A cyclic voltammetric study on Np(IV) complexes with task-specific ionic liquid with 3-dodecylimidazolium cation appended with diphenylcarbamoylmethylphosphine oxide and bis(trifluoromethyl-sulfonyl)-imide anion dissolved in the room temperature ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide has been carried out. The results are compared with its molecular entity, viz., octyl(phenyl)carbamoylmethylphosphine oxide dissolved in the same diluent. The diffusion coefficient values were determined using its variation with scan rate. The standard rate constant values were also computed. The activation energy for diffusion and thermodynamic parameters for the redox reactions of the Np complexes were determined and compared.