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# Synthesis and x-ray structure of a mercury(II) complex with adenine N(1)-oxide. A model for mercury binding to DNA

Poojary, Damodara M and Manohar, H (1984) Synthesis and x-ray structure of a mercury(II) complex with adenine N(1)-oxide. A model for mercury binding to DNA. In: Inorganica Chimica Acta, 93 (4). pp. 153-160.

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## Abstract

The synthesis and crystal structure of the adenine N(1)-oxide complex with mercury(II) chloride, $(C_5H_5N_5O)HgCl_2$ are reported. Crystals of the coordination compound belong to the monoclinic system, space group $P2_1/n$ with the following primary crystallographic data: $a = 6.685(1) \AA$, $b = 11.798(2) \AA$, $c = 10.155(1) \AA$, $\beta = 100.22(1)°$, $V = 906.04 {\AA}^3$, Z = 4. The structure was elucidated by conventional Patterson and Fourier methods and refined by the full matrix least-squares technique on the basis of 1977 observed reflections to an R value of 0.074. The basic unit of the structure is a dimer, with a centre of symmetry, consisting of two $HgCl_2$ moieties and two adenine N(1)-oxide ligands. A polymeric structure results from the bridging interactionsof chloride ions. Adenine N(1)-oxide acts as a bidentate bridging ligand, coordinating through N(7) and O(1). The coordination geometry around the mercury ion is a distorted square pyramid with N(7) and three chlorines (two of which are centro-symmetrically related) forming the square plane and O(1) occupying the axial position. Hg also interacts indirectly with N(6) through a $Cl\cdots \cdot H-N$ hydrogen bond. Principal intracomplex geometrical parameters are as follows: $Hg-N(7) = 2.61(1) \AA$, $Hg-O(1) = 2.55(1) \AA$, $Hg-Cl(1) = 2.330(3) \AA$, $Hg-Cl(2) = 2.318(3) \AA$, $Hg-Cl(2^{\prime}) = 3.347(3) \AA$. The cis angles range from 77.5° to 107.9° and the two trans angles are 155.5° and 163.1°. The centro-symmetrically related bases overlap partially and pack at a distance of $3.2 \AA$. The glide-related bases are linked by a hydrogen bond, $N(9)-H \cdots \cdot O(1)$ and are inclined to one another by 109.7°. The results are compared with those derived from spectroscopic and other physicochemical studies on metal interaction with adenine N(1)-oxide. Based on the present structural observations and earlier experimental results a possible mechanism is proposed for mercury interaction with DNA.

Item Type: Journal Article Copyright of this article belongs to Elsevier Science B.V. Division of Chemical Sciences > Inorganic & Physical Chemistry 24 Mar 2008 19 Sep 2010 04:43 http://eprints.iisc.ernet.in/id/eprint/13449

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