scholarly journals The phase transition in bis(methyl(2-phenylethyl)ammonium) tetrabromidocuprate(II)

2014 ◽  
Vol 70 (a1) ◽  
pp. C1688-C1688
Author(s):  
Marcus Bond
Keyword(s):  
Transition Temperature ◽  
Ambient Temperature ◽  
Color Change ◽  
Phenyl Group ◽  
Exothermic Peak ◽  
Steady Increase ◽  
Organic Layer ◽  
Tetrahedral Geometry ◽  
Square Planar ◽  
Axis Length

Bis(methyl(2-phenylethyl)ammonium) tetrachloridocuprate(II) is a well-known thermochromic compound that exhibits an abrupt color change (from green to yellow) at 353 K that is caused by a change in coordination geometry from square planar to flattened tetrahedral [1]. As part of a reinvestigation of established thermochromic chloridocuprate(II) and their related compounds, the bromide analog [bis(methyl(2-phenylethyl)ammonium) tetrabromidocuprate(II)] has been studied anew. The structure redetermination at ambient temperature agrees with the original [2] (CSD refcode: FUTTIX), i.e. alternating layers of flattened tetrahedral tetrabromidocuprate(II) complexes and of organic cations stacked along the a-axis of the monoclinic C2/c unit cell. A DSC scan from ambient temperature to 183 K reveals an exothermic peak (and corresponding endothermic peak upon heating) at 215 K. Single crystal structures, determined from ambient temperature to 120 K in steps of ~20 K, track a steady increase in b-axis length on cooling to the transition temperature. Across the transition temperature abrupt 1.1% and 0.74% increases in lengths of the b- and c-axes, respectively. and a 0.23% decrease in the a-axis length are observed with no change in space group. Slight changes of the organic cation phenyl group conformation are observed across the transition temperature that cause the organic layer to spread out and become thinner so that neighbouring layers are stacked more closely together along a. However, the flattened tetrahedral geometry of the tetrabromidocuprate(II) complex remains essentially unchanged across the transition.

Effect of reduced graphene oxide on mechanical behavior of an epoxy adhesive in glassy and rubbery states

2021 ◽  
pp. 002199832110316
Author(s):  
Ata Khabaz-Aghdam ◽  
Bashir Behjat ◽  
EAS Marques ◽  
RJC Carbas ◽  
Lucas FM da Silva ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Ambient Temperature ◽  
Mechanical Behavior ◽  
Reduced Graphene Oxide ◽  
Epoxy Adhesive ◽  
Ultimate Strain ◽  
Reduced Graphene

The mechanical behavior of an adhesive, in neat state and reinforced with up to 0.5 wt% of reduced graphene oxide (RGO) was investigated here. Tests were done at temperatures between the ambient temperature and the glass transition temperature ( Tg[Formula: see text] of the adhesive. Using a metal mold, cured plates of the neat and RGO reinforced epoxy adhesive were prepared. The adhesive powder and the bulk dumbbell-shaped specimens, obtained from cured adhesive plates, were subjected to differential scanning calorimetry (DSC) and tensile tests, respectively, to obtain the Tg as well as mechanical properties of the adhesives. The results indicated that adding RGO up to 0.5 wt% increased the glass transition temperature, the modulus of elasticity, and the strength of the adhesive. It was found that the presence of RGO reduced the adhesive’s strain at the break at the ambient temperature. However, at high temperatures, near the Tg, the ultimate strain of RGO-reinforced adhesives decreased slightly when compared to the ultimate strain of the neat specimens. This explains the reduction in toughness at ambient temperature obtained by adding RGO and the increase at high temperatures. Finally, the failure morphology of the neat and RGO-reinforced adhesive specimens was investigated using microscopic imaging of the specimens’ failure cross-sections, which supported and justified the experimental observations.

Silane Functionalized Ethylene/Diene Copolymer Modifiers in Composites of Heterophasic Polypropylene and Microsilica

2007 ◽  
Vol 15 (5) ◽  
pp. 343-355 ◽  
Author(s):  
S. Lipponen ◽  
P. Pietikäinen ◽  
U. Vainio ◽  
R. Serimaa ◽  
J.V. Seppälä
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Impact Strength ◽  
Ambient Temperature ◽  
Metallocene Catalyst ◽  
The Poor ◽  
Rubber Toughened ◽  
Rubbery Phase ◽  
The Impact

Ethylene/1,7-octadiene copolymer was polymerised with metallocene catalyst and hydrosilylated to form silane functionalised polyethylenes (PE-co-SiX, X=Cl, OEt, Ph). The functionalised species were tested as modifiers in composites of rubber toughened polypropylene (heterophasic PP, hPP) and microsilica filler (μSi). A metallocene-based functionalised PE (PE-co-SiF) produced earlier in our laboratory and three commercial grades of functionalised polyolefins (one PE- and two PP-based) were used as reference modifiers. Major differences were seen in the toughness of the composites both above and below the glass transition temperature (Tg) of PP. In addition to increasing the stiffness, the microsilica filler enhanced the toughness of the heterophasic polypropylene by over 200% at ambient temperature. Below the Tg of PP (at −20 °C), the influence of μSi was the opposite and the impact strength of the hPP/μSi composite was below that of unfilled hPP. With the addition of just 2 wt% of functionalised polyethylene, the poor cold toughness of hPP/μSi composite was improved by nearly 100%. With the same addition, the toughness of the composites at ambient temperature was improved by 50 to 100% compared with the unfilled hPP. This behaviour was explained by significant changes in the fracture mechanism. Addition of functionalised PE increased the concentration of microsilica in the rubbery phase, allowing the crack to enter that phase. The rubbery phase was also able to absorb a large amount of impact energy below the glass transition temperature of PP.

scholarly journals Synthesis and Structural Studies of Some Inorganic Polymers of Succinoyl Carboxymethyl Cellulose

2011 ◽  
Vol 8 (4) ◽  
pp. 1993-1999 ◽  
Author(s):  
H. D. Juneja ◽  
Manisha Joshi ◽  
N. T. KhatiI
Keyword(s):  
Ir Spectroscopy ◽  
Carboxymethyl Cellulose ◽  
Aqueous Media ◽  
Octahedral Geometry ◽  
Planar Geometry ◽  
Inorganic Polymers ◽  
Structural Studies ◽  
Tetrahedral Geometry ◽  
Square Planar ◽  
Uv Reflectance

The inorganic polymers containing transition metals such as Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) were synthesized by using succinoyl carboxymethyl cellulose (SCMC) in aqueous media. The newly synthesized polymers were characterized by elemental analysis, IR spectroscopy, TG analysis, UV reflectance spectra and magnetic moment. On the basis of these studies, the composition of the polymeric unit was found to be [M(II)L]n, [Mʼ(II)L.2H2O]n, {[Mˮ(II)L.2H2O]n H2O}, where M= Zn(II), Mʼ = Mn(II), Ni(II) and Cu(II) and Mˮ = Co(II), L = SCMC ligand. On the basis of instrumental techniques, it has been found that the [Zn(II)(SCMC)]n inorganic polymer has tetrahedral geometry, whereas {[Cu(II)(SCMC)].2H2O}n has square planar geometry and [Mn(II)(SCMC).2H2O]n, {[Co(II)(SCMC).2H2O)].H2O}n and [Ni(II) (SCMC).2H2O]n have octahedral geometry. The decomposition temperatures of the inorganic polymers have been determined by TGA. The TGA reveal that the Mn(II) polymer of SCMC is highly thermally stable than rest of the polymers and these polymers can be used as thermal resisting materials.

Cobalt(II), nickel(II) and copper(II) complexes of some 2'-hydroxychalcones

1980 ◽  
Vol 33 (4) ◽  
pp. 737 ◽  
Author(s):  
M Palaniandavar ◽  
C Natarajan
Keyword(s):  
Infrared Spectra ◽  
Metal Ion ◽  
Magnetic Moments ◽  
Phenyl Group ◽  
Ligand Field ◽  
Square Planar ◽  
Spin Pairing ◽  
Square Configuration ◽  
Electron Sink ◽  
Octahedral Configuration

Metal(II) bis-chelates of the type ML2 [M = CoII, NiII, CuII; L = 2'- hydroxy-5'-X-chalcone where X = H, CH3, Cl] have been prepared and studied. Structures have been assessed by the measurement of magnetic moments, ligand field and infrared spectra and thermal properties. These chelates possess low-spin trans-square-planar configuration and show resistance to adduct formation in contrast to metal(II) chelates of β-diketones, salicylaldehyde, o-hydroxyaryl ketones and esters and o-hydroxy-crotonophenones, which have high-spin octahedral configuration. Extensive conjugation lowers the energy of the π3* orbital which enters into a very strong dπ-π3* interaction leading to spin-pairing. ��� Infrared spectra indicate that the carbonyl group is perturbed only slightly by coordination to metal. A change in metal ion affects v(C=O), v(M-O) and other vibrations and the order of stability, namely, Co ≈ Ni < Cu, inferred from these vibrations is as expected for the low-spin square configuration of the chelates. Introduction of substituents (5'-X) alters only v(M-O) significantly and the order of stability, namely, Cl > CH3 > H, derived from v(M-O) is consistent with Taft's resonance polar parameters of the substituents. All these observations are explained by the electron sink property of the phenyl group.

Synthesis and Photophysical Study of Divalent Complexes of Chelating Schiff Base

2020 ◽  
Vol 1 (01) ◽  
pp. 5-16
Author(s):  
Alaa A. Rashad ◽  
Farah Muaiad ◽  
Ahmed Ahmed ◽  
EkhlasA. Salman ◽  
Evon Akram
Keyword(s):  
Schiff Base ◽  
Surface Morphology ◽  
Theoretical Study ◽  
Energy Gap ◽  
Photophysical Properties ◽  
Schiff Base Complex ◽  
Tetrahedral Geometry ◽  
Force Microscopy ◽  
Atomic Force ◽  
Square Planar

 Background: Schiff base compounds derivative from1,2,4-triazole, and their transition metal complexes play an essential role in coordination and bioinorganic chemistry due to biological and industrial applications. Objective: The work aims to prepare and characterize of 1, 2, 4-triazole Schiff base and its complexes with a theoretical study using  PM3 calculation and HyperChem program, photophysical properties, and surface morphology for these complexes. Methods: 1, 2, 4-triazole Schiff base prepared by condensation reaction between  4-Amino-3-mercapto-5-phenyl-4H-1,2,4-triazole and 2-hydroxy-1-naphthaldehyde, then Schiff base reacted with Co2+, Ni2+,  and Cu2+ ions,   the synthesized 1, 2, 4-triazole Schiff base, and its complexes were characterized by infrared spectra, magnetic susceptibility, conductivity measurements, photophysical properties, and surface morphology measured by atomic force microscopy. The practical results were reinforced with a theoretical study for these Schiff base complexes. Then the proposed structures of the prepared complexes. Results: 1, 2, 4-triazole Schiff base act as a chelate ligand. The coordination has occurred through the oxygen of the phenolic group O-H and the nitrogen of the imine group N=C of Schiff base with divalent metal ions. Cobalt complex has a tetrahedral geometry, while the nickel and copper complexes have square planar geometries. The stability of all compounds was studied by calculating the energy gap by diffuse reflectance spectroscopy and theoretical calculations. Copper Schiff base is a more stable complex due to the lower value of the energy gap, and the copper Schiff base complex is more semiconductivity than the other complexes. Surface morphology, properties of chelating  Schiff base ligand and its complexes measured by atomic force microscopy, cobalt Schiff base complex is higher roughness. The bond length of (-C=N-), (-C-O-),(M-O), and (M-N)  are affected in the coordination with metal ions, the bond length of the square planar geometry more affected than tetrahedral geometry. Conclusion: All compounds were prepared successfully, characterized, and photophysical properties were studied.  

scholarly journals Coordination Polymer: Synthesis, Spectral Characterization and Thermal Behaviour of Starch-Urea Based Biodegradable Polymer and Its Polymer Metal Complexes

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
Ashraf Malik ◽  
Shadma Parveen ◽  
Tansir Ahamad ◽  
Saad M. Alshehri ◽  
Prabal Kumar Singh ◽  
...  
Keyword(s):  
Thermogravimetric Analysis ◽  
Coordination Polymer ◽  
Metal Complexes ◽  
Magnetic Moment ◽  
Tetrahedral Geometry ◽  
Square Planar ◽  
Visible Spectra ◽  
Polymeric Compounds ◽  
Polymer Metal ◽  
Ft Ir

A starch-urea-based biodegradable coordination polymer modified by transition metal Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) was prepared by polycondensation of starch and urea. All the synthesized polymeric compounds were characterized by Fourier transform-infrared spectroscopy (FT-IR),H-NMRspectroscopy,C-NMRspectroscopy, UV-visible spectra, magnetic moment measurements, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). The results of electronic spectra and magnetic moment measurements indicate that Mn(II), Co(II), and Ni(II) complexes show octahedral geometry, while Cu(II) and Zn(II) complexes show square planar and tetrahedral geometry, respectively. The thermogravimetric analysis revealed that all the polymeric metal complexes are more thermally stable than the parental ligand. In addition, biodegradable studies of all the polymeric compounds were also carried out through ASTM standards of biodegradable polymers byCO2evolution method.

Square Planar vs Tetrahedral Geometry in Four Coordinate Iron(II) Complexes

2005 ◽  
Vol 44 (9) ◽  
pp. 3103-3111 ◽  
Author(s):  
Eric J. Hawrelak ◽  
Wesley H. Bernskoetter ◽  
Emil Lobkovsky ◽  
Gordon T. Yee ◽  
Eckhard Bill ◽  
...  
Keyword(s):  
Tetrahedral Geometry ◽  
Square Planar

scholarly journals Propagation of uncertainty in experiment: structures of Ni (II) coordination complexes

2018 ◽  
Vol 25 (4) ◽  
pp. 920-934 ◽  
Author(s):  
Martin J. Schalken ◽  
Christopher T. Chantler
Keyword(s):  
Hypothesis Testing ◽  
Information Content ◽  
Coordination Complexes ◽  
Data Uncertainty ◽  
Tetrahedral Geometry ◽  
High Point ◽  
Propagation Of Uncertainty ◽  
Square Planar ◽  
Valid Comparison ◽  
Physical Insight

Accurate experimental XAFS (X-ray absorption fine-structure) data including uncertainties are required during analysis for valid comparison of results and conclusions of hypothesis testing on structural determinations. Here an approach is developed to investigate data without standard interpolation of experimental data and with minimal loss of information content in the raw data. Nickel coordination complexes bis(i-n-propylsalicylaldiminato)nickel(II) (i-pr) and bis(N-n-propylsalicylaldiminato)nickel(II) (n-pr) are investigated. The additional physical insight afforded by the correct propagation of experimental uncertainty is used to determine newly refined structures for the innermost co-ordination shell. Two sets of data are investigated for each complex; one optimized for high point accuracy and one optimized for high point density. Clearly both are important and in this investigation the quality of the physical insight from each is directly provided by measured and propagated uncertainties to fairly represent the relevant accuracies. The results provide evidence for an approximate tetrahedral geometry for the i-pr Ni complex that is more symmetric than previously concluded, with our high point accuracy data yielding ligand lengths of 2.017 ± 0.006 Å and 2.022 ∓ 0.006 Å for Ni—N and Ni—O bonds, respectively, and an even more skewed square-planar (i.e.rhombohedral) arrangement for the n-pr complex with corresponding bond lengths of 2.133 ± 0.004 Å and 1.960 ∓ 0.003 Å. The ability to distinguish using hypothesis testing between the subtle differences in XAFS spectra arising from the approximate local tetrahedral and square-planar geometries of the complexes is also highlighted. The effect of standard interpolation on experimental XAFS spectra prior to fitting with theoretical model structures is investigated. While often performed as a necessary step for Fourier transformation into position space, this will nonetheless skew the fit away from actual data taken, and fails to preserve the information content within the data uncertainty. The artificial effects that interpolation imposes on χr2are demonstrated. Finally, a method for interpolation is introduced which locally preserves the χr2and thus information content, when a regular grid is required,e.gfor further analysis inr-space.

scholarly journals INTRAMOLECULARLY HYPERCOORDINATED ORGANOLEAD COMPOUNDS: (o-MeOC6H4-CH2)PbPh2R, R = Ph, Cl, WITH Pb–O SECONDARY BONDING

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Hemant K. Sharma ◽  
Alejandro J. Metta-Magaña ◽  
Laura I. Saucedo ◽  
Marcela López-Cardoso ◽  
Keith H. Pannell
Keyword(s):  
Structural Analysis ◽  
Organic Ligand ◽  
Phenyl Group ◽  
Group 14 ◽  
Tetrahedral Geometry ◽  
Trigonal Bipyramidal ◽  
Internuclear Distances ◽  
Organolead Compounds ◽  
Oxygen Functionality ◽  
Secondary Bonding

Abstract The tetrahedral geometry of organolead(IV) compounds can be readily transformed by using an organic ligand containing a dangling-arm oxygen functionality. The acidity of the Pb center results in so-called secondary bonding between O and Pb thereby pushing the geometry at Pb toward a trigonal bipyramidal (tbp) structure. Replacing a phenyl group by a chlorine atom dramatically enhances this phenomenon. Thus for (o-methoxybenzyl) triphenyllead (4), and (o-methoxybenzyl)diphenyllead chloride (5), the Pb–O internuclear distances are 3.362(4) and 2.845(3) Å, respectively; 83% (4) and 70% (5) of the sum of the van der Waals Pb and O radii. Within the group 14 element congeners the structural analysis of the (o-methoxybenzyl)triphenylE compounds, E = Si, Ge, Sn, and now Pb, demonstrates the relative acidities of E are Si &lt; Ge &lt; Sn &lt; Pb.

scholarly journals Structures of Pt(0)P3, Pt(0)P4 and Pt(II)P4 – Distortion isomers

2020 ◽  
Vol 43 (1) ◽  
pp. 111-116
Author(s):  
Milan Melník ◽  
Peter Mikuš
Keyword(s):  
Structural Parameters ◽  
Donor Ligands ◽  
Planar Geometry ◽  
Bidentate Ligands ◽  
Tetrahedral Geometry ◽  
Cooperative Effects ◽  
Square Planar ◽  
Crystal Class ◽  
Planar Geometries

AbstractIn this review are analyzed and classified crystallographic and structural parameters of P(0)P3, Pt(0) P4 and Pt(II)P4 derivatives – distortion isomers. Some of the isomers are differing not only by degree of distortion but also by crystal class. There are three types of organo-phosphines which build up the respective geometry about the platinum atoms. In Pt(0)P3 a distorted trigonal planar geometry is build up by three monodentate PPh3 ligands. In Pt(0)P4 a tetrahedral geometry with various degree of distortion is build up by a pair of homo-bidentate ligands. In Pt(II)P4 isomers a square-planar geometries with various degree of distortion are build up by bidentate-P,P’donor ligands, (except one example of isomers, where a tetradentate is involved). The bidentate-P,P’-donor ligands form: four-(PNP,PCP), five-(PC2P) and six-(PC3P) metallocyclic rings. The tetradentate forms five-(PC2P). There are some cooperative effects between Pt–P bond distances and the metallocyclic rings, and at the same time a distortion of the respective geometry increases.

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