Free-base corroles: determination of deprotonation constants in non-aqueous media

2007 ◽  
Vol 11 (04) ◽  
pp. 269-276 ◽  
Author(s):  
Jing Shen ◽  
Zhongping Ou ◽  
Jianguo Shao ◽  
Michał Gałęzowski ◽  
Daniel T. Gryko ◽  
...  
Keyword(s):  
Equilibrium Constants ◽  
Aqueous Media ◽  
Free Base ◽  
Organic Base ◽  
Experimental Conditions ◽  
Spectral Changes ◽  
Base Analysis ◽  
Uv Visible ◽  
The Given

A series of free-base corroles with different electron-donating or electron-withdrawing substituents were reacted with piperidine, 4-aminopyridine, 2-methylimidazole, 2-aminopyridine or pyridine in PhCN and the UV-visible spectral changes monitored during conversion of ( Cor ) H 3 to [( Cor ) H 2]- as a function of the concentration and strength of the added organic base. Analysis of the UV-visible spectral changes as a function of the added base concentration enabled calculation of equilibrium constants ( logK ) for deprotonation of each corrole under the given experimental conditions. Relationships are examined between the experimentally measured logK values and previously published spectroscopic and structural properties of the compounds.

Solvent and acidity effects on the UV-visible spectra and protonation-deprotonation of free-base octaethylcorrole

2008 ◽  
Vol 12 (01) ◽  
pp. 1-10 ◽  
Author(s):  
Zhongping Ou ◽  
Hongxia Sun ◽  
Weihua Zhu ◽  
Zulin Da ◽  
Karl M. Kadish
Keyword(s):  
Equilibrium Constants ◽  
Visible Spectrum ◽  
Soret Band ◽  
Free Base ◽  
Tetrabutylammonium Hydroxide ◽  
Experimental Conditions ◽  
Visible Spectra ◽  
Meso Position ◽  
Uv Visible ◽  
Strong Acids

The UV-visible spectrum of free-base octaethylcorrole, (OECor) H 3, was recorded in thirteen different nonaqueous solvents as well as in a mixed acetonitrile/acid solvent containing one of seven different acids. Spectra were also measured in seven different solutions of neat concentrated acid and in CH 3 CN containing piperidine or tetrabutylammonium hydroxide as an added base. The overall data was analyzed as a function of solvent acidity or basicity parameters and the number of protons on the central nitrogens of the macrocycle, the predominant form of the corrole in these solutions being respresented as (OECor)H 3, [ (OECor)H 4]+, [ (OECor)H 2]− or [ (OECor)H ]2− where OECor = trianion of octaethylcorrole. The mono-protonated corrole, [ (OECor)H 4]+, is formed in concentrated acetic acid or in CH 3 CN containing 0.10 M trifluoroacetic acid, H 2 SO 4, HCl , H 3 PO 4 or HClO 4. The mono-deprotonated corrole, [ (OECor)H 2]−, is generated in piperidine while doubly deprotonated [ (OECor)H ]2− exists in solutions of tetrabutylammonium hydroxide. An addition of protons to the macrocycle of [ (OECor)H 4]+ also occurs in the presence of concentrated strong acids and this results in a loss of the characteristic Soret band of the corrole leading presumably to [ (OECor)H 5]2+ where the second proton has been added to a meso-position of the macrocycle. The UV-visible spectral changes upon formation of [ (OECor)H 4]+, [ (OECor)H 2]− or [ (OECor)H ]2− in CH 3 CN were monitored during a titration with the relevent acid or base and equilibrium constants for protonation or deprotonation of (OECor)H 3 were determined using standard equations. The measured logK values are compared to protonation and deprotonation constants obtained for two related corroles and two related porphyrins under the same experimental conditions.

N-confusedmeso-tetraaryl-substituted free-base porphyrins: determination of protonation and deprotonation constants in nonaqueous media

2015 ◽  
Vol 19 (01-03) ◽  
pp. 251-260 ◽  
Author(s):  
Zhongping Ou ◽  
Xueyan Chen ◽  
Lina Ye ◽  
Songlin Xue ◽  
Yuanyuan Fang ◽  
...  
Keyword(s):  
Tautomeric Form ◽  
Equilibrium Constants ◽  
Single Step ◽  
Free Base ◽  
Nonaqueous Media ◽  
Tautomeric Forms ◽  
Visible Spectra ◽  
Phenyl Rings ◽  
Uv Visible

The protonation and deprotonation reactions for a series N-confused meso-tetraaryl-substituted free-base porphyrins containing electron-donating or electron-withdrawing substituents was monitored in CHCl3and DMF by UV-visible spectroscopy during titrations with trifluoroacetic acid or tetra-n-butylammonium hydroxide. The spectroscopic data was also used to calculate equilibrium constants for these reactions. The examined compounds are represented as (XPh)4NCPH2, where "NCP" represents the N-confused porphyrin π-conjugated macrocycle and X is a CH3O , CH3, H or Cl para-substituent on the four meso-phenyl rings (Ph) of the compound. The porphyrins can exist in two tautomeric forms depending upon the solvent and each tautomer undergoes two stepwise protonation reactions leading to formation of the mono- and bis-protonated porphyrins, [(XPh)4NCPH3]+and [(XPh)4NCPH4]2+. A single step deprotonation is observed for the same compounds in DMF and the product is assigned as [(XPh)4NCPH]-. Comparisons are made between UV-visible spectra of the protonated, neutral and deprotonated forms of the porphyrin and the effect of the porphyrin ring substituents and tautomeric form of the neutral porphyrin on the UV-visible spectra and protonation constants is discussed along with data from DFT calculations.

scholarly journals Naphthyridine derived colorimetric and fluorescent turn off sensors for Ni2+ in aqueous media

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Abida Ashraf ◽  
Muhammad Islam ◽  
Muhammad Khalid ◽  
Anthony P. Davis ◽  
Muhammad Tayyeb Ahsan ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Color Change ◽  
Aqueous Media ◽  
Field Measurements ◽  
Spectral Changes ◽  
Energy Gaps ◽  
Td Dft ◽  
Distinct Color ◽  
Uv Visible ◽  
Metal Charge Transfer

AbstractHighly selective and sensitive 2,7-naphthyridine based colorimetric and fluorescence “Turn Off” chemosensors (L1-L4) for detection of Ni2+ in aqueous media are reported. The receptors (L1-L4) showed a distinct color change from yellow to red by addition of Ni2+ with spectral changes in bands at 535–550 nm. The changes are reversible and pH independent. The detection limits for Ni2+ by (L1-L4) are in the range of 0.2–0.5 µM by UV–Visible data and 0.040–0.47 µM by fluorescence data, which is lower than the permissible value of Ni2+ (1.2 µM) in drinking water defined by EPA. The binding stoichiometries of L1-L4 for Ni2+ were found to be 2:1 through Job’s plot and ESI–MS analysis. Moreover the receptors can be used to quantify Ni2+ in real water samples. Formation of test strips by the dip-stick method increases the practical applicability of the Ni2+ test for “in-the-field” measurements. DFT calculations and AIM analyses supported the experimentally determined 2:1 stoichiometries of complexation. TD-DFT calculations were performed which showed slightly decreased FMO energy gaps due to ligand–metal charge transfer (LMCT).

scholarly journals DEVELOPMENT AND VALIDATION OF UV-VISIBLE SPECTROPHOTOMETRIC METHOD FOR DETERMINATION OF DULOXETINE

2019 ◽  
pp. 27-31
Author(s):  
LIPSA SAMAL ◽  
AMARESH PRUSTY
Keyword(s):  
Spectrophotometric Method ◽  
Spectroscopic Method ◽  
Solvent System ◽  
Spectrophotometric Analysis ◽  
Thiophene Derivative ◽  
Experimental Conditions ◽  
Relative Standard ◽  
Uv Visible ◽  
Development And Validation

Objective: The aim of the present work was to develop and validate a simple UV spectroscopic method for the determination of duloxetine, which is a thiophene derivative and a selective neurotransmitter reuptake inhibitor for serotonin, norepinephrine, and to lesser degree dopamine. Methods: The UV Spectrophotometric analysis was performed using Shimadzu UV-1800 and Shimadzu UV-1700 spectrophotometer by using solvent system acetonitrile and water in the ratio of 8:2. Detection was performed at a wavelength of 290 nm. Method validation was carried out according to ICH Q2R1 guidelines by taking the parameters linearity, accuracy, precision, ruggedness, and robustness, LOD and LOQ. Results: The UV Spectrophotometric method was found linear in the range of 10-50 μg/ml. The method was rugged and robust with % relative standard deviation less than 2. The extraction recoveries were found to be higher than 99% in all experimental conditions. Conclusion: Based upon the performance characteristics, the proposed method was found accurate, precise and rapid and suitable for the determination of Duloxetine for routine analysis.

Examination of the potential of copper during its dissolution in sodium hydroxide

1981 ◽  
Vol 46 (12) ◽  
pp. 3057-3062 ◽  
Author(s):  
Petr Sušinka ◽  
Milica Miadoková
Keyword(s):  
Quantitative Determination ◽  
Sodium Hydroxide ◽  
Oxygen Electrode ◽  
Quantitative Relation ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Crystallographic Planes ◽  
The Given ◽  
Spontaneous Reaction

Parallel to kinetic measurements, the potential of copper was monitored on the (100), (110), and (111) crystallographic planes during its spontaneous reaction in sodium hydroxide in oxygen atmosphere. A quantitative relation was obtained for the potential in dependence on the experimental conditions, indicating that unless a passivating layer of copper(II) oxide is formed on the surface, the metal does not act as an oxygen electrode. The potential change in the given medium was found to depend only on the amount of copper(I) oxide formed, obeying the relation E = (RT/nF) ln (mCu2O) + K; use was made of this relation for a quantitative determination of the growth of the copper(I) oxide layer.

Charge-Transfer Complexes Between Iodine and Substituted Thioureas: Determination of Thermodynamic and Spectroscopic Properties

1996 ◽  
Vol 51 (1-2) ◽  
pp. 116-122 ◽  
Author(s):  
Cornelia Fooken ◽  
Wolfram Baumann
Keyword(s):  
Equilibrium Constants ◽  
Spectroscopic Properties ◽  
Critical Discussion ◽  
Charge Transfer Complexes ◽  
Published Data ◽  
Visible Spectroscopy ◽  
Dichloromethane Solution ◽  
Uv Visible ◽  
Iodine Complexes

Abstract 15 iodine complexes with substituted thioureas were investigated in dichloromethane solution by UV-visible spectroscopy, and their equilibrium constants, reaction enthalpies and molar absorption coefficients were determined. The influence of the substituents on the properties of the charge-trans-fer complexes is examined. A critical discussion of previously published data is given, where comparable data are available.

The Identification Analysis for Macro Distributions Curves of Functionally Graded Materials Properties Based on Materials Components

2011 ◽  
Vol 228-229 ◽  
pp. 50-54
Author(s):  
Chao Feng Ge
Keyword(s):  
Functionally Graded Materials ◽  
Functionally Graded ◽  
Experimental Conditions ◽  
Graded Materials ◽  
Materials Properties ◽  
Dynamic Analyses ◽  
Identification Technique ◽  
Identification Analysis ◽  
The Given

There are much complex internal microstructures of functionally graded materials, and the mechanical parameters of functionally graded materials structures varied with the space coordinates. Therefore, it is generally difficult to measure point by point macro distributions curves of functionally graded materials properties based on available experimental conditions. The prerequisite for various analyses of the functionally graded materials structures is the determination of macro distributions curves of materials properties parameters. In practice, only the spatial distributions of different material components can be controlled in the course of materials production. Therefore, the functionally graded distributions curves need inversing and identifying by the materials components. In the present paper, the inversion and identification technique was put forward based on the positive static and dynamic analyses by the microelement method, which was applied to do the scale-span analyses for macro responses of functionally graded materials structures based on the given materials components distributions in production.

Synthesis, spectral and electrochemical characterization of non-aggregating α-substituted vanadium(IV)-oxo phthalocyanines

2005 ◽  
Vol 09 (05) ◽  
pp. 352-360 ◽  
Author(s):  
Zhou Jiang ◽  
Zhongping Ou ◽  
Naisheng Chen ◽  
Jundong Wang ◽  
Jinling Huang ◽  
...  
Keyword(s):  
Electronic Absorption Spectra ◽  
Polar Solvents ◽  
Experimental Conditions ◽  
Electrode Processes ◽  
Good Solubility ◽  
Diffusion Controlled ◽  
Uv Visible ◽  
The Given ◽  
Homo Lumo

Two α-substituted vanadium-oxo phthalocyanines, [( OC 6 H 3(t- Bu )2)4Pc] VO and [( OC 8 H 17)4Pc] VO , where OC 6 H 3(t- Bu )2 is 2,4-di-tert-butylphenoxy and OC 8 H 17 is 2,2,4-tri-methyl-3-pentoxy, were synthesized and characterized by elemental analysis, mass spectrometry, UV-visible, IR, ESR spectroscopy and electrochemistry. Both complexes have good solubility and do not aggregate in polar or non-polar solvents. Three reductions and two oxidations can be observed in DMF containing 0.2 M TBAP. A HOMO-LUMO gap of ~1.4 V is seen for both complexes. The first two one-electron reductions and first oxidation are reversible diffusion controlled electrode processes under the given experimental conditions. The effects of solvent and phthalocyanine macrocycle substituents on the Q bands of the electronic absorption spectra are discussed.

Synthesis, structural characterization and protonation/deprotonation of hydroxyl-substituted free-base tetraphenylporphyrins in nonaqueous media

2013 ◽  
Vol 17 (10) ◽  
pp. 941-953 ◽  
Author(s):  
Guifen Lu ◽  
Xiufeng Zhang ◽  
Xu Cai ◽  
Yuanyuan Fang ◽  
Min Zhu ◽  
...  
Keyword(s):  
Equilibrium Constants ◽  
Phenyl Group ◽  
Single Step ◽  
Hydroxyl Groups ◽  
Free Base ◽  
Nonaqueous Media ◽  
Vis Spectroscopy ◽  
Before And After ◽  
Phenyl Rings ◽  
Uv Visible

A series of hydroxyl-substituted free-base tetraphenylporphyrins was synthesized and characterized by UV-vis spectroscopy, 1 H NMR and mass spectrometry. The porphyrins are represented as (HOPh) n(t BuPh )4-n PH 2, where Ph presents a phenyl group, HO and t Bu are substituents on the para-positions of the phenyl rings of the macrocycle, n = 0–4 and P represents the dianion of tetraphenylporphyrin. The UV-visible properties of each porphyrin were examined in dichloromethane (DCM), N,N′-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) before and after addition of trifluoroacetic acid (TFA) or sodium hydroxide (NaOH) to solution. Equilibrium constants for protonation ( log βn) and deprotonation [Formula: see text] of each compound were determined using standard equations. The protonations occur in a single step involving a simultaneous two proton addition at the porphyrin central nitrogens. The phenolic protons on (HOPh) n(t BuPh )4-n PH 2 are easier to deprotonate than the core nitrogen protons of the porphyrins and this reaction occurs in a single step involving the simultaneous loss of 1–4 protons on the hydroxyl groups followed by a loss of two protons from the central nitrogens. The effect of HO substituents on UV-visible spectra and the magnitude of the protonation/deprotonation constants ( log βn and [Formula: see text]) are discussed. Two of the porphyrins, (t BuPh )4 PH 2 and trans- (HOPh) 2(t BuPh )2 PH 2, are also characterized by a single-crystal X-ray analysis.

scholarly journals A Fast and Validated High Throughput Bar Adsorptive Microextraction (HT-BAµE) Method for the Determination of Ketamine and Norketamine in Urine Samples

Molecules ◽  
2020 ◽  
Vol 25 (6) ◽  
pp. 1438 ◽  
Author(s):  
Samir M. Ahmad ◽  
Mariana N. Oliveira ◽  
Nuno R. Neng ◽  
J.M.F. Nogueira
Keyword(s):  
High Throughput ◽  
Aqueous Media ◽  
Cost Effective ◽  
Urine Samples ◽  
Gas Chromatography Mass Spectrometry ◽  
Selected Ion Monitoring ◽  
Large Volume Injection ◽  
Experimental Conditions ◽  
Assay Time

We developed, optimized and validated a fast analytical cycle using high throughput bar adsorptive microextraction and microliquid desorption (HT-BAμE-μLD) for the extraction and desorption of ketamine and norketamine in up to 100 urine samples simultaneously, resulting in an assay time of only 0.45 min/sample. The identification and quantification were carried out using large volume injection-gas chromatography-mass spectrometry operating in the selected ion monitoring mode (LVI-GC-MS(SIM)). Several parameters that could influencing HT-BAµE were assayed and optimized in order to maximize the recovery yields of ketamine and norketamine from aqueous media. These included sorbent selectivity, desorption solvent and time, as well as shaking rate, microextraction time, matrix pH, ionic strength and polarity. Under optimized experimental conditions, suitable sensitivity (1.0 μg L−1), accuracy (85.5–112.1%), precision (≤15%) and recovery yields (84.9–105.0%) were achieved. Compared to existing methods, the herein described analytical cycle is much faster, environmentally friendly and cost-effective for the quantification of ketamine and norketamine in urine samples. To our knowledge, this is the first work that employs a high throughput based microextraction approach for the simultaneous extraction and subsequent desorption of ketamine and norketamine in up to 100 urine samples simultaneously.

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