Semiempirical and Density Functional Thoery Study on Structure of Fluoromethylfuran Oligomers (original) (raw)
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Journal of Fluorine Chemistry, 2007
Structural and electronic properties of oligomers including dimer, trimer and tetramer of fluoromethylpyrroles (FMPs), NC 4 H 4-CH n F 3Àn with n = 0, 1, 2, 3, and their radical cations have been studied using DFT-B3LYP method with 6-31G(d, p) basis set. FMPs are proposed in this research as candidate monomers for conducting polymers with modified characteristics compared to polypyrrole and polymethylpyrrole. A preliminary study using a set of ab initio computations (HF) with medium basis set was carried out on di-, tri-and tetramer in order to investigate the stability of configuration of polymer chains for FMPs. The B3LYP/6-31G** optimized geometry and stereochemistry show that the selectivity of branching of the propagating polymer chain is affected by the characteristics of the substitutions of monomer and, therefore, the growth pattern of the polymer chain can be predicted upon characterization of different centers of the monomers. Also, the results of this study, including quinoid coefficients, orbital energy spacing, charge-and spin-density distributions and electric dipole moment vectors show that conducting polymers consisted of trifluoromethyl pyrrole (Py-CF 3), compared with the other FMPs, are the most favorable to be used as monomers for conducting polymer structural and electronic properties.
Journal of Molecular Structure-theochem, 2008
There is a lot of interest from the scientific and technological point of view in the use of furan-based polymer molecules as electroconducting polymers despite some difficulties in their synthesis. In order to shed some light into the factors that affect the electrical conducting properties of furan-based polymers a theoretical study on methylamine and methoxy mono-substituted furan oligomers was performed. The purpose in choosing these substituents is founded on their electro-donning nature, which could have a favorable role on the reactivity of polyfuran molecules and have a direct effect on the band gap (E g ) and ionization potential (IP) facilitating in this way the synthesis of furan-based polymers. In addition the substituents were tested on different ring positions. All molecular geometries were optimized at B3LYP/6-31G(d) level of theory. Energy gaps between HOMO and LUMO orbitals and IPs were obtained from these calculations. IPs, and E g s of the polymers were obtained by extrapolating those of the oligomers to the inverse chain length equal to zero (1/N = 0). The theoretical calculations show that substituted oligomers are stable and have a minor value of E g and IP in their ground and doubly charged states. It was found that the carbon-carbon bond lengths in the oligomers are distorted in the charged states. This is due to the partial loss of ring aromaticity which forces some bond lengths to shorten or lengthen probably caused by the formation of quinoid-like structures.
Conducting polyfurans by electropolymerization of oligofurans
Chem. Sci., 2014
Polyfurans have never been established as useful conjugated polymers, as previously they were considered to be inherently unstable and poorly conductive. Here, we show the preparation of stable and conducting polyfuran films by electropolymerization of a series of oligofurans of different chain lengths substituted with alkyl groups. The polyfuran films show good conductivity in the order of 1 S cm À1 , good environmental and electrochemical stabilities, very smooth morphologies (roughness 1-5 nm), long effective conjugation lengths, well-defined spectroelectrochemistry and electro-optical switching (in the Vis-NIR region), and have optical band-gaps in the range of 2.2-2.3 eV. A low oxidation potential needed for polymerization of oligofurans (compared to furan) is a key factor in achievement of improved properties of polyfurans reported in this work. DFT calculations and experiments show that polyfurans are much more rigid than polythiophenes, and alkyl substitution does not disturb backbone planarity and conjugation. The obtained properties of polyfuran films are similar or superior to the properties of electrochemically prepared poly(oligothiophene)s under similar conditions. Israel † This work is dedicated to the memory of Professor Michael Bendikov. ‡ Electronic supplementary information (ESI) available: Full experimental and computational details, synthesis of 1-18, Fig. S1-S26 and Tables S1-S4. See
Polyfuran conducting polymers: Synthesis, properties, and applications
Synthetic Metals, 2008
In this review, polyfuran (PFu) synthesis methods and the nucleation mechanism; the electrochemical, structural, morphological, and magnetic properties of PFu; thermal behavior; theoretical calculations on PFu, as well as its applications reported to date, have been compiled. Not only PFu homopolymers have been reviewed, but also PFu co-polymers, PFu bipolymers, and PFu composites. The results are listed, discussed, and compared. It is hoped that this assembly of all the relevant data might enhance knowledge about this conducting polymer and lead to new research fields.
Spectroscopic study of a series of fluorine-pyrrole oligomers using the density functional theory
Physical Chemistry: An Indian Journal, 2014
In one of the works previously reported by our research team [J. Fluor. Chem. 128 (2007)], we used a DFT-B3LYP method in order to study the structural and electronic properties of the oligomers including the dimer, trimer, and tetramer of fluoromethylpyrroles (FMPs), NC4H4-CX3 (where - CX3 stands for -CH2F, -CHF2 and -CF3), and their radical cations. In the work mentioned above, FMPs were proposed as candidate monomers for conducting polymers with modified characteristics compared to polypyrrole and polymethylpyrrole. In the present work, the method mentioned above is applied to predict the vibrational frequencies and NMR properties of FMPs and their corresponding oligomers. The optimized structural parameters of these compounds are used in the vibrational spectra and chemical shift calculations. Analysis of the vibrational frequencies and NMR chemical shifts for the mono-, di-, tri-, and tetramer of FMPs supports their structural and electronic properties. The results obtained from...
Organic conducting polymers: synthesis, characterization and conductivity of polyethynylfluorenol
Polymer, 1992
The polymerization reactions of ethynylfluorenol (EFI) in the presence of Rh(I), Pt (II), Pd(II) and WCI 6 catalysts have been investigated. The polymer (PEFI) is air stable and soluble; in solution PEFI slowly releases some of the pendent groups which are converted into 9-fluorenone. Upon doping, enhancement of the conductivity up to about 10 orders of magnitude can be achieved. X.p.s. measurements performed on I2-doped PEFI suggest that 15 is the major doping species. An interesting reversible response to relative humidity variations is found for FeC13-doped samples.
In this paper, electronic, structural, and spectroscopic properties of mono-, di-, tri-, and tetrafluorothiophenes and their radical cations are studied using the density functional theory and B3LYP method with 6-311++G** basis set. Also the effects of the number and position of the substituent on the electrochemical properties of the thiophene ring have been studied using optimized structures obtained for these molecules and their cations, vibrational frequencies and nuclear chemical shielding constants of these compounds have been calculated and analyzed. The results of this study including charge and spin-density distribution, size and direction of the dipole moment vector, ionization potential, electric polarizability and NICS show that among all of these compounds 3-fluorothiophene as candidate monomer for new conductive polymers, possesses the most suitable conditions for electropolymerization.
Polymer Journal, 2010
We propose four types of poly(arylene ether)s (PAEs) polymers with remarkable thermal stability and high optical transmittance. The PAEs were synthesized by means of nucleophilic displacement through polymerization on a 2-trifluoromethyl-activated bisfluoro monomer to react with bisphenols. Thermal analysis indicated that PAEs possessed a high glass-transition point of B300 1C and a decomposition temperature of T d ¼500 1C at a weight loss of 5%. In addition, a high transmittance of 92%, a low dielectric constant of B1.9 and the mechanical properties of PAE films were experimentally determined. The physical properties of PAEs related to the arylene ether positions and phenyl substituents, which showed great potential as substrates for flexible electronics.
The Journal of Physical Chemistry B, 2002
A detailed analysis of the optical and photophysical properties of 2,7-bis(phenylene)-9,9-dioctylfluorene (PFP), 2,7-bis(biphenylene)-9,9-dioctylfluorene (BPFBP), 2,7-bis(2-thienyl)-9,9-dioctylfluorene (TFT), and 2,7-bis-(2,2 \-bithien-5-yl)-9,9-dioctylfluorene (BTFBT) in various environments are reported. The optical properties of the free molecules isolated in an alkane matrix are obtained and discussed in terms of the conformation adopted by each derivative in the electronic ground and first excited states. Also, conformational changes are responsible for the optical changes observed at high concentrations in an isopentane glass at 77 K. High quantum yields of all the oligofluorenes at 77 K indicate the absence of quenching effects such as excitonic or aggregation effects. The similar spectral and photophysical properties in matrix and glass environments are explained by the disorder introduced in oligofluorenes by long octyl chains at the C-9 position of the fluorene moiety. To study the effect of intermolecular interactions in the solid state, we recorded the spectra of thin films of these derivatives. The much red-shifted emission band in the solid state cannot be explained by conformational changes and has its origin in the π-stacking of conjugated oligomers in their relaxed S 1 state. As an evidence to show the importance of the role played by octyl chains at the C-9 position of the fluorene moiety, we synthesized two new model compounds: one, without octyl chains at the C-9 position of the fluorene moiety, 2,7-bis(2-thienyl)fluorene (TFTWC) and another with more octyl chains, 1,4-bis(9,9dioctylfluoren-2-yl)phenyl (FPF). The spectral properties of these derivatives have been studied at room temperature and at 77 K. These systems serve as excellent examples to show the effect of intermolecular interactions on optical properties of oligofluorenes.