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 [NiIIL1⊂(H2O)] (1) and [2 × 1+1 × 2] cocrystals [{NiIIL1MII(H2O)3}{NiIIL1}2](ClO4)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) (H2L1) have been described in this investigation. Compound 1 is an inclusion product in which the water molecule is encapsulated in the O4 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 [NiIIL1MII(H2O)3]2+ cation and two mononuclear [NiIIL1] moieties. Among three coordinated water molecules of the dinuclear cores in 2–6, two are encapsulated in the O4 cavity of two mononuclear [NiIIL1] 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 O4 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 O4 cavity. For the NiII3CuII (2) and NiII3FeII (5) compounds, metal substitution takes place in solution, resulting in the formation of [CuIIL1Na]+ and [{CuIIL1}2Na]+ for 2 and [1 × 1+1 × 1] species [{NiIIL1}·{FeIIIL1}]+ for 5.