Recently copper(II) complexes with an aromatic nitrogen base have attracted interest as nucleoside analogues for mimicking of nucleobase pairing 1 or sensing of nucleobases. 2 Such nucleoside analogues may be utilized for creating antigene/antisense molecules, or for detecting therapeutic agents. We also synthesized some mononuclear copper(II) complexes with a tridentate ligand, 8-substitutedquinoline-2caroxylic acid, and investigated their specificity and binding affinity to nucleobases. 3

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... paper describes the synthesis and crystal structure of an 8-hydroxyquinoline-2-carboxylic acid (HQC) copper(II) complex, [Cu(HQC)(H2O)2]. The ligand HQC was synthesized from 8-hydroxyquinoline-2carbaldehyde, which was derived from 8-hydroxyquinaldine with AgO2, by oxidation using SeO2. The copper(II) complex [Cu(HQC)(H2O)2] was prepared by adding each of Cu(ClO4)2 and NaOH in aqueous solution at room temperature to HQC in ethanol. The precipitate was collected and dried over reduced pressure. Slow evaporation from a saturated aqueous solution of [Cu(HQC)(H2O)2] at room temperature gave dark-yellow needles, which are suitable for X-ray crystallography. The chemical structure of [Cu(HQC)(H2O)2] is shown in Fig. 1 . The data were collected using a Rigaku/MSC Mercury CCD diffractometer at 223 K. The liner absorption coefficient (µ) for Mo Kα radiation was 22.4 cm -1 . A numeral absorption correction was applied, which resulted in transmission factors ranging from 0.78 to 0.95. The data were corrected for Lorentz and polarization effects. A structure determination was carried out using the program SIR92. 4 All of the non-hydrogen atoms were refined anisotoropically. The positions of the hydrogen atoms were determined from a difference Fourier map and were refined isotropically. All calculations were performed using the teXsan program package. 5 Crystal and experimental data are listed in Table 1 . The structure of the complex is shown in Fig. 2 . The final positional parameters for all non-hydrogen atoms are given in Table 2 , and selected bond lengths and bond angles are summarized in Table 3 . The crystal structure of [Cu(HQC)(H2O)2] consists of mononuclear units in which each copper atom is coordinated by x115 ANALYTICAL SCIENCES 2005, VOL. 21 X-ray Structure Analysis Online A copper(II) complex with 8-hydroxyquinoline-2-carboxylic acid was synthesized and its crystal structure was determined by X-ray crystallography. 8-Hydroxyquinoline-2-carboxylic acid acted as a dibasic tridentate ligand to form a neutral mononuclear complex with a distorted square-pyramidal geometry with two water molecules.