Photoinduced electron transfer reactions of 2,4,6-triphenylpyrylium: solvent effect and charge-shift type of systems

Jayanthi, S. S.; Ramamurthy, P.

doi:10.1039/a904727a

Cited by 19 publications

(25 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, literature reports have shown a lower φ CE in CH 2 Cl 2 compared to CH 3 CN or DMF for other photocatalysts. 44,63 There are three plausible, yet speculative, hypotheses for the large cage-escape yields observed with this iron photocatalyst. First, the 2 LMCT character of 1 + * leads to a mono-reduced complex with a reduced iron(II) metal center.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The fundamental factors that impact the measured cage-escape yields in this study are unknown. In fact, the factors that impact cage-escape yields are poorly understood in all of photochemistry, with electron spin being the only factor that has clearly been shown to have an impact. ,− Indeed, the high φ CE values in CH 2 Cl 2 with an iron photocatalyst is surprising and rare. Furthermore, literature reports have shown a lower φ CE in CH 2 Cl 2 compared to CH 3 CN or DMF for other photocatalysts. , …”

Section: Results and Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Accessing Photoredox Transformations with an Iron(III) Photosensitizer and Green Light

et al. 2021

View full text Add to dashboard Cite

Efficient excited-state electron transfer between an iron(III) photosensitizer and organic electron donors was realized with green light irradiation. This advance was enabled by the use of the previously reported iron photosensitizer, [Fe(phtmeimb)2]+ (phtmeimb = {phenyl[tris(3-methyl-imidazolin-2-ylidene)]borate}, that exhibited long-lived and luminescent ligand-to-metal charge-transfer (LMCT) excited states. A benchmark dehalogenation reaction was investigated with yields that exceed 90% and an enhanced stability relative to the prototypical photosensitizer [Ru(bpy)3]2+. The initial catalytic step is electron transfer from an amine to the photoexcited iron sensitizer, which is shown to occur with a large cage-escape yield. For LMCT excited states, this reductive electron transfer is vectorial and may be a general advantage of Fe(III) photosensitizers. In-depth time-resolved spectroscopic methods, including transient absorption characterization from the ultraviolet to the infrared regions, provided a quantitative description of the catalytic mechanism with associated rate constants and yields.

show abstract

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

Accessing Photoredox Transformations with an Iron(III) Photosensitizer and Green Light

et al. 2021

View full text Add to dashboard Cite

show abstract

“…Excited-state lifetimes of all rectangles in CH 2 Cl 2 and CH 3 CN were measured using a time correlated single photon counting (TCSPC) spectrometer (model 5000U, IBM, UK). 49 The second harmonic (375 nm) output from the Tsunami mode locked picosecond laser was used as the excitation source and a Hamamatsu photomultiplier tube (MCP-PMT R3890U) was used to detect the emission. An iterative fitting program provided by IBM was used to analyse the emission decay curves.…”

Section: Excited-state Lifetime Measurementsmentioning

confidence: 99%

Luminescence quenching of Re(i) molecular rectangles by quinones

et al. 2010

View full text Add to dashboard Cite

The rhenium-based rectangles [{Re(CO)(3)(mu-bpy)Br}{Re(CO)(3)(mu-L)Br}](2) (I, L = 4,4'-dipyridylacetylene (dpa); II, L = 4,4'-dipyridylbutadiyne (dpb); III, L = 1,4-bis(4'-pyridylethynyl)benzene (bpeb); bpy = 4,4'-bipyridine) are emissive in solution at room temperature. The presence of extended pi conjugation leads to an increase in electron delocalization, which, in turn, results in improved luminescence and lower nuclear reorganization energy. These rectangles, upon electronic excitation, undergo facile electron transfer (ET) reactions with quinones and both the dynamic and static quenching contribute to the reaction. Spectral and electrochemical measurements show that quinone 7,7,8,8-tetracyanoquinodimethane (TCNQ) binds strongly to rectangle I. The driving force dependence of k(et), deduced from the luminescence quenching of rectangles with quinones, can be well accounted for within the context of the Marcus theory of electron transfer.

show abstract

“…The initial screening revealed DDQ and 9-fluorenone as ineffective catalysts for this reaction giving a yield of 26% and 15%, respectively (Table 1, entries 1-2). Interestingly, the use of RFTA led to a moderate yield of 35% (Table 1, entry 3), while the more sensitive photocatalyst TPP (PC-4) (E1/2 = + 2.3 V), 21 yielded 76% of methyl 4-cyanobenzoate (Table 1, entry 4). Surprisingly, employing acridinium photocatalysts (E1/2 = + 2.28 V) 1u resulted in poor yields of 12% and 14%, respectively (Table 1, entries 5-6).…”

Section: Resultsmentioning

confidence: 99%

Visible-Light-Promoted Metal-Free Ammoxidation of C(sp3)-H bonds

Murugesan¹,

Donabauer²,

Koenig³

2020

Preprint

View full text Add to dashboard Cite

The metal-free activation of C(<i>sp</i><sup>3</sup>)-H bonds to value-added products is of paramount importance in organic synthesis. Herein, we report the use of the commercially available organic dye 2,4,6-triphenylpyrylium tetrafluoroborate (TPP) for the conversion of methylarenes to the corresponding aryl nitriles via a photo process. Applying this methodology, a variety of cyanobenzenes have been synthesized in good to excellent yield under metal- and cyanide-free conditions. We demonstrate the scope of the method with over 50 examples including late-stage functionalization of drug molecules (celecoxib) and complex structures such as L-menthol, amino acids and cholesterol derivatives. Further, the presented synthetic protocol is applicable for gram-scale reactions. In addition to methylarenes, selected examples for the cyanation of aldehydes, alcohols and oximes are demonstrated as well. Detailed mechanistic investigations have been carried out using time-resolved luminescence quenching studies, control experiments and NMR‑ spectroscopic as well as kinetic studies, all supporting the proposed catalytic cycle.

show abstract

Photoinduced electron transfer reactions of 2,4,6-triphenylpyrylium: solvent effect and charge-shift type of systems

Cited by 19 publications

References 48 publications

Accessing Photoredox Transformations with an Iron(III) Photosensitizer and Green Light

Accessing Photoredox Transformations with an Iron(III) Photosensitizer and Green Light

Luminescence quenching of Re(i) molecular rectangles by quinones

Visible-Light-Promoted Metal-Free Ammoxidation of C(sp3)-H bonds

Contact Info

Product

Resources

About