{[Ca5(C8H4O4)5(H2O)9]·8H2O}n: the first crystallographically characterized non‐transition metal salt of isophthalic acid

The reaction of CaCO₃ with isophthalic acid in water yields nona­aqua­penta‐μ‐isophthalato‐pentacalcium octahydrate, {[Ca₅(C₈H₄O₄)₅(H₂O)₉]·8H₂O}_n, a complex polymeric one‐dimensional column structure bearing metal–carboxyl­ate bonds and Ca‐bound terminal and bridging water mol­ecules, in addition to hydrogen‐bonded water mol­ecules of crystallization. The asymmetric unit comprises half of the formula unit, with one Ca²⁺ ion located on a twofold axis, and contains 16 unique strong O—H⋯O hydrogen bonds, some of which link the columns together.