Striking effects of cobalt (III) nuclearity in fused salphen complexes on their electroconductivity and thin film transistor activity

Dinuclear and trinuclear cobalt (III) complexes were prepared using fused salphen ligands that have the same number of benzene rings along the major axis of the molecules. The two compounds were used as organic thin film formed on a glass or a SiO₂/n-Si substrate for investigating electronic conductivity and transistor characteristics, respectively. The conductivity of di- and trinuclear complexes were 8.5 × 10⁻⁵ and 5.8 × 10⁻³ S cm⁻¹, meaning that the increment of the nuclearity from two to three resulted in multiplication of 70 times. The thin film of the trinuclear complex showed a faint transistor activity, where the thin film act as n-type semiconductor. In contrast, the dinuclear complex did not afford a detectable response to the gate voltage.