Mozaffar Asadi,1,* Sheida Esmaielzadeh1 and Khosro Mohammadi2,*
1 Chemistry Department, College of Sciences, Shiraz University, Shiraz 71454, I.
R. Iran
2 Chemistry Department, Faculty of Sciences, Persian Gulf University, Bushehr
75169, I. R. Iran
* Corresponding author: E-mail: asadi@susc.ac.ir,
mozaffarasadi@yahoo.com;
Phon +98711 228 4822, Fax: +98 711 228 0926
Abstract
Some new cobalt(III) complexes: [Co(Chel)(PBu3)]ClO4.H2O (where Chel: cdsalen,
cd5OMesalen, cd5Brsalen,
cd5Clsalen, cd5NO2salen, cdMesalen, cdPhsalen) and cdsalen =
{methyl-2-[N-[2-(2-phenolate)methylidynenitrilo]
ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate; cd5OMesalen =
{methyl-2-[N-[2-(5-methoxy-2-phenolate)
methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate; cd5Brsalen
= {methyl-2-[N-[2-(5-bromo-2-
phenolate)methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate;
cd5Clsalen = {methyl-2-[N-[2-(5-
chloro-2-phenolate)methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate;
cd5NO2salen = {methyl-2-
[N-[2-(5-nitro-2-phenolate)methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate;
cdMesalen =
methyl-2-{N-[2-(2-hydroxyphenyl)ethylidynenitrilo]ethyl}amino-1-cyclopentenedithiocarboxylate
and cdPhsalen =
methyl-2-{N-[2-(2-hydroxyphenyl)phenylidynenitrilo]ethyl}amino-1-cyclopentenedithiocarboxylate
were synthesized
and characterized using elemental analysis, 1H NMR and IR spectra. The formation
constants and the thermodynamic
parameters were measured spectrophotometrically for 1:1 adduct formation of
[Co(Chel)(PBu3)]ClO4.H2O (where
Chel: cdsalen, cd5OMesalen, cd5Brsalen, cd5Clsalen, cd5NO2salen, cdMesalen,
cdPhsalen) as acceptors with some
aliphatic amines such as n-butylamine, sec-butylamine, tert-butylamine,
benzylamine, dibutylamine and diethylamine
as donors, in 98% methanol solvent and in constant ionic strength (I = 0.1 M
NaClO4) and at various temperatures T =
283 to 313 (K) by using Ketelaar and van’t Hoff equations. The trend of the
reactivity of the donors (amines) toward a
given cobalt(III) Schiff base complex is as follow: n-butylamine > benzylamine >
sec-butylamine > tert-butylamine >
diethylamine > dibutylamine. Also, the comparison of formation constants and the
thermodynamic parameters show
that the trend of formation constants of five-coordinate cobalt(III) Schiff base
complexes toward a given donor is as follows:
cd5OMesalen > cdsalen > cd5Brsalen > cd5Clsalen > cd5NO2salen and cdMesalen >
cdsalen > cdPhsalen.
Keywords: Thermodynamic parameters, cobalt complex, schiff base, formation constants, amine.