Theoretical study of spin-orbit coupling on spectra and photophysics of rhenium complexes

Title: Theoretical study of spin-orbit coupling on spectra and photophysics of rhenium complexes Author: RNDr. Radka Heydová Department: Physical and Macromolecular Chemistry Supervisor: Ing. Stanislav Záliš, CSc., JHI AS CR, v.v.i. Supervisor's e-mail address: [email protected] Abstract: Relativistic effects, especially spin-orbit coupling (SOC), play an essential role in transition metal chemistry and SOC treatment is indispensable for a correct theoretical description. To demonstrate the importance of SOC, the energies and oscillator strengths of vertical transitions for a series of [ReX(CO)3(2,2'-bipyridine)] (X = Cl, Br, I) and [Re(imidazole)(CO)3(1,10-phenanthroline)]+ complexes were calculated in the spin-free (SF) and spin-orbit (SO) conceptual frameworks. Two different computational approaches were adopted: SO-MS-CASPT2 where SOC was added a posteriori using a configuration interaction model (SO-RASSI), and the approximate perturbative SO-TD-DFT method. Relativistic effects were included via the two-component Douglas-Kroll-Hess transformation and the zeroth-order regular approximation in the former and the latter technique, respectively. The SF (i.e. accounting only for the scalar relativistic effects) and SO results from both methods were compared with each other and to available..

Teoretická studie vlivu spin-orbitální interakce na spektra a fotofyziku rheniových komplexů

Název práce: Teoretická studie vlivu spin-orbitální interakce na spektra a fotofyziku rheniových komplexů Autor: RNDr. Radka Heydová Katedra: Fyzikální a makromolekulární chemie Školitel: Ing. Stanislav Záliš, CSc., ÚFCH JH AV ČR, v.v.i. E-mail školitele: [email protected] Abstrakt: Předkládaná práce poukazuje na důležitost relativistických efektů, obzvláště spin- orbitální interakce (SOI), jež hrají zásadní roli v chemii komplexů přechodných kovů. Zahrnutí SOI je tak nezbytné pro jejich správný teoretický popis. Za účelem prokázání významu SOI byly pro komplexy [ReX(CO)3(2,2'-bipyridin)] (X = Cl, Br, I) a [Re(imidazol)(CO)3(1,10-fenantrolin)]+ napočítány energie a oscilátorové síly vertikálních přechodů v bez-spinovém (spin-free, SF) a spin-orbitálním (SO) konceptuálním rámci. Byly použity dva různé výpočetní přístupy: SO-MS-CASPT2, kde byla SOI přidána a posteriori pomocí konfiguračního stavového modelu (SO-RASSI), a přibližná poruchová metoda SO- TD-DFT. Relativistické efekty byly zohledněny prostřednictvím dvoukomponentní Douglas- Kroll-Hessovy transformace a regulární aproximace nultého řádu (ZORA) v prvním, resp. druhém případě. SF (tj. obsahující pouze skalární relativistické efekty) a SO výsledky z obou metod byly porovnány navzájem a s dostupnými experimenty. Charakter přenosových...Title: Theoretical study of spin-orbit coupling on spectra and photophysics of rhenium complexes Author: RNDr. Radka Heydová Department: Physical and Macromolecular Chemistry Supervisor: Ing. Stanislav Záliš, CSc., JHI AS CR, v.v.i. Supervisor's e-mail address: [email protected] Abstract: Relativistic effects, especially spin-orbit coupling (SOC), play an essential role in transition metal chemistry and SOC treatment is indispensable for a correct theoretical description. To demonstrate the importance of SOC, the energies and oscillator strengths of vertical transitions for a series of [ReX(CO)3(2,2'-bipyridine)] (X = Cl, Br, I) and [Re(imidazole)(CO)3(1,10-phenanthroline)]+ complexes were calculated in the spin-free (SF) and spin-orbit (SO) conceptual frameworks. Two different computational approaches were adopted: SO-MS-CASPT2 where SOC was added a posteriori using a configuration interaction model (SO-RASSI), and the approximate perturbative SO-TD-DFT method. Relativistic effects were included via the two-component Douglas-Kroll-Hess transformation and the zeroth-order regular approximation in the former and the latter technique, respectively. The SF (i.e. accounting only for the scalar relativistic effects) and SO results from both methods were compared with each other and to available...Katedra fyzikální a makromol. chemieDepartment of Physical and Macromolecular ChemistryPřírodovědecká fakultaFaculty of Scienc

Spin-Orbit TDDFT Electronic Structure of Diplatinum(II,II) Complexes

[Pt_2(μ-P_2O_5H_2)_4]^(4–) (Pt(pop)) and its perfluoroborated derivative [Pt_2(μ-P_2O_5(BF_2)_2)_4]^(4–) (Pt(pop-BF_2)) are d^8–d^8 complexes whose electronic excited states can drive reductions and oxidations of relatively inert substrates. We performed spin–orbit (SO) TDDFT calculations on these complexes that account for their absorption spectra across the entire UV–vis spectral region. The complexes exhibit both fluorescence and phosphorescence attributable, respectively, to singlet and triplet excited states of dσ*pσ origin. These features are energetically isolated from each other (∼7000 cm^(–1) for (Pt(pop-BF_2)) as well as from higher-lying states (5800 cm^(–1)). The lowest ^3dσ*pσ state is split into three SO states by interactions with higher-lying singlet states with dπpσ and, to a lesser extent, pπpσ contributions. The spectroscopically allowed dσ*pσ SO state has ∼96% singlet character with small admixtures of higher triplets of partial dπpσ and pπpσ characters that also mix with 3dσ*pσ, resulting in a second-order ^1dσ*pσ–^3dσ*pσ SO interaction that facilitates intersystem crossing (ISC). All SO interactions involving the dσ*pσ states are weak because of large energy gaps to higher interacting states. The spectroscopically allowed dσ*pσ SO state is followed by a dense manifold of ligand-to-metal–metal charge transfer states, some with pπpσ (at lower energies) or dπpσ contributions (at higher energies). Spectroscopically active higher states are strongly spin-mixed. The electronic structure, state ordering, and relative energies are minimally perturbed when the calculation is performed at the optimized geometries of the ^1dσ*pσ and ^3dσ*pσ excited states (rather than the ground state). Results obtained for Pt(pop) are very similar, showing slightly smaller energy gaps and, possibly, an additional ^1dσ*pσ – ^3dσ*pσ second order SO interaction involving higher ^1dπpσ* states that could account in part for the much faster ISC. It also appears that ^1dσ*pσ → ^3dσ*pσ ISC requires a structural distortion that has a lower barrier for Pt(pop) than for the more rigid Pt(pop-BF_2)

A Deadly Organometallic Luminescent Probe: Anticancer Activity of a Re I

The photophysical properties of [Re(CO)3 (L-N3)]Br (L-N3 =2-azido-N,N-bis[(quinolin-2-yl)methyl]ethanamine), which could not be localized in cancer cells by fluorescence microscopy, have been revisited in order to evaluate its use as a luminescent probe in a biological environment. The Re(I) complex displays concentration-dependent residual fluorescence besides the expected phosphorescence, and the nature of the emitting excited states have been evaluated by DFT and time-dependent (TD) DFT methods. The results show that fluorescence occurs from a (1) LC/MLCT state, whereas phosphorescence mainly stems from a (3) LC state, in contrast to previous assignments. We found that our luminescent probe, [Re(CO)3 (L-N3)]Br, exhibits an interesting cytotoxic activity in the low micromolar range in various cancer cell lines. Several biochemical assays were performed to unveil the cytotoxic mechanism of the organometallic Re(I) bisquinoline complex. [Re(CO)3 (L-N3)]Br was found to be stable in human plasma indicating that [Re(CO)3 (L-N3)]Br itself and not a decomposition product is responsible for the observed cytotoxicity. Addition of [Re(CO)3 (L-N3)]Br to MCF-7 breast cancer cells grown on a biosensor chip micro-bioreactor immediately led to reduced cellular respiration and increased glycolysis, indicating a large shift in cellular metabolism and inhibition of mitochondrial activity. Further analysis of respiration of isolated mitochondria clearly showed that mitochondrial respiratory activity was a direct target of [Re(CO)3 (L-N3)]Br and involved two modes of action, namely increased respiration at lower concentrations, potentially through increased proton transport through the inner mitochondrial membrane, and efficient blocking of respiration at higher concentrations. Thus, we believe that the direct targeting of mitochondria in cells by [Re(CO)3 (L-N3)]Br is responsible for the anticancer activity