L. G. Marzilli

Dipeptide-metal-nucleoside complexes as models for enzyme-metal-nucleic acid ternary species. synthesis and molecular structure of the cytidine complex of glycylglycinatocopper(II)

The cytidine complex of glycylglycinatocopper(II) has been synthesized, and its molecular structure determined by single-crystal X-ray diffraction methods. The complex crystallizes in the monoclinic system, space group P21, with a = 4.716(3)A, b = 26.86(6)A, c = 14.761(14)A, β = 90.63(6)°, Z = 4. The two independent complexes in the asymmetric unit have nearly identical molecular conformations. The coordination geometry about the copper is approximately square planar with the tridentate glycylglycine dianion and N(3) of cytidine occupying the four coordination sites. The binding of the nucleoside to the dipeptide complex is further enhanced by a weak, axial Cu⋯O(2)[cytidi

Solution and solid state studies on the interactions of protonated cytosine salts. III. Interpyrimidine base stacking and asymmetric interbase hydrogen bonding in the structure of 1-methylcytosine hemihydroiodide hemihydrate

Abstract Structural and spectroscopic data are presented on the compound 1-methylcytosine hemihydroiodide hemihydrate. In the solid, a 1:1 triply hydrogenbonded complex consisting of one protonated and one neutral 1-methylcytosine base is observed. The hydrogen bonding in this complex is asymmetric, and the asymmetry in the interbase hydrogen bonding is stimulated, at least in part, by base stacking considerations. The hydrogen-bonded base pairs associate into dimers about a crystallographic center of symmetry; the base-base stacking mode is strong [mean stacking distance = 3.22A] and is such that the molecular overlap is between protonated and neutral 1-methylcytosine molecules. The asymmetric, interbase hydrogen bonding and the protonated over neutral base stacking mode coexist in a synergistic interrelationship which maximizes molecular association and crystal packing. Intermolecular hydrogen bonds involving the 1-methylcytosine bases, the water of crystallization and the iodide anion also contribute to the overall crystal stability. Infra-red and 1H nmr data are also presented.

A new approach for assigning phosphorus-31 NMR signals and correlating adjacent nucleotide deoxyribose moieties via proton-detected multiple-quantum NMR. Application to the adduct of d(TGGT) with the anticancer agent (ethylenediamine)dichloroplatinum.

Compared to ‘H, I3C, and I5N NMR spectra, useful 31P spectra of DNA and nucleosomes under physiological conditions can be obtained more readily.’ Studies of oligodeoxyribonucleotides, where even small 31P shifts can be observed and interpreted* and spectra of other nuclei can be observed easily, can provide greater insight into 31P spectral changes on drug, carcinogen, or protein binding to DNA. Unfortunately, full utilization of 31P NMR spectroscopy is hampered by difficulties in signal assignment.* The most reliable method to date (170/’80 labeling) is limited to synthetic materials3 We report a new approach for the assignment of the 31P NMR resonances in oligodeoxyribonucleotides via ‘H-detected heteronuclear multiple-quantum coherence (HMQC) two-dimensional correlation spectroscopy” combined with 2D-NOE methods. This approach exploits the method reported for sensitivity enhancement of heteronuclei in numerous system^;^ however, we illustrate the advantage of this experiment for information content involving abundant nuclei. The HMQC experiment selects only those ‘H nuclei that are spin-coupled to (e.g., deoxyribose H3/,H{,Hr) and correlates them with their respective 31P signals. The H3’,HS’,H5’’ signals can be assigned via ’H 2D-NOE methods. Due to the narrow shift range of 3’P in these systems, it is essential to record the spectrum as a direct correlation of ‘H and 31P chemical shifts by removal of the ‘H resonance offset contribution to the F1 dimension.48*e This has been accomplished via the pulse sequencek

On the non-stoichiometry of the binding of Pt(II) anti-neoplastic agents to inosine 5′-monophosphate

Abstract A non-stoichiometric material [Na 4 (5′-IMP) 2 ·15H 2 O] 0.2 [Na 2 (Pt(5′-IMP) 2 (trimethylenediamine))·13.5H 2 O] 0.8 has been prepared and investigated by single-crystal X-ray methods and 1 H and 13 C nmr spectroscopy. The compound is isomorphous with the monosodium and disodium salts of 5′-IMP and two Pt(II)-5′-IMP compounds previously reported to be non-stoichiometric. However, the structural changes in the packing motif of the 5′-IMP molecules induced on Pt(II) coordination are uniform only if the 5′-IMP complex containing (NH 3 ) 2 Pt(II) is stoichiometric. Preliminary studies on the latter complex, synthesized in our laboratories, demonstrate that the complex is indeed stoichiometric.

Conformational properties of the osmium tetraoxide bispyridine ester of 1-methylthymine and a comment on the linearity of the trans OOsO group

The preparation and crystal and molecular structure of the osmium tetraoxide bispyridine ester of 1-methylthymine are reported. The complex crystallizes in the triclinic system, space group P1, with a = 11.493(6)A, b = 16.655(7)A, c = 6.082(2)A, alpha = 92.07(3) degrees, beta = 90.58(3) degrees, gamma = 71.36(4) degrees, V = 1102.4 A3, Dm = 1.85(1) g cm-3, DC = 1.84 g cm-3. The unit cell contains 2 osmium tetraoxide bispyridine esters of 1-methylthymine, 2 waters of crystallization and 1 disordered pyridine of solvation. Intensities for 3814 independent reflections were collected by counter methods. The structure was solved by standard heavy-atom techniques and has been refined by full-matrix least squares, based on F, to a final R value of 0.065. The osmium complex binds as a cis osmate ester to the C(5)-C(6) bond of the methylated pyrimidine in a fashion which is expected to be similar to the binding of the complex to thymidine residues in nucleic acids. The conformation of the 1-methylthymine ester is that of a half chair with C(6) showing a substantial deviation, 0.55 A, from the best mean plane of the thymine moiety. The primary coordination sphere about the Os(VI) atom is completed by 2 axial Os=O bonds and the binding of the 2 pyridine ligands in cis positions in the equatorial plane containing the ester linkages. The O=Os=O group is substantially nonlinear, 164.0(5) degrees, and this nonlinearity is attributed to intracomplex electronic effects.

Structural study of steric effects in cobalt dimethylglyoximates containing phosphine ligands. The structure of trans-Bis(dimethylglyoximato)methyltriphenylphosphinecobalt(III) and of trans-Bis(dimethylglyoximato)chlorotricyclohexyl phosphinecobalt(III) toluene solvate

Abstract The crystal and molecular structure of the title compounds has revealed that crystals of trans -bis(dimethylglyoxinate)methyltriphenylphosphinecobalt(Ill) (I) are monoclinic space group P2 1 with a = 10.4061(8), b = 15.54(1), c = 8.963(5) A β = 108. 75(7)°, Z = 2 and crystals of trans-bis (dimethylglyoximate)chlorotricyclohexylphotphinecobalt(1II) (II) are monoclinic, space group P2 1 / c with a = 9.501(7), b = 29.33(1), c = 12.98(1) A β = 99.0(1)°, Z = 4. The structures have been solved by three-dimensional Patterson and Fourier methods and refined by the least-squares technique. The final R values were 0.032 for (I) and 0.072 for (II), calculated on the basis of 1850 and 1651 independent reflections respectively. In (I) the Co-P bond length of 2.418(1) A is the largest value so far reported and confirms the strong trans -influence of the methyl group (Co--CH 3 , 2.026(6) A ). The coordinated N atoms are coplanar within ±0.015 A ; the cobalt is displaced of O. 112 A above their mean plane towards the phosphine. The two dmgH units are bent away from the photphine ligand and their mean planes make an angle of 13. 6°. The axial bond lengths in (II) are: Co-P 2.369(5) A , Co-CI 2.294(5) A. The coordinated N atoms are coplanar within 0.007 A with Co displaced of O. 10 A towards phosphine ligand, whereas the two dmgH mean planes make an angle of 15.7° These results are discussed in terms of steric factors. Correlation with experimental cone angles and n.m.r. results is discussed.

Solution and Solid State Studies on the Interactions of Protonated Cytosine Salts. IV. Asymmetric Interbase Hydrogen Bonding and Interpyrimidine Base Stacking in Triply Hydrogen-Bonded Cytosine Complexes. Crystal and Molecular Structure of Bis[1-Methylcytosine, 1-Methylcytosinium] Hexafluorosilicate Dihydrate

Abstract The crystal and molecular structures of the complex bis(1-methylcytosine, 1-methylcytosinium) hexafluorosilicate dihydrate are reported. In the solid, a 1:1 triply hydrogen-bonded complex consisting of one protonated and one neutral 1-methylcytosine base is observed. The hydrogen bonding in the complex cation is asymmetric, and the asymmetry in the interbase hydrogen bonding is stimulated to a large part by base stacking. The observed infinite, helical array of stacked complexes, in which the base stacking is strong [mean stacking distance = 3.36A] is such that the molecular overlap is between protonated and neutral 1-methylcytosine bases. The asymmetric interbase hydrogen bonding and the protonated/neutral base stacking mode coexist in a synergistic interrelationship which maximizes the molecular and crystal forces. The results found in this study are compared with a variety of other systems in which asymmetrically hydrogen-bonded cytosine complexes are observed, and it is found that although base stacking is also a predominant feature of these complexes in the solid, the base stacking found in this study is different.

Coordination chemistry of 7,9-disubstituted 6-oxopurine metal compounds. 4. Platinum(II) coordination at N(1). Molecular and crystal structure of [(ethylenediamine)bis(7,9-dimethylhypoxanthine)platinum(II)] hexafluorophosphate ☆

Abstract The preparation and molecular and crystal structure of the complex [(ethylenediamine)bis(7,9,-dimethylhypoxanthine)platinum(II)] hexafluorophosphate, [Pt(C 2 H 8 N 2 )(C 7 H 8 N 4 O) 2 ] (PF 6 ) 2 , are reported. The complex crystallizes in the monoclinic system, space group C2/c, with a = 12.334(2)A, b = 10.256(2)A, c = 22.339(3)A, β = 101.31(1)°, V = 2771.0A 3 , Z = 4, D measd = 2.087(3) g cm −3 , D calc = 2.094 g cm −3 . Intensities for 3992 symmetry-averaged reflections were collected in the θ-2 o scan mode on an automated diffractometer employing graphite-monochromatized MoKα radiation. The structure was solved by standard heavy-atom Patterson and Fourier methods. Full matrix least-squares refinement led to a final R value of 0.051. Both the ethylenediamine chelate and the PF 6 − anion are disordered. The primary coordination sphere about the Pt(II) center is approximately square planar with the bidentate ethylenediamine ligand and the N(1) atoms [Pt(II) − N(1) = 2.020(5)A] of two 7,9-dimethylhypoxanthine bases (related by a crystallographic twofold axis of symmetry) occupying the four coordination sites. The exocyclic O(6) carbonyl oxygen atoms of the two 7,9-dimethylhypoxanthine ligands participate in intracomplex hydrogen bonding with the amino groups of the ethylenediamine chelate [ N (ethylenediamine) ⋯ O(6) = 2.89( )A]. The observed Pt ⋯ O(6) intramolecular distances of 3.074(6)A are similar to those found in other Pt(II) N(1)-bound 6-oxopurine complexes and in several Pt(II) N(3)-bound cytosine systems.

Structures of two N(1)-bound platinum(II)-6-oxopurine complexes. Comparisons with complexes derived from platinum(II) anti-tumor agents

Abstract The preparation and molecular structure of [(diethylenetriamine) (7,9-dimethylhypoxanthine) platinum(II)] (PF 6 ) 2 ·1.5H 2 O and [(ethylenediamine) (7,9-dimethylhypoxanthine) 2 platinum(II)] (PF 6 ) 2 , are reported. These complexes represent the first structurally characterized N(1)-bound Pt(II) 6-oxopurine complexes. In each case, the Pt(II)N(1) bond length [2.051(6)A in the diethylenetriamine complex and 2.021(8)A in the ethylenediamine complex] indicates a strong metal-to-base binding. Both complexes contain interligand hydrogen bonds, with the ammine ligand acting as the donor and the O(6) atom of the base acting as the acceptor. These N(1)-bound complexes are compared with N(7)-bound 6-oxopurine and N(3)-bound cytosine complexes of Pt(II) anti-tumor agents.

Phosphorus-31 NMR spectra of cobaloximes: Influence of electronic and steric effects of axial ligands

The 31P NMR spectra of a large number of cobaloxime compounds having the general formula trans-Co(DH)2(L)X (where DH = the monoanion of dimethylglyoxime) have been measured. Series examined include those where L = tri-n-butylphosphine or trimethylphosphite, X = various ligands and L = various phosphorus donors, X = Cl− or CH−3. Several factors were found to influence the 31P coordination chemical shifts (Δs) such as ligand cone angle, hybridization of the phosphorus donor orbital, substituent groups on the phosphorus, and the trans-influence (or -effect) of the X groups. The data are discussed in the context of other NMR and structural studies of cobaloximes. The results lend support to a common trans-effect/influence series for octahedral complexes [1, 2].