X-ray Direct Observation of Reactions and Labile Species on the Basis of Crystal Design

Chemical Society of Japan 2014 Bulletin of the Chemical Society of Japan Vol. No.

This account reviews recent development of in situ crystallographic study of reactive intermediates using the cryo-trapping method. Starting from the basic concept of a reaction cavity in a crystal, we succeeded in not only observing photoinduced reactive species such as radical, carbene, and nitrene but also establishing a unique approach, crystalline molecular flask, to observe labile species in chemical reactions in a crystal. On the basis of such a crystalline reaction field design, we successfully observed irreversible reactive intermediates in a crystal.

Crystalline molecular flasks

Inokuma, Yasuhide,Kawano, Masaki,Fujita, Makoto Nature Publishing Group, a division of Macmillan P 2011 Nature chemistry Vol.3 No.5

<P>A variety of host compounds have been used as molecular-scale reaction vessels, protecting guests from their environment or restricting the space available around them, thus favouring particular reactions. Such molecular 'flasks' can endow guest molecules with reactivities that differ from those in bulk solvents. Here, we extend this concept to crystalline molecular flasks, solid-state crystalline networks with pores within which pseudo-solution-state reactions can take place. As the guest molecules can spontaneously align along the walls and channels of the hosts, structural changes in the substrates can be directly observed by in situ X-ray crystallography during reaction. Recently, this has enabled observation of the molecular structures of transient intermediates and other labile species, in the form of sequential structural snapshots of the chemical transformation. Here, we describe the principles, development and applications of crystalline molecular flasks.</P>

Single-crystal growth of coordination networks <i>via</i> the gas phase and dependence of iodine encapsulation on the crystal size

Kojima, Tatsuhiro,Choi, Wanuk,Kawano, Masaki The Royal Society of Chemistry 2014 Chemical communications Vol.50 No.89

<P>Self-assembly of the tripyridyl ligand 2,4,6-tris(4-pyridyl)triazine(TPT) and ZnI<SUB>2</SUB><I>via</I> the gas phase produced three kinds of networks: [(ZnI<SUB>2</SUB>)(TPT)]<SUB><I>n</I></SUB>; [(ZnI<SUB>2</SUB>)<SUB>3</SUB>(TPT)<SUB>2</SUB>]<SUB><I>n</I></SUB>; and [(ZnI<SUB>2</SUB>)(μ-I)(ZnI)(TPT)]<SUB><I>n</I></SUB>. [(ZnI<SUB>2</SUB>)<SUB>3</SUB>(TPT)<SUB>2</SUB>]<SUB><I>n</I></SUB> is the first example of the single crystal formation of a porous network <I>via</I> the gas phase and showed the dependence of iodine encapsulation on the crystal size.</P> <P>Graphic Abstract</P><P>Three kinds of coordination networks were selectively obtained <I>via</I> the gas phase. Thermodynamic control <I>via</I> the gas phase produced the first example of the single-crystal formation of a porous network. As a result of this single-crystal growth, we were able to show the dependence of guest encapsulation on the crystal size. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cc06342b'> </P>

Kinetic Assembly of a Thermally Stable Porous Coordination Network Based on Labile CuI Units and the Visualization of I₂ Sorption

Kitagawa, Hakuba,Ohtsu, Hiroyoshi,Kawano, Masaki WILEY‐VCH Verlag 2013 Angewandte Chemie Vol.125 No.47

<P><B>Im Netz gefangen</B>: Ein kinetisch angeordnetes, aber thermisch stabiles Netzwerk wird unter Verwendung der labilen Metallspezies [Cu<SUB>4</SUB>I<SUB>4</SUB>(PPh<SUB>3</SUB>)<SUB>4</SUB>] erhalten. In einzigartiger Weise adsorbiert es I<SUB>2</SUB> durch Chemisorption über I<SUB>3</SUB><SUP>−</SUP>‐Bildung. Das chemisorbierte I<SUB>2</SUB> desorbiert leicht bei >380 K wegen der dynamischen Bewegung des Gerüstes. Ein thermodynamisch angeordnetes Netzwerk physisorbiert I<SUB>2</SUB>, das exakt in den Kanal passt.</P>

Kinetic Products in Coordination Networks: Ab Initio X-ray Powder Diffraction Analysis

Martí,-Rujas, Javier,Kawano, Masaki American Chemical Society 2013 Accounts of chemical research Vol.46 No.2

<P>Porous coordination networks are materials that maintain their crystal structure as molecular “guests” enter and exit their pores. They are of great research interest with applications in areas such as catalysis, gas adsorption, proton conductivity, and drug release. As with zeolite preparation, the kinetic states in coordination network preparation play a crucial role in determining the final products. Controlling the kinetic state during self-assembly of coordination networks is a fundamental aspect of developing further functionalization of this class of materials. However, unlike for zeolites, there are few structural studies reporting the kinetic products made during self-assembly of coordination networks. Synthetic routes that produce the necessary selectivity are complex.</P><P>The structural knowledge obtained from X-ray crystallography has been crucial for developing rational strategies for design of organic–inorganic hybrid networks. However, despite the explosive progress in the solid-state study of coordination networks during the last 15 years, researchers still do not understand many chemical reaction processes because of the difficulties in growing single crystals suitable for X-ray diffraction: Fast precipitation can lead to kinetic (metastable) products, but in microcrystalline form, unsuitable for single crystal X-ray analysis. X-ray powder diffraction (XRPD) routinely is used to check phase purity, crystallinity, and to monitor the stability of frameworks upon guest removal/inclusion under various conditions, but rarely is used for structure elucidation. Recent advances in structure determination of microcrystalline solids from ab initio XRPD have allowed three-dimensional structure determination when single crystals are not available. Thus, ab initio XRPD structure determination is becoming a powerful method for structure determination of microcrystalline solids, including porous coordination networks. Because of the great interest across scientific disciplines in coordination networks, especially porous coordination networks, the ability to determine crystal structures when the crystals are not suitable for single crystal X-ray analysis is of paramount importance.</P><P>In this Account, we report the potential of kinetic control to synthesize new coordination networks and we describe ab initio XRPD structure determination to characterize these networks’ crystal structures. We describe our recent work on selective instant synthesis to yield kinetically controlled porous coordination networks. We demonstrate that instant synthesis can selectively produce metastable networks that are not possible to synthesize by conventional solution chemistry. Using kinetic products, we provide mechanistic insights into thermally induced (573–723 K) (i.e., annealing method) structural transformations in porous coordination networks as well as examples of guest exchange/inclusion reactions. Finally, we describe a memory effect that allows the transfer of structural information from kinetic precursor structures to thermally stable structures through amorphous intermediate phases.</P><P>We believe that ab initio XRPD structure determination will soon be used to investigate chemical processes that lead intrinsically to microcrystalline solids, which up to now have not been fully understood due to the unavailability of single crystals. For example, only recently have researchers used single-crystal X-ray diffraction to elucidate crystal-to-crystal chemical reactions taking place in the crystalline scaffold of coordination networks. The potential of ab initio X-ray powder diffraction analysis goes beyond single-crystal-to-single-crystal processes, potentially allowing members of this field to study intriguing in situ reactions, such as reactions within pores.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/achre4/2013/achre4.2013.46.iss

Crystal surface mediated structure transformation of a kinetic framework composed of multi-interactive ligand TPHAP and Co(<small>II</small>)

Yakiyama, Yumi,Ueda, Akira,Morita, Yasushi,Kawano, Masaki The Royal Society of Chemistry 2012 Chemical communications Vol.48 No.86

<P>A tripyridyl multi-interactive ligand TPHAP is prepared by a one-pot reaction on a gram scale. Network formation of Co(<SMALL>II</SMALL>) with TPHAP<SUP>−</SUP> gave kinetic and thermally more stable products. The kinetic network showed an unprecedented dynamic network transformation on the crystal surface by a ligand exchange reaction.</P> <P>Graphic Abstract</P><P>Co(<SMALL>II</SMALL>) and multi-interactive ligand TPHAP afford a kinetic network followed by ligand exchange mediated dynamic network transformation on the crystal surface. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cc35078e'> </P>

Safe P₄ reagent in a reusable porous coordination network

Choi, Wanuk,Ohtsu, Hiroyoshi,Matsushita, Yoshitaka,Kawano, Masaki The Royal Society of Chemistry 2016 Dalton Transactions Vol.45 No.15

<P>P-4 generated from red phosphorus via the gas phase was trapped into an interactive pore of a porous coordination network, showing weak interactions which stabilize the reactive P-4 in a pore. The network is reusable as a safe container of P-4. Furthermore, we found a size dependence of the P-4 trapping amount: for 100-50 mu m crystal, 27% occupancy of P-4; and for < 20 mu m crystal, ca. 93% occupancy of P-4.</P>

Eclipsed Columnar Packing in Crystal Structure of Sumanenetrione

Shrestha, Binod Babu,Morita, Yuki,Kojima, Tatsuhiro,Kawano, Masaki,Higashibayashi, Shuhei,Sakurai, Hidehiro Chemical Society of Japan 2014 Chemistry letters Vol.43 No.8

Solid–liquid interface synthesis of microcrystalline porous coordination networks

Martí,-Rujas, Javier,Matsushita, Yoshitaka,Izumi, Fujio,Fujita, Makoto,Kawano, Masaki Royal Society of Chemistry 2010 Chemical communications Vol.46 No.35

<P>Solid–liquid interface synthesis provided a unique way to selectively and efficiently prepare molecular complexes (ML<SUB>2</SUB>) and metastable porous coordination networks in short crystallization times. In sharp contrast, their solution reactions gave interpenetrated open-framework networks. We succeeded in solving a crystal structure of the metastable network by <I>ab initio</I> powder X-ray analysis.</P> <P>Graphic Abstract</P><P>Solid–liquid interface synthesis provided a unique way to selectively and efficiently generate crystalline monomers and metastable porous coordination networks. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0cc01141j'> </P>

Selective Trapping of Labile S₃ in a Porous Coordination Network and the Direct X-ray Observation

Ohtsu, Hiroyoshi,Choi, Wanuk,Islam, Nazrul,Matsushita, Yoshitaka,Kawano, Masaki American Chemical Society 2013 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.135 No.31

<P>S<SUB>3</SUB> is one of the basic allotropes of sulfur but is still a mysterious labile species. We selectively trapped S<SUB>3</SUB> in a pore of a thermally stable coordination network and determined S<SUB>3</SUB> structure by <I>ab initio</I> X-ray powder diffraction analysis. S<SUB>3</SUB> in a pore has a <I>C</I><SUB>2<I>v</I></SUB> bent structure. The network containing trapped S<SUB>3</SUB> is remarkably stable under ambient conditions and is inert to photoirradiation. S<SUB>3</SUB> in the network could be transformed to S<SUB>6</SUB> by mechanical grinding or heating in the presence of NH<SUB>4</SUB>X (X = Cl or Br). S<SUB>6</SUB> could be reverse-transformed to S<SUB>3</SUB> by photoirradiation. We also determined the structure of the network containing S<SUB>6</SUB> by <I>ab initio</I> X-ray powder diffraction analysis.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-31/ja4046718/production/images/medium/ja-2013-046718_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja4046718'>ACS Electronic Supporting Info</A></P>