Creatinine (2-amino-1-methyl-5H-imidazol-4-one) is an amino acid that occurs in vertebrate tissues and in urine. The mid and far infrared spectra of creatinine were recorded in the solid phase. The optimized structure of creatinine was obtained using DFT/B3LYP method with 6-311+G(d,p) and LANL2DZ basis sets. The harmonic frequencies of creatinine were calculated using DFT/B3LYP/6-311+G(d,p) method. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The creatinine-metal {cadmium [Cd(II)], zinc [Zn(II)] and mercury [Hg(II)]} halogen [chloride (Cl-) and bromide (Br-)] complexes were synthesized. DFT calculations, DFT-B3LYP/LANL2DZ were performed for the determination of geometrical structure and vibrational assignment for metal- complexes.