Phase Rebuilding of α-Cinnamic Acid in Tail Irradiations

Kaupp, Gerd; Haak, Michael

doi:10.1080/10587259808044274

Cited by 15 publications

(14 citation statements)

References 8 publications

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“…The AFM measurement of Figure 1 was taken between microscopic trenches in the same direction as the "fences." The crystal disintegrates above 30% dimerization [13]. All of these results support the challenges to a rather strange X-ray analysis as claimed for a so-called 100% dimerized α-cinnamic acid [14] in an attempt to continue claiming topochemistry by topotaxy (minimal atomic and molecular movements) against the nano-, micro-, and macro-scale evidence for far-reaching anisotropic molecular migrations followed by crystal disintegration [13].…”

Section: Introductionsupporting

confidence: 66%

Organic Solid-State Reactions

Kaupp

2016

Encyclopedia of Physical Organic Chemistry, 5 Volume Set

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Section: Introductionsupporting

confidence: 66%

Organic Solid-State Reactions

Kaupp

2016

Encyclopedia of Physical Organic Chemistry, 5 Volume Set

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“…However, the importance of the topic requires additional proof by independent SNOM. In no stage of the reaction could a SNOM contrast be obtained, therefore the photoreaction proceeds everywhere in the region of light penetration (down to 1300 layers with 365 nm light or through the whole crystal at "tail irradiation" with extremely low absorbed filtered daylight intensity at an extremely slow partial transformation during 6 months) [14] and the features do not differ in composition at different sites or from flat parts. As the photodimer 9 (without C=C double bonds) should reflect very differently from the cinnamic acid (8) (with a C=C double bond) any possibility for a cluster-by-clustertype photoreaction before crystal disintegration is additionally excluded by the absence of chemical contrast.…”

Section: Photodimerization Of α-Cinnamic Acidmentioning

confidence: 99%

Scanning near‐field optical microscopy on rough surfaces: Applications in chemistry, biology, and medicine

Kaupp

2006

International Journal of Photoenergy

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Shear-force apertureless scanning near-field optical microscopy (SNOM) with very sharp uncoated tapered waveguides relies on the unexpected enhancement of reflection in the shear-force gap. It is the technique for obtaining chemical (materials) contrast in the optical image of “real world” surfaces that are rough and very rough without topographical artifacts, and it is by far less complicated than other SNOM techniques that can only be used for very flat surfaces. The experimental use of the new photophysical effect is described. The applications of the new technique are manifold. Important mechanistic questions in solid-state chemistry (oxidation, diazotization, photodimerization, surface hydration, hydrolysis) are answered with respect to simultaneous AFM (atomic force microscopy) and detailed crystal packing. Prehistoric petrified bacteria and concomitant pyrite inclusions are also investigated with local RAMAN SNOM. Polymer beads and unstained biological objects (rabbit heart, shrimp eye) allow for nanoscopic analysis of cell organelles. Similarly, human teeth and a cancerous tissue are analyzed. Bladder cancer tissue is clearly differentiated from healthy tissue without staining and this opens a new highly promising diagnostic tool for precancer diagnosis. Industrial applications are demonstrated at the corrosion behavior of dental alloys (withdrawal of a widely used alloy, harmless substitutes), improvement of paper glazing, behavior of blood bags upon storage, quality assessment of metal particle preparations for surface enhanced RAMAN spectroscopy, and determination of diffusion coefficient and light fastness in textile fiber dyeing. The latter applications include fluorescence SNOM. Local fluorescence SNOM is also used in the study of partly aggregating dye nanoparticles within resin/varnish preparations. Unexpected new insights are obtained in all of the various fields that cannot be obtained by other techniques.

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“…Such a claim of Wegner, Enkelmann et al found widespread interest because an X-ray structural data-set was claimed to support that idea and passed the review procedure apparently without due validity check [19]. However, the invalidity [20] of the alleged X-ray data is easily demonstrated by their imaging (Figure 2). Nevertheless, the scrutiny of these clearly unsound data in [19] was refused, except in reference [20], and the scientific community still awaits their withdrawal by the authors.…”

Section: Tail Irradiationmentioning

confidence: 99%

“…However, the invalidity [20] of the alleged X-ray data is easily demonstrated by their imaging (Figure 2). Nevertheless, the scrutiny of these clearly unsound data in [19] was refused, except in reference [20], and the scientific community still awaits their withdrawal by the authors.…”

Section: Tail Irradiationmentioning

confidence: 99%

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Solid‐state photochemistry: new approaches based on new mechanistic insights

Kaupp

2001

International Journal of Photoenergy

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The application of atomic force microscopy (AFM) to solid-state photodimerizations revealed previously unexpected long-range molecular movements in the initial stages (phase rebuilding) and in the final stages (phase transformation and disintegration) of reaction. The consequences for the new understanding of solid-state photochemistry are discussed. The 4.2 Å criterion of organic topochemistry lacks a real basis and is not applicable to regular photolyses, even under tail irradiation conditions for instance ofα-cinnamic acid or inE/Z-isomerizations in the crystal bulk. The experimental observation of molecular movements in reacting crystals requires more elaborate use of X-ray structural data by invoking the molecular packing. If a crystal keeps its outer form upon photolysis this does not necessarily indicate a topotactic transformation, and submicroscopically resolved AFM investigations are in order. The applications of molecular movements or non-photoreactivities due to the prevention of movements by 3D-interlocked packing have numerous applications. Thus, amorphous solids or inclusion compounds may enable the movements in these cases. Hitherto puzzlingE/Z-photoisomerizations in the crystalline state can now be mechanistically understood. In some cases even rotational mechanisms can be modelled in combination with the movements. In others the space saving twist mechanism is the only choice. The benefits of the new solid-state mechanisms for crystal engineering, photochromism, mixed crystals, absolute asymmetric syntheses, and preparative photochemistry derive from its experimental basis. Numerous presumed puzzles from the postulate of minimal atomic and molecular movement vanish in a straightforward manner.

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Phase Rebuilding of α-Cinnamic Acid in Tail Irradiations

Cited by 15 publications

References 8 publications

Organic Solid-State Reactions

Organic Solid-State Reactions

Scanning near‐field optical microscopy on rough surfaces: Applications in chemistry, biology, and medicine

Solid‐state photochemistry: new approaches based on new mechanistic insights

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