Reversible Breaking and Forming of Metal–Ligand Coordination Bonds: Temperature‐Triggered Single‐Crystal to Single‐Crystal Transformation in a Metal–Organic Framework

Abstract

Yb(C(4)H(4)O(4))(1.5)] undergoes a temperature-triggered single-crystal to single-crystal transformation. Thermal X-ray single-crystal studies showed a reversibly orchestrated rearrangement of the atoms generated by the breaking/formation of coordination bonds, in which the stoichiometry of the compound remains unchanged. The transformation occurs on heating the crystal at approximately 130 degrees C. This uncommon behavior was also studied by thermal methods, FTIR spectroscopy, and thermodiffractometry. Both polymorphs, alpha (room-temperature form) and beta (high-temperature form), are proven to be active heterogeneous catalysts; the higher catalytic activity of beta is owed to a decrease in the Yb coordination number. A mechanism based on spectroscopic evidence and involving formation of the active species Yb-O-OH is proposed for the sulfide oxidation.

A Temperature‐Responsive Smart Europium Metal‐Organic Framework Switch for Reversible Capture and Release of Intrinsic Eu3+ Ions

“…When the temperature is gradually increased to room temperature, the Eu 3+ vibration becomes increasingly violent, the captured Eu 3+ finally escapes the hooks into the channels and the structure is regained ( Figure 4 ). As documented, the Ln–ligand bond has ever shown the dynamics to some extent, and could be reversibly rearranged under pressure or broken and reformed by heating 15. This case is intriguing because the metal cation guests could be controlled, captured, and released through smart Eu–L interactions in a SCSC manner.…”

Towards Inorganic Porous Materials by Design: Looking for New Architectures

“…However, the cooperative effects together with the more protected coordination center inside the frameworks open the possibility of having unexpected coordination geometries respective to the molecular counterpart, in a similar way as in the metalloproteins world. It is remarkable, for example, that in the Yb succinate case [ 27 ] a reversible single-crystal to single-crystal phase transition from α to β polymorph occurs at 130 ° C. This transformation involves the change of metal coordination number from eight to seven by breaking/forming Yb-O bonds.…”

“…MOFs have advantage of the oxidant capabilities of the chosen metal; thus, hydrogen peroxide, with water as subproduct, has been tested in organic sulfi de selective oxidation reactions to sulfoxides or sulfones, as a function of reaction temperature, selected metal nature [ 52 ] (Figure 3.d) or active polymorph, [ 27 ] converting (with high selectivity) contaminants …”

Redes metalorgânicas e suas aplicações em catálise

“…O mesmo grupo mostrou a atividade de MOFs de itérbio para a mesma reação e também para a hidrodessulfurização do tiofeno e oxidação de sulfetos, mostrando a importância da densidade de carga e do número de coordenação no átomo do lantanídeo para o desempenho catalítico 100 Em outro trabalho, com MOFs de Yb e ácido succínico, eles propuseram um mecanismo para a oxidação de sulfetos, baseado em evidências espectroscópicas, em que as espécies Yb-O-OH seriam responsáveis pela atividade catalítica. 101 Eles também testaram as mesmas MOFs para as reações de oxidação de metilsulfanilbenzeno e acetalização de benzaldeído. MOFs de lantanídeos também foram testadas por Cunha-Silva et al 102 na reação de ciclodesidratação de xilose a fulfural e por Vitorino et al 103 na polimerização de Ziegler-Natta.…”