Binary and Mixed-Ligand Complexes of Creatinine and L-Asparagine with First-Row Transition Metal Ions: Potentiometrie Studies

Abstract

Creatinine is a physiological component of blood, brain and muscles and an important bioligand, which is the last product of the nitrogen metabolism in the vertebrates. In this study , the stability constants of binary complexes formed by creatinine with Cu(II), Co(II), Mn(II), Cr(III), and of the mixedligand complex Cu(II)-creatinine-l-asparagine were determined by the Calvin-Bjerrum and Irving-Rossotti methods. The protonation constant and dissociation constant of creatinine was found to be 4. 90 at 25 C and for 1= 0.1.The conditional formation constants and the formation pH ranges of complexes were determined. Relative abundance was plotted using conditional formation constants of the complexes and the steps of the complexes are shown in graphs. The composition of metal-creatinine complexes was determined as metal/ligand = 1:1. ligand Brought to you by | Purdue University Libraries Authenticated Download Date | 5/29/15 4:54 AMVol . 25, No. 4, 2005 Binary and Mixed-Ligund Complexes of Creatinine renal function. The latter participates in energy flow in muscle tissues and is present in blood, muscles and the brain /l, 2/. The complexation ability of creatinine is well recognised and studies on the metal ion interactions with creatinine may be helpful in deciphering creatinine metabolic pathways /2, 3, 4, 5, 6, 7/. The study of binary and ternary complexes of this ligand should be of interest, due to the fact that creatinine metabolism might be connected with its complexation to different metal ions /8/. Five co-ordination modes have been established by X ray crystallography: bidentate bridging through N(l)(ring) and deprotonated exocyclic NH site 191, bidentate binding via N(l) (ring) and the exocyclic 0(C=0) /10/; monodentate binding through the N(l)(ring)site /11/; monodentate binding through the exocyclic 0(C=0)(12); and monodentate fashion through the deprotonated exocyclic NH group /10/. Creatinine is soluble in water and in aqueous solution it shows acidic properties(pKa =4, 89 ). L-asparagine is an amino acid which largely exists in several plants. CH, /Ν NH -NH M-(2 Ο N-fe-C-Chfe-CH-COCH Creatinine L-asparagine In the present study, the stability constants of creatinine and l-asparagine complexes with Cu(II), Co(II), Mn(II), Cr(III) were determined using Potentiometrie method by the Calvin-Bjerrum and Irving-Rossotti Procedure /13/. The conditional formation constants depending on pH values were calculatedi The mole fractions of different species from mixed compound were investigated using calculated conditional formation constants /14/. The protonation constants and the acid constants of l-asparagine and creatinine which were used as ligands were taken from the.literature /15,16/. The formation constants of Cu(II)-creat, Co(II)-creat, Mn(II)-creat and Cr(III)-creatinine complexes were found, as well as those for Cu(II), Co(II) and Mn(II) with L-asparagine. In addition, the formation of metal-Lasparagine-creatinine mixed-ligand complexes was proven.388 Brought to you by | Purdue University Libraries A...