The 12- and 14-membered diazadioxo macrocyclic ligands, 1,2 : 7,8-diphenyl-6,9-diaza-3,12-dioxocyclododecane (L
1
) and 1,2 : 8,9-diphenyl-7,10-diaza-3,14-dioxocyclotetradecane (L
2
), were ...synthesized by condensation between o-phenylenediamine, 1,2-dibromoethane/1,3-dibromopropane, and catechol. Metal complexes ML
1
Cl
2
and ML
2
Cl
2
M = Co(II), Ni(II), Cu(II), and Zn(II) were prepared by interaction of L
1
or L
2
with metal(II) chlorides. The ligands and their complexes were characterized by elemental analyses, IR,
1
H, and
13
C NMR, EPR, UV-Vis spectroscopy, magnetic susceptibility, conductivity measurements, and Electrospray ionization-mass spectral (ESI-MS) studies. The results of elemental analyses, ESI-MS, Job's method, and conductivity measurements confirmed the stoichiometry of ligands and their complexes while absorption bands and resonance peaks in IR and NMR spectra confirmed the formation of ligand framework around the metal ions. Stereochemistry was inferred from the UV-Vis, EPR, and magnetic moment studies.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
A fully automated methodology was developed for the determination of the thyroid hormones levothyroxine (T4) and liothyronine (T3). The proposed method exploits the formation of highly coloured ...charge–transfer (CT) complexes between these compounds, acting as electron donors, and π-acceptors such as chloranilic acid (CLA) and 2,3-dichloro-5,6-dicyano-
p-benzoquinone (DDQ). For automation of the analytical procedure a simple, fast and versatile single interface flow system (SIFA) was implemented guaranteeing a simplified performance optimisation, low maintenance and a cost-effective operation. Moreover, the single reaction interface assured a convenient and straightforward approach for implementing Job's method of continuous variations used to establish the stoichiometry of the formed CT complexes.
Linear calibration plots for levothyroxine and liothyronine concentrations ranging from 5.0
×
10
−5 to 2.5
×
10
−4
mol
L
−1 and 1.0
×
10
−5 to 1.0
×
10
−4
mol
L
−1, respectively, were obtained, with good precision (R.S.D. <4.6% and <3.9%) and with a determination frequency of 26
h
−1 for both drugs. The results obtained for pharmaceutical formulations were statistically comparable to the declared hormone amount with relative deviations lower than 2.1%. The accuracy was confirmed by carrying out recovery studies, which furnished recovery values ranging from 96.3% to 103.7% for levothyroxine and 100.1% for liothyronine.
Purpose: The purpose of the present study was to investigate
interaction between ketotifen fumarate and anhydrous theophylline in
aqueous media of various pH. Methods: By using Job's
...continuous-variation analysis and Ardon's spectrophotomeric
methods, the values of stability constants of theophylline with
ketotifen were determined at a fixed temperature (37 0C) at each of the
medium pH. In vitro study of protein (bovine albumin, fraction v)
binding was carried out by equilibrium dialysis method at pH 7.4 to
ascertain the influence of ketotifen on the protein binding of
theophylline. Results: Stability constant, ranging between 5.07 and
6.35, were derived from Ardon's plot, indicating that complexes
formed, as a result of interaction between the drugs, were
comparatively stable. However, following theophylline interaction with
ketotifen, stability constant was <1 at gastric pH (0.4 and 2.0) and
4.12 at intestinal pH. (6.0)The highest degree of protein binding by
ketotifen was 98 % and the lowest 90 %. For theophylline, the highest
and lowest degrees of protein binding were 90 and 85 %, respectively.
Conclusion: Concurrent administration of ketotifen and theophylline
would result in the formation of a stable complex and this is likely to
reduce the therapeutic activities of both drugs. With regard to protein
binding, the concentration of theophylline increased with decrease in
ketotifen concentration.
The purpose of the present study was to investigate the interaction between ketotifen fumarate and anhydrous theophylline in aqueous media of various pH (1.2 and 6.8). Using Job's ...continuous-variation analysis and Ardon's spectrophotomeric measurement methods, the values of the stability constants of theophylline with ketotifen were determined at a fixed temperature (37 ºC) at various pH. The stability constants, ranging between 5.66 and 9.92, were derived from Ardon's plot, indicating that comparatively stable complexes had formed as a result of an interaction between the drugs. However, following the interaction of theophylline with ketotifen, stability constants were <1 at gastric pH (1.2) and intestinal pH (6.8). Concurrent administration of ketotifen and theophylline could result in the formation of a stable complex and this is likely to reduce the therapeutic activities of both drugs.
O objetivo do presente estudo foi investigar a interação entre o fumarato de cetotifeno e a teofilina anidra em meios aquosos com vários pH (1,2 e 6,8). Utilizando a análise da variação contínua de Job e os métodos de medida espectrofotométrica de Ardon, os valores das constantes de estabilidade da teofilina com o cetotifeno foram determinados em temperatura fixa (37 oC) em vários pH. As constantes de estabilidade, variando entre 5,66 e 9,92 derivaram-se a partir do delineamento de Ardon, indicando, comparativamente, que complexos estáveis se formaram como resultado da interação entre os fármacos. Entretanto, seguindo a interação da teofilina com o cetotifeno, as constantes de estabilidade foram <1, em pH gástrico (1,2) e intestinal (8,8). A administração concomitante de cetotifeno e teofilina poderia resultar na formação de complexo estável, o que reduz a atividade terapêutica de ambos os fármacos.
Quinoline-based dye has been synthesized as a use of chemosensor for metal ions. The chemical structures and characteristics were determined by
1
H-NMR, EA, Computational calculation and cyclic ...voltammetry. The detection properties of this dye chemosensor were examined and determined using UV-Vis spectroscopy. The prepared dye showed clear detection properties for Cu
2+
and Zn
2+
. However, the sensing property between dye and Hg
2+
ion was not observed. HOMO and LUMO energy levels were determined by computational calculation and electrochemical method.
In this work, we have studied the detection properties of 1,4-dihydroxyanthracene-9,10-dione (dye 1), 3-hydroxy-2-naphthoic acid (dye 2) and methyl-3-hydroxy-2-naphthoate (dye 3), which were used as ...dye chemosensors for the metal ion complexing. Metal binding sites in dye 1, 2, and 3 show similar structural characteristics. Ketone, hydroxyl and carboxyl groups provide the functions to bind the metal ions. Metal ion detection properties of these dyes were investigated by UV-Vis absorption, fluorescent emission, HOMO/LUMO energy level and potential and job's method.
The interaction of safranin‐O (SO), a cationic dye, with anionic surfactants sodium dodecylsulfate (SDS) and sodium dodecylsulfonate (SDSo) having the same hydrophobic group but different polar ...groups was studied spectrophotometrically in the premicellar region far below the critical micelle concentration in aqueous media using the method of continuous variations, also called Job's Method. This method was applied to determine the equilibrium complex formation constant (K) as well as the molecular complex formation ratio. Both SDS and SDSo formed stable associations with SO, and the molecular complex formation ratio was determined as 1:1. The data obtained from Job's Method indicated that the equilibrium complex formation constant of SDS is higher than that of SDSo. We also studied the influence of cosolvents such as methanol, dimethylformamide (DMFA), and dioxan (DX) on molecular complex formation between SDS and SO, and observed that the presence of cosolvents inhibited molecular complex formation. This inhibitory effect of cosolvents on molecular complex formation followed the order of methanol>DMFA>DX.
On the basis of affinity of Fe(III) ions toward functional groups of 2,6-dihydroxy benzoic acid (2,6-DHB), a charge transfer complex (CT) is formed between Fe(III) ion and 2,6-DHB in acidic media. ...The stoichiometry and stability constant of the complex was determined using both mole ratio and Job’s methods. The stability constant of 1:1 complex formed in acidic media is 2.55±0.14×10
5
(mole ratio) or 2.70±0.12×10
5
(Job), in which the quantities are in agreement with together. This method was used for spectrophotometric determination of Fe(III) in aqueous media. The dynamic range and detection limit (DL) were 1.2×10
-5
to 3.6×10
-4
M and 1.5×10
-6
M, respectively. The relative standard deviation (RSD) was found to be 0.76% in the replicate treatments (n=7) with 1.6×10
-4
M Fe(III). The practical applicability of the method was confirmed using a synthetic certificated reference material (CRM) and spiked natural water samples.
UV and circular dichroism spectroscopic measurements showed that the molecular interactions in hexane/ethyl-acetate solutions between dihydroquinidine tert-butylcarbamate, used as a model for the ...quinidine carbamate chiral selector (QD), and 3-chloro-1-phenyl-propanol are too weak to affect the corresponding spectra of these compounds. The weak interactions between QD and 3-chloro-1-phenyl-propanol are probably masked by the formation of self-associated dimeric structures in solution.
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