scholarly journals STRUCTURAL STUDY OF BIS(2,6-BIS(PYRAZOL-3-YL)PYRIDINE)NICKEL(II) BY CALORIMETRY AND EXAFS SPECTROMETRY

2010 ◽  
Vol 3 (2) ◽  
pp. 74-79
Author(s):  
Kristian H Sugiyarto
Keyword(s):  
Complex Formation ◽  
Bond Length ◽  
Structural Study ◽  
Formation Constants ◽  
Exafs Analysis ◽  
The Mean

The main aim of this work is to reveal the complex formation of 2,6-bis(pyrazol-3-yl)pyridine, bpp, with nickel(II) perchlorate in DMF by calorimetric stepwise complex formation and then followed by EXAFS spectrometry. It was found that the complex formation follows two stepwise pathways namely the formation of mono pyrazolyl-pyridine, [Ni(DMF)3 bpp]2+, and bis pyrazolyl-pyridine, [Ni(bpp)2]2+;  the formation constants being  log β1 = 6.57, and log β2 = 5.02, and the total value of log β  = 11.58. The final formation of six-coordinated compound was confirmed by EXAFS analysis with the mean Ni-Nbpp bond length of 2.0646(0.0014) Å.   Keywords: nickel(II), bpp, EXAFS

Formation of CT complexes and electron transfer from excited molecules of anthracene derivatives to methylviologen in aqueous and micellar media

1987 ◽  
Vol 52 (7) ◽  
pp. 1658-1665
Author(s):  
Viktor Řehák ◽  
Jana Boledovičová
Keyword(s):  
Electron Transfer ◽  
Complex Formation ◽  
Fluorescence Quenching ◽  
Rate Constant ◽  
Formation Constants ◽  
Dynamic Quenching ◽  
Micellar Media ◽  
Complex Formation Constants ◽  
Anthracene Derivatives ◽  
Ct Complexes

Disodium 1,5- and 1,8-anthracenedisulphonate (ADS) and 9-acetylanthracene form coloured CT complexes with methylviologen (MV2+) in aqueous and micellar media. The complex formation constants and molar absorptivities were determined by the Benesi-Hildebrandt method. In the fluorescence quenching, its static component plays the major role. The dynamic quenching component is determined by the rate constant of electron transfer from the S1 state of ADS to MV2+.

Reaktionen von Azacoronanden mit Quecksilber(II)iodid: Kristallstrukturen zweier Komplexe von Hgl2 mit Diaza-15-krone-5 und Diaza-18-krone-6 /Reactions of Azacoronands with Mercury(II) Iodide: Crystal Structures of Two Complexes of Hgl2 with Diaza-15-crown-5, and Diaza-18-crown-6

1997 ◽  
Vol 52 (7) ◽  
pp. 847-850 ◽  
Author(s):  
Joachim Pickardt ◽  
Sven Wiese
Keyword(s):  
Bond Length ◽  
Crystal Structures ◽  
Iodine Atom ◽  
Bond Lengths ◽  
The Mean ◽  
Iodide Crystal

The reactions of diaza-15-crown-5 (“2.1”), and diaza-18-crown-6 (“2.2”), resp., with HgI2 in methanol afford the compounds [Hg(2.1)I][Hg2I6] (1) and [Hg(2.2)I][Hg2I6] (2), the crystal structures of which were determined. 1 consists of isolated cations [Hg(2.1)I]+ and anions [Hg2I6]2-. In the cations Hg is coordinated by one iodine atom, the two N atoms and the three O atoms of the ligand; the Hg-I distance is 262.1(3) pm, the Hg-N bond lengths are 221(2) and 238(2) pm; they are significantly shorter than the Hg-O distances, which are in the range between 262 and 271 pm. 2 consists of cations [Hg(2.2)I]+, which are bridged by the anions. In the cations of 2 Hg is coordinated by an iodine atom and by the two N atoms of the ligand, but by only three of the four O atoms. The Hg-I distance is 275.8(5) pm, the mean Hg-N bond length 234(4) pm, and the Hg-O distances vary between 285 and 304 pm. The Hg-I distance to the bridging I atom of the anion is 388.6(6) pm. The Hg-I bond lengths within the anions are slightly widened by this coordination.

Neue Chalkogenometallate mit binuklearen Anionen, I: Darstellung und Kristallstruktur von Rb6Sn2S7 / New Chalcogenometallates with Binuclear Anions, I: Preparation and Crystal Structure of Rb6Sn2S7

1999 ◽  
Vol 54 (12) ◽  
pp. 1505-1509 ◽  
Author(s):  
Kurt O. Klepp ◽  
Ferdinand Fabian
Keyword(s):  
Crystal Structure ◽  
Bond Length ◽  
Sulfur Atom ◽  
Bond Angle ◽  
The Mean

Colorless crystals of the new thiostannate Rb6Sn2S7 were obtained by reacting a stoichiometric melt of Rb2S, Sn and S at 700°C. The compound is orthorhombic, oP60, s.g. P212121 (No. 19) with a = 9.982(4), b = 13.45(1), c = 15.20(1) Å; Z = 4. The crystal structure was determined from diffractometer data and refined to a conventional R of 0.043 (1380 Fo's, 137 variables). The crystal structure contains dimeric anions, [Sn2S7]2 -, which are built up by slightly distorted SnS4 tetrahedra sharing a common sulfur atom. The mean Sn-S bond length calculates as 2.384 Å, the bond angle on the bridging S is 110.4°. The structure contains six independent Rb-cations which are coordinated to 5-6 sulfur atoms in irregular configurations.

Host–Guest interaction of pesticide bifenox with cyclodextrin molecules. An electrochemical study

2009 ◽  
Vol 74 (11-12) ◽  
pp. 1647-1664 ◽  
Author(s):  
Magdaléna Hromadová ◽  
Romana Sokolová ◽  
Lubomír Pospíšil ◽  
Štěpánka Lachmanová ◽  
Nicolangelo Fanelli ◽  
...  
Keyword(s):  
Complex Formation ◽  
Anion Radical ◽  
Formation Constants ◽  
Aprotic Solvents ◽  
Reduction Wave ◽  
Nitroaromatic Compound ◽  
Complex Formation Constants ◽  
Oh Groups ◽  
Stable Anion ◽  
Main Factor

The reduction of nitroaromatic compound bifenox (methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate) was studied in aprotic solvents in the absence or presence of cyclodextrin (CD) molecules of different cavity sizes. βCD and γCD form complexes with bifenox in DMSO with the complex formation constants (5 ± 2) × 102 M–1 [βCD–bifenox] and (3 ± 1) × 102 M–1 [γCD–bifenox], respectively. Bifenox yields a relatively stable anion radical in dimethyl sulfoxide, which is further reduced at more negative potentials by an overall addition of three electrons and four protons to the corresponding phenylhydroxylamine. In the presence of βCD the first reduction wave of bifenox becomes irreversible, it is shifted towards more positive potentials and the uptake of more than one electron is observed (up to four electrons during the exhaustive electrolysis). The first reduction wave of bifenox is not affected by the addition of glucose confirming that a simple availability of protons from the OH groups is not the main factor in further transformation of anion radical in the presence of βCD. The complex formation with βCD facilitates the protonation and additionally protects the molecule from disintegration into 2,4-dichlorophenol. A yield of 2,4-dichlorophenol decreases in the order βCD, γCD and αCD, respectively.

Bond lengths in organic and metal-organic compounds revisited: X—H bond lengths from neutron diffraction data

2010 ◽  
Vol 66 (3) ◽  
pp. 380-386 ◽  
Author(s):  
Frank H. Allen ◽  
Ian J. Bruno
Keyword(s):  
Bond Length ◽  
Data Availability ◽  
General Level ◽  
Mean Values ◽  
Bond Lengths ◽  
Transition Metal Hydrides ◽  
Order Of Magnitude ◽  
Metal Organic ◽  
Structural Database ◽  
The Mean

The number of structures in the Cambridge Structural Database (CSD) has increased by an order of magnitude since the preparation of two major compilations of standard bond lengths in mid-1985. It is now of interest to examine whether this huge increase in data availability has implications for the mean bond-length values published in the late 1980s. Those compilations reported mean X—H bond lengths derived from rather sparse information and for rather few chemical environments. During the intervening years, the number of neutron studies has also increased, although only by a factor of around 2.25, permitting a new analysis of X—H bond-length distributions for (a) organic X = C, N, O, B, and (b) a variety of terminal and homometallic bridging transition metal hydrides. New mean values are reported here and are compared with earlier results. These new overall means are also complemented by an analysis of X—H distances at lower temperatures (T ≤ 140 K), which indicates the general level of librational effects in X—H systems. The study also extends the range of chemical environments for which statistically acceptable mean X—H bond lengths can be obtained, although values from individual structures are also collated to further extend the chemical range of this compilation. Updated default `neutron-normalization' distances for use in hydrogen-bond and deformation-density studies are also proposed for C—H, N—H and O—H, and the low-temperature analysis provides specific values for certain chemical environments and hybridization states of X.

P3Se4I: 5-Iodo-2,3,6,7-tetraselena-1,4,5-triphosphabicyclo[221]heptan, ein neues Phosphorselenaiodid / P3Se4I: 5-Iodo-2,3,6,7-tetraselena-1,4,5-triphosphabicyclo[221]heptan, a New Phosphorus Selena Iodide

1987 ◽  
Vol 42 (1) ◽  
pp. 47-51 ◽  
Author(s):  
Roger Blachnik ◽  
Willi Buchmeier ◽  
Claudia Schneider ◽  
Ulrike Wickel
Keyword(s):  
Bond Length ◽  
Nmr Spectra ◽  
Lattice Parameters ◽  
Monoclinic Space Group ◽  
Space Group ◽  
Bond Lengths ◽  
The Mean

P3Se4I is formed by the reaction of molten P4Se3 and I2. P3Se4I is monoclinic, space group P21/c with the lattice parameters of a = 1130.3(3) pm, b = 654.5(2) pm, c =1420.5(4) pm, β - 117.64(2)°. d = 3.87 g cm-3 and dx = 3.82 g cm-3 for Z = 4. The structure of the molecule is derived from the structure of α-or β-P4Se3I2 by the substitution of a P−I group by a Se-atom. The P−I, P−P and Se−Se bond lengths are 249.9, 219.2 and 236.9 pm. resp. The mean P−Se bond length is 225.0 pm. The molecule is stabilized by two weak intramolecular P−Se and P−I bonds, comparable to the bonding situation in α-P4Se3I2 . The 31P NMR spectra reveal a coalescence effect, due to equilibrium between two isomeric forms of the molecules.

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