Metal–nucleotide interactions: crystal structures of Ca[Cu(5′-GMP)2(en)-(H2O)2]·8H2O (5′-GMP = guanosine 5′-monophosphate, en = ethylenediamine) and Ca[Cu(5′-IMP)2(H2O)4]·6.7H2O (5′IMP = inosine 5′-monophosphate)
The compounds Ca[Cu(5′-GMP)2(en)(H2O)2]·8H2O(1) and Ca[Cu(5′-IMP)2(H2O)4]·6.7H2O(2) have been prepared and their structures determined (5′-GMP = guanosine 5′-monophosphate, en = ethylenediamine, and 5′-IMP = inosine 5′-monophosphate). Crystals of (1) are monoclinic space group P21, with a= 10.997(2), b= 21.693(4), c= 8.872(2)Å, β= 94.69(l)°, and Z= 2. Crystals of (2) are orthorhombic, space group C2221, with a= 8.757(2), b= 23.229(5), c= 21.212(5)Å, and Z= 4. Both structures were solved by the heavy-atom technique and refined by full-matrix least-squares calculations to R= 0.074 and R′= 0.064 for 1 266 reflections for (1) and to R= 0.094 and R′= 0.093 for 1 275 reflections for (2). In both structures the copper ion shows an elongated octahedral co-ordination with the two nucleotide moieties in cis positions bound through the N(7) purine atoms. In (2) the ethylenediamine ligand has been replaced by two water molecules. Both crystal structures are essentially based on those of the sodium salts of the respective nucleotides.