EXPERIMENTAL AND THEORETICAL DETERMINATION OF ELECTRONIC-PROPERTIES IN L-DOPA

(2S)-3-(3',4'-Dihydroxyphenyl)alanine (L-dopa), C9H11-NO4,M(r)=197.9, monoclinic, P2(1), a=13.619(6), b=5.232(2), c=6.062(3)Angstrom, Beta=9 7.56(4)(o), V=428.191 Angstrom(3), Z=2, D-x=1.529g cm(-3), D-m=1.515g cm(-1) (T=293 K), Lambda(MoK Alpha)=0.71069 Angstrom, Mu=1.2 cm(-1), F (000)=208, T=173 K, R(F)=0.017 for 4208 reflections with sin Theta/Lam bda<1.078 Angstrom(-1). The electron distribution has been determined by multipole refinement with the Hansen/Coppens aspherical scattering factor expansion, including multipole terms up to octopoles for C,N an d O and up to dipoles for H. The molecular dipole moment was determine d as 12(2)D, within as esd of the ab initio value reported here of 11D . The bond critical-point properties of the total electron density wer e determined, giving negative values for rectangle(2) Rho(c) consisten t with covalent bonds, and are in fair agreement with the ab initio re sults. An analysis of the hydrogen-bond critical points gave small pos itive rectangle(2) Rho values, consistent with ionic, closed-shell int eractions between the participating atoms. A set of theoretical struct ure factors was generated from the ab initio charge distribution and s ubjected to multipole refinement, to enable a more detailed comparison with experiment.