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Updated: Sep 15, 2025

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Mono- to Tetra-nuclear Iron Dichloride Complexes Bearing N-(Fluoro)-aryl-Substituted Iminopyridine Ligands:
Obaid H Hashmi1, Raphael Caulier1, Frederic Capet1
1Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181, UCCS, Unité de Catalyse et Chimie du Solide, Lille F-59000, France.
Abstract:
The reaction of FeCl2 with the iminopyridine ligand containing fluorinated N-aryl groups {2-[(Ar)N = C(R)]C5H4N, where Ar = 3,5-(CF3)2C6H3 and R = H (L1) or CH3 (L3); Ar = C6F5 and R = H (L2) or CH3 (L4); and iminoquinoline 2-[(3,5-(CF3)2(C6H3)N = CH)]C9H6N (L5)} resulted in distinct iron coordination complexes whose structures were determined by single-crystal X-ray diffraction. Ligands L1 and L2 yielded mononuclear bis-ligated iron dichlorides (L1 or L2)2FeCl2 (complexes 1 and 2), while L3 and L5 formed dinuclear complexes (L3 or L5)2Fe(μ-Cl2)FeCl2 (complexes 3 and 5). Ligand L4 produced an unprecedented tetranuclear dimer [(L4)2FeCl(μ-Cl2)FeCl2]2 (complex 4). Mössbauer spectroscopy revealed single quadrupole doublets for mononuclear complex 2 and two sets of doublets for dinuclear complexes 3 and 5 and tetranuclear complex 4, confirming Fe(II) in high-spin states. Magnetic susceptibility and Curie-Weiss analyses elucidated magnetic interactions, showing reduced effective magnetic moments correlated with increasing Fe-(μ-Cl)-Fe bridges. DFT calculations and NBO analyses supported these findings, highlighting lower charge density on bridging compared to terminal chlorides. Activated by AliBu3/[CPh3][B(C6F5)4], complexes 1 and 2 showed lower activities (TOF = 1,000-1,200 h-1) than complexes 3 and 5 (TOF = 90,000 h-1) for isoprene polymerization, producing polymers with enriched cis-1,4-alt-3,4 microstructures.
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