Synthesis of Ester-Functionalized Vanadyl Phosphonates

New layered vanadyl organophosphonates VOHOOC(CH 2 ) 2 PO 3 ·2H 2 O and VO(O 3 PR) 1 - x (O 3 PR‘) x · y H 2 O with R being the ester function (CH 2 ) 2 COO(CH 2 ) n - 1 CH 3 and R‘ the ethylcarboxylic function (CH 2 ) 2 COOH 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(CH 2 ) 2 PO(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(CH 2 ) 2 PO(OH) 2, nothing happens with HOOCCH 2 PO(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.