Release Time:2019-03-13  Hits:

Indexed by: Journal Article

Date of Publication: 2018-11-21

Journal: NEW JOURNAL OF CHEMISTRY

Included Journals: SCIE

Volume: 42

Issue: 22

Page Number: 18448-18457

ISSN: 1144-0546

Abstract: Pharmaceutically meaningful conversions like photocatalytic sulfonylation call for the precise control of the photoelectronic properties of photocatalysts. A ligand engineering strategy of inserting different numbers of thiophenes into the scaffold of triphenylamine (TPA)-based ligands was developed to improve the visible light absorption, enhance the oxidation potentials of the ground states, and decrease the reduction potentials of the excited states, providing a powerful tool for continuous modulation of the photoelectronic properties of metal-organic framework (MOF)-based heterogeneous photocatalysts. The ligand inserted with two thiophenes was found to possess a well-balanced photoelectronic performance, endowing the corresponding MOF Zn-BCTA with good visible light-harvesting ability and a moderate excited-state reduction potential with minimal over-potential for the photoinduced generation of sulfonyl radicals while avoiding the competitive over-reduction of the sulfonyl moieties. The breaking of the C-3-symmetry of the TPA-based ligand forged a distorted coordination geometry of the Zn4O nodes of the MOF to provide potential active sites to facilitate the fixation and activation of alpha, beta-unsaturated carbonyl substrates, and the two-fold interpenetrated frameworks further enhanced the spatial proximity between the encapsulated substrate and the photoredox-active centre. The synergy of the well-tuned photoelectronic properties of Zn-BCTA and the spatial confinement effect within the pores benefited the tandem sulfonylation-cyclisation of unsaturated alkenes in an efficient and diastereoselective mode for the construction of bio-interesting sulphoyl isoquinolinediones/oxindoles.