Terpyridine-fused polyaromatic hydrocarbons generated via cyclodehydrogenation and used as ligands in Ru(ii) complexes

Abstract

A series of novel fused 4′-substituted 2,2′ : 6′,2′′-terpyridine ligands and their ruthenium(II) complexes were prepared. The unusual 4′-substituents comprised 2,3,4,5-pentaphenylbenzene and its tert-butyl derivative (1 and 2) and the products from oxidative cyclodehydrogenation, i.e. polyaromatic fragments consisting of ten or thirteen fused benzene rings (3 and 4). The syntheses of all the ligands are discussed in terms of the demands and limitations of the Scholl reaction. The optical properties of the ligands, along with the single-crystal X-ray structures of 1 and 2, are presented. The latter show that the pentaphenylbenzene and terpyridine appendages of 1 and 2 are perpendicular in the solid state. Despite the inclusion of the large organic chromophore the absorption and emission properties of the Ru(II) bis-terpy complexes (of ligands 1, 2 and 3) were found to be comparable to those of [Ru(terpy) 2 ] 2+ . They are non-emissive at room temperature but emit at 77 K with excited state lifetimes of 11-12 μs.

Methoxy functionalisation: exerting synthetic control of the supramolecular and electronic structure of nitrogen-doped nanographenes

“…long chain alkyl substituted hexaperihexabenzocoronenes frequently exhibit liquid crystalline behaviour, 2 whereas their iodo-or tert-butyl-functionalised derivatives give rise to Bernal-stacked crystalline dimers. 23 This work reveals how the combination of heteroatom doping (as pioneered by Draper et al), 17,[24][25][26] with H-bonding peripheral substituents, can unlock some exciting new applications for nanographene materials by controlling the outcome of the synthetic process and the HOMO-LUMO gaps and intermolecular order of the end-products.…”

“…both partially and fully fused species tend to be generated in a single reaction. [18][19][20] Electron donating substituents both direct and promote CC bond formation under cyclodehydrogenation conditions. 21,22 Tuning the intramolecular properties of graphenes is one step in the search for technology-enabling materials.…”

Pyridinic Nanographenes by Novel Precursor Design

“…Pyridine analogues of HBC however, proved to be difficult to synthesise (Figure 1). [5] Most defined, solution‐synthesized nanographenes are made from polyphenylene precursors that are planarized via oxidative cyclodehydrogenation or Scholl‐type reactions [1a, 2b, 6] . This procedure often fails for electron poor aromatics such as pyridines [7] .…”

Varying numbers and positions of carboxylate groups on Ru dyes for dye-sensitized solar cells: uptake on TiO2, cell performance and cell stability

“…Emission studies were carried out in degassed DMF at room temperature and 77 K. The complexes showed detectable phosphorescence only at 77 K, with room temperature emission quenched, possibly via a thermally-accessible 3 MC state. 18 The following analysis refers to the data collected at 77 K (Fig. 2, Table 1).…”