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Synthesis and Characterisation of Luminescent [Cr III 2 L( μ ‐carboxylato)] 3+ Complexes with High‐Spin S =3 Ground States (L=N 6 S 2 donor ligand)
Author(s) -
Börner Martin,
Klose Jennifer,
Gutierrez Suburu Matias E.,
Strassert Cristian A.,
Yang Fangshun,
Monakhov Kirill Yu.,
Abel Bernd,
Kersting Berthold
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.202102079
Subject(s) - superexchange , crystallography , luminescence , excited state , chemistry , ground state , carboxylate , crystal structure , electron paramagnetic resonance , ligand (biochemistry) , bridging ligand , ion , stereochemistry , atomic physics , materials science , nuclear magnetic resonance , physics , biochemistry , receptor , optoelectronics , organic chemistry
The synthesis, structure, magnetic, and photophysical properties of two dinuclear, luminescent, mixed‐ligand [Cr III 2 L(O 2 CR)] 3+ complexes (R=CH 3 ( 1 ), Ph ( 2 )) of a 24‐membered binucleating hexa‐aza‐dithiophenolate macrocycle (L) 2− are presented. X‐ray crystallographic analysis reveals an edge‐sharing bioctahedral N 3 Cr( μ ‐SR) 2 ( μ 1,3 ‐O 2 CR)CrN 3 core structure with μ 1,3 ‐bridging carboxylate groups. A ferromagnetic superexchange interaction between the electron spins of the Cr 3+ ions leads to a high‐spin ( S =3) ground state. The coupling constants ( J =+24.2(1) cm −1 ( 1 ), +34.8(4) cm −1 ( 2 ), H=−2 J S 1 S 2 ) are significantly larger than in related bis ‐ μ ‐alkoxido‐ μ ‐carboxylato structures. DFT calculations performed on both complexes reproduce both the sign and strength of the exchange interactions found experimentally. Frozen methanol‐dichloromethane 1 : 1 solutions of 1 and 2 luminesce at 750 nm when excited into the 4 LMCT state on the 4 A 2 → 2 T 1 (ν 2 ) bands (λ exc =405 nm). The absolute quantum yields ( Φ L ) for 1 and 2 were found to be strongly temperature dependent. At 77 K in frozen MeOH/CH 2 Cl 2 glasses, Φ L =0.44±0.02 (for 1 ), Φ L =0.45±0.02 (for 2 ).