(Glycylglycinato)(cytosine)copper(II)]. A model for enzyme–metal–nucleic acid ternary complexes

Abstract

The synthesis and crystal structure of the complex [(glycylglycinato) (cytosine)copper(lI)], CuO4NsCsHll, are reported. The complex crystallizes as the dihydrate in the monoclinic system, space group P2~/n, with a= 10.695 (4), b= 8.077 (1), c-14.756 (7) ,~, fl=92.38 (3) °, Z=4, D,,= 1.78 (1), De= 178 gcm -a Intensities for 2951 symmetry-averaged reflections were collected in the 0-20 mode by counter methods. The structure was solved by standard heavy-atom Patterson and Fourier methods. Full-matrix leastsquares refinement has led to a final R value of 0.084. The final weighted R value and goodness-of-fit are 0.042 and 1.3, respectively. The primary coordination sphere about the copper is approximately square planar with the tridentate glycylglycine dianion and N(3) of cytosine occupying the four coordination sites. The copper also forms two weak, axial interactions with 0(2) of cytosine, one intramolecular, Cu. . .0 (2) 2.819 (3) ,~, and one intermolecular, Cu.--0(2) 2.713 (3) A. The crystal structure is dominated by columnar stacks of complcxcs about the twofold screw axis along b with intracolumn interactions via the weak Cu--. 0(2) intermolecular bond and hydrogen bonds of the type N(4) [cytosine]... 0(2) [cytosine] and N(10) [glycylglycine]...O(7) [glycylglycine]. The columns are directly linked by hydrogen bonds involving N(4) and N(1) of cytosine and 0(8) and 0(9) of glycyiglycine and further coupled by hydrogen bonds through the waters of crystallization.