Investigation of the correlation between the substituent effect of ligands and the catalytic activity/magnetic properties in fine-tuned rare-earth complexes

Abstract

Amine-bis(benzothiazole phenol) ligands, C1NNBiBTHP-H2 and CLNNBiBTHP-H2 ligands, were designed for yttrium complexes with analogous structures. A series of nitrophenolate (NP)-type of ligands possessing R substituents with variable electronic properties (R = NO2, Cl, H, CH3) on ortho and/or para position attached to the phenolate rings have been selected as secondary ligands for complexes syntheses. Ten novel yttrium complexes have been synthesized, [Y(C1NNBiBTHP)(NP)(MeOH)] (1–5) and [Y(CLNNBiBTHP)(NP)(MeOH)] (6–10) where the secondary ligand NP = 2,4-dinitrophenol(1 and 6), 2,5-dinitrophenol (2 and 7), 2-nitrophenol (3 and 8), 4-chloro-2-nitrophenol (4 and 9) and 4-methyl-2-nitrophenol (5 and 10), as well as the structures and catalytic properties for lactide (LA) polymerization were both studied. All the core structures and coordination geometries for complexes 1–10 were isostructural. All complexes were demonstrated to be active catalysts for LA polymerization, and the catalytic performance for these complexes was compared. The dysprosium analogues (11, 12 with C1NNBiBTHP-H2 and 13, 14 with CLNNBiBTHP-H2) also been synthesized and the magnetic properties of these compounds are fully studied. Comparing a series of nitrophenolate co-ligands in two different ligand systems, we presented the first example to study the correlation between electronic effect of the ligands and catalytic properties for mononuclear rare-earth complexes.