Lanthanide-based molecular alloys with hydroxyterephthalate: a versatile system

Reactions in water between lanthanide chlorides and the disodium salt of 2-hydroxyterephthalic acid (H-2-hbdc) lead to six families of lanthanide-based coordination polymers depending on the lanthanide ion and the crystal growth method. Compounds that constitute family F1 have the general chemical formula [Ln(Hhbdc)(hbdc)center dot 9H(2)O](infinity) with Ln = La-Nd and have been obtained by slow evaporation. [Ln(2)(hbdc)(3)(H2O)(6)center dot 4H(2)O](infinity) with Ln = Sm-Eu constitute family F2 and have been obtained by solvothermal synthesis. Family F3 includes compounds, obtained by a solvothermal method, with the general chemical formula [Ln(2)-(hbdc)(3)(H2O)(4)center dot 4H(2)O](infinity) with Ln = Ho-Lu plus Y and compounds obtained by slow diffusion through gels with Ln = Eu-Tb. [Ln(Hhbdc)(hbdc)(H2O)(3)center dot H2O](infinity) with Ln = Tb-Dy have been obtained by solvothermal methods and constitute family F4. [Gd-2(hbdc)(3)(H2O)(8)center dot 6H(2)O](infinity) (F5) has been obtained by slow evaporation. The last family (F6) includes compounds with the general chemical formula [Ln(2)(hbdc)(3)(H2O)(8)center dot 2H(2)O](infinity) with Ln = Nd-Tb that have been obtained by slow diffusion through gel media. Gd-Based micro-crystalline powders can be obtained by direct mixing of aqueous solutions of Gd3+ and hbdc(2-). Unexpectedly, the micro-crystalline powder belongs to F5 when the lanthanide solution is added to the ligand one and to F6 when the opposite occurs. This phenomenon is also observed for the Tb- and/or Eu-based heterolanthanide coordination polymers. Their optical properties have been studied in detail.