Strain Alleviation in an Isomorphous Series of Lanthanide 2-Nitroterephthalates [Ln2(TPNO2)3(H2O)2]·2H2O (Ln = Pr – Lu, except Pm)
Inorganica Chimica Acta
f-Elements, Metal organic frameworks, Lanthanide contraction, Hydrothermal synthesis, Thermogravimetric analysis
An extended series of trivalent lanthanide 2-nitroterephthalates, [Ln2(TPNO2)3(H2O)2]·2H2O, (Ln = Pr through Lu, except Pm) were synthesized hydrothermally from Ln2O3 and 2-nitroterephthalic acid (H2TPNO2) at 170 °C in Teflon lined Parr steel autoclaves, and were characterized via single crystal X-ray diffraction, powder X-ray diffraction, FT-IR spectroscopy, elemental analyses, and thermogravimetric analyses.
All [Ln2(TPNO2)3(H2O)2]·2H2O coordination polymers are isomorphous, crystallizing in the monoclinic crystal system with space group C2/c. The metal centers in all networks possess the coordination number 8, while forming a three-dimensional extended lattice. Two metal centers form Ln2O14 entities, comprising crystallographically identical LnO8 polyhedra, connected via edge-sharing, utilizing two carboxylate O-atoms. These Ln2O14 units are separated along the a- and b-axes by individual 2-nitroterephthalate linkers, while being closely connected along the c-axis via two carboxylate groups on each side.
Compared to small inorganic anions, the rather flexible 2-nitroterephthalate seems to allow for the unobstructed decrease in size of the LnO8 polyhedra as Ln3+ ionic radii decrease towards the heavier Ln elements. Hence, the structural parameters of the crystal lattice adjust gradually without noticeable strain buildup along the series resulting in isomorphous arrangements for all networks. The thermogravimetric and FT-IR measurements seem to confirm the structural features.
Zehnder, R. A., Fontaine, N., Mouawad, B. A., Leonard, J. K., Zeller, M., Fronczek, F. R., de Lill, D. T., Ballard, A., Bonnette, D., Head, A., Ghimire, K., Welch, J. N., Barber, E. R., Murray, J. M., Dempsey, C., Jenkins, J., Jackson, G., Tokunboh, M., Bach, S. R., & Treadway Harris, J. A. (2017). Strain Alleviation in an Isomorphous Series of Lanthanide 2-Nitroterephthalates [Ln2(TPNO2)3(H2O)2]·2H2O (Ln = Pr – Lu, except Pm). Inorganica Chimica Acta, 467, 276 - 286. https://doi.org/10.1016/j.ica.2017.08.030. Retrieved from https://nsuworks.nova.edu/cnso_chemphys_facarticles/250