Emission studies of pyrene solutions

Emission spectra of pyrene in hexane have been obtained over a temperature range (from 130 to 260 K) that has not been explored before for concentrations ranging from 10^?4 mole/? to 2 × 10^?2 mole/?. A conventional and new approximation which does not depend on the experimental set-up response functions has been used for evaluating pyrene excimer association energy W_DM and other pyrene parameters. In both methods W_DM agrees quite satisfactorlly, at all concentrations used, with that reported in the literature and obtained by other techniques. However, both approximation fail to yield the right values of the rate parameters at concentrations ? 2 g/?. This set the upper limit of sample solubility to be at C = 2g/? for our range of temperature. Furthermore, the new approximation can probably be used at higher concentration (for higher range of temperature) and even may be used for other organic molecules. There was also no difference in the ratio of the excimer (I_D) to monomer (I_M) quantum yields when an intense laser beam was used as a source of excitation rather than a super-pressure Hg-lamp. This suggested that the concentrations we used might not be large enough. As a result, the laser beam would not create enough density of excited molecules to affect the ratio of I_D/I_M.     

Crystal Structure and Mass-, Electronic-, Infrared Spectral Studies on Hexaaqua Ni(II) Bis(O-Tolylazo-Citrazinate) Hexahydrate Complex

A new crystalline octahedral hexaaqua Ni(II) bis(o-tolylazo-citrazinate)hexahydrate complex was synthesized. The analytical data proved the formation of 1:2 stoichiometry. An X-ray structure investigation has been carried out. The triclinic space group is p and the unit cell parameters are a = 585.5 pm, b = 993 pm, c = 1139.4 pm, α = 101.6°, β = 97.4°, γ = 102.4°. Evaluation of intensity data revealed the structure with an R-value of 0.03 (2316 observed independent reflections). The compound consists of hexaaqua nickel(2+) ions, univalent anions of the carboxylic acid and six additional water molecules per     

Coordination compounds of hydrazine derivatives with transition metals. Part 27. Coordination chemistry of 4-amino-3-alkyl-5-thio-1,2,4-triazolines and 4-amino-5-oxo-3-thioxo-6-alkyl-2,3,4,5-tetrahydro-1,2,4-triazines

Summary Mono-, bis- and tris-ligand nickel(II) and cobalt(II) complexes with 4 amino-3-alkyl-5-thio-1,2,4-triazolines (HRL) (R=H, Me, or Et) and 4-amino-5-oxo-3-thioxo-6-methyl-2,3,4,5-tetrahydro-1,2,4-triazine (HL') have been prepared and characterized. In these complexes both HRL and HL' are in the neutral thione form. Nickel(II) and cobalt(II) complexes with mononegative thiolate ligands have been also isolated.The reaction of HL' with copper(II) salts in a molar ration of 11 results in the formation of [Cu(HL')X] (X=Cl or Br) and Cu(L')X (X=NO₃ or CH₃COO). However, in the presence of a large excess of HL' the reaction proceeds with partial reduction of Cu^II and both [Cu(HL')X₂] and [Cu(HL')₂]X have been isolated and characterized. The mechanism of copper(II) reduction by HL' is discussed.     

The bridged effect on the geometric,optoelectronic and charge transfer properties of the triphenylamine–bithiophene-based dyes: a DFT study

Research on Chemical Intermediates - The dye-sensitized solar cells containing a triphenylamine unit as the electron donor connected with a terminal cyanoacrylic acid electron acceptor by...     

Coordination compounds of transition metal hydrazine derivatives. Part 25. Monohydrazine-S-methylcarbodithioate schiff bases derived from α-dicarbonyl compounds

Summary The monohydrazones derived from the condensation of diacetyl and benzil with hydrazine-S-methylcarbodithioate (Dahydth) and (Benhydth) were prepared and their ligation properties with nickel(II), copper(II), palladium(II), zinc(II) and cadmium(II) were studied. A series of bisligand chelates were isolated and characterized. In the zinc(II), cadmium(II) copper(II) and palladium(II) bisligand chelates, both Dahydth and Benhydth act as mononegative bidentate molecules. The Ni(Dahydth-H)₂ chelate possesses an octahedral structure where Dahydth acts as a mononegative tridentate ligand. The¹H n.m.r. spectra of the two ligands as well as of the diamagnetic metal(II) chelates are discussed. The fragmentation in a mass spectrometer of all these chelates was also studied.     

Bis-[2(1-methyl-2-oxo-propyliden)-Hydrazin-S-methyl-dithiocarboxylat]-Nickel(II) Darstellung,IR-spektroskopische Daten und Kristallstruktur

Bis-[2 (1 -methyl-2-oxopropylidene)-hydrazine-S-methylcarbodithiolate] Nickel(II); Preparation, I.R. Data, and Crystal Structure The complex NiL₂ (L ? CH₃C(O)CCH₃NNC(S)SCH₃^?), prepared from Ni^II acetate and the Schiff base of hydrazine-carbodithioic acid methyl ester with diacetyl, crystallizes in the triclinic space group P1 with two formula units per unit cell. The cell dimensions are a = 986.1, b = 853.5, c = 1 314.5 pm and α = 113.48°, β = 95.5° and γ = 106.72°. A crystal structure determination (2 208 observed unique reflexions, R = 4.2%) showed two tridentate ligands to coordinate to one Ni atom by one oxygen, one nitrogen and one sulfur atom each, forming a distorted octahedron. The atoms of each ligand are approximately coplanar and the two planes are perpendicular to each other. I.r. data are reported and discussed.     

Coordination compounds of hydrazine derivatives with transition metals. Part 26. Coordination properties of α-diketone and α-ketoaldehyde bishydrazones derived from hydrazine-S-methylcarbodithioate

Summary Metal(II) chelates with -diketone and -ketoaldehyde bishydrazones derived from hydrazine-S-methylcarbodithioate with the general formula M[-dik(hydth)₂-2H] (M=Zn^II, Cd^II, Ni^II, Cu and Pd^II) were prepared and characterized by i.r., electronic and mass spectra as well as magnetic properties. The Ni^II, Zn^II and Cd^II chelates are most probably pentacoordinated dimers whereas the Cu^II chelates are polymeric through Cu-S linkages. The Pd^II chelates are square planar monomers.     

Aspects of surface modification, structure characterization, thermal stability and metal selectivity properties of silica gel phases-immobilized-amine derivatives

Four silica gel phases-bound-amine derivatives (I-IV) were prepared based on chemical immobilization technique. The surface modification was identified by determination of the coverage values in mmol g⁻¹ via thermal desorption method (1.463-1.807) and elemental analysis of nitrogen and carbon contents (1.089-2.456). Structure characterization related to immobilization of the amine derivatives was accomplished and evaluated by means of infrared (IR) and secondary ion mass spectrometric (SIMS) technique. The modified silica gel phases (I-IV) along with their interaction products with copper(II) were also examined by electron impact mass spectrometric analysis (EI-MS) as a method for evaluation of their thermal stability and structure elucidation. Potentiometric titration as a method of characterization was applied for the modified silica gel phases (II-IV) and their copper(II)-adduct. A series of bi- and trivalent metal ions were selected to focus more aspects of the selectivity properties incorporated into the modified silica gel phases for binding and interaction with these metals based on determination of the distribution coefficient and separation factor. The results of these evaluation processes were found to prove higher selectivity and preference of these four phases for binding with lead(II) and cadmium(II) compared to other metal ions.     

Mo2O3Cl4(Pyridin)4 · CH2Cl2 Synthese,IR-Spektrum und Kristallstruktur

Mo₂O₃Cl₄(Pyridine)₄ · CH₂Cl₂. Synthesis, IR Spectrum, and Crystal Structure Reduction of MoO₂Cl₂(pyridine)₂ with triphenylphosphane in toluene and recrystallisation from CH₂Cl₂ yields brown crystal needles of the complex Mo₂O₃Cl₄(pyridine)₄ · CH₂Cl₂. The compound crystallizes monoclinic in the space group P2₁/c with four formula units per unit cell of the dimensions a = 1 234.6 pm; b = 1 593 pm, c = 1 522.3 pm and β = 105.66° A structural investigation by X-ray methods (3 276 independent observed reflexions, R = 0.033) reveals the molecule with two molybdenum atoms in a distorted octahedral coordination linked by an almost linear Mo? O? Mo bridge with bond distances of 167 and 168 pm, respectively. The chlorine atoms are located in trans-position to the oxygen atoms which have different trans effects: The Mo? Cl bond opposite the bridge (length 242 pm) is 8 pm shorter than the bond in trans position to the terminal oxo ligands. The pyridine nitrogen atoms are in trans position to each other and complete the coordination of the molybdenum atoms. The i.r. spectrum of the compound is reported.