Lech Kozerski

The X-ray structure and spectroscopy of platinum(II) complexes with 1,2,4-triazolo[1,5-a]pyrimidines and dimethylsulfoxide

Abstract Platinum(II) complexes with 1,2,4-triazolo[1,5-a]pyrimidines of general formula trans-[PtCl2(dmso)(L)], where L=1,2,4-triazolo[1,5-a]pyrimidine (tp), 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp), 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine (dptp), 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) have been prepared by direct reaction between cis-[PtCl2(dmso)2] and respective 1,2,4-triazolo[1,5-a]pyrimidine in molar ratio M:L=1:1. All new platinum(II) compounds were characterized by 1H, 13C, 15N, 195Pt NMR and IR. Significant 15N NMR upfield shifts (75–87 ppm) were observed for N(3) atom indicating this nitrogen atom as a coordination site. Crystal structure of trans-[PtCl2(dmso)(dmtp)] (2) has been determinated. The molecular structure indicates that Pt(II) ion has the square-planar geometry with N(3) bonded dmtp, S-bonded dimethylsulfoxide and two trans chloride anions.

Structural correlations for 1H, 13C and 15N NMR coordination shifts in Au(III), Pd(II) and Pt(II) chloride complexes with lutidines and collidine

1H, 13C and 15N NMR studies of gold(III), palladium(II) and platinum(II) chloride complexes with dimethylpyridines (lutidines: 2,3‐lutidine, 2,3lut; 2,4‐lutidine, 2,4lut; 3,5‐lutidine, 3,5lut; 2,6‐lutidine, 2,6lut) and 2,4,6‐trimethylpyridine (2,4,6‐collidine, 2,4,6col) having general formulae [AuLCl3], trans‐[PdL2Cl2] and trans‐/cis‐[PtL2Cl2] were performed and the respective chemical shifts (δ1H, δ13C, δ15N) reported. The deshielding of protons and carbons, as well as the shielding of nitrogens was observed. The 1H, 13C and 15N NMR coordination shifts (Δ1Hcoord, Δ13Ccoord, Δ15Ncoord; Δcoord = δcomplex − δligand) were discussed in relation to some structural features of the title complexes, such as the type of the central atom [Au(III), Pd(II), Pt(II)], geometry (trans‐ or cis‐), metal‐nitrogen bond lengths and the position of both methyl groups in the pyridine ring system. Copyright

Theoretical and experimental 1H, 13C, 15N, and 17O NMR chemical shifts for 5-halogenouracils

Abstract Theoretical and experimental 1 H, 13 C, 15 N, and 17 O NMR chemical shifts for uracil and 5-halogenouracils were determined and analyzed. The theoretical NMR chemical shifts were calculated based on the HF and MP2 GIAO approach using the 3-21G ∗∗ , MIDI!, polarized double zeta Hansen–Bouman, and the polarized triple zeta Sadlej basis sets. The solvent effect was checked at the HF/3-21G ∗∗ level by surrounding the uracil molecule by seven water molecules. For all the nuclei studied in the series of halogenouracils, linear correlation was tested between the chemical shift (both experimental and theoretical) and halogen electronegativity. All the carbon–proton and one-bond carbon–carbon spin–spin coupling constants were measured and used to assign the carbon signals.

Assessment of Oversulfated Chondroitin Sulfate in Low Molecular Weight and Unfractioned Heparins Diffusion Ordered Nuclear Magnetic Resonance Spectroscopy Method

Heparins can be contaminated with oversulfated chondroitin sulfate, OSCS, the impurity being linked to adverse clinical events that certain lots of heparins have had on humans. Here, we propose labeling of the N-acetyl peaks in (1)H NMR spectra of heparins with the parameter D(t), describing the translational diffusion coefficient available from DOSY NMR. We show how DOSY can be applied as a routine method for screening the lots of heparins for obtaining the impurity profile when using (1)H NMR.

The X-ray structure of bis(5,7-dimethyl-1,2,4-triazolo-[1,5α]-pyrimidinium) hexachloroplatinate(IV) and spectroscopic properties of Pt(II) and Pt(IV)chloride complexes with 1,2,4-triazolo-[1,5α]-pyrimidines

Abstract Pt(II) and Pt(IV) chloride complexes with 1,2,4-triazolo-[1,5α]-pyrimidines: trans-[Pt(tp)2Cl2], trans-[Pt(dmtp)2Cl2], trans-[Pt(tp)2Cl4] and trans-[Pt(dmtp)2Cl4] where tp=1,2,4-triazolo-[1,5α]-pyrimidine and dmtp=5,7-dimethyl-1,2,4-triazolo-[1,5α]-pyrimidine were synthesised and studied by 1H, 13C, 15N, 195Pt NMR and IR spectroscopies. Significant 15N NMR upfield coordination shifts (92–96 ppm) were observed for the N(3) atom indicating that this nitrogen is the metallation site. The X-ray structure of an ionic pair (dmtpH)2[PtCl6] {bis(5,7-dimethyl-1,2,4-triazolo-[1,5α]-pyrimidinium) hexachloroplatinate(IV)} was determined, exhibiting the presence of unique (dmtpH)22+ dimeric cations, protonated at N(3), N(3′) atoms and linked by hydrogen bonding.

1H, 13C, 15N and 195Pt NMR studies of Au(III) and Pt(II) chloride organometallics with 2-phenylpyridine.

1H, 13C, 15N and 195Pt NMR studies of gold(III) and platinum(II) chloride organometallics with N(1),C(2′)‐chelated, deprotonated 2‐phenylpyridine (2ppy*) of the formulae [Au(2ppy*)Cl2], trans(N,N)‐[Pt(2ppy*)(2ppy)Cl] and trans(S,N)‐[Pt(2ppy*)(DMSO‐d6)Cl] (formed in situ upon dissolving [Pt(2ppy*)(µ‐Cl)]2 in DMSO‐d6) were performed. All signals were unambiguously assigned by HMBC/HSQC methods and the respective 1H, 13C and 15N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: Δ1Hcoord = δ1Hcomplex − δ1Hligand, Δ13Ccoord = δ13Ccomplex − δ13Cligand, Δ15Ncoord = δ15Ncomplex − δ15Nligand), as well as 195Pt chemical shifts and 1H‐195Pt coupling constants discussed in relation to the known molecular structures. Characteristic deshielding of nitrogen‐adjacent H(6) protons and metallated C(2′) atoms as well as significant shielding of coordinated N(1) nitrogens is discussed in respect to a large set of literature NMR data available for related cyclometallated compounds. Copyright

Fluorometric and NMR Studies of the Naproxen–Cyclodextrin Inclusion Complexes in Aqueous Solutions

Inclusion complexation processesinvolving four cyclodextrins and naproxen have beenstudied for the protonated and unprotonated forms ofthe guest molecule. The association constants havebeen evaluated from changes in the fluorescenceintensity of naproxen following addition of acyclodextrin to an aqueous naproxen solution. 1HNMR NOESY and ROESY spectra have shown that twoorientations of the guest molecule relative toβ-cyclodextrin are possible.

Direct insight into insulin aggregation by 2D NMR complemented by PFGSE NMR

The aggregation of Zn(II)‐bound and zinc‐free human insulin was studied in solution using the Hβ∼CH3 crosspeaks of threonine residues in 2D COSY, TOCSY, and NOESY NMR spectra which allow viewing of the oligomers in equilibrium. This is complemented by PFGSE measurements of the translational diffusion coefficient, Di, used for monitoring the changes in equilibrium composition of aggregates on dilution of both insulins in physiological medium. The back calculation of the dilution isotherm allows establishing the association constants for oligomeric equilibria in solution and discussion of the models of association. Proteins 2008.

Interaction of flavonoid topoisomerase I and II inhibitors with DNA oligomers

The binding affinities of flavonoids, genistein and quercetin, to DNA oligomers have been established by means of studying by NMR the diffusion coefficients of these compounds with and without the presence of DNA. Genistein was found to bind very weakly, Ka = 1.54 × 102 M−1, as compared to quercetin, Ka = 5.75 × 103 M−1 and luteolin, Ka = 2.17 × 104 M−1 (as reported in the literature). In the case of genistein a hydrogen bond between the NHF,B cytidine protons of the edge base pair and a genistein hydroxyl is proposed, based on the shape of the DOSY spectrum. MP2 and DFT calculations of genistein show a 9 kcal mol−1 excess energy of the planar conformation as compared with a twisted one. For this reason intercalation of the planar genistein into the base pairs is rather unlikely.

1H NMR assignment corrections and 1H, 13C, 15N NMR coordination shifts structural correlations in Fe(II), Ru(II) and Os(II) cationic complexes with 2,2′-bipyridine and 1,10-phenanthroline

1H, 13C and 15N NMR studies of iron(II), ruthenium(II) and osmium(II) tris‐chelated cationic complexes with 2,2′‐bipyridine and 1,10‐phenanthroline of the general formula [M(LL)3]2+ (M = Fe, Ru, Os; LL = bpy, phen) were performed. Inconsistent literature 1H signal assignments were corrected. Significant shielding of nitrogen‐adjacent protons [H(6) in bpy, H(2) in phen] and metal‐bonded nitrogens was observed, being enhanced in the series Ru(II) → Os(II) → Fe(II) for 1H, Fe(II) → Ru(II) → Os(II) for 15N and bpy → phen for both nuclei. The carbons are deshielded, the effect increasing in the order Ru(II) → Os(II) → Fe(II). Copyright