Coordination Polymers of 1,3,5-Tris(triazol-1-ylmethyl)-2,4,6-trimethylbenzene: Synthesis, Structure, Reversible Hydration, Encapsulation, and Catalysis Oxidation of Diphenylcarbonohydrazide

Abstract

Eight coordination polymers {[Co3(L)2(H2O)6Cl6]·4H2O}n (1), {[Co(L)2Cl2]·13H2O}n (2), {[Cu3(L)2(H2O)6Cl6]·4H2O}n (3), {[Cu(L)2Cl2]·12H2O}n (4), {[Zn(L)2(H2O)2](NO3)2·4H2O}n (5), {[Zn(L)2(H2O)2](PF6)2·6H2O}n (6), {[ZnL(mal)]·3H2O}n (7), and {[Zn3(L)2(fum)3(H2O)6]·2H2O}n (8) were synthesized by reactions of the flexible tripodal ligand 1,3,5-tris(triazol-1-ylmethyl)-2,4,6-trimethylbenzene (L) and/or fumaric acid (H2fum)/malonic acid (H2mal), with corresponding metal salts, respectively. The structures of these polymers were established by elemental analysis, IR, powder and single-crystal X-ray diffraction analysis. Complexes 1 and 3 had an infinite two-dimensional (2D) honeycomb network. L as a cis-tridentate ligand coordinated to metal ions up and down alternatively. Complexes 2 and 4 possessed a one-dimensional (1D) chain hinged structure. L was a cis-bidentate ligand. Complexes 5 and 6 had a 2D network structure with (4,4) topology. L was a trans-bidentate ligand in 5, while in 6, L adopted a cis-configuration coordinated to metal ion bidentately. Complex 7 had a wavy 2D structure. L adopted a trans-configuration coordinated ion in the c-direction, while the malonate anion coordinated to metal ions in the b-direction in left- and right-helix alternatively. Complex 8 had an unusual 2D to three-dimensional (3D) interpenetration network structure. L was in trans-configuration coordinated to metal ions tridentately in the bc plane to form a ladder structure, and fumarate anion bridged the ladder in the a-axis to form a porous 2D coordination polymer. Adjacent 2D coordination polymers penetrated each other in the c-direction to form a 3D coordination with void dimensions consisting of 11 Å rhombic channels. The structures of 1 and 2 (or 3 and 4) indicate ligand/metal ratios had a significant influence on the structures of coordination polymers. The distinct structures of all these complexes demonstrated that the counteranions played an important role in the construction of coordination polymers. The isostructure between complexes 1 and 3, 2 and 4, and 5 indicate that the metal centers did not affect the structure of the complexes. Complex 8 with the characteristic of hydrophilic carboxylate groups and hydrophobic L was capable of absorbing water reversibly under 50 °C and encapsulating guest molecules, such as curcumin, diphenylcarbonohydrazide, and phenylfluorone, to form {(guest molecule)x ⊂ 8}n. (where x = 0.2–0.4). The encapsulation behavior of 8 had been studied by elemental analysis, IR, thermogravimetric analysis (TG), and X-ray powder diffraction patterns (PXRD). Complex 8 could heterogeneously catalyze the oxidation of diphenylcarbonohydrazide in the presence of H2O2 in ethanol effectively. The oxidation process was facile, efficient, and environmental friendly.