Molar Ratio Method Research Articles

Spectrophotometric Study and Determination of Ibuprofen and Lornoxicam Drugs via Their Reaction with Copper (II) Reagent and Their Biological Activities

The reactions of Ibuprofen (IBU) and Lornoxicam (LOR) drugs with copper tetramine and copper sulphate reagents respectively were studied spectrophotometrically at optimum conditions of, reactant concentration, temperature, time, λmax and pH. Applying of molar ratio method (MRM) on the Ibuprofen and Lornoxicam copper ion-pairs, indicated (1:1) stoichiometric ratio. In addition, validity of Beer's Law was carried out at 265 and 260 nm, for Ibuprofen and Lornoxicam products, respectively. Results of analysis were statistically validated. The linearity ranged from 2.063 to 103.14 and 3.72 to 74.36 μg ml-1 of recovery values 99.95 to 100.40 and 99.98 to 100.00 %, for IBU and LOR respectively. The low values of standard deviation (SD = 0.009 to 0.533 and 0.059 to 0.844) and relative standard deviation (RSD = 0.037 to 0.577 and 0.063 to 0.635 %) refer to the accuracy and precision of the proposed method for spectrophotometric micro-determination of these drugs in pure and in their pharmaceutical formulations in comparison with official methods. The robustness and procedure validation were assayed in intra and inter days. The solid ion-pairs of these drugs with copper have been separated and identified by elemental analyses and FT-IR spectroscopic tool and they were found to be biologically active toward some kinds of Tribolium confusum common insect species in flour mills and treated areas and their adults. These ion-pairs were found to be more biologically active than their drugs.

A simple and effective method for determination of the antithyroid drug carbimazole using ruthenium trichloride

An accurate, precise, and simple spectrophotometric method is proposed for the determination of the antithyroid drug carbimazole using ruthenium(III) chloride. This method is based on the formation at room temperature of a stable yellow-colored complex with λ$_{max}$ 370 nm. The method has a Beer's law range of 7.81 to 1.95 $\times $ 10$^{2}$ $\mu $g mL$^{-1}$, molar absorptivity coefficient $\varepsilon =$ 1.519 $\times $ 10$^{3}$ L mol$^{-1}$ cm$^{-1}$, and correlation coefficient of 0.997. The metal:ligand (M:L) ratio of the complex was confirmed by the mole ratio and Job's method of continuous variation, suggesting a 1:2 stoichiometry. The formed carbimazole:Ru(III) complex was confirmed by spectral studies, including Fourier transform infrared, nuclear magnetic resonance, electron spin resonance, magnetic susceptibility, thermal analysis, and powder--X-ray diffraction. Our method could be adopted for routine analysis of carbimazole, due to its ease, affordability, and effectiveness.

Synthesis, Characterization, Antimicrobial and Theoretical Studies of V(IV),Fe(III),Co(II),Ni(II), Cu(II), and Zn(II)Complexes with Bidentate (NN) Donar Azo Dye Ligand

The new 4-[(7-chloro-2,1,3-benzoxadiazole)azo]-4,5-diphenyl imidazole (L) have been synthesized and characterized by micro elemental and thermal analyses as well as 1H.NMR, FT-IR, and UV-Vis spectroscopic techniques. (L) acts as a ligand coordinating with some metal ionsV(IV), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II). Structures of the new compounds were characterized by elemental and thermal analyses as well as FT-IR and UV-Vis Spectra. The magnetic properties and electrical conductivities of metal complexes were also determined. Study of the nature of the complexes formed in ethanol following the mole ratio method.. The work also include a theoretical treatment of the formed complexes in the gas phase, this was done using the (hyperchem-8) program for the molecular mechanics and semi-empirical calculations. The heat of formation (?Hf?), binding energy (?Eb)and total energy (?ET) for ligand and their metal complexes were calculated by (PM3) method at 298 K.The electrostatic potential of the ligand (L) was calculated to investigate the reactive sites of the molecules. PM3 were used to evaluate the vibrational and electronic spectra for the ligand (L) and their metal complexes then comparing with the experimental values. The antibacterial activity for the (L)and its metal complexes were studied against two types of pathogenic bacteria Pseudonomous aerugionosa as gram negative and Bacillus subtilis as gram positive. Furthermore, the antifungal activity against two fungi Candida albicans, and Aspergillus flavus was studied for (L) and its metal complexes.

Synthesis, Spectral and Dyeing Performance Studies of 4-(2-Aminmo-5-nitro-phenylazo)-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one Complexes with Some Metal Ions

The ligand 4-(2-aminmo-5-nitro-phenylazo)-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one derived from 4-aminoantipyrine and 4-nitroaniline was synthesized. The synthesized ligand was characterized by 1HNMR, FT-IR, UV-Vis spectra and (C.H.N) analysis. Complexes of (YIII and LaIII ) with the ligand were prepared in aqueous ethanol with a 1:2 M:L ratio and at optimum pH. The prepared complexes were characterized by using flame atomic absorption, FT-IR, UV-Vis spectra,(C.H.N) analysis and conductivity measurement. The stoichiometry of complexes was studied by the mole ratio and job methods. A concentration range (1×10-4 - 3×10-4 M) obeyed Beer's law, the complex solutions show high values of molar absorption. On the basis of physicochemical data octahedral geometries were attributed for the complexes. All prepared compounds exhibited good antibacterial activity, the ligand and their complexes were application to cotton fabric and study of the detergent fastness

Study the Molar Ratio of the Reaction between Thalassemia s Drug (Deferoxamine) with Iron Over loud

Iron-Deferoxamine complex have been synthesized in vitro by the reaction of deferoxamine (which are use as therapeutic agent for removing iron overload from the bodies of thalassemia patients) with Fe(II) salt in aqueous medium. The geometry of the prepared complex as well as the mode of bonding were determined through FTIR, UV-Vis, mass spectral studies, metal content, and molar conductance. These studies revealed octahedral geometry for the complex with the general formula [FeII (DEF)]Cl2. Complex formation via molar ratio method and variation continuous method in aqueous solution have been also investigated and results were consistent to those found in the solid complexes with a ratio of (M:L) as (1 : 1). Conditional formation constant could also be calculated for [FeII (DEF)]Cl2 as 2.0 × 103. The effect of time on the formation of Iron – Deferoxamine complex has been also studied. This study showed that each 1×10-3M of deferoxamine needs 2.5 – 3 hrs to remove 1×10-3M of Iron (II) by formation coordination complex.

Calix[4]arene based 1,3,4-oxadiazole as a fluorescent chemosensor for copper(II) ion detection

A new calix[4]arene derivative in 1,3-alternate conformation bearing four fluorescent 1,3,4-oxadiazole units was synthesized as a fluorescent chemosensor. This chemosensor displayed a highly selective recognition of Cu2+ among various metal ions by the fluorescence quenching. The binding between the chemosensor and Cu2+ showed 1:2 stoichiometry which was investigated by means of mole ratio method.

Estimation of diet in extinct raccoon dog species by the molar ratio method

AbstractEstimation of the dietary habits of extinct species using morphological traits has been attempted in numerous studies; however, previous methods have encountered several difficulties, such as requiring specialized equipment. In this study, we describe an easy quantitative method for estimating the dietary habits, and apply it to extinct raccoon dogs (Nyctereutes) species (Carnivora, Mammalia). The method is based on the lower molar ratios (M2/M1 size) that reflect the species diet (carnivorous and omnivorous tendencies) in Canidae. Among the species statistically compared, Nyctereutes sinensis showed a lower M2/M1 score similar to that of Nyctereutes procyonoides albus (Hokkaido, Japan), whereas Nyctereutes tingi had a higher M2/M1 score similar to that of Nyctereutes procyonoides viverrinus (Honshu and Kyushu, Japan). These scores suggest that the diets of N. sinensis and N. tingi were similar to those of N. p. albus (relatively carnivorous) and N. p. viverrinus (relatively omnivorous), respectively. Other extinct raccoon dogs also showed varied M2/M1 score, suggesting dietary difference. These results suggest that raccoon dogs underwent dietary transitions or exhibited dietary plasticity during evolution, while their range of diets might have remained the same as those of different populations of extant species Nyctereutes procyonoides.

DEVELOPMENT OF EXTRACTIVE SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF IRON (III) WITH SCHIFF BASE 2-[(2-HYDROXYPHENYLIMINO) METHYL]-4-NITROPHENOL

Objective: A simple spectrophotometric method has been developed for the determination of Iron (III) by using Schiff base 2-[(2-hydroxyphenylimino) methyl]-4-nitrophenol [HPIMNP].Methods: HPIMNP extracts Fe (III) quantitatively (99.95%) into chloroform from an aqueous solution of pH range 4.0-6.0.Results: The chloroform extracts show maximum absorption at 510 nm (λ max). Beer’s Law is obeyed over the Fe (III) concentration range of 0.5 to 20.0 µg/ml. The Molar absorptivity and Sandell’s sensitivity for Fe–HPIMNP system is 5000 L mol ˉ1 cmˉ1 and 0.011 µg cmˉ2respectively. The composition of extracted species is found to be 1: 3 [Fe-HPIMNP] by Job’s continuous variation and Mole-ratio method. Interference by various ions has been studied.Conclusion: The proposed method is rapid, sensitive, reproducible and accurate and it has been satisfactory applied for the determination of Iron in Pharmaceutical Samples.

Encapsulation of anticancer drug copper bis(8-hydroxyquinoline) in hydroxyapatite for pH-sensitive targeted delivery and slow release

There is a conspicuous progress in increasing anticancer drug delivery through the utilization of nanoparticles (NPs) as drug delivery agents. Hydroxyapatite (HA) gives improved clinical effectiveness of drugs by reducing systemic toxicity and broadening the spectrum of drug delivery since it is biocompatible and it can be targeted towards tumor cells. Herein, investigation of the potential of enhancing controlled drug release of the template model drug, copper bis-(8-hydroxyquinoline), by encapsulating it in hollow hydroxyapatite nano-carriers, is presented. Hydroxyapatite nanoparticles are synthesized by following four different routes to optimize its efficacy of drug loading. Copper bis-(8-hydroxyquinoline) is encapsulated by Method (a) which was effected by stirring the model drug and porous HA NPs in colloidal solution and Method (b) which was done during synthesis of hydroxyapatite nanoparticles in a solution of the model drug. In synthesizing nanoporous HA NPs, calcium carbonate is used as a template to create voids in HA. In each method, Ca/P ratio was ensured to be kept at 1.67:1. Appealing results are reported for the encapsulated product which was prepared by Method (a2). Method (a) was done at three different molar ratios of PO43−:CO32– and best result was obtained for that utilized 2.003:1 molar ratio (Method (a2).). It produced 98.67% of encapsulation efficiency and 2.9522mg/g of drug loading capacity. Release kinetics was studied at a range of pH values; the lower the pH of the medium the higher is the drug release. For instance, when considering the product which exhibited high encapsulation efficiency and high drug loading capacity, at pH3.5 during the first 8h it elicited about 13% of release, at pH5.0 about 8% release while at pH6.0 it was just 2.5%. During the 24-hour span, pH3.5 exhibited about 23.8%, at pH5.0 approximately 9% with an increasing trend of release and at pH6.0 showed a value just above 2.5%. As such, acidity of the cancerous cells can be made use to increase the drug slow-release kinetics at the vicinity of the cancer cells.

Spectrophotometric Study of Complex Formation Between Curcumin and Cr(III) Ion: A Case of Heavily Overlapping Absorption Peaks

The complex formation between curcumin and Cr(III) in dimethyl sulfoxide (DMSO) was studied by the spectrophotometric method using the overlapping correction technique and compared with the result from the voltammetric technique. All samples were prepared in DMSO, protected from light, and all measurements were made at 25.0 ± 0.1 °C. The stoichiometry of the Cr(III)–curcumin complex was obtained from the mole ratio and continuous variation methods. Due to extensive overlap between absorption of the new complex and unreacted curcumin, the true absorption of the complex could not be obtained directly and further analysis was not possible. To avoid the high expense of purchasing commercial software, a new spreadsheet method using a common software readily available in most desktop PCs or notebooks was used to calculate the residual amount of unreacted curcumin, which was then subtracted numerically from the overlapping absorption to obtain the absorbance of the anticipated complex. Subsequently, the stoichiometry of the Cr(III)–curcumin complex was determined as 1:1 from both methods, hence the complex formation constant (K) of this compound could be calculated. The value of K obtained from the equilibrium concentrations and the Benesi–Hildebrand plot are (3.20 ± 0.05) × 104 and (3.00 ± 0.05) × 104, respectively, and closely agree with the value of (3.50 ± 0.05) × 104 from Nernst’s equation.

Fluorescent Sensing of both Fe(III) and pH Based on 4-Phenyl-2-(2-Pyridyl)Thiazole and Construction of OR Logic Function.

In the presented paper we investigated a 2-pyridylthiazole derivative, 4-phenyl-2-(2-pyridyl)thiazole (2-PTP), as the molecular fluorescent switches. It was firstly found that 2-PTP could perform a "turn-on" fluorescent sensing for Fe(III) with selectivity and reversibility. A 2:1 stoichiometry between 2-PTP and Fe(III) was determined according to the molar ratio method. The binding constant was evaluated as (1.90±0.05)×10(5) (L/mol)(2). The detection limit was found as 2.2×10(-7)M (S/N=3). Secondly, 2-PTP also exhibited a pH-dependent dual-emission. The pK a(2-PTP-H(+)/2-PTP) value was then estimated as 2.0. To explain the identical emission at 479nm of both the Fe(III) coordinated form and the protonated form of the ligand, we proposed a "locked" conformation. Finally, combining the two external stimuli as inputs, an OR logic gate was constructed using the fluorescent emission at 479nm as the output channel.

Synthesis, characterization and analytical study of tellurated Schiff base of bis[2-(3-nitrobenzylideneamino)-5-nitrophenyl]telluride and its complexation reactions with Mn(II), Co(II) and Ni(II) ions

Reaction of 2-amino-5-nitrophenylmercuric chloride with 3-nitro benzaldehyde gave 2-(3-nitrobenzylideneamino)-5-nitrophenylmercuric chloride (1). Reaction of the mercurated Schiff bases 1 with tellurium tetrabromide in 2:1 mole ratio gave the tellurated Schiff bases, bis [2-(3-nitrobenzylidineamino)-5-nitrophenyl] tellurium dibromide (2). Reduction of compound 2 by hydrazine hydrate gave the corresponding telluride, bis [2-(3-nitro benzylideneamino)-5-nitrophenyl]telluride (3). Complexation reactions of equilibrium mole ratios compound 3 with MnCl 2 .4H 2 O, CoCl 2 .6H 2 O and NiCl 2 .6H 2 O gave the corresponding complexes, i.e compounds 4-6, respectively. All the prepared compounds were characterized by elemental analysis, conductivity measurements and 1 H and 13 C NMR, FT-IR and UV-visible spectroscopic data. These data suggested that the compound 3 coordinate with metal ions as tridentate ligand. The molar conductivity study indicated compounds 1-3 are neutral and behave as non-electrolytes in DMSO solvent at room temperature while compounds 4-6 behave as 1:1 electrolytes in the same conditions. The molar ratio method was used to determine metal-ligand ratio, which was found as 1:1, metal: ligand. The thermal analysis of compounds 2 and 3 were also investigated and discussed.

Development of a reliable analytical method for the precise extractive spectrophotometric determination of osmium(VIII) with 2-nitrobenzaldehydethiocarbohydrazone: Analysis of alloys and real sample

The proposed method demonstrates that the osmium(VIII) forms complex with 2-NBATCH from 0.8molL−1 HCl at room temperature. The complex formed was extracted in 10mL of chloroform with a 5min equilibration time. The absorbance of the red colored complex was measured at 440nm against the reagent blank. The Beer's law was obeyed in the range of 5–25μgmL−1, the optimum concentration range was 10–20μgmL−1 of osmium(VIII) as evaluated by Ringbom's plot. Molar absorptivity and Sandell's sensitivity of osmium(VIII)-2NBATCH complex in chloroform is 8.94×103Lmol−1cm−1 and 0.021μgcm−2, respectively. The composition of osmium(VIII)-2NBATCH complex was 1:2 investigated from Job's method of continuous variation, Mole ratio method and slope ratio method. The interference of diverse ions was studied and masking agents were used wherever necessary. The present method was successfully applied for determination of osmium(VIII) from binary, ternary and synthetic mixtures corresponding to alloys and real samples. The validity of the method was confirmed by finding the relative standard deviation for five determinations which was 0.29%.

Spectrophotometric study of the interaction of methylene blue with poly(styrene-co-sodium styrene sulfonate)

The interaction of the cationic phenothiazine dye, the Methylene Blue (MB) with poly-(sodium styrene sulfonate) f –co-(styrene) 1-f , (PSSNa f ), has been investigated by spectrophotometric method. The polyelectrolyte induced metachromasy resulting in a blue shift of the absorption maxima of the dye, in agreement with the formation of dye H-aggregates. The stability of the PSSNa-MB complexes was studied as a function of polyelectrolyte chain length, polyelectrolyte electrostatic charge density f , polyelectrolyte concentration, NaCl salt addition, tetrahydrofurane (THF) addition and THF treatment. The stoichiometry of PSSNa-MB complex evaluated by the molar ratio method was found 4:1 for the fully charged PSSNa f = 1. Reversal of metachromasy was observed upon salt and THF addition, while THF treatment does not affect the complex and allows recovering the initial complex. Finally, thermodynamic parameters of the interaction between the polyelectrolyte and the dye at different temperatures, namely free energy DG, the enthalpy DH and the entropy DS have been evaluated to determine the binding constant and as a consequence the stability of the complex. The metachromasy effect was found to be more high as the chemical charge f increases and reaches its maximum value f = 1, when operating at optimal conditions. So, the PSSNa f = 1-MB complex is the most stable in comparison to the others based on lower charge density PSSNa f .

Preparation, Characterization and Antibacterial Studies of New 2-(naphthalene-2-yl)-2-(naphthalene-2ylamino) Acetonitrile Ligand with Some Metal Ions

In the present work, the synthesized of a series of metal ions complexes of [Cr(III), Fe(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II)] from new bidentate 2-(naphthalene-2-yl)-2-(naphthalene-2ylamino) acetonitrile ligand (L) which prepared from 2-naphthaldehyde and naphthalene-2-amine in the presence of KCN and alcoholic medium. These compounds were characterized by using several techniques FT-IR, UV-Visible spectrophotometer, magnetic susceptibility, thermal gravimetric analysis (TGA), elemental analysis, molar conductivity, 1H-NMR, as well as atomic absorption. From the spectral studies, an octahedral monomer structure was proposed for all complexes. The nature of the complexes formed in ethanolic solution has been studied following the molar ratio method and the result recorded [1:2] [M:L] ratio. Some complexes were found to be non-electrolyte and others were found to be weak electrolyte in ethanol. Biological activities of the free ligand and its metal complexes have been tested against a number of microorganisms in order to assess their antimicrobial properties.

Selective sensing of submicromolar iron(III) with 3,3′,5,5′-tetramethylbenzidine as a chromogenic probe

The development of highly selective and sensitive method for iron(III) detection is of great importance both from human health as well as environmental point of view. We herein reported a simple, selective and sensitive colorimetric method for the detection of Fe(III) at submicromolar level with 3,3,′5,5′-tetramethylbenzidine (TMB) as a chromogenic probe. It was observed that Fe(III) could directly oxidize TMB to form a blue solution without adding any extra oxidants. The reaction has a stoichiometric ratio of 1:1 (Fe(III)/TMB) as determined by a molar ratio method. The resultant color change can be perceived by the naked eye or monitored the absorbance change at 652nm. The method allowed the measurement of Fe(III) in the range 1.0×10−7–1.5×10−4molL−1 with a detection limit of 5.5×10−8molL−1. The relative standard deviation was 0.9% for eleven replicate measurements of 2.5×10−5molL−1 Fe(III) solution. The chemistry showed high selectivity for Fe(III) in contrast to other common cation ions. The practically of the method was evaluated by the determination of Fe in milk samples; good consistency was obtained between the results of this method and atomic absorption spectrophotometry as indicated by statistical analysis.

Extractive Spectrophotometric Determination of Platinum in Cisplatin Injection, Alloys and Catalysts Assisted by 2-nitrobenzaldehydethiocarbohydrazone

A simple, rapid, selective and sensitive spectrophotometric method for the determination of platinum(IV) was developed, based on the color reaction between platinum(IV) and 2nitrobenzaldehydethiocarbohydrazone (2-NBATCH) in the pH range 6.4-7.8. The red colored species have been developed after heating the reaction mixture in boiling water bath for 5 min and it was extracted into chloroform. The complex has an absorption maximum at 440 nm. A 20 fold of excess of reagent was required for complete complex formation. Beer’s law was obeyed for platinum(IV) concentration in the range of 4-12 µg mL-1 and the optimum concentration range was 6-12 µg mL-1 of platinum(IV) as evaluated by Ringbom’s plot. The molar absorptivity and Sandell’s sensitivity were 1.03  104 L mol-1 cm-1 and 0.0189 µg cm-2, respectively. The effect of pH, heating and extraction time, concentration of reagent and interference from various ions were investigated. The stoichiometry of the extracted complex was determined by Job’s method of continuous variation, mole ratio method and slope ratio method. It was found that metal to ligand ratio was 1:2. The developed method has been successfully applied to the determination of platinum(IV) in pharmaceutical samples, catalyst and synthetic alloy sample.

Synthesis, Characterization, Antimicrobial and Theoretical Studies of V(IV),Fe(III),Co(II),Ni(II), Cu(II), and Zn(II)Complexes with Bidentate (NN) Donar Azo Dye Ligand

The new 4-[(7-chloro-2,1,3-benzoxadiazole)azo]-4,5-diphenyl imidazole (L) have been synthesized and characterized by micro elemental and thermal analyses as well as 1H.NMR, FT-IR, and UV-Vis spectroscopic techniques. (L) acts as a ligand coordinating with some metal ionsV(IV), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II). Structures of the new compounds were characterized by elemental and thermal analyses as well as FT-IR and UV-Vis Spectra. The magnetic properties and electrical conductivities of metal complexes were also determined. Study of the nature of the complexes formed in ethanol following the mole ratio method.. The work also include a theoretical treatment of the formed complexes in the gas phase, this was done using the (hyperchem-8) program for the molecular mechanics and semi-empirical calculations. The heat of formation (?Hf?), binding energy (?Eb)and total energy (?ET) for ligand and their metal complexes were calculated by (PM3) method at 298 K.The electrostatic potential of the ligand (L) was calculated to investigate the reactive sites of the molecules. PM3 were used to evaluate the vibrational and electronic spectra for the ligand (L) and their metal complexes then comparing with the experimental values. The antibacterial activity for the (L)and its metal complexes were studied against two types of pathogenic bacteria Pseudonomous aerugionosa as gram negative and Bacillus subtilis as gram positive. Furthermore, the antifungal activity against two fungi Candida albicans, and Aspergillus flavus was studied for (L) and its metal complexes.

4-(4'-Nitrobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole, a new chromogenic reagent for extractive spectrophotometric determination of copper (II) in pharmaceutical and alloy samples

A simple, selective and rapid extractive spectrophotometric method has been developed for the extraction and determination of Cu (II) with 4-(4'-nitrobenzylidene imino)-3-methyl-5-mercapto-1, 2, 4-triazole, (NBIMMT). The reagent (NBIMMT) instantly forms stable orange-red coloured complex with Cu (II) at room temperature and quantitatively extracted in chloroformat pH6.2. The extracted species exhibits absorption maximum at 470 nm against reagent blank. The Beer's law was followed in concentration range 4.75 to 16.13 ppm of Cu (II) and optimum concentration range obtained from Ringbom's plot was found to be 5 to 17.5 ppm. The molar absorptivity and Sandell's sensitivity of Cu (II)-NBIMMT in chloroform was 2.825×103 L mol-1cm-1 and 0.0224 μg cm-2, respectively. The optimum extraction conditions were evaluated by studying various parameters such as effect of pH, reagent concentration, solvents, shaking time and foreign ions. The use of masking agents enhances the selectivity of method. The composition of the extracted species was determined by Job's method, mole ratio method and verified by log-log plot. The ratio of Cu (II):NBIMMT was found to be 1:2. The proposed method was successfully applied for the determination of Cu (II) in synthetic mixtures, pharmaceutical samples and alloys.

Reversible Oxygenation of 2,4-Diaminobutanoic Acid-Co(II) Complexes.

This paper introduces the structural characterization and studies on reversible oxygenation behavior of a new oxygen carrier Co(II)-2,4-diaminobutanoic acid (DABA) complex in aqueous solution. The composition of the oxygenated complex was determined by gas volumetric method, molar ratio method, and mass spectrometry, and the formula of the oxygenated complex was determined to be [Co(DABA)2O2]. In aqueous solution, the complex can continuously uptake and release dioxygen and exhibit excellent reversibility of oxygenation and deoxygenation ability. This complex can maintain 50% of its original oxygenation capacity after 30 cycles in 24 h and retain 5% of the original oxygenation capacity after more than 260 cycles after 72 h. When a ligand analogue was linked to histidine (His), the new complex exhibited as excellent reversible oxygenation property as His-Co(II) complex. Insight into the relationship between structural detail and oxygenation properties will provide valuable suggestion for a new family of oxygen carriers.