Molecular Crystals with Dimensionally Controlled Hydrogen-Bonded Nanostructures

Abstract

Molecular crystals constructed by hydrogen bonding can be viewed as having nanostructural elements consisting of ordered, supramolecular hydrogen-bonded networks. These networks, whose dimensionalities and motifs are governed by the molecular structure and hydrogen-bonding topology of their constituents, can serve as “modules” in the design and synthesis of molecular materials. Robust supramolecular modules can reduce significantly the number of possible solid-state packing motifs, a key goal of crystal engineering strategies which aim to design and synthesize molecular solids with controlled solid-state structure and properties. Several examples of hydrogen bonded modules in molecular crystals are described, including one-dimensional hydrogen-bonded wires, two-dimensional hydrogen-bonded layers, and nanoporous hydrogen-bonded lattices with voids having differing dimensionalities. The presence of reliable modules in these materials provides for a better general understanding of the organization principles governing molecular and solid-state assembly by reducing the number of variables in systematic studies.

Pnicogen Bonds: A New Molecular Linker?

“…2) The P À P nonbonding interactions are strongest if a good leaving group like Br is the substituent along to the P···P axis, for example 18 (-Br)!6 (-Cl)!22 (-CCH)!12 (-F) !21 (-CH 3 ). An exception are the structures with a hydrogen substituent perpendicular to the P···P axis, for which the inverse trend can be observed.…”

“…Figure 5. Electrostatic potential at the isodensity surface with 0.01 e bohr 3 Br, and l) CF 3 I. Negatively charged regions are colored black.…”

Functional Porous Structures Based on the Pyrolysis of Cured Templates of Block Copolymer and Phenolic Resin

“…Typically, nanoporous materials are crystalline framework solids, such as zeolites, discotic molecular assemblies, [31][32][33] or "robust" molecular crystals formed using supramolecular [38] design principles. [2,[11][12][13][14][15][16][17][18][19][20] These materials can have large void volumes and high internal surface areas, but the supramolecular materials often tend to collapse upon emptying the pores. Several approaches have also been presented to prepare mesoporous and macroporous materials, such as "track-etching", [4][5][6] using honeycomb structures, [27][28][29] and emptying nanostructured templates (e.g., sol-gel processing of surfactants or block copolymers, [7][8][9][10] selective degradation of material with UV exposure, [24][25][26] pyrolysis, [21][22][23]34] and selective removal of lowmolecular-weight amphiphiles (combs) from hierarchically self-assembled polymeric comb-coil supramolecules [35,36] ).…”

Crystal Engineering: Strategies and Architectures

“…Manuscripts dealing specifically with 'designer-architectures' and with strategies for controlling and predicting structures are published on a regular basis, and several review articles (Lehn, 1988(Lehn, , 1990Aaker6y & Seddon, 1993;Braga & Grepioni, 1996;Russel & Ward, 1996;Subramanian & Zaworotko, 1994;Desiraju, 1995a;Rebek, 1996) and books (Desiraju, 1989(Desiraju, , 1995bV'6gtle, 1991;Lehn, 1995)have provided valuable overviews of the exciting and inspiring research efforts that have been presented during the last decade.…”