Structure of di(salicylaldehyde benzoylhydrazonato) zinc (II), an unusual staircase polymeric structure formed via E ! Z isomerization on complexation A. Lyubchova I , N. Jouini II , A. Massat I , J. P. Doucet I , K. Boubekeur III and A. Cosse ´-Barbi * ,I I Universite ´ Denis Diderot, Institut de Topologie et Dynamique des Syste `mes, CNRS-ESA 7086, 1 rue Guy de la Brosse, Paris Cedex 05, France II Universite ´ Denis Diderot, Laboratoire de Chimie des Mate ´riaux Divise ´s et Catalyse, 2 place Jussieu, Paris Cedex 05, France III Institut des Mate ´riaux Jean Rouxel, 2 rue de la Houssinie `re, F-44322 Nantes Cedex 3, France Received July 23, 2000; accepted April 12, 2001 Abstract. A bicomplex of salicylaldehyde benzoylhydra- zone (SBH) with Zn(II) was synthesized in ethanol and single crystals were obtained in DMSO. The compound crystallizes in the orthorhombic system with the space group Pna2 1 (33) and crystal data: a ¼ 22:573ð3Þ  A, b ¼ 6:1208ð5Þ  A, c ¼ 17:881ð2Þ  A, V ¼ 2470:5ð5Þ  A 3 , Z ¼ 4, d(calc) ¼ 1.462 g  cm 3 , (2633 reflections with I > 2sðI Þ; final R ¼ 0.0509; R w ¼ 0.1099). The asymmetric unit is a nearly planar bicomplex built up from one Zn atom linked to two monodeprotonated SBH ligands. The compound can be described as formed of chains extended along the b axis. This linear polymeric character results from the linking of each asymmetric unit to two neighbouring ones via four (2  2) covalent Zn––O bonds involving three Zn atoms and four phenolic oxy- gens. These covalent bonds are related to the very unusual Z configuration of the ligand. The three-dimensional cohe- sion of the compound is obtained by van der Waals forces between the polymeric chains. Introduction Salicylaldhehyde benzoylhydrazone (SBH) belongs to a series of iron chelators prepared for iron overload che- motherapy (Ponka, Borova, Neuwirt, Fuchs & Necas, 1979; Ponka, Borova, Neuwirt & Fuchs, 1979; Ponka, Schulman & Wilzynska, 1982; Ponka, Richardson, Baker, Schulman & Edwards, 1988; Huang & Ponka, 1983; Av- ramocivi-Grisaru, Sarel, Cohen & Bauminger, 1985; Avra- mocivi-Grisaru, Sarel, Link & Hershko, 1983). Indeed, the specificity of a synthetic chelator required for iron over- load therapy is still necessary to avoid the depletion of other essential metals such as zinc, calcium, magnesium etc. ... In order to control this specificity we have under- taken the study of complex formation between SBH and these essential metals (Lyubchova, Cosse ´-Barbi, Doucet & El Hage Chahine, 1997). The title compound was pre- pared and characterized as a part of this work. In other respects, metal cations were classified as hard and soft Lewis acid –– HSAB concept (Pearson, 1963). Soft acids form unexpected complexes with Lewis bases. Therefore, it seemed interesting to study the behavior of a chelator designed as a hard and/or a borderline Lewis base towards complex formation with a borderline Lewis acid, Zn þþ . Experimental Salicylaldhehyde benzoylhydrazone was synthesized ac- cording to published procedures (Lyubchova, Cosse ´-Barbi, Doucet, Robert, Souron & Quarton, 1995). Zinc acetate (Aldrich), dimethylsulfoxide and ethanol (Merck) were pure grade reagents and were used without further purifi- cation. The complex was prepared by adding a 0.1 M SBH solution in ethanol to a zinc acetate solution with continu- ous stirring. The solution was then heated on a steam bath for 1 hour and cooled at room temperature. A yellow com- plex precipitated (yield 75%). The product was crystal- lized from ethanol and elementary analysis was performed by standard methods. The complex melted above 300  C and was insoluble in water and non-polar organic solvents, slightly soluble in polar organic ones such as tetrahydro- furane and dimethylsulfoxide. The single crystals (pale yellow parallelepipeds) were obtained in DMSO by decreasing the temperature of a sa- turated solution of the Zn complex from 343 (1) K to 338 (1) K in 144 hours. The bicomplex is neutral, two protons being lost in the complexation. IR spectra indicate that SBH has lost its amide protons and not its phenolic ones upon complexa- tion. Indeed, the n NH stretching mode near 3200 cm 1 (2470 cm 1 for the deuteriated ligand) is missing in the bicomplex spectra (Fig. 1) whereas complexation main- tains the n OH stretching normal mode near 3000 cm 1 556 Z. Kristallogr. 216 (2001) 556–559 # by Oldenbourg Wissenschaftsverlag, Mu ¨nchen * Correspondence author (e-mail: cosse@as2100.itodys.jussieu.fr) Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 5/23/15 9:14 PM