Wirt-Gast-Komplexe von [bfu.bfu.bfu]: Vorhersage von Ionenselektivitäten mittels quantenchemischer Rechnungen XIII

The CH2–O–C2H4–O–CH2 moieties in Lehn’s cryptand [2.2.2] have been substituted by 2,2′-bifurane groups to get the cryptand [bfu.bfu.bfu]. The ion selectivity of this new cryptand was investigated by DFT calculations (RB3LYP/LANL2DZp, RB3LYP/LACVP*, RBP86/LANL2DZp and RBP86/LACVP*) based on model equations and analysis of the [M ⊂ bfu.bfu.bfu] n+ cryptate structures. The cryptand [bfu.bfu.bfu] is best suited for the alkali cations Na+ and K+, and the alkaline earth cation Sr2+ followed by Ca2+. The cavity of [bfu.bfu.bfu] is thus similar to that in [phen.phen.phen] or [bpy.bpy.bpy]. The selectivity of [bfu.bfu.bfu] is due to the flexibility of the OCCO und CN···NC dihedral angles. The results are independent of the selected DFT methods.

Inorganic reaction mechanisms. A personal journey

This review covers highlights of the work performed in the van Eldik group on inorganic reaction mechanisms over the past two decades in the form of a personal journey. Topics that are covered include, from NO to HNO chemistry, peroxide activation in model porphyrin and enzymatic systems, the wonder-world of Ru^III(edta) chemistry, redox chemistry of Ru(iii) complexes, Ru(ii) polypyridyl complexes and their application, relevant physicochemical properties and reaction mechanisms in ionic liquids, and mechanistic insight from computational chemistry. In each of these sections, typical examples of mechanistic studies are presented in reference to related work reported in the literature.

Bifunctional (64)Cu-labelled macrobicyclic cage amine isothiocyanates for immuno-positron emission tomography

New macrobicyclic cage amine or "sarcophagine" (sar) bifunctional chelators have been synthesised that form copper complexes of exceptional in vivo stability and incorporate isothiocyanate (-NCS) functional groups for conjugation to an antibody. The chelators were synthesised from the methyl-capped complex [Mg(II)(CH3)(NH2)sar](2+). Coordination of Mg(II) within the cavity of the cage amine ligand protects the secondary amine atoms from reacting with the -NCS functional groups. Two different [Mg(II)(NCS-sar)](2+) derivatives were conjugated to the HER2/neu-targeting antibody trastuzumab and the progress of the reaction monitored by electrospray mass spectrometry. The Mg(II) ion was removed from the immunoconjugates under mild conditions (0.1 M citrate buffer, pH 6). Labelling of the (CH3)(p-NCS-Ph)sar-trastuzumab conjugate with (64)Cu(II), a radioisotope suitable for positron emission tomography (PET), was fast (∼5 min) and easily performed at room temperature with high radiochemical purity (>95%). Biodistribution and PET imaging studies in vivo showed that (64)Cu-labelled (CH3)(p-NCS-Ph)sar-trastuzumab maintained high stability under physiological conditions with high and selective uptake in a HER2-positive cancer cell line. The stability of the copper complex and the 12.7 h half-life of the radioisotope allows clear visualisation of tumours out to 48 h.

Complexation of some alkali and alkaline earth metal cations by macrocyclic compounds containing four pyridine subunits – a DFT study

Tetradentate pyridine-based macrocyclic compounds offer useful ligands capable of efficient and selective complexation of M = Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺and Ca²⁺.

Host-guest complexes of calix[4]tubes--prediction of ion selectivity by quantum chemical calculations VI

The selectivity of the bis(calix[4]arene)tetraethylene abbreviated as calix[4]tube for the endohedral complexation of alkali and alkaline earth metal ions, was predicted on the basis of structures and complex formation energies computed with three different quantum chemical methods: DFT LANL2DZp)/LANL2DZp), PM3/SPASS, and PM6. A comparison with published X-ray structures demonstrated that the most reliable results were achieved applying DFT calculations. The complexation of K⁺ and Ba²⁺ is most favorable, followed by the encapsulation of Rb⁺ and Sr²⁺, respectively. The flexibility of the tube, described by the torsion angles associated with the ethylene linkages between the calix[4]arene units and phenyl rings intersecting the plane of the four methylene carbon atoms, also makes an important contribution to its selectivity. In general, the cavity size is similar to [2.2.2] and [N2N2N2], the cryptands with the largest cavities previously studied in our group applying a similar protocol.

Host-guest complexes of mixed glycol-bipyridine cryptands: prediction of ion selectivity by quantum chemical calculations, part V

The selectivity of the cryptands [2.2.bpy] and [2.bpy.bpy] for the endohedral complexation of alkali, alkaline-earth and earth metal ions was predicted on the basis of the DFT (B3LYP/LANL2DZp) calculated structures and complex-formation energies. The cavity size in both cryptands lay between that for [2.2.2] and [bpy.bpy.bpy], such that the complexation of K(+), Sr(2+) and Tl(3+) is most favorable. While the [2.2.bpy] is moderately larger, preferring Rb(+) complexation and demonstrating equal priority for Sr(2+) and Ba(2+), the slightly smaller [2.bpy.bpy] yields more stable cryptates with Na(+) and Ca(2+). Although the CH2-units containing molecular bars fixed at the bridgehead nitrogen atoms determine the flexibility of the cryptands, the twist angles associated with the bipyridine and glycol building blocks also contribute considerably.