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Enantiopure Calcium Iminophosphonamide Complexes: Synthesis, Photoluminescence, and Catalysis
Author(s) -
Goswami Bhupendra,
Feuerstein Thomas J.,
Yadav Ravi,
Köppe Ralf,
Lebedkin Sergei,
Kappes Manfred M.,
Roesky Peter W.
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202004833
Subject(s) - enantiopure drug , homoleptic , chemistry , fluorescence , catalysis , calcium , photoluminescence , medicinal chemistry , stereochemistry , enantioselective synthesis , organic chemistry , materials science , physics , optoelectronics , quantum mechanics , metal
The synthesis of calcium complexes ligated by three different chiral iminophosphonamide ligands, L‐ H ( L =[Ph 2 P{N( R )CH(CH 3 )Ph} 2 ]), L′ ‐H ( L′ =[Ph 2 P{NDipp}{N( R )CH(CH 3 )Ph}]), (Dipp=2,6‐ i Pr 2 C 6 H 3 ), and L′′ ‐H ( L′′ =[Ph 2 P{N( R )CH(CH 3 )naph} 2 ]), (naph=naphthyl) is presented. The resulting structures [ L 2 Ca], [ L′ 2 Ca], and [ L′′ 2 Ca] represent the first examples of enantiopure homoleptic calcium complexes based on this type of ligands. The calcium complexes show blue–green photoluminescence (PL) in the solid state, which is especially bright at low temperatures. Whereas the emission of [ L′′ 2 Ca] is assigned to the fluorescence of naphthyl groups, the PL of [ L 2 Ca] and [ L′ 2 Ca] is contributed by long‐lived phosphorescence and thermally activated delayed fluorescence (TADF), with a strong variation of the PL lifetimes over the temperature range of 5–295 K. Furthermore, an excellent catalytic activity was found for these complexes in hydroboration of ketones at room temperature, although no enantioselectivity was achieved.