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1. Cold Collisions of Ro-Vibrationally Excited D ₂ Molecules

   https://doi.org/10.1021/acs.jpca.2c08855  

   Croft, James F.; Jambrina, Pablo G.; Aoiz, F. Javier; Guo, Hua; Balakrishnan, N. (February 2023, The Journal of Physical Chemistry A)
2. Excited state dynamics of 2′-deoxyisoguanosine and isoguanosine in aqueous solution

   https://doi.org/10.1039/D1CP05795B  

   Caldero-Rodríguez, Naishka E.; Crespo-Hernández, Carlos E. (March 2022, Physical Chemistry Chemical Physics)

   Photostability is thought to be an inherent property of nucleobases required to survive the extreme ultraviolet radiation conditions of the prebiotic era. Previous studies have shown that absorption of ultraviolet radiation by the canonical nucleosides results in ultrafast internal conversion to the ground state, demonstrating that these nucleosides efficiently dissipate the excess electronic energy to the environment. In recent years, studies on the photophysical and photochemical properties of nucleobase derivatives have revealed that chemical substitution influences the electronic relaxation pathways of purine and pyrimidine nucleobases. It has been suggested that amino or carbonyl substitution at the C6 position could increase the photostability of the purine derivatives more than the substitution at the C2 position. This investigation aims to elucidate the excited state dynamics of 2′-deoxyisoguanosine (dIsoGuo) and isoguanosine (IsoGuo) in aqueous solution at pH 7.4 and 1.4, which contain an amino group at the C6 position and a carbonyl group at the C2 position of the purine chromophore. The study of these derivatives is performed using absorption and emission spectroscopies, broadband transient absorption spectroscopy, and density functional and time-dependent density functional levels of theory. It is shown that the primary relaxation mechanism of dIsoGuo and IsoGuo involves nonradiative decay pathways, where the population decays from the S 1 (ππ*) state through internal conversion to the ground state via two relaxation pathways with lifetimes of hundreds of femtoseconds and less than 2 ps, making these purine nucleosides photostable in aqueous solution. 

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3. Photochemical [2+4]‐Dimerization Reaction from the Excited State

   https://doi.org/10.1002/anie.202316662  

   Ahuja, Sapna; Baburaj, Sruthy; Valloli, Lakshmy_Kannadi; Rakhimov, Sarvar_Aminovich; Manal, Kavyasree; Kushwaha, Aakrati; Jockusch, Steffen; Forbes, Malcolm_D_E; Sivaguru, Jayaraman (December 2023, Angewandte Chemie International Edition)

   Abstract Aryl‐maleimides undergo a novel [2+4]‐photodimerization instead of the expected [2+2]‐photodimerization under both direct irradiation with visible light and under sensitized energy transfer conditions. This new excited state reactivity in aryl‐maleimides is deciphered through photochemical, photophysical, and spectroscopic studies. The stereochemistry of the photodimer depends on the type of non‐bonding interactions prevalent during photodimerization which is in turn dictated by the substituents on the maleimide ring. More importantly, the stereochemistry of the photodimer formed is complementary to the product observed under thermal conditions. 

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4. Electronically excited states of closed-shell azabenzene and purine anion structures: Is 2 D enough for dipole-bound excited states?

   https://doi.org/10.1063/5.0141385  

   Santaloci, Taylor J.; Fortenberry, Ryan C. (March 2023, The Journal of Chemical Physics)

   Deprotonated azabenzene anions require dipole moments in their corresponding neutral radicals of more than 3.5 D in order to exhibit dipole-bound excited states (DBXSs). This is notably larger than the typical 2.0–2.5 D associated with such behavior. Similar computational analysis on deprotonated purine derivatives also conducted herein only requires the more traditional 2.5 D dipole moment, implying that the single six-membered azabenzene rings have additional factors at play in binding diffuse electrons. The present study also shows that the use of coupled cluster singles and doubles with a double-zeta correlation consistent basis set and additional diffuse functions originating from the center-of-charge for all aspects of the computations decreases the error in predicting DBXSs to less than 0.006 eV at worst and likely less than 0.003 eV for most cases. These results can influence the modeling of molecular spectra beyond fundamental chemical curiosity with application to astrochemistry, solar energy harvesting, and combustion chemistry among others. 

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5. The ligand-to-metal charge transfer excited state of [Re(dmpe)3]2+

   https://doi.org/10.1007/s11120-021-00859-7  

   Rodriguez, Tayliz M.; Deegbey, Mawuli; Jakubikova, Elena; Dempsey, Jillian L. (July 2021, Photosynthesis Research)

   null (Ed.)

   The ligand-to-metal charge transfer (LMCT) transitions of [Re(dmpe)3]2+ (dmpe = bis-1,2-(dimethylphosphino)ethane) were interrogated using UV/Vis absorbance spectroscopy, photoluminescence spectroscopy, and time-dependent density functional theory. The solvent dependence of the lowest energy charge transfer transition was quantified; no solvatochromism was observed. TD-DFT calculations reveal the dominant LMCT transition is highly symmetric and delocalized involving all phopshine ligand donors in the charge transfer, providing an understanding for the absence of solvatochromism of [Re(dmpe)3]2+. 

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