Chemistry Reference
In-Depth Information
ð
6
Þ
Close proximity between the phenanthrolines in [Phen
2
]
PA
AcPEI would lead to strong
binding of metal ions. For the Cu(
II
) complex of [Phen
2
]
PA
AcPEI, log K
f
was 17.0 when
the phenanthrolines were fully deprotonated. The effectiveness of cooperation be-
tween two phenanthroline moieties within a binding site for the Cu(
II
) ion of [Phen
2
]-
PA
AcPEI may be expressed in terms of effective molarity, an idea originally introduced
as a measure of the efficiency of intramolecular compared with intermolecular cata-
lysis [38]. The effective molarity of a phenanthroline toward a Cu(
II
) ion bound to the
other phenanthroline in the phenanthroline pair (
3
) was estimated as 10
6
M
.
3
The effective molarity measured for [Phen
2
]
PA
AcPEI may be compared with that for
enterobactin, the strongest microbial siderophore, containing three catechol units con-
nected by a spacer. The effective molarity of a catechol unit towards a Fe(
III
) ion bound
to another catechol unit contained in enterobactin is estimated to be 3
10
4
M
[37].
Enterobactin contains three catechol units, whereas the Cu(
II
) binding site of [Phen
2
]-
PA
AcPEI consists of only two phenanthrolines. Nevertheless, the effective molarity ob-
served for [Phen
2
]
PA
AcPEI is extraordinary for a synthetic system.
Designing active sites containing functional moieties with high effective molarities
is necessary for the construction of effective synthetic molecules with high enzyme-
like or antibody-like activities. Cross-linkage of building blocks preassembled by a scaf-
fold by single or double attachment to PEI produced synthetic polymers effective for
catalysis or molecular recognition.
