Crystals engineering

In the case of [14](4.2.2)DBA4b, too, polymorphs were formed depending on the conditions of crystal growth due to different intermolecular C-H/O interaction modes [67]. Depending on the crystal morphology, different fluorescence spectra, lifetimes, and photoconductivities were observed due to the different defects in crystals. Crystals of 4b containing various aromatic guest molecules were also reported [68]. 

3D Assemblies Gels, Fibers, Vesicles, and Liquid Crystals 

In addition to the desymmetrized DBAs, DBA derivatives bearing peripheral % systems that tend to stack each other were also reported to form fibrous or gel-like self-assembled materials. These include those from TTF-fused [18] (4.4.4)DB A 7b of 50-500nm thickness obtained from aqueous THF [19], [12](4.4)DBAs 8a,b, and [18](4.4.4)DBAs 9a,b with phenanthrene units of various dimensions formed from a mixture of chloroform and ethanol by molecular stacking along the growth direction, as deduced by wide-angle X-ray diffraction (WXRD) [21]. 

Control over the self-assembly of molecular building blocks into well-defined architectures at surfaces represents one of the most important challenges of supramolecular chemistry. Self-assembled 2D monolayers formed by physisorp-tion of organic molecules have attracted a great deal of interest in view of their potential applications to molecular electronics, sensing via molecular and chiral recognition, and the formation of 2D polymers [76, 77]. In particular, 2D porous 

Double DBAs 25a-c bearing six alkyl chains also formed porous networks of Kagome type via van der Waals linkages formed by interdigitation of three alkyl chains [91]. Although several different patterns were formed in this case, at very low concentration the Kagome phase was formed exclusively. 

Supramolecular Chemistry, 2nd edition J. W. Steed and J. L. Atwood 2009 John Wiley Sons, Ltd ISBN 978-0-470-51233-3 

Reason and imagination come into play simultaneously in the quest for new functionalised solids, 

A tennis-ball-shaped molecular aggregate can be constructed by the self-assembly of curved molecule I. Tetrameric assembly of II generates a pseudo-spherical capsule. Dimeric assembly of III can be induced by the encapsulation of smaller molecules of appropriate size and shape at the center of a spherical complex. 

The determination of crystal structures by X-ray crystallography provides precise and unambiguous data on intermolecular interactions. Crystal engineering has been defined by Desiraju as the understanding of intermolecular interactions in the context of crystal packing and in the utilization of such knowledge in the design of new solids with desired physical and chemical properties.  

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G. Desiraju, Crystal Engineering, Materials Science Monographs, Vol. 54, Elsevier, Amsterdam, 1989. 

J.E. thanks the European Union (Project Localization and Transfer of Hydrogen, No. CHRX CT 940582) and the Spanish Ministry of Education (Project Crystal Engineering, No. PB96-0001-C03-03) for financial support. We thank Dr. Scott Henderson for help with the preparation of the manuscript. 

Hydrogen-Bonded Ribbons, Tapes and Sheets as Motifs for Crystal Engineering... 

VI. PREDESIGNED THREE-DIMENSIONAL SELF-ASSEMBLY OF PROTEINS CRYSTAL ENGINEERING ... 

Since diamondoids possess the capability for derivatization, they can be used to achieve suitable molecular geometries needed for MBBs of nanotechnology. Functionalization by different groups can produce appropriate reactants for desired reactions, microelectronics, and optics, by employing polymers, films, and crystal engineering. 

One of the branches of nanotechnology is called crystal engineering. Crystal engineering is a new concept through which the power of noncovalent... 

The approach in crystal engineering is to learn from known crystalline structures of, for example, minerals in order to design compounds with desired properties. Crystal engineering is considered to be a key new technology with applications in pharmaceuticals, catalysis, and materials science. The structures of adamantane and other diamondoids have received considerable attention in crystal engineering due to their molecular stiffness, derivatization capabilities, and their six or more linking groups [114-117]. 

Crystal engineering. Utilization of noncovalent intermolecular forces in the solid state to design new nanomaterials with desired functions. 

Crystal Engineering Using Multiple Hydrogen Bonds A. D. Burrows... 

Keywords Halogen bonding Supramolecular chemistry Crystal engineering Tecton Topology... 

Both theoretical and experimental data (in the solid, liquid, and gas phases) prove that the tendency of halocarbons to work as XB donors decreases in the order I > Br > Cl [66-68]. Clearly, polarizability and not electronegativity plays a key role. 3-Halo-cyanoacetylene works as self-complementary module and the N X distance is beautifully consistent with the scale reported above, being 2.932, 2.978 and 2.984 A in the iodo, bromo and chloro derivatives, respectively [69,70]. The same trend is observed when a phenyl, rather than a triple bond, spaces the donor and acceptor sites. The N Br distance in 4-bromobenzonitrile is longer than in the 4-iodo derivative [71,72] and no XB is present in the chloro and fluoro analogues, wherein molecules are pinned by N H and X- H short contacts [73]. PFCs have a very poor tendency, if any, to work as XB donors [74-77] and no crystal engineering can be based on such tectons. However, F2 is a quite strong XB donor and several adducts have been described in the gas phase [11,18] (see also the chapter by Legon in this volume). 

Keywords Crystal engineering Halogen bonding Nitroxide Tetrathiafulvalene... 

Desiraju GR (1989) In Crystal engineering the design of organic solids. Elsevier, Amsterdam... 

Braga D, Maini L, Polito M, Grepioni F (2004) Hydrogen Bonding Interactions Between Ions A Powerful Tool in Molecular Crystal Engineering 111 1-32 Brechin EK, see Aromf G (2006) 122 1-67... 

Burrows AD (2004) Crystal Engineering Using Multiple Hydrogen Bonds 108 55-96 Bussmann-Holder A, Dalai NS (2007) Order/Disorder Versus or with Displacive Dynamics in Ferroelectric Systems. 124 1-21... 

Metrangolo P, Resnati G, Pilati T, Biella S (2007) Halogen Bonding in Crystal Engineering. 126 105-136... 

Braga D, D Addario D, Giaffreda SL, Maini L, Polito M, Grepioni F (2005) Intra-Solid and Inter-Solid Reactions of Molecular Crystals a Green Route to Crystal Engineering. 254 71-94... 

Trask AV, Jones W (2005) Crystal Engineering of Organic Cocrystals by the Solid-State Grinding Approach. 254 41-70 Tuntulani T, see Suksai C (2005) 255 163-198... 

In recent years research in the field of transition-metal thiocyanates and selenocyanates received a new impetus, because of the partly interesting physical properties of such crystalline species. A review on Cd and Hg thiocyanate systems collects and sorts results of this endeavor.371 The nonlinear optical (NLO) properties of Cd thiocyanate and selenocyanate systems and criteria for the design of NLO crystals (crystal engineering), especially, have been discussed afterwards.372 Further contributions to the field have also been described.37, 374 The structure of mercury chlorothiocyanate has been re-determined.375... 

P York. Crystal engineering and particle design for the powder compaction process. Drug Dev Ind Pharm 18(6-7) 677—721, 1992. 

Sharma KCV (2002) Crystal engineering - where do we go from here Cryst Growth Des 2(6) 465 174... 

Cf. e.g. the reviews on Conformational Polymorphism by J. Berstein in Organic Solid State Chemistry (Ed. G. R. Desiraju), Elsevier Amsterdam 1987, p. 471 or by G. R. Desiraju, Crystal Engineering, Material Science Monographs 54, Elsevier, Amsterdam 1989, p. 285. 

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