Synthesis and Electronic Properties of Alkynylated Phenothiazines

Abstract Alkynylated phenothiazines 1 , 2 , 5 , 7 , and 12 − 15 can be synthesized in moderate to excellent yields by sequences of aldehyde−alkyne transformations and/or Sonogashira cross‐coupling reactions from suitable phenothiazine aldehydes or bromides. The electronic properties of (hetero)aryl ethynyl‐substituted N ‐methyl‐phenothiazines (UV/Vis absorption, fluorescence, redox potentials) strongly correlate with Hammett σ P parameters and indicate that remote substituents transmit their electronic information through π‐electron delocalization and the σ‐framework. Phenothiazinyl dyads ( 7g , 12 , 13 ) and triads ( 14 ) reveal different degrees of intramolecular electronic coupling as demonstrated by cyclic voltammetry, qualifying them as good model candidates for redox‐active molecular wires. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)