We provide spectroscopic and computational evidence for a substantial change in structure and gas phase reactivity of Al3O4 + upon Fe-substitution, which is correctly predicted by multireference (MR) wave function calculations. Al3O4 + exhibits a cone-like structure with a central trivalent O atom (C3v symmetry). The replacement of the Al- by an Fe atom leads to a planar bicyclic frame with a terminal Al–O•– radical site, accompanied by a change from the Fe+III/O–II to the Fe+II/O–I valence state. The gas phase vibrational spectrum of Al2FeO4 + is exclusively reproduced by the latter structure, which MR wave function calculations correctly identify as the most stable isomer. This isomer of Al2FeO4 + is predicted to be highly reactive with respect to C–H bond activation, very similar to Al8O12 + which also features the terminal Al–O•– radical site. Density functional theory, in contrast, predicts a less reactive Al3O4 +-like “isomorphous substitution” structure of Al2FeO4 + to be the most stable one, except for functionals with very high admixture of Fock exchange (50%, BHLYP).

Even though aluminas and aluminosilicates have found widespread application, a consistent molecular understanding of their surface heterogeneity and the behavior of defects resulting from hydroxylation/dehydroxylation remains unclear. Here, we study the well‐defined molecular model compound, [Al3(μ2‐OH)3(THF)3(PhSi(OSiPh2O)3)2], 1, to gain insight into the acid–base reactivity of cyclic trinuclear Al3(μ2‐OH)3 moieties at the atomic level. We find that, like zeolites, they are sufficiently acidic to catalyze the isomerization of olefins. DFT and gas phase vibrational spectroscopy on solvent‐free and deprotonated 1 show that the six‐membered ring structure of its Al3(μ2‐OH)3 core is unstable with respect to deprotonation of one of its hydroxy groups and rearranges into two edge‐sharing four‐membered rings. This renders AlIV−O(H)−AlIV units strong acid sites, and all results together suggest that their acidity is similar to that of zeolitic SiIV−O(H)−AlIV groups.

A novel and efficient strategy in obtaining series of mono-and bi-armed azobenzene-containing poly(3-caprolactone)s is described, starting from a commercially available azobenzene dye via azide/alkyne-"click"-reactions. The attachment of alkyne-telechelic poly(3-caprolactone)s (1 kDa and 3 kDa), followed by chromatographic separation, allowed the attachment of either one or two PCl-chains to either side of the azobenzene-dye. The resulting mono-and bi-armed photo-switchable polymers are fully characterized by 2D-NMR techniques and show a high thermal stability. Additionally liquid chromatography at critical conditions (LCCC) coupled to ESI-TOF allowed us to prove the presence of either one or two polymer chains affixed onto the central azobenzene dye.

The vibrational spectra of the copper(i) cation–dihydrogen complexes Cu+(H2)4, Cu+(D2)4 and Cu+(D2)3H2 are studied using cryogenic ion trap vibrational spectroscopy in combination with quantum chemical calculations.

Obwohl Aluminiumoxide und Aluminosilicate in vielen Bereichen eingesetzt werden, bleiben deren Oberflächenheterogenität und insbesondere das Defektverhalten nach Hydroxylierung/Dehydroxylierung auf molekularer Ebene weitestgehend unverstanden. Wir untersuchen die molekulare Modellverbindung [Al3(μ2‐OH)3(THF)3(PhSi(OSiPh2O)3)2], 1, um die Säure‐Base‐Reaktivität von cyclischen Al3(μ2‐OH)3‐Einheiten aufzuklären. Wir können zeigen, dass 1, ähnlich wie Zeolithe, eine ausreichende Acidität aufweist, um die Isomerisierung von Olefinen zu katalysieren. Simulationen und Gasphasen‐Schwingungsspektroskopie an lösungsmittelfreiem und deprotoniertem 1 zeigen, dass die Deprotonierung einer Hydroxygruppe die sechsgliedrige Ringstruktur des Al3(μ2‐OH)3‐Kerns destabilisiert und in eine Struktur aus zwei kantenverknüpften viergliedrigen Ringen umlagert. Dies macht AlIV‐O(H)‐AlIV‐Einheiten zu stark sauren Funktionalitäten, und alle Ergebnisse zusammen legen nahe, dass ihre Acidität mit derjenigen zeolithischer SiIV‐O(H)‐AlIV‐Gruppen vergleichbar ist.