Synthesis and Characterisation of Luminescent [Cr^III₂L(μ‐carboxylato)]³ Complexes with High‐Spin S=3 Ground States (L=N₆S₂ donor ligand).

Börner, Martin; Klose, Jennifer; Gutierrez Suburu, Matias E.; Strassert, Cristian A.; Yang, Fangshun; Monakhov, Kirill Yu.; Abel, Bernd; Kersting, Berthold

The synthesis, structure, magnetic, and photophysical properties of two dinuclear, luminescent, mixed‐ligand [CrIII2L(O2CR)]3 complexes (R=CH3 (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 N3Cr(μ‐SR)2(μ1,3‐O2CR)CrN3 core structure with μ1,3‐bridging carboxylate groups. A ferromagnetic superexchange interaction between the electron spins of the Cr3 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=−2JS1S2) 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 4LMCT state on the 4A2 → 2T1 (ν2) bands (λexc=405 nm). The absolute quantum yields (ΦL) for 1 and 2 were found to be strongly temperature dependent. At 77 K in frozen MeOH/CH2Cl2 glasses, ΦL=0.44±0.02 (for 1), ΦL=0.45±0.02 (for 2).

ELECTRON spin; COUPLING constants; MACROCYCLIC compounds; ELECTRON donors; LIGANDS (Chemistry); X-rays; MAGNETIC properties; CRYSTAL structure

Chemistry - A European Journal, 2021, Vol 27, Issue 60, p14899

0947-6539

Academic Journal

10.1002/chem.202102079