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In the discussion that follows some of the more recent progress in the area of anion binding by synthetic polyamine receptors is presented, with emphasis given to work undertaken by the authors’ groups. A continuing theme in these studies has been the relationship between receptor structure and its anion extraction properties. Systematic solvent extraction and structural studies for halide and perrhenate complexes with polyamines of tripodal, macrocyclic and macrobicyclic architecture that contain both aromatic moieties and four to eight amine functions have been performed in order to derive relevant structure-binding/extractability relationships. The results demonstrate that the binding and extraction behaviour of the polyamines towards halides and perrhenate is a complex function of their structural features, degree of protonation and lipophilic properties. The extraction is characterized by the preferred formation of mono- and diprotonated amine species in the organic phase. X-ray structure studies of iodide and perrhenate complexes with open-chain tetraamino derivatives and octaamino cryptands in different protonation states lead to the conclusion that in the first case only limited chelation of the anion occurs and in the second only highly protonated species are able to encapsulate the anion. The structural patterns observed are strongly influenced by the presence of water molecules in the crystals.

The novel supramolecular assembly of composition [{(bz3tren)H4}4+ · (ReO4)— · 3(Cl)—] resulted from the self-organization of a mixture of tris[2-(benzylamino)ethyl]amine (bz3tren), HCl and NH4ReO4 at a molar ratio of 1:4.7:1 in methanol. The crystal architecture is characterized by stacks of repeating sandwich-type building blocks that contain charge-assisted N—H···O(Re) hydrogen bonds [N···O 2.81-2.86A] and weaker C—H···O(Re) interactions [C···O 3.11A]. The stacks are further linked by N—H···Cl [N···Cl 3.03A] and weaker C—H···Cl [C···Cl 3.47-3.74A] interactions into two-dimensional layers bordered by the benzyl groups of the [(bz3tren)H4]4+ cations. Edge-to-face C—H···π interactions involving the aromatic rings occur within and between the layers. The protonation constants of bz3tren in methanol were determined by potentiometric titration. The corresponding structures of the ligand in its different protonation states were calculated at the DFT-level. Anionen-gesteuerte supramolekulare Selbstorganisation von vierfach protoniertem Tris[2-(benzylamino)ethyl]amin Eine neue supramolekulare Verbindung der Zusammensetzung [{(bz3tren)H4}4+ · (ReO4)— · 3(Cl)—] wurde durch Selbstorganisation einer Mischung von Tris[2-(benzylamino)ethyl]amin (bz3tren), HCl und NH4ReO4 im Molverhaltnis 1:4.7:1 in Methanol erhalten. Ihre Kristallstruktur ist durch Stapel sandwichartiger Baueinheiten charakterisiert, die auf ladungsunterstutzten N—H···O(Re)-Wasserstoffbruckenbindungen [N···O 2.81—2.86A] und schwacheren C—H···O(Re)-Wechselwirkungen [C···O 3.11A] beruhen. Diese Stapel sind uber ein ausgepragtes zweidimensionales Wasserstoffbruckennetzwerk unter Nutzung von N—H···Cl-[N···Cl 3.03A] und schwacheren C—H···Cl-Bindungen [C···Cl 3.47—3.74A] verknupft. Zusatzliche C—H···π-Wechselwirkungen zwischen den endstandigen Benzylgruppen des Kations [(bz3tren)H4]4+ fuhren schlieslich zu einer dreidimensionalen Struktur. Die Protonierungskonstanten von bz3tren wurden in Methanol durch potentiometrische Titration bestimmt; Strukturanderungen des Liganden wurden in Abhangigkeit von der Protonierung durch DFT-Rechnungen ermittelt.

The interaction of silver(I) nitrate with the polypyridyl ligand (L) formed from two dipyridylamine units joined at their secondary amines by a 2,6-lutidinyl bridge results in a molecular ladder motif that consists of pairs of cationic [Ag2(L)MeCN]2+ units bridged by an unprecedented [Ag2(NO3)6]4− anion.

A new metallo-capsule has been synthesised that consists of three copper(II) ions and two molecules of a tris-deprotonated tripodal ligand in which three 2,4-pentanedione groups are linked via their gamma-carbons through thioether spacers to the 1,3,5-positions of a triazine core.