Mixed Ca/Sr salt forms of salicylic acid, tuning structure and aqueous solubility

Pamela Allan, Jean-Baptiste Arlin, Alan R. Kennedy, Aiden Walls

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Abstract

Ten isostructural single-crystal diffraction studies of mixed cation Ca/Sr salt forms of the salicylate anion are presented, [Ca(1 − x)Srx(C7H5O3)2(OH2)2], where x = 0, 0.041, 0.083, 0.165, 0.306, 0.529, 0.632, 0.789, 0.835 and 1. The structure of an isostructural Sr/Ba species [Sr0.729Ba0.271(C7H5O3)2(OH2)2], is also described. The Ca/Sr structures form a series where, with increasing Sr content, the unit cell expands in both the crystallographic a and c directions (by 1.80 and 3.18% respectively), but contracts slightly in the b direction (−0.31%). The largest percentage structural expansion lies parallel to the direction of propagation of the one-dimensional coordination polymer that is the primary structural feature. This structural expansion is thus associated with increased M—O distances. Aqueous solubility measurements show that solubility generally increases with increasing Sr content·Thus tuning the composition of these mixed counterion salt forms leads to sytematic structural changes and allows solubility to be tuned to values between those for the pure Ca and Sr species.
Original languageEnglish
Pages (from-to)131-138
Number of pages8
JournalActa Crystallographica Section C: Structural Chemistry
VolumeC74
Issue number2
DOIs
Publication statusPublished - 28 Feb 2018

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Keywords

  • salicylic acid
  • tuning structure
  • aqueous solubility
  • s-block metal ions
  • crystalline systems
  • isostructuality

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