Thermal stability and degradation of Co(II), Cd(II), and Zn(II) complexes
89
synthesis and spectroscopic, magnetic, and structural properties
of bis(N-acetyl-b-alaninato)diaquacopper(II) and tetrakis[l-(N-
Conclusions
acetyl-b-alaninato)]-diaquadicopper(II) dihydrate.
structural isomerism. Inorg Chem. 1981;20:1075–80.
6. Antolini L, Menabue L, Prampolini P, Saladini M. Magnetic and
spectroscopic properties of dimeric copper(II)N-benzoylvalinates.
J Chem Soc Dalton Trans. 1982; 2109-12.
7. Cariati F, Erre L, Micera G, Menabue L, Prampolini P. Magnetic
investigations on some copper(II) N-acetyl- and N-benzoyl-
alaninates. Inorg Chim Acta. 1982;63:85–9.
8. Udupa MR, Krebs B. Crystal and molecular structure of tetra-
l-N-acetylglycinatodiaquodicopper(II). Inorg Chim Acta. 1979;
37:1–4.
9. Anagnostopulos A, Hadjispyrou S. Effects of mixed-ligand
complex formation on deprotonation of amide groups in N-ben-
zoylglycine and N-(4-aminobenzoyl)glycine. J Inorg Biochem.
1995;57:279–86.
10. Lambert DM, Geurts M, Scriba GKE, Poupaert JH, Dumont P.
Simple derivatives of amino acid neurotransmitters. Anticonvul-
sant evaluation of derived amides, carbamates and esters of
glycine and b-alanine. J Pharm Belg. 1995;50:194–203.
11. Chikaraishi Kasuga NC, Yamamoto R, Hara A, Amano A,
Nomiya K. Molecular design, crystal structure, antimicrobial
activity and reactivity of light-stable and water-soluble Ag–O
bonding silver(I) complexes, dinuclear silver(I) N-acetylglyci-
nate. Inorg Chim Acta. 2006;359:4412–6.
12. Nomiya K, Takahashi S, Noguchi R, Nemoto S, Takayama T,
Oda M. Synthesis and characterization of water-soluble silver(I)
complexes with L-histidine (H2his) and (S)-(-)-2-pyrrolidone-5-
carboxylic acid (H2pyrrld) showing a wide spectrum of effective
antibacterial and antifungal activities. Crystal structures of chiral
helical polymers [Ag(Hhis)]n and {[Ag(Hpyrrld)]2}n in the solid
state. Inorg Chem. 2000;39:3301–11.
13. Nomiya K, Takahashi S, Noguchi R. Water-soluble silver(I)
complexes of (R)-(?)- and (S)-(–)-2-pyrrolidone-5-carboxylic
acid and their antimicrobial activities. Chiral helical polymer and
polymer sheet structures in the solid-state formed by self-
assembly of dimeric [Ag(Hpyrrld)]2 cores. J Chem Soc Dalton
Trans. 2000;4369-73.
A case of
Co(II), Cd(II) and Zn(II) complexes with the N-benzylox-
ycarbonylglycinato ligand of formulae: [Co(N-Boc-gly)2
(H2O)4]ꢀ2H2O, [Cd(N-Boc-gly)2(H2O)2], and [Zn(N-Boc-
gly)2] were thermally investigated. The decomposition of
the Co(II) and Cd(II) complexes occurs in four and
decomposition of Zn(II) complex occurs in three main
steps. The suggested mechanisms of thermal degradation
showed that Co(II), Cd(II), and Zn(II) complexes have the
same fragmentation of its ligand chains. TG curves
revealed that the presence of crystallization and/or coor-
dinated water molecules decreases thermal stability of the
complexes. The observed order of decreasing stability is:
[Zn(N-Boc-gly)2] [[Cd(N-Boc-gly)2(H2O)2] [[Co(N-Boc-
gly)2(H2O)4]ꢀ 2H2O, and the same trend is found after
dehydration of Co(II) and Cd(II) complexes. With regard to
the composition and structures of complexes, it is confirmed
that the loss of crystallization and/or coordinated water
molecules cause a disturbance of crystal and molecular
structure of the complexes resulting in thermal instability of
dehydrated complexes. For the determination of the apparent
activation energy (Ea) and pre-exponential factor (A) Kis-
singer’s and Ozawa’s methods are used and results of these
two methods are in well accordance. Friedman’s method
signify that the first step of degradation in the case of Cd(II)
complex and the second step in the case of Co(II), Cd(II),
and Zn(II) complexes are not complex in nature, whereas the
first step of degradation of Co(II) and Zn(II) complexes and
third step of Co(II), Cd(II), and Zn(II) complexes are the
complex ones. A detailed characterization of individual steps
will be the subject of further systematic investigations.
14. Nomiya K, Takahashi S, Noguchi R. Synthesis and crystal
structure of three silver(I) complexes with (S)-(?)-5-oxo-2-tet-
rahydrofurancarboxylic acid (S-Hothf) and its isomeric forms
(R-Hothf and R,S-Hothf) showing wide spectra of effective
antibacterial and antifungal activities. Chiral helical polymers in
the solid state formed by self-assembly of the dimeric [Ag(othf)]2
cores. J Chem Soc Dalton Trans. 2000;1343-8.
Acknowledgements This work was supported by the Ministry of
Science and Technological Development of the Republic of Serbia,
Grant Nos. 142062 and 142030.
15. Geurts M, Poupaert JH, Scriba GKE, Lambert DM. N-(benzyl-
oxycarbonyl)glycine esters and amides as new anticonvulsants.
J Med Chem. 1998;41:24–30.
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