Macrocycle-Induced Modulation of Internuclear Interactions in Homobimetallic Complexes

A synthetic route has been developed for a series of3d homobimetallic complexes of Mn, Fe, Co, Ni, and Cu usingthree different pyridyldiimine and pyridyldialdimine macrocyclicligands with ring sizes of 18, 20, and 22 atoms. Crystallographicanalyses indicate that while the distances between the metals canbe modulated by the size of the macrocycle pocket, theflexibility inthe alkyl linkers used to construct the macrocycles enables theligand to adjust the orientation of the PD(A)I fragments inresponse to the geometry of the [M2(mu-Cl)2]2+core, particularlywith respect to Jahn-Teller distortions. Analyses by UV-visspectroscopy and SQUID magnetometry revealed deviations in theproperties [M2(mu-Cl)2]2+-containing complexes bound by standardmononucleating ligands, highlighting the ability of macrocycles touse ring size to control the magnetic interactions of pseudo-octahedral, high-spin metal centers