Large π‐Conjugated Chromophores Derived from Tetrathiafulvalene

Abstract

AbstractA large π‐conjugated chromophore composed of two dipyrido[3,2‐a:2′,3′‐c]phenazine units directly fused to the central tetrathiafulvalene core has been prepared as a bridging ligand and its strong binding ability to Ru2+ to form a new dinuclear complex is presented. The electronic absorption and luminescence spectra and the electrochemical behavior of the free ligand and the Ru2+ complex have been investigated in detail. The free ligand shows a very strong band in the UV region consistent with ligand‐centered π–π* transitions and an intense broad band in the visible region that corresponds to an intramolecular charge‐transfer (ILCT) transition. Upon coordination, a metal‐to‐ligand charge‐transfer band appears at 22520 cm−1, and the ILCT band is bathochromically shifted by 1620 cm−1. These electrochemically amphoteric chromophores have also been characterized by spectro‐electrochemical methods. The oxidized radical species of the free ligand show a strong tendency to undergo aggregation, in which long‐distance attractive interactions overcome the electrostatic repulsion. Moreover, these two new chromophores reveal an ILCT fluorescence with large solvent‐dependent Stokes shifts and quantum efficiencies of 0.052 for the free ligand and 0.016 for its dinuclear Ru2+ complex in CH2Cl2.