Synthesis, DNA-binding and DNA-mediated luminescence quenching of Ru(II) polypyridine complexes

Comprehensive Assessment of Biomolecular Interactions of Morpholine-Based Mixed Ligand Cu(II) and Zn(II) Complexes of 2,2'-Bipyridine as Potential Anticancer and SARS-CoV-2 Agents: A Synergistic Experimental and Structure-Based Virtual Screening

A new class of pharmacologically active mixed-ligand complexes (1a-2a) [M^II(L)₂ (bpy)], where L = 2-(4-morpholinobenzylideneamino)phenol), bpy = 2,2'-bipyridine, M^II = Cu (1a), and Zn (2a), were assigned an octahedral geometry by analytical and spectral measurements. Gel electrophoresis showed that complex (1a) demonstrated the complete DNA cleavage mediated by H₂O₂. The overall DNA-binding constants observed from UV-vis, fluorometric, hydrodynamic, and electrochemical titrations were in the following sequence: (1a) > (2a) > (HL), which suggests that the complexes might intercalate DNA, a possibility that is further supported by the biothermodynamic characteristics. The binding constant results of BSA by electronic absorption and fluorometric titration demonstrate that complex (1a) exhibits the highest binding effectiveness among others, which means that all compounds could interact with BSA through a static approach, additionally supported by FRET measurements. Density FunctionalTheory (DFT) and molecular docking calculations were relied on to unveil the electronic structure, reactivity, and interacting capability of all substances with DNA, BSA, and SARS-CoV-2 main protease (Mpro). These observed binding energies fell within the following ranges: -7.7 to -8.6, -7.2 to -10.2, and -6.7 to -8.2 kcal/mol, respectively. The higher reactivity of the complexes compared to free ligand is supported by the Frontier MolecularOrbital (FMO) theory. The in vitro antibacterial, cytotoxic, and radical scavenging characteristics revealed that complex (1a) has the best biological efficacy compared to others. This is encouraged because all experimental findings are closely correlated with the theoretical measurements.

Cytotoxic Ruthenium(II) Complexes Containing a Dangling Pyridine: Selectivity for Diseased Cells Mediated by pH-Dependent DNA Binding

Ruthenium(II) complexes of the type [Ru(bpy)₂(L¹/L²/L³)]PF₆ [where bpy = 2,2'-bipyridine, H(L¹) = N-(pyrid-2-yl)salicylaldimine (1), H(L²) = N-(6-methylpyrid-2-yl)salicylaldimine (2), and H(L³) = N-(4,6-dimethylpyrid-2-yl)salicylaldimine (3)] have been isolated. The X-ray structures of 1-3 reveal distorted octahedral coordination geometry with a planar ruthenium phenolate moiety. They exhibit interpair dimeric association in their solid state such as (a) π-π-stacking interactions (1-3) and (b) C-H···π interactions (2). The ¹H NMR spectral data shed light on the characteristics of metal-ligand bonding and chelate ring conformations. The complexes exhibit strong metal-to-ligand charge-transfer transitions in the visible region. The complexes also undergo two successive metal-based oxidative processes corresponding to the Ru^II/Ru^III and Ru^III/Ru^IV couples. Resonance Raman studies strongly suggest that the lowest unoccupied molecular orbital of 1-3 is localized at the bpy ligand. Absorption, emission, and circular dichroic spectral measurements for 1-3 with calf-thymus DNA reveal a groove binding mode of interaction. Interestingly, all of the complexes exhibit pH-dependent DNA damage, and the pH at which the damage is highest corresponds to the pH conditions of the cancer cells. The DNA damage is in the order of 3 > 2 > 1, in which a hydrolytic mechanism dominates. The protein binding properties of the complexes examined by the tryptophan quenching measurements suggest a static mechanism. The positive ΔH and ΔS values indicate that the force acting between the complexes and bovine serum albumin (BSA) is mainly a hydrophobic interaction, and thus BSA may act as a targeted drug-delivery vehicle for ruthenium(II) complexes (K ∼ 10⁵). It is noteworthy that 3 exhibits selectivity with high cytotoxicity against breast cancer cells (EVSA-T and MCF-7), and its potency is comparable to that of cisplatin.

Experimental and theoretical studies of Palladium-hydrazide complexes' interaction with DNA and BSA, in vitro cytotoxicity activity and plasmid cleavage ability

New palladium complexes with general formula trans-[Pd(L)₂(OAc)₂] (1,2), (L = Benzhydrazide and 2-Furoic hydrazide) have been synthesized and characterized with various methods including elemental analysis, FT-IR, ¹HNMR and mass spectroscopy. Afterward their interactions with bovine serum albumin and calf thymus deoxyribonucleic acid have been investigated by UV-vis absorption, fluorescence emission and circular dichroism spectroscopy. Also, site-selective replacement experiments with site probes have been carried out. Analysis of fluorescence spectrum indicated static quenching mechanism. Spectroscopic measurements for DNA binding showed the groove binding to DNA for both complexes. Furthermore, cytotoxicity studies of complexes and cis-platin have been done against colon carcinoma (CT26) and breast cancer (4T1) cell lines. Evaluation of complexes (1) and (2) on induction of apoptosis in CT26 cells has been done. Finally, plasmid cleavage ability of (1) and (2) was investigated by gel electrophoresis that indicate the more activity of (1) than (2).

DNA-Binding and Anticancer Activity of Binuclear Gold(I) Alkynyl Complexes with a Phenanthrenyl Bridging Ligand

3,6-Diethynyl-9,10-diethoxyphenanthrene (4) was synthesized from phenanthrene and employed in the synthesis of the binuclear gold(I) alkynyl complexes (R3P)Au(C≡C-3-[C14H6-9,10-diethoxy]-6-C≡C)Au(PR3) (R = Ph (5a), Cy (5b)). The diyne 4 and complexes 5a and 5b were characterized by NMR spectroscopy, mass spectrometry, and elemental analysis. UV-Vis spectroscopy studies of the metal complexes and precursor diyne show strong p à p* transitions in the near UV region that red shift by ca. 50 nm upon coordination at the gold centers. The emission spectrum of 4 shows an intense fluorescence band centered at 420 nm which red shifts, slightly upon coordination of 4 to gold. Binding studies of 4, 5a, and 5b against calf thymus DNA were carried out, revealing that 4, 5a, and 5b have >40% stronger binding affinities than the commonly used intercalating agent ethidium bromide. The molecular docking scores of 4, 5a, and 5b with B-DNA suggest a similar trend in behavior to that observed in the DNA-binding study. Unlike the ligand 4, promising anticancer properties for 5a and 5b were observed against several cell lines; the DNA binding capability of the precursor alkyne was maintained, and its anticancer efficacy enhanced by the gold centers. Such phenanthrenyl complexes could be promising candidates in certain biological applications because the two components (phenanthrenyl bridge and metal centers) can be altered independently to improve the targeting of the complex, as well as the biological and physicochemical properties.

RK, Pillegowda M, Periyasamy G, Suchetan PA, Butcher RJ, Foro S, Nagaraju G. Synthesis, crystal structures, photophysical, electrochemical studies, DFT and TD-DFT calculations and Hirshfeld analysis of new 2,2′:6′,2′′-terpyridine ligands with pendant 4′-(trimethoxyphenyl) groups and their homoleptic ruthenium complexes

[Ru(L1)₂](PF₆)₂ (1) and [Ru(L2)₂](PF₆)₂ (2): X-ray structures, CH⋯F/O, OH⋯F/N, CH⋯O/π, π⋯π interactions, absorption and emission spectra, DFT/TD-DFT, Hirshfeld analysis.

Recent Developments in the Interactions of Classic Intercalated Ruthenium Compounds: [Ru(bpy)₂dppz]2+ and [Ru(phen)₂dppz]2+ with a DNA Molecule

[Ru(bpy)₂dppz]²⁺ and [Ru(phen)₂dppz]²⁺ as the light switches of the deoxyribose nucleic acid (DNA) molecule have attracted much attention and have become a powerful tool for exploring the structure of the DNA helix. Their interactions have been intensively studied because of the excellent photophysical and photochemical properties of ruthenium compounds. In this perspective, this review describes the recent developments in the interactions of these two classic intercalated compounds with a DNA helix. The mechanism of the molecular light switch effect and the selectivity of these two compounds to different forms of a DNA helix has been discussed. In addition, the specific binding modes between them have been discussed in detail, for a better understanding the mechanism of the light switch and the luminescence difference. Finally, recent studies of single molecule force spectroscopy have also been included so as to precisely interpret the kinetics, equilibrium constants, and the energy landscape during the process of the dynamic assembly of ligands into a single DNA helix.

In silico and in vitro studies of transition metal complexes derived from curcumin-isoniazid Schiff base

A series of transition metal complexes have been synthesized from biologically active curcumin and isoniazid Schiff base. They are characterized by various spectral techniques like UV-Vis, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) and mass spectroscopies. Moreover, elemental analysis, magnetic susceptibility and molar conductivity measurements are also carried out. All these data evidence that the metal complexes acquire square planar except zinc(II) which adopts a tetrahedral geometry, and they are non-electrolytic in nature. Groove mode of binding between the calf thymus DNA (CT DNA) and metal complexes is confirmed by electronic absorption titration, viscosity and cyclic voltammetry studies. In addition to that, all the metal complexes are able to cleave pUC 19 DNA. Optimized geometry and ground-state electronic structure calculations of all the synthesized compounds are established out by density functional theory (DFT) using B3LYP method which theoretically reveals that copper(II) complex explores higher stability and higher biological accessibility. This is experimentally corroborated by antimicrobial studies. In silico Absorption, Distribution, Metabolism, Excretion (ADME) studies reveal the biological potential of all synthesized complexes, and also biological activity of the ligand is predicted by PASS online biological activity prediction software. Molecular docking studies are also carried out to confirm the groove mode of binding and receptor-complex interactions.

DNA interaction of ruthenium(ii) complexes with imidazo[4,5-f][1,10]phenanthroline derivatives

The DNA interaction properties of four Ru(ii) complexes with imidazo[4,5-f][1,10]phenanthroline derivatives were investigated by spectral titration, gel electrophoresis (GAR), dynamic light scattering (DLS), zeta potential, atomic force microscopy (AFM), and transmission electron microscopy (TEM).

Synthesis, structure and biological evaluation of mixed ligand oxidovanadium(iv) complexes incorporating 2-(arylazo)phenolates

Synthesis and characterization of mixed ligand oxidovanadium(iv) complexes [V^IVO(L^1–4)(L^NN)] incorporating arylazo ligands: evaluation of DNA/BSA interaction and cytotoxicity activity.

"Chemistry-on-the-complex": functional RuII polypyridyl-type sensitizers as divergent building blocks

Ruthenium polypyridyl type complexes are potent photoactive compounds, and have found - among others - a broad range of important applications in the fields of biomedical diagnosis and phototherapy, energy conversion schemes such as dye-sensitized solar cells (DSSCs) and molecular assemblies for tailored photo-initiated processes. In this regard, the linkage of RuII polypyridyl-type complexes with specific functional moieties is highly desirable to enhance their inherent photophysical properties, e.g., with a targeting function to achieve cell selectivity, or with a dye or redox-active subunits for energy- and electron-transfer. However, the classical approach of performing ligand syntheses first and the formation of Ru complexes in the last steps imposes synthetic limitations with regard to tolerating functional groups or moieties as well as requiring lengthy convergent routes. Alternatively, the diversification of Ru complexes after coordination (termed "chemistry-on-the-complex") provides an elegant complementary approach. In addition to the Click chemistry concept, the rapidly developing synthesis and purification methodologies permit the preparation of Ru conjugates via amidation, alkylation and cross-coupling reactions. In this regard, recent developments in chromatography shifted the limits of purification, e.g., by using new commercialized surface-modified silica gels and automated instrumentation. This review provides detailed insights into applying the "chemistry-on-the-complex" concept, which is believed to stimulate the modular preparation of unpreceded molecular assemblies as well as functional materials based on Ru-based building blocks, including combinatorial approaches.

New RuII pincer complexes: synthesis, characterization and biological evaluation for photodynamic therapy

Three new ruthenium(ii) complexes of NCN pincer and phenylcyanamide derivative ligands of the formula [Ru(L)(Ph₂phen)(3,5-(NO₂)₂pcyd)], 1, [Ru(L)(Me₂phen)(3,5-(NO₂)₂pcyd)], 2, and [Ru(L)(Cl₂phen)(3,5-(NO₂)₂pcyd)], 3 (HL: 5-methoxy-1,3-bis(1-methyl-1H-benzo[d]imidazol-2-yl)benzene, 3,5-(NO₂)₂pcyd: 3,5-(NO₂)₂pcyd, Ph₂phen: 4,7-diphenyl-1,10-phenanthroline, Me₂phen: 4,7-dimethyl-1,10-phenanthroline, Cl₂phen: 4,7-dichloro-1,10-phenanthroline) have been synthesized and studied as potential photosensitizers (PSs) in photodynamic therapy (PDT). The complexes exhibited promising ¹O₂ production quantum yields comparable with PSs available on the market. The DNA-binding interactions of the complexes with calf thymus DNA have been studied by absorption, emission, and viscosity measurements. All complexes cleave SC-DNA efficiently on photoactivation at 350 nm with the formation of singlet oxygen (¹O₂) and hydroxyl radicals (˙OH) in type-II and photoredox pathways. Complexes 1-3 showed very good uptake in cervical cancer cells (HeLa). The compounds studied were found to exhibit low toxicity against HeLa cells (IC₅₀ > 300 μM) and, remarkably, on non-cancerous MRC-5 cells (IC₅₀ > 100 μM) in the dark. However, 1 showed very promising behavior with an increment of about 90 times, in its cytotoxicity upon light illumination at 420 nm in addition to very good human plasma stability.

Interfering with DNA High-Order Structures using Chiral Ruthenium(II) Complexes

In this work, it was found that DNA can undergo B-Z transformational changes and compaction in the presence of DNA intercalators such as ruthenium(II) polypyridyl complexes. The link between B-Z transition and condensation is weak but can be strengthened under certain circumstances with slight alterations to the structures of the ruthenium(II) complexes. Here, following on from previous research, this work reports a series of ruthenium(II) complexes with imidazophenanthroline ligands, which vary in size and planarity. The complexes exhibit distinct effects on DNA structures, ranging from little impact to the transformation of DNA secondary structures to the formation of higher-order DNA structures. Further studies on DNA morphological changes induced by chiral ruthenium(II) complexes are observed by atomic force microscopy and transmission electron microscopy.

Ultrasonic effect on RuO2 nanostructures prepared by direct calcination of two new Ru(II)-organic supramolecular polymers

Two novel Ru(II) complexes [(η⁶-p-cymene)RuCl(L1)]PF₆ (R1) and [(η⁶-C₆H₆)RuCl(L1)]PF₆ (R3) with ligand (E)-4-(methylthio)-N-((quinolin-2-yl)methylene)benzenamine (L1), were synthesized and investigated using elemental analysis, IR, ¹H NMR, ¹³C NMR spectroscopy and X-ray crystallography. Complexes R1 and R3 have coordination environments with formulated (η⁶-p-cymene)Ru(N₂Cl) and (η⁶-C₆H₆)Ru(N₂Cl) respectively. The thermal stabilities of compounds R1 and R3 were studied by thermal gravimetric (TG) and differential scanning calorimetry (DSC). The binding of the complexes R1 and R3 to calf thymus DNA (CT DNA) was investigated by using electronic absorption spectra, fluorescence and redox behavior studies. Such experimental data showed that there are interactions between complexes and CT-DNA and the nature of this binding is electrostatic interaction type. Calcination of ultrasonic treated R1 and R3 results in the formation of nanoparticles of RuO₂. The nanoparticles were characterized by IR spectroscopy and X-ray diffraction (XRD). Also size and morphology of nanoparticles were investigated by scanning electron microscopy (SEM).

Preparation of Different Substitued Polypyridine Ligands, Ruthenium(II)-Bridged Complexes and Spectoscopıc Studies

Novel different substitued polypyridine ligands 4-((4-(1H-imidazo[4,5-f][1,10]phenanthroline-2-yl)phenoxy)methyl)benzaldehyde (BA-PPY), (E)-N-(4-((4-(1H-imidazo[4,5-f][1,10]phenanthroline-2-yl)phenoxy)methyl)benzylidene)-pyrene-4-amine (PR-PPY), (E)-N-(4-((4-(1H-imidazo[4,5-f][1,10] phenanthroline-2-yl)phenoxy)methyl)benzylidene)-1,10-phenanthroline-5amine (FN-PPY), 2-(4-(bromomethyl)phenyl)-1H-imidazo[4,5-f][1,10] phenanthroline (BR-PPY), 2-(4-(azidomethyl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline (N3-PPY) and triazole containing polypyridine ligand 3,4-bis[(4-(metoxy)-1,2,3-triazole)1-methylphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline)] benzaldehyde (BA-DIPPY) and Ruthenium(II) complexes were synthesized and characterized. Their photopysical properties were investigated. The complexes RuP(PR-PPY), RuB(PR-PPY, RuP(FN-PPY) and RuB(FN-PPY) exhibited a broad absorption bands at 485, 475, 476, and 453 nm, respectively, assignable to the spin-allowed MLCT (dπ-π*) transition. The emission maxima of the pyrene-appended polypyridine ligand PR-PPY was observed at λems = 616 nm and the phenanthroline-appended polypyridine ligand FN-PPY was observed at λems = 668 nm. And the emission maxima of the complexes RuP(PR-PPY), RuB(PR-PPY), RuP(FN-PPY) and RuB(FN-PPY) were observed at λems = 646, 646, 685 and 685 nm, respectively. As seen in fluorescence spectra, the fluorescence intensities of the ligands are higher than their metal complexes. This is because of quenching effect of Ruthenium(II) metal on chromophore groups.

Homo- and Heterobimetallic Ruthenium(II) and Osmium(II) Complexes Based on a Pyrene-Biimidazolate Spacer as Efficient DNA-Binding Probes in the Near-Infrared Domain

We report in this work a new family of homo- and heterobimetallic complexes of the type [(bpy)2M(Py-Biimz)M'(II)(bpy)2](2+) (M = M' = Ru(II) or Os(II); M = Ru(II) and M' = Os(II)) derived from a pyrenyl-biimidazole-based bridge, 2-imidazolylpyreno[4,5-d]imidazole (Py-BiimzH2). The homobimetallic Ru(II) and Os(II) complexes were found to crystallize in monoclinic form with space group P21/n. All the complexes exhibit strong absorptions throughout the entire UV-vis region and also exhibit luminescence at room temperature. For osmium-containing complexes (2 and 3) both the absorption and emission band stretched up to the NIR region and thus afford more biofriendly conditions for probable applications in infrared imaging and phototherapeutic studies. Detailed luminescence studies indicate that the emission originates from the respective (3)MLCT excited state mainly centered in the [M(bpy)2](2+) moiety of the complexes and is only slightly affected by the pyrene moiety. The bimetallic complexes show two successive one-electron reversible metal-centered oxidations in the positive potential window and several reduction processes in the negative potential window. An efficient intramolecular electronic energy transfer is found to occur from the Ru center to the Os-based component in the heterometallic dyad. The binding studies of the complexes with DNA were thoroughly studied through different spectroscopic techniques such as UV-vis absorption, steady-state and time-resolved emission, circular dichroism, and relative DNA binding study using ethidium bromide. The intercalative mode of binding was suggested to be operative in all cases. Finally, computational studies employing DFT and TD-DFT were also carried out to interpret the experimentally observed absorption and emission bands of the complexes.

A study of DNA/BSA interaction and catalytic potential of oxidovanadium(v) complexes with ONO donor ligands

The study of DNA/BSA interaction and the catalytic potential of five mono- and dinuclear oxidoethoxido vanadium(v) complexes.

Synthesis, characterization, DNA binding and catalytic applications of Ru(III) complexes

A new series of azodye ligands 5-chloro-3-hydroxy-4-(aryldiazenyl)pyridin-2(1H)-one (HLn) were synthesized by coupling of 5-chloro-3-hydroxypyridin-2(1H)-one with aniline and its p-derivatives. These ligands and their Ru(III) complexes of the type trans-[Ru(Ln)2(AsPh3)2]Cl were characterized by elemental analyses, IR, (1)H NMR and UV-Visible spectra as well as magnetic and thermal measurements. The molar conductance measurements proved that all the complexes are electrolytes. IR spectra show that the ligands (HLn) acts as a monobasic bidentate ligand by coordinating via the nitrogen atom of the azo group (NN) and oxygen atom of the deprotonated phenolic OH group, thereby forming a six-membered chelating ring and concomitant formation of an intramolecular hydrogen bond. The molecular and electronic structures of the investigated compounds (HLn) were also studied using quantum chemical calculations. The calf thymus DNA binding activity of the ligands (HLn) and their Ru(III) complexes were studied by absorption spectra and viscosity measurements. The mechanism and the catalytic oxidation of benzyl alcohol by trans-[Ru(Ln)2(AsPh3)2]Cl with hydrogen peroxide as co-oxidant were described.

Synthesis, characterization, DNA binding and in vitro antimicrobial studies of a novel tetra-substituted N-isopropyl-N-(4-ferrocenylphenyl)-N'-(2,6-diethylphenyl)-N″-benzoylguanidine: crystallographic structure and quantum chemical computations

A novel tetra-substituted guanidine, N-isopropyl-N-(4-ferrocenylphenyl)-N'-(2,6-diethylphenyl)-N″-benzoylguanidine (1), [(CH3)2CH)(C5H5FeC5H4C6H4)NC(NHCOC6H5)(NHC6H3(CH2CH3)2] has been synthesized and characterized by elemental analysis, FT-IR, multinuclear ((1)H, (13)C) NMR spectroscopy, single crystal X-rays diffraction analysis and density functional theory based quantum chemical calculations. The torsion angles indicating that the guanidine moiety and carbonyl group are almost co-planar, due to the pseudo hexagonal ring formed by intramolecular N-H⋯O hydrogen bonds. The DNA interaction studies performed by cyclic voltammetry and UV-visible spectroscopy are in close agreement with the binding constants (K) 1.4×10(4) and 1.2×10(4) respectively. The shift in peak potential, current and absorption maxima of the studied ferrocenyl guanidine in the presence of DNA discovered that CV coupled with UV-vis spectroscopy could provide an opportunity to elaborate DNA interaction mechanism, a prerequisite for the design of new drug like agents and understanding the molecular basis of their action. The synthesized compound (1) has also been screened for their antibacterial and antifungal.

Supramolecular architecture and photophysical and biological properties of ruthenium(ii) polypyridyl complexes

A two-dimensional cyclic hybrid water–chloride anionic network has been structurally characterized in a metal–organic matrix. DNA interactions and the cytotoxicity of ruthenium(ii) complexes have been studied.

A label-free fluorescent probe for Hg²⁺ and biothiols based on graphene oxide and Ru-complex

A novel, selective and sensitive switch-on fluorescent sensor for Hg(2+) and switch-off fluorescent probe for biothiols was developed by using [Ru(bpy)₂(pip)](2+) as the signal reporter and graphene oxide (GO) as the quencher. Due to the affinity of GO towards single-stranded DNA (ss-DNA) and [Ru(bpy)₂(pip)](2+), the three components assembled, resulting in fluorescence quenching. Upon addition of Hg(2+), a double-stranded DNA (ds-DNA) via T-Hg(2+)-T base pairs was formed, and [Ru(bpy)₂(pip)](2+) intercalated into the newly formed ds-DNA. Then, [Ru(bpy)₂(pip)](2+) and ds-DNA were removed from the surface of GO, resulting in the restoration of fluorescence. Subsequently, upon addition of biothiols, Hg(2+) was released from ds-DNA, due to the higher affinity of Hg(2+) to the sulfur atoms of biothiols, which could induce ds-DNA unwinding to form ss-DNA. Then ss-DNA and [Ru(bpy)₂(pip)](2+) were adsorbed on the surface of GO, the fluorescence of [Ru(bpy)₂(pip)](2+) was quenched again. Therefore, the changes in emission intensity of [Ru(bpy)₂(pip)](2+) directly correlated to the amount of detection target (Hg(2+) or biothiols) in solution. The assay exhibited high sensitivity and selectivity, with the limits of detection for Hg(2+), cysteine (Cys) and glutathione (GSH) to be 2.34 nM, 6.20 nM and 4.60 nM, respectively.

Synthesis, Characterisation, Interaction with DNA, Cytotoxicity, and Apoptotic Studies of Ruthenium(II) Polypyridyl Complexes

We report the synthesis and characterisation of two new ruthenium(ii) polypyridyl complexes containing monodentate ancillary ligands [Ru(L)4(4HEPIP)], where L = 4-aminopyridine (1) or pyridine (2) and 4HEPIP = 2-(4-hydroxy-3-ethoxyphenyl)-1H-imidazo[4,5-f][1,10](phenanthroline). These complexes were characterised by elemental analysis and ultraviolet-visible, infrared, and 1H NMR spectroscopy. The binding properties of the two complexes towards calf thymus (CT)-DNA were investigated with different spectrophotometric methods, viscosity measurements, and salt dependent studies. Experimental results indicated that the complexes interact with CT-DNA base pairs by intercalation. Upon irradiation at 365 nm, these complexes efficiently cleave pBR322 DNA from super coiled form I to nicked form II. Their cytotoxicity on different cancer cell lines such as A549, Du145, and HeLa was investigated. The IC50 values are 39.5, 28.3, and 27.3 μM for complex 1, and 55, 67.9, and 47.9 μM for complex 2 respectively. Cellular uptake and apoptosis induced by these complexes was also studied.

DNA interaction of [Cu(dmp)(phen-dion)] (dmp=4,7 and 2,9 dimethyl phenanthroline, phen-dion=1,10-phenanthroline-5,6-dion) complexes and DNA-based electrochemical biosensor using chitosan-carbon nanotubes composite film

The interaction of two new water-soluble [Cu(4,7-dmp)(phen-dione)Cl]Cl (1) and [Cu(2,9-dmp)(phen-dione)Cl]Cl (2) which dmp is dimethyl-1,10-phenanthroline and phen-dion represents 1,10-phenanthroline-5,6-dion, with DNA in solution and immobilized DNA on a chitosan-carbon nanotubes composite modified glassy carbon electrode were investigated by cyclic voltammetry and UV-Vis spectroscopy techniques. In solution interactions, spectroscopic and electrochemical evidences indicate outside binding of these complexes. To clarify the binding mode of complexes, it was done competition studies with Hoechst and Neutral red as groove binder and intercalative probes, respectively. All these results indicating that, these two complexes (1) and (2) interact with DNA via groove binding and partially intercalative modes, respectively. The electrochemical characterization experiments showed that the nanocomposite film of chitosan-carbon nanotubes could effectively immobilize DNA and greatly improve the electron-transfer reactions of the electroactive molecules that latter finding is the result of strong interactions between captured DNA and Cu complexes. This result indicates that these complexes could be noble candidates as hybridization indicators in further studies. At the end, these new complexes showed excellent antitumor activity against K562 (human chronic myeloid leukemia) cell lines.

Synthesis, characterization, DNA binding studies, photocleavage, cytotoxicity and docking studies of ruthenium(II) light switch complexes

A new ligand 3-(1H-imidazo[4,5-f][1,10]phenanthrolin-2yl)phenylboronic acid and its (IPPBA) three ruthenium(II) complexes [Ru(phen)2(IPPBA)](ClO4)2 (1), [Ru(bpy)2(IPPBA)](ClO4)2 (2) and [Ru(dmb)2(IPPBA)](ClO4)2 (3) have been synthesized and characterized by elemental analysis, UV/VIS, IR, (1)H-NMR,(13)C-NMR and mass spectra. The binding behaviors of the three complexes to calf thymus DNA were investigated by absorption spectra, emission spectroscopy, viscosity measurements, thermal denaturation and photoactivated cleavage. The DNA-binding constants for complexes 1, 2 and 3 have been determined to be 7.9 × 10(5) M(-1), 6.7 × 10(5) M(-1) and 2.9 × 10(5) M(-1). The results suggest that these complexes bound to double-stranded DNA in an intercalation mode. Upon irradiation at 365 nm, three ruthenium complexes were found to promote the cleavage of plasmid pBR322 DNA from super coiled form І to nicked form ІІ. Further in the presence of Co(2+), the emission of DNA-Ru(ΙΙ) complexes can be quenched. And when EDTA was added, the emission was recovered. The experimental results show that all three complexes exhibited the "on-off-on" properties of molecular "light switch". The highest Cytotoxicity potential of the complex1 was observed on the Human alveolar adenocarcinoma (A549) cell line. Good agreement was generally found between the spectroscopic techniques and molecular docked model which provides further evidence of groove binding.