Compounds In Nonpolar Solvents Research Articles

Improving the Solubility of Hexanuclear Heterometallic Extended Metal Atom Chain Compounds in Nonpolar Solvents by Introducing Alkyl Amine Moieties.

The highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) interaction at the dz2 orbital between two kinds of metal complex is useful for obtaining heterometallic one-dimensional (1D) chains as well as heterometallic metal string compounds (HMSCs). Platinum dinuclear complexes, [Pt2(piam)2(NH2R)4]X2 (piam = pivalamidate, R = CH3, C2H5, C3H7, or C4H9, X = anion), comprising σ* as HOMO were mixed with [Rh2(O2CCH3)4] comprising σ* as LUMO in solvents to afford single crystals of [{Rh2(O2CCH3)4}{Pt2(piam)2(NH2R)4}2]X4 (2–5). Single-crystal X-ray analyses revealed that 2–5 are hexanuclear complexes that are one-dimensionally aligned as Pt–Pt–Rh–Rh–Pt–Pt with metal–metal bonds, where the alkyl moieties at end Pt atoms obstruct further 1D extension. Complexes 2–5 appear as if they are cut off from an infinite chain [{Rh2(O2CCH3)4}{Pt2(piam)2(NH3)4}2]n(PF6)4n·6nH2O (1) aligned as −{Pt–Pt–Rh–Rh–Pt–Pt}n–. The diffuse reflectance spectrum of 1 depicts broad shoulder bands, which are not present in the spectra of 2–5, proving that the infinite chain 1 forms a band structure. Compounds 4 and 5 with propyl or butyl moieties at amine ligands, respectively, are soluble in nonpolar solvents, such as CH2Cl2, without the dissociation of their hexanuclear structures. Taking advantage of their solubility, measurement of cyclic voltammetry in CH2Cl2 become possible, which shows the quasi-reversible oxidation and reduction waves at 4: Eox = 0.86 V and Ered = 0.69 V and 5: Eox = 0.87 V and Ered = 0.53 V.

Differently substituted benzothiadiazoles as charge-transporting emitters for fluorescent organic light-emitting diodes

Carbazolyl- and 1,2,3,4-tetrahydrocarbazolyl-substituted benzothiadiazoles were prepared by Pd-catalyzed Buchwald-Hartwig and Heck reactions. Photophysical, electrochemical, thermal, charge-transporting properties, and performance in organic light emitting diodes (OLEDs) of the derivatives with donor-π-acceptor-π-donor and donor-acceptor-donor structures are discussed. Photo- and electroluminescent properties of the studied compounds of carbazole and benzothiadiazole are very sensitive to their molecular structures. Their glass transition temperatures range from 145 to 191 °C. Investigation of photophysical properties revealed importance of intramolecular twisting on excited state deactivation. Emission of dilute solutions of the compounds in nonpolar solvents appears in the orange region with fluorescence quantum yields up to 0.6.4,7-(Di (1,2,3,4-tetrahydro)carbazolyl)-[2,1,3]-benzothiadiazole demonstrates phosphorescence and delayed fluorescence at room temperature. Solid-state ionization potentials of the materials range from 5.64 to 5.82 eV. The layer of 4,7-(di (tert-butyl)carbazolyl)-[2,1,3]-benzothiadiazole shows high hole drift mobility of 1.7 × 10−3 cm2/V·s at an electric field of 5.3 × 105 V/cm and relatively high electron drift mobility of 5.7 × 10−5 cm2/V·s at an electric field of 5.8 × 105 V/cm. Red OLEDs based of singlet emission with maximum external quantum efficiency values of 1.3 and 0.13% were achieved using new emitters. Much better electroluminescent performance was observed for the compound having donor-acceptor-donor structure relative to the compound with donor-π-acceptor-π-donor structure.

Supramolecular polymerization: a coarse grained molecular dynamics study.

A coarse-grained (CG) force field to model the self-assembly of benzene-1,3,5-tricarboxamide (BTA) class of compounds in nonpolar solvents has been developed. The model includes an intrinsic point dipole embedded on one of the CG beads so as to impart a macrodipole moment to the oligomer, one of its characteristic feature. Chemical specificity has been preserved by benchmarking against results, including dimerization and solvation free energies, obtained from an all-atom representation. Starting from a well-dispersed configuration in n-nonane, BTA molecules self-assemble to form one-dimensional stacks. Free energy (FE) changes for the various manner in which short oligomers can exchange between the assembled and the dispersed states have been calculated. These calculations show BTA to self-assemble via a downhill cooperative mechanism with a nucleus size of three.

Conformational Analysis and Intramolecular Interactions in Aminofluorobenzoic Acids

Some aminofluorobenzoic acids were studied to evaluate the power of the F···HO hydrogen bond and other interactions as driving forces of the conformational isomerism of these compounds. Despite the occurrence of this hydrogen bond in the 2-fluorinated derivatives, as well as attractive O/F nonbonding interactions and NH···O═C hydrogen bond, the O/O repulsion dictates the orientation of the carboxyl group. Unlike 2-fluorophenol, which is reported to not experience a F···HO hydrogen bond, 2-fluorobenzoic acid derivatives were calculated to exhibit such interaction, but it could not be monitored experimentally by means of F/H(O) coupling constant, because of the low solubility of these compounds in nonpolar solvents, the acidity of the carboxyl hydrogen, the small population of some conformers capable of exhibiting hydrogen bond, and the solute self-association in solution, which make their conformational equilibrium different from that in gas phase.

Development of a molecularly imprinted polymer for pyridoxine using an ion-pair as template

One of the main challenges in the molecularly imprinted polymers (MIP) field is the proper MIP design for water-soluble compounds because of appearance of serious drawbacks in polar solvents and insolubility of those compounds in non-polar solvents which are commonly used for MIP synthesis. In this work a novel and simple method for synthesis of molecularly imprinted polymers for a water-soluble compound was introduced. Pyridoxine was chosen as a target molecule and the ion-pair complex formed between pyridoxine ion (Py +) and dodecyl sulfate ion (DS −) was transferred into the chloroform via liquid–liquid extraction. Then polymerization was carried out in chloroform. The molecular mechanics and density functional theory were proposed to screen proper monomer. Binding energy, Δ E, of a template and a monomer as a measure of their interaction was considered. Ion-pair [Py +-DS −] was supposed as a template molecule and acrylic acid, methacrylic acid, allyamine, vinylpridine and 2-hydroxy ethyl methacrylate were as tested monomers. The MIP synthesized using acrylic acid showed the highest selectivity to pyridoxine as predicted from the Δ E calculation. The obtained MIP showed very high affinity against vitamin B6 in comparison to non-imprinted polymers (NIP). It was proved that the obtained MIP with introduced method was much better than that prepared in methanol as porogen. It was showed that the MIP prepared by this new method could be used as an adsorber for extraction and determination of pyridoxine in real and synthetic samples.

Infrared study of the acidic and basic forms of betaxolol

Betaxolol and its respective hydrochloride salt were studied in solution by computational calculations and infrared spectroscopy. The solution molecular conformations were taken to be the same as those exhibited by the compounds in the solid state given by X-ray diffraction and calculated after full geometry optimization by ab initio Hartree–Fock methods using the 6-31G(d) basis set. Infrared spectra of carbon tetrachloride solutions provide valuable information on the structure of the compounds in non-polar solvents at different concentrations.

Dipole Moments and Intermolecular Association of Some Carbonyl Compounds in Nonpolar Solvents

The aggregation of some aldehydes in nonpolar solvents was investigated using the static dielectric method. The molecular association of acetone and two of its derivatives (acetophenone and benzophenone) in cyclohexane solvent were also investigated by this method. Analysis of the static dielectric data for solution of these materials indicated a high molecular association. It was found that benzaldehyde and its derivatives have a strong tendency for antiparallel molecular association, whereas acetone and its derivatives have a tendency for parallel alignment. The experimental results show that there is a sensitive relationship between the molecular association and molecular structure of these materials. The influence of solvent on the molecular association of the solute molecules was studied and compared.

Semi-empirical PM3 calculations predict the fluorescence quantum yields (Φ) of 4-monosubstituted benzofurazan compounds

We have elucidated the relationship between the fluorescence quantum yield (Φ) of 4-monosubstituted benzofurazan (2,1,3-benzoxadiazole) compounds and the substituent group at the 4-position using a group of eleven such compounds. The absorption and fluorescence spectra of these compounds were measured in fifteen different solvents. Semi-empirical PM3 calculations were carried out to obtain the optimized geometry, energies, charges and dipole moments of this group in the ground and excited states. The S1–T2 energy gaps obtained from the PM3-CAS/CI calculations, which reflected the probability of S1→T2 intersystem crossing, related well to the fluorescence quantum yield (Φ) of the 4-monosubstituted benzofurazan compounds in nonpolar solvents. It also appeared that the decrease in the S1–T1 energy gaps was related to the change in the fluorescence quantum yield (Φ) due to solvent effects. In highly polar solvents, non-radiative S1→T1 intersystem crossing occurs, in addition to non-radiative S1→T2 intersystem crossing, in 4-monosubstituted benzofurazan compounds, as they have a larger dipole moment in the S1 state than in the T2 state. These studies have enabled us to predict the fluorescence quantum yield (Φ) for a series of 4-monosubstituted benzofurazan compounds.

Spectroscopic Observation of Contact Ion Pairs Formed from Photolyzed TMPD and TMB in the Presence of Halogenated Compounds in Nonpolar Solvents

Spectroscopic Observation of Contact Ion Pairs Formed from Photolyzed TMPD and TMB in the Presence of Halogenated Compounds in Nonpolar Solvents

Coulomb‐induced intramolecular exciplex formation in semiflexible donor‐bridge‐acceptor compounds in nonpolar solvents as a function of temperature

AbstractThe mechanism of exciplex formation of two donor‐bridge–acceptor compounds, both containing a strong donor ‐ acceptor pair interconnected by a piperidine ring, was studied in nonpolar solvents as a function of temperature. Fluorescence spectra at low temperature in methylcyclohexane show that in both compounds the exciplex is formed via the harpooning mechanism, i.e. long‐range charge separation leading to an extended charge‐transfer state, followed by Coulomb‐induced folding to the exciplex state. The kinetic link between these two emissive states could be established by studying their transient fluorescence curves. Furthermore, the activation energy of the folding process was estimated from the decay rates of the extended charge‐transfer state in various solvents. An interpretation of the observed activation energies in terms of Kramers theory is presented, which gives an indication of the relative importance of internal steric effects and solvent viscosity on the dynamics of the folding process.

ChemInform Abstract: Rates and Efficiencies of Contact‐Ion‐Pair Formation in Photolyzed Mixtures of TMPD with Halogenated Compounds in Nonpolar Solvents

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Rates and efficiencies of contact-ion-pair formation in photolyzed mixtures of TMPD with halogenated compounds in nonpolar solvents

Time variation of microwave dielectric absorption has been examined for photolyzed solutions of N,N,N,N'-tetramethyl-p-phenylenediamine (TMPD) admixed with halogen-containing compounds AX (AX=CCl 4 , C 2 H 5 I, C 2 H 5 Br, C 2 H 5 Cl, C 6 H 5 I, C 6 H 5 Br, C 6 H 5 Cl, C 6 H 2 F, and C 6 F 6 ) in nonpolar solvents (mostly benzene). In solutions with CCl 4 , C 2 H 5 I, C 6 H 5 I, C 6 H 5 Br, and C 6 H 5 Cl, the dielectric absorption signals show first-order growths with appreciable intensities, indicating formation of a contact ion pair (CIP) TMPD + X - (X denotes a halogen atom) by reactions of these compounds with the excited triplet state of TMPD

Photosensitized [2+2] cycloreversion reactions of arylated cage compounds in nonpolar solvents. Highly efficient adiabatic exciplex isomerization

Photosensitized [2+2] cycloreversion reactions of arylated cage compounds 1 to dienes 2 using several cyanoaromatics as sensitizers are reported. In acetonitrile, 1a, isomerized to 2a via an efficient cation-radical chain process. In contrast, the isomerization of 1a to 2a proceeded via an exciplex in benzene. Interestingly, the exciplex emission maximum observed in the fluorescence quenching by 1a was the same as that by 2a. Such a coincidence was also observed in a series of arylated cage compounds 1a-d and dienes 2a-d in various solvents. These observations together with the results obtained from reaction and exciplex emission quenching experiments clearly demonstrated the occurrence of adiabatic exciplex isomerization of 1 to 2. Efficiencies (A e ) of the adiabatic process obtained by comparing the intensities of the observed exciplex emissions with those of diene exciplex emissions were quite high and became almost quantitative in some cases. A e values were found to increase as (1) the oxidation potentials (E 1/2 ox ) of cage compounds 1a-d decreased, (2) the reduction potentials (E 1/2 red ) of sensitizers increased, and (3) the solvent polarity (E T ) increased

Intramolecular coordination in molecules of C 6H 5COOCH 2CH 2SiX 3 (X = F, Cl)

Silicon-substituted 2-benzoyloxyethylsilanes, C 6H 5COOCH 2CH 2SiX 3 with X = F, Cl, OCH 3 or 1 3 (OCH 2CH 2) 3N, have been synthesized for the first time. The molecules of compounds with X = F and Cl may exist in two forms, acyclic with a tetracoordinated silicon atom and cyclic with a six-membered ring and a pentacoordinated silicon atom. The cyclic form of the molecules C 6H 5COOCH 2CH 2SiX 3, with X = F, Cl, are present in solutions of these compounds in non-polar solvents, the proportion increasing with decreasing temperature.

Determination of the dipole moment of polar compounds in nonpolar solvents

An experiment is described in the determination of the dipole moment of polar compounds in nonpolar solvents.

Dielectric relaxation and group rotation of some dimethoxy compounds in non polar solvents from microwave absorption measurements

Article Dielectric relaxation and group rotation of some dimethoxy compounds in non polar solvents from microwave absorption measurements was published on January 1, 1982 in the journal Zeitschrift für Physikalische Chemie (volume 263O, issue 1).

Dielectric relaxation and group rotation of some dimethoxy compounds in non polar solvents from microwave absorption measurements

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Einfluß von Substituenten auf die Fluoreszenzquantenausbeute bei Donator-Akzeptor-substituierten trans-Stilbenen

Abstract For 4'-acceptor substituted 4-dimethylaminostilbenes 1 the fluorescence quantum yield φf increases in n-heptane and toluene with decreasing acceptor interaction (i.e. with decreasing polarity in the S1-state). At the same time, the lifetimes τf w change with φf so that kf n remains approximately constant. Changes in φf for compounds 1 result from a strong change of the rate constant ktp of radiationless deactivation. This is interpreted in terms of the decreased stabilization of the Si-state occurring with the increase in the polarity of the investigated compounds in non-polar solvents, and remains in good agreement with the calculations carried out previously.

Quenching of aromatic triplet states in solution by nitric oxide and other free radicals

The rate constants for quenching of aromatic hydrocarbon triplets by nitric oxide and by the free radical di-t-butyl nitroxide have been measured by the laser flash photolysis technique. For low energy triplets the efficiency of quenching is inversely proportional to triplet energy. At high triplet energy the rates are proportional to triplet energy and there is a large effect of solvent polarity.These data are analysed in terms of an enhanced intersystem crossing process catalysed by the doublet state nitric oxide molecule. The data are shown to be consistent with important contributions from charge-transfer interactions for high triplet energy compounds in non-polar solvents.

Metal complexes of sulphur ligands. Part II. Reaction of bis(diphenylphosphinodithioato)-platinum(II) and -palladium(II) with ligands containing group VB atoms

Reaction of Pt(S2PPh2)2 with tertiary phosphines (PPh3, PMePh2, PMe2Ph) gives crystalline 1 : 1 and 1 : 2 adducts. With triphenylarsine or triphenylstibine, only 1 : 1 adducts can be isolated and with pyridine, i.r. evidence indicates that the 1 : 1 adduct is only stable in solution in the presence of an excess of pyridine. As reported earlier for the analogous palladium compounds, the 1 : 2 adducts rapidly dissociate to the 1 : 1 compounds in non-polar solvents (benzene or carbon disulphide); however, it is now found that they can be stabilised in more polar solvents (dichloromethane or nitromethane). Conductivity measurements in the latter suggests all these 1 : 2 adducts have a four-co-ordinate ionic structure and this is confirmed by an X-ray analysis of [Pd(S2PPh2)(PEt3)2]S2PPh2. An X-ray analysis on [Pd(S2PPh2)2(PPh3)] suggests a four-co-ordinate monomeric structure for the 1 : 1 compounds with uni- and bi-dentate co-ordination of dithioacid ligands. Finally, an empirical i.r. method for distinguishing unidentate, bidentate, and ionic modes of co-ordination of the diphenylphosphinodithioato-group to platinum and palladium is discussed.