DNA Interactions of the Functionalized (Mixed Polypyridine)ruthenium(II) Complex Bis(2,2′‐bipyridine‐κN1,κN1′)(methyl dipyrido[3,2‐a : 2′,3′‐c]phenazine‐11‐carboxylate‐κN4,κN5)ruthenium(2+) ([Ru(bpy)2(dppz‐11‐CO2Me)]2+)

A novel polypyridine ligand, dipyrido[3,2‐a:2′,3′‐c]phenazine‐11‐carboxylic acid methyl ester (=dppz‐11‐CO₂Me), and its ruthenium(II) complex, [Ru(bpy)₂(dppz‐11‐CO₂Me)]²⁺ ( 1 ), were synthesized and characterized. The binding properties of this complex to calf‐thymus DNA (CT‐DNA) were investigated by different spectrophotometric methods and viscosity measurements. The results suggest that the complex binds to DNA in an intercalative mode and serves as a molecular ‘light switch’ for DNA. When irradiated at 365 nm, the complex 1 promoted the photocleavage of plasmid pBR‐322 DNA.     

Synthesis and structures of photoactive rhenium carbonyl complexes derived from 2‐(pyridin‐2‐yl)‐1,3‐benzothiazole, 2‐(quinolin‐2‐yl)‐1,3‐benzothiazole and 1,10‐phenanthroline

Carbon monoxide (CO) has recently been identified as a gaseous signaling molecule that exerts various salutary effects in mammalian pathophysiology. Photoactive metal carbonyl complexes (photoCORMs) are ideal exogenous candidates for more controllable and site‐specific CO delivery compared to gaseous CO. Along this line, our group has been engaged for the past few years in developing group‐7‐based photoCORMs towards the efficient eradication of various malignant cells. Moreover, several such complexes can be tracked within cancerous cells by virtue of their luminescence. The inherent luminecscent nature of some photoCORMs and the change in emission wavelength upon CO release also provide a covenient means to track the entry of the prodrug and, in some cases, both the entry and CO release from the prodrug. In continuation of the research circumscribing the development of trackable photoCORMs and also to graft such molecules covalently to conventional delivery vehicles, we report herein the synthesis and structures of three rhenium carbonyl complexes, namely, fac‐tricarbonyl[2‐(pyridin‐2‐yl)‐1,3‐benzothiazole‐κ²N ,N ′](4‐vinylpyridine‐κN )rhenium(I) trifluoromethanesulfonate, [Re(C₇H₇N)(C₁₂H₈N₂S)(CO)₃](CF₃SO₃), ( 1 ), fac‐tricarbonyl[2‐(quinolin‐2‐yl)‐1,3‐benzothiazole‐κ²N ,N ′](4‐vinylpyridine‐κN )rhenium(I) trifluoromethanesulfonate, [Re(C₇H₇N)(C₁₆H₁₀N₂S)(CO)₃](CF₃SO₃), ( 2 ), and fac‐tricarbonyl[1,10‐phenanthroline‐κ²N ,N ′](4‐vinylpyridine‐κN )rhenium(I) trifluoromethanesulfonate, [Re(C₇H₇N)(C₁₂H₈N₂)(CO)₃](CF₃SO₃), ( 3 ). In all three complexes, the Re^I center resides in a distorted octahedral coordination environment. These complexes exhibit CO release upon exposure to low‐power UV light. The apparent CO release rates of the complexes have been measured to assess their comparative CO‐donating capacity. The three complexes are highly luminescent and this in turn provides a convenient way to track the entry of the prodrug molecules within biological targets.     

Synthesis and structures of photoactive manganese–carbonyl complexes derived from 2‐(pyridin‐2‐yl)‐1,3‐benzothiazole and 2‐(quinolin‐2‐yl)‐1,3‐benzothiazole

PhotoCORMs (photo‐active CO‐releasing molecules) have emerged as a class of CO donors where the CO release process can be triggered upon illumination with light of appropriate wavelength. We have recently reported an Mn‐based photoCORM, namely [MnBr(pbt)(CO)₃] [pbt is 2‐(pyridin‐2‐yl)‐1,3‐benzothiazole], where the CO release event can be tracked within cellular milieu by virtue of the emergence of strong blue fluorescence. In pursuit of developing more such trackable photoCORMs, we report herein the syntheses and structural characterization of two Mn^I–carbonyl complexes, namely fac‐tricarbonylchlorido[2‐(pyridin‐2‐yl)‐1,3‐benzothiazole‐κ²N ,N ′]manganese(I), [MnCl(C₁₂H₈N₂S)(CO)₃], (1), and fac‐tricarbonylchlorido[2‐(quinolin‐2‐yl)‐1,3‐benzothiazole‐κ²N ,N ′]manganese(I), [MnCl(C₁₆H₁₀N₂S)(CO)₃], (2). In both complexes, the Mn^I center resides in a distorted octahedral coordination environment. Weak intermolecular C—H…Cl contacts in complex (1) and Cl…S contacts in complex (2) consolidate their extended structures. These complexes also exhibit CO release upon exposure to low‐power broadband visible light. The apparent CO release rates for the two complexes have been measured to compare their CO donating capacity. The fluorogenic 2‐(pyridin‐2‐yl)‐1,3‐benzothiazole and 2‐(quinolin‐2‐yl)‐1,3‐benzothiazole ligands provide a convenient way to track the CO release event through the `turn‐ON' fluorescence which results upon de‐ligation of the ligands from their respective metal centers following CO photorelease.     

Mitochondria‐Targeting Oxidovanadium(IV) Complex as a Near‐IR Light Photocytotoxic Agent

Oxidovanadium(IV) complexes [VO(L¹)(phen)] ? Cl ( 1 ) and [VO(L²)(L³)] ? Cl ( 2 ), in which HL¹ is 2‐{[(benzimidazol‐2‐yl)methylimino]‐methyl}phenol (sal‐ambmz), HL² is 2‐[({1‐[(anthracen‐9‐yl)methyl]‐benzimidazol‐2‐yl}methylimino)‐methyl]phenol (sal‐an‐ambmz), phen is 1,10‐phenanthroline and L³ is dipyrido[3,2‐a:2′,3′‐c]phenazine (dppz) conjugated to a Gly‐Gly‐OMe dipeptide moiety, were prepared, characterized, and their DNA binding, photoinduced DNA‐cleavage, and photocytotoxic properties were studied. Fluorescence microscopy studies were performed by using complex 2 in HeLa and HaCaT cells. Complex 1 , structurally characterized by X‐ray crystallography, has a vanadyl group in VO₂N₄ core with the VO²⁺ moiety bonded to N,N‐donor phen and a N,N,O‐donor Schiff base. Complex 2 , having an anthracenyl fluorophore, showed fluorescence emission bands at 397, 419, and 443 nm. The complexes are redox‐active exhibiting the V(IV)/V(III) redox couple near ?0.85 V versus SCE in DMF 0.1 M tetrabutylammonium perchlorate (TBAP). Complex 2 , having a dipeptide moiety, showed specific binding towards poly(dAdT)₂ sequence. The dppz‐Gly‐Gly‐OMe complex showed significant DNA photocleavage activity in red light of 705 nm through a hydroxyl radical (^.OH) pathway. Complex 2 showed photocytotoxicity in HaCaT and HeLa cells in visible light (400–700 nm) and red light (620–700 nm), however, the complex was less toxic in the dark. Fluorescence microscopy revealed the localization of complex 2 primarily in mitochondria. Apoptosis was found to occur inside mitochondria (intrinsic pathway) caused by ROS generation.     

DNA Intercalating RuII Polypyridyl Complexes as Effective Photosensitizers in Photodynamic Therapy

Six substitutionally inert [Ru^II(bipy)₂dppz]²⁺ derivatives (bipy=2,2′‐bipyridine, dppz=dipyrido[3,2‐a:2′,3′‐c]phenazine) bearing different functional groups on the dppz ligand [NH₂ ( 1 ), OMe ( 2 ), OAc ( 3 ), OH ( 4 ), CH₂OH ( 5 ), CH₂Cl ( 6 )] were synthesized and studied as potential photosensitizers (PSs) in photodynamic therapy (PDT). As also confirmed by DFT calculations, all complexes showed promising ¹O₂ production quantum yields, well comparable with PSs available on the market. They can also efficiently intercalate into the DNA double helix, which is of high interest in view of DNA targeting. The cellular localization and uptake quantification of 1 – 6 were assessed by confocal microscopy and high‐resolution continuum source atomic absorption spectrometry. Compound 1 , and especially 2 , showed very good uptake in cervical cancer cells (HeLa) with preferential nuclear accumulation. None of the compounds studied was found to be cytotoxic in the dark on both HeLa cells and, interestingly, on noncancerous MRC‐5 cells (IC₅₀>100 μM ). However, 1 and 2 showed very promising behavior with an increment of about 150 and 42 times, respectively, in their cytotoxicities upon light illumination at 420 nm in addition to a very good human plasma stability. As anticipated, the preferential nuclear accumulation of 1 and 2 and their very high DNA binding affinity resulted in very efficient DNA photocleavage, suggesting a DNA‐based mode of phototoxic action.     

Synthesis,structure and cytotoxic activity of binuclear phenyltin(IV) complexes with N,N′‐bis(2‐hydroxybenzyl)‐1,2‐ethanebis(dithiocarbamate) ligand

Two new dinuclear phenyltin(IV) complexes derived from N,N′‐bis(2‐hydroxybenzyl)‐1,2‐ethanebis(dithiocarbamate) ligand, [2‐HOC₆H₄CH₂N(CS₂SnPh₃)CH₂]₂ ( 1 ) and [2‐HOC₆H₄CH₂N(CS₂SnClPh₂)CH₂]₂ ( 2 ) have been synthesized and characterized by elemental analysis, IR and NMR (¹H, ¹³C and ¹¹⁹Sn) spectra. The crystal structures of complexes 1 and 2 were determined by X‐ray single crystal diffraction and show that the dithiocarbamate ligand is coordinated to the tin atom in the anisobidentate manner and the tin atom is five‐coordinated. The coordination geometry of tin atom is best described as an intermediate between trigonal bipyramidal and square pyramidal with τ‐values of 0.63 and 0.53, respectively. Intermolecular hydrogen bonds (O H···S and O H···Cl) in 1 and 2 connect neighboring molecules into a one‐dimensional supramolecular chain with the centrosymmetric cyclic motifs. Complex 1 has potent in vitro cytotoxic activity against two human tumor cell lines, CoLo205 and Bcap37, while complex 2 displays weak cytotoxic activity. Copyright © 2011 John Wiley & Sons, Ltd.     

Honeycomb‐like Ordered Assembly of DNA Induced by Flexible Binuclear Ruthenium(II)–Polypyridyl Complexes

A series of binuclear ruthenium(II)–polypyridyl complexes of the type [Ru₂(N‐N)₄(BPIMBp)]⁴⁺, in which N‐N is 2,2′‐bipyridine (bpy; 1 ), 1,10‐phenanthroline (phen; 2 ), dipyrido[3,2‐d:2′,3‐f] quinoxaline (dpq; 3 ), dipyrido[3,2‐a:2′,3′‐c] phenanzine (dppz; 4 ), and 1,4′‐bis[(2‐pyridin‐2‐yl)‐1H‐imidazol‐1‐yl)methyl]‐1,1′‐biphenyl (BPIMBp) is a bridging ligand, have been synthesized and characterized. These complexes are charged (4+) cations and flexible due to the ?CH₂ group of the bridging ligand and possess terminal ligands with variable intercalative abilities. The interaction of complexes 1 – 4 with calf thymus DNA (CT‐DNA) was explored by using UV/Vis absorption spectroscopy, steady‐state emission, emission quenching with K₄[Fe(CN)₆], ethidium bromide displacement assay, Hoechst displacement assay, and viscosity measurements and revealed a groove‐binding mode for all the complexes through a spacer and an intercalative mode for complexes 3 and 4 . A decrease in the viscosity of DNA revealed bending and coiling of DNA, an initial step toward aggregation. Interestingly, a distinctive honeycomb‐like ordered assembly of the DNA–complex species was visualized by fluorescence microscopy in the solution state. The use of SEM and AFM confirmed the disordered self‐organization of the DNA–complex adduct on evaporation of the solvent. The small orderly nanosized DNA aggregates were confirmed by means of circular dichroism, dynamic light scattering (DLS), and TEM. These complexes are moderately cytotoxic against three different cell lines, namely, MCF‐7, HeLa, and HL‐60.     

π‐Stacking Modulates the Luminescence of [(dppz)Ni(Mes)Br] (dppz = dipyrido[3,2‐a:2′,3′‐c]phenazine,Mes = 2,4,6‐trimethylphenyl)

The red colour of the novel organonickel complex [(dppz)Ni(Mes)Br] (dppz = dipyrido[3,2‐a:2′,3′‐c]phenazine, Mes = 2,4,6‐trimethylphenyl) originates from long‐wavelength MLCT/L′LCT charge transfer bands. However, luminescence in dilute solution comes presumably from the ³π‐π* (phenazine) excited state. The red‐shifted emission exhibited in concentrated solutions is assigned to dimers. In the solid state emission is quenched. The crystal structure reveals two different types of π‐π stacking along the crystallographic a axis.     

Structure of the Complex of [Ru(tpm)(dppz)py]2+ with a B‐DNA Oligonucleotide—A Single‐Substituent Binding Switch for a Metallo‐Intercalator

We report the synthesis of three new complexes related to the achiral [Ru(tpm)(dppz)py]²⁺ cation (tpm=tripyridazole methane, dppz=dipyrido[3,2‐a:2′,3′‐c]phenazine, py=pyridine) that contain an additional single functional group on the monodentate ancillary pyridyl ligand. Computational calculations indicate that the coordinated pyridyl rings are in a fixed orientation parallel to the dppz axis, and that the electrostatic properties of the complexes are very similar. DNA binding studies on the new complexes reveal that the nature and positioning of the functional group has a profound effect on the binding mode and affinity of these complexes. To explore the molecular and structural basis of these effects, circular dichroism and NMR studies on [Ru(tpm)(dppz)py]Cl₂ with the octanucleotides d(AGAGCTCT)₂ and d(CGAGCTCG)₂, were carried out. These studies demonstrate that the dppz ligand intercalates into the G²–A³ step, with {Ru(tpm)py} in the minor groove. They also reveal that the complex intercalates into the binding site in two possible orientations with the pyridyl ligand of the major conformer making close contact with terminal base pairs. We conclude that substitution at the 2‐ or 3‐position of the pyridine ring has little effect on binding, but that substitution at the 4‐position drastically disrupts intercalative binding, particularly with a 4‐amino substituent, because of steric and electronic interactions with the DNA. These results indicate that complexes derived from these systems have the potential to function as sequence‐specific light‐switch systems.     

Structural studies and antileishmanial activity of 2‐acetylpyridine and 2‐benzoylpyridine nitroimidazole‐derived hydrazones

Three imidazole hydrazone compounds, namely 2‐(4‐nitro‐1H‐imidazol‐1‐yl)‐N′‐[1‐(pyridin‐2‐yl)ethylidene]acetohydrazide, C₁₂H₁₂N₆O₃, ( 1 ), 2‐(2‐nitro‐1H‐imidazol‐1‐yl)‐N′‐[1‐(pyridin‐2‐yl)ethylidene]acetohydrazide, C₁₂H₁₂N₆O₃, ( 2 ), and 2‐(2‐nitro‐1H‐imidazol‐1‐yl)‐N′‐[(phenyl)(pyridin‐2‐yl)methylidene]acetohydrazide, C₁₇H₁₄N₆O₃, ( 3 ), were obtained and fully characterized, including their crystal structure determinations. While all the compounds proved not to be cytotoxic to J774.A1 macrophage cells, ( 1 ) and ( 3 ) exhibited activity against Leishmania chagasi, whereas ( 2 ) was revealed to be inactive. Since both ( 1 ) and ( 3 ) exhibited antileishmanial effects, while ( 2 ) was devoid of activity, the presence of the acetyl or benzoyl groups was possibly not a determining factor in the observed antiprotozoal activity. In contrast, since ( 1 ) and ( 3 ) are 4‐nitroimidazole derivatives and ( 2 ) is a 2‐nitroimidazole‐derived compound, the presence of the 4‐nitro group probably favours antileishmanial activity over the 2‐nitro group. The results suggested that further investigations on compounds ( 1 ) and ( 3 ) as bioreducible antileishmanial prodrug candidates are called for.     

Hydrogen‐bonding patterns in enaminones: (2Z)‐1‐(4‐bromophenyl)‐2‐(pyrrolidin‐2‐ylidene)ethanone and its piperidin‐2‐ylidene and azepan‐2‐ylidene analogues

The title compounds, namely (2Z)‐1‐(4‐bromophenyl)‐2‐(pyrrolidin‐2‐ylidene)ethanone, C₁₂H₁₂BrNO, (I), (2Z)‐1‐(4‐bromophenyl)‐2‐(piperidin‐2‐ylidene)ethanone, C₁₃H₁₄BrNO, (II), and (2Z)‐2‐(azepan‐2‐ylidene)‐1‐(4‐bromophenyl)ethanone, C₁₄H₁₆BrNO, (III), are characterized by bifurcated intra‐ and intermolecular hydrogen bonding between the secondary amine and carbonyl groups. The former establishes a six‐membered hydrogen‐bonded ring, while the latter leads to the formation of centrosymmetric dimers. Weak C—H...Br interactions link the individual molecules into chains that run along the [011], [101] and [101] directions in (I)–(III), respectively. Additional weak Br...O, C—H...π and C—H...O interactions further stabilize the crystal structures.     

Tuning the Excited State of Water‐Soluble IrIII‐Based DNA Intercalators that are Isostructural with [RuII(NN)2(dppz)] Light‐Switch Complexes

The synthesis of two new Ir^III complexes which are effectively isostructural with well‐established [Ru(NN)₂(dppz)]²⁺ systems is reported (dppz=dipyridophenazine; NN=2,2′‐bipyridyl, or 1,10‐phenanthroline). One of these Ir^III complexes is tricationic and has a conventional N₆ coordination sphere. The second dicationic complex has a N₅C coordination sphere, incorporating a cyclometalated analogue of the dppz ligand. Both complexes show good water solubility. Experimental and computational studies show that the photoexcited states of the two complexes are very different from each other and also differ from their Ru^II analogues. Both of the complexes bind to duplex DNA with affinities that are two orders of magnitude higher than previously reported Ir(dppz)‐based systems and are comparable with Ru^II(dppz) analogues.     

Synthesis and Characterization of a Trisheteroleptic RuII‐Based Molecular Switch

The synthesis of a trisheteroleptic ruthenium complex [Ru(tb)(dppz)(tmbiH₂)][PF₆]₂ (tb=4,4′‐di‐tert‐butyl‐2,2′‐bipyridine, dppz=dipyrido[3,2‐a:2′,3′‐c]phenazin, tmbiH₂=5,6,5′,6′‐tetramethyl‐2,2′‐bibenzimidazole) is described. In addition, the structural characterisation by means of 1D, 2D ¹H NMR spectroscopy, and mass spectrometry, along with determination of the solid‐state structure of the important precursor Ru(tb)(dppz)Cl₂, supports the proposed octahedral coordination geometry. The capability of tmbiH₂ to form hydrogen bonds is corroborated by the solid‐state structure. The photochemical characteristics of this complex can be described as a combination of the “light switch” effects, which are either attributed to the dppz or to the tmbiH₂ ligand. To illustrate the molecule’s double switchable features, steady‐state absorption and emission measurements were performed, which include the determination of the quantum yield and the pK_a values of the acidic protons of the tmbiH₂ ligand. Notably, the emission lifetimes are sensitive to the solvents used. This phenomenon is due to a proton‐coupled deactivation of the excited metal‐to‐ligand charge transfer (MLCT) state of the complex.     

Synthesis and Crystal Structure of Di-n-butyltin（Ⅳ） Complex with 2-Oxo-propionic Acid （4-Pyridinecarbonyl） Hydrazone

The novel complex di‐n‐butyltin(IV) 2‐oxo‐propionic acid (4‐pyridinecarbonyl) hydrazone, (n‐C₄H₉)₂Sn‐[O₂CC(CH₃)=N‐N=C(‐O)C₅N‐4] (H₂O) has been synthesized and its structure has been determined by X‐ray diffraction analysis. The complex crystallizes in orthorhombic system with space group Pca2₁. Crystal data: a=2.7540(9) nm, b=0.9676(3) nm, c= 1.5750(5) nm, V=4.197(2) nm³, D_c= 1.444 g/cm³, Z=8. μ= 1.241 mm^?1. F(000)= 1856, R₁=0.0462 and wR₂=0.1001. In the crystals of the title complex, the tin atom is in six‐coordination with a distorted octahedral geometry, three oxygen atoms [O(1), O(3) and O(4)] and one nitrogen atom N(1) forming the equatorial plane and C(10)‐Sn(1)‐C(14) being the axis. Two molecules form a dimer with weak interactions of Sn‐O bonding and hydrogen bonds.     

N,N, N′, N′‐Tetrakis(diphenylphosphanyl)‐1, 3‐diaminobenzene as a Bis‐chelate Ligand in [1, 3‐{cis‐Mo(CO)4(PPh2)2N}2C6H4]

1, 3‐Diaminobenzene reacts readily with PPh₂Cl to give N, N, N′, N′‐tetrakis(diphenylphosphanyl)‐1, 3‐diaminobenzene ( 1 ) in excellent yield. The dinuclear complex [1, 3‐{cis‐Mo(CO)₄(PPh₂)₂N}₂C₆H₄] ( 2 ) is obtained in high yield from 1 and cis‐[Mo(CO)₄(NCEt)₂]. Compounds 1 and 2 were characterized by NMR spectroscopy (¹H, ¹³C, ³¹P) and by crystal structure determination. The latter shows the formation of a bis‐chelate complex with Mo‐P‐N‐P four‐membered rings.     

rac‐1‐[(2‐Methoxyethyl)sulfanyl]‐2‐[(2‐methoxyethyl)sulfinyl]benzene and its PdCl2 complex

As an extension of recent findings on the recovery of palladium with dithioether extractants, single crystals of the chelating vicinal thioether sulfoxide ligand rac‐1‐[(2‐methoxyethyl)sulfanyl]‐2‐[(2‐methoxyethyl)sulfinyl]benzene, C₁₂H₁₈O₃S₂, (I), and its square‐planar dichloridopalladium complex, rac‐dichlorido{1‐[(2‐methoxyethyl)sulfanyl]‐2‐[(2‐methoxyethyl)sulfinyl]benzene‐κ²S,S′}palladium(II), [PdCl₂(C₁₂H₁₈O₃S₂)], (II), have been synthesized and their structures analysed. The molecular structure of (II) is the first ever characterized involving a dihalogenide–Pd^II complex in which the palladium is bonded to both a thioether and a sulfoxide functional group. The structural and stereochemical characteristics of the ligand are compared with those of the analogous dithioether compound [Traeger et al. (2012). Eur. J. Inorg. Chem. pp. 2341–2352]. The sulfinyl O atom suppresses the electron‐pushing and mesomeric effect of the S—C...;C—S unit in ligand (I), resulting in bond lengths significantly different than in the dithioether reference compound. In contrast, in complex (II), those bond lengths are nearly the same as in the analogous dithioether complex. As observed previously, there is an interaction between the central Pd^II atom and the O atom that is situated above the plane.     

(Benzyl isocyanide)gold(I) pyrimidine‐2‐thiolate complex: Synthesis and biological activity

The reaction of [(Me₂S)AuCl] with an equimolar amount of benzyl isocyanide (PhCH₂NC) ligand led to the formation of complex [(PhCH₂NC)AuCl] ( 1 ). The solid‐state structure of 1 was determined using the X‐ray diffraction method. Through a salt metathesis reaction, the chloride ligand in 1 was replaced by pyrimidine‐2‐thiolate (SpyN^?) to afford the complex [(PhCH₂NC)Au(η¹‐S‐Spy)] ( 2 ), which was characterized spectroscopically. The cytotoxic activities of 1 and 2 were evaluated against three human cancer cell lines: ovarian carcinoma (SKOV3), lung carcinoma (A549) and breast carcinoma (MCF‐7). Complex 2 showed higher cytotoxicity than cisplatin against SKOV3 and MCF‐7 cancer cell lines. It showed a strong anti‐proliferative activity with IC₅₀ of 7.80, 6.26 and 6.14 μM, compared with that measured for cisplatin which was 7.62, 12.36 and 11.47 μM, against A549, SKOV3 and MCF‐7 cell lines, respectively. The induction of cellular apoptosis by 2 was also studied on MCF‐7 cell line. Our results indicated that 2 could induce apoptosis in cancerous cells in a dose‐dependent manner.     

Synthesis and Characterization of New Copper(I) Complexes Containing Thione Derivatives of 1, 2, 4‐Triazine. Crystal Structure of [Cu(PPh3)2(ATTO)]NO3 (ATTO = 4‐amino‐1, 2, 4‐triazin‐3(2H)‐thione‐5‐one)

The reaction of 4‐amino‐1, 2, 4‐triazin‐3(2H)‐thione‐5‐one (ATTO, 1 ) with [Cu(PPh₃)₂]NO₃ in ethanol led to the complex [Cu(PPh₃)₂(ATTO)]NO₃ ( 2 ). 2 was characterized by elemental analyses, IR, ¹H NMR and Raman spectroscopy. A single‐crystal X‐ray diffraction of compound 2 revealed that ATTO acts as a bidentate ligand via its nitrogen and sulfur atoms. Crystal data for 2 at 20 °C: space group P2₁/n with a = 975.7(1), b = 1533.5(2), c = 2504.2(3) pm, β = 92.25(1)°, Z = 4, R₁ = 0.0632.     

A new coordination complex based on a polynitrile ligand: bis(4‐amino‐3,5‐di‐2‐pyridyl‐4H‐1,2,4‐triazole)diaquairon(II) bis(1,1,3,3‐tetracyano‐2‐methylsulfanylpropenide)

The new high‐spin iron(II) complex, [Fe(C₁₂H₁₀N₆)₂(H₂O)₂](C₈H₃N₄S)₂ or [Fe(abpt)₂(H₂O)₂](tcnsme)₂ [where abpt is 4‐amino‐3,5‐di‐2‐pyridyl‐4H‐1,2,4‐triazole and tcnsme is the 1,1,3,3‐tetracyano‐2‐methylthiopropenide anion], consists of discrete [Fe(abpt)₂(H₂O)₂]²⁺ dications, where the Fe^II ion is coordinated by two N,N′‐bidentate chelating abpt ligands in the equatorial plane and two water molecules in trans positions, generating a distorted octahedral [FeN₄O₂] environment. The cationic unit is neutralized by two polynitrile tcnsme anions, in which the C—N, C—C and C—S bond lengths indicate extensive electronic delocalization. In the crystal structure, the dications and anions are linked through O—H...N and N—H...N hydrogen bonds involving the water H atoms and those of the NH₂ groups and the N atoms of the CN groups, leading to the formation of a three‐dimensional network.     

Topoisomerase I inhibitory and photocleavage activity of non‐dppz DNA ‘light switches’ based on ruthenium complexes containing nitro group

A new polypyridyl ligand containing a nitro group and two new ruthenium complexes of it were synthesized. The two complexes exhibited non‐dppz DNA ‘light switch’ effects after interaction with calf thymus DNA. Introducing both electron‐withdrawing group (─ NO₂) and electron‐donating group (─ CH₃) may be the reason that the two complexes display DNA ‘light switch’ behaviors. Furthermore, one of the complexes showed higher photocleavage activity, topoisomerase I inhibition activity and DNA affinity than the other. The present work shows that the more active complex can be employed as a non‐dppz DNA ‘light switch’, DNA photocleaver and topoisomerase I inhibitor. In addition, the two complexes have no or weak cytotoxic activities against Eca‐109 and A549 cells.