A model of a copper-dioxolene complex linked to Au( 1 1 1) surface with butanethiol linker is investigated using first-principles methods. It is shown that the complex adsorbed at the surface may appear in various locally stable structural forms differing in electron charge and spin density distribution, the symmetric high spin (HS) one and the twisted low spin (LS) structure. The electric field directed perpendicular to the surface controls the amount of the charge transfer between the complex and the substrate, starting from the zero-field value of Q= +0.18 vertical bar e vertical bar up to the value of Q= +0.94 vertical bar e vertical bar for the field strength of E = 0.5 V/angstrom. The field modifies also the mutual stability of the two structural forms, reducing the energy gap between the more energetically stable LS twisted form and the symmetrical HS one, from a value of Delta similar to 0.29 eV in absence of the field to Delta similar to 0.11 eV for the field strength of E = 0.35 V/angstrom. (C) 2015 Elsevier B.V. All rights reserved.