Author
W.G. van Dorp
Bio: W.G. van Dorp is an academic researcher. The author has contributed to research in topics: Porphin & Triplet state. The author has an hindex of 8, co-authored 8 publications receiving 520 citations.
Papers
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TL;DR: In this paper, an appropriate mathematical model for describing the fluorescence transients is introduced in conjunction with a specific series of experiments from which one may evaluate the molecular quantities in a systematic way.
Abstract: Transient signals in the fluorescence intensity induced by microwaves can be used to acquire quantitative information on the molecular rates of populating and depopulating of the lowest triplet state of organic molecules. This method seems especially promising when the molecule emits no detectable phosphorescence. Part of this paper concerns the introduction of an appropriate mathematical model for describing the fluorescence transients. The model is formulated in conjunction with a specific series of experiments from which one may evaluate the molecular quantities in a systematic way. The kinetics of the lowest triplet state of free base porphin (H2P) are determined explicitly by this method. In the discussion the results for H2P are compared with those for Zn porphin. A satisfactory qualitative explanation based on the theory of radiationless transitions can be given for the great difference in behaviour of these two porphyrin molecules. Short attention is given to effects due to the photochemical shift...
120 citations
TL;DR: In this article, three pairs of microwave transitions with widths of a few MHz are found, all of them corresponding to a decrease in phosphorescence intensity, corresponding to the Shpolskii effect, and it was further established that by pumping either of these transitions a third one can be detected at the difference frequency, so that the order of the levels must be X>Y>Z (or reverse)
Abstract: Phosphorescence microwave double resonance experiments are reported on Zn porphin at 1·2 K In glassy solution very broad resonance transitions are observed However, for Zn porphin in a crystalline n-octane matrix—a system known for its sharp optical spectra (Shpolskii effect)—three pairs of microwave transitions with widths of a few MHz are found, all of them corresponding to a decrease in phosphorescence intensity By studying the behaviour of the signals for various methods of preparation of the sample and as a function of the optical bandwidth of excitation and detection, one pair of transitions could be assigned to monomeric solute molecules The corresponding zero-field splittings are |X - Z| = 1355, |Y - Z| = 806 MHz It was further established that by ‘pumping’ either of these transitions a third one can be detected at the difference frequency, so that the order of the levels must be X> Y>Z (or reverse) The results indicate that the molecule no longer possesses a four-fold axis in the excited st
101 citations
TL;DR: The zero-field splitting of the non-phosphorescent lowest triplet state of free base porphin is measured by observing microwave induced changes in the fluorescence of this molecule as a guest in a Shpolskii-matrix of n -octane at 4.2°K.
88 citations
TL;DR: In this paper, the authors have shown that the large majority of guest molecules occur in two orientations and that the 65 cm-1 doublet separation is related to the occurrence of these two orientation, and the hyperfine structure is obtained for the two inplane canonical orientations of the magnetic field and also when the field bisects the angle between these two directions.
Abstract: E.S.R. experiments have been performed on the lowest triplet state of free base porphin (H2P) in a n-octane single crystal at 1·3 K. The results demonstrate that the large majority of guest molecules occur in two orientations. While the molecules in these two orientations are coplanar, they have their N-H H-N axes at right angles. The fine structure results show that the two molecular orientations have zero-field splittings that differ by a few per cent in magnitude. Further, the 65 cm-1 doublet separation which appears in the fluorescence spectrum of H2P is related to the occurrence of these two orientations. Resolved hyperfine structure is obtained for the two in-plane canonical orientations of the magnetic field and also when the field bisects the angle between these two directions. From an analysis of the fine structure and hyperfine structure results it is established that the zero-field splitting pattern is described by the parameters (average over the two orientations) the x axis is taken along the...
85 citations
43 citations
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01 Jan 1978
741 citations
TL;DR: This review highlights the basic principles and the main mechanisms behind phosphorescent light emission of various classes of photofunctional OLED materials, like organic polymers and oligomers, electron and hole transport molecules, elementoorganic complexes with heavy metal central ions, and clarify connections between the main features of electronic structure and the photo-physical properties of the phosphorescent OLED materials.
Abstract: Organic light-emitting device (OLED) technology has found numerous applications in the development of solid state lighting, flat panel displays and flexible screens. These applications are already commercialized in mobile phones and TV sets. White OLEDs are of especial importance for lighting; they now use multilayer combinations of organic and elementoorganic dyes which emit various colors in the red, green and blue parts of the visible spectrum. At the same time the stability of phosphorescent blue emitters is still a major challenge for OLED applications. In this review we highlight the basic principles and the main mechanisms behind phosphorescent light emission of various classes of photofunctional OLED materials, like organic polymers and oligomers, electron and hole transport molecules, elementoorganic complexes with heavy metal central ions, and clarify connections between the main features of electronic structure and the photo-physical properties of the phosphorescent OLED materials.
371 citations
TL;DR: The theory and principles of computational phosphorescence are illustrated by highlighting studies of classical examples like molecular nitrogen and oxygen, benzene, naphthalene and their azaderivatives, porphyrins, as well as by reviewing current research on systems like electrophosphorescent transition metal complexes, nucleobases, and amino acids.
Abstract: Phosphorescence is a phenomenon of delayed luminescence that corresponds to the radiative decay of the molecular triplet state. As a general property of molecules, phosphorescence represents a cornerstone problem of chemical physics due to the spin prohibition of the underlying triplet-singlet emission and because its analysis embraces a deep knowledge of electronic molecular structure. Phosphorescence is the simplest physical process which provides an example of spin-forbidden transformation with a characteristic spin selectivity and magnetic field dependence, being the model also for more complicated chemical reactions and for spin catalysis applications. The bridging of the spin prohibition in phosphorescence is commonly analyzed by perturbation theory, which considers the intensity borrowing from spin-allowed electronic transitions. In this review, we highlight the basic theoretical principles and computational aspects for the estimation of various phosphorescence parameters, like intensity, radiative...
362 citations
TL;DR: In this paper, the triplet state of a single pentacene molecule embedded in a p-terphenyl host crystal was observed for a single molecule in a single-molecule environment.
Abstract: THE introduction of optical detection methods for observing magnetic resonance transitions in metastable paramagnetic states1–4 has contributed enormously to our understanding of the properties of photoexcited molecules in condensed phases. In such experiments the luminescence intensity is recorded as a function of the frequency of an applied microwave field. At resonance with transitions between sublevels of a metastable paramagnetic state, the lifetime of the metastable state is altered and a consequent change in the luminescence intensity is observed. Here we report the observation of such optically detected magnetic resonance transitions for the triplet state of a single pentacene molecule embedded in a p-terphenyl host crystal. This result has been obtained by combining the conventional optical detection technique for observing magnetic resonance transitions1–4 with the new single-molecule optical detection methods developed recently5,6. This observation opens the way for magnetic resonance studies in condensed phases with single-molecule sensitivity.
233 citations
210 citations