The effects of carbon chains placed on the electron-accepting P atom of a P center dot center dot center dot N bond are examined via ab initio calculations. Saturated alkyl groups have a mild weakening effect, regardless of chain length. In contrast, incorporation of double bonds into the chain strengthens the interaction, C equivalent to C triple bonds even more so. These effects are only slightly enhanced by additional conjugated double bonds or an aromatic ring. Placing F atoms onto the carbon chains strengthens the P center dot center dot center dot N bond, but only by a small amount, which wanes as the F atom is displaced further from the P along the chain. (C) 2012 Elsevier B. V. All rights reserved.