[(M2M3II)-M-III](n+) trigonal bipyramidal cages based on diamagnetic and paramagnetic metalloligands.

A family of five [(M2M3II)-M-III](n+) trigonal bipyramidal cages (M-III = Fe, Cr and Al; M-II = Co, Zn and Pd; n = 0 for 1-3 and n = 6 for 4-5) of formulae [Fe2Co3L6Cl6] (1), [Fe2Zn3L6Br6] (2), [Cr2Zn3L6Br6] (3), [Cr2Pd3L6(dppp)(3)](OTf)(6) (4) and [Al2Pd3L6(dppp)(3)](OTf)(6) (5) (where HL is 1-(4-pyridyl) butane-1,3-dione and dppp is 1,3-bis(diphenylphosphino) propane) are reported. Neutral cages 1-3 were synthesised using the tritopic [(ML3)-L-III] metalloligand in combination with the salts (CoCl2)-Cl-II and (ZnBr2)-Br-II, which both act as tetrahedral linkers. The assembly of the cis-protected [PdII(dppp)(OTf)(2)] with [(ML3)-L-III] afforded the anionic cages 4-5 of general formula [(M2Pd3II)-Pd-II](OTf)(6). The metallic skeleton of all cages describes a trigonal bipyramid with the MIII ions occupying the two axial sites and the M-II ions sitting in the three equatorial positions. Direct current (DC) magnetic susceptibility, magnetisation and heat capacity measurements on 1 reveal weak antiferromagnetic exchange between the Fe-III and Co-II ions. EPR spectroscopy demonstrates that the distortion imposed on the {MO6} coordination sphere of [(ML3)-L-III] by complexation in the {(M2M3II)-M-III} supramolecules results in a small, but measurable, increase of the zero field splitting at M-III. Complete active space self-consistent field (CASSCF) calculations on the three unique Co-II sites of 1 suggest D-Co approximate to -14 cm(-1) and E/D approximate to 0.1, consistent with the magnetothermal and spectroscopic data.