RESUMEN
Combination of CF(3)CHF and CF(3) radicals at room temperature generated chemically activated CF(3)CHFCF(3) molecules with 95 +/- 3 kcal/mol of internal energy that decompose by loss of HF, initially attached to adjacent carbons, with an experimental unimolecular rate constant of (4.5 +/- 1.1) x 10(2) s(-1). Density functional theory was used to model the unimolecular rate constant for HF elimination, k(HF), to determine a threshold energy of 75 +/- 2 kcal/mol.
Asunto(s)
Hidrocarburos Fluorados/química , Cinética , Modelos Moleculares , Conformación Molecular , Teoría Cuántica , TermodinámicaRESUMEN
A rapid and reproducible method for determining the temperature dependence of luminescence lifetimes has been developed. With the use of this method, a set of standards for the excited-state lifetime oxygen quenching of several ruthenium(II) transition metal complexes was established. With the use of three solvents of different viscosities and two metal complexes with widely different lifetimes, an overlapping range of ca. 100 ns to 6 micros was obtained. The decays are pure single exponentials, which means that they can be used reliably with both phase and pulsed lifetime instruments. For a pure single-exponential decay, a properly operating phase shift instrument will give the same lifetime as a time domain instrument. With the use of a thermal deactivation model and a three-parameter temperature-dependent oxygen quenching constant, the lifetime temperature-dependent data was well fit by a simple six-parameter equation that covers the temperature range of 10-50 degrees C and oxygen pressures from 0 to 1 atm of oxygen with excellent precision (ca. <1%). This permits both laboratory and field calibration of instruments.