Electrochemical characterization and DNA-binding property of dipyridophenazine complexes of osmium (II).

Novel dipyridophenazine (DPPZ) complexes of osmium (II), [Os(L)2(DPPZ)]2+ [L = 2,2'-bipyridyl (bpy)(1), 4,4'-diamino-2,2'-bipyridyl (DA-bpy)(2), 4,4'-dimethyl-2,2'-bipyridyl(DM-bpy)(3), and 4,4'-dicarboxyl-2,2'-bipyridyl (DC-bpy)(4)] have been synthesized and characterized. The DNA-binding properties of the complexes were studied by electrochemical methods. As the results, complex 2 shows higher affinity to DNA than other osmium complexes. The binding constant, K of complex 2 to calf thymus DNA has been determined to be 2.3 x 10(7) M-1 by normal pulse voltammetry (NPV).     

Preparation of platinum(IV) complexes with dipeptide and diimine. X-ray crystal structure and 195Pt NMR spectra

We prepared platinum(IV) complexes containing dipeptide and diimine or diamine, the [PtCl(dipeptide-N,N,O)(diimine or diamine)]Cl complex, where -N,N,O means dipeptide coordinated as a tridentate chelate, dipeptide=glycylglycine (NH(2)CH(2)CON(-)CH(2)COO(-), digly, where two protons of dipeptide are detached when the dipeptide coordinates to metal ion as a tridentate chelate), glycyl-L-alanine (NH(2)CH(2)CON(-)CHCH(3)COO(-), gly-L-ala), L-alanylglycine (NH(2)CH CH(3)CON(-)CH(2)COO(-), L-alagly), or L-alanyl-L-alanine (NH(2)CHCH(3)CON(-)CHCH(3)COO(-), dil-ala), and diimine or diamine=bipyridine (bpy), ethylenediamine (en), N-methylethylenediamine (N-Me-en), or N,N'-dimethylethylenediamine (N,N'-diMe-en). In the complexes containing gly-L-ala or dil-ala, two separate peaks of the (195)Pt NMR spectra of the [PtCl(dipeptide-N,N,O)(diimine or diamine)]Cl complexes appeared in, but in the complexes containing digly or L-alagly, one peak which contained two overlapped signals appeared. One of the two complexes containing gly-L-ala and bpy, [PtCl(gly-L-ala-N,N,O)(bpy)]NO(3), crystallized and was analyzed. This complex has the monoclinic space group P2(1)2(1)2(1) with unit cell dimensions of a=9.7906(3)A, b=11.1847(2)A, c=16.6796(2)A, Z=4. The crystal data revealed that this [PtCl(gly-L-ala-N,N,O)(bpy)]NO(3) complex has the near- (Cl, CH(3)) configuration of two possible isomers. Based on elemental analysis, the other complex must have the near- (Cl, CH(3))-[PtCl(gly-L-ala-N,N,O)(bpy)]NO(3) configuration. The (195)Pt NMR chemical shifts of the near- (Cl, CH(3))-[PtCl(gly-L-ala-N,N,O)(bpy)]NO(3) complex and the far- (Cl, CH(3))-[PtCl(gly-L-ala-N,N,O)(bpy)]NO(3) complex are 0 ppm and -19 ppm, respectively (0 ppm for the Na(2)[PtCl(6)] signal). The additive property of the (195)Pt NMR chemical shift is discussed. The (195)Pt NMR chemical shifts of [PtCl(dipeptide-N,N,O)(bpy)]Cl appeared at a higher field when the H attached to the dipeptide carbon atom was replaced with a methyl group. On the other hand, the (195)Pt NMR chemicals shifts of [PtCl(dipeptide-N,N,O)(diamine)] appeared at a lower field when the H attached to the diamine nitrogen atom was replaced with a methyl group, in the order of [PtCl(digly-N,N,O)(en)]Cl, [PtCl(digly-N,N,O)(N-Me-en)]Cl, and [PtCl(digly-N,N,O)(N,N'-diMe-en)]Cl.     

Ruthenium(II) mixed-ligand complex containing 2-(4'-benzyloxy-phenyl)imidazo[4,5-f][1,10]phenanthroline: synthesis, DNA-binding and photocleavage studies

A novel polypyridyl ligand 2-(4'-benzyloxyphenyl)imidazo[4,5-f][1,10]phenanthroline (BPIP) and its complex [Ru(bpy)2(BPIP)]2+ (1) (bpy=2,2'-bipyridine) and (2) [Ru(phen)2(BPIP)]2+) (phen=1,10-phenanthroline) have been synthesized and characterized by elemental analysis, electrospray mass spectra and 1H NMR. The DNA-binding properties of the two complexes were investigated by spectroscopic and viscosity measurements. The results suggest that both complexes bind to DNA via an intercalative mode. Both complexes can enantioselectively interact with calf thymus DNA (CT-DNA) in a way. The Lambda enantiomer of complex 1 is slightly predominant for binding to CT-DNA to the Delta enantiomer. Under irradiation at 365 nm, both complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA. Inhibitors studies suggest that singlet oxygen ((1)O2) and hydroxyl radical (*OH) play a significant role in the cleavage mechanism for both complexes. Moreover, the DNA-binding and photocleavage properties of both complexes were compared with that of [Ru(bpy)2(BPIP)]2+ and [Ru(phen)2(BPIP)]2+. The experimental results indicate that methene group existence or not have a significant effect on the DNA-binding and cleavage mechanism of these complexes.     

Pt(II) complexes with N-(3-pyridyl)-2-(4-(trifluoromethyl)phenyl)diazenecarboxamide and their reactions with glutathione

The reaction between [PtCl(dmso)(en)]Cl (dmso=dimethyl sulfoxide, en=ethylenediamine) and N-(3-pyridyl)-2-(4-(trifluoromethyl)phenyl)diazenecarboxamide (L) was studied using multinuclear NMR spectroscopy. The water-soluble complexes [PtCl(en)(L-N1)](+) (1) and [Pt(en)(L-N1)(2)](2+) (2) were isolated and their reactions with glutathione (GSH) were investigated to assess the oxidation properties of coordinated L. Both species 1 and 2 oxidized GSH to GSSG, while the reduced form of L (semicarbazide, SL) remained coordinated to Pt(2+). In complex 1 the labile chloride ion was substituted by the thiol moiety of GSH, which gave rise to the release of en in excess GSH over a period of 7 days. Complexes [PtCl(dmso)(en)]Cl, 1, 2 and ligand L were tested against T24 bladder carcinoma cells. Ligand L and complexes 1 and 2 showed higher cytotoxicity than [PtCl(dmso)(en)]Cl.     

Synthesis and photophysical properties of zinc myoglobin appending an ethidium ion as a DNA intercalator

In order to elucidate the intramolecular photoinduced electron-transfer or energy-transfer mechanisms of the zinc myoglobin (ZnMb) dyad and to construct a photoreaction system within a Mb–DNA complex, we newly prepared ZnMb appending an ethidium ion (Et⁺). The steady-state fluorescence of ZnMb–Et⁺ at 600 nm and its lifetime (2.2 ns) indicate that the excited singlet state of ¹(ZnMb)* is not quenched by the Et⁺ moiety, whereas the lifetime of the excited triplet state of ³(ZnMb)*–Et⁺ was shorter (τ = 4.3 ms) than those of ZnMb and the intermolecular (ZnMb + ethidium) system. Upon photoirradiation of Et⁺, fluorescence studies indicated the intramolecular quenching reactions from the excited singlet state, ¹(Et⁺)*, to ZnMb, the process of which is likely the photoinduced energy-transfer reaction via a through-space mechanism. We also demonstrate the photophysical and spectroscopic properties of ZnMb–Et⁺ in the presence of calf thymus (CT) DNA. The changes in the absorption and fluorescence spectra of ZnMb–Et⁺ on the addition of CT-DNA up to 15 equiv were very small, indicating that there are no major changes in the heme pocket. However, we observed a longer lifetime of ³(ZnMb)*–Et⁺ in the presence of CT-DNA (τ = 5.3 ms) by single flash photolysis. This was induced by noncovalent interactions between Et⁺ and CT-DNA, followed by a conformational change of Et⁺ at the surface of ZnMb, where the donor–acceptor distance was probably elongated by CT-DNA. The synthetic manipulation at the Mb surface, by using a DNA intercalator coupled with photoinduced reaction, may provide a sensitive transient signal for DNA and valuable information to construct new Mb–DNA complex. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

DNA intercalating studies of [Ru(bpy)2dmt]2+ with two vacant nitrogen atoms by introducing copper(II) ions

A novel, yet effective method for identifying DNA-binding modes of [Ru(bpy)(2)dmt](2+) (where bpy?=?2,2'-bipyridine and dmt?=?2,3-dimethyl-1,4,8,9-tetra-aza-triphenylene) on an indium tin oxide electrode has been successfully developed by introducing Cu(2+) ion and ethylenediaminetetraacetic acid. The results from emission spectra and fluorescence microscopic images suggested that [Ru(bpy)(2)dmt](2+) not only associates with Cu(2+) ion in both the absence and presence of DNA but also shows strong affinity with DNA in the presence of Cu(2+). Evidence for the strong binding of [Ru(bpy)(2)dmt](2+) to DNA was determined from the interface studies using electrochemical methods. The present study suggests that a combination of photoluminescence measurement with electrochemical methods identifies the DNA-binding behavior of luminescent molecules with redox activities. [Ru(bpy)(2)dmt](2+) binds to DNA via an intercalative mode.     

Cytotoxicity and DNA binding studies of several platinum (II) and palladium (II) complexes of the 2,2'-bipyridine and an anion of 2-pyridinecarboxylic/2-pyrazinecarboxylic acid.

Four water soluble complexes of the type [M(bpy)(a-x)]NO3, where M is Pd(II) or Pt(II), bpy is 2,2-bipyridine, and a-x is anion of 2-pyridinecarboxylic acid or 2-pyrazinecarboxylic acid, have been found to bind calf thymus DNA, possibly through hydrogen binding. [M(bpy)(2-py)]NO3 complexes (2-py is an anion of 2-pyridinecarboxylic acid) show I.D.50 values smaller than cisplatin whereas [M(bpy)(2-pyz)]NO3 complexes (2-pyz is an anion of 2-pyrazinecarboxylic acid) show I.D.50 values larger than cisplatin against P388 cancer cells.     

An ultraviolet melting study of the stability of the DNA double helix in the NaDNA-bipyridyl-(ethylenediamine)platintum(II) complex

Complexes of NaDNA with the bipyridyl-(ethylenediamine)platintum(II) (abbreviated [(bipy)Pt(en)]2+) molecular ion have been studied in solution via ultraviolet absorption experiments at 260 nm between 50 and 90 degrees C. These measurements, performed as a function of the molar ratio of the [(bipy)Pt(en)]2+ complex to DNA base pairs, show that the stability of the DNA double helix is increased by the formation of the DNA.[(bipy)Pt(en)]2+ complex: at a molar ratio of 0.33, the temperature at which the DNA double helix separates into two single strands is increased by about 15 degrees C.     

Adduct formation between ternary Pt(II)-amino acid-aromatic diimine complexes and flavin mononucleotide and its effect on redox properties

Adduct formation of ternary Pt(II) complexes composed of an amino acid and an aromatic diimine, [Pt(A)(DA)] (A = glycinate (Gly), alaninate (Ala), valinate, or arginine (Arg); DA = 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen)), with flavin mononucleotide (FMN) and anthraquinone-2-sulfonate (AQS) were investigated by spectroscopic, X-ray diffraction, and electrochemical methods. The Pt(II) complexes formed 1:1 [Pt(A)(DA)]-FMN adducts by stacking with the aromatic moiety of FMN, and the stability constants, log K, for the systems with [Pt(A)(phen)] (A = Gly, Ala, and Arg) and [Pt(Arg)(bpy)] were determined to be 2.83(8)-3.42(6) from ¹H NMR spectra at 25 °C in D₂O (I = var.). The structure of the adduct [Pt(Ala)(phen)](AQS) (1) was determined by X-ray analysis to involve a π-π stacking interaction between coordinated phen and AQS with the distance of 3.400(7) Å and a hydrogen bond between the sulfonate moiety of AQS and the amino group of coordinated Ala. Cyclic voltammetry of the 1:1 [Pt(A)(DA)]-FMN systems in a phosphate buffer (pH 7.0) showed that the potentials, E_1/2, for the two-electron redox process of FMN shifted to higher values by 18-31 mV as compared with the value for free FMN.     

The dichotomy in the DNA-binding behaviour of ruthenium(II) complexes bearing benzoxazole and benzothiazole groups

The substituted tris(bipyridine)ruthenium(II) complexes {[Ru(bpy)(2)(4,4'-bbob)](2+) and [Ru(bpy)(2)(5,5'-bbob)](2+) [where bpy=2,2'-bipyridine and bbob=bis(benzoxazol-2-yl)-2,2'-bipyridine] have been prepared and compared to the previously studied complex [Ru(bpy)(2)(4,4'-bbtb)](2+) [where bbtb=bis(benzothiazol-2-yl)-2,2'-bipyridine]. From the UV/VIS titration studies, Delta-[Ru(bpy)(2)(4,4'-bbob)](2+) displays a stronger association than the Lambda-isomer with calf-thymus DNA (ct-DNA). For [Ru(bpy)(2)(5,5'-bbob)](2+), there appears to be minimal interaction with ct-DNA. The results of fluorescence titration studies suggest that [Ru(bpy)(2)(4,4'-bbob)](2+) gives an increase in emission intensity with increasing ct-DNA concentrations, with an enantiopreference for the Delta isomer, confirmed by membrane dialysis studies. The fluorescent intercalation displacement studies revealed that [Ru(bpy)(2)(4,4'-bbob)](2+) and [Ru(bpy)(2)(5,5'-bbob)](2+) display a preference for more open DNA structures such as bulge and hairpin sequences. While Lambda-[Ru(bpy)(2)(4,4'-bbtb)](2+) has shown the most significant affinity for all the oligonucleotides sequences screened in previous studies, it is the Delta isomer of the comparable benzoxazole ruthenium(II) complex (Delta-[Ru(bpy)(2)(4,4'-bbob)](2+)) that preferentially binds to DNA.     

Synthesis, structure, and reactivity of monofunctional platinum(II) and palladium(II) complexes containing the sterically hindered ligand 6-(methylpyridin-2-yl)acetate

Three complexes containing the novel, sterically hindered ligand 6-(methylpyridin-2-yl)acetate (PICAC) have been synthesized and characterized: [Pt(NH3)2(PICAC-N,O)]NO3 (1), [Pt(en)(PICAC-N,O)]NO3 (2), and [Pd(en)(PICAC-N,O)]NO3 (3) (en = ethane-1,2-diamine). The crystal structures of 2 and 3 have been determined. The two complexes are isostructural and exhibit a mixed [N3O] coordination. In both cases, PICAC forms a sterically crowded six-membered chelate. Signal multiplicities in 1H NMR spectra of 1-3 indicate that the N,O chelates are conformationally rigid on the NMR timescale as a result of the steric bulk of the pyridine derivative. Complex 2 undergoes facile ring opening in 0.1M NaCl solution at neutral pH, resulting in a zwitterionic species in which carboxylate oxygen has been replaced with chloride. The complex was identified by X-ray crystallography as [PtCl(en)(PICAC-N)] x H2O (4), which contains a "dangling" carboxylate group. In 4, the pyridine moiety adopts an almost perpendicular orientation relative to the platinum coordination plane. Likewise, complex 2 reacts rapidly with 5'-guanosine monophosphate (5'-GMP) to form the monofunctional adduct [Pt(en)(PICAC)(5'-GMP)] (5) (NMR, 25 degrees C, t(1/2) approximately 24 min). 2-D nuclear Overhauser enhancement spectroscopy (NOESY) and double quantum-filtered correlated spectroscopy (dqf-COSY) experiments (500 MHz) and variable temperature NMR spectroscopy confirm that adduct 5 exists as a 1:1 mixture of rotamers in solution as a result of the mutual repulsion between the cis-oriented pyridine and guanine bases. While 2 readily reacts with DNA nitrogen, its monofunctional adducts show no significant effect on the conformation of native DNA. Circular dichroism (CD) spectra recorded of platinum-modified calf-thymus DNA suggest that the structural damage produced by complex 2 does not mimic that produced by the clinical agent. Both the unusual reactivity and the inability to induce cisplatin-like DNA conformational changes are proposed to be responsible for the marginal biological activity of the new complexes.     

Intrinsically fluorescent cytotoxic cisplatin analogues as DNA marker molecules

Two square planar derivatives of Pt(en)Cl(2) with intrinsic fluorescence in aqueous solution at room temperature, with quantum yields (Phi) 0.11 and 0.10, respectively, have been synthesized and characterized as [Pt(en)(CG)Cl] (Complex 1) and [Pt(en)(CG)(2)] (Complex 2) (en = ethylenediamine, CG = cholylglycinate). Complexes 1 and 2 exchange just one ligand (chloride or cholylglycinate, respectively) when reacted with water or 5'-GMP to give the same chemical species. After reaction with DNA oligonucleotides or DNA plasmids, they show enhanced emission in the visible region, which lasts for long periods of time and makes them potentially useful DNA marker molecules. Incubation with nucleated blood cells followed by microscopic analyses revealed that they enter the cells within minutes of exposure, selectively stain the DNA, and persist after more than 48 h of exposure. Complexes 1 and 2 display cell cycle phase-independent cytotoxic activity against cisplatin-resistant CHO (Chinese hamster ovarian) tumor cells, with an early onset of their effects. Their slightly different biological effects, as compared to cisplatin, are considered to be linked to the bile acids and their vector properties and to the preferential formation of monoadducts.     

Electrochemiluminescence of dipicolinic acid (DPA) and (bpy)(2)Ru(DPA)(+) (bpy = 2,2'-bipyridine).

The spectroscopic and electrochemiluminescence (ECL) properties of dipicolinic acid (DPA), (bpy)(2)Ru(2+) (bpy = 2,2'-bipyridine) and the species formed when DPA and (bpy)(2)Ru(2+) [abbreviated to (bpy)(2)Ru(DPA)(+)] are allowed to react are reported. The UV-Vis absorption maxima for (bpy)(2)Ru(2+) and (bpy)(2)Ru(DPA)(+) are 493 and 475 nm, respectively, indicating the in situ formation of a complex between DPA and (bpy)(2)Ru(2+). DPA, (bpy)(2)Ru(2+) and (bpy)(2)Ru(DPA)(+) display ECL upon oxidation in the presence of the oxidative-reductive co-reactant tri-n-propylamine (TPrA). The ECL of (bpy)(2)Ru(DPA)(+) is at least two-fold higher than either of the parent species. An ECL spectrum of (bpy)(2)Ru(DPA)(+) displays a peak maximum 40 nm red-shifted from the photoluminescence peak maximum, suggesting that the excited state formed electrochemically is different from that formed spectroscopically.     

Synthesis, characterization and DNA-binding of novel chiral complexes delta- and lambda-[Ru(bpy)2L]2+ (L = o-mopip and p-mopip)

Novel chiral Ru(II) complexes [Ru(bpy)2L]2+ (bpy = 2,2-bipyridine; L: o-mopip = 2-(2-methoxylphenyl)imidazo[4,5-f][1,10]phenanthroline, p-mopip = 2-(4-methoxylphenyl)imidazo[4,5-f][1,10]phenanthroline) containing -OCH3 at different positions on the phenyl ring have been synthesized and characterized. The DNA-binding and DNA-photocleavage properties of the complexes were investigated. The theoretical calculations for these complexes were also carried out applying the density functional theory (DFT) method. The experimental results show that: both these two isomer complexes can bind to DNA in an intercalative mode; the DNA-binding affinity of [Ru(bpy)2(p-mopip)] 2 is greater than that of [Ru(bpy)2(o-mopip)] 1; moreover, the DNA-binding affinities of enantiomers delta-1 and delta-2 are all greater than those of lambda-1 and lambda-2, respectively. In addition, a very interesting finding is experimentally obtained, i.e. under a low [DNA]/[Ru] ratio, the emission intensities of delta-1 and lambda-1 are all weaker than those of delta-2 and lambda-2, however, upon a high [DNA]/[Ru] ratio, the emission intensities of both delta-1 and lambda-1 are stronger than those of delta-2 and lambda-2. Such a difference of the emission spectra can be interpreted by the electric effect of substituent on the intercalative ligand. The difference in DNA-binding affinities of these two isomeric complexes can also be reasonably explained by the DFT calculations.     

Synthesis of new ultrasonic-assisted palladium oxide nanoparticles: an in vitro evaluation on cytotoxicity and DNA/BSA binding properties

Abstract

Better solubility and improved toxicity of palladium complexes compared with cisplatin were major reasons for synthesis of novel Pd(II) complex, [Pd(8Q)(bpy)]NO₃ (8Q=8-hydroxyquinolinate, bpy=2,2′-bipyridine). Interaction between the [Pd(8Q)(bpy)]NO₃ complex and calf thymus DNA in aqueous solution has been investigated by circular dichroism (CD), UV-Visible absorption and fluorescence spectroscopic techniques. These experiments showed that prepared Pd(II) complex can effectively intercalate into CT-DNA and weakly bind to BSA in which the bovine serum albumin molecule was unfolded slightly. The cytotoxicity of the prepared complex has been evaluated on the MCF-7 and DU145 cell lines by MTT and TUNEL assay. The MTT results were showed that in DU145, the CC₅₀ values of [Pd(8Q)(bpy)]NO₃ and cisplatin are very close together (10.4 and 8.3?μM, respectively), unlike MCF-7. Accordingly, TUNEL assay was performed on DU145 and apoptosis was clearly obvious by 43% DNA fragmentation in the treated cell lines. So, we can suggest the [Pd(8Q)(bpy)]NO₃ as alternative drug for cisplatin in the future which has great potential in DNA denaturation and apoptosis specially on prostate cancer. PdO nanoparticles were successfully prepared without supported any surfactants via sonochemical approach. The synthesized PdONPs were characterized using UV-Vis and FTIR spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Communicated by Ramaswamy H. Sarma     

Effects of amine ligand bulk and hydrogen bonding on the rate of reaction of platinum(II) diamine complexes with key nucleotide and amino acid residues

NMR spectroscopy has been used to observe the effects of the amine ligand on the rate of reaction of platinum diamine and triamine complexes with DNA and protein residues. Whereas [Pt(dien)Cl]Cl and [Pt(dien)(D(2)O)](2+) have been known to react faster with thioether residues such as N-AcMet than with 5'-GMP, we found that [Pt(Me(4)en)(D(2)O)(2)](2+) appeared to react faster with 5'-GMP. To quantitatively assess the factors influencing the rates of reaction, rate constants at pH 4 were determined for the reactions of [Pt(en)(D(2)O)(2)](2+) [en = ethylenediamine] and [Pt(Me(4)en)(D(2)O)(2)](2+) with N-AcMet, N-AcHis, 5'-GMP, and Guo (guanosine). In each case the less bulky complex ([Pt(en)(D(2)O)(2)](2+)) reacts more quickly than does the bulkier [Pt(Me(4)en)(D(2)O)(2)](2+), as expected. Both complexes reacted faster with 5'-GMP; however, analysis of the rate constants suggests that the [Pt(en)(D(2)O)(2)](2+) complex favors reaction with 5'-GMP due to hydrogen bonding with the 5'-phosphate, whereas [Pt(Me(4)en)(D(2)O)(2)](2+) disfavors reaction with N-AcMet due to steric clashes. Bulk had relatively little effect on the rate constant with N-AcHis, suggesting that peptides or proteins that coordinate via His residues would not have their reactivity affected by bulky diamine ligands.     

DNA-Binding and Photocleavage Properties of Ru(II) Polypyridyl Complexes with DNA and Their Toxicity Studies on Eukaryotic Microorganisms

Four Ru(II) polypyridyl complexes, [Ru(bpy)₂(7-NO₂-dppz)]²⁺, [Ru(bpy)₂(7-CH₃-dppz)]²⁺, [Ru(phen)₂(7-NO₂-dppz)]²⁺, and [Ru(phen)₂(7-CH₃-dppz)]²⁺ (bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline), (7-Nitro-dppz = 7-Nitro dipyrido[3,2-a:2′-3′-c]phenazine, 7-CH₃-dppz = 7-Methyl dipyrido[3,2-a:2′-3′-c]phenazine), have been synthesized and characterized by IR, UV, elemental analysis, ¹H NMR, ¹³C-NMR, and mass spectroscopy. The DNA-binding properties of the four complexes were investigated by spectroscopic and viscosity measurements. The results suggest that all four complexes bind to DNA via an intercalative mode. Under irradiation at 365 nm, all four complexes were found to promote the photocleavage of plasmid pBR 322 DNA. Toxicological effects of the selected complexes were performed on industrially important yeasts (eukaryotic microorganisms).