OJIC  Vol.3 No.1 , January 2013
Synthesis, characterization, and stability of iron (III) complex ions possessing phenanthroline-based ligands
Abstract: It has previously been demonstrated that phenanthroline-based ligands used to make gold metallotherapuetics have the ability to exhibit cytotoxicity when not coordinated to the metal center. In an effort to help assess the mechanism by which these ligands may cause tumor cell death, iron binding and removal experiments have been considered. The close linkage between cell proliferation and intracellular iron concentrations suggest that iron deprivation strategies may be a mechanism involved in inhibiting tumor cell growth. With the creation of iron (III) phen complexes, the iron binding abilities of three polypyridal ligands [1,10-phenanthroline (phen), 2,9-dimethyl-1, 10-phenanthroline (methylphen), and 2,9-di-sec-butyl-1, 10-phenanthroline (sec-butylphen)] can be tested via a competition reaction with a known iron chelator. Therefore, iron (III) complexes possessing all three ligands were synthesized. Initial mass spectrometric and infrared absorption data indicate that iron (III) tetrachloride complex ions with protonated phen ligands (RphenH+) were formed: [phenH][FeCl4], [methylphenH][FeCl4], [sec-butylphenH][FeCl4]. UV-vis spectroscopy was used to monitor the stability of the complex ions, and it was found that the sec-butylpheniron complex was more stable than the phen and methylphen analogues. This was based on the observation that free ligand was observed immediately upon the addition of EDTA to the [phenH][FeCl4] and [methylphenH] [FeCl4] complex ions.
Cite this paper: Tosonian, S. , J. Ruiz, C. , Rios, A. , Frias, E. and Eichler, J. (2013) Synthesis, characterization, and stability of iron (III) complex ions possessing phenanthroline-based ligands. Open Journal of Inorganic Chemistry, 3, 7-13. doi: 10.4236/ojic.2013.31002.

[1]   Wein, A.N., Stockhausen, A.T., Hardcastle, K.I., Saadein, M.R., Peng, S., Wang, D. and Eichler, J.F. (2011) Tumor cytotoxicity of 5,6-dimethyl-1,10-phenanthroline and its corresponding gold (III) complex. Journal of Inorganic Biochemistry, 105, 663-668. doi:10.1016/j.jinorgbio.2011.01.006

[2]   Sun, R. and Che, C. (2009) The anti-cancer properties of gold (III) compounds with dianionic porphyrin and tetradentate ligands. Coordination Chemistry Reviews, 253, 1682-1691. doi:10.1016/j.ccr.2009.02.017

[3]   Messori, L., Abbate, F., Marcon, G., Orioli, P., Fontani, M., Mini, E., Mazzei, T., Carotti, S., O’Connell, T. and Zanello, P. (2000) Gold (III) complexes as potential antitumor agents: Solution chemistry and cytotoxic properties of some selected gold (III) compounds. Journal of Medicinal Chemistry, 43, 3541-3548. doi:10.1021/jm990492u

[4]   Cinellu, M.A., Maiore, L., Manassero, M., Casini, A., Arca, M., Fiebig, H.-H., Kelter, G., Michelucci, E., Pieraccini, G., Gabbiani, C. and Messori, L. (2010) [Au2 (phen2Me)2(μ-O)2](PF6)2, a novel dinuclear gold (III) complex showing excellent antiproliferative properties. ACS Medicinal Chemistry Letters, 1, 336-339.

[5]   Hudson, Z.D., Sanghvi, C.D., Rhine, M.A., Ng, J.J., Bunge, S.D., Hardcastle, K.I., Macbeth, C. and Eichler, J.F. (2009) Synthesis and characterization of gold (III) complexes possessing 2,9-dialkylphenanthroline ligands: to bind or not to bind? Dalton Transactions, 28, 7473-7480. doi:10.1039/b823215f

[6]   Richardson D.R., Tran, E.H. and Ponka, P. (1998) The potential of iron chelators of the pyridoxal isonicotinoyl hydrazone class as effective antiproliferative agents. Blood, 86, 4295-4306.

[7]   Satterfield, M. and Brodbelt, J.S. (2001) Relative binding energies of gas-phase pyridyl ligand/metal complexes by energy-variable collisionally activated dissociation in a quadrupole ion trap. Inorganic Chemistry, 40, 5393-5400. doi:10.1021/ic010356r

[8]   Pallenberg, A. J., Koenig, K. S. and Barnhart, D. M., (1995) Synthesis and characterization of some copper (I) phenanthroline complexes. Inorganic Chemistry, 34, 2833-2840. doi:10.1021/ic00115a009

[9]   Kulkarni, P., Padhye, S. and Sinn, E. (1998) Communication:: The first well characterized Fe (phen) Cl3 complex: structure of aquo mono(1,10-phenanthroline) iron (III) trichloride: [Fe (phen) Cl3 (H2O)]. Polyhedron, 17, 2623-2626. doi:10.1016/S0277-5387(97)00515-9

[10]   Hara, Y. and Akiyama, M. (2001) An iron reservoir model based on ferrichrome:? Iron (III)-binding and metal (III)-exchange properties of tripodal monotopic and ditopic hydroxamate ligands with an l-alanyl-l-alanyl-n-hydroxy-β-alanyl sequence. Journal of the American Chemical Society, 123, 7247-7256. doi:10.1021/ja003251g

[11]   Khavasi, H.R., Amani and V., Safari, N. (2008) (2,2’-Biquinoline-2N,N’)dichloridoiron(II). Zeitschrift für Kristallographie—New Crystal Structures, 223, 41-42.

[12]   Eckenhoff, W.T., Biernesser, A.B. and Pintauer, T. (2012) Structural characterization and investigation of iron (III) complexes with nitrogen and phosphorus based ligands in atom transfer radical addition (ATRA). Inorganica Chimica Acta, 382, 84-95. doi:10.1016/j.ica.2011.10.016

[13]   Amani, V., Nasser, S., Khavasi, H.R. and Mirzaei, P. (2007) Iron (III) mixed-ligand complexes: Synthesis, characterization and crystal structure determination of iron (III) hetero-ligand complexes containing 1,10-phenanthroline, 2,2’-bipyridine, chloride and dimethyl sulfoxide, [Fe(phen)Cl3(DMSO)] and [Fe(bipy)Cl3(DMSO)]. Polyhedron, 26, 4908-4914. doi:10.1016/j.poly.2007.06.038

[14]   Gomer, R. and Inghram, M.G. (1955) Applications of field ionization to mass spectrometry. Journal of the American Chemical Society, 77, 500. doi:10.1021/ja01607a096