Copper complexes of a p-phenylenediamine-based bis(tridentate)
ligand
Abstract
A new bis(tridentate) compound,
N,N,N′,N′-tetrakis(2-
pyridylmethyl)benzene-1,4-diamine (tpbd), its diprotonated derivative,
[H
2
tpbd]
2+
, and a dicopper complex
[Cu
2
(tpbd)(H
2
O)
4
][S
2
O
6
]
2
have been prepared and structurally characterized.
The pyridyl nitrogen atoms are strongly hydrogen bonded in the crystal
structure of the yellow diprotonated salt
tpbd·2HClO
4
·2Me
2
CO. The
bis(picolyl)amine ends of the ligand show a meridional-type
co-ordination to the copper ions in the complex. Magnetic susceptibility
measurements on
[Cu
2
(tpbd)(H
2
O)
4
][S
2
O]
2
indicate that the p-phenylenediamine bridge commutes a
weak antiferromagnetic coupling
[J = -15.56(6) cm
-1
]. Two
related dicopper complexes, Cu
2
(tpbd)Cl
4
and
Cu
2
(tpbd)(NO
3
)
4
, were also isolated.
The ESR spectra of the chloride and nitrate complexes indicated
negligible magnetic exchange coupling. Reaction of tpbd with
one-electron oxidants generated a purple radical cation which has been
characterized by ESR and UV/VIS spectroscopy.
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