Structural diversity of lanthanoid salicylate hydrates

From metathesis reactions between lanthanoid salts and sodium salicylate (Na(salH)) in water, four classes of lanthanoid salicylate hydrates have been identified. Single crystal X-ray studies established a new monomeric class [Ln(salH)(3)(H2O)(3)]center dot 3H(2)O (6Ln). This new rhombohedral R3c, Z= 6 form '6Ln' has the nine coordinate metal atom on a crystallographic 3-axis, for Ln = Sm-Gd, Ho, Er, Yb, Lu, Y. We also have augmented or defined the previously known different forms, consolidating or extending their putative 'domains of existence'. The monohydrate, Ln = '1Ce', monoclinic, P2(1/n), has been re-examined at low temperature suggesting further elasticity in its formulation beyond the recently proposed '[Ln(H(2)sal) (Hsal)(sal)H2O)]((infinity vertical bar infinity))' for the Ln = Gd complex, '1Gd', one of the protonic hydrogen atoms being associated with a very short phenoxyl-O center dot center dot center dot carboxylate-O distance (2.427(3) angstrom). With refinement and the insights from a previous Ln = Eu study, suggest the protonic disposition to be around the O center dot center dot center dot O median. The 'domain of existence' for this, form embraces Ln = La (dependent on a powder diffraction study) - Gd. The tetrahydrate is manifested in two forms: triclinic, centrosymmetric binuclear [Ln(2)(salH)(6)(H2O)(4)]. 4H(2)O, P (1) over bar, Z = 1, '4Ln' recorded here in a 153 K determination, for Ln = Ho, consolidating the assignment of its domain of existence to be Ho-Er, Y, and 'polymeric mononuclear' [Ln(salH)(3)(H2O)(2)]((infinity vertical bar infinity))center dot 2H(2)O, '4Ln,' recorded here for Ln = Tb-Er, Yb, Lu, Y. The 6Gd hexahydrate shows paramagnetic f(7) magnetic behaviour. The reaction conditions leading to the isolation of a particular structural type of lanthanoid salicylate could not be reliably identified, indicating that a fine balance exists in the preferential crystallization of the lanthanoid salicylate hydrate phases. The discovery of the monomeric class has applications for the species acting as a corrosion inhibitor in dilute aqueous solution. Crown Copyright (C) 2016 Published by Elsevier Ltd. All rights reserved.