Tetracyanoethylene Complexes Research Articles

Infrared spectroscopic determination of the degree of charge transfer in complexes of TCNE with methyl-substituted benzenes

The position of the CN stretching frequency in infrared spectra of tetracyanoethylene (TCNE) complexed with methyl-substituted benzenes is used to determine the fraction of charge transferred from the electron donor to the acceptor.

Substituent Effects in S- and Se-Centered Radical Cations

The first ionization potentials of molecules XZY and 1,4-XC6H4ZR (X, Y are inorganic, organo- metallic, or organic substituents; Z = S, Se), as well as the energies of charge-transfer bands in the electronic spectra of tetracyanoethylene complexes of these molecules are determined by the inductive, resonance, and polarization effects of substituents X and Y. Z-Centered radical cations formed both from individual molecules in the gas phase and from those incorporated in tight radical ion pairs in solutions are closely allied in their electronic structure. The resonance parameters σ+R of organosilicon, organogermanium, and organotin substituents bound to the radical cation center Z+· were determined.

Theoretical investigation of charge transfer excitation and charge recombination in acenaphthylene–tetracyanoethylene complex

AbstractAb initio calculations were performed to investigate the charge separation and charge recombination processes in the photoinduced electron transfer reaction between tetracyanoethylene and acenaphthylene. The excited states of the charge‐balanced electron donor–acceptor complex and the singlet state of ion pair complex were studied by employing configuration interaction singles method. The equilibrium geometry of electron donor–acceptor complex was obtained by the second‐order Møller–Plesset method, with the interaction energy corrected by the counterpoise method. The theoretical study of ground state and excited states of electron donor–acceptor complex in this work reveals that the S1 and S2 states of the electron donor–acceptor complexes are excited charge transfer states, and charge transfer absorptions that corresponds to the S0 → S1 and S0 → S2 transitions arise from π–π* excitations. The charge recombination in the ion pair complex will produce the charge‐balanced ground state or excited triplet state. According to the generalized Mulliken–Hush model, the electron coupling matrix elements of the charge separation process and the charge recombination process were obtained. Based on the continuum model, charge transfer absorption and charge transfer emission in the polar solvent of 1,2‐dichloroethane were investigated. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 23–35, 2003

A Density Functional Study of C60 Transition Metal Complexes

Density functional calculations have been performed on (PH3)2M(η2-C60) (M = Ni, Pd, Pt) complexes. The optimized geometries have been found in good agreement with the X-ray experimental data. The electronic structure has been analyzed in terms of the Chatt−Dewar−Duncanson model, and the contribution from π back-donation was found to dominate over that from σ donation for all three complexes. Reliable values for the metal fullerene bond dissociation energies have been calculated and found higher than the corresponding metal ethylene complexes, but lower than metal tetrafluoro- and tetracyanoethylene complexes.

Donor−Acceptor Complexes of Alkylcarbazole and Dicarbazolylalkane Donors with the Acceptors Tetracyanoethylene and Tetranitromethane

Electron donor−acceptor complexes of conformationally flexible 1,n-dicarbazolylalkanes (C12H8N−(CH2)n−NC12H8), where n = 1−5, were examined. Carbazole, methylcarbazole, ethylcarbazole, and cyanoethylcarbazole also were studied as monochromophoric analogues for comparison. In dichloromethane solution, the dicarbazolylalkanes form 1:1 complexes with the terminal carbazolyl chromophores acting as independent donors when n ≥ 2. With the acceptor tetranitromethane (TNM), the carbazoles form contact complexes displaying small positive enthalpies of formation. In contrast, stable complexes form with the acceptor tetracyanoethylene (TCNE). Crystalline TCNE complexes were isolated for the bichromophoric donors with n = 2−4. The solid complexes and their uncomplexed donor components were analyzed by single-crystal X-ray diffraction. The solid-state stoichiometries of (carbazolyl donor):(TCNE acceptor) were found to depend on the donor conformation. Dicarbazolylalkane donors separated by two or four methylene units ...

Charge transfer in complexes of C60 and C70 in solutions and solid state

Electronic absorption spectra of complexes of C60 and C70 fullerenes with donors, tetrathiafulvalene and pyranylidene derivatives, were studied in solutions and in the solid state. Charge transfer bands were found in the 680–1300 nm range. The charge transfer energies (hv ct) for the C60 and C70 complexes in solutions are close and almost independent of the solvent polarity. For the C60 complexes in the solid state, the dependence ofhv ct on the ionization potential (IP) of donors was found to behv ct=0.82IP–3.93 eV. In the C60 complexes in the solid state, thehv ct values are 0.15–0.20 eV lower than those in the solution. The linear dependences ofhv ct onIP of donors for the C60 complexes lie 0.6–0.7 eV higher than those in the complexes with tetracyanoethylene (TCNE). This is associated with lower values of the electron affinity of C60 and the energy of the electrostatic interaction in the fullerene complexes as compared to those of the TCNE complexes.

The Study of π–π Interaction in Layered [3.3]Orthocyclophanes. Charge-Transfer Complexes of [3.3]Orthocyclophanes with Tetracyanoethylene

Abstract Dibenzo[3.3]orthocyclophanes ([3.3]OCPs) with a bicyclo[4.4.1]undecane substructure form charge-transfer (C-T) complexes with tetracyanoethylene (TCNE). 3,4 : 8,9-Dibenzobicyclo[4.4.1]undecane (9) and its 11-methylene derivative 8 are flexible molecules and take a chair-boat conformation. Complexes 8- and 9-TCNE exhibit the absorption maximum at ca. 420 nm, which coincides with the value for the TCNE complex of o-xylene. On the other hand, acetal 5, methylcarbinol 6, and dimethylmethylene derivative 7 are rigid, layered [3.3]OCPs with stacked benzene rings. Compounds 5, 6, and 7 form a 1 : 1 complex with TCNE in solution. The absorption maxima of the complexes at ca. 500 nm suggest an enhanced C-T complexation due to a π–π through-space interaction in 5, 6, and 7. A 2 : 1 complex of rigid [3.3]OCP 7 with TCNE crystallized from dichloromethane, while OCP 8 gave a red crystalline 2 : 3 complex with TCNE. X-ray crystallographic analyses of these two complexes is given.

Iron dinitrosyl complexes of TCNE: a synthetic, X-ray crystallographic, high field NMR and electrochemical study

Treatment of Fe(NO) 2[PR 3](CO) with tetracyanoethylene (TCNE) in diethyl ether leads to the formation of Fe(NO) 2[PR 3]( η 2-TCNE), where PR 3=P(OCH 3) 3, 1, P( n-Bu) 3, 2, PMe 2Ph, 3, and PEt 2Ph, 4. An X-ray crystallographic study of 1 shows the iron to be situated in a nearly tetrahedral environment with a π-bonded tetracyanoethylene and two linearly bound nitrosyl groups. From the ambient-temperature NMR spectral data, it is evident that there exist two non-equivalent cyanocarbon environments, indicating that the rotation about the Fe-TCNE π-bond is slowed at room temperature; variable-temperature NMR studies on Fe(NO) 2[P(OMe) 3]( η 2-TCNE), 1, yielded an activation energy barrier of approximately 18.1±0.5 kcal mol −1 for this rotational process. Electrochemical studies revealed that the neutral Fe(NO) 2[PR 3]( η 2-TCNE) complexes undergo irreversible reductions at positively shifted potentials, relative to the related Fe(NO) 2[PR 3](CO) complexes. Moreover, a trend toward cathodic shift of the reduction potentials with increasing phosphine p K a has been observed. The high energy barrier for alkene rotation and the shift towards positive reduction potentials are rationalized in terms of a strong π-interaction between the iron center and TCNE.

Magnetic properties of charge transfer complexes of manganese porphyrin derivatives and tetracyanoethylene

A series of charge transfer complexes between tetracyanoethylene and manganese(II) tetraphenylporphyrin derivatives with redox potentials (E ° (Mn 3+/2+)) ranging from −0.23 through −0.08 V vs. SCE, were prepared. The magnitude of the charge transfer decreased with the more anodically shifted redox potentials of the porphyrins which have stronger electron withdrawing groups, in the order of phenyl, 4-methoxyphenyl, 2-thienyl, and 4-cyanophenyl substituents at meso positions. The magnitude of the charge transfer reflected in frequency shift of CN vibration of the TCNE. The magnetization curves at very low temperature showed hysteresis. The salt with cathodically-shifted E ° (Mn 3+/2+) has a lower Curie temperature (Tc). In other words, the degree of the charge transfer between TCNE and Mn porphyrin responsible for the high T C value.

Charge–transfer excitation of electron donor–acceptor complexes of arylcyclopropanes

Electron-transfer (ET) reactions of mono- and di-arylcyclopropanes 1 and 2 have been investigated by employing charge-transfer (CT) excitation of their electron donor–acceptor (EDA) complexes with tetracyanoethylene (TCNE) or p-chloranil (CA). For the TCNE complexes, no reaction is observed following photoexcitation within their CT bands. Picosecond absorption spectroscopic experiments with phenylcyclopropane 1a and 1,1-diphenylcyclopropane 2a reveal that the photogenerated ion radical pairs [1a˙+, TCNE˙-] and [2a˙+, TCNE˙-] are too short-lived to undergo chemical reaction. For the CA complexes, net chemical change is observed in the CT excitation of the 2a–CA complex though the efficiency is very low. The other arylcyclopropane–CA complexes are found to be unreactive. Factors concerned with the reactivity of 1 and 2 upon their CT-excitation are discussed.

Palladium(0)–tetracyanoethylene complexes of diphosphines and a dipyridine with large bite angles, and their crystal structures

M. Kranenburg, J. G. P. Delis, P. C. J. Kamer, P. W. N. M. van Leeuwen, K. Vrieze, N. Veldman, A. L. Spek, K. Goubitz and J. Fraanje, J. Chem. Soc., Dalton Trans., 1997, 1839 DOI: 10.1039/A607927J

ChemInform Abstract: Charge‐Transfer Complexes of Tetracyanoethylene with Alkyl and Aryl Derivatives of the Halogens

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.

Optimized Electron Transfer in Charge-Transfer Ion Pairs. Pronounced Inner-Sphere Behavior of Olefin Donors

Time-resolved (fs) spectroscopy allows the direct observation of charge-transfer ion pairs resulting from the photoexcitation of the electron donor−acceptor (EDA) complexes of tetracyanoethylene with various olefin donors, i.e., [olefin, TCNE], in dichloromethane solutions. Measurement of the spectral decays yields first-order rate constants for electron transfer (kET) in the collapse of the charge-transfer ion pairs [olefin•+, TCNE•-] by very rapid return to the ground-state EDA complex at 25 oC. [These ultrafast ET rates necessitated the design/construction of a new tunable, high-power pump−probe spectrometer based on a Ti:sapphire laser with 250-fs resolution.] The value of kET = 5 × 1011 s-1 is strikingly nonvariant for the different TCNE complexes despite large differences in the driving force for electron transfer (ΔG0), as evaluated from the varying ionization potentials of the olefins. Such a unique nonvariant trend for the free energy relationship (log kET versus ΔG0) is analyzed in terms of a dominant inner-sphere component to electron transfer. In a more general context, the inner-sphere (adiabatic) electron transfer in [olefin•+, TCNE•-] relates to a similar, but less pronounced, inner-sphere behavior noted in the analogous [arene•+, TCNE•-] radical-ion pairs. As such, these electron-transfer processes represent an extremum in the continuum of ET transition states based on the inner-sphere/outer-sphere dichotomy.

Charge-Transfer Complexes of Tetracyanoethylene with Alkyl and Aryl Derivatives of the Halogens

Spectral characteristics (λCT, Δν1/2, and e) and association constants (in dichloromethane) of charge-transfer (CT) complexes of tetracyanoethylene (T) with donors containing C−X linkages (X = F, Cl, Br, and I) are presented. The donor orbitals from which CT transitions originate are identified by correlation of λCT and Δν1/2 values of CT bands of the complexes with the ionization bands of the photoelectron spectra of the donor molecules. CT energies of the complexes are influenced by intramolecular conjugative and inductive effects between halogen atoms and alkyl and aryl groups. Haloalkanes form weak complexes with T through interaction of the px and py orbitals of the halogen with the π* LUMO of T. Monoiodoalkane−T complexes exhibit two spectral bands arising from the transfer of nonbonded electrons from the 5p orbitals of iodine which are split into 2E1/2 and 2E3/2 states through spin−orbit coupling. λ1 and λ2 values of monoiodoalkanes increase progressively with increasing bulk of the alkyl group. Ha...

Charge-Transfer Complexes of Tetracyanoethylene with Alkyl and Aryl Derivatives of Sulfur, Selenium, and Tellurium

Charge-Transfer Complexes of Tetracyanoethylene with Alkyl and Aryl Derivatives of Sulfur, Selenium, and Tellurium

Molecular Complexes of Macrocyclic Polyamines with π-Electron Acceptors

Abstract The charge-transfer interaction of macrocyclic polyamines 1,4,8,11-tetraazacyclotetradecane (TACTD); 1,4,8,12-tetraazacyclopentadecane (TACPD) and 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (TMTACTD) with chloranil (CHL), tetracyanoethylene (TCNE) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as π-electron acceptors was investigated spectroscopically. Spectral characteristics and stability constants of formed CT complexes are examined and discussed in terms of molecular structure of both electron donor and acceptor as well as solvent polarity. It is deduced that the CT complexes are of strong kind where macrocyclic polyamines-DDQ, TMTACTD-TCNE, -CHL complexes essentially exist in the dissociated state (radical cations and anions D+, A−). On the other hand, the TCNE and CHL complexes with TACTD and TACPD exist in a dative structure (D+-A−). Solid 1:1 CT complexes are synthesized and characterized.

Formation Constants of Radical-Ion Pairs and Charge-Transfer Complexes of Tetracyanoethylene with Group 8 Metallocenes

Formation constants K i of radical-ion pairs and K c of charge-transfer (CT) complexes of tetracyanoethylene (T) with ferrocene and ruthenocene and some of their alkyl derivatives in dichloromethane (DCM) are presented. The spectra of some alkylmetallocene/T/DCM systems simultaneously exhibit CT bands for the feeble n-covalent complex and bands for the radical-ion pairs which follow electron transfer. K i and K c are calculated using a modified form of the Benesi-Hildebrand equation

ChemInform Abstract: Charge‐Transfer Complexes of Tetracyanoethylene with Alkyl, Alkenyl, and Aryl Derivatives of Oxygen

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.

Charge-Transfer Complexes of Tetracyanoethylene with Alkyl, Alkenyl, and Aryl Derivatives of Oxygen

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCharge-Transfer Complexes of Tetracyanoethylene with Alkyl, Alkenyl, and Aryl Derivatives of OxygenJohn E. Frey, Theresa Aiello, Douglas N. Beaman, Scott D. Combs, Shi-lin Fu, and Jeffrey J. PuckettCite this: J. Org. Chem. 1994, 59, 7, 1817–1830Publication Date (Print):April 1, 1994Publication History Published online1 May 2002Published inissue 1 April 1994https://doi.org/10.1021/jo00086a037RIGHTS & PERMISSIONSArticle Views140Altmetric-Citations19LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Electronic structure of the benzene–tetracyanoethylene complex: A synthesis of molecular orbital and density functional descriptions

AbstractThe electronic structure of the benzene–tetracyanoethylene electron donor–acceptor complex is investigated at the HF/6‐311G** level of theory. The computed electronic wave function is analyzed with rigorous interpretive tools that involve both molecular orbital and density functional approaches. The in situ electronegativity difference is calculated at 3.32 eV, resulting in a charge transfer of 0.016. This extent of charge transfer is found to account for only ca. 17% of the interaction energy of ca. 33% of the dipole moment. The remaining part of the dipole moment originates from buckling of the tetracyanoethylene moiety. The dependence of the electronegativity difference on the magnitude of charge transfer is found to be highly nonlinear. © 1994 John Wiley & Sons, Inc.