Publication Details (including relevant citation information):
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Determining the structure and the chemical stability of polydentate coordinate complexes used in MRI contrast agents is essential in the field of diagnostic medicine. Chelation complexes using Gadolinium(III) metal, a paramagnetic Lanthanide, produce ideal signal intensities in diagnostic Magnetic Resonance Imaging (MRI) that has made its use in radiology a staple and also justify its importance for computational research. Gadolinium(III) complexes show variable
imaging qualities depending on the attached ligands to the central atom and the diagnostic application they are used for. Our study focuses on determining the structures and molecular properties of three ligands, MS-325-L, COPTA, and EOB-DTPA used in the preparation of the three Gd(III) complexes already used for clinical applications. Our calculations were performed using density functional theory (DFT) with the B3LYP functional applied in conjunction with two basis sets (3-21G and 6-31G) to obtain the equilibrium geometries, vibrational frequencies, and IR spectra for the ligands. The highest occupied molecular orbital (****) – lowest occupied molecular orbital (LUMO) energy gap values for all compounds are greater than 4 eV suggesting that the ligands are chemically stable. The ligands exhibit hydrogen bonding which can account for the significant chemical stability. The ligands possess significant dipole moments with values greaterthan 8 Debye, consistent with their chemical polar character. Our computed vibrational frequencies were found in excellent agreement with the experimental values, suggesting our proposed models are good representations of the actual molecular structures.
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