Synthesis and structure investigation of the antibiotic amoxicillin complexes of d-block elements
The study of some transition metals (M) and amoxicillin trihydrate (ACT) ligand complexes (M–ACT) that formed in solution involved the spectrophotometric determination of stoichiometric ratios and their stability constants and these ratios were found to be M:ACT = 1:1, 1:2 and 2:1 in some instances....
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Published in | Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Vol. 61; no. 9; pp. 2231 - 2238 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
England
Elsevier B.V
01.07.2005
|
Subjects | |
Online Access | Get full text |
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Summary: | The study of some transition metals (M) and amoxicillin trihydrate (ACT) ligand complexes (M–ACT) that formed in solution involved the spectrophotometric determination of stoichiometric ratios and their stability constants and these ratios were found to be M:ACT = 1:1, 1:2 and 2:1 in some instances. The calculated stability constants of these chelates, under selected optimum conditions, using molar ratio method have values ranging from
K
f = 10
7 to 10
14. These data were confirmed by calculations of their free energy of formation Δ
G, which corresponded to their high stabilities. The separated solid complexes were studied using elemental analyses, IR, reflectance spectra, magnetic measurements, mass spectra and thermal analyses (TGA and DTA). The proposed general formulae of these complexes were found to be
ML
(
H
2
O
)
w
(
H
2
O
)
x
(
OH
)
y
(
Cl
)
z
, where M = Fe(II), Co(III),
w
=
0
,
x = 2,
y = 1,
z = 0; M = Co(II),
w
=
0
,
x = 1,
y = 0,
z = 1; M = Fe(III),
w
=
0
,
x = 1,
y = 2,
z = 0; M = Ni(II), Cu(II) and Zn(II),
w
=
2
,
x = 0,
y = 1,
z = 0, where
w
= water of crystallization,
x = coordinated water,
y = coordinated OH
− and
z = Cl
− in the outer sphere of the complex. The IR spectra show a shift of
ν(NH) (2968
cm
−1) to 2984–2999
cm
−1of imino group of the ligand ACT and the absence of
ν(CO) (β-lactame) band at 1774
cm
−1 and the appearance of the band at 1605–1523
cm
−1 in all complexes suggest that 6,7-enolization takes place before coordination of the ligand to the metal ions. The bands of M
N (at 625–520
cm
−1) and of M
O (at 889–7550
cm
−1) proved the bond of N (of amino and imino groups) and O of C
O group of the ligand to the metal ions. The reflectance spectra and room temperature magnetic measurements refer to octahedral complexes of Fe(II) and Fe(III); square planner form of Co(II), reduced Co(III), Ni(II) and Cu(II)–ACT complexes but tetrahedral form of Zn–ACT complex. The thermal degradation of these complexes is confirmed by their mass spectral fragmentation. These data confirmed the proposed structural and general formulae of these complexes. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1386-1425 |
DOI: | 10.1016/j.saa.2004.08.022 |