ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2006, Vol. 32, No. 10, pp. 756–760. © Pleiades Publishing, Inc., 2006.
Original Russian Text © G.M. Mamardashvili, O.M. Kulikova, 2006, published in Koordinatsionnaya Khimiya, 2006, Vol. 32, No. 10, pp. 786–790.
The axial coordination (extra coordination) of
ligands is typical of many complexes with the planar
coordination core, particularly, of
metalloporphyrins. The structure, composition, and sta-
bility of the complexes formed are determined by the
porphyrin basicity, the nature of the axial ligand and
solvent. The inﬂuence of the nature of a ligand or por-
phyrin on the processes of complex formation is stud-
ied sufﬁciently extensively today [1–4], while the effect
of a solvent on the complexation reactions of metal-
loporphyrins is studied to a lesser extent. The reactions
of coordination of the ligands with Zn porphyrinates
were commonly investigated in toluene, benzene,
dichloromethane, chloroform, and tetrachloromethane
[1–6], while data for the other solvents are almost
absent in the literature.
The aim of this work was to study the effect of intro-
duction of the additives of monobasic alcohols (metha-
nol and ethanol) on the processes of pyridine (
dination with Zn 2,3,7,8,12,13,17,18-octaethylporphy-
) and Zn 5,10,15,20-tetraphenyl-
) in toluene. The data on the com-
plexation reactions of porphyrins with different ligands
in binary solvents make it possible to estimate in detail
the effect of the solvent nature on this process, in par-
ticular, during introduction of one or another additive
(which is necessary due to limited solubility of reac-
tants in individual solvents).
Porphyrinates ZnP(1) and ZnP(2) were synthesized
and puriﬁed by the known procedures [7, 8]. The sol-
vents and pyridine were puriﬁed and dehydrated by
standard procedures .
The complex formation reaction of Zn porphyri-
nates with pyridine was investigated by spectrophoto-
metric titration in the region of the Soret band, which
has the maximum intensity. The composition of a
molecular complex formed was determined from the
slope of the plots vs.
The Effect of a Solvent on Complexation
of Zn Porphyrinates with Pyridine
G. M. Mamardashvili and O. M. Kulikova
Institute of Solution Chemistry, Russian Academy of Sciences, ul. Akademicheskaya 1, Ivanovo, 153045 Russia
Received October 27, 2005
—Spectrophotometric titration was used to study complexation reactions of Zn 2,3,7,8,12,13,17,18-
octaethylporphyrinate and Zn 5,10,15,20-tetraphenylporphyrinate with pyridine in binary solvents toluene–
methanol and toluene–ethanol at different alcohol concentrations at
. Capability of both porphyrinates to
give complexes with pyridine in a binary solvent, i.e., toluene–monobasic alcohol, was found to decrease by
more than one order of magnitude as the alcohol concentration increased from 0 to 1 mole fraction. The effect
of the solvent polarity and extent of its association due to hydrogen bonds on the complexing capability of both
porphyrinates was discussed.