Search

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 detailed chemical composition of crude oil in subsurface reservoirs provides important information about reservoir connectivity and can potentially play a very important role for the understanding of recovery processes. Relying on studying produced oil samples alone to understand the rock-fluid and fluid-fluid interactions is insufficient as the heavier polar components may be retained by tight reservoirs and not produced. These heavy and polar compounds that constitute the resin and asphaltene fractions of crude oil are typically present in low concentrations and yet are determining for the physical-chemical properties of the oil because of their polarity. In order to obtain a fingerprint analysis of oils including polar compounds from different wells, the oil content of drill cores has been extracted and analyzed. Infrared spectroscopy has been used to perform chemical fingerprinting of the oil extracted from drill cores sampled in different geographical locations of the Danish North Sea. Statistical analysis has been employed to identify the chemical differences within the sample set and explore the link between chemical composition and geographic location of the sample. A principal component analysis, based on spectral peak fitting in the 1800-1400 cm-1 range, has allowed for statistical grouping of the samples and identified the primary chemical feature characteristic of these groups. Statistically significant differences in the quantities of polar oxygen- and nitrogen-containing compounds were found between the oil wells. The results of this analysis have been used as guidelines and reference to establish an express statistical approach based on the full-range infrared spectra for a further expansion of the sample set. The chemical information presented in this work is discussed in relation to oil fingerprinting and geochemical analysis.

Quinoid-based ligands constitute the most common class of redox-active ligands used to construct electrically conductive and magnetic metal–organic frameworks (MOFs). Whereas this chemistry is intensively explored for transition-metal and lanthanide ions, any related actinide compound has not received attention. In particular, the MOF chemistry of actinide ions in the lower oxidation states is underexplored. We herein report the synthesis, and structural and physical property characterization of a uranium(IV) quinoid-based MOF, [U(Cl2dhbq)2(H2O)2]·4H2O (1, Cl2dhbq2– = deprotonated 2,5-dichloro-3,6-dihydroxybenzoquinone). 1 is a rare example of a U(IV)-based coordination solid and the first material to incorporate bona fide reducible bridging ligands. Despite the anticipated thermodynamic driving force, no indications of valence tautomerism are evident from magnetometry, near-IR spectroscopy, and X-band electron paramagnetic resonance measurements. These initial results suggest that reduction potentials alone are insufficient as guidelines for the prediction of the occurrence of electron transfer in uranium–quinoid-based materials.

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.