Syntheses, Crystal Structures and Mass Spectrometry of Mononuclear NiII Inclusion Product and Self‐Assembled [2 × 1+1 × 2] NiII3MII (M = Cu, Ni, Co, Fe or Mn) Cocrystals Derived from N,N′‐Ethylenebis(3‐ethoxysalicylaldimine)

The syntheses, characterization and structures of a mononuclear nickel(II) compound [Ni II L 1 ⊂(H 2 O)] (1) and [2 × 1+1 × 2] cocrystals [{Ni II L 1 M II (H 2 O) 3 }{Ni II L 1 } 2 ](ClO 4 ) 2 [M = Cu (2), Ni (3), Co (4), Fe (5) and Mn (6)] derived from the hexadentate Schiff base compartmental ligand N,N'-ethylenebis(3-ethoxysalicylaldimine) (H 2 L 1 ) have been described in this investigation. Compound 1 is an inclusion product in which the water molecule is encapsulated in the O 4 compartment by forming bifurcated hydrogen bonds. Reactions of 1 with perchlorate salts of copper(II), nickel(II), cobalt(II), iron(II) and manganese(II) in open atmosphere produce compounds 2-6, which have similar structures. These compounds are [2 × 1+1 × 2] tetrametallic systems containing self-assembled and cocrystallized one dinuclear [Ni II L 1 M II (H 2 O) 3 ] 2+ cation and two mononuclear [Ni II L 1 ] moieties. Among three coordinated water molecules of the dinuclear cores in 2-6, two are encapsulated in the 0 4 cavity of two mononuclear [Ni II L 1 ] moieties by forming bifurcated hydrogen bonds. Evidently, the formation of inclusion product 1 and dinuclear-mononuclear cocrystals 2-6 are related to the affinity of the 0 4 compartment to encapsulate a water molecule. Electrospray ionization mass spectrometry (ESI+) spectra of compounds 1-6 have been recorded. The mass spectra of 2-6 reveal that not only the tetrametallic self-assemblies are ruptured but also the second metal ion in the dinuclear core leaves the 0 4 cavity. For the Ni II 3 Cu II (2) and Ni II 3 Fe II (5) compounds, metal substitution takes place in solution, resulting in the formation of [Cu II L 1 Na] + and [{Cu II L 1 } 2 Na] + for 2 and [1 × 1+1 × 1] spe c i es [{Ni II L 1 }·{Fe III L 1 }] + for 5. .