Gamal-Eddin Khalil

Porphyrin free base phosphorescence

Abstract The wavelength for heavy atom enhanced phosphorescence is unambiguously established by time resolved excitation spectra in 50% EPA and 50% ethyl iodide at 77 K for protoporphyrin (795 nm), mesoporphyrin (773 nm), octaethylporphin (768 nm), and porphin (785 nm). Excitation spectra also establish the phosphorescence wavelength of brominated protoporphyrin in EPA at 77 K to be 783 nm, with a quantum yield φp ∼ 9 × 10−4. Using laser excitation the phosphorescence quantum yields in EPA were found for protoporphyrin (φp ∼ 5 × 10−5), mesoporphyrin (φp

Surface pressure field mapping using luminescent coatings

In recent experiments we demonstrated the feasibility of using the oxygen dependence of luminescent molecules for surface pressure measurement in aerodynamic testing. This technique is based on the observation that for many luminescent molecules the light emitted increases as the oxygen partial pressure, and thus the air pressure, the molecules see decreases. In practice the surface to be observed is coated with an oxygen permeable polymer containing a luminescent molecule and illuminated with ultraviolet radiation. The airflow induced surface pressure field is seen as a luminescence intensity distribution which can be measured using quantitative video techniques. Computer processing converts the video data into a map of the surface pressure field. The experiments consisted of evaluating a trial luminescent coating in measuring the static surface pressure field over a two-dimensional NACA-0012 section model airfoil for Mach numbers ranging from 0.3 and 0.66. Comparison of the luminescent coating derived pressures were made to those obtained from conventional pressure taps. The method along with the experiment and its results will be described.

Porphyrins. XXXII. Absorptions and luminescence of Cr(III) complexes

Chloro−(tetraphenylporphinato)chromium(III) shows relatively normal visible (Q) bands in the region 610−500 nm and a relatively normal Soret (B) band at 447 nm; in addition, there are prominent bands in the near uv region 400−300 nm (2×104 < e < 3×104 M−1⋅cm−1) and clear near ir bands in the region 820−610 nm (300 < e < 2100 M−1⋅cm−1). At 160°K there is one main emission band at ∼815nm (τ < 6 μsec); at 77°K there are emission bands of comparable intensity at both 811 and 847 nm (τ = 44 μsec); at 4°K both emission bands appear with intensity ratio I811/I847 = 0.12. The near ir absorption and emission band at 811 nm is attributed to a ’’trip−quartet’’ excited state formed from the (π,π*), S = 1 porphyrin state coupling to the d3, S = 3/2 electrons of the Cr(III); the 847 nm emission is attributed to the sextet state that arises from the same electron configuration. The prominent near uv bands are attributed to a2u(π), a1u(π) → eg(dπ) charge transfer transitions. Phenol−phenoxo− (octaethylporphinato)chromium...

High Performance Liquid Chromatography Separation and Analysis of Metallotetra(Pentafluorophenyl)Porpholactone

Abstract The analytical separation and analysis of silver, nickel, zinc and palladium complexes of tetra(pentafluorophenyl)porpholactone (TFPL) from free bases is described. An isocratic mobile phase of n-hexane and diethyl ether was developed to separate these complexes using a normal phase μPorasil HPLC column (150 × 3.9 mm I. D.) at a flow rate of 1 mL/min. In addition, two porphodilactone isomers were also isolated from the reaction products, a result which we were unable to achieve with flash chromatography nor with a reversed phase C18 Ultrasphere HPLC column (250 × 4.6 mm I. D.). The optical absorption spectra of the metal derivatives show two bands in the visible region, compared to the four bands shown by the free base. The retention of these metal complexes on a normal phase column was found to be increasing in the order Pd(TFPL) < Ag(TFPL) < Zn(TFPL) < Ni(TFPL).

Novel ultraviolet electroluminescence from Al/octaethylporphyrin/Ag film sandwich cells

Abstract The electroluminescence of a [glass/Al/H 2 OEP/Ag] sandwich cell under pulsed voltage is presented. The luminescence obtained shows three types of light. (i) There is a red fluorescence characteristics of the octaethylporphyrin material, with the origin at ≈ 630 nm. (ii) There is a UV emission consisting of two origin bands at 315.0 nm and 336.5 nm. An extensive vibronic progression is built on the latter which contains two vibrational energies, 1350 and 1680 cm -1 , which are known to be porphyrin ring vibrations. The progression is explained as electron-hole recombination, i.e. P + +P - →2P(v), Where v is a vibrational level. Two possible explanations are offered for the 315.0 nm origin band, on which no progression is built. (iii) The third type of light comes in the form of burst attributed to dielectric breakdown. The burst last for about 10–20 ns.