New symmetrical binucleating ligands N,N-bis[2-hydroxy-5-methyl-3-(4-methyl-piperazinomethyl)benzyl]-alkylamines L1 and L2 and their copper(II) complexes [Cu2L(X)2]·2H2O, where X = CH3COO？, C6H5COO？, Cl？, and , were prepared and characterised. All the complexes undergo quasi-reversible reduction at negative potential (E = ？0.48 to ？1.02？V). The acetate and benzoate complexes undergo a two-step single electron transfer at –0.48 to –0.60？V and ？0.9 to ？1.02？V. The chloro and perchlorate complexes undergo a single step two-electron transfer at ？0.55 to ？0.75？V. Variable temperature magnetic studies show the presence of weak exchange interaction for acetate (？2？J around 25 to 40？cm？1) and benzoate (？2？J around 45 to 55？cm？1) bridged complexes and no exchange interaction is found for chloro and perchlorate complexes. ESR spectra of chloro and perchlorate complexes are like mononuclear copper(II) complexes with hyperfine splitting (A = 165 ± 5, = 2.17–2.23, and = 2.05–2.10). The ESR spectra of acetate and benzoate complexes are like binuclear copper(II) complexes with broad signal ( = 2.2). 1. Introduction Interest in the synthesis of new binucleating ligands with different donor atoms and flexibility [1–6] attracts the attention of several coordination chemists, because complexes prepared using these ligands emerge with peculiar chemical behaviours mainly due to their application in bioinorganic chemistry, magnetochemistry, electrochemistry, and homogeneous catalysis. This interest has arisen because such ligands can accommodate two metal centers and thus may provide the basis of models for the active sites of biological systems. Several bi- and polynuclear copper containing proteins have been identified such as hemocyanin, tyrosinase, catechol oxidases, ceruloplasmin, laccase, and ascorbate oxidase [7–15]. Understanding the functional and structural properties of binuclear active site by developing small dicopper complexes as models for these metalloproteins is the main aim of the bioinorganic chemist. In physicochemical aspects, these dicopper complexes have noteworthy significance as new inorganic materials capable of showing peculiar magnetic and redox properties and hence these dinuclear copper(II) complexes have wealthy applications in magnetochemistry and homogeneous catalysis [16–20]. In our laboratory we are dealing with binucleating ligands and their metal complexes for more than one decade. So far we have synthesised series of binucleating ligands with phenolic and piperazinyl donor atoms [21–29]. The magnetic and ESR spectral behaviours of the
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