Synthesis, molecular structure (X-ray and DFT), and solution behavior of titanium 4-Acyl-5-pyrazolonates. Correlations with related antitumor beta-diketonato derivatives

Inorg Chem. 2007 Sep 3;46(18):7553-60. doi: 10.1021/ic700935x. Epub 2007 Aug 11.

Abstract

Previously reported structure-activity relationships have shown two features for effective antitumor activity of titanium beta-diketone complexes: (a) ligand asymmetry and (b) the presence of planar substitutents on the ligand. Mono- and dinuclear derivatives, studied with diffraction and DFT methods show that (a) is consistent with different Ti-O(beta-diketonato) bond lengths, which are longer than Ti-O(oxo) and Ti-O(alkoxy) ones. pi-pi features observed in dinuclear derivatives correlate with strong reactivity of related complexes with DNA and support DNA intercalation by such planar groups, in agreement with (b). Large variation for Ti-O bond lengths and Ti-O-C bond angles in the ethoxy moiety is associated with the titanium withdrawing effect and oxygen bonding s character; it is confirmed through exploration of the Cambridge crystallographic database. This ethoxy geometrical flexibility also suggests versatile accommodation in protein pockets and/or other biological targets. Electrospray ionization mass spectrometry (ESI-MS) spectra show formation of di- and trinuclear Ti-4-acyl-5-pyrazolonato cationic oligomers. Hydrolysis/oligomerization is also described by NMR results.

MeSH terms

  • Acylation
  • Antineoplastic Agents / chemical synthesis*
  • Antineoplastic Agents / chemistry
  • Crystallography, X-Ray
  • Hydrogen / chemistry
  • Ketones / chemical synthesis
  • Ketones / chemistry*
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Molecular Structure
  • Oxygen / chemistry
  • Piperidines / chemical synthesis
  • Piperidines / chemistry*
  • Titanium / chemistry*

Substances

  • Antineoplastic Agents
  • Ketones
  • Piperidines
  • Hydrogen
  • Titanium
  • Oxygen