Correlating photochemical H production and excited state lifetimes of heterostructured and doped ZnCdS nanoparticles.

A variety of ZnCdS-based semiconductor nanoparticle heterostructures with extended exciton lifetimes were synthesized to enhance the efficacy of photocatalytic hydrogen production in water. Specifically, doped nanoparticles (NPs), as well as core/shell NPs with and without palladium and platinum co-catalysts, were solubilized into water using various methods to assess their efficacy for solar H fuel synthesis. The best results were obtained with low bandgap ZnCdS cores and ZnCdS/ZnS core/shell NPs with palladium co-catalysts.

Heavy atom effects on synthetic pyranoanthocyanin analogues.

Pyranoflavylium cations are synthetic analogues of pyranoanthocyanins, the much more color-stable compounds that are formed spontaneously from grape anthocyanins during the maturation of red wines. In the present work, our studies of the photophysical properties of pyranoanthocyanin analogues are extended to include nine pyranoflavylium cations substituted with one or two bromo and/or iodo heavy atoms. The room temperature fluorescence, 77 K fluorescence and phosphorescence, triplet formation in solution, and sensitized singlet oxygen formation, with excited state acidity suppressed by the addition of trifluoroacetic acid, are compared to those of similar pyranoflavylium cations that do not contain a heavy atom.

Targeted Modulation of Photocatalytic Hydrogen Evolution Activity by Nickel-Substituted Rubredoxin through Functionalized Ruthenium Phototriggers.

Light-driven hydrogen evolution is a promising means of sustainable energy production to meet global energy demand. This study investigates the photocatalytic hydrogen evolution activity of nickel-substituted rubredoxin (NiRd), an artificial hydrogenase mimic, covalently attached to a ruthenium phototrigger (RuNiRd). By systematically modifying the para-substituents on Ru(II) polypyridyl complexes, we sought to optimize the intramolecular electron transfer processes within the RuNiRd system.

Photo- and Electrocatalytic Hydrogen Evolution by Heteroleptic Dirhodium(II,II) Complexes: Role of the Bridging and Diimine Ligands.

A series of heteroleptic Rh(II,II) complexes, [Rh(μ-DPhF)(μ-bncn)] (; bncn = benzo[]cinnoline), [Rh(μ-DPhF)(μ-OAc)(μ-bncn)] (), and [Rh(μ-OAc)(μ-bncn)] (), is presented, and the excited state and redox properties of each complex was characterized for the photo- and electrocatalytic production of H. The oxidation potentials shift anodically from to , consistent with a highest occupied molecular orbital (HOMO) with significant metal-ligand mixing, Rh(δ*)/DPhF(π/nb). In contrast, modest differences in the first two bncn-localized reversible reduction potentials were observed in - .

Mixed Ru(II)-Ir(III) Complexes as Photoactive Inhibitors of the Major Human Drug Metabolizing Enzyme CYP3A4.

Cytochrome P450 3A4 (CYP3A4) is a crucial enzyme in human drug metabolism. To garner photochemical control over the inhibition of CYP3A4, a potent Ir(III)-based inhibitor of CYP3A4 was complexed with two Ru(II)-based photocaging groups. Chemical, photochemical, and biological properties of the photocaged inhibitors were characterized.

Ru(II)-Photoactive Agents for Targeting ER Stress and Immunogenic Cell Death.

Immunotherapy has emerged as a promising avenue for cancer treatment by bolstering the immune system's ability to recognize and attack cancer cells. Photodynamic therapy shows potential in enhancing antitumor immunity, though the mechanisms behind its success are not fully understood. In this manuscript, we investigate two previously reported green light activated PCT/PDT agents where compound - [Ru(tpy)(Me2bpy)( )] , (tpy = 2,2':6',2''- terpyridine, Me2bpy = 6,6'-dimethyl-2,2'-bipyridine, = pyridyl-BODIPY-I2,) - shows remarkable photoselectivity in assays containing both 2D cancer cells and 3D cocultures containing BALB/c macrophages and 4T1 murine breast cancer cells.

Ru(II) Complexes with Absorption in the Photodynamic Therapy Window: O Sensitization, DNA Binding, and Plasmid DNA Photocleavage.

Two Ru(II) complexes, [Ru(pydppn)(bim)(py)] [; pydppn = 3-(pyrid-2'-yl)-4,5,9,16-tetraaza-dibenzo[]naphthacene; bim = 2,2'-bisimidazole; py = pyridine] and [Ru(pydppn)(Mebim)(py)] [; Mebim = 2,2'-bis(4,5-dimethylimidazole)], were synthesized and characterized, and their photophysical properties, DNA binding, and photocleavage were evaluated and compared to [Ru(pydppn)(bpy)(py)] (; bpy = 2,2'-bipyridine). Complexes and exhibit broad MLCT (metal-to-ligand charge transfer) transitions with maxima at ∼470 nm and shoulders at ∼525 and ∼600 nm that extend to ∼800 nm. These bands are red-shifted relative to those of , attributed to the π-donating ability of the bim and Mebim ligands.

Ruthenium-Cathepsin Inhibitor Conjugates for Green Light-Activated Photodynamic Therapy and Photochemotherapy.

Dysregulated cathepsin activity is linked to various human diseases including metabolic disorders, autoimmune conditions, and cancer. Given the overexpression of cathepsin in the tumor microenvironment, cathepsin inhibitors are promising pharmacological agents and drug delivery vehicles for cancer treatment. In this study, we describe the synthesis and photochemical and biological assessment of a dual-action agent based on ruthenium that is conjugated with a cathepsin inhibitor, designed for both photodynamic therapy (PDT) and photochemotherapy (PCT).

Water-Mediated Charge Transfer and Electron Localization in a CoFe Cyanide-Bridged Trigonal Bipyramidal Complex.

The effects of temperature and chemical environment on a pentanuclear cyanide-bridged, trigonal bipyramidal molecular paramagnet have been investigated. Using element- and oxidation state-specific near-ambient pressure X-ray photoemission spectroscopy (NAP-XPS) to probe charge transfer and second order, nonlinear vibrational spectroscopy, which is sensitive to symmetry changes based on charge (de)localization coupled with DFT, a detailed picture of environmental effects on charge-transfer-induced spin transitions is presented. The molecular cluster, CoFe(tmphen)(μ-CN)(-CN), abbrev.

Differences in Photophysical Properties and Photochemistry of Ru(II)-Terpyridine Complexes of CHCN and Pyridine.

A series of 22 Ru(II) complexes of the type [Ru(tpy)(L)(L')], where tpy is the tridentate ligand 2,2';6,2″-terpyridine, L represents bidentate ligands with varying electron-donating ability, and L' is acetonitrile (-) or pyridine (-), were investigated. The dissociation of acetonitrile occurs from the MLCT state in -, such that it does not require the population of a LF state. Electrochemistry and spectroscopic data demonstrate that the ground states of these series do not differ significantly.

Ligand-Centered Photocatalytic Hydrogen Production in an Axially Capped Rh(II,II) Paddlewheel Complex with Red Light.

A new series of Rh(II,II) complexes with the formula -[Rh(DTolF)(bpnp)(L)], where bpnp = 2,7-bis(2-pyridyl)-1,8-naphthyridine, DTolF = ,-di(-tolyl) formamidinate, and L = pdz (pyridazine; ), cinn (cinnoline; ), and bncn (benzo[]cinnoline; ), were synthesized from the precursor -[Rh(DTolF)(bpnp)(CHCN)] (). The first reduction couple in is localized on the bpnp ligand at approximately -0.52 V vs Ag/AgCl in CHCN (0.

Etalon-Assisted Study of the Strong CO Ligand Vibrations of the -[Re(CO)(bpy)(CHCN)] Octahedral Complex.

The strong CO ligand vibrations of an octahedral complex, [Re (CO)(bpy)(CHCN)], in acetonitrile are observed at 2040 and 1932 cm. Facial rhenium tricarbonyl systems offer very strong and isolated CO vibrations with the potential for interactions between these vibrations. This work first identifies the dominant ion-pair species using attenuated total reflection infrared (ATR-IR) absorption spectra on a dilution series and then determines the strength of these CO ligand vibrations (as isolated vibrations) with a combination of ATR-IR and etalon-based measurements that determine the absolute complex index of refraction of the solution.

Dynamic Ir(III) Photosensors for the Major Human Drug-Metabolizing Enzyme Cytochrome P450 3A4.

Probing the activity of cytochrome P450 3A4 (CYP3A4) is critical for monitoring the metabolism of pharmaceuticals and identifying drug-drug interactions. A library of Ir(III) probes that detect occupancy of the CYP3A4 active site were synthesized and characterized. These probes show selectivity for CYP3A4 inhibition, low cellular toxicity, values as low as 9 nM, and are highly emissive with lifetimes up to 3.

Etalon-Assisted Determination of the Complex Index of Refraction of a Solution for the Study of Strong Cavity-Vibrational Coupling of PF in Acetonitrile.

A new method is established using an etalon cavity to assist in the determination of the wavelength-dependent complex index of refraction of a solution throughout the mid-infrared range. The results are used to study the cavity-vibration polaritons of PF in acetonitrile. Mixed states are formed by placing solution inside a pair of parallel plate mirrors with a wavelength-scale spacing, .

Electrochemical Strategy for Proton Relay Installation Enhances the Activity of a Hydrogen Evolution Electrocatalyst.

A new method to install a proton relay that enhances the reactivity near an active catalytic site for H production is reported, afforded by the electrochemical reduction and protonation of one of the ligands in the paddlewheel Rh(II,II) hydrogen evolution complex, -[Rh(DPhF)(bncn)] (; DPhF = N,'-diphenylformamidinate, bncn = benzo[]cinnoline). An electrochemical reversible prewave is observed for at potentials more positive than the first bncn-centered reduction couple in the presence of strong acids, observed at -0.72 V vs Fc (Fc = ferrocene) in the cyclic voltammograms (CVs) in DMF (0.

Acetonitrile Ligand Photosubstitution in Ru(II) Complexes Directly from the MLCT State.

The excited states of the series [Ru(tpy)(L)(CHCN)] (-) ( = 1, 2) containing bidentate ligands L with varying electron-donating ability were characterized through Arrhenius analysis of the temperature dependence of their excited-state lifetimes. Complexes - undergo photoinduced CHCN dissociation upon 450 nm irradiation with ligand exchange quantum yields that increase with the energy barrier to populating a dissociative triplet ligand field (LF) state from the lowest-energy triplet metal-to-ligand charge transfer (MLCT) excited state. Combined with DFT calculations, the data indicate that ligand photodissociation in - occurs directly from the MLCT state instead of a LF state.

Ir(III)-Based Agents for Monitoring the Cytochrome P450 3A4 Active Site Occupancy.

Cytochromes P450 (CYPs) are a superfamily of enzymes responsible for biosynthesis and drug metabolism. Monitoring the activity of CYP3A4, the major human drug-metabolizing enzyme, is vital for assessing the metabolism of pharmaceuticals and identifying harmful drug-drug interactions. Existing probes for CYP3A4 are irreversible turn-on substrates that monitor activity at specific time points in end-point assays.

Two-photon-absorbing ruthenium complexes enable near infrared light-driven photocatalysis.

One-photon-absorbing photosensitizers are commonly used in homogeneous photocatalysis which require the absorption of ultraviolet (UV) /visible light to populate the desired excited states with adequate energy and lifetime. Nevertheless, the limited penetration depth and competing absorption by organic substrates of UV/visible light calls upon exploring the utilization of longer-wavelength irradiation, such as near-infrared light (λ > 700 nm). Despite being found applications in photodynamic therapy and bioimaging, two-photon absorption (TPA), the simultaneous absorption of two photons by one molecule, has been rarely explored in homogeneous photocatalysis.

Photocytotoxicity and photoinduced phosphine ligand exchange in a Ru(ii) polypyridyl complex.

Two new tris-heteroleptic Ru(ii) complexes with triphenylphosphine (PPh) coordination, -[Ru(phen)(PPh)(CHCN)] (1a, phen = 1,10-phenanthroline) and -[Ru(biq)(phen)(PPh)(CHCN)] (2a, biq = 2,2'-biquinoline), were synthesized and characterized for photochemotherapeutic applications. Upon absorption of visible light, 1a exchanges a CHCN ligand for a solvent water molecule. Surprisingly, the steady-state irradiation of 2a followed by electronic absorption and NMR spectroscopies reveals the photosubstitution of the PPh ligand.

Unlocking the Potential of Ru(II) Dual-action Compounds with the Power of the Heavy-atom Effect.

We report the synthesis, photochemical and biological characterization of two new Ru(II) photoactivated complexes based on [Ru(tpy)(Me bpy)(L)] (tpy = 2,2':6',2''-terpyridine, Me bpy = 6,6'-dimethyl-2,2'-bipyridine), where L = pyridyl-BODIPY (pyBOD). Two pyBOD ligands were prepared bearing flanking hydrogen or iodine atoms. Ru(II)-bound BODIPY dyes show a red-shift of absorption maxima relative to the free dyes and undergo photodissociation of BODIPY ligands with green light irradiation.

Ru(II)-Based Acetylacetonate Complexes Induce Apoptosis Selectively in Cancer Cells.

The synthesis, chemical and biological characterization of seven Ru(II) polypyridyl complexes containing acetylacetonate (acac) ligands are reported. Electronic absorption spectra were determined and electrochemical potentials consistent with Ru(III/II) couples ranging from +0.60 to +0.

Trifluoromethyl substitution enhances photoinduced activity against breast cancer cells but reduces ligand exchange in Ru(ii) complex.

A series of five ruthenium complexes containing triphenyl phosphine groups known to enhance both cellular penetration and photoinduced ligand exchange, -[Ru(bpy)(P(-R-Ph))(CHCN)], where bpy = 2,2'-bipyridine and P(-R-Ph) represent -substituted triphenylphosphine ligands with R = -OCH (), -CH () -H (), -F (), and -CF (), were synthesized and characterized. The photolysis of in water with visible light ( ≥ 395 nm) results in the substitution of the coordinated acetonitrile with a solvent molecule, generating the corresponding aqua complex as the single photoproduct. A 3-fold variation in quantum yield was measured with 400 nm irradiation, , where is the most efficient with a = 0.