Photostable Polynuclear Ruthenium(II) Photosensitizers Competent for Dehalogenation Photoredox Catalysis at 590 nm

Abstract

Higher nuclearity photosensitizers produced dehalogenation yields greater than 90% in the reported [Ru(bpy) 3 ] 2+mediated dehalogenation of 4-bromobenzyl-2-chloro-2-phenylacetate to 4-bromobenzyl-2-phenylacetate with orange light in 7 h, whereas after 72 h yields of 49% were obtained with [Ru(bpy) 3 ] 2+ . Dinuclear (D1), trinuclear (T1), and quadrinuclear (Q1) ruthenium(II) 2,2′-bipyridine based photosensitizers were synthesized, characterized, and investigated for their photoreactivity. Three main factors were shown to lead to increased yields (i) the red-shifted absorbance of polynuclear photosensitizers, (ii) the more favorable driving force for electron transfer, characterized by more positive E 1/2 (Ru 2+ * /+ ), and (iii) the smaller population of the 3 MC state (<0.5% for D1, T1 and Q1 vs 48% for [Ru(bpy) 3 ] 2+ at room temperature). Collectively, these results highlight the potential advantages of using polynuclear photosensitizers in phototriggered redox catalysis reactions.

Tuning the excited-state deactivation pathways of dinuclear ruthenium(ii) 2,2′-bipyridine complexes through bridging ligand design

“…This bears immediate consequence for research in bio-imaging 32,33 , photobiology 34 , photo-conversion 35,36 , as well as photoredox catalysis. 37 A drastic influence of the geometry of the connection between the two bipyridine parts of the bridging ligand was shown. Connection through the para position of the 2,2'-bipyridine, as in complex DP, increased the portion of absorbed visible light, as well as the molar absorption coefficient, and decreased the rate constants of direct (kdr + kdnr) and activated deactivation pathways (k3MC + k3MLCT).…”

“…[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] These dinuclear ruthenium(II) complexes 31 have found applications in the field of bio-imaging 32,33 , photobiology 34 , photo-conversion 35,36 and more recently in the field of photoredox catalysis. 37 Significantly, the nature of the bridging ligand is of paramount importance, as this influences the electronic communication between the metal centers, as well as the excited-state properties. 38 In this study, the photophysical and photochemical properties of two dinuclear Ru(II) complexes (Dp and Dm) were correlated to the geometric arrangement of chelating sites of the bridging ligand, i.e.…”

A biohybrid strategy for enabling photoredox catalysis with low-energy light

“…[44][45][46][47] Energy transfer, which occurs over longer distances, was introduced by conjugating together transition-metal photocatalysts with different excitation energies, which expanded their absorption window. [48][49][50][51][52][53][54][55] Despite the expanded absorption, the low extinction coefficients of the photocatalysts lead to light-limited activity under many conditions. The absorption range was also expanded into the low-energy (near-infrared) region by direct excitation of the 3 MLCT state, and the utility of this scheme was demonstrated on a range of photoredox reactions.…”

Silicon-Silver Dendritic Nanostructures Enabled Photoelectrochemical Solar Water Splitting for Energy Applications

“…Semiconductor nanostructures have been studied from the photoelectrochemical-induced solar water splitting. Other materials such as ruthenium polypyridyl complexes have been investigated as visible light-induced photo-sensitizers for water splitting applications [22]. Synthesis of carbon nanotube anode and tin oxide nanoribbons has been carried out for various applications [23].…”