Biomolecule−Mercury Interactions: Modalities of DNA Base−Mercury Binding Mechanisms. Remediation Strategies

The first 3D coordination polymer containing a nucleobase as a bridging ligand, {[Cu2(μ-ade)4(H2O)2][Cu(ox)(H2O)]2·∼14H2O}n (1), has been synthesized by reaction of adenine (Hade) with a basic solution of K2[Cu(ox)2]·2H2O (ox = oxalato dianion). Compound 1 crystallizes in the trigonal space group R3 with a = b = 31.350(1) A, c = 14.285(1) A, V = 12158.7(10) A3, and Z = 9. X-ray analysis shows a covalent 3D network in which the copper(II) centers are bridged by tridentate μ-N3,N7,N9 adeninate ligands. The compound has relatively large, nanometer-sized tubes associated with the self-assembly process directed solely by metal−ligand interactions. The covalent 3D framework remains intact upon removal of the guest water molecules trapped in the nanotubes. Magnetic measurements indicate an overall antiferromagnetic behavior of the compound.

An unusual 3D coordination polymer based on bridging interactions of the nucleobase adenine.

Mercury(II)—Thiolate Chemistry and the Mechanism of the Heavy Metal Biosensor MerR

Synthesis, properties and crystal structures of dicopper(I) and disilver(I) complexes with 1,8-naphthyridine (napy): [Cu2(napy)2](ClO4)2 and [Ag2(napy)2](ClO4)2

Steric blockage of the N1 and N7 sites of 9-methyladenine for metal complexation is achieved by twofold methylation of the exocyclic amino group. With 6′,6′,9-trimethyladenine (TrimeA), binding of MII(dien) (M = Pt, Pd) as well as of trans-[Pt(NH3)2Cl]+ therefore takes place through N 3. X-ray crystal structure determinations and NMR spectroscopic studies of three compounds are reported, and the effects of PtII and PdII on the geometry and the acid-base properties of the TrimeA ligand have been measured and compared with those of the free base. TrimeA has a very pronounced self-stacking tendency in water (K85M−1 according to the isodesmic model of indefinite noncooperative self-association). Acidity constants derived from potentiometric pH titrations, spectrophotometry, and NMR shift experiments display excellent agreement with each other. Twofold protonated TrimeA, that is H2(TrimeA)2+, carries protons at the N7 and N1 sites; the acidity constants are pKHH2(TrimeA) = – 0.75 and pKHH(TrimeA) = 4.15. These values compare well with those of other adenine residues. Protonation of [Pt(dien)-(TrimeA-N3)]2+ occurs at the N7 position, as shown by spectrophotometry and NMR spectroscopy. The acidity constant of the H+ (N7) site in this complex is low, that is pKHH[Pt(dien)(TrimeA)] = 0.3 (as determined by spectrophotometry), but it is not as low as that for the same site when a proton resides at N1 of unmetalated TrimeA. The pKa of the doubly protonated complex, pKHH2[Pt(dien)(TrimeA)], in which the second acidic proton is situated at N1, is about–1.2 ± 0.3. These findings indicate that upon metalation of N3, the sequence of adenine protonation is reversed. While the N7 site still displays basic properties, the N1 site has undergone a dramatic loss in basicity.

The N3 Position of N9‐Substituted Adenine as a Metal Ion Binding Site: Structural and Solution Studies with PdII and PtII Complexes of N6′, N6′,N 9‐Trimethyladenine

The title compound belongs to space group with the following cell parameters: a = 6.304, b = 11.925, c = 25.946 A, α = 85.76, β = 89.78, γ = 83.57°, and Z = 4. The structure was solved by the heavy-atom method and refined on 2570 nonzero reflections to an R factor of 0.044. In the two crystallographically independent [Adeninato(CH3Hg)3]2+ ions, methylmercury groups are linearly bonded to N(3), N(7), and N(9) of a deprotonated adenine ring, forming Hg—N bonds of normal lengths (ave. 2.08 A) for two-coordinated mercury. One half of the complex cations are associated in a dimeric unit by a pair of strong hydrogen bonds, while the others are packed as individual species in the crystal. The structure is stabilized by a number of contacts between mercury and perchlorate oxygens.

Metal binding to N(9), N(7), and N(3) of adenine. Crystal structure of μ-(adeninato-N3,N7,N9)tris(methylmercury(II)) perchlorate

Crystal structure of di-.mu.-adeninium-disilver(I) perchlorate monohydrate

Crystal structure of dichlorobis(6-mercaptopurine)mercury(II)

The molecular and crystal structure of the [Pt(dien)Br]Br complex (dien = diethylenetriamine) has been studied by X-ray diffraction. The compound belongs to the orthorhombic Pca21 space group and the cell parameters are: a = 14.211, b = 4.940, c = 13.450 A, and Z = 4. The refinement of the positional and anisotropic thermal parameters, carried out by full matrix least squares calculations, converged to R = 0.039 and Rw = 0.036.The coordination around the platinum atom is planar. The crystal consists of alternate layers of [Pt(dien)Br]+ cations and Br− ions parallel to the ac plane.

The Crystal Structure of the [Pt(diethylenetriamine)Br]Br Complex

The crystal and molecular structure of dithiocyanato(triphenylarsine)mercury(II) has been determined from X-ray diffraction data. The crystals are monoclinic, space group P21/c, with a = 10.290(7),...

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Joseph Hubert

Papers

Metal binding to N(9), N(7), and N(3) of adenine. Crystal structure of μ-(adeninato-N3,N7,N9)tris(methylmercury(II)) perchlorate

Crystal structure of di-.mu.-adeninium-disilver(I) perchlorate monohydrate

Crystal structure of dichlorobis(6-mercaptopurine)mercury(II)

The Crystal Structure of the [Pt(diethylenetriamine)Br]Br Complex

Crystal and Molecular Structure of Dithiocyanato(triphenylarsine)mercury(II)