Difference between revisions of "Phosphorescence"

Latest revision as of 08:40, 22 May 2021

Angelo Albini[1]

Professor of Organic Chemistry at the University of Pavia, via Taramelli 12, 27100 Pavia, Italy.

Publication Date 19/10/2017 & 5/09/2019

Phosphorescence or afterglow. The name derives from phosphorous, on an irradiated sample from which a long-lived persistent after that irradiation was terminated, in contrast to fluorescence) emission was first observed, similarly to that obtained from white phosphorous [1, 2]. In that case and in many other ones it was later ascertained that it was a chemiluminescent reaction that was involved, as was the case for phosphor compounds [3], but also from several minerals, e.g. Vincenzo Casciarola, an Italian cobbler, described a long-lived emission from Bologna Stone, a form of barite, in 1603 [4], and luminescence from biologic samples had been known for centuries [5-8]). After the seminal work by GN Lewis [9, 10], the term phosphorescence is used only in a restricted sense to mean the vertical emission that occurs along with a change in multiplicity. In organic molecules, this is the forbidden emission from T[math]_{1}[/math] to S[math]_{0}[/math] that as such is slow ([math]\mu[/math]s to s and above) and is ill observed in the presence of oxygen. The triplet state acts as a metastable state, that is it doesn’t absorb light but is easily revealed by emission, provided that any interaction with a quencher is ineffective. In fact, although phosphorescence is revealed in a painfully purified solution or by having recourse of alternative methods of generation [10-12], it is usually registered in a glassy solvent in order to minimize bimolecular interaction and quenching. The slow phosphorescence emission is determined by the rigidity of the spin selection rule and is tempred in the presence of intramolecular and intermolecular heavy atoms.

References

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[3] Duewer W H, Setse D W, Infrared chemiluminescence and energy partitioning from reactions of fluorine atoms with hydrides of carbon, silicon, oxygen, sulfur, nitrogen, and phosphorus, The Journal of Chemical Physics , 1973, 58, 0.1063/1.1679506

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[8] G N Gilbert, Kasha M, Phosphorescence and the role of triplet state in the electronic excitation of complex molecules, Chem Rev, 1947, 41, 401-419.

[8] Lewis G N, Calvin M, Powe A M, Fletcher K A, St. Luce N N, Lowry, Sharon N, McCarroll M E, Philip B. Oldham P B, Linda B. McGown L B, Isiah M. Warner, I W, Molecular fluorescence, phosphorescence, and chemiluminescence spectrometry. Anal. Chem. 2004, 76, 4614-4634.

[9] Lewis GN, Calvin M, Kasha M, Photomagnetism. Determination of the paramagnetic susceptibility of a dye in its paramagnetic state, J Chem Phys, 1949, 17, 804-812

[9] Lewis G N, Calvin M, Paramagnetism on the phosphorescent state, J Am Chem Soc, 1945, 67, 1232-1233.

[10] Su MoonParkAllen J.Bard,Electrogenerated chemiluminescence. The production of benzophenone phosphorescence in fluid solution by radical ion reaction, Chem. Phys Let, 1976, 38, 257-262.

[11] J M Vanderkooi, G Maniara, T J Green, D F Wilson, An optical method for measurement of dioxygen concentration based upon quenching of phosphorescence, The Journal of Biological Chemistry 262, 5476-5482.

[12] A.Muñozde la Peña∗I.Durán-MerásF.SalinasI.M.WarnerT.T.Ndou, Cyclodextrin-induced fluid solution room-temperature phosphorescence from acenaphthene in the presence of 2-bromoethanol, Anal Chim Acta, 1991, 255, 351-357