Synthesis of Ester-Functionalized Vanadyl Phosphonates

Abstract

New layered vanadyl organophosphonates VOHOOC(CH2)2PO3·2H2O and VO(O3PR)1-x(O3PR‘)x·yH2O with R being the ester function (CH2)2COO(CH2)n-1CH3 and R‘ the ethylcarboxylic function (CH2)2COOH were prepared. Two different synthesis routes were used; the first compound is obtained in a water−acetone mixture with vanadyl acetylacetonate and 2-carboxyethylphosphonic acid [HOOC(CH2)2PO(OH)2], while the latter are prepared from the same phosphonic acid by reaction of vanadium pentoxide in an alcohol medium. These compounds were characterized by X-ray diffraction, IR spectrosopy, and thermal analysis. EXAFS experiments and magnetic measurements were also performed. The interlayer distance of esterified compounds increases as the alkyl chain length n increases. For the same value of n, the compounds esterified with alkanediols display shorter interlayer distances than those prepared from alkanols. This results from a pillaring process: both alcohol functions of the alkanediols react with the carboxylic functions of two adjacent layers. On the other hand, while the esterification reaction is observed with HOOC(CH2)2PO(OH)2, nothing happens with HOOCCH2PO(OH)2 (Sabbar, E.; de Roy, M. E.; Besse, J. P. Ann. Chim. Sci. Mater. 1998, 23, 341). As already observed elsewhere, the accessibility of the carboxylic function depends on the alkyl chain length of the vanadyl carboxy n-alkylphosphonate.