Spin Cross-Over (SCO) Complex Based on Unsymmetrical Functionalized Triazacyclononane Ligand: Structural Characterization and Magnetic Properties

Abstract : The unsymmetrical ligand 1-(2-aminophenyl)-4,7-bis(pyridin-2-ylmethyl)-1,4,7-triazacyclononane (L6) has been prepared and characterized by NMR spectroscopy. The L6 ligand is based on the triazamacrocycle (tacn) ring that is functionalized by two flexible 2-pyridylmethyl and one rigid 2-aminophenyl groups. Reaction of this ligand with Fe(ClO4)2·xH2O led to the complex [Fe(L6)](ClO4)2 (1), which was characterized as the first Fe(II) complex based on the unsymmetrical N-functionalized tacn ligand. The crystal structure revealed a discrete monomeric [FeL6]2+ entity in which the unsymmetrical N-functionalized triazacyclononane molecule (L6) acts as hexadentate ligand. As observed in the few parent examples that are based on the symmetrical N-functionalized tacn ligands, the triazacyclononane ring is facially coordinated and the N-donor atoms of the three functional groups (two pyridine and one aniline groups) are disposed in the same side of the tacn ring, leading to a distorted FeN6 environment. The magnetic studies of 1 revealed the presence of an incomplete spin crossover (SCO) transition above 425 K, whose progress would be prevented by a very exothermic thermal decomposition at ca. 472 K, as shown by thermogravimetric and DSC measurements
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Submitted on : Tuesday, March 12, 2019 - 2:46:12 PM
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Merzouk Halit, Mélissa Roger, Véronique Patinec, Said Yefsah, Carlos Gomez-Garcia, et al.. Spin Cross-Over (SCO) Complex Based on Unsymmetrical Functionalized Triazacyclononane Ligand: Structural Characterization and Magnetic Properties. Magnetochemistry, MDPI, 2019, 5 (1), pp.19. ⟨10.3390/magnetochemistry5010019⟩. ⟨hal-02065175⟩

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