Crystal structure of diaqua-bis(1,10-phenanthroline)-bis(benzenesulfonylalaninato)- gadolinium(III) nitrate dihydrate, [Gd(C11H10NO3S)2(C10H8N2)2(H2O)2][NO3] · 2H2O

Abstract

Source of materialFor the preparation of the ligand (Bs-alaH 2 , Bs = N-benzenesulfonyl), BsCl (6.9 g, 0.03 mol) was added to a solution of alanine (2.7 g, 0.03 mol) in 1 M NaOH (50 mL). The mixture was stirred under reflux at room temperature for 5 h, and then, the aqueous solution was acidified to pH = 4 with 6 M hydrochloric acid and a white solid derivative crystallized at once. The crystals were collected on a filter and recrystallized from 20 mL of 50 % alcohol (yield about 64 %). For the preparation of the complex, Gd2O3 (5 mmol) was solved in 6 M HNO3, the excessive HNO 3 was removed by evaporation, then water (about 10 mL) was added to obtain the solution of Gd(NO3)3. Then a solution of Bs-alaH2 (5 mmol) in 40 mL of 60°C water was added to the solution of Gd(NO3)3, the mixture was kept on stirring for 3 h at 60°C, and the solution of phen (20 mL, 10 mmol) was added. The resulting solution was adjusted to keep a pH value of 4-5 using 2 M NaOH and stirred for 24 h at 60°to obtain a red solution. The solution left to evaporate for about 15 days at room temperature, giving pale red rod-shaped crystals. Experimental detailsOne nitrate anion and two water molecules were found to be disordered. Except the H atoms of the disordered water, all H atoms belonging to N or O atoms were determined from Fourier difference maps and refined by means of geometrical restraints. H atoms attached to C atoms were added geometrically and treated as riding. DiscussionAmino acids are the fundamental structure unit of biomacromolecules, such as protein and enzyme, and they are also the important biomicromolecular ligands inside the life body [1,2]. Nprotected amino acids have analogous structure with O-terminal of peptide, so its coordination behavior might be similar. The complexes of N-protected amino acids with transition metals have been widely investigated [3][4][5][6][7][8], in which the N-protected amino acids have different coordination behavior at different pH values or different transition metal ions. Recently, rare earths with amino acids compounds have been attracting more and more attention for their important biochemical and medical applications. The structure and biological activity of binary rare earth complexes with N-p-tolylsulfonyl-b-alanine were reported in the literature [9][10][11], but the ternary complexes more approach biological surrounding than the binary complexes, therefore, we describe a ternary complex structure of Gd(III) with N-sulfonyl amino acids and phenanthroline. The complex exhibits several characteristic strong bonds: The one observed at 3260 cm 1 is attributed to the NH stretching vibration, that at 1613 cm 1 can be assigned to the C=N stretching vibration, those at 1318 cm 1 and 1165 cm 1 are due to vas(SO2