meta ‐Phosphonobenzoic Acid: A Rigid Heterobifunctional Precursor for the Design of Hybrid Materials

Rigid meta ‐phosphonobenzoic acid 2 possesses two functional groups (phosphonic acid and carboxylic acid) both having the aptitude to associate with a metallic precursor to form hybrid materials. The hydrothermal reactions of compound 2 with MnCl 2 · 4H 2 O or Co(NO 3 ) 2 · 6H 2 O produce, respectively, the isostructural layered materials M(H 2 O)(PO 3 C 6 H 4 CO 2 H) ( 3 , M = Mn; 4 , M = Co) characterized by the presence of the free carboxylic acid groups in the interlayer space (space group P 2 1 / n ). The reaction of Zn(CH 3 COO) 2 · 2H 2 O with 2 produces two different materials depending on the pH of the reaction media. At low pH (pH < 4.1), the isostructural material Zn(H 2 O)(PO 3 C 6 H 4 CO 2 H) ( 5 ) is formed possessing Zn II atoms octahedrally coordinated. At higher pH, generated by the addition of urea in the hydrothermal reaction, Zn 3 (H 2 O) 2 )(PO 3 C 6 H 4 CO 2 ) 2 ( 6 ) is formed (orthorhombic; space group P can). In material 6 , the phosphonic acid and the carboxylic acid groups are linked to the inorganic network. One of the two Zn II centres is tetrahedrally coordinated and the other is surrounded by a trigonal bipyramid. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)