2 research outputs found
Towards understanding mode of action of L-dopa and carbidopa: DFT/TD-DFT analyses of their electronic and vibration spectra
1378-1386<span style="font-size:11.0pt;font-family:
" times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi"="" lang="EN-GB">The electronic absorption and vibrational spectra of L-dopa (LD) and carbidopa
(CD) have been measured experimentally in different solvents and also computed
theoretically. FTIR spectra of LD and CD have been computed theoretical at the
B3LYP/6-311++G** level of theory. <span style="font-size:
11.0pt;font-family:" times="" new="" roman","serif";mso-fareast-font-family:calibri;="" mso-bidi-font-family:mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;="" mso-bidi-language:hi"="" lang="EN-GB">A scaling factor of 0.95 results in good correspondence
between calculated and experimental spectra. Vibrational modes have been
assigned and similarities and differences between the FTIR spectra of LD and CD
are discussed. Two IR marker bands have been identified for CD. Based on TD-DFT/TPSSh
calculations, the leading transitions contributing to the electronic absorption
of LD and CD are proposed. These findings have been discussed in the context of
the experimentally observed spectra reported for LD and CD in different
solvents. NTO analyses clearly indicate that most of the leading transitions in
LD and partially in CD involve a sizable charge transfer from the aromatic
catechol moiety to the aliphatic amino acid side chain. The short wavelength
transition, however, shows an opposite trend.</span