Characterizing the Conformational Behavior of Yttrium(III) Tris-Phthalocyaninates Using Variable Temperature NMR Spectroscopyстатья
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Аннотация:We present a variable-temperature NMR study of the conformational behavior of homo- and heteroleptic yttrium(III) triple-decker complexes containing butoxy- and 15-crown-5-substituted phthalocyanine ligands Y2[(BuO)8Pc]3 and [(BuO)8Pc]Y[(BuO)8Pc]Y[(15C5)4Pc] in dichloromethane. In the homoleptic complex, the adjacent BuO-substituted ligands form gauche conformers, which undergo interconversion due to rapid rotation around the C4 axis. In contrast, in the heteroleptic complex, the inner BuO- and the outer 15C5-substituted ligands are in the staggered conformation; moreover, such an arrangement of the ligands has been shown to decrease the rotation rate of the outer BuO-substituted ligand. This allowed to find the coalescence temperature (223 K) and to determine the activation energy EA (57.7?3.4 kJ/mol) and other thermodynamic properties of the ligand rotation in the heteroleptic complex. These conclusions were supported by DFT GIAO calculations. The obtained results will be useful for further characterization of magnetic properties of paramagnetic analogues of the synthesized complexes using VT-NMR spectroscopy.