title: Assemblies of salen-type oxidovanadium(IV) complexes: substituent effects and in vitro protein tyrosine phosphatase inhibition.
abstract: Oxidovanadium(IV) complexes with substituted chiral tetradentate dianionic N,N'-bis-o-hydroxybenzylidene-1,2-propylenediamines were synthesized and their physicochemical properties were characterized using single crystal X-ray diffraction, elemental analysis, ATR FTIR, UV-VIS and EPR spectroscopy, cyclic voltammetry, spectroelectrochemistry and preliminary in vitro protein-tyrosine phosphatase inhibition activity studies. Different 5-substituents in the salicylaldehyde (condensed with 1,2-diaminopropane; 2 : 1) were tested, namely 5-Br (complex 1), 5-Cl (2), 5-NO2 (3) and 5-OCH3 (4). The crystal structures of 1 and 2 show square pyramidal coordination of vanadium and parallel arrangement of monomeric exo isomers in supramolecular dimers. The halogen-halogen interaction of substituents in 5,5'-positions leads to weakening of axial interaction between phenolate O and V in 2, compared to 1. The Br atom takes part in halogen bonding with a vanadyl group in 1. Complex 3 has a linear polymeric structure with a V-O-V asymmetric bridge motif (IR absorption band at 873 cm(-1), separated d-d bands and broad EPR band structure in frozen solution pointing to oligomeric nature) while 4 is monomeric (V=O stretching at 976 cm(-1), broad d-d band structure). Redox potentials of the V(4+)/V(5+) couple lie in the range of -0.14 to 0.21 V (vs. Fc/Fc(+)) and show substantial dependence on the electron withdrawing properties of the substituents. The charge transfer character of the bands present in the range 365-395 nm was confirmed based on UV-VIS spectroelectrochemical experiments. Different assemblies of complex molecules are influenced by the electron withdrawing properties of the 5,5'-substituents, leading to supramolecular dimers (1, 2 and 4) and linear polymeric self-assembly (3). An in vitro study of representative complex 1 showed protein tyrosine phosphatase activity inhibition higher than that of suramin but lower than those of oxidovanadium(IV) sulphate and bis(maltolato)oxidovanadium(IV).
authors.affiliation: Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland. zabierow@chemia.uj.edu.pl.
authors.forename: Piotr
authors.initials: P
authors.lastname: Zabierowski
authors.forename: Janusz
authors.initials: J
authors.lastname: Szklarzewicz
authors.forename: Ryszard
authors.initials: R
authors.lastname: Gryboś
authors.forename: Barbara
authors.initials: B
authors.lastname: Modryl
authors.forename: Wojciech
authors.initials: W
authors.lastname: Nitek
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D055664:Electrochemical Techniques; D004578:Electron Spin Resonance Spectroscopy; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D005029:Ethylenediamines / Q000737:chemistry*; D006860:Hydrogen Bonding; D020128:Inhibitory Concentration 50; D008968:Molecular Conformation; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D014639:Vanadium / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D004791:Enzyme Inhibitors; D005029:Ethylenediamines; D014639:Vanadium; C011452:disalicylaldehyde ethylenediamine; D017027:Protein Tyrosine Phosphatases