Characterization of pentacyanoferrate(II) and -(III) complexes of adenosine and related aminopyridine ligands

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Title:	Characterization of pentacyanoferrate(II) and -(III) complexes of adenosine and related aminopyridine ligands
Authors:	Hung, C.H., Huang, H.Y., Liao, J.Y., Yeh, A.
Contributors:	Department of Chemistry, Tunghai University
Date:	1990
Issue Date:	2013-05-14T09:01:56Z (UTC)
Abstract:	A series of Fe(CN) 5L 3- complexes, where L = adenosine, 1-methyladenosine, tubercidin, and 2- and 3-aminopyridines, were prepared and characterized in aqueous solution. A metal to ligand charge-transfer transition was observed for complexes of adenosine (337 nm), tubercidin (340 nm), 2-aminopyridine (345 nm), and 3-aminopyridine (362 nm). Their corresponding Fe(III) complexes also display a ligand to metal charge-transfer absorption at 570 (adenosine), 635 (tubercidin), 655 (2-aminopyridine) and 695 nm (3-aminopyridine). The 1-methyladenosine complex of pentacyanoferrate(II) exhibits a band maximum at 375 nm, which is similar to that of imidazole complex. The rate constants of formation and dissociation were measured, and the k f and k d values (25°C, μ = 0.10 M (LiClO 4), pH = 8) are 269 M -1 s -1 and 9.70 × 10 -2 s -1 (adenosine), 257 M -1 s -1 and 0.612 s -1 (1-methyladenosine), 70.4 M -1 s -1 and 0.596 s -1 (tubercidin), 401 M -1 s -1 and 0.585 s -1 (2-aminopyridine), and 310 M -1 s -1 and 1.84 × 10 -3 s -1 (3-aminopyridine). Cyclic voltammetry of the complexes under study has shown that the oxidation is a one-electron reversible process with E 1/2 values of 0.49 (adenosine), 0.44 (tubercidin), 0.41 (2-aminopyridine), and 0.43 V (3-aminopyridine) vs. NHE at 25°C, μ = 0.10 M (LiClO 4), and pH = 8 (Tris). Both spectral and electrochemical results suggest that the coordination site of both Fe(CN) 5ado 3- and Fe(CN) 5ado 2- complexes is at N-1 of the nucleic acid and there is no linkage isomerization from N-1 to the exocyclic nitrogen when the metal center is oxidized from Fe(II) to Fe(III). ? 1990 American Chemie Society.
Relation:	Inorganic Chemistry Volume 29, Issue 16, 1990, Pages 2940-2944
Appears in Collections:	[Department of Chemistry ] Periodical Articles

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