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A new synthetic approach for homo- and heteronuclear complexes, based on N,N′-bis[(3-methoxysalicylideneamino)-propyl]-piperazine (H2L) Schiff-base ligand, has been developed. The ligand has been crystallized in the form H2L·2DMSO and its structure has been solved. Using this ligand, the following complexes have been synthesized: [CoL](ClO4) (1), [Zn2L(CH3COO)2]·2H2O (2), [Cu3L2(NO3)2] (3) and [LaCu6L4(H2O)2(NO3)2](NO3)5·15H2O (4). The 1–4 complexes were characterized by elemental analysis, X-ray crystallography, infrared and diffuse reflectance spectroscopy. The crystallographic investigations revealed that H2L presents the stable chair conformation of the piperazine ring, while its coordination mode changes according to the nature of the metal ion and counterion, respectively, allowing the formation of mono- (1) and oligonuclear (2–4) complexes. Compound 1 consists of a mononuclear complex cation, where the double-deprotonated ligand (L2−) encapsulates the trivalent cobalt ion. In compound 2, L2− acts as a symmetrical binucleatig ligand through the two N2O sets disposed on each side of the piperazine ring and coordinates two zinc(II) ions. Compounds 3 and 4 contain trinuclear units where two ligand molecules coordinate unsymmetrically three CuII ions, with the N3O donor set wrapped around the peripheral CuII and the remaining NO sets bound to the central CuII ion. Two such trinuclear moieties coordinate the LaIII ion in crystal 4. Electrochemical behavior of compounds 1 and 3 and luminescent properties of compound 2 are discussed.

The behavior of 2-(2-hydroxy-benzylidene)-cyclohexan-1-one (BC) in the acidic and basic media was investigated. In acidic conditions a new dimeric structure 4′a-methoxy-2,2′,3,3′,4′,4′a,9′,9′a-octahydro-1H, 1′H-4,9′-bixanthene (XTC) was isolated. The structures of BC and XTC were confirmed by single crystal X-ray diffraction and NMR. In basic conditions, unprotonated specie (BC − ) was characterized by NMR, UV–Vis and fluorescent spectroscopy; BC could function as pH sensor.

This paper describes a new case of the bis(antipyryl-methyl)-piperazine [BAMP] ligand being in the “boat”-conformation and acting as a tetradentate. But unlike in Co(BAMP)(NCS) 2 , which is the only complex with BAMP acting as tetradentate known so far, the coordinated copper(II) is connected via a iodo-bridge to a Cu I I 2 -moiety. The synthesis, elemental analysis, spectroscopic (far- and mid-FTIR, UV–Vis) and structural characterization (X-ray diffraction) as well as magnetochemical and conductivity data of this novel mixed valence binuclear complex Cu I Cu II (BAMP)I 3 are presented.