Competing ultrafast photoinduced electron transfer and intersystem crossing of [Re(CO)$$_3$$(Dmp)(His124)(Trp122)]$$^+$$ in Pseudomonas aeruginosa azurin: a nonadiabatic dynamics study

Abstract

We present a computational study of sub-picosecond nonadiabatic dynamics in a rhenium complex coupled electronically to a tryptophan (Trp) side chain of Pseudomonas aeruginosa azurin, a prototypical protein used in the study of electron transfer in proteins. To gain a comprehensive understanding of the photoinduced processes in this system, we have carried out vertical excitation calculations at the TDDFT level of theory as well as nonadiabatic dynamics simulations using the surface hopping including arbitrary couplings (SHARC) method coupled to potential energy surfaces represented with a linear vibronic coupling model. The results show that the initial photoexcitation populates both singlet metal-to-ligand charge transfer (MLCT) and singlet charge-separated (CS) states, where in the latter an electron was transferred from the Trp amino acid to the complex. Subsequently, a complex mechanism of simultaneous intersystem crossing and electron transfer leads to the sub-picosecond population of triplet MLCT and triplet CS states. These results confirm the assignment of the sub-ps time constants of previous experimental studies and constitute the first computational evidence for the ultrafast formation of the charge-separated states in Re-sensitized azurin.

Intersystem Crossing and Triplet Dynamics in an Iron(II) N-Heterocyclic Carbene Photosensitizer

“…The recent implementation of a LVC model within SH 37 has made the dynamical simulations of molecules with hundreds of degrees of freedom much more computationally feasible. 38 , 39 …”

Surface Hopping Dynamics on Vibronic Coupling Models

“…The zeroth-order terms in eq 3 correspond to vertical excitation energies E n el and optional constant coupling terms η nm that are used to introduce weakly geometry-dependent couplings like spin−orbit couplings 25,28,29 or excitonic couplings. 18,19 The first-order terms in eq 4 define the widely used LVC model, 28,30−32 that mediate interactions between the diabatic states.…”

Ultrafast and long-time excited state kinetics of an NIR-emissive vanadium(iii) complex II. Elucidating triplet-to-singlet excited-state dynamics

“…In order to overcome these challenges, we recently combined the nonadiabatic trajectory surface hopping method SHARC 24,25 with a linear vibronic coupling (LVC) approach 26 to compute the electronic potentials. 27 In this way, the photodynamics of a number of transition metal complexes have been investigated, 16,[28][29][30] where time-dependent density functional theory (TDDFT) was used to parametrize the LVC potentials. Given its positive tradeoff between accuracy and computational cost, TDDFT is likely the most popular method to study transition metal complexes 31,32 , and it has also been applied in on-the-fly surface hopping studies of other transition-metal complexes.…”