Syntheses and characterization of neutral complexes of Zn(II) with mono- and dianionic pyrrole-2-imine ligands [(pyrrole-2-CHN)nR]n− (n = 1, 2)

The reactions of the dianionic [(pyrrole-2-CHN)₂R]^2? ligands [(N′₂N₂)^2?] (R = (R)(S)-1,2-cyclohexane or 1,2-ethane) with Zn(II) yield neutral dimeric [Zn₂(N′₂N₂)₂] complexes. The dimeric nature of the complexes was established by field-desorption mass spectrometry. ¹H NMR studies show that these complexes have dimeric structures in solution in which the (N′₂N₂)^2? ligands act as di-bidentates.The metal centres have tetrahedral geometries and bot have Δ or Λ configurations. The complex with the (R)(S)-1,2-cyclohexanediyl bridges has a rigid structure in solution. Neither intermolecular nor intramolecular exchange processes are observed The ¹H NMR spectrum of the complex with the 1,2-ethanediyl bridging groups shows that at 213 K in CDCl₃ a fast conformational movement is already taking place between two identical structures of the complex. It is not possible to determine whether in this complex intermolecular exchange processes are also taking place.The reactions of the anionic [pyrrole-2-CHNR′]^? ligands [(N′N)^?] (R′ = t-Bu, i-Pr, (S)-CHMePh or 2,6-xylyl) with Zn(II) yield the neutral Zn(N′N)₂ complexes. These complexes were synthesized to study the coordination properties of the [pyrrole-2-CHNR′]^? moieties with Zn(II). A ¹H NMR study established that the zinc centres in the complexes containing the prochiral i-Pr or chiral (S)-CHMePh substituents have tetrahedral geometries with Δ or Λ configurations in CDCl₃ at 213 K. These complexes undergo an intramolecular exchange process at higher temperatures (above 260 K when R′ = i-Pr) which involves inversion of the configuration of the zinc centre. A mechanism for this exchange process is proposed.     

Methane emission from global livestock sector during 1890–2014: Magnitude,trends and spatiotemporal patterns

Human demand for livestock products has increased rapidly during the past few decades largely due to dietary transition and population growth, with significant impact on climate and the environment. The contribution of ruminant livestock to greenhouse gas (GHG) emissions has been investigated extensively at various scales from regional to global, but the long‐term trend, regional variation and drivers of methane (CH₄) emission remain unclear. In this study, we use Intergovernmental Panel on Climate Change (IPCC) Tier II guidelines to quantify the evolution of CH₄ emissions from ruminant livestock during 1890–2014. We estimate that total CH₄ emissions in 2014 was 97.1 million tonnes (MT) CH₄ or 2.72 Gigatonnes (Gt) CO₂‐eq (1 MT = 10¹² g, 1 Gt = 10¹⁵ g) from ruminant livestock, which accounted for 47%–54% of all non‐CO₂ GHG emissions from the agricultural sector. Our estimate shows that CH₄ emissions from the ruminant livestock had increased by 332% (73.6 MT CH₄ or 2.06 Gt CO₂‐eq) since the 1890s. Our results further indicate that livestock sector in drylands had 36% higher emission intensity (CH₄ emissions/km²) compared to that in nondrylands in 2014, due to the combined effect of higher rate of increase in livestock population and low feed quality. We also find that the contribution of developing regions (Africa, Asia and Latin America) to the total CH₄ emissions had increased from 51.7% in the 1890s to 72.5% in the 2010s. These changes were driven by increases in livestock numbers (LU units) by up to 121% in developing regions, but decreases in livestock numbers and emission intensity (emission/km²) by up to 47% and 32%, respectively, in developed regions. Our results indicate that future increases in livestock production would likely contribute to higher CH₄ emissions, unless effective strategies to mitigate GHG emissions in livestock system are implemented.     

Postnatal changes in subcellular distribution of copper,zinc and metallothionein in the liver of bank vole (Clethrionomys glareolus): a possible involvement of metallothionein and copper in cell proliferation

1. Dramatic interdependent changes in the intracellular concentrations of copper (Cu), zinc (Zn) and metallothionein (MT) in the liver of bank voles during the first 30 days of their life were observed.2. The post-mitochondrial Cu, Zn and MT (ZnMT) abruptly decreased between 1 and 3 days following birth but the nuclear MT (CuMT) and Cu increased at the same time, suggesting that Cu displaced Zn already bound to MT in the cytoplasm and subsequently the complex CuMT was translocated to the nuclei.3. The nuclear Cu concentration reached the highest level (62–71% of the total tissue Cu) in the period from day 3 to day 20 post-partum, just prior to and during a rapidly growing liver.4. The data indicate that MT and Cu may be involved in the hepatocyte proliferation.     

Metal stoichiometry of isolated and arsenic substituted metallothionein: PIXE and ESI-MS study

The stoichiometric analysis of the metal induced Metallothionein (MT) is pertinent for understanding the metal-MT interactions. Despite innumerable publications on MT, the literature addressing these aspects is limited. To bridge this gap, PIXE and ESI-MS analysis of the commercial rabbit liver MT1 (an isoform of MT), zinc induced isolated rat liver MT1, apo and Arsenic substituted rabbit liver MT1 have been carried out. These techniques in combination provide information about number and the signature of all the metal ions bound to MT. By using ESI-MS in the rabbit MT1, ions of Zn _n MT1 (n = 0, 1, 4, 5, 6, 7) whereas, in rat MT1, the Zn₁MT1 and Zn₅MT1 ions are observed. PIXE analysis shows that some copper along with zinc is also present in the rabbit as well as rat MT1 which could not be assessed with ESI-MS. During As metallation reaction with rabbit MT1, with increase in arsenic concentration, the amount of arsenic bound to MT1 also increases, though not proportionally. The presence of both Zn and Cu in MT1 on Zn supplementation can be related to the role of MT in Zn and Cu homeostasis. Further, the presence of partially metallated MT1 suggests that MT1 may donate fractional amount of metal from it’s fully metallated form to other proteins where Zn acts as a cofactor.     

Investigation of the spectral characteristics of Sm3+ ions in lead borosilicate glass for photonic applications

Different concentrations of Sm₂O₃-doped lead borosilicate glass were synthesized using a melt–quenching method and their characteristics were analyzed using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy absorption, emission, and decay curves. From the XRD patterns, the noncrystalline nature of titled glass was confirmed. The structural groups that existed in the host glass were observed from FTIR spectra. The Judd–Ofelt (JO) intensity parameters and oscillator strengths were derived from the absorption spectra and compared with various reported systems. The excitation luminescence levels of the Sm³⁺ ion radiative properties were further computed using the JO intensity parameters. Effective bandwidth, emission cross-sections (σ_e), and several lasing properties were assessed from emission spectra and compared with other reported glass systems. The decay curves of the ⁴G_5/2 level of Sm³⁺ ion were also been measured and examined. Additionally, the colour coordinates of the Commission International de I'Éclairage chromaticity were assessed. The titled glass were suitable for visible reddish orange luminescence devices based on all obtained parameters.     

Is Ag(I) an adequate probe for Cu(I) in structural copper–metallothionein studies?

The binding abilities of silver(I) to mammalian MT 1 have been studied and compared with those of copper(I), recently reported [Bofill et al. (2001) J Biol Inorg Chem 6:408–417], with the aim of analyzing the suitability of Ag(I) as a Cu(I) probe in Cu–MT studies. The Zn/Ag replacement in recombinant mouse Zn₇–MT 1 and corresponding Zn₄-MT 1 and Zn₃-MT 1 fragments, as well as the stepwise incorporation of Ag(I) to the corresponding apo-MTs, have been followed in parallel by various spectroscopic techniques including electronic absorption (UV–vis), circular dichroism (CD) and electrospray mass spectrometry coupled to capillary zone electrophoresis (CZE-ESI-MS). A comparative analysis of the sets of data obtained in the titration of Zn₇–MT 1, Zn₄–MT 1 and Zn₃-MT 1 with AgClO₄ at pH 7.5 and 2.5 has led to the reaction pathways followed during the incorporation of silver to these proteins under these specific conditions, disclosing unprecedented stoichiometries and structural features for the species formed. Thus, the Zn/Ag replacement in Zn₇–MT 1 at pH 7.5 has revealed the subsequent formation of Ag₄Zn₅–MT, Ag₇Zn₃–MT, Ag₈Zn₃–MT, Ag₁₀Zn₂–MT, Ag₁₂Zn₁–MT, Ag_x–MT, x=14–19, whose structure consists of two additive domains only if Zn(II) remains coordinated to the protein. A second structural role for Zn(II) has been deduced from the different folding found for the Ag_x–MT species of the same stoichiometry formed at pH 7.5 or 2.5. Comparison of the binding features of Cu(I) and Ag(I) to the entire MT at pH 7.5 shows that, among all the _xZn_y–MT (0y<7) species found, only M^I₄Zn₅–MT [(Zn₄)(₄Zn₁)] and M^I₇Zn₃–MT [(₃Zn₂)(₄Zn₁)], which form during the first stages of the Zn(II)/M(I) metal replacement, show comparable 3D structures; thus, they are the only species where Ag(I) ions can be predicted to be an adequate probe for Cu(I).Electronic Supplementary Material Supplementary material is available in the online version of this article at .     

Luminescence of the near‐ultraviolet blue‐emitting Ba9Al2Si6O24:Ce3+ phosphor

A near‐ultraviolet (NUV) blue‐emitting phosphor Ba₉Al₂Si₆O₂₄:Ce³⁺ (BAS:Ce³⁺) was synthesized using a high‐temperature solid‐state reaction. BAS:Ce³⁺ had an excitation band peak at about 328 nm and showed a blue emission band. The NUV‐blue emission band had a peak at about 386 nm with a band width of about 60 nm, attributed to the 5d–4f transition of Ce³⁺. Fluorescent decay showed an exponential model with a lifetime of 27.2 nsec. At 150°C, the luminescence intensity decreased to 68.7% compared with the intensity at room temperature.     

Long‐lived electrochemiluminescence of ruthenium (II) complexes/tri‐n‐propylamine in aqueous solutions

Although the clinical use of immunoassays based on the oxidative‐reduction electrochemiluminescence (ECL) of tris(2,2′‐bipyridine)ruthenium (II)/tri‐n‐propylamine has been a great success, elucidation of the ECL generation mechanism still remains unsatisfactory. We report here our experimental observations of long‐lived luminescence that remains detectable for several seconds after termination of electrochemical heterogeneous oxidation. Long‐lived luminescence was observed in both a surfactant‐free buffer and a surfactant‐containing broadly used commercial buffer under different conditions. The slow decay of emission seems to have been unnoticed in previous ECL mechanistic studies. Within the frame of the reaction schemes so far proposed, its origin is inconclusively ascribed to the reductive‐oxidation process of ruthenium (II) complex, that is Ru(bpy)₃²⁺ → Ru(bpy)₃¹⁺ → Ru(bpy)₃²⁺* → Ru(bpy)₃²⁺ with the involvement of the tri‐n‐propylamine‐derived radical cation. It is anticipated that long‐lived ECL will suggest a research approach to separate some homogeneous reactions from the complicated reaction system and therefore help to resolve the mechanistic mystery.     

Oxidation reactivity of zinc–cysteine clusters in metallothionein

Evaluating the reactivity of the metal–thiolate clusters in metallothionein (MT) is a key step in understanding the biological functions of this protein. The effects of the metal clustering and protein environment on the thiolate reactivity with hydrogen peroxide (H₂O₂) were investigated by performing quantum theory calculations with chemical accuracy at two levels of complexity. At the first level, the reactivity with H₂O₂ of a model system ([(Zn)₃(MeS)₉]^3?, MeS is methanethiolate) of the β domain cluster of MT was evaluated using density functional theory (DFT) with the mPW1PW91 functional. At the second level of complexity, the protein environment was included in the reactant system and the calculations were performed with the hybrid ONIOM method combining the DFT–mPW1PW91 and the semiempirical PM6 levels of theory. In these conditions, the energy barrier for the oxidation of the most reactive terminal thiolate was 21.5 kcal mol^?1. This is 3 kcal mol^?1 higher than that calculated for the terminal thiolate in the model system [(Zn)₃(MeS)₉]^3? and about 7 kcal mol^?1 higher than that obtained for the free thiolate. In spite of this rise of the energy barrier induced by the protein environment, the thiolate oxidation by H₂O₂ is confirmed as a possible way for metal release from MT. On the other hand, the results suggest that the antioxidant role of MT in the living cell cannot be as important as that of glutathione (which bears a free thiol).     

Induction of Metallothionein in Rat Liver by Zinc Exposure: A Dose and Time Dependent Study

Metallothioneins (MTs) are low molecular weight ubiquitous metalloproteins with high cysteine (thiol) content. The intracellular concentration of zinc (Zn) is tightly regulated and MT plays a crucial role in it. The present study investigates the relationship between the Zn status (as a function of Zn concentration and time) in the rat liver and the occurrence of hepatic MT. For dose dependent study, four experimental groups, one control and three receiving different levels of metal supplementation, were chosen [Group 1 control and Group 2, Group 3, Group 4 receiving subcutaneous dose of 10, 50 and 100 mg of Zn/kg body weight (in the form of ZnSO₄·7H₂O), respectively]. For the time dependent expression of MT, again four experimental groups, i.e. Group 5 control and Group 6, Group 7, Group 8 receiving 50 mg of Zn/kg body weight (in the form of ZnSO₄·7H₂O) subcutaneously and sacrificed at different time intervals after last injection i.e. 6, 18, 48 h, respectively were chosen. Isolation of MT was done by using combination of gel filtration and ion exchange chromatography while characterization of MT fraction was carried in the wavelength range 200–400 nm. Expression of MT was studied by using Western blot analysis. The results revealed that the MT expression increases with increasing the dose of Zn administered and maximum at 18 h after last Zn injection. Accumulation of MT with increase dose would help in maintaining the intracellular Zn concentration by its sequestration which further reduces the possibility of undesirable binding of Zn to other proteins significantly and maintains Zn homeostasis. The maximum expression of MT at 18 h is indicative of its half life.     

Dual emission fluorescent silver nanoclusters for sensitive detection of the biological coenzyme NAD+/NADH

Fluorescent silver nanoclusters (Ag NCs) displaying dual-excitation and dual-emission properties have been developed for the specific detection of NAD⁺ (nicotinamide adenine dinucleotide, oxidized form). With the increase of NAD⁺ concentrations, the longer wavelength emission (with the peak at 550 nm) was gradually quenched due to the strong interactions between the NAD⁺ and Ag NCs, whereas the shorter wavelength emission (peaking at 395 nm) was linearly enhanced. More important, the dual-emission intensity ratio (I₃₉₅/I₅₅₀), fitting by a single-exponential decay function, can efficiently detect various NAD⁺ levels from 100 to 4000 μM, as well as label NAD⁺/NADH (reduced form of NAD) ratios in the range of 1–50.     

Elongation of acyl-CoAs by microsomes from etiolated leek seedlings

Long chain fatty acid synthesis was studied using etiolated leek seedling microsomes. In the presence of ATP, [2-¹⁴C]malonyl-CoA was incorporated into fatty acids of C₁₆C₂₆. The omission of ATP, even in the presence of acetyl-CoA, led to a complete loss of activity, which was restored by addition of exogeneous acyl-CoAs. Comparison of acyl-CoA (C₁₂C₂₄) elongation showed that stearoyl-CoA, in the presence of [2-¹⁴C]malonyl-CoA, was the more efficient precursor leading to the formation of fatty acids having a chain length of C₂₀C₂₆. [1-¹⁴C]C₁₆CoA and [1-¹⁴C]C₁₈CoA were elongated in the presence of malonyl-CoA, without degradation of the acyl chain. The time-course and the malonyl-CoA concentration curves showed that [1-¹⁴C]C₁₈CoA was a better primer than [1-¹⁴C]C₁₆CoA. Acyl-CoA elongation was also studied over the concentration range 4.5–45 μM [1-¹⁴C]C₁₈CoA. Comparison of the radioactivity incorporated into the fatty acids formed using [2-¹⁴C]malonyl-CoA in the presence of C₁₈CoA, on the one hand, and [1-¹⁴C]C₁₈CoA in the presence of malonyl-CoA, on the other, demonstrated clearly that the acyl chain of the acyl-CoA was elongated by malonyl-CoA.     

Interaction of polyamine macrocycles with Zn(II) and ATP in aqueous solution. Binary and ternary systems. A potentiometric,NMR and fluorescence emission study

ATP binding to ligands L1 and L3 and to their Zn(II) complexes has been examined by means of potentiometric and ¹H and ³¹P NMR measurements in aqueous solution. Their coordination features have been compared to those of ligand L2 and its Zn(II) complex. In all the three cases, the Zn(II) complexes proved to be better receptors than free ligands, due to the synergetic action of metal ion and ammonium functions in ATP binding. Among the three complexes, Zn(II) complex with L1 shows the highest equilibrium constant, which can be ascribed to the fact that, being coordinated by the dipyridine nitrogens outside the macrocyclic cavity, it is less saturated by ligand donors. The ³¹P NMR investigation showed that the nucleotide interacts via the P_γ and P_β phosphate groups with both free ligands and complexes, while the ¹H spectra revealed that the binding is reinforced by the presence of π–π interactions. Photophysical studies showed that the fluorescence emission intensity of the Zn(II) complexes is enhanced upon interaction with ATP.     

Synthesis and luminescence properties of a novel blue emitting phosphor NaMgPO4:Eu2+

A novel blue‐emitting phosphor of Eu²⁺‐activated NaMgPO₄ was prepared by combustion‐assisted synthesis. Sodium dihydrogen phosphate and magnesium nitrate were used as the source of Na, P and Mg, respectively. The ratios of magnesium and phosphorus components that were dissolved into the combustion solution were changed from 1:1 to 1:1.3. Their effect on the crystallinities and photoluminescence spectra of the phosphor particles were investigated. The post‐heated phosphor particles had a broad excitation wavelength that ranged from 240 to 410 nm. The phosphor particles prepared from the combustion solution with a 1:1.2 ratio of magnesium to phosphorus had maximum emission intensity under ultraviolet excitation. The effect of doped Eu²⁺ concentration on the emission intensity of NaMgPO₄:Eu²⁺ was also investigated.     

Main group metal halide complexes with sterically hindered thioureas. IX. New complexes of selected post-transition metals and 1,3-dimethyl-2(3H)-imidazolethione and a structural investigation of infrared peak shifts associated with coordination

Five new complexes of sterically hindered 1,3- dimethyl-2(3H)-imidazolethione (dmit) with the chlorides of Cd(II), Hg(II), Te(II), Sn(IV) and Sb(V) have been synthesized and characterized. The previously reported Zn(II) adduct was also synthesized and further characterized. These complexes were of the general formula MX_n(dmit)_m where n = 2 and m = 2 when M = Zn, Cd, Hg and Sn; and n = 2 and m = 4 for Te(II). The only 1:1 adduct observed was SbCl₅dmit, and its chemistry is more complex giving rise to unique redox products upon heating in solution. Solid state spectra of these complexes as well as for dmit complexes are reported and discussed with regard to the coordination sensitive NCN asymmetric stretch and the CS stretch observed not only for dmit complexes but for tetramethylthiourea (tmtu) complexes reported in the literature as well. Greatest shifts on coordination are observed with the NCN asymmetric stretch for tmtu causing shifts to higher wave numbers ranging from 55 to 95 cm⁻¹ relative to free tmtu. Shifts are explained on the basis of observed crystal structures of tmtu adducts showing a greater CN double bond character. Dmit adducts show much smaller shifts both to higher and lower wave numbers for this mode relative to free ligand, and the CS stretch shows little change also. Comparison to known crystal structures show little change in the bond distances of the dmit ligand upon coordination. Inductive effects based on correlations of shift magnitude to the Sanderson group electronegativity (SGEN) of the acceptor seem to be unrelated with the exception of a small positive correlation observed for the NCN asymmetric stretch of tmtu.     

Fluorescence Decaying Kinetics and Photodamage of Quinone-Reconstituted D1/D2/Cytochrome b559 Complex

Photosystem Ⅱ reaction center D1/D2/Cytochrome b559 complex loses its bound secondary electron acceptor QA and QB during isolation and purification. The artificial plastoquinone can reconstitute with the complex. The reconstitution of decyl-plastoquinone (DPQ) with D1/D2/Cytochrome b559 complex results in a decrease of the fraction of the two long lived fluorescence decay components (24 ns and 73 ns) coupled with photochemical activities to the total fluorescence yields, as well as a decrease of the total fluorescence intensity and a blue-shift of maximum emission wavelength. These results suggest that as the electron acceptor of reduced Pheo, DPQ restricts the charge recombination of P680+ Pheo-, and the two long lived fluorescence decay components (24 ns and 73 ns) come from the recombination. Although DPQ reconstitution has little effect on the susceptibility of Chi a to photodamage, β-carotene can easily be photodamaged after DPQ reconstitution. This is probably related to the physiological function of β-carotene.     

The crystal and molecular structures of dioxo mo(VI) complexes of tripodal,tetradentate N,S-donor ligands

The crystal and molecular structures of the complexes MoO₂((SCH₂CH₂)₂NCH₂CH₂SCH₃), I and MoO₂((SCH₂CH₂)₂NCH₂CH₂N(CH₃)₂), II, have been determined from X-ray intensity data collected by counter methods. Compound I crystallizes in two forms, Ia and Ib. In form Ia the space group is P2₁/n with cell parameters a = 7.235(2), b = 7.717(2), c = 24.527(6) Å, β = 119.86(2)°, V = 1188(1) ų, Z = 4. In form Ib the space group is P2₁/c with cell parameters a = 14.945(5), b = 11.925(5), c = 14.878(4) Å, β = 114.51(2)°, V = 2413(3) ų, Z = 8. The molecules of I in Ia and Ib are very similar having an octahedral structure with cis oxo groups, trans thiolates (cis to both oxo groups) and N and thioether sulfur atoms trans to oxo groups. Average ditances are MoO = 1.70, MoS (thiolate) = 2.40, MoN = 2.40 and MoS (thioether) = 2.79 Å. Molecule II crystallizes in space group P2₁2₁2₁ with a = 7.188(1), b = 22.708(8), c = 7.746(2) Å, V = 1246(1) ų and Z = 4. The coordination about Mo is octahedral with cis oxo groups, trans thiolates and N atoms trans to oxo. Distances in the first coordination sphere are MoO = 1.705(2), 1.699(2), MoS = 2.420(1), 2.409(1) and MoN = 2.372(2), 2.510(2) Å. The conformational features of the complexes are discussed. Complex I displays MoO and MoS distances which are very similar to those found by EXAFS in sulfite oxidase. This similarity is discussed.     

31P n.m.r. studies of complexes of NADPH and NADP+ with Escherichia coli dihydrofolate reductase

We have measured the ³¹P n.m.r. spectra of NADP⁺ and NADPH in their binary complexes with Escherichia coli dihydrofolate reductase and in ternary complexes with the enzyme and folate or methotrexate. The ³¹P chemical shift of the 2′ phosphate group is the same in all complexes; its value indicates that it is binding in the dianionic state and its pH independence suggests that it is interacting strongly with cationic residue(s) on the enzyme. Similar behaviour has been noted previously for the complexes with the Lactobacillus casei enzyme although the ³¹P shift is somewhat different in this complex, possibly due to an interaction between the 2′ phosphate group and His 64 which is not conserved in the E. coli enzyme. For the coenzyme complexes with both enzymes ³¹POC₂¹H_2′ spin-spin interactions were detected (7.5–7.8 Hz) on the 2′ phosphate resonances, indicating a POC₂H_2′ dihedral angle of 30 or 330 : this is in good agreement with the value of 330° measured in crystallographic studies¹ (Matthews et al., 1978) on the L. casei enzyme. NADPH-MTX complex. The pyrophosphate resonances are shifted to different extents in the various complexes and there is evidence that there is more OPO bond angle distortion in the E. coli enzyme complexes than in those with the L. casei enzyme. The effects of ³¹POC₅¹H_5′ spin coupling were detected on one pyrophosphate resonance and indicate that the POC₅H_5′ torsion angle has changed by at least ～30° on binding to the E. coli enzyme: this is considerably less than the distortion (～50°) observed previously in the L. casei enzyme complex.     

Preparation,structure and properties of dicyano silver complexes of the M(en)3Ag2(CN)4 and M(en)2Ag2(CN)4 type

Complexes of the M(en)₃Ag₂(CN)₄ (M = Ni, Zn, Cd) and M(en)₂Ag₂(CN)₄ (M = Ni, Cu, Zn, Cd) type were prepared and identified by elemental analysis, infrared spectroscopy, measurement of magnetic susceptibility, and X-ray powder diffractometry. The crystal structures of Ni(en)₃Ag₂(CN)₄ (I) and Zn(en)₂Ag₂(CN)₄ (II) were determined by the method of monocrystal structure analysis. Complex I crystallizes in the space group C2/c, a = 1.2639(5), b = 1.3739(4), c = 1.2494(4) nm, β = 113.25(4)°, D_m = 1.86(1), D_c = 1.86 gcm⁻³ Z = 4, R = 0.0429. The crystal structure of I consists of complex cations [Ni(en)₃]²⁺ and complex anions [Ag(CN)₂]⁻. Complex II crystallizes in the space group I2/m, a = 0.9150(3), b = 1.3308(4), c = 0.6442(2) nm, β = 95.80(3)°, D_m = 2.14(1), D_c = 2.15 gcm⁻³, Z = 2, R = 0.0334. Its crystal structure consists of infinite, positively charged chains of the [-NCAgCNZn- (en)₂]_nⁿ⁺ type and isolated [Ag(CN)₂]⁻ anions. The atoms of Ag are positioned parallely to the z axis and the AgAg distance is equal to 0.3221(2) nm.