Dramatic Structural Rearrangements in Porous Coordination Networks

Martí,-Rujas, Javier,Islam, Nazrul,Hashizume, Daisuke,Izumi, Fujio,Fujita, Makoto,Kawano, Masaki American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.15

<P>With the use of <I>ab initio</I> X-ray powder diffraction, a family of isostructural crystalline porous coordination networks, [(ZnX<SUB>2</SUB>)<SUB>3</SUB>(TPT)<SUB>2</SUB>]<SUB><I>n</I></SUB>· (solvent) (X = I, Br, Cl), has been studied at elevated temperatures of 573−723 K. Upon heating, all three networks exhibited crystalline-to-amorphous-to-crystalline (CAC) phase transformations to three new networks, [(ZnI<SUB>2</SUB>)<SUB>3</SUB>(TPT)<SUB>2</SUB>]<SUB><I>n</I></SUB>, [(ZnBr<SUB>2</SUB>)<SUB>3</SUB>(TPT)<SUB>2</SUB>]<SUB><I>n</I></SUB>·(H<SUB>2</SUB>O) and [(ZnBr<SUB>2</SUB>)(μ-Br)(ZnBr)(TPT)]<SUB><I>n</I></SUB>, and [(ZnCl<SUB>2</SUB>)(μ-Cl)(ZnCl)(TPT)]<SUB><I>n</I></SUB>, respectively. A set of control experiments was used to obtain detailed mechanistic aspects of the CAC transformations. We demonstrate how bonds are broken and formed in these significant molecular rearrangements and how the initial arrangement plays a crucial role in the formation of the new networks after the CAC transformations. The structural information in the amorphous phase is retained and passed from a metastable to a more stable crystal, thus, reinforcing the notion that coordination networks are flexible and chemically active.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2011/jacsat.2011.133.issue-15/ja109160a/production/images/medium/ja-2010-09160a_0014.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja109160a'>ACS Electronic Supporting Info</A></P>

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>

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

Ab Initio Powder Diffraction Structure Analysis of a Host–Guest Network: Short Contacts between Tetrathiafulvalene Molecules in a Pore

Martí,‐,Rujas ,, Javier,Islam, Nazrul,Hashizume, Daisuke,Izumi, Fujio,Fujita, Makoto,Song, Hyun Jae,Choi, Hee Cheul,Kawano, Masaki WILEY‐VCH Verlag 2011 Angewandte Chemie Vol.123 No.27

<P><B>Synchrotron‐Pulver‐XRD</B>‐Analysen führten zur Kristallstruktur eines unter kinetischer Kontrolle gebildeten Koordinationspolymers mit großer Elementarzelle (15 729(1) Å<SUP>3</SUP>). In den Poren dieses Gerüsts sind Tetrathiafulvalenmoleküle mit kleinen S<B>⋅⋅⋅</B>S‐Abständen eingeschlossen (siehe Bild).</P>

Crafting Child-friendly Cities: Evidence from Biratnagar Sub-metropolitan City, Eastern Nepal

Bala Raju Nikku,Ruja Pokhrel 한국사회복지학회 2013 Asian Social Work and Policy Review Vol.7 No.2

Our cities are increasingly becoming the sites where children socialize, observe, and learn how societyfunctions and many local and global activities have impacted children’s health and well-being. The Child-friendly Cities initiative, launched by the United Nations Children’s Fund and theUnited Nations Human Settlements Programme in 1996, draws in diverse stakeholders to placechildren at the center of the urban agenda. Based on social work research, this article analyzes theacclaimed status of Biratnagar Sub-metropolitan city, Eastern Nepal, as a child-friendly city. Despite its efforts, the city of Biratnagar is yet to meet the required criteria to claim itself as a childfriendlycity. Further improvements by the city administration in achieving children’s participationin decision-making, child-friendly legal environment, and code of conduct are essential. Based onthe evidence, the authors advocate for bottom-up approaches that include children’s voices andtheir real participation in city governance and a strong political will to craft child-friendly cities,not as a policy rhetoric but for real. Enabling children to fulfill their potential as equal participantsin crafting child-friendly cities will require adults to relinquish some of their hegemonic powers ofdecision-making on behalf of children.