Time-dependent density functional theory calculations of the photoabsorption of fluorinated alkanes

Time-dependent density functional theory (TD-DFT) calculations of the transition energies and oscillator strengths of fluorinated alkanes have been performed. The TD-DFT method with the non-local B3LYP potential yields transition energies for the methanes, which are smaller by about 10% as compared to the experimental values. An empirical linear correlation was found between the calculated and experimental transition energies both at the B3LYP/DZ+Ryd(C, F) and B3LYP/cc-pVTZ+Ryd(C, F, H) levels for a total of 19 transitions of the fluorinated methanes with linear correlation coefficients of 0.987 for the former and 0.988 for the latter. This empirical correlation for fluorinated methane molecules is found to agree well with the previously obtained empirical correlations between calculated and experimental values for non-fluorinated molecules. The results show that a single empirical-correlation relationship can be used for both non-fluorinated and fluorinated molecules to predict transition energies. This linear relationship is then used to predict the photoabsorption spectra of ethane, propane, butane, and partially and fully fluorinated derivatives. A key result of these calculations is the dominance of Rydberg transitions in the spectral region of interest.     

Synthesis and characterization of new polyfluorinated dendrimeric phthalocyanines

The synthesis of new polyfluorinated dendrimeric metallophthalocyanines (M = Zn, Ni, Co) bearing 3,5-bis(2′,3′,4′,5′,6′-pentafluorobenzyloxy)benzyloxy moieties (2–4) was achieved by cyclotetramerization of phthalonitrile derivative 1 in the presence of zinc, nickel or cobalt salts in DMF. All the target phthalocyanines were separated by column chromatography and their spectroscopic, fluorescence and energy transfer properties, and aggregation behavior were investigated in different solvents and at different concentrations in chloroform. The compounds were characterized by Fourier transform-infrared, fluorine, proton and carbon nuclear magnetic resonance, mass, ultraviolet–visible and fluorescence spectral data. The phthalocyanines (2–4) were extremely soluble in various organic solvents, such as tetrahydrofuran, acetone and dichloromethane.     

New Fluorinated Poly(imide siloxane) Random and Block Copolymers with Variation of Siloxane Loading

Several new random and block copoly(imide siloxane)s have been prepared by the solution polycondensation of commercially available 4,4′-oxydianiline (ODA) and amino-propyl terminated polydimethylsiloxane (APPS) with 4,4′-(hexafluoro-isopropylidene)diphthalic anhydride (6FDA). The siloxane loading was kept to 10, 20, 30, 40 and 50 wt% in the copolymers. The random copolymers were prepared by a one pot solution imidization technique, and two pot solution imidization technique was adopted for the synthesis of the block copolymers. The diamine ODA and the dianhydride 6FDA composed the hard block segment, while APPS and 6FDA composed the soft block segment. The hard block length was kept constant while the soft block lengths were varied by varying the siloxane loading. Accordingly, block copoly(imide siloxane)s were prepared on increasing the soft block lengths (DP) from 3 to 6, 10, 18 and 36 for fixed hard block length of 22. The resulting polymers have been well characterized by IR, NMR and GPC techniques. Thermal and mechanical properties of the random and block copolymers were compared with the already reported homopolyimide without siloxane moiety.     

Synthesis of Highly Functionalized Fluorinated Porphyrins

Highly functionalized fluorinated porphyrins were synthesized by a convergent strategy. Nucleophilic substitution using fluorinated branched unit and 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin afforded highly functionalized fluorinated porphyrin 8 containing 24 fluorinated chains in the peripheral region.     

Reactions of fluorinated acid anhydrides, (CF3CO)2O, (CF3SO2)2O and (FSO2)2O, with organometallic substrates of group 15 (As, Sb and Bi)

(C₆H₅)₃MX₂ (M = As, Sb; X = OCOCF₃ and M = Sb, Bi; X = SO₃F, SO₃CF₃) compounds prepared by the interaction of triphenylmetal(V) substrates with (CF₃CO)₂O, (CF₃SO₂)₂O and (FSO₂)₂O have been characterized by molecular weight determination, elemental and spectroscopic (IR, ¹H and ¹⁹F NMR, mass) analyses.     

Fluorinated styrene-based monomers for cyclopolymerizations

The synthesis of versatile fluorine compounds and monomers for conducting polymer research and cyclopolymerizations is presented. Semiprotected 2,3,5,6-tetrafluoroterephthaldehyde 1 could be elaborated through Wittig olefination chemistry, deprotection and reduction to the previously unknown 4-vinyl-2,3,5,6-tetrafluorobenzylalcohol 8 in good yields. Compound 8 can be reacted to form the malonate ester, and then alkylation on the malonate moiety in mild conditions affords difunctional monomer 3. Through sequential esterifications on the malonate moiety, and subsequent alkylation, compound 4, a difunctional monomer for cyclopolymerization bearing one styrene and one perfluoroaryl styrene moiety, has been obtained. Preliminary experiments show that it is possible to cyclopolymerize 4 under free radical conditions.     

The Synthesis and Properties of Some Fluorinated Dialkyl Phosphoramidates

The synthesis and physical properties of the first fluorinated dialkyl phosphoramidates of structure (RCH 2 O) 2 P(O)NHCH 2 R F , where R = CH 3 , CF 3 or CCl 3 and R F = CF 3 or C 2 F 5 , are described. They were obtained by treatment of the respective dialkyl phosphorochloridates with trifluoroethylamine or pentafluoropropylamine in ether in the presence of triethylamine.     

CONVENIENT SYNTHETIC METHODS FOR THE PREPARATION OF N-FLUOROALKYLHYDROXAMIC ACIDS

ABSTRACT

Polyhydroxamate chelators containing fluoro substituents are of interest as potential extractants for actinides in separations involving supercritical carbon dioxide. In this context, we have developed three new reagents 1, 2, and 3, that allow the efficient incorporation of an N-fluoroalkyl hydroxamate moiety onto a variety of substrates using acylation, alkylation, and Michael addition strategies.     

Solubilization and applications of single-walled carbon nanotubes into aqueous and organic media by the use of nanometer size-controlled fluoroalkyl end-capped oligomeric aggregates

We have studied on the solubilization of single-walled carbon nanotubes (SW-CNTs) into aqueous and organic media by the use of a variety of nanometer size-controlled fluorinated self-assemblies, which were formed by the aggregations of end-capped fluoroalkyl segments in fluoroalkyl end-capped acrylic acid oligomers [R_F-(ACA)_n-R_F], N,N-dimethylacrylamide oligomers [R_F-(DMAA)_n-R_F], acryloylmorpholine oligomers [R_F-(ACMO)_n-R_F], and N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomers [R_F-(DOBAA)_n-R_F]. Fluorinated self assemblies formed in organic media (colorless solutions) could solubilize SW-CNTs into organic media to afford the transparent pale yellow solutions. The dynamic light scattering measurements showed that the size of fluorinated self-assemblies increased after the solubilization of SW-CNTs into organic media. It was suggested that the solubilization of SW-CNTs into organic media is due to the encapsulation of SW-CNTs into fluorinated assemblies. Fluorinated assemblies were also able to solubilize SW-CNTs into water to give the transparent gray solutions. Among a variety of fluorinated assemblies, fluorinated assemblies formed by R_F-(ACMO)_n-R_F [R_F = CF(CF₃)OC₆F₁₃] oligomer was more effective for the solubilization of SW-CNTs into both aqueous and organic media. Contact angle measurements of dodecane and the fluorescence spectra for poly(methyl methacrylate) cast film modified by fluorinated self-assemblies—SW-CNTs complexes showed that SW-CNTs are dispersed above the PMMA surface.     

Thermal stability and bond dissociation energy of fluorinated polymers: A critical evaluation

Intrinsic bond dissociation energies (BDEs) of selected fluorinated polymers are critically evaluated. Two distinctive approaches were followed. In the first one, according to Wu and Rodgers [E.-C. Wu, A.S. Rodgers, J. Am. Chem. Soc. 98 (1976) 6112-6115], starting from the gas-phase enthalpy of polymerization we obtained the polymer backbone BDE through appropriate thermodynamic cycles. Revised experimental results indicate that the CC BDEs of all the polymers taken into account fall within a limited energy interval, comparable to the average experimental uncertainty. Central to the second methodology adopted, is a model compound approach. Thanks to the large number of reliable thermodynamic data available in the scientific literature and to simple end-capping rules, C₂ molecules were chosen as suitable models for infinite linear polymers and alternating copolymers between ethylene and fluorinated olefins. For partially fluorinated polymers, like polyvinylidene fluoride (PVDF), alternating ethylene-tertrafluoroethylene (ETFE) and alternating ethylene-chlorotrifluoroethylene (ECTFE), the weight loss due to HF and HCl evolution during heating experiments was successfully related to the threshold energy E_o(HX) for 1,2-elimination from chemically activated hydrofluoro and hydrofluorochlorocarbons according to the modified Rice-Rampsberger-Kassel (RRKM) unimolecular theory.