Oxidation state variation in bis-catix[4]arene supported decametallic Mn clusters

The reaction of MnCl2 center dot 4H(2)O, H8L(2,2'-bis-p-Bu-t-calix[4]arene) and NEt3 in a dmf/MeOH solvent mixture results in the formation of a mixed valent decametallic cluster of formula [(Mn6Mn4III)-Mn-II(L)(2)(mu(3)-OH)(4)(mu-OH)(4)(MeOH)(4)(dmf)(4)(MeCN)(2)]center dot MeCN (3). Complex 3 crystallises in the monoclinic space group P2(1)/n with the asymmetric unit comprising half of the compound. Structure solution reveals that the bis-calix[4] arene ligands are arranged such that one TBC[4] moiety in each has undergone inversion in order to accommodate a ((Mn4Mn6II)-Mn-III) metallic skeleton that describes three vertex-sharing [(Mn2Mn2II)-Mn-III] butterflies. The structure is closely related to the species [(Mn6Mn4II)-Mn-III(L)(2)(mu(3)-O)(2)(mu(3)-OH)(2)(mu-OMe)(4)(H2O)(4)(dmf)(8)]center dot 4dmf (4), the major difference being the oxidation level of the Mn ions in the core of the compound. DFT calculations on the full structures reveal that replacing the Mn-III ions in 4 for Mn-II ions in 3 results in a significant decrease in the magnitude of some antiferromagnetic exchange contributions, a switch from ferromagnetic to antiferromagnetic in others, and the loss of significant spin frustration.

Automated summary

The reaction results in the formation of a mixed valent decametallic cluster with a complex structure. The ligands are arranged to accommodate the metallic skeleton, resulting in significant changes in the magnetic properties of the compound.