Intra-hydrogen Bonds Research Articles

Novel dinuclear open paddle-wheel-like copper complexes involving π-stacking on the basis of chiral binaphthyl phosphoric acid {(R)-PhosH}: structural, magnetic and optical properties.

This research embarked on the study of a new binaphthyl phosphate scaffold of copper. There are two independent neutral complexes in the asymmetric unit: Cu1/Cu2 (I) and Cu3/Cu4 (II) from a similar structure topaddle-wheel-like, with one arm formed by an intra-hydrogen bond between the water molecule bonded to the copper and the phosphine oxide (PO) moieties. Moreover, in the first complex two water and one ketone molecule complete the coordination sphere of the two-copper metals, instead, in the second one, one water and two ketone molecules. The experimental value obtained for the effective paramagnetic moment indicates that there is no appreciable interaction between the copper(II) cations and that they behave as paramagnetic ions over the entire temperature range explored (5-350 K).

Deciphering the intrinsic dynamics of unphosphorylated IRAK4 kinase bound to type I and type II inhibitors

Interleukin-1 receptor-associated kinase 4 (IRAK4) is a vital protein involved in Toll-like and interleukin-1 receptor signal transduction. Several studies have reported regarding the crystal structure, dynamic properties, and interactions with inhibitors of the phosphorylated form of IRAK4. However, no dynamic properties of inhibitor-bound unphosphorylated IRAK4 have been previously studied. Herein, we report the intrinsic dynamics of unphosphorylated IRAK4 (uIRAK4) bound to type I and type II inhibitors. The corresponding apo and inhibitor-bound forms of uIRAK4 were subjected to three independent simulations of 500 ns (total 1.5 μs) each, and their trajectories were analyzed. The results indicated that all three systems were relatively stable, except for the type II inhibitor-bound form of uIRAK4, which exhibited less compact folding and higher solvent surface area. The intra-hydrogen bonds corroborated the structural deformation of the type-II inhibitor-bound complex, which could be attributed to the long molecular structure of the type-II inhibitor. Moreover, the type II inhibitor bound to uIRAK4 showed higher binding free energy with uIRAK4 than the type I inhibitor. The free energy landscape analysis showed a reorientation of Phe330 side chain from the DFG motif at different metastable states for all the systems. The intra-residual distance between residues Lys213, Glu233, Tyr262, and Phe330 suggests a functional interplay when the inhibitors are bound to uIRAK4, thereby hinting at their crucial role in the inhibition mechanism. Ultimately, the intrinsic dynamics study observed between type I/II inhibitor-bound forms of uIRAK4 may assist in better understanding the enzyme and designing therapeutic compounds.

Regeneration Approach to Enhance the Antimicrobial and Antioxidant Activities of Chitosan for Biomedical Applications

Owing to its biodegradability, non-toxicity, and biocompatibility, chitosan (Cs) is a ubiquitous biopolymer. However, applications of Cs are limited owing to the existence of strong inter- and intra-molecular hydrogen bonds within its network. To address this issue, we regenerated medium-molecular-weight Cs to enhance the physico-chemical and functional properties using a cationic approach. Accordingly, alkaline modification was employed to introduce an additional positive charge to the amine functional groups of Cs and moderately disintegrate the inter- and intra-hydrogen bonds. The chemical structure of Cs and regenerated chitosan (RCs) was confirmed through Fourier transform infrared and 1H-NMR spectroscopy. RCs showed higher zeta potential value compared to Cs. Additionally, using X-ray diffraction, RCs exhibited low crystallinity, which can be attributed to the repulsive force caused by the positive surface charge and the destruction of hydrogen bonds. The RCs exhibited stronger antioxidant activity than Cs. Furthermore, the minimum inhibition concentrations (MICs) of RCs against Escherichia coli and Staphylococcus aureus were reduced by almost four times compared with those of Cs. The superior functional properties of RCs can be attributed to the formation of a polycationic structure after alkaline modification. Thus, RCs can be introduced as potent agents for various biomedical purposes.

Acidic pH Promotes Refolding and Macroscopic Assembly of Amyloid β (16-22) Peptides at the Air-Water Interface.

Assembly by amyloid-beta (Aβ) peptides is vital for various neurodegenerative diseases. The process can be accelerated by hydrophobic interfaces such as the cell membrane interface and the air–water interface. Elucidating the assembly mechanism for Aβ peptides at hydrophobic interface requires knowledge of the microscopic structure of interfacial peptides. Here we combine scanning force microscopy, sum-frequency generation spectroscopy, and metadynamics simulations to probe the structure of the central fragment of Aβ peptides at the air–water interface. We find that the structure of interfacial peptides depends on pH: at neutral pH, the peptides adopt a less folded, bending motif by forming intra-hydrogen bonds; at acidic pH, the peptides refold into extended β-strand fibril conformation, which further promotes their macroscopic assembly. The conformational transition of interfacial peptides is driven by the reduced hydrogen bonds, both with water and within peptides, resulting from the protonation of acidic glutamic acid side chains.

N-Vinyl Caprolactam/Maleic-Based Copolymers as Kinetic Hydrate Inhibitors: The Effect of Internal Hydrogen Bonding

Kinetic hydrate inhibitors (KHIs) have been used for over 25 years to prevent gas hydrate formation in oil and gas production flow lines, but they are some of the most expensive oilfield production chemicals. The main component in KHI formulations is a water-soluble polymer with many amphiphilic groups. Usually, in commercial KHI polymers, the hydrophilic part of these groups is the amide group. In addition, KHI polymers are often incompatible with film-forming corrosion inhibitors. Therefore, we sought to find cheaper but effective KHIs that could also act as a flow line corrosion inhibitor. Continuing earlier work from our group with maleic-based polymers, we have now explored maleic acid/N-vinyl caprolactam (MAcid/VCap) copolymers to introduce VCap, a well-known KHI monomer, together with the cheaper MA monomer. KHI performance screening tests were conducted under high pressure with a structure II-forming natural gas mixture in steel rocking cells using the slow (1 °C/h) constant-cooling test method. Surprisingly, the MAcid/VCap copolymer showed very poor KHI efficacy. GFN2-xTB molecular dynamics simulations revealed that MAcid/VCap exhibits intra-hydrogen bond networks that trap the polymer morphology in the globular form. In this scenario, the caprolactam ring is encapsulated inside the polymer structure due to the intra-hydrogen bonds and the hydrophobic interactions that minimize its ability to interact with the hydrate surfaces, which significantly reduces the MAcid/VCap kinetic inhibition performance. However, the polymer in such globular forms still displays an important amount of its carboxylic groups exposed to water, which explains the water solubility. In contrast to MAcid/VCap copolymers, maleimide derivatives with dibutylamino end groups were effective KHIs and even better with dibutylamine oxide end groups. A terpolymer of MA/VCap reacted with N,N-dibutylaminopropylamine followed by subsequent oxidation of the end groups to dibutylamine oxide and gave the best performance of any maleic-based polymer reported to date. The combination of caprolactam and dibutylamine oxide groups can be thought of as synergism within the same polymer, akin to the excellent synergy of the separate molecules, tributylamine oxide and PVCap.

Electrochemical One-Step Immunoassay Based on Switching Peptides and Pyrolyzed Carbon Electrodes.

Switching peptides were designed to bind reversibly to the binding pocket of antibodies (IgG) by interacting with frame regions (FRs). These peptides can be quantitatively released when antigens bind to IgG. As FRs have conserved amino acid sequences, switching peptides can be used as antibodies for different antigens and different source animals. In this study, an electrochemical one-step immunoassay was conducted using switching peptides labeled with ferrocene for the quantitative measurement of analytes. For the effective amperometry of the switching peptides labeled with ferrocene, a pyrolyzed carbon electrode was prepared by pyrolysis of the parylene-C film. The feasibility of the pyrolyzed carbon electrode for the electrochemical one-step immunoassay was determined by analyzing its electrochemical properties, such as its low double-layer capacitance (Cdl), high electron transfer rate (kapp), and wide electrochemical window. In addition, the factors influencing the amperometry of switching peptides labeled with ferrocene were analyzed according to the hydrodynamic radius, the number of intrahydrogen bonds, dipole moments, and diffusion coefficients. Finally, the applicability of the electrochemical one-step immunoassay for the medical diagnosis of the human hepatitis B surface antigen (hHBsAg) was assessed.

Revealing the mechanism beneath the effects of starch-amino acids interactions on starch physicochemical properties by molecular dynamic simulations

In this study, the effects of different amino acids (AAs) including glycine (Gly), lysine (Lys) and glutamic acid (Glu) on starch physicochemical (gelatinization, swelling capacity, pasting and retrogradation) and morphological characteristics were investigated using differential scanning calorimeter, rapid visco analyser, a novel automatic segmentation methodology, along with both SEM and polarization microscope under normal and polarized light. Results showed that at a concentration of 3% (w/w), the addition of AAs showed no or only limited effects on starch granular morphological properties and crystallinity. Nevertheless, AAs could significantly inhibit starch granular swelling and gelatinization during heating, especially for charged AAs including Glu and Lys, leading to lower swelling capacity but higher gelatinization temperatures (p < 0.05). Moreover, the starch-AAs interactions also significantly decreased the starch viscosities including peak, trough, final and the setback viscosities, through retarding the leaching of starch molecules from inside. The molecular dynamics simulation further reveals that compared with water molecules, in an order of Glu > Lys > Gly, the interactions between AAs and water significantly decreased the number of starch-water hydrogen bonds, maintaining a higher number of starch-starch intra hydrogen bonds. This in turn improved the intra-hydrogen bonds within starch chains, resulting to more stable structures and thus inhibited starch gelatinization as well as its swell capacity. This study provides important information in terms of the application of different of AAs on starch aiming to improve starch physicochemical properties for better food processing and better starch functional properties.

Computational Insights into the Structural Dynamics of MDA5 Variants Associated with Aicardi-Goutières Syndrome and Singleton-Merten Syndrome.

Melanoma differentiation-associated protein 5 (MDA5) is a crucial RIG-I-like receptor RNA helicase enzyme encoded by IFIH1 in humans. Single nucleotide polymorphisms in the IFIH1 results in fatal genetic disorders such as Aicardi–Goutières syndrome and Singleton–Merten syndrome, and in increased risk of type I diabetes in humans. In this study, we chose four different amino acid substitutions of the MDA5 protein responsible for genetic disorders: MDA5L372F, MDA5A452T, MDA5R779H, and MDA5R822Q and analyzed their structural and functional relationships using molecular dynamic simulations. Our results suggest that the mutated complexes are relatively more stable than the wild-type MDA5. The radius of gyration, interaction energies, and intra-hydrogen bond analysis indicated the stability of mutated complexes over the wild type, especially MDA5L372F and MDA5R822Q. The dominant motions exhibited by the wild-type and mutant complexes varied significantly. Moreover, the betweenness centrality of the wild-type and mutant complexes showed shared residues for intra-signal propagation. The observed results indicate that the mutations lead to a gain of function, as reported in previous studies, due to increased interaction energies and stability between RNA and MDA5 in mutated complexes. These findings are expected to deepen our understanding of MDA5 variants and may assist in the development of relevant therapeutics against the disorders.

Thermal Stability and Compression Strength of Rigid Polyurethane/Kenaf Fibre Biocomposite Foam

Rigid palm oil-based polyurethane/kenaf fibre biocomposite foams were prepared at various amounts of kenaf fibre (i.e. 2.5, 5.0, 7.5, 10.0 and 12.5 pphp). Effects of kenaf fibre (KF) loadings on thermal stabilities and compressive strength were investigated. The peaks detected by Fourier transform infrared (FTIR) at 3,310 cm-1 (OH stretching), 1,533 cm-1 (NH bending) and 1,510 cm-1 (CN stretching) had proved the formation of urethane linkages in the system. Results from thermogravimetric analysis (TGA) showed that the thermal stabilities of biocomposite foams were higher than that of control PU foam. Higher KF contents resulted in agglomeration of which reduced the rate of heat transfer throughout the system. The presence of intra-hydrogen bonds in agglomerated KF caused more heat needs to break the bonds, thus increasing the thermal stabilities. Consequently, the agglomeration of KF created stress concentration, which reduced the compression strength of the foams with respect to the control PU foam. The presence of intra-hydrogen bonding in PU chains had surpassed the agglomeration effect, thus causing just a small reduction percentage. The foams have potentials to be used in non-load bearing applications such as insulators and wall panels.

Effect of Plasticizer on the Morphology and Foaming Properties of Poly(vinyl alcohol) Foams by Supercritical CO2 Foaming Agents

As an environment-friendly polymer, polyvinyl alcohol (PVA) foams have attracted increasing attention due to their excellent thermal insulation and cushioning properties. However, the main drawback of PVA is its difficulty in melt processing (due to strong inter-/intrahydrogen bonds) and to control the cell morphology. To overcome the processing limits and realize the control of cell morphology, environmentally friendly PVA microcellular foams were prepared by two-step foaming method, using ethylene glycol (EG) as a plasticizer and supercritical carbon dioxide (Sc-CO2) as foaming agent. The melting behavior and rheological properties of plasticized PVA foams were investigated by differential scanning calorimetry (DSC) and rheometer. The effect of EG content on cell morphology was studied by scanning electron microscopy (SEM). It was demonstrated that EG plasticizer exhibited good plasticizing effect, which decreased the melting point and widened the processing window of PVA. Moreover, the plasticizer could affect the melt strength and crystallization of samples, thus, affecting the foaming process and the cell morphology. The foaming effect of PVA foams was obviously improved after adding plasticizer. With the increase of plasticizer content, the cell size of the foam increased from 9.30 μm (10 phr) to 12.75 μm (30 phr), and the expansion ratio increased from 2.33 (10 phr) to 3.36 (30 phr). This work has reference significance for the study of the regulation of cell morphology in the subsequent polymer foaming process.

Correlation between single crystal data and molecular mechanics calculation of 3-(2-hydroxy-phenylimino)-1,3-diphenyl-propan-1-one

The Schiff base 3-(2-hydroxy-phenylimino)-1,3-diphenyl-propan-1-one (L), was prepared and characterized by elemental analysis, IR, 1H NMR and mass spectral techniques. The crystal and molecular structures were determined by using the single crystal X-ray diffraction data. The crystal was triclinic with unit-cell dimensions: a = 9.051(3) Å, b = 10.245(3) Å, c = 11.016(3) Å, α = 69.28(2)°, β = 81.66(2)°, γ = 64.25(2)°, space group is Pī and Z = 2. The structure was refined by least squares method. The single crystal was prepared by supersaturating method using tetramethoxysilane as gelling agent. Energy minimization for locating stable conformations and single point energy calculations for comparing the obtained and calculated conformations of the same molecule were carried out using molecular mechanics method (MM2 force field). The bond lengths and the bond angles were calculated and compared with the values obtained from the single crystal analysis. The obtained results were discussed and evaluated. Generally, the calculated parameters are in good agreement with the corresponding X-ray diffraction values. The obtained results reveal that, the amine-imine tautomerism is more preferable than keto-enol form and the intra-hydrogen bond stabilize the amine-imine tautomerism.

Tyrosine nitration of human ERK1 introduces an intra-hydrogen bond by molecular dynamics simulations

ERK1 is an important kinase in Ras–Raf–MEK signaling. We have recently demonstrated by mass spectrometry that Tyr210 of ERK1 can be nitrated, and the nitration leads to a novel CHIP–dependent ERK1 degradation pathway. This motivated us to investigate the effect of this nitration on local and global structures of human ERK1 by Gaussian calculations and molecular dynamics simulations. Our study shows that the nitration at either the CE1 or the CE2 positions introduces an intra-hydrogen bond between the hydroxyl group and the nitro group of the nitrated Tyr210 of ERK1. Our data indicate that the hydrogen bond between Tyr210 and Glu237 is not stable and the nitration of Tyr210 facilitates its breakage. The previous studies demonstrated that ERK1 can be autophosphorylated at tyrosine residue 204. We next studied the effect of the phosphorylation in combination with the nitration. We found that the nitration of Tyr210 modestly decreases its inter-residue electrostatic interactions, and the phosphorylation of Tyr204 increases its inter-residue electrostatic interactions as expected. In the active state of ERK1, the conserved Lys71 forms a salt bridge with the conserved Glu88 and this salt bridge is essential for the activity of ERK1. Our data demonstrate an additional salt bridge for Glu88 with Arg84, and this salt bridge is unphosphorylation-dependent. The phosphorylation of ERK1 with the nitration at CE2, not at CE1, slightly enhances the K71–E88 salt bridge. Collectively, our simulations have demonstrated formation of a tyrosine nitration–dependent hydrogen bond. Our molecular dynamics simulations in combination with the experimental data on the nitration of Tyr210 of ERK1 indicate that a post-translational modification of a protein can specifically alter local structural environments, and a local structural change could lead to changes of protein functions.

Spectroscopic properties and molecular structure of copper phytate complexes: IR, Raman, UV\u2013Vis, EPR studies and DFT calculations

The copper phytate IP6Cu, IP6Cu2 and IP6Cu3 complexes were synthesized changing the phytate to metal mole ratio. The obtained products have been characterized by means of chemical and spectroscopic studies. Spectroscopic ATR/IR, FT-Raman, UV–Vis, EPR and magnetic measurements were carried out. The structures of these compounds have been proposed on the basis of the group theory and geometry optimization taking into account the shape and number of the bands corresponding to the stretching and bending vibrations of the phosphate group and metal–oxygen polyhedron. The role of the inter- and intra-hydrogen bonds in stabilization of the structure has been discussed. EPR studies showed that a local rhombic symmetry of copper ions appears in the studied phytates. Dominant interactions show antiferromagnetic properties depending on the content of paramagnetic ions.

Syntheses, spectroscopic properties and molecular structure of silver phytate complexes - IR, UV-VIS studies and DFT calculations

Silver phytate IP6, IP6Ag, IP6Ag2 and IP6Ag3 complexes in the solid state have been synthesized changing the phosphate to metal mole ratio. The obtained products have been characterized by means of chemical and spectroscopic studies. Attenuated total reflection Fourier transform infrared technique and Raman microscope were used in the measurements. These results were discussed in terms of DFT (Density Functional Theory) quantum chemical calculations using the B3LYP/6-31G(d,p) approach. The molecular structures of these compounds have been proposed on the basis of group theory and geometry optimization taking into account the shape and the number of the observed bands corresponding to the stretching and bending vibrations of the phosphate group and metal-oxygen polyhedron. The role of inter- and intra-hydrogen bonds in stabilization of the structure has been discussed. It was found that three types of hydrogen bonds appear in the studied compounds: terminal, and those engaged in the inter- and intra-molecular interactions. The Fermi resonance as a result of the strong intra-molecular OH⋯O hydrogen bonds was discovered. Electron absorption spectra have been measured to characterize the electron properties of the studied complexes and their local symmetry.

Living Supramolecular Compounds: Influence of Multiple Hydrogen Bond Connection on Molecular Configuration of Monophosphate or Pyrophosphate Thiamine with Anions or Coordination Anions

AbstractThree supramolecular compounds with monophosphate or pyrophosphate esters of thiamine, namely, [TPPH+·CF3SO3·H2O] (1), [TMPH+·(CdCl4)0.5·2H2O] (2), and [TMPH+·NO3·2.5H2O] (3) (TPP = thiamine pyrophosphate, TMP = thiamine monophosphate) were synthesized in methanol or water systems at room temperature. They were characterized by elemental analysis, IR spectrocopy, and single X‐ray diffraction. Structural analysis shows that they are all supramolecular compounds and there are abundant interhydrogen and intrahydrogen bonds in the molecules. In addition, combined with the quantum mechanical calculations, their potential reaction activity and molecular electronic configuration were discussed.

Long-acting GLP-1 analogue in V-shaped conformation by terminal polylysine modifications.

Glucagon-like peptide-1 (GLP-1) possesses multiple physiological functions, which make it a potential drug candidate for the treatment of type 2 diabetes. However, its clinical application was limited severely by its short half-life in vivo. Therefore, stabilization of GLP-1 is critical for the use of this peptide in drug development. In this study, a novel GLP-1 derivative, VGLP1K6, processed a significantly prolonged half-life in vivo. Structural analysis using molecular dynamics simulations demonstrated that VGLP1K6 has a rigid V-shaped conformation resulting from the intrapeptide disulfide bond. The C-terminal polylysine residues of VGLP1K6 caused the vulnerable N-terminus of GLP-1 (HA-fragment) to reside within the pocket-like cavity of the peptide due to the intrahydrogen bonds. The structural analysis suggested that this structural alteration contributed to the remarkable prolonged half-life of VGLP1K6, which was approximately 70 h. In addition, VGLP1K6 induced better long-acting glucose tolerance and greater HbA1c reductions than GLP-1 in rodents. Our findings suggest that the GLP-1 derivative VGLP1K6 might be a possible potent antidiabetic drug for the treatment of type 2 diabetes mellitus.

SYNTHESIS, CHARACTERIZATION AND CRYSTAL STRUCTURE OF 3'-[(4-FLUOROPHENYL)CARBONYL]-5'-(HYDROXYMETHYL)-4’-PHENYL SPIRO[INDOLE-3,2'-PYRROLIDIN]-2(1H)-ONE

The title compound 3'-[(4-fluorophenyl)carbonyl]-5'-(hydroxymethyl)-4’-phenyl spiro[indole-3,2'-pyrrolidin]-2(1 H )-one is synthesized by the straightforward multicomponent reaction of 1-(4-fluorophenyl)-3-phenylprop-2-en-1-one, isatin and serine, and is crystallises in monoclinic space group C2/c.The molecule is essentially planar except one of the pyrrolidin ring which adopts normal envelope conformation. The supermoleular assembly is consolidated by ᴨ-ᴨ interactions [centroid- centroid distance= 3.7983(18)]. The crystal structure is stabilized by one C-H…O intra-hydrogen bond, two N-H…O and one O-H…N inter-hydrogen bonds, and these interactions links the molecules into chain extending along the b-axis.

Structure and Kinetics of Hydrogen Bonds in Aqueous Glucose Solutions

Hydrogen bonding structure and kinetics in aqueous glucose solutions with different concentrations were studied using the molecular dynamics simulation method. The percentage distributions of glucose and water molecules with i hydrogen bonds (intra, inter, or both) were analyzed. We find that a critical number N exists and the percentage of glucose or water molecules with N hydrogen bonds is the highest. When iN, the percentage of glucose or water molecules with i hydrogen bonds increases as the glucose concentration increases, while when iN the percentage of glucose or water molecules with i hydrogen bonds decreases as the glucose concentration increases. Continuous and intermittent autocorrelation functions for the different hydrogen bonds (intra-hydrogen bonds in the glucose molecules, hydrogen bonds between glucose molecules, hydrogen bonds between the water molecules, hydrogen bonds between the glucose and water molecules, and all hydrogen bonds) and the hydrogen bond lifetimes were also calculated.

Effects of a pretreatment with N‐methylmorpholine‐N‐oxide on the structures and properties of ramie

AbstractTo improve the dyeing properties of ramie, the ecofriendly organic solvent N‐methylmorpholine‐N‐oxide (NMMO) was used to substitute sodium hydroxide as a ramie‐fiber swelling solvent. Through padding and baking pretreatment, ramie fabric was modified by an NMMO aqueous solution. Ultraviolet–visible spectrophotometry, Fourier transform infrared spectroscopy, X‐ray diffraction, and differential scanning calorimetry were used to investigate the effects of NMMO pretreatment on the structure of the ramie, whereas the color strength (K/S, where K is the light absorption coefficient and S is the scattering coefficient), adsorption isotherm, and dye uptake rate curve were measured to investigate the effects of NMMO pretreatment on the dyeing properties of the ramie. The results show that the ramie fiber experienced a limited and irreversible swelling because of the partial breakage of interhydrogen and intrahydrogen bonds of cellulose molecules in the amorphous area, but the crystal and chemical structure of the ramie fiber did not change obviously under the experimental conditions. The K/S value of the NMMO‐modified ramie fabrics dyed with reactive dyes increased by about 100%, and the dye uptake increased by 27.88% compared to that of the raw sample, whereas the standard affinity and diffusion coefficient value of the reactive dyes on the NMMO‐modified ramie fabric were higher than those of the raw ramie fabric. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Crystal structure of cis-dichloro-1,2-ethylenediamine-bis(1,4- (diphenylphosphino)butane)-ruthenium(II) dichloromethane disolvate, RuCl2(C2H8N2)(C28H28P2) · 2CH2Cl2

C32H40Cl6N2P2Ru, triclinic, P1 (no. 2), a = 10.338(6) A, b = 13.024(5) A, c = 14.491(5) A, = 81.02(2)°, = 87.65(3)°, = 66.95(3)°, V = 1772.9 A, Z = 2, Rgt(F) = 0.028, wRref(F) = 0.075, T = 173 K. Source of material All the reactions were performed using Schlenk-type flask under argon and standard high vacuum-line techniques. Solvents were of analytical grade and distilled under argon. The title compound was prepared starting from trans-RuCl2(dppb)2. Mixing of ethylenediamine (0.012 g, 0.200 mmol) in dichloromethane (10 ml) dropwise with cis-[RuCl2(dppb)en] (0.200 g, 0.195 mmol) dissolved in the same solvent (15 ml). The reaction mixture was stirred at room temperature for 2 h. The solvent was removed in vacuo, the residuewaswashedwellwith hexane then diethylether and dried, to give yellow powder. The crystals were grown by slow diffusion of diethylether into a solution of the complex in dichloromethane. NMR, IR, and FAB-mass spectroscopy data are available in the CIF. Elemental analysis – found: C, 54.57 %; H, 5.26 %; Cl, 10.84 %; N, 4.19 %; calc. for C30H36Cl2N2P2Ru: C, 54.71 %; H, 5.51 %; Cl, 10.77 %; N, 4.25 %. Discussion The synthesis and chemistry of Ru(II) complexes possessing a chelating, ditertiary phosphine (P-P) and diamine (N-N) ligands remains a topic of interest, themain impetus being the potential of such complexes as catalysts [1-5]. Recently ruthenium homogenous hydrogenation catalysts have been proven to be some of most useful catalytic hydrogenation of polar double bonds such as C=O or C=N due to their favorable reactivity and selectivity [3-6]. The use of chiral Ru(II)(P-P)*(N-N)* complexes for asymmetric catalysis have been tremendously successful, especially in enantioselective hydrogenation of functionalized carbonyl compounds [2,5-8], and there has been much interest in the chemistry of Ru(II) complexes bearing chiral diphosphine ligands such as BINAP [9]. Such complexes proved to be excellent catalysts in the hydrogenation of functionalized carbonyl compounds under mild condition [2-11]. The title complex [RuCl2(dppb)en] crystallizes with two CH2Cl2 solvated molecules in full cis form with lost of the C2 symmetry. The cis-[RuCl2(dppb)en] thermodynamical isomer is structurally favored over the trans-[RuCl2(dppb)en] kinetic isomer [4,11,12], while the opposite was observed in solution and some solid state studies [3,6-8,13]. The rutheniumcenter is in a distorted octahedral environment with a five-membered diamine ring coordinating in cis form via N1 and N2, a seven-membered bis(phosphine) ring coordinating in cis form via P1 and P2 as well as cis-dichloro coordination. The bis(phosphine) ring allows for P–Ru–P angle to be larger than the ideal value of 94.13°, the smaller 1,2-diamine enforces N–Ru–N angle that is 10.85° less than the ideal value, while the Cl–Ru–Clwas found to be 89.61°which is very close to the ideal value. The Ru—N1 distance trans to Cl1 is shorter than the Ru—N2 distance trans to P2, 2.1213A and 2.1825A, respectively. The Ru—P1 distance trans to Cl2 slightly shorter than Ru—P2 distance trans to N2, 2.266 A and 2.278 A, respectively. The Ru—Cl1 distance trans to N1 is slightly shorter than the Ru—Cl2 distance trans to P1 by 0.034A, and found to be 2.489A and 2.455A, respectively. In the crystal structure there are a number of RuCl···H2N contacts smaller than 3.0 A, indicating the presence of unconventional intra-hydrogen bonds [7,13]. Z. Kristallogr. NCS 222 (2007) 1 © by Oldenbourg Wissenschaftsverlag, Munchen