Using TDDFT for Selective Tuning of 1st Row Transition Metal Complexes for Inner Sphere Photocatalysis

Research Seminar abstract

Transition metals make for ideal photocatalysts due to their absorption of visible light. Current research relies heavily on ruthenium and iridium based catalysts.1 Unfortunately, due to their rarity, these metals are not sustainable. Earth abundant 1st row transition metals provide an interesting alternative to rarer metals, but moving up the periodic table is not without its challenges. 1st row transition metals are more reactive, have lower redox barriers, are electron spin active, and have low-lying excited states.2 Some of these properties are thought to make an inner sphere mechanism possible by allowing the electron transfer to occur between complexes through a bridging ligand, in which no auxiliary agents are used. However, these properties also make 1st row transition metals difficult to characterize. Through the collaborate efforts spanning several labs, the combination of electronic structure theory with organic and inorganic synthesis and spectroscopy has yielded progress towards better photocatalytic complexes.

Density functional theory(DFT) is a natural choice for studying large transition metal complexes. APF-D functional is particularly useful in studying photocatalytic systems because of its accurate representation of the electron density and the inclusion of dispersion.3,4 Excited states of these complexes can be calculated using time dependent density functional theory (TDDFT). Theoretical absorption spectra can be generated from these excited state calculations, and natural transition orbitals (NTOs) can be used to classify types of electronic transitions.

A library of first row transition metals have been calculated, and ligands have been selectively tuned to promote high absorption in the visible region. Tripod and salen derivative type ligands have been studied extensively with early and late 1st row transition metals, laying the groundwork for substrate binding and enantioselective photocatalysis.

(1) Prier, C. K.; Rankic, D. A.; MacMillan, D. W. C. Chem. Rev. 2013, 113 (7), 5322–5363. (2)
Su, B.; Cao, Z.-C.; Shi, Z.-J. Acc. Chem. Res. 2015, 48 (3), 886–896.
(3) Austin, A.; Petersson, G. A.; Frisch, M. J.; Dobek, F. J.; Scalmani, G.; Throssell, K.
Journal of Chemical Theory
and Computation 2012, 8 (12), 4989–5007.
(4) Medvedev, M. G.; Bushmarinov, I. S.; Sun, J.; Perdew, J. P.; Lyssenko, K. A. Science 2017,
355 (6320), 49–52.

Division(s): Physical

Speaker: Collette Nite

Speaker Institution: Colorado State University

Event Date: 03-30-2017

Event Time: 4:00 PM

Event Location: Chemistry A101

Mixer Time: 3:45 PM

Mixer Location: Chemistry B101E

Host: C. Ackerson