Interactions between [AuX4]− (X = Cl, CN) and cytosine and guanine model nucleobases: salt formation with (hemi-) protonated bases, coordination, and oxidative degradation of guanine
摘要:
Complexes of composition AuCl3L with L= 1,9-dimethylguanine (1,9-DimeG) (1), 2-amino-6-methoxy-9-methylpurine ((OMe)-Me-6-9-MeG) (2), 9-methylguanine (9-MeGH) (3), and 9-ethylguanine (9-EtGH) (4) were prepared from Na[AuCl4] or H[AuCl4] and L in water at pH 3.2 +/- 0.5. The X-ray crystal structures of 1 and 2 were determined. In both complexes, Au(III) binding is via N(7) of the purine ring. The coordination sphere of Au(III) is completed by three Cl ligands in a square plane and a weaker intermolecular contact with an adjacent molecule (Au ... Cl, 3.59(5) Angstrom (1) and 3.48(1) Angstrom (2)), thereby making each Au atom approximately square-pyramidal. In addition, three salts containing the fully or hemiprotonated model nucleobases 7,9-dimethylguanine (7,9-DimeGH), 9-MeGH and 1-methylcytosine (1-MeC) were X-ray structurally characterized: [7,9-DimeGH] [AuCl4] (5), [(9-MeGH(2)) . (9-MeGH) ] [Au(CN)(4)] (6), and [ ( 1-MeCH) . (1-MeC) ] [Au(CN)(4)] . 2H(2)O (7). Although poorly soluble in water, compounds 1-4 redissolve in a slow process that takes weeks to months with destruction of the purine skeleton and formation of guanidinium and parabanic acid derivatives as well as other products, depending upon the conditions applied. (C) 1998 Elsevier Science S.A. All rights reserved.
Interactions between [AuX4]− (X = Cl, CN) and cytosine and guanine model nucleobases: salt formation with (hemi-) protonated bases, coordination, and oxidative degradation of guanine
摘要:
Complexes of composition AuCl3L with L= 1,9-dimethylguanine (1,9-DimeG) (1), 2-amino-6-methoxy-9-methylpurine ((OMe)-Me-6-9-MeG) (2), 9-methylguanine (9-MeGH) (3), and 9-ethylguanine (9-EtGH) (4) were prepared from Na[AuCl4] or H[AuCl4] and L in water at pH 3.2 +/- 0.5. The X-ray crystal structures of 1 and 2 were determined. In both complexes, Au(III) binding is via N(7) of the purine ring. The coordination sphere of Au(III) is completed by three Cl ligands in a square plane and a weaker intermolecular contact with an adjacent molecule (Au ... Cl, 3.59(5) Angstrom (1) and 3.48(1) Angstrom (2)), thereby making each Au atom approximately square-pyramidal. In addition, three salts containing the fully or hemiprotonated model nucleobases 7,9-dimethylguanine (7,9-DimeGH), 9-MeGH and 1-methylcytosine (1-MeC) were X-ray structurally characterized: [7,9-DimeGH] [AuCl4] (5), [(9-MeGH(2)) . (9-MeGH) ] [Au(CN)(4)] (6), and [ ( 1-MeCH) . (1-MeC) ] [Au(CN)(4)] . 2H(2)O (7). Although poorly soluble in water, compounds 1-4 redissolve in a slow process that takes weeks to months with destruction of the purine skeleton and formation of guanidinium and parabanic acid derivatives as well as other products, depending upon the conditions applied. (C) 1998 Elsevier Science S.A. All rights reserved.