#chemistry #photochemistry #molecular #education #oxygen #anticancer #quantumphysics #quantumtheory #molecularorbitaltheory

This is an edited videolecture for chemists that are interested in molecular oxygen, photochemistry and singlet oxygen.
The triplet ground state of molecular oxygen and the excited state, singlet oxygen, are discussed.
(A similar lecture has been presented for BSc students, for MSc students, for PhD students as well as for Professors at an institutional talk).

For more information on PDT and singlet oxygen, see also
   • The Photochemistry of Photodynamic (a...  
(and text below video, for references)

Learning objectives:
1
Molecular oxygen has a triplet ground state, responsible for many of its special properties.
It has "biradial character". We need the Lewis structure with the double bond as well as the Lewis structure with the two unpaired electrons (with the same spin) to describe it, in a simple way.

2
Singlet oxygen, the delta form, can react similar to ozone, it can result in similar reaction products. We can use the zwitterionic resonance form of singlet oxygen to describe some of its reactivity.

3
Lewis structures of excited states can be very useful, and give insight, in a different way. We have to use quantum mechanics to describe the system fully, and as good as we can. It can help to than translate the full quantum chemical results into "simplified Lewis structure of excited states".
We do that on a regular basis for charge transfer states as well as for pushpull chromophores.
https://doi.org/10.3906/kim081133
(Figure 4)
https://doi.org/10.1039/B818371F
(Figure 10)
https://doi.org/10.1002/cphc.200500127
(computations)
https://doi.org/10.1142/9789814327824...
(Figure 7)
https://doi.org/10.1039/c2pp05378k
(Figure 6)
https://doi.org/10.1039/c9pp00399a
(Figure 13, 14, 15, in an abstract way)
https://doi.org/10.1002/chem.202001494
(scheme 1)
https://www.researchgate.net/profile/...


Some related work on molecular oxygen:

The most important information presented in this video can be found on pages 583586 of
Modern Molecular Photochemisry, by Nicolas J. Turro, 1991.

Hoffman
https://doi.org/10.1021/jacs.7b04232

Greer (Ene reaction)
https://doi.org/10.1021/ja027225p

Turro & Murthy 1976:
https://doi.org/10.1021/ja00437a088
(picture with zwitterionic form!!)
"Thus, the reaction of 1 and singlet oxygen produces an intermediate whose decomposition results in formation of excited states of 2. This intermediate is stable for days at —90 °C. Reaction of
1 with the phosphorus ozonides 39a and 49b also results in chemiluminescence at temperatures below 0 °C."


DFT
https://doi.org/10.1063/1.2217733

Ogilby papers:
https://doi.org/10.1039/B926014P

Wilkinson papers
https://doi.org/10.1063/1.555965
https://doi.org/10.1063/1.555934

YouTube lectures on singlet oxygen reactivity:
   • Photoreduction and singlet oxygen pho...  
(note mistake in MO scheme of oxygen!!).

   • Mod01 Lec20 Singlet Oxygen Chemistry  
(at ~9:10 zwitterionic form of singlet oxygen is used!!)


ADDITION:
20042023
see also Figure 3 in:
Journal of Porphyrins and Phthalocyanines J. Porphyrins Phthalocyanines 2001; 5: 105–129
REVIEW
Basic principles of photodynamic therapy
IAN J. MACDONALD* and THOMAS J. DOUGHERTY

https://doi.org/10.1002/jpp.328


oxygen v2 28 01 2023