M. B. Avinash

Two-dimensional nanoarchitectonics: organic and hybrid materials.

Programmed molecular assemblies with molecular-level precision have always intrigued mankind in the quest to master the art of molecular engineering. In this regard, our review seeks to highlight the state of the art in supramolecular engineering. Herein we describe two-dimensional (2D) nanoarchitectonics of organic and organic-inorganic based hybrid materials. Molecular systems ranging from simpler hydrogen bonding driven bis-acylurea and cyclic dipeptide derivatives to complex peptoids, arylenes, cucurbiturils, biphenyls, organosilicons and organometallics, which involve a delicate interplay of multiple noncovalent interactions are discussed. These specifically chosen examples illustrate the molecular design principles and synthetic protocols to realize 2D nanosheets. The description also emphasizes the wide variety of functional properties and technological implications of these 2D nanomaterials besides an outlook for future progress.

Amino acid derivatized arylenediimides: a versatile modular approach for functional molecular materials.

Natures elegant molecular designs and their assemblies with specific structure-property correlations have inspired researchers to design and develop bio-mimics for advanced functional applications. To realize such advanced molecular materials, naturally evolved amino acids are arguably the ideal auxiliaries due to their remarkable molecular/chiral recognition and distinctive sequence specific self-assembling properties. Over the years, this modular approach of derivatizing naphthalenediimides (NDIs) and perylenediimides (PDIs) with amino acids and peptides have resulted in several hitherto unknown molecular assemblies with phenomenal impact on their performance. Derivatization with versatile arylenediimides is especially interesting due to their wide spread applications in fields ranging from biomedicine to electronics. Herein some of these seminal reports of this rapidly emerging field and the design principles embraced are discussed.

Self‐Cleaning Functional Molecular Materials

The controlled self-assembly of small molecules into welldefined, ordered nanoand microstructures is of current interest for potential applications in photavoltaics, photonic crystals, tissue engineering, single-cell analysis, microreactors, and superhydrophobic coatings. This bottom-up molecular assembly approach has been elegantly utilized by nature to form a variety of functional nanomaterials. However, it is only now that chemists have begun to understand the underlying supramolecular design principles in an ongoing effort to construct ordered two-dimensional (2D) or three-dimensional (3D) patterns and arrays, which could ultimately lead to complex architectures and functions. In this context, superhydrophobic surfaces in particular have come into focus in recent years, partly by the motivation to mimic nature and owing to their promising applications. Over the years, a variety of chemical and physical methods for the fabrication of rough surfaces with subsequent low-surface-energy coatings have been explored by lithography, sublimation, plasma techniques, self-assembled monolayers (SAM), and electrochemical methods. Furthermore, the so called breath-figure technique (BFT) has also been explored owing to its simple solution processability, robustness, and the excellent tunability of size over three orders of magnitude (nm to mm). When a solution is drop-cast on a surface under humid air, the evaporation of the volatile solvent facilitates condensation of water droplets on the cold surface. This evaporative cooling and subsequent solidification of the solute under favorable conditions produces highly ordered arrays of well-defined cavities with diameters of 50 nm to 20 mm, called breath-figure arrays. However, the use of BFT has been limited to date to certain classes of macromolecules, such as star polymers, cross-linked star polymers, hyperbranched polymers, conjugated polymers, and dendronized polymers, with an exception of only a few organogelators. It has been argued that viscous polymer solutions with additional polar functionalities are required in BFT to form a stable interface with the water droplet. In contrast, small molecules either crystallize or unspecifically aggregate and thus lack the ability to stabilize water rafts. Herein, we report our serendipitous discovery that a naphthalene diimide (NDI)-based molecule 1 forms highly-ordered self-assembled breath-figure arrays from

Extremely Slow Dynamics of an Abiotic Helical Assembly: Unusual Relevance to the Secondary Structure of Proteins.

Serendipitously, we found that isoleucine methylester functionalized perylenediimide 1 undergoes an extremely slow supramolecular helical assembly over a days time. Surprisingly, heating led to irreversible chiral denaturation. However, reversible helical assembly could be achieved only in the presence of nondenatured aggregates of 1, which act as seeds. The intriguing functional relevance deduced from 1 was employed to draw parallels with the secondary structure of proteins, envisaging its plausible implications.

Exploring hydrogen bonding and weak aromatic interactions induced assembly of adenine and thymine functionalised naphthalenediimides

Adenine and thymine functionalised naphthalenediimide (NDI) conjugates and complementary peptide nucleic acid (PNA) dimers are designed to exploit complementary hydrogen bonding and aromatic interactions for controllable molecular organization. These nucleobase appended NDIs organized into well-defined fibers, nanoribbons, porous spheres, belts and petal-like 2D sheets.

Bioinspired Reductionistic Peptide Engineering for Exceptional Mechanical Properties

A simple solution-processing and self-assembly approach that exploits the synergistic interactions between multiple hydrogen bonded networks and aromatic interactions was utilized to synthesize molecular crystals of cyclic dipeptides (CDPs), whose molecular weights (~0.2 kDa) are nearly three orders of magnitude smaller than that of natural structural proteins (50–300 kDa). Mechanical properties of these materials, measured using the nanoindentation technique, indicate that the stiffness and strength are comparable and sometimes better than those of natural fibres. The measured mechanical responses were rationalized by recourse to the crystallographic structural analysis and intermolecular interactions in the self-assembled single crystals. With this work we highlight the significance of developing small molecule based bioinspired design strategies to emulate biomechanical properties. A particular advantage of the successfully demonstrated reductionistic strategy of the present work is its amenability for realistic industrial scale manufacturing of designer biomaterials with desired mechanical properties.