Luminescent Coordination Polymers Constructed from a Flexible, Tetradentate Diisopyrazole Ligand and Copper(I) Halides

Design of luminescent complexes with different Cu4I4 cores based on pyridyl phenoxarsines

A series of luminescent Cu4I4 clusters with stair-step, cubane, and octahedral geometries supported by a novel type of cyclic As,N-ligand, pyridyl-containing 10-phenoxarsines, were synthesized and characterized by NMR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction analysis. An unusual arrangement of As,N-bidentate and μ2-iodo ligands was found in the octahedral cluster. The structural diversity of the Cu(I) complexes is reflected in their photophysical properties: the phosphorescence spectra of the compounds display emission in a broad spectral range of 495-597 nm. The complex with the Cu4I4L2 stoichiometry bearing a stair-step Cu4I4 core demonstrates temperature-dependent dual emission. The luminescence properties of all complexes were rationalized by DFT calculations.

Coordination modulated on-off switching of flexibility in a metal-organic framework

Stimuli-responsive metal-organic frameworks (MOFs) exhibit dynamic, and typically reversible, structural changes upon exposure to external stimuli. This process often induces drastic changes in their adsorption properties. Herein, we present a stimuli-responsive MOF, 1·[CuCl], that shows temperature dependent switching from a rigid to flexible phase. This conversion is associated with a dramatic reversible change in the gas adsorption properties, from Type-I to S-shaped isotherms. The structural transition is facilitated by a novel mechanism that involves both a change in coordination number (3 to 2) and geometry (trigonal planar to linear) of the post-synthetically added Cu(i) ion. This process serves to 'unlock' the framework rigidity imposed by metal chelation of the bis-pyrazolyl groups and realises the intrinsic flexibility of the organic link.

Aliphatic polyketones as classic yet new molecular ropes for structural diversity in organic synthesis

Polyketone compounds play an important role in organic chemistry as a prominent source of reactivity and functionality. Their chemical properties vary widely depending on the ketone sequence in carbon chains. Although vicinal and β-polyketones have been used for more than 150 years, the recent development of new ketone sequences composed of alternating 1,3- and 1,4-diketones has demonstrated the further potential of polyketones as structurally flexible molecular ropes capable of derivatization to π-conjugated chromophores and molecular assemblies. In this Feature Article, we review the synthetic strategies and reactivities of polyketones with respect to their ketone sequence. Furthermore, recent research on polyketones with hybrid ketone sequences is also discussed, focussing on their structural diversity in chemical transformations including intramolecular cyclization and stereoselective oxidation.

Modular synthesis of oligoacetylacetones via site-selective silylation of acetylacetone derivatives

Aliphatic oligoketones with tailored carbonyl and substituent sequences were modularly synthesized utilizing site-selective formation of enol silyl ethers. Their unique conformational preferences in solid-state were revealed by X-ray crystallography.