Lanthanide-Based Molecular Materials: Gel Medium Induced Polymorphism

The reaction of Er 3+ with polycarboxylate ligands in a gel medium frequently leads to coordination polymers that cannot be obtained via hydrothermal methods. A new Er 3+ 1,2,4,5-benzenetetracarboxylate based coordination polymer, namely, Er 4 (C 10 H 2 O 8 ) 3 (H 2 O) 12 ·12H 2 O, has been synthesized and its crystal structure is reported herein. It crystallizes in the space group P 1̄ (no. 2) with a = 10.4005(2) Å, b = 10.6486(2) Å, c = 13.6321(3) Å, α = 105.3070(7)°, β = 93.8348(8)°, γ = 108.9345(12)°, and Z = 2. To investigate the influence of the gel medium on the observed polymorphism, the Ni 2+ /1,3,5-benzenetricarboxylate system was studied, and polymorphism was also observed in this case. The crystal structure of a new Ni 2+ -containing coordination compound, namely, the Ni 3 (C 9 H 3 O 6 ) 2 (H 2 O) 14 ·4H 2 O, has been synthesized and its crystal structure is also reported. It crystallizes in the space group P 1̄ (no. 2) with a = 6.6892(9) Å, b = 10.7615(15) Å, c = 12.3163(16) Å, α = 98.907(16)°, β = 102.171(16)°, γ = 108.074(16)°, and Z = 2. Its thermal behavior has also been studied and an hydration/dehydration cycle similar to the one already observed in the Er 3+ /1,3,5-benzenetricarboxylate is described. The availability for potential industrial applications of all the reported phases is discussed.