Synthesis, crystal structure, and porosity estimation of hydrated erbium terephthalate coordination polymers

The reaction of the Er3+ ion with polycarboxylate ligands in gel media leads to coordination polymers exhibiting various structural types and dimensionalities. Five Er3+/1,4-benzenedicarboxylate-based coordination polymers have been obtained in such conditions. Four out of the five are new. Their crystal structures are reported and compared herein. Compound 1, namely, Er2Ter3(H2O)6, where H2Ter symbolizes the terephthalic acid, crystallizes in the space group P1 (No. 2) with a = 7.8373(10) A, b = 9.5854(2) A, c = 10.6931(2) A, alpha = 68.7770(8) degrees, beta = 70.8710(8) degrees, and gamma = 75.3330(12) degrees. It has already been reported elsewhere. The last four compounds are new. Compound 2, namely, Er2Ter3(H2O)6 x 2 H2O, crystallizes in the space group P121/a1 (No. 14) with a = 6.7429(2) A, b = 22.4913(7) A, c = 9.6575(3) A, and beta = 91.6400(18) degrees. Compound 3, namely Er2Ter3(H2O)8 x 2 H2O crystallizes in the space group P1 (No. 2) with a = 7.5391(2) A, b = 10.0533(3) A, c = 10.4578(3) A, alpha = 87.7870(10) degrees, beta = 82.5510(11) degrees, and gamma = 86.2800(16) degrees. Compound 4, namely, Er2Ter3(H2O)6 x 2 H2O crystallizes in the space group C2/c (No. 15) with a = 38.5123(13) A, b = 11.1241(4) A, c = 7.0122(2) A, and beta = 98.634(2) degrees. Compound 5, namely, Er2Ter3(H2O)6 x H2O, crystallizes in the space group P1 (No. 2) with a = 6.8776(10) A, b = 11.0420(2) A, c = 18.5675(3) A, alpha = 84.7240(6) degrees, beta = 81.8380(6) degrees, and gamma = 84.1770(8) degrees. A computational method has also been developed to evaluate the potential porosity of the coordination polymers. This method is described and then applied to the different Er2Ter3(H2O)n coordination polymers previously described.