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1
[Ga2(HLC)3] (4) in solution was assessed using H NMR spec-
troscopy. Complex 2 is soluble in CD3Cl producing in this
solvent a clean spectrum, consistent with the expected ideal-
ized symmetry (Fig. 2, top). The latter features nine signals,
analogous to those shown by the free ligand25 (ESI†) without
the peak of the enolic –OH. Complex 4 is only scarcely soluble
in DMF. In this solvent it produces a more complex spectrum
(Fig. 2, bottom) consistent with the lack of mirror symmetry
of HLC2−. The asymmetry of the complex is only reflected by
the splitting of the peaks corresponding to the phenol –OH
groups (inset Fig. 2, bottom) and the peaks most directly con-
nected to the metals (e and k in Fig. 2, bottom). The remainder
of the signals are not sensitive to the configuration of the
ligands within the molecule. These results are in full agree-
ment with the structure of 4 observed in the solid state.
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Conclusions
In conclusion, we have shown here the first results of a new
synthetic approach to make specific non-symmetric helicates
with bis-(β-diketonate) ligands. Interestingly, the stability of
such supramolecular motifs in solution opens the possibility
of evaluating their potential towards biomolecular targets. In
that sense, we are now implementing this strategy for the pro-
duction of new asymmetric ligands featuring both hydrogen
donor units and moieties favoring π-stacking interactions,
from which the resulting helicates could potentially present
the characteristics required to significantly enhance DNA
bonding.
Conflicts of interest
There are no conflicts to declare.
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Acknowledgements
G. A. thanks the Generalitat de Catalunya for the prize ICREA
Academia 2018 and QUANTERA for project SUMO (through
Spanish PCI2018-093106). The authors acknowledge funding
by the Spanish MINECO through PGC2018-098630-B-I00 (G. A.,
L. A. B., D. A., M. D., R. D., P. L. and J. G.) and MAT2017-
86826-R (O. R.), as well as through the Juan de la Cierva
program IJCI-2016-29901 (D. A.). This research used resources
of the Advanced Light Source, which is a DOE Office of Science
User Facility under contract no. DE-AC02-05CH11231 (S. J. T.).
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Notes and references
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