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Keywords:

  • Lanthanides;
  • Benzene-1,3-dicarboxylic acid;
  • 2-Phenyl-1H-1,3,7,8-tetraazacyclopenta[l]phenanthrene;
  • Hydrothermal synthesis;
  • X-ray diffraction

Abstract

Reaction of the ligands 2-phenyl-1H-1,3,7,8-tetraazacyclopenta[l]phenanthrene (PTCP) and benzene-1,3-dicarboxylic acid (m-H2BDC) with Ln2O3 under hydrothermal conditions lead to three isomorphous coordination polymers [Ln2(PTCP)2(m-BDC)3·H2O]n (Ln = Tm, 1; Nd, 2; Ce, 3). The coordination polymers crystallize in monoclinic, space group P21/m with a = 9.8340(2), b = 17.9140(4), c = 15.6050(3) Å, β = 100.51(3)° for 1, with a = 9.8423(3), b = 18.3562(4), c = 15.6209(3) Å, β = 102.138(3)° for 2, and with a = 9.8620(2), b = 18.4960(4), c = 15.6530(3) Å, β = 102.42(3)° for 3, respectively. The metal ions (Ln3+) are located in an octacoordinated environment and the dinuclear [Ln2O12N4] units act as octahedral secondary building units (SBU), which are bridged in two coordination modes by six m-BDC ligands to form a three-strand-like chain. These chains are decorated by PTCP ligands and form unique three zipper-like structures, which are further assembled into three-dimensional supramolecular nets by π···π stacking interactions. Additionally, hydrogen bonds are observed in the structures. Furthermore, compounds 13 were studied by IR spectrocopy and thermogravimetric analyses.