The intramolecular aryl embrace: from light emission to light absorption

Abstract

6-(1-Methylpyrrol-2-yl)-2,2'-bipyridine, 3, and 6-(selenophene-2-yl)-2,2'-bipyridine, 4, have been prepared and characterized in solution and by structural determinations. Copper(I) complexes [CuL(2)][PF(6)] in which L is 2,2'-bipyridine substituted in the 6-position by furyl, thienyl, N-methylpyrrolyl, selenopheneyl, methyl or phenyl, (L = 1-6) have been synthesized. The complexes have been characterized by electrospray mass spectrometry, and solution NMR and UV-VIS spectroscopies. The single crystal structures of [Cu(1)(2)][PF(6)], [Cu(2)(2)][PF(6)], [Cu(3)(2)][PF(6)], [Cu(5)(2)][PF(6)] and [Cu(6)(2)][PF(6)] have been determined. In those compounds containing an aromatic substituent attached to the bpy unit, the substituent is twisted with respect to the latter. In [Cu(3)(2)][PF(6)] and [Cu(5)(2)][PF(6)], this results in intra-cation π-stacking between ligands which is very efficient in [Cu(3)(2)](+) despite the steric requirements of the N-methyl substituents. Face-to-face stacking between the ligands in the [Cu(2)(2)](+) ion is achieved by complementary substituent twisting and elongation of one Cu-N bond, but there is no analogous intra-cation π-stacking in [Cu(1)(2)](+). Ligand exchange reactions between [CuL(2)][PF(6)] (L = 1-6) and TiO(2)-anchored ligands 7-10 (L' = 2,2'-bipyridine-based ligands with CO(2)H or PO(OH)(2) anchoring groups) have been applied to produce 24 surface-anchored heteroleptic copper(i) complexes, the formation of which has been evidenced by using MALDI-TOF mass spectrometry and thin layer solid state diffuse reflectance electronic absorption spectroscopy. The efficiencies of the complexes as dyes in DSCs have been measured, and the best efficiencies are observed for [CuLL'] with L' = 10 which contains phosphonate anchoring groups.

Light harvesting with Earth abundant d-block metals: Development of sensitizers in dye-sensitized solar cells (DSCs)

“…Some 6,6'-disubstituted-2,2'-bipyridines used in copper(I) sensitizers. were observed with anchoring ligand 43 which binds through phosphonate groups [96]. This is a recurring feature, pointing to phosphonate anchors being particularly advantageous.…”

‘Surfaces-as-ligands, surfaces-as-complexes’ strategies for copper(I) dye-sensitized solar cells

“…In order to optimize atom efficiency and to facilitate the screening of libraries of surface-bound dyes, we have developed methods of stepwise assembly of surface-bound bis(diimine) copper(I) dyes. In a further extention of the 'complexes-asligands' methodology introduced by the Bologna group for the systematic and regiospecific synthesis of homo-and heterometallic complexes [19,20], we have developed a powerful 'surfaces-as-ligands, surfaces-as-complexes' strategy for the preparation of DSSCs and other interfacial heterojunction devices [21,22,23,24,25,26,27,28]. In this approach, a nanoparticulate TiO 2 surface is treated with an anchoring ligand (L anchor ) which possesses two orthogonal functionalities: one is the anchoring group which interacts with the semiconductor (metal oxide in our case) surface and the other is one that can bind a metal centre.…”

To deprotect or not to deprotect: Phosphonate ester versus phosphonic acid anchor ligands in copper(I)-based dye-sensitized solar cells

“…The recognition of this lability allowed us to develop a method of assembling TiO 2 -bound heteroleptic [Cu(L anchor )(L ancillary )] + dyes directly on a surface [4]. The diimine ligand L anchor is typically functionalized with carboxylic or phosphonic acid groups, with the latter exhibiting enhanced binding and temporal performance over the former [13].…”