Investigating the influence of relativistic effects on absorption spectra for platinum complexes with light-activated activity against cancer cells

Abstract

We report the first systematic investigation of relativistic effects on the UV-vis spectra of two prototype complexes for so-called photo-activated chemotherapy (PACT), trans–trans–trans-[Pt(N3)2(OH)2(NH3)2] and cis–trans–cis-[Pt(N3)2(OH)2(NH3)2].

Polarizable embedding complex polarization propagator in four- and two-component frameworks

“…In the previous section, we saw that PE-X2C-CPP worked excellently to describe and we now move to a more challenging system: we have previously investigated trans-trans-trans-[Pt(N 3 ) 2 (OH) 2 (NH 3 ) 2 ] with conventional response theory. 24 We found that around 80 roots in the response equations were necessary to cover the UV-vis region; while this is possible for present days response solvers, it is certainly to the high site. The CPP model has a large advantage and we show the UV-vis spectra for trans-trans-trans-[Pt(N 3 ) 2 (OH) 2 (NH 3 ) 2 ] in vacuum and water in Figure 7.…”

“…We have previously investigated the platinum complex in the same manner and came to the same conclusion. 24 We will in the subsections therefore not discuss non-relativistic results, but focus on quantifying the effect of either solvation or the effect of switching from 4c to X2C Hamiltonian.…”

“…Particular for the L-edge involving the 2p-orbitals, a relativistic description is pertinent since spin-orbit coupling splits the 2p-orbitals into p 1 2 and p3 2 , giving rise to L II and L III edges. Generally, the inclusion of spin-orbit coupling will also entail the inclusion of a (non-degenerate) triplet manifold, resulting in a high density of states, 21,24 giving the CPP model another advantage in relativistic TD-DFT calculations.…”

“…Finally, we also apply our newly developed method on the platinum complex trans-trans-trans-[Pt(N 3 ) 2 (OH) 2 (NH 3 ) 2 ], which is a prototype complex for photo-activated cancer therapy. 57,58 Therefore, its' UV-vis spectrum has been studied extensively, although only recently by relativistic methods 24,59 and without solvent effects.…”

General Design Rules for Bimetallic Platinum(II) Complexes

“…Though the density of states will increase, given additional transitions would become allowed under the relativistic regime, explicit inclusion of relativistic effects is not expected to substantially improve the intense spectral signals. 46 Additionally, since exchange-correlation kernels are fundamentally frequency independent, the calculations presented in this study are confined to the adiabatic approximation. Finally, although some evidence of double excitations, in the form of satellite peaks, can be seen in the experimental spectra, the agreement between the observed and simulated spectra suggests single excitations are dominant in these systems.…”