Separation of Geometric Isomers of a Dicopper Complex by Using a 19F-Labeled Ligand: Dynamics, Structures, and DFT Calculations.

Introducing a F group on two pyridines of the HLCH3 ligand (2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenol) allows the sepn. of two geometric isomers after complexation by two Cu(II) ions. Reaction of the fluorinated ligand F2-HLCH3 (F2-HLCH3 = 2,6-bis[((6-fluoro-2-pyridylmethyl)(2-pyridylmethyl)amino)methyl]-4-methylphenol) with Cu(ClO4)2·6H2O afforded the corresponding $μ$-phenoxo,$μ$-hydroxo dicopper complex [Cu2(F2-LCH3)($μ$-OH)](CLO4)2 (1) as a mixt. of isomers. Methods for isolating the isomers (1meso and 1rac) as cryst. $μ$-phenoxo,$μ$-hydroxo dicopper(II) complexes were developed. Both isomers (1meso and 1rac) were characterized by x-ray crystallog. and 19F NMR. The isomerism is detd. by the disposition of the F atoms with respect to the plane contg. the Cu2O2 core. D. functional theory calcns. using different functionals were performed to provide addnl. support for the existence of these two forms. Dissoln. of 1meso in acetone or MeCN causes its spontaneous isomerization into the 1rac form at room temp. Combined exptl. studies (UV-visible, 19F NMR) and theor. calcns. support this process. Paramagnetic 19F NMR appears as a unique and powerful probe for distinguishing the two isomers and supplying direct evidence of this isomerization process in soln. [on SciFinder(R)]


Soumis le 12 avril 2018