Abstract

The reaction between N,N-dimethylaminoethanol (dmaeH) and nickel(II) acetylacetonate, [Ni(acac)₂]₃ or Ni(II) acetate tetrahydrate, [Ni(CH₃CO₂)₂(H₂O)₄] yields the new complexes [Ni(acac)₂(dmaeH)] (1) and [Ni(CH₃CO₂)₂(dmaeH)₂] (2). Complexes (1) and (2) are mononuclear, containing six-coordinate Ni(II) atoms in slightly distorted octahedral environments. Complex (1) contains two bidentate and chelating acetylacetonate groups with a chelating dmaeH ligand. Complex (2) contains two monodentate acetate groups in a cis configuration and two chelating dmaeH ligands. Both complexes dissolve readily in dmaeH to form stable solutions, and are good precursors for the deposition of NiO thin films by sol–gel techniques. (1) and (2) were successfully used to grow electrochromic NiO thin films on conductive glass substrates. The surface morphology of the films was characterised by scanning electron microscopy (SEM) and atom force microscopy (AFM). The thin film performances were characterised by means of optical (transmittance) and electrochemical (cyclic voltammetry) methods. Upon cycling, the NiO thin films switch from brown to transparent in a reversible way exhibiting anodic electrochromic performance.