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The self-assembly of trivalent lanthanide ions with ditopic organic spacers results in the formation of complex tiling patterns that mimic the structural motifs of quasi-periodic 2D materials. The assembly of trans-{LnI2}+ nodes (Ln = Gd, Dy) with both closed-shell and anion radicals of 4,4'-bipyridine affords rare examples of Archimedean tessellations in a metal-organic framework. We furthermore demonstrate occurrence of sizable magnetic exchange interactions and slow relaxation of magnetization behaviour in a complex tessellation pattern. The implementation of Archimedean tessellations in lanthanide(III) coordination solids couriers a strategy to design elusive quasi-periodic metal-organic frameworks with inimitable magnetic properties

We report the synthesis of pyrazine-pillared metal–organic frameworks (MOFs) generated through ligand substitution of the Group 6 metal hexacarbonyls. The obtained frameworks exhibit hexagonal pore channels with CO-plastered porewalls. This series constitutes the first crystallographically characterized examples of Cr(0), Mo(0), and W(0)-based MOFs and suggests the exploration of homoleptic metal carbonyls as starting materials to generate polymeric materials with low-valent metal nodes.

The quest for simple ligands to participate in concerted base metal-ligand multiple-electron redox events is driven by perspectives of replacing noble metals in catalysis and for discovering novel chemical reactivity. Yet the vast majority of simple ligand systems displays electrochemical potentials impractical for catalytic cycles substantiating the importance of new strategies towards aligned metal–ligand orbital energy levels. We herein demonstrate the possibility to establish and tame the elusive non-innocence of the ubiquitous acetylacetonate (acac), that is the most commonly employed anionic, chelating ligand towards elements across the entire Periodic Table. By employing the ligand field in the high-spin Cr(II) as a thermodynamic switch, we were able to chemically tailor the occurrence of metal–ligand redox events. The very mechanism can be understood as a destabilization of the dz2 orbital relative to the pi* LUMO of acac, which proffers a generalizable strategy to synthetically engineer non-innocence with seemingly redox-inactive ligands.

The quest for simple ligands that enable multi-electron metal–ligand redox chemistry is driven by a desire to replace noble metals in catalysis and to discover novel chemical reactivity. The vast majority of simple ligand systems display electrochemical potentials impractical for catalytic cycles, illustrating the importance of creating new strategies towards energetically aligned ligand frontier and transition metal d orbitals. We herein demonstrate the ability to chemically control the redox-activity of the ubiquitous acetylacetonate (acac) ligand. By employing the ligand field of high-spin Cr(ii) as a switch, we were able to chemically tailor the occurrence of metal–ligand redox events via simple coordination or decoordination of the labile auxiliary ligands. The mechanism of ligand field actuation can be viewed as a destabilization of the dz2 orbital relative to the π* LUMO of acac, which proffers a generalizable strategy to synthetically engineer redox-activity with seemingly redox-inactive ligands., Tailoring the chemical surroundings of chromium(ii) allows reversible electron-transfer to the ubiquitous, purportedly redox-inactive acetylacetonate.

β-Diketonates, such as acetylacetonate, are amongst the most common bidentate ligands towards elements across the entire periodic table and are considered wholly redox-inactive in their complexes. Herein we show that complexation of 1,1,1,5,5,5- hexafluoroacetylacetonate (hfac-) to Cr(II) spontaneously affords Cr(III) and a reduced beta-diketonate ligand radical, as evidenced by crystallographic analysis, magnetic measurements, optical spectroscopy, reactivity studies, and DFT calculations. The possibility of harnessing ß-diketonates as electron reservoirs opens up possibilities for new metal-ligand concerted reactivity in the ubiquitous β-diketonate coordination chemistry.