Coordination Algorithms Control Molecular Architecture: [Cu I 4 (L2) 4 ] 4+ Grid Complex Versus [M II 2 (L2) 2 X 4 ] y+ Side‐By‐Side Complexes (M=Mn, Co, Ni, Zn; X=Solvent or Anion) and [Fe II (L2) 3 ][Cl 3 Fe III OFe III Cl 3 ]

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 [2×2] grid, [Cu I 4 (L2) 4 ][PF 6 ] 4 ⋅ (CH 3 CN)(H 2 O)(CH 3 CH 2 OCH 2 CH 3 ) 0.25 ( 2⋅ (CH 3 CN)(H 2 O)(CH 3 CH 2 OCH 2 CH 3 ) 0.25 ), whereas the [Zn 2 (L2) 2 (CH 3 CN) 2 (H 2 O) 2 ][ClO 4 ] 4 ⋅ CH 3 CN ( 1⋅ CH 3 CN), [Ni II 2 (L2) 2 (CH 3 CN) 4 ][BF 4 ] 4 ⋅ (CH 3 CH 2 OCH 2 CH 3 ) 0.25 ( 5 a⋅ (CH 3 CH 2 OCH 2 CH 3 ) 0.25 ) and [Co II 2 (L2) 2 (H 2 O) 2 (CH 3 CN) 2 ][ClO 4 ] 4 ⋅ (H 2 O)(CH 3 CN) 0.5 ( 6 a⋅ (H 2 O)(CH 3 CN) 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 Cl 3 OCl 3 Fe III ] ⋅ CH 3 CN ( 7⋅ CH 3 CN). A more soluble salt of the cation of 7 , the diamagnetic complex [Fe II (L2) 3 ][BF 4 ] 2 ⋅ 2 H 2 O ( 8 ), was prepared, as well as two derivatives of 2 , [Cu I 2 (L2) 2 (NCS) 2 ] ⋅ H 2 O ( 3 ) and [Cu I 2 (L2)(NCS) 2 ] ( 4 ). The manganese complex, [Mn II 2 (L2) 2 Cl 4 ] ⋅ 3 H 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 II 2 (L2) 2 (H 2 O) 4 ][BF 4 ] 4 ( 5 b ) (fraction monomer 0.02); J =−7.6 cm −1 and g =2.44 for S = 3/2 dicobalt( II ) complex [Co II 2 (L2) 2 (H 2 O) 4 ][ClO 4 ] 4 ( 6 b ) (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⋅ H 2 O 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 Fe III OFe III species because of fitting of superimposed monomer and dimer susceptibilities arising from trace impurities. The iron( II ) centre in 7⋅ H 2 O is low spin and hence diamagnetic, a fact confirmed by the preparation and characterisation of the simple diamagnetic iron( II ) complex 8 . Mössbauer measurements at 77 K confirmed that there are two iron sites in 7⋅ H 2 O, 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.