Rhenium complexes with phosphine-containing peptides. Synthesis and characterization of oxorhenium(V) complexes with N-{N -[3-(diphenylphosphino)propionyl]glycyl}-L-S -benzylcysteine and its methyl ester
Abstract
The co-ordination of dipeptides modified with a phosphine group to
the Re![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
O
3+
core has been studied, and the new
donor sets PN
2
X (X = O or S) achieved.
N-{N-[3-(Diphenylphosphino)propionyl]glycyl
}-L-S-benzylcysteine
(H
3
L
2
) and its methyl ester derivative
(H
2
L
1
) have been used for preparing
six-co-ordinated oxorhenium(V) complexes, providing a new
chelating system for targeting
186/188
Re to protein bioactive
molecules. The complexes have been characterized by means of UV/VIS, IR,
FAB and
1
H NMR spectroscopy. The crystal structures of
[ReO(L
2
)(OH
2
)]·H
2
O·MeOH
and [ReO(L
1
)Cl] have been established. In both the complexes
the co-ordination geometry is distorted octahedral. The ligands are
tetradentate, co-ordinating the ReO
3+
moiety
through the phosphine phosphorus, the two deprotonated amide nitrogens
and the O or S atom from the carboxylate or thioether groups. When the
cysteine carboxylic moiety is free, it can replace, in organic solvents,
the thioether sulfur to give a stable complex, the fourth donor atom in
the equatorial plane being a carboxylate oxygen. In basic medium
[ReO(L
1
)Cl] underwent substitution of Cl
-
by
OH
-
, evidence for the high stability of the
PN
2
S donor set.
O
3+
core has been studied, and the new
donor sets PN
2
X (X = O or S) achieved.
N-{N-[3-(Diphenylphosphino)propionyl]glycyl
}-L-S-benzylcysteine
(H
3
L
2
) and its methyl ester derivative
(H
2
L
1
) have been used for preparing
six-co-ordinated oxorhenium(V) complexes, providing a new
chelating system for targeting
186/188
Re to protein bioactive
molecules. The complexes have been characterized by means of UV/VIS, IR,
FAB and
1
H NMR spectroscopy. The crystal structures of
[ReO(L
2
)(OH
2
)]·H
2
O·MeOH
and [ReO(L
1
)Cl] have been established. In both the complexes
the co-ordination geometry is distorted octahedral. The ligands are
tetradentate, co-ordinating the ReO
3+
moiety
through the phosphine phosphorus, the two deprotonated amide nitrogens
and the O or S atom from the carboxylate or thioether groups. When the
cysteine carboxylic moiety is free, it can replace, in organic solvents,
the thioether sulfur to give a stable complex, the fourth donor atom in
the equatorial plane being a carboxylate oxygen. In basic medium
[ReO(L
1
)Cl] underwent substitution of Cl
-
by
OH
-
, evidence for the high stability of the
PN
2
S donor set.
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