Synthetic and theoretical study on novel N-ylidic complexes of mercury as new antibacterial agents.

The novel structure of Hg(II) complexes including the pyridinium ylide C5H5NCHC(O)C6H4-m-Br (Y) were synthesized and reported in this study. In the first step, the pyridinium salt C5H5NCH2C(O)C6H4-m-Br (S) was produced by reacting 2,3'-dibromoactophenone and pyridine. then, treatment of S with K2CO3 gave the related pyridinium ylide Y. Finally, the reaction of Y with HgX2 and Hg(NO3)2·H2O leads to the formation of novel binuclear [HgY2][HgX4] (X=Cl (1); X=Br (2); X=I (3)) and polymeric [HgY(NO3)2]n (4) complexes. The structure of complex 2 was also determined by X-ray diffraction analysis. The obtained analyses proved the coordination through the ylidic carbon to metallic center. Additionally, Natural Bond Orbital (NBO), Energy Decomposition Analysis (EDA), and EDA-NOCV studies are also used to investigate the nature of metal-ligand bonding in the complexes. Finally, the antibacterial activity of 1-4 was also examined against Gram positive and negative represented significant levels of inhibitory potency respected to used standards.

Nature of Metal-Drug Bond in Some Antitumor Active Complexes of Coinage Metal Ions.

N-Heterocyclic carbene and phosphine can be labeled as solid σ-donor ligands and can contribute to stable complexes. In addition, the constructed complex can accommodate a wide variety of applications, such as pharmaceutical products. In the light of this, a theoretical analysis was carried out on the existence of metal-drug interactions of group 11 metal ions in coordination with symmetrical unsaturated N-heterocyclic carbenes [NHC(R)(R')] and monodentate phosphine (PR3). The R substitutes on N atoms in NHC and phosphines are identical, and R' substitutes are located on two noncarbenic carbon atoms (C4 and C5) in the heterocycle complexes. All complexes are in general formula, [Tgt → ML] {where M = Cu(I), Ag(I), Au(I), Tgt = 2,3,4,6-tetra-O-acetyl-1-thio-ß-d-glucopyranoside, L= [NHC(R)(R')], and PR3; R = F, Cl, Br, H, CH3, C2H5, SiH3, 2,6-diisopropylphenyl; R' = H and Ph} at the PBE-D3/def2-TZVP level of theory. Findings show greater tolerance for the release of drugs in the presence of Ag(I) metal ions than the other metal ions studied here. Applying natural bond orbital (NBO), atoms in molecules (AIMs), energy decomposition analysis (EDA), and extended transition-state natural orbital for chemical valence (ETS-NOCV) analysis have been researched in order to ascertain the nature of M ← S and M ← C (M ← P) bonds in the complexes. Results have shown that σ donation from S to M atoms in [Tgt → MPR3] complexes is better and the π acceptor is weaker than the corresponding [Tgt → MNHC(R)(R')] complexes.

Toward prediction of the precatalyst activation mechanism through the cross-coupling reactions: Reduction of Pd(II) to Pd(0) in precatalyst of the type Pd-PEPPSI.

Pd-PEPPSI type complexes are widely used as precatalyst in a variety of organic reactions, including the Negishi, Kumada and Suzuki-Miyaura cross-coupling reactions. The aim of this research is to determine potential proposed reaction pathways 1, 2, or 2' (See Schemes 1 and S1-S4) for Pd-PEPPSI precatalyst activation in the presence of ethylene glycol as a solvent also in the gas phase at Cam-B3LYP-D3 method nominated among eight DFT methods examined. There is also investigation into the impact of promoter bases (NaOEt, NaOi Pr, NaOt Bu) on precatalyst activation of Pd-PEPPSI. Eventually, the most favorable proposed reaction pathway and promoter base for reducing Pd(II) to Pd(0) are predicted computationally. Notably, our findings are consistent with the organ Pd-PEPPSI type complexes that offer increased catalytic activity and provide basic information in the presence of solvents designing the monoligated Pd(0)-solvent.

Thermo-mechanical contact problems and elastic behaviour of single and double sides functionally graded brake disks with temperature-dependent material properties.

A thermo-elastic contact problem of functionally graded materials (FGMs) rotating brake disk with different pure brake pad areas under temperature dependent material properties is solved by Finite Element Method (FEM). The properties of brake disk change gradually from metal to ceramic by power-law distribution along the radial direction from the inner to the outer surface. Areas of the pure pad are changing while the vertical force is constant. The ratio of brake pad thickness to FGMs brake disk thickness is assumed 0.66. Two sources of thermal loads are considered: (1) Heat generation between the pad and brake disk due to contact friction, and (2) External thermal load due to a constant temperature at inner and outer surfaces. Mechanical responses of FGMs disk are compared with several pad contact areas. The results for temperature-dependent and temperature-independent material properties are investigated and presented. The results show that the absolute value of the shear stress in temperature-dependent material can be greater than that for temperature-independent material. The radial stress for some specific grading index (n = 1.5) is compressive near the inner surface for double contact while it is tensile for a single contact. It is concluded that the radial strain for some specific value of grading index (n = 1) is lower than other FGMs and pure double side contact brake disks.

N-Heterocyclic carbene or phosphorus ylide: which one forms a stronger bond with group 11 metals? A theoretical study.

N-Heterocyclic carbene and phosphorus ylides are inorganic and organometallic ligands, and their coordination chemistry with transition elements, particularly group 11 metals, would be noticeable. This study seeks to characterize the structure and nature of the C→M bond of group 11 metals (M = Cu(i), Ag(i), Au(i)) in coordination with different monodentate phosphorus ylides {P(Ph)3CHR} and N-heterocyclic carbenes (NHC(R)) (where R = F, Cl, Br, CF3, CH3, H, C(CH3)3, Si(CH3)3, SiH3, Ph). In this regard, DFT calculations with the PBE/def2-TZVP level of theory were applied. The results show that the M←C bond interaction energies (ΔEint) related to [NHC(R) → MR'] and [{P(Ph)3CHR} → MCl] complexes (M = Cu(i), Ag(i), Au(i); R = F, Cl, Br, CF3, H, CH3, C(CH3)3, Si(CH3)3, SiH3, Ph; R' = Cl, OAc) are substantial and conform to the well-known V-shaped trend for the transition metals of the first, second, and third row in the following order: Ag(i) < Cu(i) < Au(i). The nature of the C→M bond in the complexes was analyzed using NBO, AIM, EDA, and ETS-NOCV. The nature of the C→M bond interactions in [NHC(R) → MR'] and [{P(Ph)3CHR} → MCl] complexes studied here is largely electrostatic, and this feature accounts for about 65%-74% of the total interaction energy. Furthermore, it is found that in the presence of electron-donating substituents, the group 11 metals form stronger bonds with NHC(R) rather than monodentate phosphorus ylides. Comparison of the EDA-NOCV results for the M←C bond with the same M atom and R substituent in [NHC(R) → MR'] and [{P(Ph)3CHR} → MCl] indicates that the monodentate phosphorus ylide ligands studied here ({P(Ph)3CHR}) are slightly better σ-donors and weaker π-acceptors than the corresponding NHC(R) ligands.

Regioselective Green Electrochemical Approach to the Synthesis of Nitroacetaminophen Derivatives.

A regioselective green synthesis of nitroacetaminophen derivatives was carried out by electrochemical oxidation of acetaminophen, N-(2-hydroxyphenyl)acetamide, and 1-(4-(4-hydroxyphenyl)piperazin-1-yl)ethanone in the presence of nitrite ion as a nucleophile. The present work has led to the development of a reagentless green and facile electrochemical method for the synthesis of some nitroacetaminophen derivatives.

Comparison of various functionally graded femoral prostheses by finite element analysis.

This study is focused on finite element analysis of a model comprising femur into which a femoral component of a total hip replacement was implanted. The considered prosthesis is fabricated from a functionally graded material (FGM) comprising a layer of a titanium alloy bonded to a layer of hydroxyapatite. The elastic modulus of the FGM was adjusted in the radial, longitudinal, and longitudinal-radial directions by altering the volume fraction gradient exponent. Four cases were studied, involving two different methods of anchoring the prosthesis to the spongy bone and two cases of applied loading. The results revealed that the FG prostheses provoked more SED to the bone. The FG prostheses carried less stress, while more stress was induced to the bone and cement. Meanwhile, less shear interface stress was stimulated to the prosthesis-bone interface in the noncemented FG prostheses. The cement-bone interface carried more stress compared to the prosthesis-cement interface. Stair climbing induced more harmful effects to the implanted femur components compared to the normal walking by causing more stress. Therefore, stress shielding, developed stresses, and interface stresses in the THR components could be adjusted through the controlling stiffness of the FG prosthesis by managing volume fraction gradient exponent.

Preliminary analysis of knee stress in full extension landing.

OBJECTIVE: This study provides an experimental and finite element analysis of knee-joint structure during extended-knee landing based on the extracted impact force, and it numerically identifies the contact pressure, stress distribution and possibility of bone-to-bone contact when a subject lands from a safe height. METHODS: The impact time and loads were measured via inverse dynamic analysis of free landing without knee flexion from three different heights (25, 50 and 75 cm), using five subjects with an average body mass index of 18.8. Three-dimensional data were developed from computed tomography scans and were reprocessed with modeling software before being imported and analyzed by finite element analysis software. The whole leg was considered to be a fixed middle-hinged structure, while impact loads were applied to the femur in an upward direction. RESULTS: Straight landing exerted an enormous amount of pressure on the knee joint as a result of the body's inability to utilize the lower extremity muscles, thereby maximizing the threat of injury when the load exceeds the height-safety threshold. CONCLUSIONS: The researchers conclude that extended-knee landing results in serious deformation of the meniscus and cartilage and increases the risk of bone-to-bone contact and serious knee injury when the load exceeds the threshold safety height. This risk is considerably greater than the risk of injury associated with walking downhill or flexion landing activities.

Preliminary analysis of knee stress in Full Extension Landing

OBJECTIVE: This study provides an experimental and finite element analysis of knee-joint structure during extended-knee landing based on the extracted impact force, and it numerically identifies the contact pressure, stress distribution and possibility of bone-to-bone contact when a subject lands from a safe height. METHODS: The impact time and loads were measured via inverse dynamic analysis of free landing without knee flexion from three different heights (25, 50 and 75 cm), using five subjects with an average body mass index of 18.8. Three-dimensional data were developed from computed tomography scans and were reprocessed with modeling software before being imported and analyzed by finite element analysis software. The whole leg was considered to be a fixed middle-hinged structure, while impact loads were applied to the femur in an upward direction. RESULTS: Straight landing exerted an enormous amount of pressure on the knee joint as a result of the body's inability to utilize the lower extremity muscles, thereby maximizing the threat of injury when the load exceeds the height-safety threshold. CONCLUSIONS: The researchers conclude that extended-knee landing results in serious deformation of the meniscus and cartilage and increases the risk of bone-to-bone contact and serious knee injury when the load exceeds the threshold safety height. This risk is considerably greater than the risk of injury associated with walking downhill or flexion landing activities. .

Theoretical studies on the structure and protonation of Cu(II) complexes of a series of tripodal aliphatic tetraamines: Good correlations with the experimental data.

DFT(B3LYP) studies on first protonation step of a series of Cu(II) complexes of some tripodal tetraamines with general formula N[(CH(2))(n)NH(2)][(CH(2))(m)NH(2)][(CH(2))(p)NH(2)] (n = m = p = 2, tren; n = 3, m = p = 2, pee; n = m = 3, p = 2, ppe; n = m = 3, tpt; n = 2, m = 3, p = 4, epb; and n = m = 3, p = 4; ppb) are reported. First, the gas-phase proton macroaffinity of all latter complexes was calculated with considering following simple reaction: [Cu(L)](2+)(g) + H(+)(g) --> [Cu(HL)](3+)(g). The results showed that there is a good correlation between the calculated proton macroaffinities of all complexes with their stability constants in solution. Then, we tried to determine the possible reliable structures for microspecies involved in protonation process of above complexes. The results showed that, similar to the solid state, the [Cu(L)(H(2)O)](2+) and [Cu(HL)(H(2)O)(2)](3+) are most stable species for latter complexes and their protonated form, respectively, at gas phase. We found that there are acceptable correlations between the formation constants of above complexes with both the -Delta E and -Delta G of following reaction: [Cu(L)(H(2)O)](2+)(g) + H(+)(g) + H(2)O(g) --> [Cu(HL)(H(2)O)(2)](3+)(g). The -Delta E of the latter reaction can be defined as a theoretically solvent-proton macroaffinity of reactant complexes because they have gained one proton and one molecule of the solvent. The unknown formation constant of [Cu(epb)](2+) complex was also predicted from the observed correlations. In addition, the first proton affinity of all complexes was studied in solution using DPCM and CPCM methods. It was shown that there is an acceptable correlation between the solvent-proton affinities of [Cu(L)(H(2)O)](2+) complexes with formation constants of [Cu(HL)(H(2)O)(2)](3+) complexes in solution.

Theoretical studies on the first proton macroaffinity of Ni(II), Cu(II), Zn(II) and Cd(II) complexes of four triazacycloalkanes ([X]ane N3, X = 9-12): good correlations with the formation constants in solution.

A theoretical study on the first protonation step of Ni(ii), Cu(ii), Zn(ii) and Cd(ii) complexes of some triazacycloalkanes with general formula [X]ane N(3) (X = 9-12) is reported. The calculations were performed at DFT (B3LYP) level of theory, using LanL2DZ basis set. The DFT calculations were performed again using DZVP2 basis set for Ni(ii), Cu(ii) and Zn(ii) complexes and DZVP for Cd(ii) complexes. Once again, two kinds of our recently published definitions for gas-phase proton affinities of polybasic ligands, proton microaffinity and proton macroaffinity, were extended to their metal complexes. Among the 16 investigated complexes the most stable complex has both the smallest proton macroaffinity and macrobasicity. The least stable complex has also both the greatest proton macroaffinity and macrobasicity. In the case of each metal ion there are good correlations between the calculated gas-phase proton macroaffinities as well as macrobasicities of the corresponding complexes with their formation constants in solution.

First reported correlation between the calculated gas-phase proton macroaffinities of some metal complexes with their measured formation constants in solution: Zn(II) complexes of a series of tripodal aliphatic tetraamines.

A theoretical study on the first protonation step of a series of metal complexes with the general formula {M(N[(CH2)nNH2][(CH2)mNH2][(CH2)pNH2])2+} (n = m = p = 2, tren; n = 3, m = p = 2, pee; n = m = 3, p = 2, ppe; n = m = p = 3, tpt; n = 2, m = 3, p = 4, epb; and n = m = 3, p = 4, ppb; and M = Zn2+) was reported using both the Hartree-Fock and DFT (B3LYP) levels of theory. For the first time, two kinds of our recently published definitions for gas-phase proton affinities of polybasic ligands, proton microaffinity and proton macroaffinity, were extended to their metal complexes. There is a good correlation between the calculated gas-phase proton macroaffinities and the corresponding formation constants in solution.

Complete gas-phase proton microaffinity analysis of two bulky polyamine molecules.

Density functional theory (DFT) and ab initio (Hartree-Fock) calculations employing the 6-31G* basis set are used to determine gas-phase proton microaffinities (PA(n,i)) of two bulky symmetrical tripodal tetraamine ligands N[(CH2)(4)NH2]3, trbn, and N[(CH2)(5)NH2]3, trpa. The corresponding proton macroaffinities (PA(n)) are calculated not only according to our recently established method but also considering two alternative formulas based on a Boltzmann distribution. The successive protonation macroconstants in aqueous solution for these bulky amines are predicted from the well-defined correlation between the calculated proton macroaffinities, without considering Boltzmann distribution, and the corresponding log Kn for these amines. The overall protonation constants are also predicted by two different methods.