Research Interests
 

Our research is mainly focused on understanding the local environment around metal ions in solution and solid state, as well as sulfur speciation. X-ray absorption spectroscopy (EXAFS) provides information on the bond distance and the type of coordinating atoms. Complementary information is obtained using e.g., multi-nuclear NMR, vibrational spectroscopy and theoretical calculations.

 

 

 

1) Heavy-metal complex formation with small thiol-containing molecules of biological interest

 

Accumulation of heavy metal ions in the environment causes adverse health effects. “Soft” metal ions have a high affinity for thiol (-SH) groups, in e.g., amino acid L-cysteine (H2Cys), the cysteine-rich protein metallothionein, and tripeptide glutathione (GSH = g-Glutamyl-Cysteine-Glycine), which is the most abundant cellular thiol in the body and has important in vivo functions for protection against heavy metal ions. Uptake via food, drinking water and air of Hg(II), Pb(II) and Cd(II) can affect human metabolism by blocking enzymatic functions. Thiol-containing drugs, e.g. D-penicillamine (H2Pen = 3,3´-dimethylcysteine), are clinically used for heavy metal detoxification.

     We have applied a novel combination of different spectroscopic methods such as multi-nuclear NMR, EXAFS and vibrational spectroscopy for investigating the coordination of such metal ions to glutathione, cysteine and its derivatives, to elucidate the structure of their complexes, and to evaluate the distribution of these species in aqueous solution. The information on structure and bonding of heavy metal complexes with such thiol-containing small molecules can assist us to design new chelating agents/ drugs with improved efficiency for detoxification by increasing their bonding efficiency.

(Ref: V. Mah and F. Jalilehvand*, J. Biol. Inorg. Chem., 2008, 13, 541- 553  and

 F. Jalilehvand*, B. O. Leung and V. Mah, Inorg. Chem. 2009, 48, 5758 - 5771)

 

2) Solvation of metal ions

We recently studied Mo(V) aqua-chloro complexes in hydrochloric acid (1.7 -9.4 M) solutions by means of Mo K- and L2,3-edge X-ray absorption and Raman spectroscopic methods. In 0.2 M solutions of MoCl5 in 7.4 to 9.4 M HCl the mononuclear, green complex [MoOCl4(OH2)]- dominates. The Mo K-edge EXAFS spectrum for 0.2 M MoCl5 in 1.7 M HCl solution reveals a dinuclear, red complex [Mo2O4Cl6-n(OH2)n]n-4 (n = 2, 3) with a double oxygen bridge and the average distances Mo=O 1.67(2) Å, Mo-(m-O) 1.93(2) Å, Mo-Cl 2.47(3) Å, Mo-Mo 2.56(2) Å, and a short Mo-OH2 distance of 2.15(2) Å, which implies at least one of the aqua ligands in equatorial position relative to the two axial Mo=O bonds. This position differs from the Mo-OH2 configuration exclusively trans to the M=O groups of the isomeric (with n = 2) dinuclear complex in crystalline [Mo2O4Cl4(OH2)2]2-. The difference in the ligand field is also reflected in their L2,3-edge XANES spectra.

(Ref: F. Jalilehvand*, V. Mah, B. Leung, et al, Inorg. Chem. 2007, 46, 4430-4445) 

 

          We also investigated the structures of [Pt(H2O)n]2+ ion and cis-[Pt(NH3)2(H2O)m]2+ complex, as one of the active forms of the anti-tumor drug cis-platin, which inhibits cell division. When entering a cellular environment, the drug cis-platin, cis-diamminedichloroplatinum(II), is activated by substitution of one or both chloro-ligands with water molecules. Structural information for hydrated platinum(II) species including the hydration products of cis-platin is essential for a better understanding of its reaction mechanism. Our results show that in the above hydrated Pt(II) complexes, there are four tightly bonded Pt-O/N bonds at 2.01(2) Å, as well as one (or two) weakly bonded axial water molecule(s) at 2.4 Å. This result provides a new basis for theoretical computational studies aiming to connect the function of the anti-cancer drug cis-platin to its ligand exchange reactions, where usually four-coordinated square planar platinum(II) species are considered as the reactant and product.

(Ref: F. Jalilehvand* and L. J. Laffin, Inorg. Chem. 2008, 47, 3248- 3254      and

L. Kocsis, J. Mink,* F. Jalilehvand, L. J. Laffin, et al., J. Raman Spectrosc. 2009, 40, 481 - 490)

 

 

 

3) Sulfur speciation in waterlogged wood of historical shipwrecks

 

We applied sulfur K-edge XANES, for the first time, to marine-archaeological wood samples, and could reveal the cause of a severe problem for such artefacts. Sulfate salt formation had been observed on the 17th century shipwreck of the warship Vasa in Stockholm, Sweden. The sulfur XANES spectra showed that a large amount of elemental sulfur, stored in the moist wood, was being oxidized to sulfuric acid, causing wood deterioration.

(Ref: M. Sandström*, F. Jalilehvand, et al., Nature, 2002, 145, 893-897).

 

      We also studied other artifacts and shipwrecks such as the Mary Rose (England), the Batavia (Western Australia) and the Bremen Cog (Germany), to study how general the sulfur problem is, and the role of sulfides such as pyrite in this process.

(Ref: M. Sandström*, F. Jalilehvand, et al., PNAS 2005, 102, 14165-14170).

 

 

 

4) Sulfur speciation in plant leaves

Sulfur is ubiquitous with important functions in nature. While the total sulfur concentration can be easily determined, revealing the mechanisms of the transformation of sulfur species in a large number of valence states, from –II in sulfides to +VI in sulfates, and the mechanisms of the transformation processes that sulfur undergoes represent a real challenge.

      One interesting aspect is sulfur speciation in fresh leaves and trees. Two sources of sulfur are available to plants: sulfate ions from the soil, and SO2 and H2S from the air, entering the leaves via stomata. Different mechanisms have been proposed for the assimilation of sulfur compounds. Characterization of the intermediates is of great importance for understanding the sulfur metabolism and this will be achieved using sulfur XANES spectroscopy on the plant leaves. Also, the effects of excess sulfur pollutant gases, such as SO2, will be studied using sulfur XANES spectroscopy.

(Ref: F. Jalilehvand in “Sulfur Transport and Assimilation in Plants in the Post Genomic Era”, Eds. K. Saito, L. J. De Kok, et al., Backhuys Publishers, 2005, pp. 53-57)

 

 

 

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