Syntheses, Crystal Structures and Mass Spectrometry of Mononuclear Ni^II Inclusion Product and Self‐Assembled [2 × 1+1 × 2] Ni^II₃M^II (M = Cu, Ni, Co, Fe or Mn) Cocrystals Derived from <i>N</i>,<i>N′</i>‐Ethylenebis(3‐ethoxysalicylaldimine)

Abstract

Abstract 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 O 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 O 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 O 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] species [{Ni II L 1 } · {Fe III L 1 }] + for 5 .