Sheets of Tetranuclear Ni(II) [2 × 2] Square Grids Structure with Infinite Orthogonal Two-Dimensional Water–Chlorine Chains

Abstract

The tetranuclear nickel(II) complex [Ni 4 (HL) 4 ]Cl 4 ·4H 2 O {H 2 L = 1,5-bis[1-(pyridin-2-yl)ethylidene]carbono hydrazone} has been prepared by reaction in methanol of nickel(II) chloride and H 2 L in 2:1, M:L molar ratio. The single crystal Xray diffraction analysis revealed a 2 × 2 square grid of tetramer units with the metal ions joined in pairs by the alkoxide oxygen atom in the μ 2 mode with octahedral geometry around each nickel ion. The supramolecular structure shows that the tetramer units are linked through edge-to-face (T shape) C−H···π interactions, forming sheets with hydrophobic-(occupied by infinite 2D water−chlorine chains) and hydrophilic-(occupied by chlorine anions) channels. Variable temperature magnetic studies suggest an antiferromagnetic coupling between the adjacent Ni(II) centers with a coupling constant of J = −6.6 cm −1 .T he binding of transition metal ions to properly designed multifunctional organic ligands for the construction of original metallosupramolecular architectures 1 continue to attract scientific attention for several reasons, such as magnetic, electronic, catalytic, or biological properties. 2 For example, the packing of some compounds can give rise to diverse nature channels, similar to those present in natural proteins as aquaporins involved in water transport. 3 It might seem that hydrophobic channels should repel water; however, they can be hydrated and their nature promoted rapid water flow. 4 It is well-known that if discrete metallo-supramolecular species contain additional peripheral binding sites, they can assemble to give polymeric structures. 5 Similarly, aggregation to give polymers can be supported by additional bridging ligands 6 or counterions. 7 A knowledge of the principles of structure formation through polymerization is important not only from the viewpoint of coordination chemistry but also for the future development of increasingly intricate and functional coordination networks. In this sense, noncovalent interactions such as hydrogen bonds and π,π-stacking are the main driving forces behind this self-assembly process. 8 One of the main targets in this field is the design and synthesis of new polytopic ligands that can be used for synthesis of molecular metal grids. Thompson and cowokers have successfully produced many tetranuclear [n × n] grids using directed self-assembly polydentate ligands with transition metal ions. 9 They have synthesized tetranuclear complexes using templated cyclization methods, where the bridging arrays among the metal ions involve oxygen donor atoms. 10 In this way, self-assembly of transition metal ions with designed Schiff bases allow for the synthesis of stable metal complexes with interest and potential applications in many fields. 11 On the other hand, owing to its ability to adopt various geometries, the coordination chemistry of nickel(II) ions was widely explored in this past decade 12 and complexes with esthetical architectures were synthesized. 13 The use of the nickel compounds in development of new magnetic ...

Synthesis, Spectroscopic Studies and X-Ray Diffraction of Heptacoordinated Mn(II) and Co(II) Complexes with Ligands Derived from Carbonohydrazide

“…In the literature, dinuclear compounds of manganese or cobalt which exhibit ferromagnetic or antiferromagnetic interactions are largely reported [34] [35] [36]. In recent years, we have prepared different symmetrical Schiff base types from the condensation of carbono or thiocarbono hydrazide and aldehydes or ketones which are subsequently used to prepare dinuclear or tetranuclear metal complexes [37] [38] [39]. In the absence of any particular precautions, the reaction which is a nucleophilic addition of the primary amine on the carbonyl group, proceeds on both arms of the carbonohydrazide.…”

Vanadium(V) Complexes with Substituted 1,5-bis(2-hydroxybenzaldehyde)carbohydrazones and Their Use As Catalyst Precursors in Oxidation of Cyclohexane

“…Recently, some of them, containing two binding moieties (provided by oxalic, malonic, adipic, or terephthalic central fragments) have been used for the synthesis of dinuclear − and polymeric vanadium­(V) species with high catalytic activity in oxidation of alkanes. Ditopic ligands based on the carbohydrazide fragment linked with pyridine, carboxylate, and oxime functional groups display coordination versatility and lead to various structural motifs. − The polydentate Schiff base ligand 1,5-bis­(salicylidene)­carbohydrazide (H 4 L) that resulted from a condensation reaction between 2-hydroxybenzaldehyde and carbohydrazide provides two different binding sites, ONN and ONO, to accommodate metal ions. Thus, dioxidomolybdenum­(VI), diorganotin­(IV), nickel­(II), and copper­(II) complexes have been reported. − In all of these compounds, the ligand acts as a trianion, in contrast to its thioanalogue, which also can be stabilized in metal complexes as a tetraanion …”

Synthesis, Crystal Structure Determination and Magnetic Study of a New [2 × 2] Grid Tetranuclear Fe(II) and Ni(II) Complexes Derived from the Ligand 1, 5-Bis(1-(Pyridin-2-Yl) Ethylidene) Carbonohydrazide)

“…The , which are, respectively, assigned to  O-H,  N-H,  C=O and  C=N [30]. The bands due to the pyridine ring appear in the range 1558-1466 cm -1…”