Abstract The photophysical and electrochemical properties of p-phenylenediamine (PPD) are strongly affected by the addition of cyano groups to the aromatic ring. In 2, 3, 5, 6- tetracyano-p-phenylenediamine (TCPPD) the photophysics is governed mostly by the solvent basicity (β) whereas in 2, 6-dicyano-N, N, N′, N′-tetramethyl-p-phenylenediamine (DCTMPPD) by the solvent polarity/polarizability (π*). In order to study the interactions of ...