The Role of Triplet States in the Photodissociation of a Platinum Azide Complex by a Density Matrix Renormalization Group Method

Abstract

Platinum azide complexes are appealing anticancer photochemotherapy drug candidates because they release cytotoxic azide radicals upon light irradiation. Here we present a density matrix renormalization group self-consistent field (DMRG-SCF) study of the azide photodissociation mechanism of trans,trans,trans -[Pt(N 3 ) 2 (OH) 2 (NH 3 ) 2 ], including spin–orbit coupling. We find a complex interplay of singlet and triplet electronic excited states that falls into three different dissociation channels at well-separated energies. These channels can be accessed either via direct excitation into barrierless dissociative states or via intermediate doorway states from which the system undergoes non-radiative internal conversion and intersystem crossing. The high density of states, particularly of spin-mixed states, is key to aid non-radiative population transfer and enhance photodissociation along the lowest electronic excited states.

Simplified State Interaction for Matrix Product State Wave Functions

“…This insufficiency can be remedied by a DMRG-SCF calculation with 26 electrons in 19 orbitals, as employed in ref ( 45 ). As this active space is computationally too expensive for a CASSCF calculation, only DMRG-SCF calculations with subsequent approximate and full MPSSI calculations are performed.…”

“…As a testbed we employ trans, trans, trans-[Pt­(N 3 ) 2 (OH) 2 (NH 3 ) 2 ] (in the following referred to as 1 ), which is a flagship Pt­(IV) azide complex, relevant in photoactivated cancer chemotherapy. − As the majority of 5d metal compounds, 1 shows strong spin–orbit couplings and since its photoactivation mechanism involves azide dissociation, such a process is best described by multiconfigurational methods …”

“…42−44 As the majority of 5d metal compounds, 1 shows strong spin−orbit couplings and since its photoactivation mechanism involves azide dissociation, such a process is best described by multiconfigurational methods. 45 3.1. Performance of MPSSI Approximation on Wave Function Overlaps.…”

“…h i b i t e d .ref45. As this active space is computationally too expensive for a CASSCF calculation, only DMRG-SCF calculations with subsequent approximate and full MPSSI calculations are performed.…”

Enhanced Electron Transfer and Spin Flip through Spin–Orbital Couplings in Organic/Inorganic Heterojunctions: A Nonadiabatic Surface Hopping Simulation

“…NA-MD methods implementing the surface hopping (SH) scheme in the framework of time-dependent Kohn–Sham (TDKS) equation (in brief, TDKS-based NA-MD) − provide a detailed description of spin-free electronic state transitions resulting from electron–phonon couplings (EPCs), such as the charge transfer, hot carriers relaxation, and nonradiative recombination in condensed matter systems. ,,,− More recently, NA-MD has started to report SOC effects on these nonadiabatic processes, ,− yet SOC-induced spin dynamics is unreported to the best of our knowledge. Consequently, the fundamental knowledge of the fate of electron spin during the interlayer charge transfer and relaxation in solids, which is important for light harvesting, efficiency promotion of organic solar cells, and applicable high-IQE luminescent devices, , continues to be a missing piece of information because of the absence of suitable theoretical tools. ,, Therefore, there is an urgent need to investigate SOC-induced spin-related electron dynamics at organic/inorganic interfaces. Recently, Zheng et al .…”