Controllable Formation of Heterotrimetallic Coordination Compounds: Systematically Incorporating Lanthanide and Alkali Metal Ions into the Manganese 12-Metallacrown-4 Framework

Abstract

The inclusion of Ln(III) ions into the 12-MC-4 framework generates the first heterotrimetallic complexes of this molecular class. The controllable and deliberate preparations of these compounds are demonstrated through 12 crystal structures of the Ln(III)M(I)(OAc)4[12-MCMn(III)(N)shi-4](H2O)4·6DMF complex, where OAc(-) is acetate, shi(3-) is salicylhydroximate, and DMF is N,N-dimethylformamide. Compounds 1-12 have M(I) as Na(I), and Ln(III) can be Pr(III) (1), Nd(III) (2), Sm(III) (3), Eu(III) (4), Gd(III) (5), Tb(III) (6), Dy(III) (7), Ho(III) (8), Er(III) (9), Tm(III) (10), Yb(III) (11), and Y(III) (12). An example with M(I) = K(I) and Ln(III) = Dy(III) is also reported (Dy(III)K(OAc)4[12-MCMn(III)(N)shi-4](DMF)4·DMF (14)). When La(III), Ce(III), or Lu(III) is used as the Ln(III) ions to prepare the Ln(III)Na(I)(OAc)4[12-MCMn(III)(N)shi-4] complex, the compound Na2(OAc)2[12-MCMn(III)(N)shi-4](DMF)6·2DMF·1.60H2O (13) results. For compounds 1-12, the identity of the Ln(III) ion affects the 12-MCMn(III)(N)shi-4 framework as the largest Ln(III), Pr(III), causes an expansion of the 12-MCMn(III)(N)shi-4 framework as demonstrated by the largest metallacrown cavity radius (0.58 Å for 1 to 0.54 Å for 11), and the Pr(III) causes the 12-MCMn(III)(N)shi-4 framework to be the most domed structure as evident in the largest average angle about the axial coordination of the ring Mn(III) ions (103.95° for 1 to 101.69° for 11). For 14, the substitution of K(I) for Na(I) does not significantly affect the 12-MCMn(III)(N)shi-4 framework as many of the structural parameters such as the metallacrown cavity radius (0.56 Å) fall within the range of compounds 1-12. However, the use of the larger K(I) ion does cause the 12-MCMn(III)(N)shi-4 framework to become more planar as evident in a smaller average angle about the axial coordination of the ring Mn(III) ions (101.35°) compared to the analogous Dy(III)/Na(I) (7) complex (102.40°). In addition to broadening the range of structures available through the metallacrown analogy, these complexes allow for the mixing and matching of a diverse range of metals that might permit the fine-tuning of molecular properties where one day they may be exploited as magnetic materials or luminescent agents.