四氢叶酸辅酶模型1, 2, 3-三取代咪唑啉盐的质谱裂解行为

讨论了１ ,２ ,３不对称取代咪唑啉盐各种离子的生成途径以及取代基对裂解方式的影响并分析了该类化合物的主要裂解方式。在所有实验中均有 ｍ／ｚ ＝ １２７（ Ｉ＋ ） 的离子峰和有机正离子 Ａ 峰存在,表明化合物１ 和２ 均为有机正离子和碘离子形成的盐。化合物１ 和２ 的质谱有相似的裂解方式：有机正离子发生失掉氮原子上的一个取代基而保留咪唑啉环产生 Ｄ, Ｅ, Ｆ 离子的裂解方式。更重要的是咪唑啉环有相同的裂解方式： Ｃ２ Ｎ３ 键和 Ｃ５ Ｎ１ 键同时断裂产生 Ｇ 离子碎片,以及 Ｃ２ Ｎ３ 键和 Ｃ４ Ｃ５ 键同时断裂产生 Ｈ 离子碎片。由于化合物１ 和２ 环上所连接的取代基不同而导致了其质谱裂解方式和程度的差异。化合物２ 的有机正离子 Ａ部分较稳定,质谱中表现为基峰,其 Ｅ, Ｆ 离子峰很弱;化合物１ 的有机正离子 Ａ 稳定性差,其相对丰度很小,其 Ｅ, Ｆ 离子峰较强。化合物１ｃ ,１ｄ ,１ｅ 的质谱中出现了比 Ａ 离子少三个单位的 Ｃ 离子峰,这是一种较特殊的裂解方式。     

Hydration of a Na(+)-montmorillonite studied by thermally stimulated depolarization current

Thermally stimulated depolarization current (TSDC) technique is a powerful tool for probing dipole re-orientational motions in condensed matter. In the case of cation-exchangeable aluminosilicates, it allows the assessment of the potential barrier related to the hopping mechanism of cations and, consequently, the measurement of its evolution when molecules, i.e. water, are adsorbed and interact with the cations embedded in the solid framework. Then, using suitable models based on thermodynamics, the analysis of TSDC signals obtained at various hydration states provides insights about the surface properties of the studied solid and the mechanism of adsorption at the cationic site. In this work, TSDC is used to study the first stage, i.e. when the number of adsorbed molecules is below the occurrence of the water monolayer, of water adsorption in a Na(+)-montmorillonite from Mostaganem (Algeria). It is shown that the hydration process follows two stages. Using the "chemical force" concept it can then be concluded that when the number of adsorbed water molecules per cation is lower than 2, cation-water interaction dominates the energetics of adsorption, whereas at higher water loading the water "chemical force" is also involved into water-water and/or water-clay framework interactions. The number of water molecules for the monohydrated state is found to be about 7.     

Investigation of thermally stimulated charge relaxation mechanism in SiO<Subscript>2</Subscript> filled polycarbonate nanocomposites

The thermally stimulated charge relaxation properties of polycarbonate (PC) filled with SiO₂ nanofiller were studied by means of thermally stimulated discharge current (TSDC). The nanocomposite samples were further characterized by UV–vis spectroscopy, scanning electron microscopy, energy dispersive X-ray spectra, and differential scanning calorimetry (DSC) techniques to investigate the dispersion of nanofillers in polymer matrix and glass transition temperature. All pristine and nanocomposites samples of thickness about 25 μm were prepared using solution mixing method. The suitable weight percentage of SiO₂ nanofillers has been chosen to prevent the nonuniform dispersion. TSDC measurement of PC (Pristine) and PC+ (7% SiO₂) shows the single peak, while TSDC characteristic of other nanocomposites are showing two peaks. The higher temperature TSDC peak of pristine and nanocomposites samples is originated due to the charge relaxation from shallower and deeper trapping sites, however, low temperature peak is caused by dipolar relaxation of charge carriers. Since the position of higher temperature TSDC peak is generally an analysis of glass transition temperature of polymer/polymer nanocomposites. The authors have observed that the temperature of this peak is almost same as the T _g measured by DSC with 0 to ±5% variation. This article presents the deeper understanding of charge relaxation mechanism caused by SiO₂ nanofillers in polycarbonate.     

Distributed relaxations in PVC/PEMA polymer blends as revealed by thermostimulated depolarization current

Thermally stimulated depolarization current (TSDC) was used to investigate the relaxation in amorphous polymers including poly(vinyl chloride) (PVC) and poly(ethyl methacrylate) (PEMA) and its polyblend over a temperature range that covers the -relaxation. Analysis of TSDC behavior revealed that PVC and PEMA are characterized with a broad peak located at the temperature maximum, T_m=355 and 347 K, respectively. These peaks were positioned in the vicinity of the glass-transition temperature of each polymer, which are attributed to dipole–dipole interaction. Moreover, thermal sampling technique (TS) was used to resolve the complex TSDC behavior of all samples to obtain its elementary peaks characterized by a single relaxation time. The peak parameters characterizing the TS peaks have been estimated by using the iterative method. In addition, around each relaxation, compensation phenomena have been observed.     

Temperature dependence of ion and water transport in perfluorinated ionomer membranes for fuel cells

To clarify the mechanisms of transport of ions and water molecules in perfluorosulfonated ionomer membranes for fuel cells, the temperature dependence of their transport behaviors was investigated in detail. Two types of Flemion membranes having different equivalent weight values (EW) were utilized along with Nafion 117 as the perfluorinated ionomer membranes, and H-, Li-, and Na-form samples were prepared for each membrane by immersion in 0.03 M HCl, LiCl, and NaCl aqueous solutions, respectively. The ionic conductivity, water self-diffusion coefficient (D(H)(2)(O)), and DSC were measured in the fully hydrated state as a function of temperature. The ionic conductivity of the membranes was reflected by the cation transport through the intermediary of water. Clearly, H(+) transports by the Grotthuss (hopping) mechanism, and Li(+) and Na(+) transport by the vehicle mechanism. The differences of the ion transport mechanisms were observed in the activation energies through the Arrhenius plots. The D(H)(2)(O) in the membranes exhibited a tendency similar to the ionic conductivity for the cation species and the EW value. However, no remarkable difference of D(H)(2)(O) between H- and the other cation-form membranes was observed as compared with the ionic conductivity. It indicates that water in each membrane diffuses almost in a similar way; however, H(+) transports by the Grotthuss mechanism so that conductivity of H(+) is much higher than that of the other cations. Moreover, the D(H)(2)(O) and DSC curves showed that a part of water in the membranes freezes around -20 degrees C, but the nonfreezing water remains and diffuses below that temperature. This fact suggests that completely free water (bulk water) does not exist in the membranes, and water weakly interacting with the cation species and the sulfonic acid groups in secondary and higher hydration shells freezes around -20 degrees C, while strongly binding water in primary hydration shells does not freeze. The ratio of freezing and nonfreezing water was estimated from the DSC curves. The D(H)(2)(O) in the membranes was found to be influenced by the ratio of freezing and nonfreezing water. DFT calculation of the interaction (solvation) energy between the cation species and water molecules suggested that the water content and the ratio of freezing and nonfreezing water depend strongly on the cation species penetrated into the membrane.     

四氢叶酸辅酶模型1, 2, 3-三取代咪唑啉盐的质谱裂解行为

讨论了１,２,３－不对称取代咪唑啉盐各种离子的生成途径以及取代基对裂解方式的影响并分析了该类化合物的主要裂解方式。在所有中的均ｍ／ｚ＝１２７（１＾＋）的离子峰和有机正离子Ａ峰存在,表明化合物１和２均有机正离子和碘离子形成的盐。化合物１和２的质谱有相似的裂解方式;有机正离子发生失掉氮原子上的一个取代基而保留咪唑啉环产生Ｄ,Ｅ,Ｆ离子的裂解方式。更重要的是咪唑啉环有相同的裂解方式：Ｃ＾２－Ｎ＾３键和Ｃ     

Primary and secondary dielectric relaxations in semi-crystalline and amorphous starch

The thermally stimulated depolarization current technique, TSDC, has been used to study the dielectric relaxations in cassava starch on semi-crystalline and amorphous samples. The A-type structure was observed by WAXS experiments and the variation of the crystallinity as a function of the moisture content, h, was followed on native starch. Retrogradation of the amorphous sample occurred at room temperature after 4 weeks in a closed vessel with a water activity 97.3%. In these conditions the humidity content reached a value of 28.5 wt% dry base and the crystallinity degree was comparable to that of the native starch. Three secondary relaxation modes were detected and attributed to short range orientations of polar groups and to main chain restricted motion. The influence of the moisture plasticization effect on the relaxation parameters of the local modes, was determined by decomposing the global TSDC curve in elementary Debye peaks with Arrhenius relaxation times. The main relaxation, α, which is proposed to be the dielectric manifestation of the dynamic glass transition, sweeps a wide temperature interval around room temperature as the sample dries, shifting to higher temperatures as a result of the plasticization of the polysaccharide by water molecules. The α peak deconvolution lead to the 2D relaxation time distribution and Vogel-Tammann-Fulcher parameters were obtained confirming the cooperative character of this mode. The transformed sample showed a bimodal distribution of segmental relaxation times that is interpreted as the existence of a heterogeneous amorphous phase: the mobile one which is similar to the original disordered phase present in semi-crystalline native starch and a more restricted one originated by the disruption of the crystalline lamellae during the pre-gelatinization process.     

TSDC and DSC Study of Effects of Physical Aging on Polybutylene Terephthalate (PBT)

The impact of the physical aging process on the electrical and thermal properties of semicrystalline polybutylene terephthalate (PBT) was investigated by means of thermally stimulated depolarization currents (TSDC) and differential scanning calorimetry (DSC). The TSDC technique was used to study the relaxation modes of PBT in the temperature range ?50° to + 120°C. The obtained spectra revealed two peaks located at temperature maxima of 45° and 93°C. The peak appearing at 45°C corresponds to the dielectric manifestation of the glass transition phenomenon (α-relaxation). The aim of this work is to study the effect of physical aging on this relaxation. The recording of TSDC peaks of aged PBT at different temperatures for different times revealed a reduction in their intensities and their shift towards higher temperatures when the aging becomes significant. This result can be explained by the diminution of molecular chain mobility, which is directly related to the area under the peak representing the polarization of the sample. This result was confirmed by DSC measurements, which revealed the growth and the shift of the peak, which is superimposed on the jump of the heat capacity, located around 38°C and characteristic of the glass transition, towards higher temperatures where aging becomes significant.     

Composition, structure, and luminescence of montmorillonites saturated with different aggregates of methylene blue

The distribution of various aggregates (dimers, trimers, and tetramers) of methylene blue (MB) formed in aqueous solution at various concentrations of dye has been calculated using the equilibrium aggregation constants betaq. Two montmorillonite samples with different cation exchange capacities, surface areas, and interlayer distances d001, Na-SWy, and Ca-Cheto, were saturated with methylene blue (MB) solutions with various ratios between monomers and higher aggregates of dye. The total amount of MB in the intercalated montmorillonite samples (MB-SWy and MB-Cheto) increases with increasing concentration of dye in water solutions, i.e., with increasing aggregates/monomers ratio of MB in water solution. In all intercalated montmorillonite samples with methylene blue except guest qth aggregate cations [MBqq+] low contents of Na+ (in MB-SWy) and Ca2+ (in MB-Cheto) cations were also determined. A very good positive correlation between the basal spacing d001 and the MB/montmorillonite molar ratio was revealed for saturated MB-montmorillonite samples. Structural analysis using a combination of diffraction data with molecular modeling revealed the differences in the interlayer arrangement of MB guests in MB-SWy and MB-Cheto intercalates. Also, fluorescence measurements showed the strong effect of the silicate layer charge on the spectroscopic behavior of MB guests intercalated in montmorillonite. Methylene blue exhibits a certain luminescence in MB-SWy samples with cation exchange capacity 0.80 meq g-1 and almost no luminescence in MB-Cheto samples with higher cation exchange capacity 1.50 meq g-1.     

Mass spectrometry of humic substances of different origin including those from Antarctica A comparative study

Mass spectra of humic acids (HA) from different sampling sites (Antarctica, Brazil, Czech Republic, Mexico and USA) and origin (plant, soil, peat, and coal derived) were obtained by laser desorption/ionization time of flight mass spectrometry (LDI-TOF MS). Optimisation of the experimental conditions are given as the optimal value of the laser energy at 20–30% higher than the threshold. Under these conditions, reproducible mass spectra of HA samples were obtained. In the mass spectra the majority of the peaks are observed in the m/z region 100–1000 Da. Mass spectra fingerprints of HA were analyzed and, in spite of the differences in their origin, a number of common features and profiles (patterns of peaks) were observed in most of the samples. Very similar structural groups (patterns) of the peaks are present in the m/z range 717–918 Da for HA samples of quite different origins, countries or continents.

The tandem LDI-TOF MS and multivariate statistical tools allowed us to extract and elucidate underlying information contained in the mass spectra of the HA samples under study. Applying principal components and cluster analysis, it was, e.g. demonstrated that most of the Antarctica HA samples show distinguishable differences when compared with humic acids from other continents and of different origin.     

Formability and properties of self-standing clay film by montmorillonite with different interlayer cations

Influences of exchangeable interlayer cations were investigated on self-standing film formability, film morphology, and properties of the clay films such as flexibility and gas barrier property. Ion-exchanged montmorillonite samples were prepared by a cation exchange from naturally bearing cation, mostly Na⁺, to Li⁺, Mg²⁺, Ca²⁺, Al³⁺, and Fe^{2+, 3+}. Self-standing films were prepared from aqueous colloidal dispersions of these montmorillonite samples with no additives. The montmorillonite samples with monovalent or divalent cation formed flat self-standing films while the Al-montmorillonite sample produced a distorted film. The Fe-montmorillonite sample formed many separated reddish-brown rod-shaped pieces. Clay film microstructures were different with interlayer cations. The films with monovalent interlayer cations were constructed by the stacking of units with delicately waved thin clay sheets in the whole film, but other films show different morphologies between the upper side and lower side; the upper side is laminated with thin sheets; the lower side is laminated with large thick sheets.The self-standing films’ flexibility and gas barrier property differed according to the interlayer cations. These properties were good in cases of samples with monovalent cations. The innumerable short wave and sheet thinness are considered to foster good flexibility and gas barrier properties. The differences in film formability and properties of the films are attributable to different swellability among samples with different interlayer cations. The montmorillonite samples with monovalent cations swell sufficiently by water, but those with polyvalent cations swell poorly. In the latter case, clay crystals aggregate in water, then the aggregate grows into large particles, creating a film with large particles.     

Photodissociation yield spectroscopy of vinyl bromide cation generated by mass-analyzed threshold ionization: vibrational spectroscopy and decay dynamics in the (~)B state

A new technique [mass-analyzed threshold ionization (MATI)-photodissociation yield spectroscopy] to probe bound excited states of a cation was developed, which measures photodissociation yield of the cation generated by mass-analyzed threshold ionization. A vibrational spectrum of vinyl bromide cation in the (~)B state was obtained using this technique. Optical resolution in the low vibrational energy range of the spectrum was far better than in conventional MATI spectra. The origin of the (~)B state was found at 2.2578+/-0.0003 eV above the first ionization onset. Almost complete vibrational assignment was possible for peaks appearing in the spectrum. Analysis of time-of-flight profiles of C(2)H(3) (+) product ion obtained with different laser polarization angles suggested that photoexcited vinyl bromide cation remained in the (~)B state for several hundred picoseconds prior to internal conversion to the ground state and dissociation therein.     

Thermogravimetric analysis of different molar mass ammonium cations intercalated different cationic forms of montmorillonite

Different cationic forms of montmorillonite, mainly K-, Na-, Ca- and Mg-montmorillonites were intercalated in this study via ion exchange process with mono-, di-, and triethanolammonium cations. The developed samples were characterized by TG, XRD, and CHNS techniques. Thermogravimetric study of ammonium-montmorillonites shows three thermal transition steps, which are attributable to the volatilization of the physically adsorbed water and dehydration, followed by the decomposition of the intercalated ammonium cations and dehydroxylation of the structural water of the modified clay, respectively, while untreated and cationic forms of montmorillonite showed only two decomposition steps. The type of ammonium cation has affected both desorption temperature (Position) and the amount of the adsorbed water (intensity). XRD results show a stepwise change in the crystallographic spacings of montmorillonite with the molar mass of ammonium cation, reflecting a change in the structure of the clay. CHNS data confirm the intercalation of ammonium cations into the interlayer space of montmorillonite and corroborate the effect of the molar mass of ammonium cation on the amount adsorbed by the clay.     

Quantitative determination of inorganic minor cations in sodium-, calcium-, magnesium-matrix simulated samples by capillary electrophoresis

The analysis of ammonium, alkali and alkaline-earth trace cations (0.5 ppm) in samples with a calcium, sodium or magnesium matrix (500 ppm) has been achieved using 10 mM imidazole (pH 4.5) electrolyte to which a complexing agent (15-crown-5, oxalic acid or dipicolinic acid) has been specifically added in order to decrease the electrophoretic mobility of the matrix cation and thus to allow the separation of higher mobility cations at sub-ppm concentrations. The influence of several experimental parameters (complexing agent concentration, buffer pH and temperature) have been studied in order to optimize the separation. The complexing agent concentration appears to be the main parameter governing the selectivity of the cations during the analysis of matrix samples. In optimized conditions, we have checked that the separation between minor inorganic cations is not significantly altered by an increase in the matrix cation concentration. As the concentration of the matrix cation increases, the migration times of minor cations remain unchanged even for a 1000 ppm concentration of the matrix cation. Finally, these optimized buffers allow the quantitation of minor cations down to 0.05% (w/w) for calcium- or magnesium- matrix simulated samples and 0.2% (w/w) for sodium-matrix simulated samples.     

Simultaneous determination of 15 flavonoids in Epimedium using pressurized liquid extraction and high-performance liquid chromatography

Herba Epimedii (family Berberidaceae), Yinyanghuo in Chinese, is one of the commonly used Chinese medicines. Flavonoids are considered as its active components. In this study, a reliable pressurized liquid extraction (PLE) and HPLC method was developed for simultaneous determination of 15 flavonoids, namely hexandraside E, kaempferol-3-O-rhamnoside, hexandraside F, epimedin A, epimedin B, epimedin C, icariin, epimedoside C, baohuoside II, caohuoside C, baohuoside VII, sagittatoside A, sagittatoside B, 2'-O-rhamnosyl icariside II and baohuoside I in different species of Epimedium. The analysis was performed by using a Zorbax SB-C18 analytical column (250 mm x 4.6 mm I.D., 5 microm) at gradient elution of water and acetonitrile with diode-array detection (270 nm). All calibration curves showed good linearity (r(2)>0.9997) within test ranges. The LOD and LOQ were lower than 1.31 ng and 2.62 ng on column, respectively. The RSD for intra- and inter-day of 15 analytes was less than 3.8% at three levels, and the recoveries were 90.5-106.8%. The validated method was successfully applied for the analysis of 15 flavonoids in different species of Epimedium which had great variation on the contents of investigated flavonoids. Hierarchical clustering analysis based on the characteristics of 15 investigated compound peaks in HPLC profiles showed that 26 samples were divided into three main clusters, which were in accordance with their flavonoid contents. Four flavonoids including epimedin A, B, C and icariin were optimized as markers for quality control of the species of Epimedium used as Yinyanghuo.     

Thermal Analysis,Microcalorimetry and Combined Techniques for the Study of the Polymorphic Behaviour of a Purine Derivative

The polymorphic behaviour of the purine derivative MKS 492 was studied with investigations of suspensions of selected samples in different solvents and of samples obtained by crystallizations. The samples were analyzed by DSC, TG and X-ray diffraction. Six different crystalline modifications called A, B, B, C, D and E and an amorphous form were identified. Four pure crystalline modifications, A, B, C and D have been manufactured and characterized by DSC, X-ray, IR, solubilities, densities, hygroscopicity and dissolution measurements. The four forms A, C, D and E are monotrop to the form B. The form B is enantiotrop to the form B, which revealed the highest melting point of all known polymorphs. This form B is only stable at high temperature. Temperature resolved X-ray diffraction was very helpful for proper interpretation of the thermal events. The melting peaks of the forms A and C and the endothermic peak corresponding to the enantiotropic transition B into B occur in a narrow range of temperature. The form B which is the most stable one at room temperature has been chosen for further development. Quantitative methods to determine the content of the forms A, C and D in samples of form B or to determine the content of form A, B and D in form C have been developed by using X-ray diffraction. Limits of detection are 1 or 2%. For the quantitative determination of the amorphous fraction, X-ray diffraction and microcalorimetry are compared. For high amounts of the amorphous fraction, the X-ray diffraction method is preferred because it is faster. Microcalorimetry is very attractive for levels below 10% amorphous content. The lowest limit of detection is obtained by microcalorimetry, about 1%.This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermally stimulated depolarization currents of tactic polymethyl methacrylates and their mixtures

Summary Thermally stimulated depolarization currents (TSDC) of atactic (a), syndiotactic (s) and isotactic (i) PMMA and mixtures ofs- andi-PMMA were measured. In pure tactic PMMA, TSDC peak was obtained at a temperature corresponding to the glass transition temperature of each PMMA. TSDC of mixtures isolated as precipitates from 1/1 and 1/2 (i/sweight ratio) mixed solutions showed a peak which can be attributed to the glass transition temperature of the stereocomplex. TSDC of original l/1 mixture showed two peaks which are ascribed to the glass transition temperature of residual i-PMMA and the stereocomplex. The results suggests that stereocomplex formation occurs ini/s weight ratio of 1/2 independent of the way of preparation.With 9 figures and 1 table     

单柱离子色谱法测定一价阳离子的流动相研究

对单柱离子色谱法测定一价阳离子的流动相进行了系统研究，阐述了一价阳离子的保留行为和电导检测行为与流动相之间的关系，分别对无机酸（硝酸）、有机酸（柠檬酸）和芳香碱（苯胺）为流动相测定一价阳离子进行了讨论，其中有机酸和无机酸是较为适宜的流动相。     

Water sorption and thermally stimulated depolarization currents in nylon-6

The influence of water on the low temperature dielectric relaxations of nylon-6 has been investigated in the range from dry to water-saturated polymer by means of sorption experiments and thermally stimulated depolarization currents (TSDC). Three different ranges of water sorption are observed and their reflection in the TSDC spectra is examined. It is found that position and intensity of the TSDC maxima exhibit characteristic and different behavior in each of these sorption ranges. The critical concentrations are 1.5 ± 0.5% and 6.0 ± 0.5% water content. An interpretation of the experimental results is given with respect to the molecular origins of the low-temperature dielectric relaxations and the mechanisms of water sorption in nylons. The most important idea is that water exists as firmly bound, loosely bound, and clustered water, depending on its concentration. An attempt is made to determine relations between these different states of water in nylon-6 and some characteristic features of the low-temperature TSDC spectrum. © 1996 John Wiley & Sons, Inc.     

Ligands rock & roll: stepwise twisting of two cis-coordinated lopsided N-heterocycles in an octahedral bis(2-phenylazopyridine)-ruthenium(II) complex with seven atropisomers

1H NMR data of alpha-[Ru(azpy)2(MeBim)2](PF6)2 (azpy=2-phenylazopyridine, MeBim=1-methylbenzimidazole), 2, revealed the presence of a total of seven atropisomers at -95 degrees C: three head-to-tail, HT, isomers (A, C, and D), and four head-to-head, HH, isomers which, due to the presence of an intrinsic C2 axis in the alpha-[Ru(azpy)2] moiety, are two sets of identical pairs (B/B and E/E). The NMR data of 2 represent a unique example of a coordination compound that shows a variable temperature (VT) behavior with more, well-defined steps of slow-to-fast exchange of its atropisomers. At 65 degrees C, all atropisomers are in fast exchange; on lowering the temperature the sharp signals first broaden (at room temperature) and consecutively split up into two sets of relatively sharp signals, in slow exchange, at about 0 degrees C (D, 40 %, and the coalesced signals of ABBCEE, 60 %). Upon further cooling, the set of peaks belonging to D remain sharp until the lowest recording temperatures. The signals of the other set of resonances, on the other hand, first broaden again and then separate into two sets of broad peaks (C/E/E and A) and one set of sharp peaks (B and B in fast exchange); on lowering the temperature even more, these signals broaden once again and finally, at -95 degrees C, are split up into a total of four sets of signal (A, B/B, C, and E/E). At low temperatures, ROESY experiments revealed that atropisomerization occurs through the synchronous rotation of both MeBim ligands in the interconversion of the two "identical" HH atropisomers B and B, as well as in the interconversion between C and E/E. The HH rotamers B/B furthermore exhibit a slow-to-fast exchange atropisomerization behavior that is observed independently from the other dynamic processes in this compound. The versatile cis bifunctional binding of the DNA model bases (MeBim ligands) in 2 parallels the observation of alpha-[Ru(azpy)2Cl2] which shows extraordinarly high cytotoxicity against tumor cell lines.