title: Synthesis, structures, and electrochemistry of gold(III) ethylenediamine complexes and interactions with guanosine 5'-monophosphate.
abstract: [Au(en)Cl(2)]Cl.2H(2)O, where en = ethylenediamine (1,2-diaminoethane), has been synthesized, and its structure has been solved for the first time by the single-crystal X-ray diffraction method. The complex has square-planar geometry about Au(III), and the anionic Cl- is located in the apical position and at a distance of 3.3033(10) A compared to 2.2811(9) and 2.2836(11) A for the coordinated Cl-. [Au(en)Cl2]Cl.2H2O belongs to the space group Pbca with a = 11.5610(15) A, b = 12.6399(17) A, c = 13.2156(17) A, alpha = beta = gamma = 90 degrees , and Z = 8. Bond lengths of Au-N are 2.03 A. [Au(en)Cl2]Cl.2H2O is less thermally stable than [Au(en)2]Cl3 because of the replacement of two Cl ligands by a second en ligand in the latter. Cyclic voltammetry shows that the formal potential of Au(III)/Au(0) becomes more negative in the series [AuCl4]-, [Au(en)Cl2]+, and [Au(en)2]3+. 1H, 13C, and 31P NMR reveal that in an aqueous solution [Au(en)Cl2]+ bonds to guanosine 5'-monophosphate, 5'-GMP (1:1 mole ratio), via N7, although the stability is not very high. NMR data also indicate that N7-O6 or N7-phosphate 5'-GMP chelation, as found in some gold(III) nucleotide complexes, is not present. The gold(III) complex undergoes hydrolysis at pH >2.5-3.0 and, therefore, N1 coordination to 5'-GMP is not observed. No direct coordination between 5'-GMP and [Au(en)2]Cl3 is observed.
authors.affiliation: Department of Chemistry, The University of Texas at San Antonio, 6900 North Loop 1604 West, San Antonio, Texas 78249-0698, USA.
authors.forename: Shourong
authors.initials: S
authors.lastname: Zhu
authors.forename: Waldemar
authors.initials: W
authors.lastname: Gorski
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Powell
authors.forename: Judith A
authors.initials: JA
authors.lastname: Walmsley
mesh_terms: D004563:Electrochemistry; D005029:Ethylenediamines / Q000737:chemistry*; D006157:Guanosine Monophosphate / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D050607:Organogold Compounds / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D005029:Ethylenediamines; D050607:Organogold Compounds; C031234:ethylenediamine; D006157:Guanosine Monophosphate