Coordination algorithms control molecular architecture:: [CuI4(L2)4]4+ grid complex versus [MII2(L2)2X4]y+ side-by-side complexes (M = Mn, Co, Ni, Zn; X = solvent or anion) and [FeII(L2)3][Cl3FeIIIOFeIIICl3]

The synthesis and characterisation of a pyridazine-containing two-armed grid ligand L2 (prepared from one equivalent of 3,6-diformylpyridazine and two equivalents of p-anisidine) and the resulting transition metal (Zn, Cu, Ni, Co, Fe, Mn) complexes (1-9) are reported. Single-crystal X-ray structure determinations revealed that the copper(I) complex had self-assembled as a [2 x 2] grid, [Cu-4(1)(L2)(4)][PF6](4)CH3CN)(H2O)(CH3CH2OCH3CH3)(0.25) (2 . (CH3CN)(H2O)(CH3CH2OCH2-CH3)(0.25)), whereas the [Zn-2(L2)(2)(CH3CN)(2)(H2O)(2)][ClO4](4).CH3CN(1 . CH3CN), [Ni-2(II)(L2)(2)(CH3CN)(4)][BF4](4) . (CH3CH2OCH2CH3)(0.25) (5a.(CH3CH2OCH2-CH3)(0.25)) and [Co-2(II)(L2)(2)(H2O)(2)- (CH3CN)(2)][ClO4](4) . (H2O)(CH3CN)(0.5) (6a . (H2O) (CH3CN)(0.5)) complexes adopt a side-by-side architecture; iron(II) forms a monometallic cation binding three L2 ligands, [Fe-II(L2)(3)]- [Fe-III Cl3OCl3FeIII].CH3CN (7.CH3CN). A more soluble salt of the cation of 7, the diamagnetic complex [Fe-II(L2)(3)][BF4](2).2H(2)O (8), was prepared, as well as two derivatives of 2, [CU21(L2)(2)(NCS)(2)] . H2O (3) and [Cu-2(1)(L2)(NCS)(2)] (4). The manganese complex, [Mn-2(II)(L2)(2)Cl-4].3H(2)O (9), was not structurally characterised, but is proposed to adopt a side-by-side architecture. Variable temperature magnetic susceptibility studies yielded small negative J values for the side-by-side complexes: J= -21.6 cm(-1) and g = 2.17 for S=1 dinickel(II) complex [Ni-2(II)(L2)(2)(H2O)(4)][BF4](4) (5b) (fraction monomer 0.02); J = - 7.6 cm(-1) and g = 2.44 for S=3/2 dicobalt(II) complex [CO2II(L2)(2)(H2O)(4)][ClO4](4) (6b) (fraction monomer 0.02); J = - 3.2 cm(-1) and g = 1.95 for S = 5/2 dimanganese(II) complex 9 (fraction monomer 0.02). The double salt, mixed valent iron complex 7. H2O gave J = - 75 cm(-1) and g = 1.81 for the S=5/2 diiron(III) anion (fraction monomer = 0.025). These parameters are lower than normal for Fel(III)OFe(III) species because of fitting of superimposed monomer and dimer susceptibilities arising from trace impurities. The iron(II) centre in 7 - H2O is low spin and hence diamagnetic, a fact confirmed by the preparation and characterisation of the simple diamagnetic iron(II) complex 8. Mossbauer measurements at 77 K confirmed that there are two iron sites in 7. H2O, a low-spin iron(II) site and a high-spin diiron(III) site. A full electrochemical investigation was undertaken for complexes 1, 2, 5 b, 6 b and 8 and this showed that multiple redox processes are a feature of all of them.