Construction of Four Copper Coordination Polymers Derived from a Tetra-Pyridyl-Functionalized Calix[4]arene: Synthesis, Structural Diversity, and Catalytic Applications in the A³ (Aldehyde, Alkyne, and Amine) Coupling Reaction

Abstract

Solvothermal reactions of CuX2 (X = NO3, Cl, Br, I) with tetra-pyridyl-functionalized calix[4]arene at 130 °C afforded four novel coordination polymers, {[(CuNO3)2L]·MeOH}n (1), [(CuCl2)L0.5]n (2), [(Cu3Br3)L]n (3), and [(Cu3I3)L]n (4), where L = 25,26,27,28-tetra[(3-pyridylmethyl)oxy]calix[4]arene. All the products were characterized by infrared spectroscopy, thermogravimetric analysis, single-crystal X-ray diffraction, and powder X-ray diffraction. Crystal structure analysis reveals that 1 holds a one-dimensional (1D) double-chain constructed by mononuclear [Cu(NO3)] units and L linkers, while 2 features a 1D chain and its bowl-shaped L ligands work as linkers to connect the dinuclear [Cu2Cl4] units. Compounds 3 and 4 bear similar two-dimensional networks, in which each trinuclear [Cu3Br3]/[Cu3I3] unit works as a three-connecting node to connect its six equivalents by sharing L ligands. These results demonstrate that different anions have a significant effect on the final structure formation. Compounds 1–4 were employed as catalysts for the A3 coupling reaction under microwave irradiation. Notably, 3 showed the best catalytic properties for the synthesis of versatile propargylamines (yield up to 94% in only 10 min) from the A3 reaction of formaldehyde with a variety of alkynes and amines.