Charge Carrier Mobility of Phenothiazine Functionalized TCBD Derivatives of Naphthalimide

AbstractA set of naphthalimide functionalized push–pull chromophores NPI 1–3 were designed and synthesized via Pd‐catalyzed Sonogashira cross‐coupling followed by [2 + 2] cycloaddition‐electrocyclic ring‐opening reaction. The 1,8‐naphthalimide (NPI) and 1,1,4,4‐tetracyanobuta‐1,3‐diene (TCBD) moiety acts as an acceptor unit, whereas phenothiazine (PTZ) unit acts as a donor unit. Their photophysical, electrochemical properties, and charge carrier mobilities were investigated. Density functional theory (DFT) and TD‐DFT calculations were performed on NPI 1–3 to analyze the molecular geometry, frontier molecular orbitals, molecular electrostatic potentials (MEPs), and electronic transitions related to their absorption spectra. The incorporation of cyano‐based strong electron acceptor TCBD in the phenothiazine functionalized naphthalimide derivatives NPI1 resulted in TCBD incorporated chromophore NPI 2–3 which exhibits red‐shifted electronic absorption spectra in the near IR region. The electrochemical properties reveal that the naphthalimide derivatives NPI 1–3 exhibit multiple redox waves, attributed to the presence of NPI and TCBD acceptor units and phenothiazine donor units. The measured hole and electron mobilities for NPI 1–3 are 4.06 × 10−3 and 3.16 × 10−3 cm2 V−1 s−1, 7.5 × 10−3 and 4.48 × 10−3 cm2 V−1 s−1, 6.76 × 10−3 and 3.1 × 10−3 cm2 V−1 s−1, respectively, obtained by space‐charge limited current (SCLC) measurements.