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

The inclusion of
LnIII 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 LnIIIMI(OAc)4[12-MCMnIII(N)shi-4]­(H2O)4·6DMF complex, where
OAc– is acetate, shi3‑ is salicylhydroximate,
and DMF is N,N-dimethylformamide. Compounds 1–12 have MI as NaI, and LnIII can be PrIII (1),
NdIII (2), SmIII (3), EuIII (4), GdIII (5), TbIII (6), DyIII (7), HoIII (8), ErIII (9), TmIII (10), YbIII (11), and YIII (12). An example with MI = KI and LnIII = DyIII is also
reported (DyIIIK­(OAc)4[12-MCMnIII(N)shi-4]­(DMF)4·DMF (14)). When LaIII, CeIII, or LuIII is
used as the LnIII ions to prepare the LnIIINaI(OAc)4[12-MCMnIII(N)shi-4] complex, the compound Na2(OAc)2[12-MCMnIII(N)shi-4]­(DMF)6·2DMF·1.60H2O (13) results. For compounds 1–12, the identity of the LnIII ion affects the 12-MCMnIII(N)shi-4 framework as the largest
LnIII, PrIII, causes an expansion of the 12-MCMnIII(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 PrIII causes
the 12-MCMnIII(N)shi-4 framework
to be the most domed structure as evident in the largest average angle
about the axial coordination of the ring MnIII ions (103.95°
for 1 to 101.69° for 11). For 14, the substitution of KI for NaI does
not significantly affect the 12-MCMnIII(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 KI ion does cause the 12-MCMnIII(N)shi-4 framework to become more planar as evident
in a smaller average angle about the axial coordination of the ring
MnIII ions (101.35°) compared to the analogous DyIII/NaI (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.