Reversible thermal phase transition in crystalline (β-cyanoethyl)bis(dimethylglyoximato)(4-methylpyridine)colbalt(III)

Uchida, A.; Sasada, Y.; Ohashi, Y.

doi:10.1107/s0108768187012618

Cited by 9 publications

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“…The crystal showed a single crystal-to-single crystal phase transition at ca 343 K [113]. The unit cell dimensions gradually changed with retention of a single-crystal form on exposure to a xenon lamp above the phase transition (346 K), although the crystal was easily decomposed below the transition temperature.…”

Section: Crystallography Reviews 93mentioning

confidence: 98%

Dynamic motion and various reaction paths of cobaloxime complexes in crystalline-state photoreaction

Ohashi¹

2013

Crystallography Reviews

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The various alkyl groups bonded to the cobalt atom in (alkyl)(base)cobaloxime complex crystals are isomerized on exposure to visible light without degradation of the single crystal form. The solid-state reactions keeping the single crystal form were called crystalline-state reactions and the reaction mechanisms were explained with the concept of reaction cavity for the alkyl group. Changing the axial base ligands, a variety of crystalline-state reactions were examined not only by X-rays but also by neutron diffraction. The various reaction paths were made clear from the structures of initial, intermediate and final stages of the reactions. Moreover, the reaction rate was proved to have a positive relation with the volume of reaction cavity in each reaction. Not only various isomerizations but also unusual racemic-to-chiral transformations and a chirality inversion were also observed and the mechanisms were clearly explained and the shape of the reaction cavity made clear the mechanism. Two promising methods to observe the photoreaction with retention of the single crystal form, mixed crystal formation and bulky group insertion, are proposed and several successful results are shown.

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Section: Crystallography Reviews 93mentioning

confidence: 98%

Dynamic motion and various reaction paths of cobaloxime complexes in crystalline-state photoreaction

Ohashi¹

2013

Crystallography Reviews

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“…5 Recently it was observed that the p-ce group in the 3-methylpyridine complex crystal was isomerized to the a -c e group on exposure to visible light retaining the single crystal form. 6 The complex with 4-methylpyridine as an axial base ligand exhibits a reversible single crystal-to-single crystal thermal phase transition when the crystal was warmed up to 343 K. 7 The present work was undertaken to examine the reactivity above and below the phase transition temperature. Contrary to our expectation, two quite new results have been observed; one is that the p-ce group is isomerized without degradation of the crystallinity in the high temperature phase, the other is that the phase transition occurs below the transition temperature if the crystal was exposed to a weak Xe lamp.…”

Section: Introductionmentioning

confidence: 99%

Crystalline-State Photoisomerization and Photoinduced Phase Transition of a Cobaloxime Complex

Sekine

Tatsuki

Ohashi

1994

Molecular Crystals and Liquid Crystals Science and Technology.

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The ctystal of (~-cyanoethyl)bis(dimethylglyoximato)(4-methylpyridine)cobalt(III) exhibits a reversible single crystal-to-single crystal thermal phase transition at 343 K. The P-cyanoethyl group of the crystal was isomerized to a-cyanoethyl group retaining the single crystal form when the crystal was irradiated with a strong Xe lamp above 343 K, although the crystal was decomposed below the temperature. On the other hand, when the crystal was exposed to a weak Xe lamp at 340 K, the crystal showed the phase transition after 20 hours exposure keeping the single crystal form. The crystal after the phase transition also exhibited the P-a photoisomerization on exposure to the strong Xe lamp. The mechanism has clearly been elucidated on the basis of the analyzed structures before and after the photoisomerization or phase transition.

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Crystalline‐State Reaction

Ohashi¹

1994

Reactivity in Molecular Crystals

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One special feature of solid-state reactions is that the spacial arrangement of the atoms at the beginning and sometimes also at the end of the reaction can be mapped quite precisely. This distinguishes them from reactions in solution or in the gas phase and provides the possibility for new insight into the geometric aspects of chemical reactivity in general. The molecules in a given crystal react in a single conformation (occasionally in more than one) and in well-defined surroundings. Thus, differences in chemical behavior among crystals that differ mainly in the packing of otherwise similar molecules can be interpreted by studying the packingdifferences. Many excellent works are collected in Orxanic SolidState Chrmistr-y ' ) and Structure and Properties of' Molrcular Crjsstals. 2, Among the above solid-state reactions, a single crystal-to-single crystal transformation is very attractive, because both structures of the reactant and product are obtained by X-ray analysis using only one crystal. And the topochemical process can be easily speculated.The first example reported is the [2 + 21 photocycloaddition of 2,5-distyrylpyradine."' Further details will be discussed in section 5.1 in this volume. Other typical examples are the photopolymerization of diacetylene d e r i~a t i v e s ,~) the [2 + 21 photodimerization of 5-benzylidenecy~lopentanones~) and thermal dimerization of o-benzenedithiol cobalt complex.') In all the case the reaction proceeds almost keeping the single crystal form and the movement of each atom can be presumed from the structures before and after the reaction. The composite diagram of the reactant and product structures is very informative. However, the reaction does not alway proceed smoothly, that is, obeying first-order kinetics, from the intial stage to the final stage. The structures at several intermediate stages are essential for elucidating the reaction process. Moreover, a systematic analysis of related crystals is necessary to obtain a quantitative mechanism.In this section we describe a systematic analysis of reactions occurring in crystals keeping their single crystal forms. From several intermediate structures obtained by X-ray analyses, we have observed various reaction pathways and obtained a quantitative relationship between the macroscopic reaction rate and the microscopic atomic arrangement in a series of related crystals. Since such a stepwise X-ray structure analysis is a very effective method for elucidating the reaction mechanism, we call the analysis "dynamic structure analysis", and the reaction that enables the dynamic structure analysis is termed "crystalline-state reaction".')

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Reversible thermal phase transition in crystalline (β-cyanoethyl)bis(dimethylglyoximato)(4-methylpyridine)colbalt(III)

Cited by 9 publications

References 0 publications

Dynamic motion and various reaction paths of cobaloxime complexes in crystalline-state photoreaction

Dynamic motion and various reaction paths of cobaloxime complexes in crystalline-state photoreaction

Crystalline-State Photoisomerization and Photoinduced Phase Transition of a Cobaloxime Complex

Crystalline‐State Reaction

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