COMFORMATIONAL ANALYSIS AND ELECTRONIC PROPERTIES OF FLUOROMETHYLFURAN OLIGOMERS: SEMIEMPIRICAL AND DFT STUDY. (original) (raw)
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Semiempirical and Density Functional Thoery Study on Structure of Fluoromethylfuran Oligomers
Australian Journal of Basic and Applied …, 2011
Structural and electronic properties of oligomers of fluoromethylfurans (FMFs), OC 4 H 4-CH n F 3-n with n = 1, 2, 3 and 4 have been studied using ZINDO/AM1 and B3LYP/6-31G(d) basis set. Preliminary study using AM1 and ab initio (HF) 6-31G(d) with medium basis set was carried out on di-, tri-and tetramer FMFs in order to investigate the stability of configuration of the polymer chains and conformation analysis of the dimers. There is noticeable effect of substituents on the geometries of FMFs as compared to polyfuran, polymethylfuran and chloromethylfuran (CMF) analogues [11]. The modeled FMFs have improved characteristics as conducting polymers compared to polyfurans, polymethylfurans and CMFs. The most stable conformation is the anti-planar conformation except in fluoromethylfuran in which anti-gauche conformation is most stable. The energy band gaps, electronic spectroscopy and electronic dipole moment vectors of the compounds are presented. Generally FMFs presented lower energy band gaps, longer wavelength and higher electric dipole moments and are therefore more suitable as monomer for conducting polymer especially trifluoromethylfuran.
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.
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.
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.
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.
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
Synthetic Metals, 1993
A number of triheterocycles XYZ, where X, Y, Z = furan (O), thiophene (S), or N-methylpyrrole (N) were prepared, and the polymers, obtained by oxidizing them with NOPF 6, were studied by four-probe DC conductivity and EPR. SSS has a conductivity of 2.4 S cm -1 at room temperature, and 0.0075 spin/triheterocycle, while SOS has a conductivity of 0.2 S cm -1 and 0.15 spins/triheterocycle; both have narrow Lorentzian EPR lineshapes. The other samples had conductivities below the measurement threshhoid (10 -5 S cm-t). We postulate that NOPF 6 overoxidized the polymers, thereby creating more bipolarons than polarons, and reducing the number of charge carriers. X, Y, Z = O, $, N(Me)
Polyfluorenes have emerged as versatile semiconducting materials with applications in various polymer optoelectronic devices, such as light-emitting devices, lasers, solar cells, memories, field-effect transistors and sensors. Organic syntheses and polymerizations allow for the powerful introduction of various periodic table elements and their building blocks into -conjugated polymers to meet the requirements of organic devices. In this review, a soccer-team-like framework with 11 nodes is initially proposed to illustrate the structure-property relationships at three levels: chain structures, thin films and devices. Second, the modelling of hydrocarbon polyfluorenes (CPFs) is summarized within the framework of a four-element design principle, in which we have highlighted polymorphic poly(9,9-dialkylfluorene)s with unique supramolecular interactions, various hydrocarbon-based monomers with different electronic structures, functional bulky groups with steric hindrance effects and ladder-type, kinked, hyperbranched and dendritic conformations. Finally, the detailed electronic structure designs of main-chain-type heteroatomic copolyfluorenes (HPFs) and metallopolyfluorenes (MPFs) are described in the third and fourth sections. Supramolecular, nano and soft semiconductors are the future of polyfluorenes in the fields of optoelectronics, spintronics and electromechanics.
Journal of Organic Chemistry, 2005
Poly(fluorene)-type materials are widely used in polymer-based emitting devices. One of the drawbacks of light-emitting diodes based on polyfluorene derivatives is the injection of holes from the anode due to the high ionization potential (IP) of most derivatives. Substitution by electrondonating alkoxy substituents or by adding charge carriers on the conjugated polymer's backbone produces a remarkable influence on its electrical and optical properties. In this contribution, we apply quantum-chemical techniques to investigate a family of π-conjugated polymers with substituted dimethoxy groups at the 3,6 positions of the fluorene ring, namely, poly(2,7-(3,6dimethoxy-fluorene)(PDMOF), poly(2,7-(3,6-dimethoxy-fluorene)-co-alt-fluorene (PDMOFF), and poly(2,7-(3,6-dimeth-oxy-fluorene)-co-alt-2,5-thiophene (PDMOFT). The electronic properties of the neutral molecules, HOMO-LUMO gaps (∆ H-L ), in addition to the positive and negative ions, are studied using the B3LYP functional. The lowest excitation energies (E g ) and the maximal absorption wavelength λ abs of PDMOF, PDMOFF, and PDMOFT are studied by employing time-dependent density functional theory (TD-DFT) and the ZINDO semiempirical method. The IP, EA, and E g values of each polymer were obtained by extrapolating those of the oligomers to the inverse chain length equal to zero ( 1 / n ) 0). The influence of the presence of methoxy groups on the fluorene moiety on the ionization potential is especially emphasized. The outcomes show that the HOMO energies of these systems under study increase by about 0.4 eV and the IP values decrease by about 0.3 eV compared to those of the corresponding polyfluorene. Both effects result in a reduction of the energy barrier for the injection of holes in related polymeric light-emitting devices and should contribute to the enhancement of their performances. Because of the cooperation with thiophene in PDMOFT, which results in a good planar conformation, both the hole-creating and electronaccepting abilities are improved.