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Schiff-base [4]helicene Zn(ii) complexes as chiral emitters†
Mariia Savchuk,Steven Vertueux,Thomas Cauchy,Matthieu Loumaigne,Francesco Zinna,Lorenzo Di Bari,Nicolas Zigon,Narcis Avarvari
Dalton Transactions Pub Date : 07/01/2021 00:00:00 , DOI:10.1039/D1DT01752G
Abstract

The controlled preparation of chiral emissive transition metal complexes is fundamental in the field of circularly polarized luminescence (CPL) active molecular materials. For this purpose, enantiopure Zn(II) complexes 1 and 2 based on a tetradentate salen ligand surrounded by [4]helicene moieties, together with their racemic counterpart 3, have been herein synthesized. Chirality is primarily brought about by chiral 1,2-cyclohexane-diamines. Alternatively, achiral complex 4 based on ortho-phenylene-diamine has been prepared as well. Single crystal X-ray diffraction analyses have been performed on helicenic intermediates 8 and 9 and complexes 1 and 4. Complexes 1 and 4 display the typical tetradentate O,N,N,O coordination around Zn(II) characteristic of salen ligands, and bear two [4]helicene moieties. The zinc complexes are luminescent in the visible range around 560 nm at room temperature in aerated solutions with the QY reaching ca. 15% for a luminescence lifetime of 5.5 ns. The optical activities of these complexes have been assessed by CD and CPL, and compared to DFT calculations.

Graphical abstract: Schiff-base [4]helicene Zn(ii) complexes as chiral emitters
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