pH effects on optical and DNA binding properties of a thiophene-containing ruthenium(II) complex

Chiral Iridium-Based TLD-1433 Analogues: Exploration of Enantiomer-Dependent Behavior in Photodynamic Cancer Therapy

Metallodrug-based photodynamic therapy (PDT) agents have demonstrated significant superiority against cancers, while their different chirality-induced biological activities remain largely unexplored. In this work, we successfully developed a pair of enantiopure mononuclear Ir(III)-based TLD-1433 analogues, Δ-Ir-3T and Λ-Ir-3T, and their enantiomer-dependent anticancer behaviors were investigated. Photophysical measurements revealed that they display high photostability and chemical stability, strong absorption at 400 nm with high molar extinction coefficients (ε = 5.03 × 104 M-1 cm-1), and good 1O2 relative quantum yields (ΦΔ ≈ 47%). Δ- and Λ-Ir-3T showed potent efficacy against MCF-7 cancer cells, with a photocytotoxicity index of ≤44 238. This impressive result, to the best of our knowledge, represents the highest value among reported mononuclear Ir(III)-based PDT agents. Remarkably, Λ-Ir-3T tended to be more potent than Δ-Ir-3T when tested against SK-MEL-28, HepG2, and LO2 cells, with consistent results across multiple test repetitions.

Biological interaction of Pt complex with imidazole derivative as an anticancer compound with DNA: Experimental and theoretical studies

This investigation is applied to find out interesting information on DNA binding mode with Pt(II) derivative of two N, N bidentate ligands in treating cancer. Thus, one new water-soluble platinum complex with FIP and phen with a new formula of [Pt(phen)(FIP)](NO3)2 was prepared and specified. DFT data can be used to evaluate geometry parameters. Based on the ADMET prediction, this complex can be considered a drug-like agent. Cytotoxicity property was evaluated against some human cancerous MCF7, A549, and HCT116 cell lines. Accumulation of Pt complex, cisplatin, and oxaliplatin in each cancerous cell was determined, which is probably related to their lipophilicity and solubility properties. The binding mode of the complex to ct-DNA was investigated by fluorescence spectroscopy, circular dichroism, and molecular docking simulation. The viscosity of DNA by different concentrations of EB and Pt complex titration shows Pt complex interacts with DNA via groove binding like the spectroscopic binding result. In the MD study, DNA helix, RMSD, and RMSF analysis showed that DNA stability decreased and that the majority of residues left the initial state. DNA increased residual deviations and flexibility are linked to an increase in its gyratory radius, which is consistent with the findings of the experiments.

Merging of a Perylene Moiety Enables a RuII Photosensitizer with Long-Lived Excited States and the Efficient Production of Singlet Oxygen

Multichromophoric systems based on a RuII polypyridine moiety containing an additional organic chromophore are of increasing interest with respect to different light-driven applications. Here, we present the synthesis and detailed characterization of a novel RuII photosensitizer, namely [(tbbpy)2 Ru((2-(perylen-3-yl)-1H-imidazo[4,5-f][1,10]-phenanthrolline))](PF6 )2 RuipPer, that includes a merged perylene dye in the back of the ip ligand. This complex features two emissive excited states as well as a long-lived (8 μs) dark state in acetonitrile solution. Compared to prototype [(bpy)3 Ru]2+ -like complexes, a strongly altered absorption (ϵ=50.3×103  M-1  cm-1 at 467 nm) and emission behavior caused by the introduction of the perylene unit is found. A combination of spectro-electrochemistry and time-resolved spectroscopy was used to elucidate the nature of the excited states. Finally, this photosensitizer was successfully used for the efficient formation of reactive singlet oxygen.

Influence of the Protonation State on the Excited-State Dynamics of Ruthenium(II) Complexes with Imidazole π-Extended Dipyridophenazine Ligands

Ruthenium(II) complexes, like [(tbbpy)₂Ru(dppz)]²⁺ (Ru-dppz; tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine, dppz = dipyrido-[3,2-a:2',3'-c]phenazine), have emerged as suitable photosensitizers in photoredox catalysis. Since then, there has been ongoing interest in the design of π-extended Ru-dppz systems with red-shifted visible absorption maxima and sufficiently long-lived excited states independent of the solvent or pH value. Herein, we explore the photophysical properties of protonation isomers of the linearly π-extended [(tbbpy)₂Ru(L)]²⁺-type complexes bearing a dppz ligand with directly fused imidazole (im) and methyl-imidazole units (mim) as L. Steady-state UV-vis absorption, resonance Raman, as well as time-resolved emission and transient absorption spectroscopy reveal that Ru-im and Ru-mim show desirable properties for the application in photocatalytic processes, i.e., strong visible absorbance and two long-lived excited states in the ³ILCT and ³MLCT manifold, at pH values between 3 and 12. However, protonation of the (methyl-)imidazole unit at pH ≤ 2 unit causes decreased excited-state lifetimes and an emission switch-off.

Electron injection effect in In2O3 and SnO2 nanocrystals modified by ruthenium heteroleptic complexes

In this work, the optical characteristics and conductivity under photoactivation with visible light of hybrids based on nanocrystalline SnO2 or In2O3 semiconductor matrixes and heteroleptic Ru(ii) complexes were studied. The heteroleptic Ru(ii) complexes were prepared based on 1H-imidazo[4,5-f][1,10]phenanthroline and 2,2'-bipyridine ligands. Nanocrystalline semiconductor oxides were obtained by chemical precipitation with subsequent thermal annealing and characterized by XRD, SEM and single-point BET methods. The heteroleptic Ru(ii) complexes as well as hybrid materials were characterized by time-resolved luminescence and X-ray photoelectron spectroscopy. The results showed that the surface modification of SnO2 nanoparticles with heteroleptic ruthenium complexes led to an increase in conductivity upon irradiation with light appropriate for absorption by organometallic complexes. In the case of In2O3, the deposition of Ru(ii) complexes resulted in a decrease in conductivity, apparently due to the special structure of the surface layer of the semiconductor.

DNA groove-binding and acid-base properties of a Ru(II) complex containing anthryl moieties

DNA groove binders have been poorly studied as compared to the intercalators. A novel Ru(II) complex of [Ru(aeip)₂(Haip)](PF₆)₂ {Haip = 2-(9-anthryl)-1H-imidazo[4,5-f][1,10]phenanthroline and aeip = 2-(anthracen-9-yl)-1-ethyl-imidazo[4,5-f][1, 10]phenanthroline} is synthesized and characterized by elemental analysis, ¹H NMR spectroscopy and mass spectrometry. The complex is evidenced to be a calf-thymus DNA groove binder with a large intrinsic binding constant of 10⁶ M^-1 order of magnitude as supported by UV-visible absorption spectral titrations, salt effects, DNA competitive binding with ethidium bromide, DNA melting experiment, DNA viscosity measurements and density functional theory calculations. The acid-base properties of the complex studied by UV-Vis spectrophotometric titrations are reported as well.

Transition Metal Complexes and Photodynamic Therapy from a Tumor-Centered Approach: Challenges, Opportunities, and Highlights from the Development of TLD1433

Transition metal complexes are of increasing interest as photosensitizers in photodynamic therapy (PDT) and, more recently, for photochemotherapy (PCT). In recent years, Ru(II) polypyridyl complexes have emerged as promising systems for both PDT and PCT. Their rich photochemical and photophysical properties derive from a variety of excited-state electronic configurations accessible with visible and near-infrared light, and these properties can be exploited for both energy- and electron-transfer processes that can yield highly potent oxygen-dependent and/or oxygen-independent photobiological activity. Selected examples highlight the use of rational design in coordination chemistry to control the lowest-energy triplet excited-state configurations for eliciting a particular type of photoreactivity for PDT and/or PCT effects. These principles are also discussed in the context of the development of TLD1433, the first Ru(II)-based photosensitizer for PDT to enter a human clinical trial. The design of TLD1433 arose from a tumor-centered approach, as part of a complete PDT package that includes the light component and the protocol for treating non-muscle invasive bladder cancer. Briefly, this review summarizes the challenges to bringing PDT into mainstream cancer therapy. It considers the chemical and photophysical solutions that transition metal complexes offer, and it puts into context the multidisciplinary effort needed to bring a new drug to clinical trial.

Photosensitive Organic-Inorganic Hybrid Materials for Room Temperature Gas Sensor Applications

In this work, the hybrids based on nanocrystalline SnO₂ or In₂O₃ semiconductor matrixes and heterocyclic Ru(II) complex are studied as materials for gas sensors operating at room temperature under photoactivation with visible light. Nanocrystalline semiconductor oxides are obtained by chemical precipitation with subsequent thermal annealing and characterized by XRD, SEM and single-point BET methods. The heterocyclic Ru(II) complex is synthesized for the first time and investigated by ¹H NMR, ¹³C NMR APT, MALDI-MS analysis, and UV-Vis spectroscopy. The HOMO and LUMO energies of the Ru(II) complex are calculated from cyclic voltammetry data. The hybrid materials are characterized by TGA-MS analysis and EDX mapping. The optical properties of hybrids are studied by UV-Vis spectroscopy in the diffuse reflection mode. The investigation of spectral dependencies of photoconductivity of hybrid samples demonstrates that the role of organic dye consists in shifting the photosensitivity range towards longer wavelengths. Sensor measurements demonstrate that hybrid materials are able to detect NO₂ in the concentration range of 0.25⁻2 ppm without the use of thermal heating under periodic illumination with even low-energy long-wavelength (red) light.

Synthesis, characterisation and ion-binding properties of oxathiacrown ethers appended to [Ru(bpy)2]2+. Selectivity towards Hg2+, Cd2+and Pb2+

Oxathiacrown ether modified ruthenium complex2facilitates a selective naked-eye detection of Hg²⁺with an instrumental detection limit of 68 ppm.

Anticancer, antibacterial and antifungal activity of new ni (ii) and cu (ii) complexes of imidazole-phenanthroline derivatives

Two new nickel(II) and copper(II) complexes of 2-(Furan-2-yl)-1H-Imidazo[4,5-f][1,10]Phenanthroline (FIP) and 2-(thiophen-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (TIP), imidazophen derivatives were synthesized. The structures of the compounds were determined by UV-visible and FT-IR spectroscopic methods and elemental analysis. The biological activities of Ni and Cu complexes, as anticancer agents, were tested against chronic myelogenous leukemia cell line, K562, at micromolar concentration. The MTT studies showed Cc₅₀ values are 21 and 160 µM for Cu and Ni(II) complexes, respectively; suggesting that Ni (II) complex has Cc₅₀ almost seven times of that obtained for cisplatin. Biological activity of the Ni(II) and Cu(II) complexes were also assayed against selective microorganisms by disc diffusion method. These results showed that the Cu(II) complex is antifungal agent but Ni(II) complex has antibacterial activity.

Influence of Protonation State on the Excited State Dynamics of a Photobiologically Active Ru(II) Dyad

The influence of ligand protonation on the photophysics of a ruthenium (Ru) dyad bearing the 2-(1-pyrenyl)-1H-imidazo[4,5-f][1,10]-phenanthroline (ippy) ligand was investigated by time-resolved transient absorption spectroscopy. It was found that changes in the protonation state of the imidazole group led to changes in the electronic configuration of the lowest lying excited state. Formation of the fully deprotonated imidazole anion resulted in excited state signatures that were consistent with a low-lying intraligand (IL) triplet state. This assignment was supported by time-dependent density functional theory (TDDFT) calculations. IL triplet states have been suggested to be potent mediators of photodynamic effects. Thus, these results are of interest in the design of Ru metal complexes as photosensitizers (PSs) for photodynamic therapy (PDT).

DNA Binding Behavior, Sensor Studies, Antimicrobial, Photocleavage and In vitro Cytotoxicity of Synthesized Ru(II) Complexes with Assorted Intercalating Polypyridyl Ligands

The four novel Ru(II) polypyridyl complexes of [Ru(Hdpa)2dmbip](2+) (1), [Ru(Hdpa)2NO2-dmbip](2+) (2), [Ru(Hdpa)2debip](2+) (3) and [Ru(Hdpa)2OH-debip](2+) (4) where Hdpa = 2,2'-bipyridylamine, dmbip = 2-(4-N,N-dimethylbenzenamine)1H-imidazo[4,5-f][1,10]phenanthroline, debip = 2-(4-N,N-diethylbenzenamine)1H-imidazo[4,5-f][1,10]phenanthroline, NO2-dmbip = NO2-2-(4-N,N-dimethylbenzenamine)1H-imidazo[4,5-f][1,10]phenanthroline, OH-debip = OH-2-(4-N,N-diethylbenzenamine)1H-imidazo[4,5-f][1,10]phenanthroline were synthesized and fully characterized using elemental analysis, Mass, NMR and FT-IR. The DNA binding behavior of all synthesized complexes were investigated by using electronic absorption spectra, emission spectra, cyclic light switch on and off, sensor studies, electrochemical method and viscosity titrations. Docking studies were performed with human DNA TOP1 by using LibDock. Furthermore explore antimicrobial activity, photocleavage and in vitro cytotoxicity assay of four Ru(II) complexes.

DNA studies of newly synthesized heteroleptic platinum(II) complexes [Pt(bpy)(iip)](2+) and [Pt(bpy)(miip)](2.)

Two new mono-nuclear heteroleptic platinum(II) complexes, [Pt(bpy)(iip)](PF6)2 (1) and [Pt(bpy)(miip)](PF6)2·2H2O (2) (bpy is 2,2'-bipyridine; iip is 2-(imidazo-4-yl)-1H-imidazo[4,5-f] [1,10] phenanthroline; miip is 2-(1-methylimidazo-2-yl)-1H-imidazo[4,5-f] [1, 10] phenanthroline), have been synthesized and fully characterized by CHN analysis, electrospray ionization and MALDI-TOF mass spectrometry, (1)H NMR, FT-IR (ATR), and UV-Vis spectrophotometer. Cytotoxicity, ability to inhibit DNA transcription and DNAse activity of the complexes were studied. The DNA-binding behaviors of both complexes have also been studied by spectroscopic methods, cyclic voltammetry and viscosity measurements. Both complexes showed cytotoxic properties and 2 was more cytotoxic than 1. DNA transcription was inhibited upon increasing concentrations of both complexes. The complex 2 was found to be a better inhibitor than 1. The same pattern can be seen in the DNAse profile of the complexes. In addition, 2 was found to promote cleavage of pBR322 DNA at a lower concentration than 1. The spectroscopic, electrochemical and viscometric results indicate that both complexes show some degree of binding to DNA in an intercalative mode, resulting in intrinsic binding constants K b = 3.55 ± 0.6 × 10(4) M(-1) and 7.01 ± 0.9 × 10(4) M(-1) for 1 and 2, respectively. The difference in the DNA-binding affinities of 1 and 2 may presumably be explained by the methylated imidazole nitrogen atom that makes the compound more hydrophobic and gives better intercalative binding ability to DNA's hydrophobic environment.

Two star-shaped tetranuclear Ru(II) complexes containing uncoordinated imidazole groups: synthesis, characterization, photophysical and pH sensing properties

Tetrapodal ligands H4L(1) and H4L(2) containing imidazole groups have been synthesized by the reaction of 1,10-phenanthroline-5,6-dione with 1,2,4,5-tetrakis[(4-formylphenoxy)methyl]benzene and 1,2,4,5-tetrakis[(3-formylphenoxy)methyl]benzene, respectively, in presence of NH4OAc. Two star-shaped complexes [{Ru(bpy)2}4(μ4-H4L(1))](PF6)8 and [{Ru(bpy)2}4(μ4-H4L(2))](PF6)8 (bpy = 2,2'-bipyridine) have been prepared by refluxing Ru(bpy)2Cl2 ·2H2O and each ligand in ethylene glycol. The deprotonated complexes [{Ru(bpy)2}4(μ4-L(1))](PF6)4 and [{Ru(bpy)2}4(μ4-L(2))](PF6)4 have been obtained by the reaction of sodium methoxide with [{Ru(bpy)2}4(μ4-H4L(1))](PF6)8 and [{Ru(bpy)2}4(μ4-H4L(2))](PF6)8, respectively, in methanol. The pH effects on the UV-vis light absorption and emission spectra of both complexes have been studied, and ground- and excited-state ionization constants of both complexes have been derived. The photophysical properties of both complexes are strongly dependent on the solution pH. They act as proton-induced off-on-off luminescent sensors through two successive deprotonation processes of imidazole groups, with a maximum on-off ratio of 8 in buffer solution at room temperature. Theoretical calculations for the highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LOMO) orbitals of bridging ligand are also presented for plausible explanations of the fluorescence changes.

Two dinuclear Ru(II) polypyridyl complexes with different photophysical and cation recognition properties

Two dinuclear Ru(II) polypyridyl complexes functionalized with vacant coordination sites have been designed and synthesized. Their photophysical properties and interactions with various metal ions have been investigated at room temperature. The two complexes exhibit different UV/Vis absorption and emission intensities. When titrated with various metal ions, complex [{Ru(bpy)2}2(μ2-L(1))](4+) exhibits a notable fluorescence quenching in the presence of Cu(2+) in H2O-CH3CN media (1:1, v/v); its analogous complex [{Ru(bpy)2}2(μ2-L(2))](4+) exhibits no cation selectivity, the fluorescence intensity of complex [{Ru(bpy)2}2(μ2-L(2))](4+) has been enhanced by several transition metal ions due to prevention of the photo-induced electron transfer process. The fluorescence titration spectra and Benesi-Hildebrand expression reveal the formation of a 1:1 bonding mode between [{Ru(bpy)2}2(μ2-L(1))](4+) and Cu(2+) ion with the association constant of 5.50×10(4) M(-1).

pH luminescence switching, dihydrogen phosphate sensing, and cellular uptake of a heterobimetallic ruthenium(II)-rhenium(I) complex

A new heterobimetallic ruthenium(II)-rhenium(I) complex of [Ru(bpy)2(HL)Re(CO)3Cl](ClO4)2·6H2O (RuHLRe) {bpy = 2,2'-bipyridine and HL = 2-(4-(2,6-di(pyridin-2-yl)pyridin-4-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} was synthesised and characterised by elemental analysis, proton nuclear magnetic resonance spectroscopy, and mass spectrometry. The ground- and excited-state acid-base properties of RuHLRe were studied using UV-Vis absorption spectrophotometric and spectrofluorimetric titrations in a 100 : 1 (v/v) Britton-Robinson buffer-CH3CN solution combined with luminescence lifetime measurements. The complex exhibited two-step separate protonation-deprotonation processes in both the ground and excited states. The complex acted as pH-induced "off-on-off" luminescence switches (I(on)/I(off) = 31.0 and 14.6), with one of the switching actions being driven by pH variations over the physiological pH range (5.3-8.0). Importantly, cellular imaging and cytotoxicity experiments demonstrated that RuHLRe rapidly and selectively illuminated the membrane of HeLa cells over fixed cells and exhibited reduced cytotoxicity at the imaging concentration compared to the Re(I)-free parent Ru(II) complex. In addition, RuHLRe acted as an efficient "turn on" emission sensor for H2PO4(-) and "turn off" emission sensor for F(-) and OAc(-).

Dual topoisomerase I and II poisoning by chiral Ru(II) complexes containing 2-thiophenylimidazo[4,5-f][1,10]phenanthroline derivatives

A series of chiral Ru(II) complexes bearing thiophene ligands were synthesized and characterized. Both Ru(II) complexes Δ/Λ-[Ru(bpy)2(pscl)](2+) (Δ/Λ-1) and Δ/Λ-[Ru(bpy)2(psbr)](2+) (Δ/Λ-2) (bpy=2,2'-bipyridine, pscl=2-(5-chlorothiophen-2-yl)imidazo[4,5-f][1,10]phenanthroline, psbr=2-(5-bromothiophen-2-yl)imidazo[4,5-f][1,10]phenanthroline) showed antitumor activities against A549, HepG2 and BEL-7402 tumor cell lines, especially HeLa tumor cell line. Moreover, Δ enantiomers were more active than Λ enantiomers, accounting for the different cellular uptake. In addition, with the extension of time, these enantiomers could finally accumulate in the nucleus, suggesting that nucleic acids were the cellular target of these enantiomers. The DNA-binding behaviors of complexes were studied using spectroscopic and viscosity measurements. Results suggested that four complexes could bind to DNA in an intercalative mode but no obvious DNA-binding selectivity between the enantiomers was observed. Topoisomerase inhibition and DNA religation assay confirmed that four complexes acted as efficient dual topoisomerase I and II poisons, DNA strand breaks had also been observed from alkaline single cell gel electrophoresis (comet assay). Δ-1 and Δ-2 inhibited the growth of HeLa cells through the induction of apoptotic cell death, as evidenced by the Alexa Fluor® 488 annexin V staining assays and flow cytometry analysis. The results demonstrated that Δ/Λ-1 and Δ/Λ-2 acted as dual topoisomerase I and II poisons and caused DNA damage that could lead to cell cycle arrest by apoptosis.

Luminescent pH sensor of a novel imidazole-containing hexanuclear Ru(II) polypyridyl complex

Hexapodal ligand H6L containing imidazole rings has been prepared by the reaction of 1,10-phenanthroline-5,6-dione with 1,2,3,4,5,6-hexakis[(3-formylphenoxy)methyl]benzene. The Ru(II) polypyridyl complex [{Ru(bpy)2}6(μ6-H6L)](PF6)12 (bpy=2,2'-bipyridine) has been synthesized by the reaction of Ru(bpy)2Cl2·2H2O with ligand H6L. The pH effects on the UV-vis absorption and emission spectra of the complex have been studied. The ground- and excited-state ionization constants of the acid-base equilibria have been calculated according to the absorbance and emission data. The complex acts as an off-on-off luminescent pH sensor through two successive deprotonation processes of imidazole rings, with a maximum on-off ratio of 5 in buffer solution.

The effects of linear assembly of two carbazole groups on acid-base and DNA-binding properties of a ruthenium(II) complex

A novel Ru(II) complex of [Ru(bpy)2(Hbcpip)](ClO4)2 {where bpy=2,2-bipyridine, Hbcpip=2-(4-(9H-3,9'-bicarbazol-9-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} is synthesized and characterized. Calf-thymus DNA-binding properties of the complex were studied by UV-vis absorption and luminescence titrations, steady-state emission quenching by [Fe(CN)6](4-), DNA competitive binding with ethidium bromide, thermal denaturation and DNA viscosity measurements. The results indicate that the complex partially intercalated into the DNA with a binding constant of (5.5±1.4)×10(5) M(-1) in buffered 50 mM NaCl. The acid-base properties of the complex were also studied by UV-visible and luminescence spectrophotometric pH titrations, and ground- and excited-state acidity ionization constant values were derived.