Syntheses, crystal structures and magnetic properties of [2 × 1 + 1 × 2] heterotetrametallic and [1 × 1 + 1 × 1] heterodimetallic cocrystals of copper(II) and iron(II/III)

Abstract The present work reports syntheses, crystal structures and variable-temperature magnetic properties of three copper(II)–iron(II/III) compounds [{Cu II L 1 }{Fe III L 1 (H 2 O) 2 }](ClO 4 ) ( 1 ), [{Cu II L 1 Fe II (H 2 O) 3 }{Cu II L 1 } 2 ](ClO 4 ) 2 ( 2 ) and [{Cu II L 2 Fe II (H 2 O) 3 }{Cu II L 2 } 2 ](ClO 4 ) 2 ·H 2 O·CH 3 COCH 3 ( 3 ), where H 2 L 1  =  N , N ′-ethylenebis(3-ethoxysalicylaldimine) and H 2 L 2  =  N , N ′- o -phenylenebis(3-ethoxysalicylaldimine). Compounds 2 and 3 are tetrametallic [2 × 1 + 1 × 2] cocrystals of one diphenoxo-bridged dinuclear Cu II Fe II and two mononuclear Cu II moieties, while compound 1 is a dimetallic [1 × 1 + 1 × 1] cocrystal of one mononuclear Fe III and one mononuclear Cu II moieties. The overall topology of 1 is one-dimensional. Tetrametallic (in 2 and 3 ) and one-dimensional (in 1 ) self-assemblies are generated due to weak noncovalent interactions. Variable-temperature magnetic susceptibility measurements reveal that iron(II) or iron(III) centers in 1 – 3 remain in high-spin state. Compounds 2 and 3 exhibit weak antiferromagnetic interaction; the J values in the dinuclear core are −22.5 and −13.7 cm −1 , respectively, compound 1 exhibits very weak antiferromagnetic interaction ( J  = −0.25 cm −1 ) propagated through the weak noncovalent bonds.