Magneto-Structural Studies of Copper(II) Coordination Compounds Using 1,10-Phenanthroline and 1,4-Phenylene Diacetic Acid Ligands



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The main focus of this work is on a structural and magnetic study of copper(II) centers chelated by 1,10-phenanthroline (phen) ligands and connected through 1,4-phenylene diacetate (pda) linkers to make the coordination compounds. Their structures and magnetic behavior were determined and the correlation between them was investigated. Using magnetic models based on the structure of the compounds, experimental data were fitted to calculate the coupling constants (J values). Then the coupling constants were assigned to specific CuII···CuII interactions based on the structural geometry. Seven new copper(II) coordination compounds were synthesized solvothermally. The synthesis conditions were varied to find the optimum conditions to obtain pure phases, in the highest yield, and with the best crystal quality. These copper(II) coordination compounds were characterized by single crystal X-ray diffraction. The compounds [Cu3(phen)3(pda)2(H2O) 2+]·(ClO4-)2·(H2O)4 (1), [Cu(phen)(pda)]·(H2O)2 (2), and [{Cu(OH)(phen)}4]·(ClO4)4 (3) were phase pure and further characterized using IR, Raman, thermogravimetric analysis, powder X-ray diffraction and magnetic measurements. Four other compounds [Cu2(phen)2(pda)(H2O)]·[H2pda]·[ClO4-]2·(H2O)4 (4.1), [Cu2(phen)2(Hpda)0.175(CH3CH2pda)0.825(H2O)]·(H2O)0.35·(ClO4-)2 (4.2), [Cu4(phen)4(pda)2(H2O)2]·(ClO4-)4·(H2O)2·(CH3CN)4 (5.1), and [Cu4(phen)4(pda)2(H2O)2] ·(ClO4-)4 ·(H2O)0.24 (5.2). could be synthesized as major phases with the suitable single crystals for structural characterization. The magnetic data in the trinuclear compound [Cu3(phen)3(pda)2(H2O)]·(ClO4)2·(H2O)4 (1), were well described with a 2-J model, with J1=-51.8 cm-1, which is consistent with the structural similarity to copper acetate, and J2=+22.9 cm-1, which follows the Goodenough−Kanamori−Anderson (GKA) rule. Zigzag chains are found in [Cu(phen)(pda)]·(H2O)2 (2). Fitting the experimental data with the Fisher chain model results in two-dimensional magnetic ordering with a long-range intrachain interactions with J =+2.52 cm-1, and the interchain coupling constant of zJ=-1.98 cm-1. The magnetic data in the [{Cu(OH)(phen)}4]·(ClO4)4 (3) with a cubane arrangement, were fitted using a 1+1+4 unique model with the J1=−28.0 cm−1, J2=+72.2 cm−1, and J3=−15.3 cm−1. By considering the CuII-O-CuII angles (θ), the magnetic interactions of the two subunits and the four diagonal interactions are consistent with the Hatfield magnetic correlation model in hydroxo-bridged binuclear compounds, and the 2+4 model, respectively. Due to the interesting structural geometries of four later coordination compounds, their structures were reported. Several compounds were synthesized using phen and pda ligands through this work. The similar stability of these compounds leads to the simultaneous occurrence of different compounds in the same reaction pot. However, three compounds were successfully synthesized in a single-phase, and their magnetic behavior was studied.



Copper(II) Coordination Compound, Transition Metal Complex, Magneto-Structural Correlation, Coupling Constant, Magnetism, Cu(II) Complexes, Solvothermal Reaction, Magnetic Behavior Study