Solvent-dependent self-assembly of an amphiphilic copper(II) complex with bulky head groups

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Schreck, Constantin ; Weihermüller, Johannes ; Thoma, Peter ; Rosenfeldt, Sabine ; Drechsler, Markus ; Förster, Christoph ; Heinze, Katja ; Hörner, Gerald ; Weber, Birgit:
Solvent-dependent self-assembly of an amphiphilic copper(II) complex with bulky head groups.
In: European Journal of Inorganic Chemistry. Bd. 2022 (2022) Heft 27 . - e202200341.
ISSN 1099-0682
DOI: https://doi.org/10.1002/ejic.202200341

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Abstract

The aggregation behavior of an amphiphilic copper(II) complex was studied in solution by means of UV-Vis and EPR spectroscopy. While dilute solutions in polar media do not give indication of relevant intermolecular interactions, concentrated solutions in nonpolar media clearly do not reflect the molecular properties of [CuL] (H 2 L : N 2 O 2 ligand of the Jäger-type with bulky head-group and long alkoxy tailing). Massive broadening of EPR-lines is prevalent in non-polar media, such as n -heptane and iso -octane. In combination with DFT-modelling, the solvent-dependence of the EPR response (line widths and Cu-hyperfine coupling) could be associated with the formation of oligomers with weak anti-ferromagnetically coupled copper centers. Weak anti-ferromagnetic coupling becomes evident also by SQUID magnetometry at T < 10 K of solid samples of [CuL] . The tendency towards supramolecular aggregation is unequivocally shown by electron microscopy of dried (TEM) and frozen samples (cryo-TEM). While the former approach gives evidence of the formation of extended 2D sheet-like structures with extensions on the micrometer scale, the latter technique identifies the formation of 1D thread-like structures with lengths of several hundred nanometers.