Effects Of Transition Metal Complexes Research Articles

Viscosity Reduction and Mechanism of Aquathermolysis of Heavy Oil Co-Catalyzed by Bentonite and Transition Metal Complexes

At present, the research on aquathermolysis catalysts mainly focuses on the catalytic effect of external catalysts on the reaction, ignoring the fact that external catalysts will form complexes with in situ inorganic minerals after entering the reservoir. In this paper, we investigated the effects of transition metal complexes as external catalysts and bentonite as in situ catalysts on aquathermolysis, respectively. Meanwhile, the aquathermolysis reaction co-catalyzed by external and in situ catalysts was further investigated. The results show that the transition metal complexes exhibited good co-catalysis with bentonite. The viscosity reduction rate can reach 73.47% at 200 °C and 4 h with 0.1 wt.% of catalyst (NAD–Zn) addition. The addition of ethanol under the same reaction conditions will further increase the viscosity reduction rate to 84.59%. The results of thermogravimetric analysis, component analysis and boiling range analysis of heavy oil show that the heavy components in heavy oil are cracked into light components after the aquathermolysis. The results of elemental analysis show that the heteroatoms in the heavy oil were removed and the quality of the crude oil was improved. The results of GC–MS analysis of the model compounds showed that the process of aquathermolysis was mainly through the cleavage of C–C, C–N and C–S bonds to crack the macromolecules into small molecules, and then achieve the effect of viscosity reduction. The main mechanism of catalyst action is the acidic center on the surface of the bentonite and the coordination bonds formed by the transition metal complexes with the heteroatoms.

Quantification of Cooperativity between Metal Sites in Dinuclear Transition Metal Complexes Containing the (2-Dimethylamino)-4-(2-pyrimidinyl)pyrimidine Ligand.

A concept for the quantification of cooperative effects in transition-metal complexes is presented. It is demonstrated for a series of novel N,N- (mononuclear) and C,N-coordinated homo- and heterometallic binuclear complexes based on the (2-dimethylamino)-4-(2-pyrimidinyl)pyrimidine ligand, which are accessible by applying roll-over cyclometallation. These iridium-, platinum-, and palladium-containing compounds are investigated with respect to their absorption and fluorescence spectra. The cooperative effects in the electronic absorptions, i. e., the energetic shifts between mononuclear and dinuclear complexes, and free ligands are analyzed on the basis of the lowest energy π-π* transitions and compared to calculated data, obtained from TD-DFT calculations. Furthermore the corresponding fluorescence spectra are presented and analyzed with respect to the concept of cooperativity.

In vivo acute toxicity evaluation and in vitro molecular mechanism study of antiproliferative activity of a novel indole Schiff base β-diiminato manganeseIII complex in hormone-dependent and triple negative breast cancer cells.

Breast cancer is the most frequently diagnosed cancer among women worldwide. Recently, increasing attention has been paid to the anticancer effects of transition metal complexes of indole Schiff bases. β-diiminato ManganeseIII complex has shown promising cell cycle arrest and apoptosis induction against MCF-7 and MDA-MB-231 breast cancer cells. In this study, time- and dose- dependent inhibitory activity were evaluated using MTT assay after 48 h and 72 h exposure time. In addition, median effect analysis was conducted according to Chou–Talalay method to investigate whether MnIII complex has synergistic effect in combination with chemotherapeutic drugs on inhibiting breast cancer cell growth. The molecular mechanisms underlying its potent antiproliferative effect was determined through bioluminescent caspase-3/7, -8 and -9 activity assays and quantitative expression analysis of cell cycle- and apoptosis-related genes. Furthermore, safety evaluation of MnIII complex was assessed through the acute oral toxicity test in in vivo model. The MTT assay results revealed that it potently reduced the viability of MCF-7 (IC50 of 0.63 ± 0.07 µg/mL for 48 h and 0.39 ± 0.08 µg/mL for 72 h) and MDA-MB-231 (1.17 ± 0.06 µg/mL for 48 h, 1.03 ± 0.15 µg/mL for 72 h) cells in dose- and time-dependent manner. Combination treatment also enhanced the cytotoxic effects of doxorubicin but not tamoxifen on inhibiting breast cancer cell growth. The involvement of intrinsic and extrinsic pathway in apoptosis induction was exhibited through the increased activity of caspase-9 and caspase-8, respectively, leading to enhanced downstream executioner caspase-3/7 activity in treated MCF-7 and MDA-MB-231 cells. In addition, gene expression analysis revealed that MnIII complex exerts its antiproliferative effect via up-and down-regulation of p21 and cyclin D1, respectively, along with increased expression of Bax/Bcl-2 ratio, TNF-α, initiator caspase-8 and -10 and effector caspase-3 in MCF-7 and MDA-MB-231 cells. However, the results did not show increased caspase-8 activity in treated MCF-7 cells. Furthermore, in vivo acute oral toxicity test revealed no signs of toxicity and mortality in treated animal models compared to the control group. Collectively, the promising inhibitory effect and molecular and mechanistic evidence of antiproliferative activity of MnIII complex and its safety characterization have demonstrated that it may have therapeutic value in breast cancer treatment worthy of further investigation and development.

Rhodium-catalyzed synthesis of 2,3-disubstituted indoles from β,β-disubstituted stryryl azides.

Rhodium-catalyzed synthesis of 2,3-disubstituted indoles from β,β-disubstituted stryryl azides.

Tailoring Transition Metal Complexes for Nonlinear Optics Applications. 2. A Theoretical Investigation of the Second-Order Nonlinear Optical Properties of M(CO)5L Complexes (M = Cr, W; L = Py, PyCHO, Pyz, PyzBF3, BPE, BPEBF3)

In this work, we report an ab initio investigation of second-order nonlinear optical (NLO) properties and absorption electronic spectra of push-pull transition metal chromophores of the formula [M(CO)(5)L] (M = Cr, W; L = pyridine (Py), 4-formyl-pyridine (PyCHO), pyrazine (Pyz), trans-1,2-bis(4-pyridyl)ethylene (BPE)). Pyz and BPE are considered either with one nitrogen atom free or interacting with the strong acceptor BF(3). All of the molecular properties have been calculated using two different and methodologically independent approaches: the time dependent and coupled perturbed density functional theories (TDDFT and CPDFT) and the sum-over-states (SOS) approach, where the excited states are obtained via the single configuration interaction (SCI) ab initio method. DFT results are in acceptable agreement with the experimental energy values of electronic transitions (with the exception of chromophores with the large pi-delocalization, like BPE); SCI calculations overestimate excitation energies and produce an inversion in the order of d(M) --> pi(L) and d(M) --> pi(CO) transitions. The SCI-SOS approach gives first-order hyperpolarizabilities, basically in agreement as trend and values with the experiments and seems to be a tool generally suitable for the evaluation of these properties also for transition metal complexes. On the other hand, the first-order hyperpolarizabilities computed using the CPDFT approach are consistently overestimated in comparison with the experimental results, especially in the case of a ligand with large pi-delocalization. We also show that the "two-level" approximation taking into account only the lowest energy charge transfer excitation (e.g., d(M) --> pi(L)) is not applicable to chromophores with the extended pi-delocalized ligand (BPE) coordinated to a transition metal, due to significant contributions originating from intraligand pi(L) --> pi(L) transitions. This study reports a detailed analysis and comparison of electronic NLO effects of transition metal complexes computed with DFT and ab initio SCI-SOS methodology.

Bonding in cis- and trans-dichlorobis(dimethylsulfide)platinum(II) studied by vibrational (micro)spectroscopy and force field calculations

The vibrational spectra of the square-planar complexes cis- and trans-dichlorobis(dimethylsulfide)platinum(II) have been investigated using Raman and synchrotron infrared microscopy of small samples, and mid- to far-infrared spectroscopy of macroscopic samples. Synthesis of the compounds produces the cis- and trans-stereoisomers. Using microscopy we were able to identify single crystals of the trans isomer and amorphous regions containing both cis and trans isomers. The infrared and Raman data are interpreted using force field calculations. Spectral shifts are discussed in terms of influence of the cis- and trans-ligands. It is found that vibrational spectroscopy is a sensitive technique for measuring subtle chemical effects in transition metal complexes which complements and may improve studies made with X-ray crystallography.

The bacteriocidal effects of transition metal complexes containing the NO+ group on the food-spoilage bacterium Clostridium sporogenes.

The chemical and molecular mechanism of toxicity of nitrite towards food-spoilage bacteria such as Clostridium botulinum or Clostridium sporogenes is not well understood. In order to discover the active species and explore its chemistry, a number of compounds related to nitrite were synthesized. Their bacteriocidal effects on C. sporogenes were investigated in Oxoid nutrient broth No. 2 growth medium at pH 7.0. Inhibition of cell growth, expressed as the concentration which causes 50% cell inhibition, was observed with nitrite at 10 mM, whereas [Fe4S3(NO)7]-(the anion of Roussin's black salt) and (Fe2(SCH2CH2OH)2(NO)4] (a water-soluble Roussin's red salt ester) were found to be effective at 0.001 mM and 0.005 mM, respectively, confirming previous reports that iron-sulphur-nitrosyl complexes are much more toxic to these organisms than nitrite itself. The nitroprusside anion, [Fe(CN)5NO]2- was found to be toxic at 0.030 mM and the corresponding chromium species, [Cr(CN)5NO]3-, at 0.1 mM. Therefore, on the basis of the number of NO groups present, the nitrosylcyano complexes are comparable in activity with the iron-sulphur-nitrosyl compounds. These results show that neither iron nor sulphur are essential for the bacteriostatic effect of the Roussin's type compounds. The property that all these compounds have in common is that they contain NO+. It is proposed that this is the active species responsible for the preservative effect of nitrite, and that a relationship may exist between the N-O stretching frequency, a measure of the NO+ character, and the toxicity of these NO(+)-containing complexes.

The effects of transition metal complexes on the permeation of small gas molecules through cellulose acetate membranes

Cellulose acetate (CA) membranes containing RuCl3·3H2O and RhCl [P(C6H5)3]3 were prepared reproducibly. Such membranes, on treatment with CO, formed metal-carbonyl species at relatively low temperature. The Ru-carbonyls formed in CA were quite stable at 40°C in comparison with the Rh-carbonyl species and, interestingly, there was no permeation of CO gas through the ruthenium-containing CA membrane at 40°C. However, the permeation of other gas molecules, such as H2, N2 and O2, through the same membrane was reduced only slightly, probably due to the cross-linking effect of the transition metal complexes in CA. It was found that essentially pure H2 gas could be recovered from a 1: 1 mixture of H2 and CO gases using ruthenium-containing cellulose acetate membranes.

Synergistic effects in transition-metal complexes with two or three ligands

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynergistic effects in transition-metal complexes with two or three ligandsF. Strobel and D. P. RidgeCite this: Inorg. Chem. 1988, 27, 5, 891–893Publication Date (Print):March 1, 1988Publication History Published online1 May 2002Published inissue 1 March 1988https://doi.org/10.1021/ic00278a028RIGHTS & PERMISSIONSArticle Views278Altmetric-Citations15LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (371 KB) Get e-Alerts Get e-Alerts

Use of proton NMR to study low symmetry bonding effects in transition metal complexes

Abstract The 300 MHZ proton NMR chemical shifts of the mixed complex (salicylaldehyde)(acetyl-acetone)ethylenediimino nickel(II) and the two corresponding non-mixed complexes were studied. The differences in chemical shifts were very small, ∼ 0.05 ppm, but by looking at both the mixed and non-mixed species in the same solution relative values could be determined. The differences in chemical shifts were attributed to both a geometry effect and a basicity effect.

Correlational aspects of substituent effects in transition metal complexes containing non-fused phenyl rings transition metal complexes containing non-fused phenyl rings

Correlational aspects of substituent effects in transition metal complexes containing non-fused phenyl rings transition metal complexes containing non-fused phenyl rings

Catalytic properties of cobalt and manganese complexes with macromolecular ligands in the liquid-phase oxidation of ethylbenzene

The selective catalytic effect of transition metal complexes (in particular cobalt and manganese) with polymeric ligands is shown on the example of the liquid-phase oxidation of ethylbenzene. The catalytic activity depends on both the structure of the polymeric matrix and the nature of metal.

Effects of transition metal complexes on human lymphocyte blastogenesis in vitro

Summary The effect of two Platinum (II), two Rhodium (I), and two Ruthenium (II) complexes on the in vitro blastogenic response of human peripheral lymphocytes has been tested. All compounds except Ru(II) (DMSO)2 o -phen-Cl2 strongly inhibit the blastogenic response stimulated by mixed culture and by PHA. In the discussion of the results special emphasis is given to the pronounced difference between inhibition of PHA- and mixed culture-stimulated lymphocytes shown by the two platinum compounds.

ChemInform Abstract: CYCLOADDITION OF DIAZOESTERS TO NORBORNADIENE, AND RAPID CYCLOREVERSION OF THE ADDUCT, EFFECT OF TRANSITION METAL COMPLEXES

AbstractCycloaddition of Diazoesters to Norbornadiene, and Rapid Cycloreversion of the Adduct; Effect of Transition‐metal Complexes.

Cycloaddition of diazoesters to norbornadiene, and rapid cycloreversion of the adduct; effect of transition-metal complexes

Norbornadiene reacts with diazoesters with formation of 3- or 5-ethoxycarbonylpyrazole (II) and cyclopentadiene(III); this is the first example of a mild cycloreversion of a 1,3-dipolar adduct obtained from a diazoalkane, and metal carbonyl complexes accelerate the 1,3-dipolar addition of the diazoester to the double bond.

The Transmission of Substituent Effects in Transition Metal Complexes

The effect of ligand substitution on bonding to other ligands has been investigated in a series of V(III) complexes. Nuclear magnetic resonance (n.m.r.) contact shifts have been utilized for this purpose. These shifts are interpreted as arising from metal to ligand charge transfer. The results obtained are contrary to those expected from simple considerations of the electron withdrawing or donating abilities of the substituents. Electron withdrawing substituents decrease the charge transfer to the substituted ligand and increase the charge transfer to the remaining ligands. Electron donating substituents have the opposite effect. A simple interpretation is proposed to account for these results. An electron withdrawing substituent on a ligand in the xy plane increases the occupancy of dxy which cannot interact with the π system of the ligand in the xy plane but which is available for π bonding with the remaining ligands. Effects of this type are to be anticipated whenever the filling of the t2g orbitals is not symmetrical.

Transmission of Electronic Effects in Transition Metal Complexes

AN interesting aspect of transition metal chemistry relates to the influence which one ligand partner, in a mixed complex, may exert on another. The importance of electronic effects transmitted through a central metal ion is demonstrated, for example, by the directing influence of certain ligands in substitution reactions1. We report here some preliminary results on the influence of certain anionic ligands on the nature of the metal–pyridine bond in mixed complexes of cobalt (II). Our evidence for transmitted electronic effects in these complexes rests on certain striking differences in the influence of X on the position of equilibrium in the following configurational transformation : in chloroform solution. Py = pyridine and X = Cl−, Br−, I−, OCN−, SCN− or SeCN−. Co(II) complexes are well suited to configurational equilibria investigations of this kind because of the relatively high crystal field stabilization energy expected for the d7 configuration in a tetrahedral field2, and experimentally, because of the separate well-defined visible spectral characteristics of the two stereo -chemical arrangements. Equilibrium constants derived from spectrophotometric measurements were coupled with enthalpies determined calorimetrically and the associated entropy changes calculated. Since chloroform is relatively non-co-ordinating, the derived thermo-dynamic quantities refer, fairly closely, to the actual association reaction as represented in equatior (1).