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The influence of the counterions on the geometry of Cu(I) and Cu(II) unsubstituted phen-based (phen = 1,10-phenanthroline) complexes was investigated. The synthetic strategy used afforded the synthesis of both the tetracoordinated Cu(I) and pentacoordinated Cu(II) species with general formula [(phen)2Cu]+Y− (Y− = ClO4−, I−, SCN− and BF4−) and [(phen)2CuX]+Y− (X = Cl−, I−, NCS−, and Y− = ClO4−, I−, SCN− and BF4−), respectively. The firstly isolated Cu(I) complexes were characterized by IR, 1H NMR and UV-Vis spectroscopies, their proposed structures being confirmed by elemental analysis, atomic absorption spectroscopy (AAS) and thermogravimetric analysis (TGA). The molecular structure of Cu(II) complexes was determined by single crystal X-ray diffraction analysis. While for Cu(I) complexes, the coordinating nature of the counterions seems to have a strong influence (observed in the solid state and concentrated solution) on the flattening distortion (D2d → D2) of the geometry about the Cu(I) ion, in the Cu(II) derivatives, the size, shape, number and type of intermolecular interactions established by the counterions, drive not only the overall cations supramolecular organization, but also the molecular stereochemistry around the Cu(II) ion.

Three tetranuclear zinc(II) complexes of the general formula [ Zn 4 ( μ 3 -OH ) 2 ( LR N,N, O 1 – 3 ) 4 ( LR N,N 1 – 3 ) 2 ] (1–3) were formed from the reaction of ZnCl2 with 2 equiv. of the respective 2-pyridyl ketone oximes, HLR1−3 (R1–3 = H, Ph and Py). The synthesis and the characterization (elemental analysis, IR, 1H NMR and UV–Vis) are described. Complexes 2 and 3 were structurally characterized by single-crystal X-ray crystallography, revealing new examples of anti 12-metallocrown-4 complexes where anions such as hydroxyl groups are encapsulated into the cavity of the tetranuclear cluster.

New mononuclear palladium(II) complexes formed by with 2-hydroxy-4-(n-hexyloxybenzylidene)-4′-n-hexyaniline (HL) and 2-phenylpyridine (I), benzo[h]quinoline (II), azobenzene (III), 2-benzoylpyridine (IV) or phenyl-2-pyridylketone-2,4-dinitrophenylhydrazone (V) have been synthesized and characterized by analytical and spectroscopic methods and the single-crystal structures of [(IVa)Pd(L)] and [(Va)Pd(L)] have been established. The spectroscopic and diffractrometric data account for molecular structures wherein the palladium(II) center is part of two chelate rings involving HL and one of the I–V ligands which form a five-member N,C{[(Ia)PdL], [(IIa)Pd(L)] and [(IIIa)Pd(L)]}, a six-member N,C{[(IVa)Pd(L)]}, or a six-member N,N′{[(Va)Pd(L)]} metallacycle. The electronic spectra of [(IIIa)Pd(L)] and [(Va)Pd(L)] show an absorption maxima, at 495 (e∼3×103 M−1 cm−1) and 531 nm (e∼2×104 M−1 cm−1), respectively, which results are significantly affected by the polarity of the solvent. These chromophores should therefore be of interest for the preparation of nonlinear optical materials.

Two new dinuclear Pd(II) cyclometalated complexes of formula [L2Pd2(μ-1,2-sq)(C5H11N)2] (1) and [L2Pd2(μ-1,3-sq)(C5H11N)2]·2[(C5H12N)BF4] (1a) [HL=2,6-dimethylazobenzene], have been synthetized from a reaction of the mononuclear [LPd(acetone)2][BF4] with the piperidinium salt of squaric acid, [C5H12N]2[sq]. The single crystal X-ray analysis of complexes 1 and 1a shows that the sq ligand is found to bridge in both μ-1,2- and μ-1,3-coordination modes. These are the first examples of squarato Pd(II) complexes characterized structurally up to now.