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

Abstract

Ten isostructural single-crystal diffraction studies of mixed cation Ca/Sr salt forms of the salicylate anion are presented, namely catena-poly[[diaquacalcium(II)/strontium(II)]-bis(μ-2-hydroxybenzoato)], [CaSr(CHO)(HO)], 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, namely catena-poly[[diaquastrontium(II)/barium(II)]-bis(μ-2-hydroxybenzoato)], [SrBa(CHO)(HO)], 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 counter-ion salt forms leads to systematic structural changes and allows solubility to be tuned to values between those for the pure Ca and Sr species.

Crystal structures of three halide salts of L-asparagine: an isostructural series

“…This means, for example, that it is not currently possible to predict which salt form of an active pharmaceutical ingredient (API) will be the most soluble or have the best compaction properties. In this area, isostructural series of structures are especially interesting as they allow changes in properties to be related to changes in intermolecular interaction strength or type without the complication of changes to the overall gross structure (Galcera & Molins, 2009;Allan et al, 2018). Here we present the structures of three isostructural halide salts of l-asparagine, namely ISSN 2056-9890 the monohydrates [HAsp][Cl]ÁH 2 O, (I), [HAsp][Br]ÁH 2 O, (II) and [HAsp][I]ÁH 2 O, (III), (HAsp = C 4 H 9 N 2 O 3 cation).…”

1D and 2D Coordination Polymers of Calcium with Nonsteroidal Anti‐Inflammatory Drugs: Synthesis, Crystal Structures, Hirshfeld Surfaces, Antimicrobial and Antioxidant Activities

“…[4,[9][10][11][12][13][14] However, significantly less attention has been paid to CPs based on the alkaline-earth metal ions. [2,7,[15][16][17][18] These metal ions play a crucial role in numerous biological pathways such as cellular diversity, partition, apoptosis, homeostasis, adjusting electrolyte balances, pH, and nerve impulses. [19,20] Additionally, they have an advantage over transition or lanthanide metal ions because most of the sblock cations are non-toxic, relatively cheap, and soluble in aqueous media.…”

“…At present, most of the coordination polymers reported in the literature involve the d‐block transition metal ions [4,9–14] . However, significantly less attention has been paid to CPs based on the alkaline‐earth metal ions [2,7,15–18] . These metal ions play a crucial role in numerous biological pathways such as cellular diversity, partition, apoptosis, homeostasis, adjusting electrolyte balances, pH, and nerve impulses [19,20] .…”