CHARGE-TRANSFER COMPLEXES OF BIPHENYLENE

1966 ◽  
Vol 44 (1) ◽  
pp. 9-12 ◽  
Author(s):  
P. H. Emslie ◽  
R. Foster ◽  
R. Pickles
Keyword(s):  
Charge Transfer ◽  
Charge Transfer Complex ◽  
Equilibrium Constants ◽  
Charge Transfer Complexes ◽  
Kcal Mole ◽  
Dichloromethane Solution ◽  
Entropy Of Formation ◽  
Charge Transfer Transitions ◽  
Different Temperatures ◽  
Enthalpy And Entropy

An attempt has been made to redetermine the enthalpy and entropy of formation of the charge-transfer complex between tetracyanoethylene and biphenylene in dichloromethane solution from measurements of the equilibrium constant at different temperatures. The results obtained under conditions where biphenylene is in excess differ from those previously published in which tetracyanoethylene was in excess. It is argued that the optimum condition for determining equilibrium constants of a 1:1 complex is when the reactants are mixed in solution in this ratio. Determinations under this condition yield ΔH = −2.6 kcal mole−1 and ΔS = −4.1 e.u.The energies of the intermolecular charge-transfer transitions of biphenylene with several different acceptors suggest that the ionization potential of biphenylene is ~7.4 eV.

Evaluation of thermodynamic parameters on higly correlated chemical systems: a spectrophotometric study of the 1:1 and 1:2 equilibria between I2 and R4todit = 4,5,6,7-tetrathiocino[1,2-b:3,4-b′]diimidazolyl-1,3,8,10-tetraalkyl-2,9-dithione; (R = Bu, Me (new data); Et, Ph (reinvestigation)). Crystal and molecular structure of the charge-transfer complex Bu4 todit•2I2

1995 ◽  
Vol 73 (3) ◽  
pp. 380-388 ◽  
Author(s):  
Francesco Bigoli ◽  
Maria Angela Pellinghelli
Keyword(s):  
Molecular Structure ◽  
Charge Transfer ◽  
Standard Enthalpy ◽  
Charge Transfer Complexes ◽  
X Ray ◽  
Entropy Changes ◽  
Different Temperatures ◽  
Enthalpy And Entropy Changes ◽  
Enthalpy And Entropy ◽  
Absorbance Data

The reactions between Bu4todit and I2 in CHCl3 solution have been investigated by spectrophotometry at different temperatures. Evidence for the stepwise formation of the 1:1 and 1:2 charge-transfer complexes has been obtained by computer analysis of the experimental data. The stability constants of both complexes and the corresponding standard enthalpy and entropy changes have been calculated. The 1:2 complex has been characterized in the solid state by an X-ray structural study: the crystals of Bu4todit 2I2 are monoclinic, space group C2/c, a = 16.352(6), b = 9.376(5), c = 23.470(7) Å, β = 99.78(2)°, Z = 4,R = 0.0579. The molecular structure shows that the two thionic sulfur atoms coordinate two diiodine molecules, the bond distances and angles being similar to those observed previously in Et4todit•2I2. On the contrary, the solution studies disagree with the previous investigations on Et4todit and Ph4todit, where the absorbance data were explained assuming the formation of the 1:1 complex only. A new calculation procedure for the least-squares minimization of spectrophotometric data, based on Powell's direct search method, has been developed. This procedure allows for the refinement of the standard enthalpy and entropy changes from a set of absorbance data at different temperatures. Convergence has been attained for the reaction of diiodine with Bu4todit and Me4todit (new data) and also for Et4todit and Ph4todit (old data). Keywords: equilibrium constants, charge-transfer complexes, Fourier transform – Raman, X-ray, I2-thioamides.

Charge-Transfer Complexes of Brominated Polycyclic Aromatic Hydrocarbons

1962 ◽  
Vol 15 (2) ◽  
pp. 278 ◽  
Author(s):  
TM Spotswood
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Charge Transfer ◽  
Aromatic Hydrocarbons ◽  
Charge Transfer Complex ◽  
Equilibrium Constants ◽  
Molecular Complexes ◽  
Charge Transfer Complexes ◽  
Extinction Coefficients ◽  
Polycyclic Aromatic ◽  
Molar Extinction Coefficients

Charge-transfer complex formation between the donors 1-bromonaphthalene. 9-bromophenanthrene, 9-bromoanthracene, 3-bromopyrene, and 7-bromobenz[a]-anthracene and the acceptors iodine, tetrachlorophthalic anhydride, 1,3,5-trinitrobenzene, and 2,4,7-trinitrofluorenone has been investigated. The positions of the charge-transfer absorption maxima, apparent molar extinction coefficients, and equilibrium constants have been determined in carbon tetrachloride solution and the results compared with those for the corresponding unsubstituted polycyclic aromatic hydrocarbons. The positions of the absorption maxima of the charge-transfer bands of the brominated hydrocarbons were anomalous but the apparent molar extinction coefficients and equilibrium constants were similar to those obtained for the parent hydrocarbons. The strength of charge-transfer bonding in molecular complexes of brominated polycyclic aromatic hydrocarbons is shown to be of the same order as that in molecular complexes of the unsubstituted hydrocarbons.

A study of the donor properties of the phenoxachalcogenines II: 7,7,8,8-tetracyanoquinodimethane as the acceptor

1980 ◽  
Vol 58 (11) ◽  
pp. 1133-1137 ◽  
Author(s):  
David P. Rainville ◽  
Ralph A. Zingaro ◽  
John P. Ferraris
Keyword(s):  
Free Energy ◽  
Charge Transfer ◽  
Room Temperature ◽  
Charge Transfer Complex ◽  
Equilibrium Constants ◽  
Entropy Change ◽  
Charge Transfer Complexes ◽  
Chalcogen Atom ◽  
Dc Conductivities ◽  
Type Interaction

The phenoxachalcogenines have been studied as donors towards 7,7,8,8-tetracyanoquinodimethane. For the 1:1 complexes studied, the equilibrium constants, K, vary over the range 4–6; the enthalpy, ΔH0, is about −2.0 kcal/mol; the free energy, ΔG0, is −1.4 to −1.0 kcal/mol, and the entropy change, ΔS0, is −7.3 to −3.5 eu. The entropy change is greatest in the case of the dibenzo-1,4-dioxane – 7,7,8,8-tetracyanoquinodimethane charge-transfer complex. This is attributed to the planarity of the dibenzo-1,4-dioxane molecule. The extinction coefficient, εc, for the series studied varies from 115 to 230, and no regularity in the trend has been noted.The lack of any significant changes (with change in the chalcogen atom) in the thermodynamic values for the phenoxachalcogenine – 7,7,8,8-tetracyanoquinodimethane charge-transfer complexes is interpreted in terms of a similar π to π type interaction involving a delocalized π orbital of the phenoxachalcogenine rather than a localized n orbital of the hetero atom.The room temperature four-probe dc conductivities of single crystals of PSe–TCNQ and PS–TCNQ were found to be 4 × 10−8 and 3 × 10−7 ohm−1 cm−1, respectively.

Charge-transfer interaction of bithienyls and some thiophene derivatives with electron acceptors

1976 ◽  
Vol 54 (23) ◽  
pp. 3705-3712 ◽  
Author(s):  
Rafie Abu-Eittah ◽  
Fakhreia Al-Sugeir
Keyword(s):  
Charge Transfer ◽  
Complex Formation ◽  
Molecular Complexes ◽  
Formation Constants ◽  
Electron Acceptors ◽  
Charge Transfer Complexes ◽  
Extinction Coefficients ◽  
Charge Transfer Transitions ◽  
Different Temperatures ◽  
Thiophene Derivatives

The charge transfer complexes of 2,2′-bithienyl, 5,5′-dimethyl-2,2′-bithienyl, and some thiophene derivatives as donors with tetracyanoethylene as an acceptor have been studied spectrophotometrically. In addition, complexes of the first donor with chloranil and iodine have been studied. The formation constants and extinction coefficients of the molecular complexes formed have been determined by graphical as well as iterative methods. From measurements at different temperatures, the thermodynamic functions of the complex formation have been calculated. The ionization potentials of the donors have been obtained from the energies of the charge transfer transitions.

Chemical shifts of charge-transfer complexes and Buckingham equation

1990 ◽  
Vol 55 (9) ◽  
pp. 2131-2137
Author(s):  
Mahboob Mohammad ◽  
Ather Yaseen Khan ◽  
Tariq Mahmood ◽  
Ismat Fatima ◽  
Riffat Shaheen ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Nmr Spectra ◽  
Charge Transfer Complex ◽  
Chemical Shifts ◽  
Charge Transfer Complexes ◽  
Aprotic Solvents ◽  
Reaction Field ◽  
H Nmr ◽  
Spherical Cavities ◽  
Dipolar Aprotic Solvents

The 1H NMR spectra of the charge-transfer complex of 1-ethyl-4-methoxycarbonylpyridinium iodide have been recorded in various dipolar aprotic solvents. An attempt is made to interpret the chemical shifts in terms of Buckingham's reaction field equation for spherical cavities. A linear dependence has been found between the δ(2,6) values and the square of dielectric function for a spherical cavity, which confirms the validity of the Buckingham equation for this class of compounds.

Gelification Effects on the Structure and Birefringence of Charge Transfer Complex Terthiophene Bisililated – TCNQ Hybrid Materials

2006 ◽  
Vol 517 ◽  
pp. 257-261
Author(s):  
N. Kancono ◽  
H.B. Senin
Keyword(s):  
Charge Transfer ◽  
Detection Limit ◽  
Hybrid Materials ◽  
Vibrational Spectra ◽  
Lamellar Structure ◽  
Radical Anion ◽  
Charge Transfer Complex ◽  
Visible Spectrum ◽  
Charge Transfer Complexes

Charge transfer complexes (CTC) can be readily introduced into materials by cohydrolysis-copolymerisation of bis-silylated ter-thiophenes as precursors with TMOS and TEOS in the presence of TCNQ. CTC formation is shown in the visible spectrum of the xerogel by the band at 850 nm characteristic of the TCNQ·- radical anion. Vibrational spectra have shown that strong vibration of C≡N bond at 2184, 2120 and 1595 cm-1 as peaks characteristics of CTC. The CTC bands are weak and the complex is easily destroyed by washing with acetone, which removes the TCNQ. The gelification effect of the charge transfer complexes on the hybrid materials of 2,5’’- bis(trime thoxysilyl)terthiophene/TCNQ/ TMOS showed that the peak with distance of more than 11.68 Å, formed by precursors and matrices, as a lamellar structure. The birefringence of xerogel BTS3T in presence of alkoxysilane showed that the value is near the detection limit of 0.1 – 0.4 x 10-3, which is weaker than BTS3T / THF with the birefringence value of 4.5 x 10-3.

scholarly journals Fermi level pinned molecular donor/acceptor junctions: reduction of induced carrier density by interfacial charge transfer complexes

2020 ◽  
Vol 8 (43) ◽  
pp. 15199-15207
Author(s):  
Paul Beyer ◽  
Eduard Meister ◽  
Timo Florian ◽  
Alexander Generalov ◽  
Wolfgang Brütting ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Fermi Level ◽  
Carrier Density ◽  
Charge Transfer Complex ◽  
Charge Transfer Complexes ◽  
Interfacial Charge Transfer ◽  
Fermi Level Pinning ◽  
Donor Acceptor ◽  
Interfacial Charge

Charge transfer complex (CPX) formation at a donor–acceptor interface reduces the amount of Fermi-level pinning induced interfacial charge transfer.

Determination of Equilibrium Constants for Weakly Bound Charge-transfer Complexes

1999 ◽  
Vol 69 (4) ◽  
pp. 443-447 ◽  
Author(s):  
Ramona Zaini ◽  
Andrew C. Orcutt ◽  
Bradley R. Arnold
Keyword(s):  
Charge Transfer ◽  
Equilibrium Constants ◽  
Charge Transfer Complexes ◽  
Weakly Bound

Application of time-resolved linear dichroism spectroscopy: Intensity borrowing in charge transfer complex absorption spectra

2003 ◽  
Vol 81 (6) ◽  
pp. 567-574
Author(s):  
Dustin Levy ◽  
Bradley R Arnold
Keyword(s):  
Charge Transfer ◽  
Charge Transfer Complex ◽  
Chlorinated Solvents ◽  
Linear Dichroism ◽  
Charge Transfer Transition ◽  
Time Resolved ◽  
Transition Energies ◽  
Charge Transfer Transitions ◽  
Donor Acceptor ◽  
Influence Of Solvent

Time-resolved linear dichroism spectroscopy has been used to study the influence of solvent on the charge transfer complex formed between hexamethylbenzene and 1,2,4,5-tetracyanobenzene. It was shown that cyano-substituted solvents induce a 1500 cm–1 increase in the charge transfer transition energies relative to those observed in chlorinated solvents. Furthermore, the angle between the charge transfer absorption transition moments and the photochemically produced radical anion absorption transition moment, after relaxation, has been measured for this complex in several solvents. A simple model was used to correlate the angles measured using time-resolved linear dichroism spectroscopy with the extent of localized excitation mixed into the charge transfer transitions. These measurements reveal that different charge transfer transitions borrow intensity from the localized excitation to different extents. By using different excitation wavelengths, the partitioning of the borrowed intensity among the charge transfer transitions of this complex could be evaluated for the first time.Key words: 1,2,4,5-tetracyanobenzene, hexamethylbenzene, donor–acceptor complex, photoinduced electron transfer, photoselection.

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