Biomedical subjects

Tadeusz J Bartczak

Publications and source records attributed to Tadeusz J Bartczak.

5 recordsLinked to original sources

PubMed2006

Bond-valence parameters of lanthanides.

Ln-O and Ln-N bond-valence parameters have been computed in coordination complexes for lanthanides (Ln) at oxidation states other than +3 (Ce(IV), Sm(II), Eu(II) and Yb(II)). Moreover, Ln-Cl, Ln-S and Ln-C(pi-bonded) bond-valence parameters are presented, as calculated for coordination compounds. In general, the bond-valence parameters decrease in the order Ln-O > Ln-C > Ln-N > Ln-Cl > Ln-S. It has been found that the values of bond-valence parameters decrease with increasing lanthanide atomic number for coordination compounds. As expected, the values of lanthanide-oxygen and lanthanide-nitrogen bond-valence parameters diminish with increasing lanthanide oxidation state. Several examples are given where the total valence of the lanthanide ion is apparently incorrectly assigned, as well as cases where bond-valence method calculations confirm the doubtful oxidation state assignment.

Journal Article↗

PubMed2005

Bis{mu-2-[(2,3-dichlorophenyl)amino]benzoato-kappaO}di-mu2-ethoxo-octamethyldi-mu3-oxo-tetratin(IV).

The title compound, [Sn4(CH3)8(C13H8Cl2NO2)2(C2H5O)2O2], is a centrosymmetric dimer, with three linearly fused four-membered Sn-O-Sn-O rings. The coordination polyhedron of the Sn atom bonded to the carboxylate can be described as trigonal-bipyramidal distorted toward square-pyramidal. That of the second Sn atom is similar, but the distortion towards square-pyramidal geometry is greater. The Sn-O and Sn-C distances are 2.020 (2)-2.226 (2) and 2.096 (4)-2.114 (4) A, respectively. The benzene rings of the 2-[(2,3-dichlorophenyl)amino]benzoate ligand subtend an angle of 50.49 (17) degrees; the conformation of the ligand is stabilized by intramolecular N-H...Cl and N-H...O hydrogen bonds. The structure is assembled via pi-pi stacking interactions to form chains parallel to [120].

Anti-Inflammatory Agents↗

PubMed2005

New lanthanide-nitrogen bond-valence parameters.

The bond-valence parameters (R(ij)), which connect bond valences and bond lengths, have been computed for lanthanide-nitrogen bonds. It has been found that values of bond-valence parameters decrease with increasing lanthanide atomic number in coordination compounds, and that they are smaller than the R(ij) parameters of inorganic compounds. As expected, the lanthanide-nitrogen bond-valence parameters are larger than lanthanide-oxygen bond-valence parameters. There are no obvious dependencies between the number of N atoms in the coordination sphere and the bond-valence parameter value.

Journal Article↗

PubMed2004

New bond-valence parameters for lanthanides.

The bond-valence method, especially the valence-sum rule, is very useful for checking if the structures formed by trivalent lanthanides are correct. In this work bond-valence parameters (Rij), which connect bond valences and bond lengths, have been computed for a large number of bonds taken from the Cambridge Structural Database, Version 5.24 (2002) [Allen (2002). Acta Cryst. B58, 380-388]. The calculated values of bond-valence parameters for metal-organic compounds decrease with an increase in lanthanide atomic number; the Rij values are also smaller than bond-valence parameters calculated for inorganic compounds. A summary of bond-valence sums calculated for Rij given in this work and reported in the literature, and a functional correlation between lanthanide-oxygen distances and coordination number are presented.

Journal Article↗

PubMed2004

New derivatives of quinazoline and 1, 2-dihydroquinazoline n3-oxide with expected antitumor activity.

Some derivatives of quinazoline and 1, 2-dihydroquinazoline N(3)-oxide were synthesised and their cytotoxic activities against human leukaemia HL-60 cells under hypoxic and aerobic conditions were tested and compared to tirapazamine as the reference compound. Compound 8 showed 5-fold higher toxicity under hypoxic conditions than in normal oxygen atmosphere. The structure of quinazoline derivatives was established by X-ray crystal structure analysis.

Antineoplastic Agents↗