Intense Ground-State Charge-Transfer Interactions in Low-Bandgap, Panchromatic Phthalocyanine-Tetracyanobuta-1,3-diene Conjugates

摘要

A cycloaddition-retroelectrocyclization reaction between tetracyanoethylene and two zinc phthalocyanines (Zn(II)Pcs) bearing one or four anilino-substituted alkynes has been used to install a strong, electron-accepting tetracyanobuta-1,3-diene (TCBD) between the electron-rich (ZnPc)-Pc-II and aniline moieties. A combination of photophysical, electrochemical, and spectroelectrochemical investigations with the (ZnPc)-Pc-II-TCBD-aniline conjugates, which present panchromatic absorptions in the visible region extending all the way to the near infrared, show that the formal replacement of the triple bond by TCBD has a dramatic effect on their ground- and excited-state features. In particular, the formation of extremely intense, ground-state charge-transfer interactions between (ZnPc)-Pc-II and the electron-accepting TCBD were observed, something unprecedented not only in Pc chemistry but also in TCBD-based porphyrinoid systems.