Copper(II) Coordination Chemistry of Westiellamide and Its Imidazole, Oxazole, and Thiazole Analogues

Abstract

Six molecules of an amphiphilic fullerene derivative make up the smallest persistent micelle detected so far (see picture, the six amphiphilic molecules are shown in different colors). These micelles can be used to systematically study the factors that determine the structural persistence of micelles and may lead to the design of tailor‐made supramolecular containers.

Insights into the Electronic Structure of CuII Bound to an Imidazole Analogue of Westiellamide

“…+ are in good agreement with the experimental findings from the CW and pulsed EPR, UV-vis, and CD spectroscopic studies, 22,83 which are characteristic of a square pyramidal Cu II coordination geometry with Cu II bound to the N het -N amide -N het motif.…”

Cyclic peptide marine metabolites and CuII

“…The break-through in our own studies was the accessibility of a variety of ligands based on a modular synthesis which allowed the preparation of appreciable quantities of ligands in relatively short time, and with the possibility to tune their structures and flexibilities as well as the electronics of the donor groups via the type of heterocycle and the configuration of the macrocycle side-chain. 54,56,57,65,66,68 The other important factor, leading to a comprehensive account with respect to the coordination chemistry involved, is based on the combination of various spectroscopies (UV-vis-NIR, CD, MCD, ESI-MS, NMR, EPR, HYSCORE and ENDOR) with computational modeling (structure optimization and electronic structure calculation); thorough kinetic studies and thermodynamic analyses have started to appear and begin also to be combined with modeling approaches -in this area there still is important work ahead. Obvious next steps are similar sets of experiments with other metal ions and other (hydrolysis) reactions.…”

“…The usual conformation of the cyclic pseudo-hexapeptide is strongly twisted in this silver cluster: in order to coordinate to the central silver(I) ion Ag1, the carbonyl groups of westiellamide are rotated towards the inside of the ring, thus flipping the macrocycle and rotating the amide nitrogens such that they face the outside of the macrocycle (see above for the relative stability of the various conformers of the metal-free peptide ligands Table 1). 54,55 The structures of these complexes depend on the electronic properties and, specifically also on the flexibilities of the heterocycles, and yield two structural types each for the mono-and dinuclear Cu II complexes, respectively (see Fig. 6).…”

“…6). 54 Two of the nitrogen donors originate from azole rings and one from the connecting amide group, forming the usual N het -N amide -N het bonding motif. The deprotonation is metal ion assisted and takes place at relatively low pH values -Cu II is known to be able to deprotonate amide nitrogen atoms in oligopeptides at pH ≈ 4-5).…”

Thieme Chemistry Journal Awardees - Where Are They Now? Macrocyclic Peptide Chemistry Inspired by Nature - From Chiral Artificial Receptors toward Molecular Devices

“…Within a cooperation, the intrinsic affinity of platforms 47a-c for Cu(II) ions was investigated by ESI-HRMS, spectrophotometric and polarimetric titrations, as well as by EPR and IR spectroscopy. 38 The relative signal intensities of noncoordinated platform [H 4 L] + , mononuclear [Cu II (H 2 L)] + and dinuclear [Cu II 2 (HL)(m-OCH 3 )] + complexes in the detected ESI mass spectra at various ligand/ base/Cu 2+ molar ratios suggest that triimidazole 47c is a significantly better Cu(II) acceptor than the less basic oxazole and thiazole 47a,b. Twofold Cu(II) binding may occur with a cooperative effect, in which preorganization of the second binding site by the first metal ion is further assisted by coordinated methanol donors.…”