Structure and magnetic behavior of a new 1-D compound with simultaneous end-on azido and carboxylato bridges. Unexpected strong ferromagnetic coupling for a Cu-N-Cu bond angle of 111.9 degrees as a consequence of ligand HOMOs countercomplementarity

The X-ray structure of the mu-carboxylate-mu(1,1)-azido-bridged compound {[Cu(Hpht)(N-3)]. H2O}(n) has been determined (Hpht = hydrogen phthalate). Crystal data: formula C8H7CuN3O5, monoclinic, P2(1)/m (No. 11), a = 7.383(3) Angstrom, b = 6.568(4) Angstrom, c = 10.659(4) Angstrom, beta = 93.38(3)degrees, Z = 2. The compound is found to be a system formed by chains of copper atoms bridged simultaneously by syn-syn carboxylato and end-on azido bridges. The copper chains are linked by a second carboxylato bridge, giving a 2-D compound. Magnetic measurements indicate strong ferromagnetic coupling, which affords a good example of unexpected magnetic properties due to the countercomplementarity of the superexchange pathways of the two ligands.