ZANCO Journal of Pure and Applied Sciences The official scientific journal of Salahaddin University-Erbil https://zancojournals.su.edu.krd/index.php/JPAS ISSN (print ):2218-0230, ISSN (online): 2412-3986, DOI RESEARCH PAPER Preparation and Characterization of Neodymium(III) arginine complex. Ary Bahman Faiq Department of Medical Laboratory, Technical College of Health, Sulaimani Polytechnic University, Sulaimani, Kurdistan Region, Iraq A B S T R A C T: A new complex of neodymium(III) arginine was prepared from Nd(NO 3 ) 3 .6H 2 O and arginine. The preparation involves mixing the metal-ligand by the ratio 1:2 dissolving both in H 2                       1:1. The 1 H-NMR spectrum of the complex observed a broadness attributed to the coordination of the paramagnetic metal with the ligand. In addition to, the comparison of vibrational spectra of free and coordinated arginine in the region of carbonyl, imine, and amino groups all indicated the occurrence of the complex. The Uv-vis spectra were also inspected where a new band appeared in the range of 240–270 nm assigned to the ligand metal charge transfer. KEY WORDS: lanthanide; neodymium; arginine; complex DOI: http://dx.doi.org/10.21271/ZJPAS.31.6.12 ZJPAS (2019) , 31(6);117-122 . 1. INTRODUCTION: Arginine has three functional groups (carboxyl, amine, and imine) each one can donate electrons to form hydrogen bonding or to metals having empty orbitals as shown in figure 1. Arginine exists in the structure of many enzymes. Arginine in one subunit has the ability of binding with another one and with substrates through hydrogen bonding (Wang et al. 2004; and Karsten and Cook 1993). In erythrocytes glycolysis pathway the enzyme bisphosphoglycerate mutase converts 1,3- biphosphoglycerate (1,3-BPG) to 2,3- biphosphoglycerate (2,3-BPG). This substrate 1,3- BPG binds with the enzyme at different amino acids in which arginine is one of them specially at the guanidinium site studied by (Garel et al. 1993), also quoted that "mutation in arginine89 resulted in significant perturbation in the enzyme's catalytic activity". A study made by Fairlie et al. (1997) on arginine complexes, the X-ray and NMR spectra showed that the guanidine group of arginine had contributed in the coordination with Co(III) and Pt (II) ions. The spectroscopic studies are quit helpful for interpreting the occurrence of the complex (Aiyelabola et al. 2012; and Martins et.al 2003). The arginine infrared spectrum shows bands of C=O stretching in the regions 1700 to 1660 cm -1 and NH deformation from 1650 to 1610 cm -1 (Kumar and Rai 2010; Muley et al. 2009; and Wang et al. 2014). Some of previous investigations of arginine complexes focused on bands shifting of carbonyl stretching around 1700cm -1 and of imine stretching around 1550cm -1 (Kong and Yu 2007; Ozturk et al. 2014; Wu et al. 2010; and Sunatkari et al. 2015) due to their interactions with metals. Furthermore, shifting in NH deformation band around 1630cm -1 of the arginine is another indicator taken for assessing the occurrence of the * Corresponding Author: Ary Bahman Faiq E-mail: ary.faiq@spu.edu.iq Article History: Received: 04/05/2019 Accepted: 05/08/2019 Published: 05/12/2019