Department of Chemistry

Current Group Research



Ultrafast Intersystem Crossing Dynamics

Our research group investigate molecules that challenge conventional paradigms in photochemistry. One of such traditional views is that the rate of internal conversion (IC) is always larger than that of intersystem crossing (ISC). However, molecules can exhibit excited-state non-equilibrium dynamics when their singlet and triplet states are strongly coupled by spin-orbit interactions; the so-called strongly non-adiabatic regime. In these molecules, the distinction between singlet and triplet states is no longer well-defined and understanding their excited-state dynamics requires the use of ultrafast time-resolved techniques, high-level ab initio calculations, and mixed quantum-classical dynamics methods that model non-adiabatic and spin-orbit couplings on equal footing. Developing and refining a quantitative understanding of the excited-state dynamics in these molecules, has the potential to change comtemporary views on how we think about the photochemistry and excited-state dynamics in these molecules.



Non-Equilibrium Dynamics



Organometalics

Recent Publications

  • Ashwood, B.; Ortiz-Rodríguez, L. A.; Crespo-Hernández, C. E., "Photochemical Relaxation Pathways of S6-Methylthioinosine and O6-Methylguanosine in Solution", Faraday Discuss. 2018, DOI: 10.1039/C7FD00193B. Invited Manuscript; submitted as part of the themed collection: "Photoinduced Processes in Nucleic Acids and Proteins". Access article
  • Yang, W.; Ashwood, B.; Zhao, J.; Ji, W.; Escudero, D.; Jacquemin, D.; Crespo-Hernández, C. E., "Ultrafast Excited-State Dynamics in Cyclometalated Ir(III) Complexes Coordinated with Perylenebisimide and Its π-Radical Anion Ligands", J. Phys. Chem. C 2017, 121, 21184-21198. Access article
  • Ashwood, B.; Ortiz-Rodríguez, L. A.; Crespo-Hernández, C. E., "Excited-State Dynamics of O6-Methylguanosine: Impact of O6-Methylation on the Photophysics of Guanine Monomers", J. Phys. Chem. Lett. 2017, 8, 4380–4385. Access article
  • Sánchez-Rodríguez, J. A.; Mohamadzade, A.; Mai. S.; Ashwood, B.; Pollum, M.; Marquetand, P.; González, L.; Crespo-Hernández, C. E.; Ullrich, S., "2-Thiouracil Intersystem Crossing Photodynamics Studied by Wavelength-Dependent Photoelectron and Transient Absorption Spectroscopies", Phys. Chem. Chem. Phys. 2017, 19, 19756-19766. Invited Manuscript; submitted as part of the themed issue on the "XUV/XRay Light and Fast Ions for Ultrafast Chemistry".Access article
  • 69. DiScipio, R.; Santiago, R. Y.; Taylor, D.; Crespo-Hernández, C. E., "Electronic Relaxation Pathways of the Biologically Relevant Pterin Chromophore", Phys. Chem. Chem. Phys. 2017, 19, 12720-12729. Access article
  • Ashwood, B.; Jockusch, S.; Crespo-Hernández, C. E., "Photochemical Reactivity of dTPT3: A Crucial Nucleobase Derivative in the Development of Semi-Synthetic Organisms", J. Phys. Chem. Lett. 2017, 8, 2387−2392. Access article
  • Ashwood, B.; Jockusch, S.; Crespo-Hernández, C. E., "Excited-State Dynamics of the Thiopurine Prodrug 6-Thioguanine: Can N9-Glycosylation Affects Its Phototoxic Activity?", Molecules 2017, 22, 379 (15 pages). Access article
  • Martínez-Fernández, L.; Granucci, G.; Pollum, M.; Crespo-Hernández, C. E.; Persico, M.; Corral, I., "Decoding the Molecular Basis for the Population Mechanism of the Triplet Phototoxic Precursors in UVA Light-Activated Pyrimidine Anticancer Drugs", Chem. Eur. J. 2017, 23, 2619-2627. Access article
  • Mai, S.; Pollum, M.; Martínez-Fernández, L.; Dunn, N.; Marquetand, P.; Corral, I.; Crespo-Hernández, C. E.; González, L., "The Origin of Efficient Triplet State Population in Sulfur-Substituted Nucleobases", Nature Commun. 2016, 7, 13077 (DOI: 10.1038/ncomms13077). Access article
  • Ashwood, B.; Pollum, M.; Crespo-Hernández, C. E., "Can a Six-Letter Alphabet Increase the Likelihood of Photochemical Assault to the Genetic Code?", Chem. Eur. J. 2016, 22, 16648-16656. Access article
  • Yu, H. Sanchez-Rodriguez, J. A.; Ullrich, S.; Pollum, M.; Crespo-Hernández, C. E.; Mai. S.; Marquetand, P.; González, L., "Internal Conversion and Intersystem Crossing Pathways in UV Excited, Isolated Uracils and Their Implications in Prebiotic Chemistry", Phys. Chem. Chem. Phys. 2016, 18, 20168-20176. Invited Manuscript; submitted as part of the themed issue on the "Prebiotic Chemistry and the Molecular Origins of Life".Access article
  • Pollum, M.; Ortiz-Rodríguez, L. A.; Jockusch, S.; Crespo-Hernández, C. E., "The Triplet State of 6-Thio-2’-deoxyguanosine: Intrinsic Properties and Reactivity toward Molecular Oxygen", Photochem. Photobiol. 2016, 92, 286-292. Access article
  • Selected as one of the top papers published in the journal Photochemistry & Photobiology, as part of a virtual issue cellebrating its 55th anniversary.
    Access and read the complete virtual issue here.

  • Brister, M.; Crespo-Hernández, C. E. "Direct Observation of Triplet-State Population Dynamics in the RNA Uracil Derivative 1-Cyclohexyluracil", J. Phys. Chem. Lett. 2015, 6, 4404-4409. Access article
  • Pollum, M.; Martínez-Fernández, L.; Crespo-Hernández, C. E.; "Photochemistry of Nucleic Acid Bases and their Thio- and Aza-Analogues in Solution", Top. Curr. Chem. 2015, 355, 245-327. Invited Review Chapter. Access article
  • Pollum, M.; Jockusch, S.; Crespo-Hernández, C. E. "Increase in the Phooreactivity of Uracil Derivatives by Doubling Thionation", Phys. Chem. Chem. Phys. 2015, 17, 27851-27861. Access article
  • Pollum, M.; Jockusch, S.; Crespo-Hernández, C. E.; "2,4-Dithiothymine as a Potent UVA Chemotherapeutic Agent", J. Am. Chem. Soc. 2014, 136, 17930-17933. Access article
  • Pollum, M.; Crespo-Hernández, C. E.; "Communication: The dark singlet state as a doorway state in the ultrafast and efficient intersystem crossing dynamics in 2-thiothymine and 2-thiouracil", J. Chem. Phys. 2014, 140, 071101. Access article
  • Vogt, R. A.; Reichardt, C.; Crespo-Hernández, C. E.; "Excited-State Dynamics in Nitro-Naphthalene Derivatives: Intersystem Crossing to the Triplet Manifold in Hundreds of Femtoseconds", J. Phys. Chem. A 2013, 117, 6580-6588. Access article
  • Vogt, R. A.; Gray, T. G.; Crespo-Hernández, C. E.;"Subpicosecond Intersystem Crossing in Mono- and Di-(Organophosphine)gold(I) Naphthalene Derivatives in Solution", J. Am. Chem. Soc. 2012, 134, 14808–14817.Access article
  • Reichardt, C.; Guo, C.; Crespo-Hernández, C. E.;"Excited-State Dynamics in 6-Thioguanosine from the Femtosecond to Microsecond Time Scale", J. Phys. Chem. B 2011, 115, 3263-3270.Access article
  • Reichardt, C.; Crespo-Hernández, C. E.; "Room-Temperature Phosphorescence of the DNA Monomer Analogue 4-Thiothymidine in Aqueous Solutions after UVA Excitation", J. Phys. Chem. Lett. 2010, 1, 2239-2243.Access article
  • Reichardt, C.; Crespo-Hernández, C. E.; "Ultrafast Spin Crossover in 4-Thiothymidine in an Ionic Liquid", Chem. Comm. 2010, 46, 5963-5965.Access article
  • Reichardt, C.; Vogt, R. A.; Crespo-Hernández, C. E.; "On the Origin of Ultrafast Nonradiative Transitions in Nitro-PAHs: Excited-State Dynamics in 1-Nitronaphthalene", J. Chem. Phys. 2009, 131, 224518.Access article