Photoactive Metal-Organic Frameworks for the Selective Synthesis of Thioethers: Coupled with Phosphine to Modulate Thiyl Radical Generation

Metal-organic framework (MOF) materials are intriguing photocatalysts to trigger radical-mediated chemical transformations. We report herein the synthesis and characterization of a series of isomorphic MOFs which show a novel structure, wide visible-light absorption, high chemical stability, and specific redox potential. The prepared MOFs were explored for the photoinduced single-electron oxidation of thiol compounds, generating reactive thiyl radicals to afford thioethers via a convenient thiol-olefin reaction. Importantly, we provide a widely applicable strategy by combing a photoactive MOF with phosphine to modulate the generation of thiyl radical in the reaction, thereby producing a single product of the thioether without the formation of a disulfide byproduct due to the dimerization of thiyl radicals. The photocatalytic reaction takes advantage of this strategy, showing great generality where tens of thiols and olefins have been examined as coupling partners. In addition, the strategy has also been demonstrated to be effective for the reactions catalyzed by other MOFs. Mechanism studies reveal that the selective synthesis of C-S products relies on a synergy between the photoinduced generation of a thiyl radical over the MOF and the in situ cleavage of S-S bond into a S-H bond by phosphine. It is notable that the synthesized MOFs show advanced performance in comparison with classical MOFs. The work not only provides a series of novel MOF photocatalysts that are capable of photoinduced thiol-olefin coupling but also indicates the great potential of MOFs for photochemical transformations mediated by reactive radicals.

One-dimensional networks formed via the self-assembly of anthracenedibenzoic acid with zinc(II)

Self-assembly of metal-organic coordination polymers occurs because of enthalpically favorable interactions. In the case of the bulky 4,4'-(anthracene-9,10-diyl)dibenzoic acid ligand (abdH₂), we demonstrate that the presence of numerous π-π and C-H...π interactions outweigh the formation of saturated coordination complexes with zinc, leading to the formation of a dimethylformamide (DMF) solvate, namely 4,4'-(anthracene-9,10-diyl)dibenzoic acid dimethylformamide disolvate, C₂₈H₁₈O₄·2C₃H₇NO or [(abdH₂)(DMF)₂], at low concentrations of zinc. Meanwhile, at higher zinc concentrations, the abdH₂ ligand gives rise to the nonporous one-dimensional coordination polymer catena-poly[[bis(dimethylformamide-κO)zinc(II)]-μ-4,4'-(anthracene-9,10-diyl)dibenzoato-κ²O:O'], [Zn(C₂₈H₁₆O₄)(C₃H₇NO)₂]_n or [Zn(abd)(DMF)₂]_n, when assembled in dimethylformamide, while a related compound is observed when N,N-dimethylacetamide (DMA) is used as the solvent, namely catena-poly[[[bis(N,N-dimethylacetamide-κO)zinc(II)]-μ-4,4'-(anthracene-9,10-diyl)dibenzoato-κ²O:O'] N,N-dimethylacetamide monosolvate], {[Zn(C₂₈H₁₆O₄)(C₄H₉NO)₂]·C₄H₉NO}_n or {[Zn(abd)(DMA)₂]·DMA}_n. Attempts to use other amide-based solvents did not give rise to any other assembled structures.

Electrical conductivity and electroluminescence of a new anthracene-based metal-organic framework with π-conjugated zigzag chains

A new three-dimensional microporous MOF has been constructed using a highly conjugated anthracene-based ligand. The rarely occurring long-range π-stacking of the ligand in the form of a zigzag chain has been found in the MOF structure, which provides not only a new charge transport pathway with high electrical conductivity of 1.3 (±0.5) × 10(-3) S cm(-1) but also an electroluminescence property with an emission centred at 575 nm.

An intermediate band dye-sensitised solar cell using triplet–triplet annihilation

A new mechanism of charge photogeneration is demonstrated for the first time, based on organic molecular structures.