Calixarenes and their use for sequestration of metals

The present invention relates to novel calixarenes, methods of their preparation, and uses thereof, in particular for the sequestration of metals. Disclosed are "acid-amide" calixarenes of formula (I) wherein: L is [-CH-] or [-O-CH-O-] and may be the same or different between each aryl group Ris H, halogen, or Caliphatic hydrocarbyl group, Caryl group, any of which may optionally be substituted by one or more halo or oxo groups or interrupted by one or more oxo groups, and Rmay be the same or different on each aryl group; Rcomprises an optionally protected carboxy group; two groups out of R, R, and R, are H; the one group out of R, R, and Rnot being H comprises an amide group. The amide group may be linked to a second calixarene to form a dimer. Also disclosed are methods of use of such calixarenes for the purposes of metal sequestration, especially of lanthanides and actinides. Also disclosed are calixarene dimer derivatives of the calixarenes of the invention. Also disclosed are processes for preparing the calixarenes and dimers