Photoinduced Energy and Electron-Transfer Reactions by Polypyridine Ruthenium(II) Complexes Containing a Derivatized Perylene Diimide

The [Ru­(II) (phen)₂(pPDIp)]²⁺ complex, where pPDIp is the symmetric bridging ligand phenanthroline–perylene–phenanthroline, shows strong electronic absorption bands attributed to the pPDIp and {Ru­(phen)₂}²⁺ moieties in acetonitrile. The charge-separated intermediate {Ru­(III) (phen)₂(pPDIp^–•)} was detected by transient absorption spectroscopy upon electronic excitation in either the pPDIp or the complex moieties. The charge-separated intermediate species decays to generate the triplet state ³*pPDIp-Ru­(II) (τ_P = 1.8 μs) that sensitizes the formation of singlet molecular oxygen with quantum yield ϕ_Δ = 0.57. The dyad in deaerated acetonitrile solutions is reduced by triethylamine (NEt₃) to the [Ru­(II) (phen)₂(pPDIp^•–)] radical anion in the dark. The electron-transfer reaction is accelerated by light absorption. By photolysis of the radical anion, a second electron transfer reaction occurs to generate the [Ru­(II) (phen)₂(pPDIp^2–)] dianion. The changes of the color of solution indicate the redox states of complexes and offer a sensitive reporter of each stage of redox reaction from start to finish. The reduced complexes can be converted to the initial complex, using methyl viologen or molecular oxygen as an electron acceptor. The accumulation of electrons in two well-separated steps opens promising opportunities such as in catalysis

Modulation of the Excited States of Ruthenium(II)-perylene Dyad to Access Near-IR Luminescence, Long-Lived Perylene Triplet State and Singlet Oxygen Photosensitization

Herein, we present a novel ruthenium(II)-perylene dyad (RuPDI-Py) that combines the photophysical properties of pyrrolidine-substituted perylene diimide (PDI-Py) and the ruthenium(II) polypyridine complex [Ru(phen)3]2+. A comprehensive study of excited-state dynamics was carried out using time-resolved and steady-state methods in a dimethyl sulfoxide solution. The RuPDI-Py dyad demonstrated excitation wavelength-dependent photophysical behavior. Upon photoexcitation above 600 nm, the dyad exclusively exhibits the near-infrared (NIR) fluorescence of the 1PDI-Py state at 785 nm (τfl = 1.50 ns). In contrast, upon photoexcitation between 350 and 450 nm, the dyad also exhibits a photoinduced electron transfer from the {[Ru(phen)3]2+} moiety to PDI-Py, generating the charge-separated intermediate state {Ru(III)-(PDI-Py)•–} (4 μs). This state subsequently decays to the long-lived triplet excited state 3PDI-Py (36 μs), which is able to sensitize singlet oxygen (1O2). Overall, tuning 1O2 photoactivation or NIR fluorescence makes RuPDI-Py a promising candidate for using absorbed light energy to perform the desired functions in theranostic applications

Luminescent Ruthenium Complexes for Theranostic Applications

The water-soluble and visible luminescent complexes <i>cis-</i>[Ru­(L-L)₂(L)₂]²⁺ where L-L = 2,2-bipyridine and 1,10-phenanthroline and L= imidazole, 1-methylimidazole, and histamine have been synthesized and characterized by spectroscopic techniques. Spectroscopic (circular dichroism, saturation transfer difference NMR, and diffusion ordered spectroscopy NMR) and isothermal titration calorimetry studies indicate binding of <i>cis-</i>[Ru­(phen)₂(ImH)₂]²⁺ and human serum albumin occurs via noncovalent interactions with <i>K</i>_b = 9.8 × 10⁴ mol^–1 L, Δ<i>H</i> = −11.5 ± 0.1 kcal mol^–1, and <i>T</i>Δ<i>S</i> = −4.46 ± 0.3 kcal mol^–1. High uptake of the complex into HCT116 cells was detected by luminescent confocal microscopy. Cytotoxicity of <i>cis-</i>[Ru­(phen)₂(ImH)₂]²⁺ against proliferation of HCT116p53^+/+ and HCT116p53^–/– shows IC₅₀ values of 0.1 and 0.7 μmol L^–1. Flow cytometry and western blot indicate RuphenImH mediates cell cycle arrest in the G1 phase in both cells and is more prominent in p53^+/+. The complex activates proapoptotic PARP in p53^–/–, but not in p53^+/+. A cytostatic mechanism based on quantification of the number of cells during the time period of incubation is suggested

Luminescent Ruthenium Complexes for Theranostic Applications

The water-soluble and visible luminescent complexes <i>cis-</i>[Ru­(L-L)₂(L)₂]²⁺ where L-L = 2,2-bipyridine and 1,10-phenanthroline and L= imidazole, 1-methylimidazole, and histamine have been synthesized and characterized by spectroscopic techniques. Spectroscopic (circular dichroism, saturation transfer difference NMR, and diffusion ordered spectroscopy NMR) and isothermal titration calorimetry studies indicate binding of <i>cis-</i>[Ru­(phen)₂(ImH)₂]²⁺ and human serum albumin occurs via noncovalent interactions with <i>K</i>_b = 9.8 × 10⁴ mol^–1 L, Δ<i>H</i> = −11.5 ± 0.1 kcal mol^–1, and <i>T</i>Δ<i>S</i> = −4.46 ± 0.3 kcal mol^–1. High uptake of the complex into HCT116 cells was detected by luminescent confocal microscopy. Cytotoxicity of <i>cis-</i>[Ru­(phen)₂(ImH)₂]²⁺ against proliferation of HCT116p53^+/+ and HCT116p53^–/– shows IC₅₀ values of 0.1 and 0.7 μmol L^–1. Flow cytometry and western blot indicate RuphenImH mediates cell cycle arrest in the G1 phase in both cells and is more prominent in p53^+/+. The complex activates proapoptotic PARP in p53^–/–, but not in p53^+/+. A cytostatic mechanism based on quantification of the number of cells during the time period of incubation is suggested

Temperature-Driven Isosymmetric Reversible Phase Transition of the Hormone Estradiol 17β Valerate

The hormone estradiol 17β valerate (E2V), used in hormone replacement therapy, undergoes a structural phase transition at 251.1 K on cooling. The crystalline structures of the low and room temperature phases were determined showing that neither the space group nor the site symmetry and number of atoms are altered. These phases are related by a large conformational reorientation of the valerate chain. In addition, thermal analysis, solid state nuclear magnetic resonance, and infrared spectroscopy show that the transformation is reversible, discontinuous, and first order, evidencing the occurrence of an isosymmetric phase transition, rare for organic compounds