Poly[[tetra-aqua-(μ(3)-4-hy-droxy-pyridine-2,6-di-carboxyl-ato)di-μ(2)-oxalato-dipraseodymium(III)] 4.29-hydrate].

The coordination polymer of crystal formula [Pr(III) (2)(C(7)H(2)NO(5))(C(2)O(4))(2)(H(2)O)(4)]·4.29H(2)O or [Pr(III) (2)(HCAM)(ox)(2)(H(2)O)(4)]·4.29H(2)O was synthesized from praseodymium(III) nitrate in water using chelidamic acid (H(3)CAM) and oxalic acid (H(2)ox). There are two Pr(III) atoms in the asymmetric unit. One metal ion has nine-fold coordination from one pyridyl nitro-gen and eight oxygen atoms from one HCAM(2-), two ox(2-), and two coordinating water mol-ecules leading to the formation of a tricapped trigonal {Pr(III)NO(8)} prism. The other metal ion is coordinated by ten oxygen atoms from two HCAM(2-), two ox(2-), and two coordinating water mol-ecules, forming a bicapped square {Pr(III)O(10)} unit. The HCAM(2-) linker has a μ(2)-κ(2):κ(1) chelating coordination mode via its carboxyl-ates and N-pyridyl donors, linking the {Pr(III)NO(8)} and {Pr(III)O(10)} units into infinite chains. The μ(2)-κ(1):κ(1):κ(1):κ(1) bridging carboxyl-ates of the ox(2-) linkers connect adjacent chains into sheets in the ac plane. Adjacent layers further aggregate through inter-molecular hydrogen bonding, most of which involves the water mol-ecules of crystallization, and π-π inter-actions to form a tri-periodic supra-molecular framework. Some of the co-crystallizing water mol-ecules as well as one of the metal-coordinating water mol-ecules are disordered.