially well‐defined conformations: a closed vase and an expanded kite. vase‐1 was switched to kite‐1 upon addition of TFA or cooling, whereas kite‐1 was isomerized to vase‐1 in the presence of NEt3 or through heating. The interconversion in this molecular switch was tightly associated with the change of fluorescence as we found that changing the temperature and pH of the system‐ a bispyrene compound 1 and gelator 2 led to the sol ‐ gel transformation and reversible intramolecular excimer emission. Briefly, the results show that the fluorescence decreases in the gelation phase and is enhanced in the solution due to variations in temperature and pH. we thus concluded that 1 could be a useful fluorescence probe to determine the multiple states of organogel.

Synthesis of Nocistatin C-terminal and it's Amide Derivatives as an Opioid Peptide.

A new biological active hexapeptide of C-terminal of nocistatin, contains Glu-Gln-Lys-Gln-Leu-Gln sequence was synthesized according to solid phase peptide synthesis on the surface of 2-chloro tritylchloride resin and using fmoc-protected amino acids in the presence of TBTU (O-(Benzotriazol-1-yl)-N,N,N',N'-tetramethyl uranium tetrafluoroborate) as a coupling reagent. Then, amidation of the C-terminus of peptides was carried out using NH4Cl and alkyl ammonium chloride (RNH3Cl) in the presence of TBTU and a tertiary amine (DIPEA) as the base at room temperature in good to high yields. Cleavage of the desired peptides from the surface of the resin after the addition of TFA (1%) provided the protected peptides. All of the products were purified using preparative HPLC and structures were assigned according to MALDI-mass spectrometry data.

Proteomic characterization of the acid-insoluble fraction of whole saliva from preterm human newborns

The acid-insoluble salivary proteome obtained by addition of TFA to whole human saliva from adults, preterm and at-term newborns has been analysed by 2-DE in order to evidence differences among the three groups, and integrate data previously obtained on the acid-soluble fraction. 2-DE spots differentially expressed among the three groups were submitted to in-gel tryptic digestion and the peptide mixtures analysed by high resolution HPLC–ESI–MS/MS. By this strategy, we identified 3 over-expressed proteins in at-term newborns with respect to preterm newborns and adults (BPI fold-containing family A member 1, annexin A1, and keratin type 1 cytoskeletal 13), and several over-expressed proteins in adults (fatty acid-binding protein, S100A6, S100A7, S100A9, prolactin-inducible protein, Ig kappa chain, cystatin SN, cystatin S/SA and α-amylase 1). Four spots, already detected but not characterized by other authors in human saliva 2-DE, were attributed to different protein species of S100A9 (long-type and long-type monophosphorylated, short-type and short-type monophosphorylated) by MS/MS analysis of tryptic peptides and sequential staining of 2-DE gels with Pro-Q Diamond, for specific detection of phosphoproteins, and total protein SYPRO Ruby stain. SignificanceDifferential protein expression analysis of the acid insoluble fraction of saliva from preterm, at-term newborns and adults has been performed in this study by coupling 2-DE analysis and high-resolution tandem mass spectrometry in order to complete the information previously obtained by top-down LC–MS only on the acid-soluble proteome. Several proteins identified in the acid insoluble fraction of both preterm newborn and adult saliva are not of glandular origin, being only prolactin-inducible protein, salivary cystatins, α-amylase and polymeric immunoglobulin receptor exclusive of salivary glands.Three proteins resulted increased in at-term newborns with respect to preterm newborns and adults: BPI fold-containing family A member 1, two proteoforms of annexin A1 and keratin type 1 cytoskeletal 13, while several proteins were significantly increased in adults.

Multi-addressable fluorescence switch based on a new photochromic diarylethene with two rhodamine B units

A novel diarylethene derivative with two rhodamine B units has been synthesized successfully. The diarylethene could be effectively controlled by the stimulation of light, proton, and metal ions. The fluorescence intensity of the diarylethene was enhanced upon addition of TFA, Al3+, Cr3+, and Fe3+, which was assigned to the blocked FRET process by the protonation of the rhodamine or complexation with Al3+, Cr3+, and Fe3+. The results indicated that the diarylethene could act as a multi-addressable fluorescence switch with the light, proton, and metal ions stimulus. Moreover, two logic circuits were constructed with the fluorescence intensity as the output signal responding to the light and chemical species as the inputs.

ChemInform Abstract: Palladium‐Catalyzed Direct C—H Arylation of 3‐Aryl‐2H‐benzo[1,2,4]thiadiazine 1,1‐Dioxides: An Efficient Strategy to the Synthesis of Benzothiadiazine‐1,1‐dioxide Derivatives.

A new palladium-catalyzed benzothiadiazine-1,1-dioxide direct arylation of C(sp2)–H bonds is described. 3-Aryl-2H-benzo[1,2,4]thiadiazine 1,1-dioxides react with various aryl iodides to give the corresponding mono-arylation products 3-(biphenyl-2-yl)-2H-benzo[1,2,4]thiadiazine 1,1-dioxides with high reactivity and regioselectivity in the presence of AgOAc. Remarkedly, the addition of TFA is crucial to improve the arylation yield.

A fluorescent probe for Cd2+ based on a diarylethene with pyridinepiperazine-linked hydroxyquinoline group

A new diarylethene containing a pyridinepiperazine-linked hydroxyquinoline group was synthesized. Its multi-controllable switching behaviors induced by light and chemical stimuli were investigated. The diarylethene could be used as a fluorescent probe for the detection of Cd2+ with high selectivity. When triggered by Cd2+, enhanced fluorescence intensity accompanied with color change from light blue to bright blue was observed. In addition, the diarylethene exhibited notable fluorescence enhancement upon the addition of TFA into the solution. Moreover, its fluorescence behaviors in response to light and Cd2+ were applied for the construction of a molecular logic circuit with four inputs and one output.

A multi-state fluorescence switch based on a new photochromic diarylethene with a di-(ethyl-1,8-naphthalimidyl)amine unit

Abstract A novel asymmetrical diarylethene with a di-(ethyl-1,8-naphthalimidyl)amine unit was synthesized. Its fluorescence can be effectively modulated by UV–vis, TFA/TEA, and Sn 2+ . The fluorescence intensity of the title compound was enhanced upon addition of TFA or Sn 2+ , which was ascribed to the blocked PET process by protonation of the tertiary amine or complexation with Sn 2+ . As a result, the diarylethene can serve as a fluorescence chemosensor for highly selective recognition of Sn 2+ in THF. Moreover, a logic circuit was designed with one optical output responding to three inputs.

A semi-automated LC–MS/MS method for the determination of LCI699, a steroid 11β-hydroxylase inhibitor, in human plasma

A novel liquid chromatographic method with tandem mass spectrometric detection (LC-MS/MS) for the determination of LCI699 was developed and validated with dynamic ranges of 0.0500-50.0 ng/mL and 1.00-1,000 ng/mL using 0.0500 mL and 0.100mL, respectively, of human plasma. LCI699 and the internal standard, [M+6]LCI699, were extracted from fortified human plasma via protein precipitation. After transfer or dilution of the supernatant followed by solvent evaporation and/or reconstitution, the extract was injected onto the LC-MS/MS system. Optimal chromatographic separation was achieved on an ACE C18 (50 mm × 4.6mm, 3 μm) column with 30% aqueous methanol (containing 0.5% acetic acid and 0.05% TFA) as the mobile phase run in isocratic at a flow rate of 1.0 mL/min. The total analysis cycle time is approximately 3.5 min per injection. The addition of an ion-pair reagent, TFA (0.05%, v/v), to the mobile phases significantly improved the chromatographic retention and resolution of the analyte on silica based reversed-phase column. Although addition of TFA to the mobile phase suppresses the ESI signals of the analyte due to its ion-pairing characteristics in the gas phase of MS source, this negative impact was effectively alleviated by adding 0.5% acetic acid to the mobile phase. The current method was validated for sensitivity, selectivity, linearity, reproducibility, stability and recovery. For the low curve range (0.0500-50.0 ng/mL), the accuracy and precision for the LLOQs (0.0500 ng/mL) were -13.0 to 2.0% bias and 3.4-19.2% CV, respectively. For other QC samples (0.100, 6.00, 20.0 and 40.0 ng/mL), the precision ranged from 1.2 to 9.0% and from 3.8 to 8.8% CV, respectively, in the intra-day and inter-day evaluations. The accuracy ranged from -11.3 to 8.0% and -7.2 to 1.6% bias, respectively, in the intra-day and inter-day batches. For the high curve range (1.00-1,000 ng/mL), the accuracy and precision for the LLOQs (1.00 ng/mL) were 1.0-15.0% bias and 7.4-9.2% CV, respectively. For the other QC samples (3.00, 20.0, 200 and 750 ng/mL), the precision ranged from 0.8 to 7.0% and from 1.9 to 5.2% CV, respectively, in the intra-day and inter-day evaluations. The accuracy ranged from -2.5 to 4.0% and 0.7-1.0% bias, respectively, in the intra-day and inter-day batches. Additional assessments of incurred sample stability (ISS) and incurred sample reanalysis (ISR) were conducted to demonstrate the ruggedness and robustness of the assay method. The absence of adverse matrix effect and carryover was also demonstrated. The validated method was successfully used to support rapid turnaround human pharmacokinetic studies.

An improved palladium(II)-catalyzed method for the synthesis of aryl ketones from aryl carboxylic acids and organonitriles

A palladium(II)-catalyzed decarboxylative protocol for the synthesis of aryl ketones has been developed. The addition of TFA was shown to improve the reaction yield and employing THF as solvent enabled the use of solid nitriles and in only a small excess. Using this method, five different benzoic acids reacted with a wide range of nitriles to produce 29 diverse (hetero)aryl ketone derivatives in up to 94% yield.

The One Hour Yeast Proteome

We describe the comprehensive analysis of the yeast proteome in just over one hour of optimized analysis. We achieve this expedited proteome characterization with improved sample preparation, chromatographic separations, and by using a new Orbitrap hybrid mass spectrometer equipped with a mass filter, a collision cell, a high-field Orbitrap analyzer, and, finally, a dual cell linear ion trap analyzer (Q-OT-qIT, Orbitrap Fusion). This system offers high MS2 acquisition speed of 20 Hz and detects up to 19 peptide sequences within a single second of operation. Over a 1.3 h chromatographic method, the Q-OT-qIT hybrid collected an average of 13,447 MS1 and 80,460 MS2 scans (per run) to produce 43,400 (x̄) peptide spectral matches and 34,255 (x̄) peptides with unique amino acid sequences (1% false discovery rate (FDR)). On average, each one hour analysis achieved detection of 3,977 proteins (1% FDR). We conclude that further improvements in mass spectrometer scan rate could render comprehensive analysis of the human proteome within a few hours.