Supramolecular polymer of Schiff base gadolinium complex: Synthesis, crystal structure and spectroscopic properties

Abstract

The new gadolinium(III) nitrate complex [Gd(H2L)2(NO3)3(EtOH)]MeOH where H2L is N,N′-bis(5-methylsalicylidene)-4-methyl-1,3-phenylenediamine was obtained in template condensation reaction of 5-methylsalicylaldehyde with 4-methyl-1,3-phenylenediamine in presence of gadolinium(III) nitrate hexahydrate. The structure of the complex was determined by single-crystal X-ray diffraction analysis and by physicochemical methods. The central cation is nine-coordinated, and the coordination resembles distorted tricapped trigonal prism and only oxygen atoms are involved in coordination. In the crystal structure there is uncoordinated solvent – methanol molecule. The methanol molecule plays an important role in the crystal packing by hydrogen bonding and it connects the complex molecules into infinite chains. Electron paramagnetic resonance studies confirmed complex formation of gadolinium ion because internal coordination sphere of gadolinium was changed. The absorption and fluorescence properties of [Gd(H2L)2(NO3)3(EtOH)]MeOH were studied in different solvents: ethyl acetate, 1-propanol, methanol, ethanol and acetonitrile. Fluorescence quantum yields (ΦF) were calculated for the complex in all solvents and the values, of ΦF are rather low, the exact values depend on solvent, being between 0.0005 (in acetonitrile and ethyl acetate) and 0.0014 (in 1-propanol).