title: Trapping of muscle relaxant methocarbamol degradation product by complexation with copper(II) ion: spectroscopic and quantum chemical studies.
abstract: Structural properties of methocarbamol (Mcm) were extensively studied both experimentally and theoretically using FT IR, (1)H NMR, UV-Vis., geometry optimization, Mulliken charge, and molecular electrostatic potential. Stability arises from hyper-conjugative interactions, charge delocalization and H-bonding was analyzed using natural bond orbital (NBO) analysis. Mcm was decomposed in ethanol/water mixture at 80°C to guaifenesin [(RS)-3-(2-methoxyphenoxy)propane-1,2-diol] and carbamate ion [NH2COO(-)], where the degradation mechanism was explained by trapping the carbamate ion via the complexation with copper(II) ion. The structure of the isolated complex ([Cu(NH2COO)2(H2O)]⋅4H2O) was elucidated by spectral, thermal, and magnetic tools. Electronic spectra were discussed by TD-DFT and the descriptions of frontier molecular orbitals and the relocations of the electron density were determined. Calculated g-tensor values showed best agreement with experimental values from EPR when carried out using both the B3LYP and B3PW91 functional.
authors.affiliation: Chemistry Department, Faculty of Science, Cairo University, Gamaa Street, Giza 12613, Egypt. Electronic address: inorganic_am@yahoo.com.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Mansour
authors.affiliation: Chemistry Department, Faculty of Science, Cairo University, Gamaa Street, Giza 12613, Egypt.
authors.forename: Ola R
authors.initials: OR
authors.lastname: Shehab
mesh_terms: D003300:Copper / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008721:Methocarbamol / Q000737:chemistry*; D009125:Muscle Relaxants, Central / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods
chemical_list: D009125:Muscle Relaxants, Central; D008721:Methocarbamol; D003300:Copper
keywords: Copper complex; EPR; Methocarbamol; NBO; TD-DFT