Jerzy Sitkowski

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

SYNTHESIS AND STRUCTURE DETERMINATION OF SOME OXADIAZOLE-2-THIONE AND TRIAZOLE-3-THIONE GALACTOSIDES

The syntheses of 5-pyridyl-3((β-D-galactopyranosyl)-1,3,4-oxadiazole-2-thiones 3a–3c and 5-pyridyl-2((β-D-galactopyranosyl)-4-benzyl-1,2,4-triazole-3-thiones 6a–6c are reported. The existence of N-galactosides – not S-galactosides – was proven by IR and 15N NMR spectroscopy. The structures of the final products and the intermediates were elucidated by IR, 1H, 13C and 15N NMR spectroscopy and mass spectrometry. †Deceased.

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.

13 C NMR differentiation of diastereoisomeric complexes of cis-decalin with β-cyclodextrin

13 C NMR spectra show chiral discrimination between two invertomers of cis-decalin complexed with β-cyclodextrin.

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

A multinuclear NMR study of proton transfer processes in Schiff bases

Abstract 1 H, 13 C and 15 N NMR data are reported for seven Schiff bases in order to study the possibility of proton transfer from oxygen to nitrogen. The compounds contain various substituents which influence the acidity of the OH group and the basicity of the nitrogen atom. All the NMR results provide a consistent view of the extent of proton transfer. The reported value of 1 J( 15 N − 1 H ) is used to give a quantitative estimate of this extent. Low temperature 15 N NMR results for compound 7 show an increase in proton transfer with respect to that found for this molecule at room temperature.

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.