radiative de-activation processes remain quite comparable in
the two classes of helicates, as shown by identical intrinsic
quantum yields for EuIII. That is, the inner coordination
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0
Comparing [Eu2(LC2 )3] with [Eu2(LC2)3] does not reveal any
significant difference in cell imaging properties either: same
concentration dependence (Fig. S14, ESIw), same time course
(Fig. S15, ESIw), same mechanism of uptake—endocytosis,
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Bunzli and V. K. Pecharsky, Elsevier Science B.V., Amsterdam,
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Therefore, contrary to the cyclam complex cited in the
introduction, for which a minor change in the length of one
substituent, namely the addition of one methylene group, leads
to important modifications of its biological activity,44 the
chemical and biochemical properties of the [Ln2(LCX)3] heli-
cates remain rather insensitive to the substitution in the
pyridine 4-position. This is very encouraging for the targeting
experiments we are planning to conduct in a near future and
which require modification of the tris(polyoxyethylene) pen-
dant arms of H2LC2, as well as, in some instances, a lengthen-
ing of the functionalized arm to avoid close contact between
the emissive stain and the targeted biological site. Further-
more, the data on cell leakage reported here comfort our
opinion that [Ln2(LCX)3] helicates are a viable alternative to
existing chelates reported in the literature for bio-medical
analyses and imaging.41
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This work is supported through grants from the Swiss Na-
tional Science Foundation (200020-119866/1) and the Swiss
Secretariat for Education and Research (project C07.0116).
Selected funding from the European Science Foundation
through COST action D38 is also acknowledged. We thank
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