DNA binding, oxidative DNA cleavage, cytotoxicity, and apoptosis-inducing activity of copper(II) complexes with 1,4-tpbd (N,N,N',N'-tetrakis(2-yridylmethyl)benzene-1,4-diamine) ligand

Three new binuclear copper(II) complexes have been synthesized and structurally characterized by X-ray crystallography, [Cu₂(1,4-tpbd)(dafo)₂(MeOH)₂](ClO₄)₄·2.5H₂O (1), [Cu₂(1,4-tpbd) (DMSO)₂(ClO₄)₂](OH)₂·6H₂O (2) and [Cu₂(1,4-tpbd)(OAC)₂(ClO₄)₂]·5H₂O (3) (1,4-tpbd = N,N,N′,N′-tetrakis(2-pyridylmethyl)benzene-1,4-diamine). Complex 1 to 3 shows similar binuclear structure and each Cu atom adopts five-coordinated square-pyramidal geometry. The interactions of the three complexes with CT-DNA (Calf-thymus DNA) have been investigated by UV absorption, fluorescence spectroscopy, circular dichroism spectroscopy and viscosity. Furthermore, the three complexes display oxidative cleavage of supercoiled DNA in the presence of external agents. Complex 3 shows higher DNA affinity and nuclease activity may be attributed to its cis structural configuration and labile acetate and perchlorate anions. The cleavage mechanisms between the complexes and plasmid DNA are likely to involve singlet oxygen or singlet oxygen-like entity as reactive oxygen species. In addition, in vitro cytotoxicity studies on the Hela cell line show that the IC₅₀ values of complexes 1-3 are 14.75, 13.67 and 16.58 μM, respectively. The apoptosis-inducing activity was also assessed by AO/EB (Acridine Orange/Ethidium bromide) staining assay, indicating they have the potential to act as effective metal-based anticancer drugs.     

Chirality in Distorted Square Planar Pd(O,N)2 Compounds

Salicylidenimine palladium(II) complexes trans‐Pd(O,N)₂ adopt step and bowl arrangements. A stereochemical analysis subdivides 52 compounds into 41 step and 11 bowl types. Step complexes with chiral N‐substituents and all the bowl complexes induce chiral distortions in the square planar system, resulting in Δ/Λ configuration of the Pd(O,N)₂ unit. In complexes 1 , 2 , 3 , 4 , 5 , 6 with enantiomerically pure N‐substituents ligand chirality entails a specific square chirality and only one diastereomer assembles in the lattice. Dimeric Pd(O,N)₂ complexes with bridging N‐substituents in trans‐arrangement are inherently chiral. For dimers 7 , 8 , 9 , 10 , 11 different chirality patterns for the Pd(O,N)₂ square are observed. The crystals contain racemates of enantiomers. In complex 12 two independent molecules form a tight pair. The (R_C) configuration of the ligand induces the same Δ chirality in the Pd(O,N)₂ units of both molecules with varying square chirality due to the different crystallographic location of the independent molecules. In complexes 13 and 14 atrop isomerism induces specific configurations in the Pd(O,N)₂ bowl systems. The square chirality is largest for complex 15 [(Diop)Rh(PPh₃)Cl)], a catalyst for enantioselective hydrogenation. In the lattice of 15 two diastereomers with the same (R_C,R_C) configuration in the ligand Diop but opposite Δ and Λ square configurations co‐crystallize, a rare phenomenon in stereochemistry. Chirality 25:663–667, 2013. © 2013 Wiley Periodicals, Inc.     

Environmental regulation of H2 utilization (3H2 exchange) among natural and laboratory populations of N2 and non-N2 fixing phytoplankton

Regulation of H₂ utilization, as monitored by the hydrogenase-mediated³H₂ exchange reaction, was examined among phytoplankton communitiesin situ and populations in culture. During a 2-year study in the Chowan River, North Carolina, at least 2 major groups of phytoplankton dominated³H₂ exchange rates. They included N₂ fixing cyanobacteria and NO₃ ^}- utilizing genera. Utilization of³H₂ by N₂ fixers was mainly dark-mediated, whereas³H₂ utilization associated with periods of NO₃ ^}- abundance revealed an increasing dependence on light. Inhibitors of N₂ fixation (C₂H₂ and NH₄ ⁺) negatively affected³H₂ utilization, substantiating previous findings that close metabolic coupling of both processes exists among N₂ fixing cyanobacteria. Conversely, NO₃ ^}- stimulated³H₂ utilization among N₂ and non-N₂ fixing genera, particularly under illuminated conditions. A variety of environmental factors were shown to control³H₂ exchange. In addition to the nitrogen sources discussed above, dissolved O₂, photosynthetically available radiation (PAR), temperature, and pH changes altered³H₂ exchange rates. It is likely that other factors not addressed here could also affect³H₂ exchange rates. At least 2 ecological benefits from H₂ utilization in natural phytoplankton can be offered. They include the simultaneous generation of adenosine triphosphate (ATP) and consumption of O₂ during the oxidation of H₂ via an oxyhydrogen or “Knallgas” reaction. Both processes could help sustain phytoplankton, and particularly cyanobacterial, bloom intensity under natural conditions when O₂ supersaturation is common in surface waters. H₂ utilization appeared to be a general feature of natural and laboratory phytoplankton populations. The magnitudes of³H₂ utilization rates were directly related to community biomass. Although it can be shown that utilization rates are controlled by specific environmental factors, the potential relationships between H₂ utilization and phytoplankton primary production remain poorly understood.     

Synthesis,characterization, and evaluation of (E)-methyl 2-((2-oxonaphthalen-1(2H)-ylidene)methylamino)acetate as a biological agent and an anion sensor

An amino acid based and bidentate Schiff base, (E)-methyl 2-((2-oxonaphthalen-1(2H)-ylidene)methylamino)acetate (ligand), was synthesized from the reaction of glycine-methyl ester hydrochloride with 2-hydroxy-1-naphthaldehyde. Characterization of the ligand was carried out using theoretical quantum–mechanical calculations and experimental spectroscopic methods. The molecular structure of the compound was confirmed using X-ray single-crystal data, NMR, FTIR and UV–Visible spectroscopy, which were in good agreement with the structure predicted by the theoretical calculations using density functional theory (DFT). Antimicrobial activity of the ligand was investigated for its minimum inhibitory concentration (MIC) to several bacteria and yeast cultures. UV–Visible spectroscopy studies also shown that the ligand can bind calf thymus DNA (CT-DNA) electrostatic binding. In addition, DNA cleavage study showed that the ligand cleaved DNA without the need for external agents. Energetically most favorable docked structures were obtained from the rigid molecular docking of the compound with DNA. The compound binds at the active site of the DNA proteins by weak non-covalent interactions. The colorimetric response of the ligand in DMSO to the addition of equivalent amount of anions (F⁻, Br⁻, I⁻, CN⁻, SCN⁻, ClO₄⁻, HSO₄⁻, AcO⁻, H₂PO₄⁻, N₃⁻ and OH⁻) was investigated and the ligand was shown to be sensitive to CN⁻ anion.     

N2(C2H2)ASE ACTIVITY BY ALNUS INCANA SSP. RUGOSA (BETULACEAE) IN THE NORTHERN HARDWOOD FOREST

Field assays of N₂(C₂H₂)ase activity were performed with intact nodules from a pure alder site (alder) and a mixed alder-aspen site (aspen). Assays were performed between 12 June and 12 August 1980 and in May 1981. N₂(C₂H₂)ase rates are expressed as g N g nodule oven-dry wt⁻¹ hr⁻¹ (g N g⁻¹ hr⁻¹). Diurnal N₂(C₂H₂)ase activity showed an increase in both sites between 0600 and midday, then decreased to a low by 1800. Nighttime activity in the May 1981 assay was approximately 25% of the daytime peak. Mean (±SE) 1200 hr N₂(C₂H₂)ase activity (μg N g⁻¹ hr⁻¹) for all sizes in the alder stand rose from 24.56 ± 6.56 on 12 June to 73.96 ± 28.37 on 26 June and declined to 9.20 ± 2.56 by 12 August. In the aspen stand activity decreased from the 12 June rate of 21.81 ± 4.59 to 3.64 ± 1.87 on 24 July but then increased to 30.00 ± 7.39 by 12 August. Based on diurnal assays, the seasonal mean N influx (μg N g⁻¹ hr⁻¹) is statistically higher (P 0.05) in the alder stand with a value of 26.70 compared to 14.63 in the aspen stand. Small size class shrubs had significantly higher (P < 0.05) N₂(C₂H₂)ase activity (μg N g⁻¹ hr⁻¹) in diurnal assays than medium or large class shrubs. The estimated mean (±SE) N₂(C₂H₂)ase activity (mg N g⁻¹ season⁻¹) for all sizes was 44.4 ± 18.6 in the alder stand compared to 16.2 ± 5.2 in the aspen stand. Nodule excavations showed the g shrub⁻¹ in the alder stand to be 16.48 ± 10.29, 38.57 ± 12.34 and 29.11 ± 7.15 for small, medium and large size shrubs and 12.73 ± 3.23, 28.21 ± 4.36 and 56.45 ± 16.23 for respective sizes in the aspen stand. Seasonal N influx was 4.69 kg ha⁻¹ in the alder stand and 0.84 kg ha⁻¹ in the aspen stand, representing 17.9% of the alder stand. Nitrogen feedback inhibition from uric acid-N influx and allelochemic interference from aspen are discussed as explanations for the differences in N influx in the two stands.     

Conformational preferences of modified nucleoside N(2)-methylguanosine (m(2)G) and its derivative N(2), N(2)-dimethylguanosine (m(2)(2)G) occur at 26th position (hinge region) in tRNA

Conformational preferences of the modified nucleosides N²-methylguanosine (m²G) and N², N²-dimethylguanosine (m₂²G) have been studied theoretically by using quantum chemical perturbative configuration interaction with localized orbitals (PCILO) method. Automated complete geometry optimization using semiempirical quantum chemical RM1, along with ab initio molecular orbital Hartree–Fock (HF-SCF), and density functional theory (DFT) calculations has also been made to compare the salient features. Single-point energy calculation studies have been made on various models of m²G26:C/A/U44 and m₂²G26:C/A/U44. The glycosyl torsion angle prefers “syn” (χ = 286°) conformation for m²G and m₂²G molecules. These conformations are stabilized by N(3)–HC2′ and N(3)–HC3′ by replacing weak interaction between O5′–HC(8). The N²-methyl substituent of (m²G26) prefers “proximal” or s-trans conformation. It may also prefer “distal” or s-cis conformation that allows base pairing with A/U44 instead of C at the hinge region. Thus, N²-methyl group of m²G may have energetically two stable s-trans m²G:C/A/U or s-cis m²G:A/U rotamers. This could be because of free rotations around C–N bond. Similarly, N², N²-dimethyl substituent of (m₂²G) prefers “distal” conformation that may allow base pairing with A/U instead of C at 44th position. Such orientations of m²G and m₂²G could play an important role in base-stacking interactions at the hinge region of tRNA during protein biosynthesis process.     

Synthesis, 95Mo NMR spectra and x-ray crystal structure of MoO2(C14H11N2O)2(C2H5H)1 and Mo2O5(C14H11N2O)2(C2H5OH)1(H2O)1

The crystal structures and ⁹⁵Mo NMR spectra of two complexes formed between 2-α-hydroxybenzyl- benzimidazole (C₆H₅·CHOH·C₇H₅N₂=HOBB), as its sodium salt, and MoO₂Cl₂ are reported. [MoO₂- (OBB)₂]·EtOH (OBB=deprotonated HOBB) crystallizes in space group P2₁/n, with a=12.8441(7), b=15.917(3), c=13.314(2) Å, β=97.163(8)° and Z =4. The structure was determined from 3096 observed reflections and refined to a final R value of 0.030. The complex is a six coordinate cis-dioxo species, the ⁹⁵Mo spectrum of which shows a single sharp peak at 56 ppm in dimethylformamide (DMF). The second complex, [Mo₂O₅(OBB)₂]·EtOH·H₂O, crystallizes in space group Pbca, with a=22.482(4), b=16.442(3), c=18.407(3) Å and Z=8. The structure was determined from 2936 observed reflections and refined to a final R value of 0.061. The complex is a binuclear doubly bridged species in which one metal atom is six coordinate while the other is five coordinate. Its ⁹⁵Mo NMR spectrum in DMF shows a sharp peak at 124 ppm and a second broader much weaker peak at 51 ppm.     

N2 Fixation (C2H2 reduction) by epiphylls on coffee,Coffea arabica

Nitrogen fixation (C₂H₂ reduction) by epiphylls on coffee,Coffea arabica, grown in sites with different degrees of shade, was determined. Coffee leaves with nitrogen-fixing epiphylls were found in all sites in approximately equal numbers. Rates of C₂H₂ reduction were similar for all sites and throughout the year, averaging 3.21 nmoles C₂H₂ reduced leaf with epiphylls^–1 day^–1. Apparently, neither rates of activity nor abundance of leaves with nitrogen-fixing epiphylls is related to the degree of shade in a site. No correlation was found between percent epiphyll cover and the presence or magnitude of nitrogen-fixing activity. Calculated annual fixation by epiphylls on coffee was low, ranging from 0.7 g N₂ ha^–1 year^–1 for the shadeless site to 1.4 g N₂ ha^–1 year^–1 for the site withIngajinicuil shade trees. These results suggest that epiphyll fixation is not an important source of nitrogen for the coffee ecosystem studied.     

Homogeneous CO hydrogenation and transfer hydrogenation catalyzed by ruthenium(II) complexes containing optically active Ph2PCH(Ph)CH(Me)NH2 and 1,2-C5H8(PPh2)2 ligands

Combination of (1S,2S)-cyclopentanediylbis(diphenylphosphine) with [Ru(η⁴-C₈H₁₂){η³-(CH₂)₂CMe}₂] afforded the chelate complex [Ru{η³-(CH₂)₂CMe}₂{(1S,2S)-C₅H₈(PPh₂)₂}] (1), which gave (OC-6-13)-[RuCl₂{(1S,2S)-C₅H₈(PPh₂)₂}{(1S,2S)-Ph₂PCH(Ph)CH(Me)NH₂}] (2) upon reaction with methanolic HCl in acetone, followed by the addition of the β-aminophosphine in DMF. The (P ∩ N)₂-chelated complexes (OC-6-13)-[RuCl₂{(1S,2S)-Ph₂PCH(Ph)CH(Me)NH₂}₂] (3) and (OC-6-13)-[RuCl₂{(1R,2S)-Ph₂PCH(Ph)CH(Me)NH₂}₂] (4) resulted from RuCl₃ · 3H₂O and the P,N ligands under reducing conditions. The crystal structures of 3 and 4 were determined by single-crystal X-ray diffraction. Following activation by KOBu-t in isopropanol, compounds 2–4 catalyzed the enantioselective transfer hydrogenation of acetophenone with i-PrOH as the hydrogen source as well as the direct hydrogenation of the ketone by H₂ in low to moderate e.e. (up to 67%).     

Acetylene reduction,H2 evolution and 15N2 fixation in the Alnus incana-Frankia symbiosis

Acetylene reduction, ¹⁵N₂ reduction and H₂ evolution were measured in root systems of intact plants of grey alder (Alnus incana (L.) Moench) in symbiosis with Frankia. The ratios of C₂H₂: ¹⁵N₂ were compared with C₂H₂:N₂ ratios calculated from C₂H₂ reduction and H₂ evolution, and with C₂H₂:N₂ ratios calculated from accumulated C₂H₄ production and nitrogen content. It was possible to calculate C₂H₂:N₂ ratios from C₂H₂ reduction and H₂ evolution because this source of Frankia did not show any hydrogenase activity. The ratios obtained using the different methods ranged from 2.72 to 4.42, but these values were not significantly different. It was also shown that enriched ¹⁵N could be detected in the shoot after a 1-h incubation of the root-system. It is concluded that the measurement of H₂ evolution in combination with C₂H₂ reduction represents a nondestructive assay for nitrogen fixation in a Frankia symbiosis which shows no detectable hydrogenase activity.     

Purification,properties and primary structure of H2-formingN 5,N10-methylenetetrahydromethanopterin dehydrogenase fromMethanococcus thermolithotrophicus

H₂-FormingN ⁵,N¹⁰-methylenetetrahydromethanopterin dehydrogenase (Hmd) is a novel type of hydrogenase found in methanogenic Achaea that contains neither nickel nor iron-sulfur clusters. The enzyme has previously been characterized fromMethanobacterium thermoautotrophicum and fromMethanopyrus kandleri. We report here on the purification and properties of the enzyme fromMethanococcus thermolithotrophicus. Thehmd gene was cloned and sequenced. The results indicate that the enzyme fromMc. thermolithotrophicus is functionally and structurally closely related to the H₂-forming methylene tetrahydromethanopterin dehydrogenase fromMb. thermoautotrophicum andMp. kandleri. From amino acid sequence comparisons of the three enzymes, a phylogenetic tree was deduced that shows branching orders similar to those derived from sequence comparisons of the 16S rRNA of the orders Methanococcales, Methanobacteriales, and Methanopyrales.Abbreviations H ₂ Forming dehydrogenase orHmd - H₂-FormingN ⁵,N¹⁰ methylene tetrahydromethanopterin dehydrogenase - H ₄MPT Tetrahydromethanopterin - CH ₂=H₄MPT N⁵,N¹⁰ Methylene tetrahydromethanopterin - CHH ₄MPT⁺ N⁵,N¹⁰ Methenyltetrahydromethanopterin - MALDI-TOF-MS Matrix-assisted laser desorption     

Azolla-Anabaena azollae Relationship: V. N(2) Fixation, Acetylene Reduction, and H(2) Production

In order to characterize the reactions catalyzed by nitrogenase in the Azolla-Anabaena association, ¹⁵N₂ fixation, C₂H₂ reduction, and ATP-dependent H₂ production were measured in both the Azolla-Anabaena complex and in the alga isolated from the complex.     

Abiotic synthesis of organic molecules from minerals containing traces of dissolved H2O,CO2 and N2 part II: Experimental data

Even though a given mineral, for instance olivine, may contain only traces of dissolved H₂O, CO₂ and N₂ the gases which evolve from its surface during heating comprise (a) highly reduced molecules such as H₂, CH₄, C_mH_n and more complex hydrocarbons, HCN and other N-bearing compounds (b) oxidized species in various degrees of oxidation from formaldehyde and CO to oxygen. These gases evolve sequentially besides H₂O, CO₂ and possibly N₂, their relative amounts being controlled by experimental parameters such as the rate of heating. Preliminary indications of amino acids have been obtained by liquid extraction. The chemical complexity is a consequence of radical reactions between different solute species in the surface and the bulk of the mineral grains. Data for synthetic MgO and for mantle-derived olivine are presented.     

Effect of H2S on the formation of organic compounds from C,N, H,S model atmospheres submitted to a glow discharge

H₂S has been often invoked as the initial source of sulfur in prebiotic evolution, and several sulfur-containing compounds has been proposed as intermediates in the primordial synthesis of biologically relevant sulfur-containing chemicals. The possibilities of synthesis of the principal key intermediates by glow discharges in CH₄−N₂−H₂S mixtures is studied. It is shown that synthesis of important intermediates such as HCN, (CN)₂, CHCCN and CH₃SH is possible from such mixtures if the amount of H₂S is not more than 10%. For higher amounts of H₂S, the syntheses are strongly inhibited.     

HN(CA)N and HN(COCA)N experiments for assignment of large disordered proteins

Two new 3D HN-based experiments are proposed for backbone assignment of large disordered proteins. The spectra obtained with the new pulse schemes are free of redundant diagonal peaks (H_iN_i–N_i) and provide sequential correlations (H_iN_i–N_i+1 and H_iN_i–N_i?1) not only between adjacent non-proline residues but also between non-proline and proline residues. The experiments have been demonstrated on an intrinsically disordered protein with 306 amino acids including 64 proline residues. Using the two experiments, we obtained nearly complete assignments of backbone amides and proline ¹⁵N spins except for 4 proline and 4 non-proline residues.     

Growth, denitrification and nitrate ammonification of the rhizobial strain TNAU 14 in presence and absence of C2H4 and C2H2

Soil-N (NO₃ ^?) initiates as far as a threshold concentration is surpassed manifold physiological reactions on N₂-fixation. Organic N and ammonium oxidised to NO₃ ^? means oxygen depletion. Plants suffering under O₂ or infection stress start to excrete ethylene (C₂H₄). C₂H₄ widens the root intercellulars that O₂-respiration will continue. Now microbes may more easily enter the plant interior by transforming the reached methionine into C₂H₄. Surplus nitrate and C₂H₄ inhibit nodulation of leguminous plants. Excess NO₃ ^? in the nodulesphere could be diminished by N₂-fixing bacteria which in addition can denitrify or ammonify nitrate. Consequently, it was asked whether C₂H₄ interferes with the potential of N₂-fixing bacteria to reduce nitrate. The groundnut-nodule isolate TNAU 14, from which it was known that it denitrifies and ammonifies nitrate, served as inoculum of a KNO₃-mannitol-medium that was incubated under N₂-, 1% (v/v) N₂?C₂H₄-, and 1% (v/v) N₂?C₂H₂-atmosphere in the laboratory. C₂H₂ was included into the experiments because it is frequently used to quantify N₂-fixing potentials (acetylene reduction array, ARA). Gene-16S rDNA-sequencing and physiological tests revealed a high affiliation of strain TNAU 14 toRhizobium radiobacter andRhizobium tumefaciens. Strain TNAU 14 released N₂O into the bottle headspace in all treatments, surprisingly significantly less in presence of C₂H₂. Nitrate-ammonification was even completely blocked by C₂H₂. C₂H₄, in contrast rather stimulated growth, denitrification, and nitrate-ammonification of strain TNAU 14 which consumed the released NH₄ ⁺ during continuing incubation.     

Synthesis and characterization of carbamoyl methyl pyrazole(CMPz) compounds of palladium(II) chloride: The crystal and molecular structure of [PdCl2{C3H3N2CH2CONBu2}2]

Carbamoyl methyl pyrazole compound of palladium(II) chloride of the type [PdCl₂L₂] (where L =  C₅H₇N₂CH₂CON(C₄H₉)₂, C₅H₇N₂CH₂CON(ⁱC₄H₉)₂, C₃H₃N₂CH₂CON(C₄H₉)₂, or C₃H₃N₂CH₂CON(ⁱC₄H₉)₂) has been synthesized and characterized by IR and ¹H NMR spectroscopy. The structure of the compound [PdCl₂{C₃H₃N₂CH₂CONⁱBu₂}₂] has been determined by single crystal X-ray diffraction and shows that the ligands are bonded through the soft pyrazolyl nitrogen atom to the palladium(II) chloride in a trans disposition.     

Solution-mediated syntheses and characterizations of two new zincophosphites [C6H14N2]0.5[Zn(H2PO3)2] and [C4H12N2]0.5[(CH3)2NH2][Zn2(HPO3)3]

Two new zincophosphites [C₆H₁₄N₂]_0.5[Zn(H₂PO₃)₂] 1 and [C₄H₁₂N₂]_0.5[(CH₃)₂NH₂][Zn₂(HPO₃)₃] 2 have been solvothermally synthesized in mixed solvents of N,N-dimethylformamide (DMF) and 1,4-dioxane (DOA), respectively. Single-crystal X-ray diffraction analysis reveals that compound 1 exhibits a neutral inorganic chain formed by ZnO₄ and HPO₂(OH) units. Interestingly, the left- and right-handed hydrogen-bonded helical chains are alternately formed via the hydrogen-bonds between two adjacent chains. Compound 2 exhibits a layer structure with 4- and 12-MRs formed by ZnO₄ and HPO₃ units, in which two kinds of organic amine molecules both act as countercations to compensate the overall negative electrostatic charge of the anionic network.     

Structural and equilibrium studies on mixed ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II) with N-(2-benzimidazolyl)methyliminodiacetic acid and typical N, N donor ligands

Mixed ligand complexes: [Co(L)(bipy)] · 3H₂O (1), [Ni(L)(phen)] · H₂O (2), [Cu(L)(phen)] · 3H₂O (3) and [Zn(L)(bipy)] · 3H₂O (4), where L²⁻ = two -COOH deprotonated dianion of N-(2-benzimidazolyl)methyliminodiacetic acid (H₂bzimida, hereafter, H₂L), bipy = 2,2′ bipyridine and phen = 1,10-phenanthroline have been isolated and characterized by elemental analysis, spectral and magnetic measurements and thermal studies. Single crystal X-ray diffraction studies show octahedral geometry for 1, 2 and 4 and square pyramidal geometry for 3. Equilibrium studies in aqueous solution (ionic strength I = 10⁻¹ mol dm⁻³ (NaNO₃), at 25 ± 1 °C) using different molar proportions of M(II):H₂L:B, where M = Co, Ni, Cu and Zn and B = phen, bipy and en (ethylene diamine), however, provides evidence of formation of mononuclear and binuclear binary and mixed ligand complexes: M(L), M(H₋₁L)⁻, M(B)²⁺, M(L)(B), M(H₋₁L)(B)⁻, M₂(H₋₁L)(OH), (B)M(H₋₁L)M(B)⁺, where H₋₁L³⁻ represents two -COOH and the benzimidazole N₁-H deprotonated quadridentate (O⁻, N, O⁻, N), or, quinquedentate (O⁻, N, O⁻, N, N⁻) function of the coordinated ligand H₂L. Binuclear mixed ligand complex formation equilibria: M(L)(B) + M(B)²⁺ ? (B)M(H₋₁L)M(B)⁺ + H⁺ is favoured with higher π-acidity of the B ligands. For Co(II), Ni(II) and Cu(II), these equilibria are accompanied by blue shift of the electronic absorption maxima of M(II) ions, as a negatively charged bridging benzimidazolate moiety provides stronger ligand field than a neutral one. Solution stability of the mixed ligand complexes are in the expected order: Co(II) < Ni(II) < Cu(II) > Zn(II). The Δ log K_M values are less negetive than their statistical values, indicating favoured formation of the mixed ligand complexes over the binary ones.     

Abiotic synthesis of organic molecules from minerals containing traces of dissolved H2O,CO2 and N2 part I: Basic principles

Oxides and silicates which crystallize in the presence of H₂O, CO₂ and N₂, especially at high pressures, are expected to dissolve traces of these fluid components. In doing so atomic and electronic rearrangements occur between the host lattice and the dissolved molecules which lead to different solute species. These may be simply hydroxyl OH^–, carbonate CO₃ ^2– of similar ions, but other species can also form which are chemically reduced such as molecular H₂, CO₂ ^2– and CO^– or oxidized such as peroxy ions, O₂ ^2–. When the minerals containing such solute species are decompressed and cooled, they eventually become supersaturated with respect to their dissolved impurities. If the relative mobilities of the different solute species are different, diffusion and subsurface segregation lead to spatial separation: the surface and subsurface zone become enriched in the reduced species while the oxidized species remain in the bulk. Upon heating or during chemical dissolution (weathering) the reduced species contained in the surface react leading to the formation of a wide variety of H–C–O–N molecules: not only H₂O, CO₂ and possibly N₂ but also organic molecules. No external reduced atmosphere is needed, according to this hypothesis.