REACTIONS OF CHELATE COMPLEXES WITH MACROCYCLIC LIGANDS
351
but remains as extra ligand, i.e., it migrates together action, and, on the other hand, it creates the steric hin-
with Zn2+ to the reaction site:
H2OPTAP + Zn(L)+(Solv)n
(L)ZnOPTAP + H2L+ + n(Solv).
drances to the cation approaching the meso-nitrogen
atom. That is why the amino complexes H2OPTAP(Br)8
· M(L)– are not formed in DMSO.
ç2OPTAP(NO2)8 enter the complexation reaction
with all the studied salts (and even with Cu(Ala)2)
almost instantaneously. In the absence of the kinetic
parameters of reactions with compound III, the conclu-
sion about the molecularity of its complexation with
chelate salts is difficult.
(7)
When porphyrin coordination occurs according to the
common bimolecular mechanism, the ligand detach-
ment from the chelate salt molecule and its further addi-
tion to the zinc ion in (L)ZnOPTAP do not affect the
rate of reaction (7). One can suggest that if the reaction
proceeds through the stage of the amino complex for-
mation, then the possibility of the additional coordina-
tion of L by Zn atom in zinc porphyrin accelerates the
complexation reaction.
The introduction into the tetraazaporphyrin mole-
cule of the electron-accepting bromine atoms, which
make the ionic nature of the N–H bonds more pro-
nounced, significantly accelerates the complexation
process. In the pure pyridine, complexation occurs
almost instantaneously and therefore, the reaction rates
cannot be measured by spectrophotometric kinetic
methods [4, 5]. When the electron-accepting substitu-
ents (NO2, Br) are introduced into the phenyl rings of
ç2OPTAP, the rate of complexation reaction in chloro-
form–pyridine mixture increases 10 times [6].
ACKNOWLEDGMENTS
This work was supported by the RAS integrated
program “New principles and methods for production
and target synthesis of compounds with required prop-
erties”, project “Target synthesis of cyclic and linear
polypyrroles used as catalysts, conductors, and photo-
converters”.
REFERENCES
1. Berezin, B.D. and Mamardashvili, G.M., Koord. Khim.,
2000, vol. 26, no. 10, p. 796.
2. Berezin, B.D. and Mamardashvili, G.M., Koord. Khim.,
2002, vol. 28, no. 11, p. 822.
3. Berezin, B.D. and Khelevina, O.G., Porfiriny: Struktura.
Svoistva. Sintez (Porphyrins: Structure, Properties, and
Synthesis), Moscow: Nauka, 1985.
In the case of DMSO, this increase was even more
significant. Most of the chelate salts react with com-
pound II almost instantaneously. An exception is a
weakly coordinating salt Cu(Ala)2, which reacts with II
at a measurable rate. The introduction of eight bromine
atoms into ç2OPTAP increases the rate of its complex-
ation with ëu(Ala)2 almost by two orders of magnitude
(Table 2).
4. Chizhova, N.V., Cand. Sci. (Chem.) Dissertation,
Ivanovo: Inst. of Chemical Technology, 1990.
5. Stuzhin, P.A. and Khelevina, O.G., Coord. Chem. Rev.,
1996, vol. 147, p. 41.
6. Khelevina, O.G., Chizhova, N.V., and Rumyantseva, S.V.,
Koord. Khim., 1999, vol. 25, no. 6, p. 680.
It should be noted that unlike I, compound II is
coordinated with Cu(Ala)2 following the bimolecular
mechanism. However, as in the case with other copper
salts studied by us in [1, 12], the reaction order in the
salt is equal to ~0.5. This implies that the solution con-
tains several reactive forms of the salt.
7. Cook, A.N. and Linstead, R.P., J. Chem. Soc., 1937,
no. 6, p. 929.
8. Adler, A.D., Longo, F.R., and Finarelli, J.D., J. Org.
Chem., 1967, vol. 32, no. 2, p. 476.
9. Chizhova, N.I. and Berezin, B.D., Zh. Org. Khim., 1994,
vol. 30, no. 11, p. 1678.
The intermediate amino complex XI is likely to
form simultaneously due to the donor–acceptor interac-
tion and hydrophobic π–π-interaction of ç2OPTAP
with the ligand surrounding of the metal. On the one
hand, the introduction of a bromine atom into each phe-
nyl ring increases the electron density on the meso-
nitrogen atom and thus favors the donor–acceptor inter-
10. Chizhova, N.V., Khelevina, O.G., and Berezin, B.D., Izv.
Vyssh. Uchebn. Zaved., Khim. Khim. Tekhnol., 1994,
vol. 37, no. 1, p. 20.
11. Sharma, V.S., Mathur, H.B., and Biswas, F.B., Indian J.
Chem., 1964, vol. 2, no. 7, p. 257.
12. Mamardashvili, G.M. and Berezin, B.D., Koord. Khim.,
2000, vol. 26, no. 9, p. 699.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 29 No. 5 2003