DNA binding and nuclease activity of cationic iron(IV) and manganese(III) corrole complexes

Cationic meso(4‐N‐methylpyridyl)‐based metallocorroles, μ‐oxo iron corrole dimer ( 1b ) and manganese corrole monomer ( 2b ), were synthesized and characterized. The interactions of these two metal corrole complexes with CT‐DNA were studied by UV–visible, fluorescence and circular dichroism spectroscopic methods, as well as by viscosity measurements. The results revealed that 1b interacts with CT‐DNA in a difunctional binding mode, i.e. non‐classical intercalation and outside groove binding with H‐aggregation, while 2b can interact with CT‐DNA via an outside groove binding mode only. The binding constants K_b of 1b and 2b were 4.71 × 10⁵ m ^?1 and 2.17 × 10⁵ m ^?1, respectively, indicating that 1b can bind more tightly to CT‐DNA than 2b . Furthermore, both complexes may cleave the supercoiled plasmid DNA efficiently in the presence of hydrogen peroxide or tert‐butyl hydroperoxide (TBHP), albeit 1b exhibited a little higher efficiency. The inhibitor tests suggested that singlet oxygen and high‐valent (oxo)iron(VI) corrole or (oxo)manganese(V) corrole might be the active intermediates responsible for the oxidative DNA scission. Copyright © 2014 John Wiley & Sons, Ltd.     

Novel cytotoxic oxovanadium(IV) complexes: Influence of pyrazole‐incorporated heterocyclic scaffolds on their biological response

Homoleptic VO^IV complexes with bidentate heterocycles, namely bipyrazole/pyrimidin‐2‐amine/triazolopyrimidine derivatives, are novel square pyramidal oxovanadium(IV) complexes. Their identities have been established using physicochemical techniques, namely elemental and spectral (ESI‐MS, IR, UV–visible) analyses. The in vitro antibacterial activities against Gram‐negative and Gram‐positive microorganisms have been studied for all compounds, exhibiting good inhibition as compared to the ligands. In addition, all compounds exhibit significant cytotoxicity towards brine shrimp with LD₅₀ values obtained in the range 8–24 μg ml⁻¹. Cellular level cytotoxicity has been investigated using bioassay of Schizosaccharomyces pombe , the complexes showing inevitable viability as concentration increases. Notably, UV absorption spectral titrations of the synthesized complexes with DNA reveal that the complexes bind to calf thymus DNA (CT‐DNA) through intercalation mode (K _b = 10⁴–10⁵ M⁻¹). Molecular docking reveals that the compounds are stacked between the base pairs of DNA. The results suggest that the complexes show promising binding affinity compared to the ligands towards CT‐DNA.     

Isomeric Effect on the anticancer Behavior of two Zinc (II) complexes based on 3,5‐bis(1‐imidazoly) pyridine: Experimental and Theoretical Approach

Two isomeric Zinc (II) complexes constructed by 3,5‐bis(1‐imidazoly) pyridine has been synthesized and characterized by single crystal X‐ray diffraction, elemental analyses and infrared spectroscopy. The binding mode and ability of complex 1–2 with CT‐DNA were studied by UV and fluorescence spectra. The intrinsic binding constant K_b (K_b1 = 2.305 × 10⁴ M^?1, K_b2 = 3.095 × 10⁴ M^?1) and the observed association constant K_obs (K_obs1 = 1.523*10⁶ M^?1, K_obs2 = 2.057*10⁶ M^?1) indicated that the insertion ability of complex 2 with CT‐DNA is stronger than complex 1. Gel electrophoresis showed that complexes have a good ability to hydrolyze cleavage pBR322 plasmid DNA. The cytotoxicity and apoptosis studies showed that complexes exhibited excellent cytotoxic activity against HeLa cells, especially complex 2 had better growth inhibition than Cisplatin. Molecular docking study simulated the binding model of complexes with DNA (PDB:4av1), showing an imidazole plane of complex 2 can be inserted into a DNA base pair in relative parallel. Both complexes can be used as potential anticancer agents.     

In vitro biomolecular interaction studies and cytotoxic activities of copper(II) and zinc(II) complexes bearing ONS donor thiosemicarbazones

Among all the bio‐metals, zinc and copper derivatives of ONS donor thiosemicarbazone have aroused great interest because of their potential biological applications. Multisubstituted thiosemicarbazone ligand H₂dspt (3,5‐dichlorosalicylaldehyde‐N⁴‐phenylthiosemicarbazone) derived new ternary complexes like [Zn(dspt)(phen)]?DMF ( 1 ) and [Cu(dspt)(phen)]?DMF ( 2 ), and another thiosemicarbazone, H₂dsct (3,5‐dichlorosalicylaldehyde‐N⁴‐cyclohexylthiosemicarbazone), derived [Cu(dsct)(bipy)]?DMF ( 3 ). These complexes have been characterized by elemental analysis (CHNS), Fourier transform infrared (FT‐IR), ultraviolet–visible (UV–Vis) and proton nuclear magnetic resonance (¹H‐NMR) spectra. The structures of the complexes were obtained by single‐crystal X‐ray diffraction analysis. Compounds 1 and 2 got crystallized in the monoclinic P2₁/c space group. The complexes showed interesting supramolecular interaction, which in turn stabilizes the complexes. The ground state electronic configurations of the complexes were studied using the B3LYP/LANL2DZ basis set, and ESP plots of complexes were investigated. The interaction of the complexes with calf thymus DNA (CT‐DNA) was studied using absorption and fluorescence spectroscopic methods. A UV study of the interaction of the complexes with calf thymus DNA (CT‐DNA) has shown that the complexes can effectively bind to CT‐DNA, and [Cu(dspt)(phen)]·DMF ( 2 ) exhibited the highest binding constant to CT‐DNA (K_b = 3.7 × 10⁴). Fluorescence spectral studies also indicated that Complex 2 binds relatively stronger with CT DNA through intercalative mode, exhibiting higher binding constant (K_q = 4.7 × 10⁵). The DNA cleavage result showed that the complexes are capable of cleaving the DNA without the help of any external agent. Molecular docking studies were carried out to understand the binding of complexes with the molecular target DNA. Complex 2 exhibited the highest cytotoxicity against human breast cancer cell line MD‐MBA‐231 (IC₅₀ = 23.93 μg/mL) as compared to Complex 1 (IC₅₀ = 44.40 μg/mL) .     

New anthracene based Schiff base ligands appended Cu(II) complexes: Theoretical study,DNA binding and cleavage activities

New anthracene based Schiff base ligands L ¹ and H( L ² ), their Cu(II) complexes [Cu( L ¹ )Cl₂] ( 1 ) and [Cu( L ² )Cl] ( 2 ) , (where L ¹  = N¹,N²‐bis(anthracene‐9‐methylene)benzene‐1,2‐diamine, L ²  = (2Z,4E)‐4‐(2‐(anthracen‐9‐ylmethyleneamino)phenylimino)pent‐2‐en‐2‐ol) have been prepared and characterized by elemental analysis, NMR, FAB‐mass, EPR, FT‐IR, UV–Vis and cyclic voltammetry. The electronic structures and geometrical parameters of complexes 1 and 2 were analyzed by the theoretical B3LYP/DFT method. The interaction of these complexes 1 and 2 with CT‐DNA has been explored by using absorption, cyclic voltammetric and CD spectral studies. From the electronic absorption spectral studies, it was found that the DNA binding constants of complexes 1 and 2 are 8.7 × 10³ and 7.0 × 10⁴ M^?1, respectively. From electrochemical studies, the ratio of DNA binding constants K₊/K₂₊ for 2 has been estimated to be >1. The high binding constant values, K₊/K₂₊ ratios more than unity and positive shift of voltammetric E_1/2 value on titration with DNA for complex 2 suggest that they bind more avidly with DNA than complex 1 . The inability to affect the conformational changes of DNA in the CD spectrum is the definite evidences of electrostatic binding by the complex 1 . It can be assumed that it is the bulky anthracene unit which sterically inhibits these complexes 1 and 2 from intercalation and thereby remains in the groove or electrostatic. The complex 2 hardly cleaves supercoiled pUC18 plasmid DNA in the presence of hydrogen peroxide. The results suggest that complex 2 bind to DNA through minor groove binding.     

Ni(II) Ternary Complex Based on Antimicrobial Drug Enoxacin: Synthesis and Biological Properties

First Ni(II) ternary complex using the quinolone antibacterial agent enoxacin (HEn) as ligand and 1,10‐phenanthroline as co‐ligand has been synthesized and characterized. It is a mononuclear structure, in which enoxacin acts as a bidentate ligand bound to the metal through the ketone oxygen and a carboxylate oxygen atom. The complex exhibited good binding propensity to human and bovine serum albumin proteins having relatively high binding constants (6.40×10⁴ and 7.12×10⁴, respectively). The investigation of the interaction of the complex with calf‐thymus (CT) DNA has been performed with UV and circular dichroism (CD) spectroscopies, indicating that they bind to CT DNA probably by the intercalative binding mode. The binding constant (K_b) of the complex with CT DNA calculated with UV is 2.03×10⁵, which is higher than that of free enoxacin drug (2.09×10⁴) and even higher than that of typical intercalation indicator (1.23×10⁵) of ethidium bromide (EB). Fluorescence competitive studies with EB have revealed that the complex exhibited the ability to displace the DNA‐bound EB using the intercalative binding site. In addition, the antimicrobial activity showed that the complex exhibited a little bit good inhibition (MIC=1.843 (g·mL^?1) against B. subtilis than free HEn.     

Effects of the ancillary ligands of polypyridyl cobalt(II) complexes on pH-induced spectral properties and DNA binding properties

Abstract  

Two new Co(II) complexes [Co(ipH)₂(bdipH)]²⁺ and [Co(8-HQ)₂(bdipH)] (ipH = imidazo[4,5-f][1,10]phenanthroline, bdipH = 2-(benzo[d][1,3]dioxol-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline, 8-HQ = 8-hydroxyquinoline) were synthesized and characterized in detail by elemental analysis, IR, and UV–Vis spectroscopic techniques. The effects of pH on the UV–Vis absorption and emission spectra of the complex were studied. The interaction of the two complexes with calf thymus DNA was explored by using viscosity measurements, electronic absorption titration, competitive binding experiments, and cyclic voltammetry. The experimental results show that complex [Co(ipH)₂(bdipH)]²⁺ exhibits pH-sensitive emission, the two complexes can bind to DNA in an intercalation mode, and the DNA binding affinity of complex [Co(ipH)₂(bdipH)]²⁺ (K _b = 2.11 × 10⁵ M⁻¹) is greater than that of complex [Co(8-HQ)₂(bdipH)] (K _b = 1.76 × 10⁵ M⁻¹). The results show that the size and shape of the ancillary ligand have significant effects on the binding affinity of DNA and complexes.     

Novel water soluble bis(μ‐chloro) bridged Cu(II) binuclear and mononuclear complexes: Synthesis,characterization and biological evaluation

A water soluble chloro bridged binuclear copper(II) complex (3) and mononuclear complex (4) have been synthesized from chloro substituted 2‐oxo‐1,2‐dihydroquinolin‐3‐yl‐methylene‐2 hydroxybenzohydrazide 1 and 2 and CuCl₂·2H₂O. The structures of the complexes have been determined by single crystal X‐ray diffraction. The binding interactions of the ligands and complexes with CT‐DNA and protein have been evaluated by absorption and emission spectroscopic method. CT‐DNA and ethidium bromide (EB) competitive studies revealed that the compounds could interact with CT‐DNA through intercalation binding mode. Interactions of the compounds with BSA were also studied by UV−visible, fluorescence and synchronous fluorescence spectroscopic methods which showed that the compounds had a strong binding affinity with BSA through static quenching process. The cytotoxic effect of the compounds examined on cancer cell lines, such as A549 (lung cancer) and MCF7 (breast cancer) cell lines showed that all four compounds exhibited substantial cytotoxic activity.     

DNA/BSA binding interactions and VHPO mimicking potential of vanadium(IV) complexes: Synthesis,structural characterization and DFT studies

Vanadium(IV) Schiff base complexes (VOL¹‐VOL³) were synthesized and characterized by elemental analysis, various spectral methods and single crystal XRD studies. Structural analysis of VOL² reveals that the central vanadium ion in the complex is six coordinate with distorted octahedral geometry. Density functional theory (DFT) and time dependent (TD‐DFT) studies were used to understand the electronic transitions observed in the complexes in UV–Vis spectra. The electrochemical behavior of the complexes was investigated in acetonitrile medium exhibit quasi‐reversible one electron transfer. The DNA and BSA protein binding interaction of vanadium complexes has been explored by UV–Vis and fluorescence spectral methods and viscosity measurements reveal that the complexes interact with CT‐DNA through intercalation mode and follows the order VOL¹ < VOL³ < VOL². The complexes exhibit binding interactions with BSA protein. The complexes act as chemical nuclease and cleave DNA in the presence of H₂O₂. The 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay was used to evaluate the radical scavenging activity demonstrate the antioxidant property of the complexes. The antimicrobial activity was screened for several microorganisms, Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli. The mimicking of vanadium haloperoxidase was investigated by the bromination of the organic substrate phenol red by vanadium complexes in the presence of bromide and H₂O₂.     

Preparation,characterization and biological evaluation of two chiral binuclear copper(II) complexes

Two chiral Cu(II) complexes of [Cu₂(R‐L)₂](PF₆)₂·2C₂H₅OH ( 1 ) and [Cu₂(S‐L)₂](PF₆)₂·2C₂H₅OH ( 2 ) (HL = 2‐(Bis(quinolin‐2‐ylmethyl)amino)‐1‐propanol) were designed and synthesized to serve as chemical nucleases and anticancer drugs. X‐ray crystallography revealed that two complexes contain chiral binuclear cations and PF₆^? anions. The interaction of two complexes with CT‐DNA was researched via various spectroscopic techniques and viscosity measurement, indicating that the complexes were bound to CT‐DNA by a classical intercalation binding mode. In addition, the two complexes exhibited remarkable DNA cleavage activity with an optimal dosage of 10 μM in the absence of any exogenous oxidant agent. Both of the complexes showed excellent in vitro cytotoxicity on A549 cell lines with IC₅₀ values in the low micromolar range. Moreover, complex 2 could damage DNA of A549 cells into fragmentation and then induced cell apoptosis in a dose‐dependent manner, which was demonstrated by comet assay and Hoechst 33342 staining experiment. Further research showed that complex 2 could also induce G₂ and S phase cell cycle arrest.     

Experimental and Theoretical Studies on DNA‐Binding and Spectral Properties of ‘Light Switch’ Complexes [Ru(L)2(ppn)]2+ (L=2,2′‐Bipyridine and 1,10‐Phenanthroline; ppn=Pteridino[6,7‐f] [1,10]phenanthroline‐11,13‐diamine)

The ligand pteridino[6,7‐f] [1,10]phenanthroline‐11,13‐diamine (ppn) and its Ru^II complexes [Ru(bpy)₂(ppn)]²⁺ ( 1 ; bpy=2,2′‐bipyridine) and [Ru(phen)₂(ppn)]²⁺ ( 2 ; phen=1,10‐phenanthroline) were synthesized and characterized by elemental analysis, electrospray MS, ¹H‐NMR, and cyclic voltammetry. The DNA‐binding behaviors of 1 and 2 were studied by spectroscopic and viscosity measurements. The results indicate that both complexes strongly bind to calf‐thymus DNA in an intercalative mode, with DNA‐binding constants K_b of (1.7±0.4)?10⁶ M ^?1 and (2.6±0.2)?10⁶ M ^?1, respectively. The complexes 1 and 2 exhibit excellent DNA‐‘light switch’ performances, i.e., they do not (or extremely weakly) show luminescence in aqueous solution at room temperature but are strongly luminescent in the presence of DNA. In particular, the experimental results suggest that the ancillary ligands bpy and phen not only have a significant effect on the DNA‐binding affinities of 1 and 2 but also have a certain effect on their spectral properties. [Ru(phen)₂(ppn)]²⁺( 2 ) might be developed into a very prospective DNA‐‘light switch’ complex. To explain the DNA‐binding and spectral properties of 1 and 2 , theoretical calculations were also carried out applying the DFT/TDDFT method.     

Synthesis, Characterization, DNA-binding Properties and DNA Cleavage of a New Ternary Copper(Ⅱ) Complex with Mixed-ligands of Tridentate Schiff Base and 1,10-Phenanthroline

A new copper(II) complex, [Cu(naph‐leu)phen]CH₃OH·0.5H₂O, in which naph‐leu is the tridentate Schiff base ligand derived from the condensation of 2‐hydroxy‐1‐naphthaldehyde and L‐leucine, phen is phenanthroline, has been synthesized and characterized by elemental analyses, IR spectra and single crystal X‐ray diffraction. The DNA‐binding properties of this complex have been investigated by absorption spectra, fluorescence spectra and circular dichroism (CD) spectra, as well as viscosity measurement. Results show that this copper(II) complex binds to calf thymus DNA (CT‐DNA) in an intercalative mode and its intrinsic binding constant K_b is 4.87×10³ L·mol^?1. Furthermore, the DNA cleavage activity of this copper(II) complex has also been investigated by submarine gel electrophoresis. Interestingly, it was found that this complex can cleave the supercoiled plasmid pBR322 DNA to both nicked and linear forms.     

Synthesis and characterization of water‐soluble copper(II), cobalt(II) and zinc(II) complexes derived from 8‐hydroxyquinoline‐5‐sulphonic acid: DNA binding and cleavage studies

Three water‐soluble complexes, [Cu₂L₂Cl₂] ( 1 ), [CoL₂(im)₂] ( 2 ) and [ZnLClH₂O] ( 3 ) (HL = 8‐hydroxyquinoline‐5‐sulphonic acid; im = N ‐methylimidazole), were prepared and characterized using various spectral techniques. The DNA binding behaviour of complexes 1 – 3 was studied using UV–visible and circular dichroism (CD) spectra and cyclic voltammetry. All three complexes exhibit hypochromism but complexes 1 and 3 alone give a red shift of 4 nm with a significant binding constant of K _b = 2.1 × 10⁴ and 1.0 × 10⁴ M⁻¹, respectively, but complex 2 shows no red shift with lower K _b of 4.1 × 10³ M⁻¹. The voltammetric E _1/2 of complex 1 on interaction with herring sperm DNA shifts to a more positive potential, as expected, than complex 2 due to higher DNA affinity. Additionally, analysis of electrochemical data yields a value of K ₊/K ₂₊ greater than one suggesting that complex 1 binds to DNA through intercalation in the M(I) state. Evidently in CD spectral analysis, complex 1 exhibits a decrease in molar ellipticity with a red shift of 10 nm and a significant decrease in intensity compared to complexes 2 and 3 . This clearly indicates that complex 1 induces the B → A transition to a greater extent than 2 and 3 . Oxidative cleavage using circular plasmid pUC18 DNA with complex 1 was investigated using gel electrophoresis. Interestingly, complex 1 displays a strong DNA binding affinity and is efficient in cleaving DNA in the presence of H₂O₂ at pH = 8.0 at 37 °C.     

Methyl substituent effect on one‐dimensional copper(II) coordination polymers containing biologically active ligands: Synthesis,characterization, DNA interactions and cytotoxicities

Three novel water‐soluble copper(II) complexes – {[Cu(phen)(trp)]ClO₄·3H₂O}_n ( 1 ), {[Cu(4‐mphen)(trp)]ClO₄·3H₂O}_n ( 2 ) and [[Cu(dmphen)(trp)(MeOH)][Cu(dmphen)(trp)(NO₃)]]NO₃ ( 3 ) (phen: 1,10‐phenanthroline; 4‐mphen: 4‐methyl‐1,10‐phenanthroline; dmphen: 4,7‐dimethyl‐1,10‐phenanthroline; trp: l ‐tryptophan) – have been synthesized and characterized using various techniques. Complexes 1 and 2 are isostructural, and exist as one‐dimensional coordination polymers. Complex 3 consists of two discrete copper(II) complexes containing [Cu(trp)(dmphen)(MeOH)]⁺, [Cu(trp)(dmphen)(NO₃)] and one nitrate anion. The binding interaction of the complexes with calf thymus DNA (CT‐DNA) was investigated using thermal denaturation, electronic absorption and emission spectroscopic methods, revealing that the complexes could interact with CT‐DNA via a moderate intercalation mode. The binding activity of the complexes to CT‐DNA follows the order: 3  >  2 > 1 . The pUC19 DNA cleavage activity of the complexes was investigated in the absence and presence of external agents using the agarose gel electrophoresis method. Especially, in the presence of H₂O₂ as an activator, the pUC19 DNA cleavage abilities of the complexes are clearly enhanced at low concentration. Addition of hydroxyl radical scavenger dimethylsulfoxide shows a marked inhibition of the pUC19 DNA cleavage activity of the complexes. In vitro cytotoxic effect of the complexes was examined on human tumor cell lines (Caco‐2, A549 and MCF‐7) and healthy cells (BEAS‐2B). The potent cytotoxic effect of complex 3 , with IC₅₀ values of 1.04, 1.16 and 1.72 μM, respectively, is greater relative to clinically used cisplatin (IC₅₀ = 22.70, 31.1 and 22.2 μM) against the Caco‐2, A549 and MCF‐7 cell lines.     

Interactions of Dissolved dsDNA with Intercalating Drug by Anodic Voltammetry and Spectroscopy. Influence of pH

The interactions of C‐1305 (5‐dimethylaminopropylamino‐8‐hydroxy‐6H‐v‐triazolo[4,5,1‐de]acridin‐6‐one) with DNA were studied using differential pulse voltammetry and UV‐vis spectroscopy. C‐1305 interacts with dsDNA in two ways: by intercalation and by binding to the minor‐groove. For the intercalation at physiological pH (7.4) the values of the binding constant, K₁, and the binding‐site size, n₁, equal 3.36×10⁵ M^?1 and 2.5, respectively. For the weak interactions the K₂ and n₂ parameters equal 0.18×10⁵ M^?1 and 4. In the presence of excess NaCl the weak interactions do not vanish, therefore they are assigned to the minor groove binding. Substantial and complex is the influence of pH.     

4-氯-2-(1H-咪唑并[4,5-f][1,10]菲咯啉)苯酚铜(Ⅱ)配合物的晶体结构及其与DNA的相互作用

利用菲咯啉酮衍生物4-氯-2-(1H-咪唑并[4,5-f][1,10]菲咯啉)苯酚(HL)设计合成了一种新的单核铜配合物[Cu (L)(5-Cl-sal)(DMF)]ClO₄·DMF (5-Cl-Hsal=5-氯-水杨醛),用元素分析和X射线单晶衍射等手段对配合物进行了表征。该配合物晶体属三斜晶系,P1空间群。用紫外吸收光谱、荧光光谱和凝胶电泳等方法研究了配合物与DNA的相互作用。结果表明,配合物以插入方式与CT-DNA结合,结合常数为1.02×10³ L·mol^-1。同时配合物也能较大程度淬灭EB-DNA复合物的荧光,表观键合常数为4.37×10⁵ L·mol^-1,略小于经典键合常数10⁷ L·mol^-1。淬灭机理为动态淬灭。凝胶电泳实验研究表明配合物在H₂O₂存在下可将pBR322质粒DNA切割为开环缺口型DNA和线型DNA,配合物浓度越大,切割效果越好。机理研究显示,配合物切割DNA的反应是由羟基自由基(·OH)和单线态氧(¹O₂)作为活性物种的氧化切割过程。     

Synthesis,crystal structures and DNA/human serum albumin binding of ternary Cu(II) complexes containing amino acids and 6‐(pyrazin‐2‐yl)‐1,3,5‐triazine‐2,4‐diamino

Two water‐soluble 6‐(pyrazin‐2‐yl)‐1,3,5‐triazine‐2,4‐diamino (pzta)‐based Cu(II) complexes, namely [Cu(l ‐Val)(pzta)(H₂O)]ClO₄ ( 1 ) and [Cu(l ‐Thr)(pzta)(H₂O)]ClO₄ ( 2 ) (l ‐Val: l ‐valinate; l ‐Thr: l ‐threoninate), were synthesized and characterized using elemental analyses, molar conductance measurements, spectroscopic methods and single‐crystal X‐ray diffraction. The results indicated that the molecular structures of the complexes are five‐coordinated and show a distorted square‐pyramidal geometry, in which the central copper ions are coordinated to N,N atoms of pzta and N,O atoms of amino acids. The interactions of the complexes with DNA were investigated using electronic absorption, competitive fluorescence titration, circular dichroism and viscosity measurements. These studies confirmed that the complexes bind to DNA through a groove binding mode with certain affinities (K_b = 4.71 × 10³ and 1.98 × 10³ M^?1 for 1 and 2 , respectively). The human serum albumin (HSA) binding properties of the complexes were also evaluated using fluorescence and synchronous fluorescence spectroscopies, indicating that the complexes could quench the intrinsic fluorescence of HSA in a static quenching process. The relevant thermodynamic parameters revealed the involvement of van der Waals forces and hydrogen bonds in the formation of complex–HSA systems. Finally, molecular docking technology was also used to further verify the interactions of the complexes with DNA/HSA.     

Two Lanthanide(III) Complexes based on the Schiff Base N,N′‐Bis(salicylidene)‐1,5‐diamino‐3‐oxapentane: Synthesis,Characterization, DNA‐binding Properties,and Antioxidation

The Schiff base N,N′‐bis(salicylidene)‐1,5‐diamino‐3‐oxapentane (H₂L) and its lanthanide(III) complexes, PrL(NO₃)(DMF)(H₂O) ( 1 ) and Ho₂L₂(NO₃)₂ · 2H₂O ( 2 ), were synthesized and characterized by physicochemical and spectroscopic methods. Single crystal X‐ray structure analysis revealed that complex 1 is a discrete mononuclear species. The Pr^III ion is nine‐coordinate, forming a distorted capped square antiprismatic arrangement. Complex 2 is a centrosymmetric dinuclear neutral entity in which the Ho^III ion is eight‐coordinate with distorted square antiprismatic arrangement. The DNA‐binding properties of H₂L and its Ln^III complexes were investigated by spectrophotometric methods and viscosity measurements. The results suggest that the ligand H₂L and its Ln^III complexes both connect to DNA in a groove binding mode; the complexes bind more strongly to DNA than the ligand. Moreover, the antioxidant activities of the Ln^III complexes were in vitro determined by superoxide and hydroxyl radical scavenging methods, which indicate that complexes 1 and 2 have OH ^· and O₂^{– ·} radical scavenging activity.     

Dose‐, time‐and lipophilicity‐dependent silver(I)–N‐heterocyclic carbene complexes: Synthesis,characterization and interaction with plasmid and Aedes albopictus DNA

Four new Ag(I)–N‐heterocyclic carbene (NHC) complexes ( 5 – 8 ) bearing symmetrically substituted NHC ligands have been synthesized starting from the corresponding benzimidazolium bromide salts which are accessible in a single step from N ‐substituted benzimidazoles (N ‐alkyl and N ‐aryl) and subsequently reacted with the basic metal source Ag₂O in acetonitrile–methanol. These compounds were characterized using elemental analyses, ¹H NMR, ¹³C NMR, Fourier transform infrared and UV–visible spectroscopic techniques, and molar conductivity. Single‐crystal structural studies for complex 5 show that the Ag(I) centre has a perfectly linear C–Ag–C coordination, with quasi‐parallel pairs of aromatic benzimidazole planes. All the complexes interact with Aedes albopictus DNA via intercalation mode by a large hypochromicity of 22 and 27% and smaller hypochromicity of 16 and 19%. Furthermore, all complexes exhibit efficient DNA cleavage activity via a non‐oxidative mechanistic pathway. The DNase activities of the test compounds revealed a time‐ and concentration‐dependent activity pattern. The Ag(I)–NHC complexes showed considerably higher DNA cleavage activity compared to their respective benzimidazolium salts at a lower concentration. The DNA cleavage of these complexes changed from a moderate effect to a good one, corresponding to the increasing lipophilicity order of the complexes as 5  <  6  <  7  <  8 (1.02, 1.05, 1.78 and 2.06 for 5 – 8 , respectively). This order is further corroborated with the DNA binding study, but with the exception of complex 5 , which shows a better binding ability for DNA (K _b = 3.367 × 10⁶) than complexes 6 – 8 (6.982 × 10⁵, 8.376 × 10⁵ and 1.223 × 10⁶, respectively).     

The Charge Transfer Complex between 2, 3-diamino-5-bromopyridine and Chloranilic acid: Preparation,Spectroscopic Characterization,DNA binding,and DFT/PCM analysis

A charge transfer hydrogen bonded complex was prepared and experimentally explored in an acetonitrile (ACN) medium between the proton acceptor (electron donor) 2, 3-Diamino-5-bromopyridine and the proton donor (electron acceptor) chloranilic acid. The stoichiometry of the charge transfer complex is 1:1. The Benesi-Hildebrand equation is used to calculate the molar absorptivity (ε_CT), association constant (K_CT) and other spectroscopic physical characteristics. The solid compound was synthesized and studied using several spectroscopic methods. The presence of charge and proton transfers in the resultant complex was supported by ¹H NMR, FT-IR and SEM-EDX investigations. The complex DNA binding ability was investigated using electron absorption spectroscopy, and the CT complex binding mechanism is intercalative. The intrinsic binding constant (K_b) value is 5.2 × 10⁶M?1. The good binding affinity of the CT complex makes it potentially suitable for usage as a pharmaceutical in the future. Molecular docking calculations have been performed between CT complex and DNA (ID = 1BNA) to study the CT-DNA interaction theoretically. To corroborate the experimental findings, calculations based on DFT were carried out in the gas and PCM analysis where the existence of charge and hydrogen transfers. Finally, good agreement between experimental and theoretical computations was observed confirming that the basis set used is appropriate for the system under examination.