Rich or poor: the impact of electron donation and withdrawal on the photophysical and photocatalytic properties of copper(i) complexes

Abstract

Motivated by the need to design efficent photocatatalysts based on eart-abundant metals and to elucidate essential structure-property relationships this study deals with heteroleptic copper(I) complexes. A systematic series of four...

Bright or Dark: Unexpected Photocatalytic Behavior of Closely Related Phenanthroline‐based Copper(I) Photosensitizers

“…The complexes [Cu(5,6-bis(4-methoxyphenyl)-2,9-dimethyl-1,10phenanthroline)(xant)]PF 6 Cu1, [48] [Cu(4,7-bis(4-methoxyphenyl)-2,9-dimethyl-1,10-phenanthroline)(xant)]PF 6 Cu2 [49] and the reference complex [Cu(bcp)(xant)]PF 6 CuRef [48] (Figure 1) were synthesized for previous studies and used here for further investigations.…”

“…Both complexes exhibit the typical structural features common to this class of compounds: i) a distorted tetrahedral geometry around the copper center, ii) the tendency that the CuÀ N bonds are shorter than the CuÀ P bonds and iii) a significant π-π stacking interaction between one phenyl ring and the phenanthroline core. [10,23,[48][49][50][51] Despite Figure 1. Various phenyl-based substituents were introduced to the 2,9dimethyl-1,10-phenanthroline moiety in 5,6-position (cf.…”

“…[48] The same functional groups in 4,7-position (red, top right) have a significantly different impact on the photophysical properties of the resulting Cu I PS. [49] Therefore, the two most different derivatives Cu1 and Cu2, both bearing 4methoxyphenyl substituents (blue and red, bottom), are investigated in this study.…”

“…[48] Within the investigated series, it was found that the most electron donating derivative, bearing 4-methoxyphenyl substituents in 5,6-position, has the least beneficial photophysical properties, i. e. shortest emission lifetime and lowest quantum yield (τ em = 11 ns and Φ em = 0.16 %). [48] As electron donating groups have been reported to rather improve these parameters, [8,50] our recent work [49] explored the same functional groups, but in the 4,7-position (Figure 1, top right). In this case, the functionalization caused changes in the photophysical properties, which were in accordance with the literature: [8,50] absorptivity, emission lifetime and emission quantum yield were increased by the electron rich 4-methoxyphenyl substituents (e. g. τ em = 628 ns and Φ em = 2.1 %).…”

“…In this case, the functionalization caused changes in the photophysical properties, which were in accordance with the literature: [8,50] absorptivity, emission lifetime and emission quantum yield were increased by the electron rich 4-methoxyphenyl substituents (e. g. τ em = 628 ns and Φ em = 2.1 %). [49] To understand why the 4-methoxyphenyl substitution in 5,6-position leads to short-lived emissive states with low emission intensity, while the same substituents in 4,7-position yields highly emissive and long-lived states, we have now conducted a comprehensive study comparing both Cu I PSs. This study aims to directly contrast some of their known properties and, in addition, to extend the investigation by detailed spectroscopic and computational techniques.…”