Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

The Halogen Bond

In this Review, we aim to provide an updated summary of the research related to hollow micro- and nanostructures, covering both their synthesis and their applications. After a brief introduction to the definition and classification of the hollow micro-/nanostructures, we discuss various synthetic strategies that can be grouped into three major categories, including hard templating, soft templating, and self-templating synthesis. For both hard and soft templating strategies, we focus on how different types of templates are generated and then used for creating hollow structures. At the end of each section, the structural and morphological control over the product is discussed. For the self-templating strategy, we survey a number of unconventional synthetic methods, such as surface-protected etching, Ostwald ripening, the Kirkendall effect, and galvanic replacement. We then discuss the unique properties and niche applications of the hollow structures in diverse fields, including micro-/nanocontainers and rea...

Synthesis, Properties, and Applications of Hollow Micro-/Nanostructures

Hollow-structured mesoporous materials (HMMs), as a kind of mesoporous material with unique morphology, have been of great interest in the past decade because of the subtle combination of the hollow architecture with the mesoporous nanostructure. Benefitting from the merits of low density, large void space, large specific surface area, and, especially, the good biocompatibility, HMMs present promising application prospects in various fields, such as adsorption and storage, confined catalysis when catalytically active species are incorporated in the core and/or shell, controlled drug release, targeted drug delivery, and simultaneous diagnosis and therapy of cancers when the surface and/or core of the HMMs are functionalized with functional ligands and/or nanoparticles, and so on. In this review, recent progress in the design, synthesis, functionalization, and applications of hollow mesoporous materials are discussed. Two main synthetic strategies, soft-templating and hard-templating routes, are broadly sorted and described in detail. Progress in the main application aspects of HMMs, such as adsorption and storage, catalysis, and biomedicine, are also discussed in detail in this article, in terms of the unique features of the combined large void space in the core and the mesoporous network in the shell. Functionalization of the core and pore/outer surfaces with functional organic groups and/or nanoparticles, and their performance, are summarized in this article. Finally, an outlook of their prospects and challenges in terms of their controlled synthesis and scaled application is presented.

Hollow‐Structured Mesoporous Materials: Chemical Synthesis, Functionalization and Applications

Surface chemistry of porphyrins and phthalocyanines

Solvent-Dependent Molecular Isomerization and 2D Self-Assembled Phase Transitions of Benzothiadiazole-Based π-Conjugated Fluorophore

Fabrication of structural diversity in self-assembled monolayers has gained considerable attention, not only due to its significance in interface science but also because of its potential application in designing nanomaterials. Here, systematical characterization of the molecular self-assembly of tri-substituted anthraquinone derivatives at the 1-octanoic acid/HOPG interface is provided. Different nanopatterns of Linear I, Butterfly-like, and Linear II are recorded for 1,2,4-A-3OC16 by gradually changing the solution concentration. Diverse polymorphs are also obtained by alkyl chain elongation, meaning that 1,2,4-A-3OC15,17,18 adopt Dimer-Linear, Linear III, and Linear IV structures, respectively. Dipole–dipole, hydrogen bonding, and van der Waals interactions are the dominant forces on forming the stable adlayers. Also, the coadsorption of the solvent molecules is a common phenomenon, ascribing to space matching and gain of enthalpy. Moreover, the 1,2,4-A-3OC17,18 self-assembled into monolayers consists of both ordered and chaotic domains. This loss of regularity is attributed to the large number and long length of the side chains, for entropy reasons. This work provides important insight into the fabrication of complex molecular self-assembly and the exploration of monolayers at the liquid/solid interface.

STM Exploration of the Diverse Polymorphs for Tri‐Substituted Anthraquinone Derivatives via Alkyl Chain Elongation

Probing the halogen-bonded nanostructures of two-dimensional (2D) supramolecular self-assembly is essential to understand and engineer the nature of halogen bonding. However, exploring the formatio...

Solvent Effect on Halogen-Bonded Self-Assembled Nanostructures of a 2,9-Dibromo-Phenanthridine Derivative at the Liquid–Solid Interface

Supramolecular self-assemblies of bromine-substituted benzene and naphthalene derivatives (Br-BC16 and Br-NC16) are investigated using scanning tunneling microscopy at the liquid/solid interface. These two molecules arrange in different linear patterns stabilized by intermolecular H···Br and Br···Br bonds. Because of the different geometry symmetry of conjugated cores along the C–Br bond, the side chains and conjugated cores of Br-BC16 pack with the same direction; however, the side chains of Br-NC16 stretch into different directions along the graphite lattices and the conjugated cores of Br-NC16 in each dimer adopt the reverse orientation. Electrostatic potential maps and density functional theory calculations show that a pair of intermolecular H···Br bonds between the hydrogen atoms with the positive charge and the bromine atoms with the negative charge in each dimer dominate the structural formation. In addition, a Br···Br bond in each dimer for Br-BC16 and a Br···Br bond between the neighboring dimers...

Geometry Symmetry of Conjugated Cores along C–Br Bond Effect on the 2D Self-Assembly by Intermolecular H···Br and Br···Br Bonds

We reported the synthesis, characterization, and self-assembly of two new regioisomeric π-conjugated chromophores (p-DBPy and d-DBPy) based on pyridyl-flanked diketopyrrolopyrrole (DPP), where the nitrogen atom in the pyridyl was proximal or distal to the central DPP unit. Their solid powders and solutions displayed different colors, especially for p-DBPy, which could be attributed to the conversion of molecular conformation and different intermolecular aggregations. UV–vis spectra demonstrated that the possible intermolecular hydrogen bonding existed in the solution of p-DBPy. Of particular interest is that the morphology of solid powders and thin films for each molecule investigated by SEM and AFM, respectively, were dramatically different owing to different intermolecular interactions and different crystal growth speed. Their spectroscopic and electrochemical properties turned out to be strongly dependent on the orientation of the pyridyl group. DFT calculations were performed to determine the optimize...

Wenli Deng

Papers

Solvent-Dependent Molecular Isomerization and 2D Self-Assembled Phase Transitions of Benzothiadiazole-Based π-Conjugated Fluorophore

STM Exploration of the Diverse Polymorphs for Tri‐Substituted Anthraquinone Derivatives via Alkyl Chain Elongation

Solvent Effect on Halogen-Bonded Self-Assembled Nanostructures of a 2,9-Dibromo-Phenanthridine Derivative at the Liquid–Solid Interface

Geometry Symmetry of Conjugated Cores along C–Br Bond Effect on the 2D Self-Assembly by Intermolecular H···Br and Br···Br Bonds

Effect of Pyridyl Orientation on the Molecular Conformation and Self-Assembled Morphology of Regioisomeric Diketopyrrolopyrrole Derivatives