Effect of the apical ligand on the geometry and magnetic properties of copper(ii)/mesoxalate trinuclear units.

Three new heterometallic metal-organic frameworks, namely, {(Ph4P)(2)[MnCu3(Hmesox)(3)Br(H2O)].H2O} n (1), {(Ph4P)(2)[CoCu3(Hmesox)(3)Br]} n (2) and {(Ph4P)(2)[ZnCu3(Hmesox)(3)Br].2.5H(2)O}(n) (3) were prepared and their structure and magnetic properties were investigated (H(4)mesox = mesoxalic acid, Ph-4(P+) = tetraphenylphosphonium). The structure of all the compounds consist of two interpenetrating opposite-chirality supramolecular cationic and polymeric anionic 3-D (10,3)-a networks, which results in chiral compounds. The anionic network is formed from the polymerization of [Cu-3(Hmesox)(3)Br](4-) units, working as three connectors, and M(II) cations, working as three- connecting nodes, M = Mn(II), Co(II) and Zn(II). The Ph4P+ cations build the cationic chiral supramolecular network opposite to the anionic one. Compounds 1 and 2 exhibit long-range magnetic ordering with critical temperatures of 7.2 K and 6.9 K, respectively. However, compound 3 does not display long-range order, but shows ferromagnetic and antiferro-magnetic coupling among the Cu(II) ions. The magnetic interactions are studied by DFT calculations and compared with related Cu(II)-mesoxalate compounds previously reported.