Simultaneous hydroxido-, nitrato-, and phenoxido-bridged binuclear copper Schiff base complex for green catalytic click chemistry: Synthesis, structure, Hirshfeld surface analysis, theoretical study and photoluminescence spectra

Catalytic click reactions are highly fascinating in chemical industries from several aspects like green synthesis, easy separation, nearly-perfect bond formation, etc. A new binuclear copper complex [Cu2(µ-OH)(µ-NO3)(H4L)(H2O)(NO3)]·(H2O) (where H5L = 2,2′-((1E,1′E)-((2-hydroxy-5-methyl-1,3-phenylene)bis(methanylylidene))bis(azanylylidene))bis(propane-1,3-diol)) has been used for catalytic Huisgen 1,3-dipolar cycloaddition click reaction in water. The complex has been synthesized by using a multidentate compartmental ligand and characterized by single crystal X-ray crystallography along with spectral characterizations. The structural analysis shows that this binuclear complex crystallizes in the monoclinic space group P21/c and both metal centers are bridged by a nitrate anion, a hydroxide ion, and a phenoxide group. Each discrete complex is connected by hydrogen bonding interactions to form a 3D supramolecular structure. Hirshfeld analysis and corresponding 2D fingerprint plots give a detailed information about the intermolecular interactions present in the complex. The complex also shows blue emission spectra. Density functional theory (DFT) and time dependent DFT (TDDFT) calculations have been carried out to rationalize the geometry and absorption spectrum of the complex. Afterward, the complex was used for the green catalytic click chemistry by optimizing the Huisgen 1,3-dipolar cycloaddition reaction. The complex shows high catalytic activity for copper catalyzed azide–alkyne cycloaddition (CuAAC) reaction in the aqueous phase with an average 80 % yield.