Crystal and molecular structure of (cyclo-L-methionylglycine)silver(I) nitrate

Abstract

The structure of the title compound has been determined by single-crystal X-ray diffraction methods. The compound crystallizes in the monoclinic system, space group P2₁, with unit-cell dimensions a= 13.634(6), b= 6.225(4), c= 6.784(4)Å, β= 104.8(7)°, and Z= 2. The structure was solved by the heavy-atom method and refined by least-squares calculations to a conventional R factor of 0.052 based on 1 342 independent observed reflections. The structure comprises infinite linear arrays of silver atoms doubly bridged by methionine sulphur atoms and nitrate groups. Each silver atom is surrounded by two sulphurs at 2.511(2) and 2.577(2)Å, two oxygens of a nitrate group at 2.512(7) and 2.574(9)Å, and two oxygens of a second nitrate group at 2.523(9) and 2.855(9)Å. Comparison with the crystal structure of the uncomplexed dipeptide shows remarkable conformational changes upon co-ordination.