Abstract
Four different carboxylato bridges have been efficiently utilized for growth of three tetranuclear nickel(II) complexes [Ni4(μ3-H2L)2(μ3-OH)2(μ1,3-CH3CO2)2](ClO4)2 (1), [Ni4(μ3-H2L)2(μ3-OH)2(μ1,3-C2H5CO2)2](ClO4)2·1/2H2O (2), and [Ni4(μ3-H2L)2(μ3-OH)2(μ1,3-O2C-C6H4-pNO2)2](ClO4)(p-NO2-C6H4-CO2)·DMF·5H2O (3) and one dinuclear nickel(II)-based chain complex {[Ni2(μ-H2L)(μ1,3-O2CCH2Ph)2(H2O)](ClO4)·1/2(CH3OH)}n (4). These were obtained via the reaction of Ni(ClO4)2·6H2O with H3L [2,6-bis((2-(2-hydroxyethylamino)ethylimino)methyl)-4-methylphenol] and RCO2Na (R = CH3,C2H5, p-NO2C6H4, and PhCH2). This family of complexes is developed from {Ni2(μ-H2L)}3+ fragments following self-aggregation. The complexes were characterized by X-ray crystallography and magnetic measurements. The changes from acetate, propionate, and p-nitrobenzoate to phenylacetate groups resulted in two different types of coordination aggregation. These compounds are new examples of [Ni4] and [Ni2]n complexes where organization of the building motifs are guided by the type of the carboxylate groups responsible for in-situ generation and utilization of HO- bridges with alteration in the aggregation process within the same ligand environment. Studies on the magnetic behavior of the compounds reveal that the exchange coupling within 1-4 is predominantly antiferromagnetic in nature.
Highlights
Recent intense interest in the synthesis and characterization of high-nuclearity coordination cluster complexes of 3d metal ions is driven by a variety of reasons, such as their relevance to biologically significant structural motifs and to add new members to the ever growing family of magnetic materials.[1]Incorporation of nickel(II) ions within these from the coordination support of phenol-based ligands has been receiving increasing attention in recent years in the field of molecular magnetism and electronics.[2]
Hydroxyethylamino)ethylimino}methyl]-4-methylphenol with nickel(II) perchlorate and aggregation propensity of the fragments formed have been studied in this work
The use of acetate, propionate, and pnitrobenzoate to phenylacetate groups in the reaction medium resulted in two distinct courses of aggregation reactions
Summary
Recent intense interest in the synthesis and characterization of high-nuclearity coordination cluster complexes of 3d metal ions is driven by a variety of reasons, such as their relevance to biologically significant structural motifs and to add new members to the ever growing family of magnetic materials.[1]. Hydroxyethylamino)ethylimino)methyl)-4-methylphenol (H3L) was prepared (Scheme S3) following a modified literature procedure,[15] and its reaction with nickel(II) perchlorate has been examined The suitability of this ligand has been explored for the synthesis of multimetallic complexes. The reaction of Ni(ClO4)2·6H2O with H3L and the respective carboxylate salts of sodium in a 2:1:1 molar ratio in MeOH led to the formation of 2 as green crystals and 3 as green powder from the reaction mixture in 66% and 42% yields. Intramolecular hydrogen-bonding interactions further stabilize the weak interdinuclear link formed from alcoholic HO− coordination (Figure S7) Both the nickel(II)-bound −OH group (O2) and the dangling −OH arm (O3) within the. The presence of a monocationic {Ni2} fragment [Ni2(H2L)(ClO4)(O2CC2H5)]+ (C20H32ClN4Ni2O9) in solution phase, characteristic for bound C2H5CO2−, originating from 2 is confirmed by a medium-intensity peak at m/z = 623.10 (calcd 623.05). Due to the model employed, the intermolecular interaction is larger than expected, because it takes into account intrachain interactions between dinuclear units, as well as any possible interchain interactions and any decrease in χMT caused by zfs
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