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  1. Free, publicly-accessible full text available July 15, 2023
  2. Integration of polycyclic aromatic hydrocarbon (PAH) units into semi-fluorinated polymers affords high thermal stability and excellent processability for potential applications in optoelectronic, gas-separation, and advanced composites. Base-promoted step-growth polycondensation of commercial bisphenols with new triphenylene containing bis-trifluorovinyl ether (TFVE) monomers affords semi-fluorinated arylene vinylene ether (FAVE) polymers in good yields. The solution-processable polymers form tough transparent films and produce substitution dependent blue-light emission in solution with emission quantum yields ranging from 7.2–12% (in dichloromethane). Although predominantly amorphous with high glass transition temperatures ( T g ) ranging from 176–243 °C, powder X-ray diffraction studies show typical molecular diameter and pi-stacking reflections for triphenylene polymers. The polymers exhibited excellent thermal stability, solution photostability, and remarkable thermal oxidative photostability after heating at 250 °C for 24 h in air. Further, a model post-polymerization Scholl coupling afforded a novel semi-fluorinated hexabenzocoronene polymer with new optical properties. Time-dependent density functional theory (TD-DFT) computations were also performed using SMD (dichloromethane)- ω B97XD/BS1 (BS1 = 6-31G(d′) for C, H, O and F). This work demonstrated the synthesis and characterization of processable, blue-light emitting, thermally stable triphenylene enchained semi-fluorinated aryl ether polymers.
    Free, publicly-accessible full text available May 31, 2023
  3. The correlation consistent Composite Approach for transition metals (ccCA-TM) and density functional theory (DFT) computations have been applied to investigate the fluxional mechanisms of cyclooctatetraene tricarbonyl chromium ((COT)Cr(CO)3) and 1,3,5,7-tetramethylcyclooctatetraene tricarbonyl chromium, molybdenum, and tungsten ((TMCOT)M(CO)3 (M = Cr, Mo, and W)) complexes. The geometries of (COT)Cr(CO)3 were fully characterized with the PBEPBE, PBE0, B3LYP, and B97-1 functionals with various basis set/ECP combinations, while all investigated (TMCOT)M(CO)3 complexes were fully characterized with the PBEPBE, PBE0, and B3LYP methods. The energetics of the fluxional dynamics of (COT)Cr(CO)3 were examined using the correlation consistent Composite Approach for transition metals (ccCA-TM) to provide reliable energy benchmarks for corresponding DFT results. The PBE0/BS1 results are in semiquantitative agreement with the ccCA-TM results. Various transition states were identified for the fluxional processes of (COT)Cr(CO)3. The PBEPBE/BS1 energetics indicate that the 1,2-shift is the lowest energy fluxional process, while the B3LYP/BS1 energetics (where BS1 = H, C, O: 6-31G(d′); M: mod-LANL2DZ(f)-ECP) indicate the 1,3-shift having a lower electronic energy of activation than the 1,2-shift by 2.9 kcal mol−1. Notably, PBE0/BS1 describes the (CO)3 rotation to be the lowest energy process, followed by the 1,3-shift. Six transition states have been identified in the fluxional processes of eachmore »of the (TMCOT)M(CO)3 complexes (except for (TMCOT)W(CO)3), two of which are 1,2-shift transition states. The lowest-energy fluxional process of each (TMCOT)M(CO)3 complex (computed with the PBE0 functional) has a ΔG‡ of 12.6, 12.8, and 13.2 kcal mol−1 for Cr, Mo, and W complexes, respectively. Good agreement was observed between the experimental and computed 1H-NMR and 13C-NMR chemical shifts for (TMCOT)Cr(CO)3 and (TMCOT)Mo(CO)3 at three different temperature regimes, with coalescence of chemically equivalent groups at higher temperatures.« less
  4. Free, publicly-accessible full text available August 24, 2023
  5. Free, publicly-accessible full text available August 24, 2023