Synthesis and Characterization of New Self-Assembled Metallo-Polymers Containing Electron-Withdrawing and Electron-Donating Bis(terpyridine) Zinc(II) Moieties

Abstract

A series of rigid π-conjugated bis(terpyridines) (M1−M7) bearing electron-acceptor spacer units in 4′-position was synthesized in moderate to high yields by Pd0-catalyzed Sonogashira cross-coupling reactions. The compounds were fully characterized by NMR spectroscopy, MALDI−TOF mass spectrometry, elemental analysis and their photophysical properties were discussed in detail. These new bis(terpyridines) were applied for the self-assembly reaction with ZnII ions to form metallo-homo polymers (P1−P7). Broadened NMR signals and UV−vis titration experiments confirmed the successful polymerization. The electro-optical properties of the materials were investigated in detail. Band gaps up to 2.08 eV and bright blue to orange photoluminescence with quantum yields of 18 to 66% were observed strongly depending on the nature of the π-conjugated bis(terpyridine) system. In combination with electron-donor ditopic terpyridine ligands (MD1 and MD2), two ZnII random copolymers (R1 and R2) were synthesized. These materials were investigated by UV−vis absorption and photoluminescence experiments in dilute solution and in the solid state, prepared by spin-coating from DMF solutions. Thereby, random copolymer R2 featured an energy transfer from the donor to the acceptor part in dilute solution