Copper(i) complexes of 6,6′-disubstituted 2,2′-bipyridine dicarboxylic acids: new complexes for incorporation into copper-based dye sensitized solar cells (DSCs)

Abstract

Synthetic approaches to 6,6'-disubstituted-2,2'-bipyridine ligands bearing carboxylic acid substituents at the 4,4' or 5,5'-positions are described. Copper(I) complexes with these ligands have been prepared for use in copper-based dye-sensitized solar cells. The single-crystal structures of 6,6'-dimethyl-2,2'-bipyridine-4,4'-dicarboxylic acid (H(2)4), [H(3)6][CF3CO2].2CF3CO2H (H(2)6 = 6,6'-diphenyl-2,2'-bipyridine-4,4'-dicarboxylic acid) and 4[Cu(H(2)2)(H2)].3H2O (H(2)2 = 6,6'-dimethyl-2,2'-bipyridine-5,5'-dicarboxylic acid) are described, as well as those of the intermediates (1E,5E)-1,6-di(2-furyl)hexa-1,5-diene-3,4-dione and 4,4'-di(2-furyl)-6,6'-dimethyl-2,2'-bipyridine (3), and the copper(I) complex [Cu(3)(2)][PF6]. The roles that classical and non-classical hydrogen bonding and pi-stacking interactions play in determining the solid-state packing in these structures are discussed. Preliminary studies of DSCs with these complexes are reported.

The beneficial effects of trifluoromethyl-substituents on the photoconversion efficiency of copper(i) dyes in dye-sensitized solar cells

“…Most attention has focused on the development of [Cu(NN) 2 ] + complexes in whichNN is a 2,2 0 -bipyridine (bpy) or 1,10-phenanthroline (phen) domain. Early copper(I) dyes were homoleptic complexes bearing anchoring groups, [8][9][10][11] and such compounds continue to be used.…”

Copper Bipyridyl Redox Mediators for Dye-Sensitized Solar Cells with High Photovoltage

“…13−15 Stability issues and toxicity concerns regarding cobalt complexes limit their potential for industrialization and mass production. 16,17 As alternative redox mediators, copper complexes (Cu(I)/ Cu(II)) have been studied both as redox mediators 18−21 and hole-transport materials (HTMs) 22 in DSCs. First, Hattori et al obtained a maximum photon to current efficiency (PCE) of 1.4% with bis(2,9-dimethyl-1,10-phenantroline)copper(I)/(II) [Cu(dmp) 2 ] 2+/+1 , which has a distorted tetragonal shape providing a relatively low reorganization energy.…”

A strategy for controlling charge and conformation in 2,2′-bipyridine complexes for use in photonic applications

“…The conventional approach to anionic ''bpy-like" ligands (bpy = 2,2 0 -bipyridine) involves cyclometallation of ligands such as 2-phenylpyridine to give negatively-charged CN-donors although this can have unwanted stereogenic and reactivity consequences. We [7,11] and others [12] have investigated carboxylic acid functionalised ligands which may be deprotonated at the periphery and, although readily available, they prove to exhibit unpredictable lattice hydrogen-bonding interactions. In this paper, we describe the use of 3,3 0 -dihydroxy-2,2 0 -bipyridine ligands which after monodeprotonation give anionic species which are conformationally locked through intramolecular hydrogen bonding, converting a ''bpy-like" to a ''phen-like" metal-binding domain (see Scheme 1).…”

“…We have recently utilised such ligands in copper-based photovoltaic cells [5][6][7] and in the course of this work identified a need for new ligands which control the conformation and charge of these metal-binding domains. The photophysical properties of [CuL 2 ] + complexes depend critically on the degree of distortion from the ideal D 2d symmetry [8][9][10].…”