Synthesis, photoluminescence and thermodynamics of two lanthanide coordination polymers with 5-nitroisophthalate

Two lanthanide-based metal-organic frameworks, [Tb-2(5-nip)(3)(H2O)(5)center dot 5H(2)O](n)(1), and [Eu-3(5 nip)(4)(5 Hnip) (H2O)(7)center dot 9H(2)O](n) (2) (5-H-2 nip = 5-nitroisophthalic acid), have been synthesized and structurally characterized. 1 features a unique 3D network with two distinct paddlewheel building blocks. 2 displays a 3D supramolecular framework with 1D channels occupied by free water molecules. Solid-state photoluminescence studies indicate that both the compounds 1 and 2 exhibit characteristic luminescence emission bands of the corresponding lanthanide ions in the visible region at room temperature. TG-DSC curves show that the dehydrated products of the title compounds exhibit high stability up to 400 degrees C. The enthalpy changes of liquid-phase reaction of formation for 1 and 2, Delta H-r(m)theta(l), were determined at 298.15 K by a microcalorimeter to be (10.7 +/- 0.1) kJ mol(-1) and (30.6 +/- 0.1) kJ mol(-1), respectively. Based on a designed thermochemical cycle, that of solid-phase reaction of formation and the standard molar enthalpy of formation for 1, Delta H-r(m)theta(s) and Delta H-f(m)theta, were calculated to be (16.9 +/- 0.6) kJ.mol(-1) and -(3103.2 +/- 15.3) kJ mol(-1), respectively. Those for 2 were (119.4 +/- 0.8)10 mol(-1) and -(4510.2 +/- 17.4) kJ mol(-1), respectively. Combining the thermochemical data of the reactions and kinetic equations with the data of thermokinetic experiments, the fundamental thermodynamic and kinetic parameters were also achieved.