scholarly journals Tuning organic crystal chirality by the molar masses of tailored polymeric additives

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xichong Ye ◽  
Bowen Li ◽  
Zhaoxu Wang ◽  
Jing Li ◽  
Jie Zhang ◽  
...  
Keyword(s):  
Asymmetric Catalysis ◽  
Crystal Engineering ◽  
Building Blocks ◽  
Oriented Attachment ◽  
Organic Crystals ◽  
Chirality Transfer ◽  
Precise Control ◽  
Polymeric Additives ◽  
Scope Of Application ◽  
Chiral Crystals

AbstractHierarchically ordered chiral crystals have attracted intense research efforts for their huge potential in optical devices, asymmetric catalysis and pharmaceutical crystal engineering. Major barriers to the application have been the use of costly enantiomerically pure building blocks and the difficulty in precise control of chirality transfer from molecular to macroscopic level. Herein, we describe a strategy that offers not only the preferred formation of one enantiomorph from racemic solution but also the subsequent enantiomer-specific oriented attachment of this enantiomorph by balancing stereoselective and non-stereoselective interactions. It is demonstrated by on-demand switching the sign of fan-shaped crystal aggregates and the configuration of their components only by changing the molar mass of tailored polymeric additives. Owing to the simplicity and wide scope of application, this methodology opens an immediate opportunity for facile and efficient fabrication of one-handed macroscopic aggregates of homochiral organic crystals from racemic starting materials.

Research Progress on the Catalytic Enantioselective Synthesis of Axially Chiral Allenes by Chiral Organocatalysts

2020 ◽  
Vol 24 (6) ◽  
pp. 694-708 ◽  
Author(s):  
Qing Han Li ◽  
Xin Jiang ◽  
Kun Wu ◽  
Rui Qiang Luo ◽  
Meng Liang ◽  
...  
Keyword(s):  
Asymmetric Catalysis ◽  
Building Blocks ◽  
Enantioselective Synthesis ◽  
Research Progress ◽  
Organic Transformations ◽  
Chirality Transfer ◽  
Reaction Systems ◽  
Axially Chiral ◽  
Nucleophilic Reagents ◽  
Organic Catalysts

Chiral allenes are important structural scaffolds found in many natural products and drugs, and in addition, they also serve as building blocks for many organic transformations. The conventional methods for preparing chiral allenes rely on the resolution of racemic allenes and the chirality transfer between non-racemic propargylic derivatives and nucleophilic reagents. In recent years, the synthesis of chiral allenes by asymmetric catalysis has been achieved fruitful results. Among them, enantioselective synthesis of chiral allenes with chiral organic catalysts is particularly prominent. In this paper, the research progress of enantioselective synthesis of chiral allenes catalyzed by chiral organic catalysts in recent years is reviewed, including various reaction systems and synthesis applications.

Application of Nitrogen Heterocyclic Carbenes in Organocatalysis

2020 ◽  
Vol 09 ◽  
Author(s):  
Minita Ojha ◽  
R. K. Bansal
Keyword(s):  
Asymmetric Catalysis ◽  
Building Blocks ◽  
Structural Features ◽  
Heterocyclic Carbenes ◽  
Stetter Reaction ◽  
Metal Pollutants ◽  
Synthetic Strategy ◽  
Wide Range ◽  
Benzoin Condensation ◽  
Nitrogen Heterocyclic

Background: During the last two decades, horizon of research in the field of Nitrogen Heterocyclic Carbenes (NHC) has widened remarkably. NHCs have emerged as ubiquitous species having applications in a broad range of fields, including organocatalysis and organometallic chemistry. The NHC-induced non-asymmetric catalysis has turned out to be a really fruitful area of research in recent years. Methods: By manipulating structural features and selecting appropriate substituent groups, it has been possible to control the kinetic and thermodynamic stability of a wide range of NHCs, which can be tolerant to a variety of functional groups and can be used under mild conditions. NHCs are produced by different methods, such as deprotonation of Nalkylhetrocyclic salt, transmetallation, decarboxylation and electrochemical reduction. Results: The NHCs have been used successfully as catalysts for a wide range of reactions making a large number of building blocks and other useful compounds accessible. Some of these reactions are: benzoin condensation, Stetter reaction, Michael reaction, esterification, activation of esters, activation of isocyanides, polymerization, different cycloaddition reactions, isomerization, etc. The present review includes all these examples published during the last 10 years, i.e. from 2010 till date. Conclusion: The NHCs have emerged as versatile and powerful organocatalysts in synthetic organic chemistry. They provide the synthetic strategy which does not burden the environment with metal pollutants and thus fit in the Green Chemistry.

Hierarchy of Supramolecular Arrangements and Building Blocks: Inverted Paradigm of Crystal Engineering in the Unprecedented Metal Coordination of Methylene Blue

2017 ◽  
Vol 56 (6) ◽  
pp. 3512-3516 ◽  
Author(s):  
Stefano Canossa ◽  
Alessia Bacchi ◽  
Claudia Graiff ◽  
Paolo Pelagatti ◽  
Giovanni Predieri ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Crystal Engineering ◽  
Building Blocks ◽  
Metal Coordination ◽  
Supramolecular Arrangements

Preparation of Optically Activeα-Amino[3]ferrocenophanes− Building Blocks for Chelate Ligands in Asymmetric Catalysis

2003 ◽  
Vol 2003 (23) ◽  
pp. 4261-4261 ◽  
Author(s):  
Patrick Liptau ◽  
Ludger Tebben ◽  
Gerald Kehr ◽  
Birgit Wibbeling ◽  
Roland Fröhlich ◽  
...  
Keyword(s):  
Asymmetric Catalysis ◽  
Building Blocks ◽  
Chelate Ligands

A threefold interpenetrated two-dimensional zinc(II) supramolecular architecture based on 3-nitrobenzoic acid and 4,4′-bipyridine

2016 ◽  
Vol 72 (2) ◽  
pp. 128-132 ◽  
Author(s):  
Long Tang ◽  
Ji-Jiang Wang ◽  
Feng Fu ◽  
Sheng-Wen Wang ◽  
Qi-Rui Liu
Keyword(s):  
Coordination Polymers ◽  
Crystal Engineering ◽  
Critical Factor ◽  
Building Blocks ◽  
Zigzag Chain ◽  
Great Success ◽  
Supramolecular Architecture ◽  
Two Dimensional ◽  
Hydrothermal Conditions ◽  
Nitrobenzoic Acid

With regard to crystal engineering, building block or modular assembly methodologies have shown great success in the design and construction of metal–organic coordination polymers. The critical factor for the construction of coordination polymers is the rational choice of the organic building blocks and the metal centre. The reaction of Zn(OAc)2·2H2O (OAc is acetate) with 3-nitrobenzoic acid (HNBA) and 4,4′-bipyridine (4,4′-bipy) under hydrothermal conditions produced a two-dimensional zinc(II) supramolecular architecture,catena-poly[[bis(3-nitrobenzoato-κ2O,O′)zinc(II)]-μ-4,4′-bipyridine-κ2N:N′], [Zn(C7H4NO4)2(C10H8N2)]nor [Zn(NBA)2(4,4′-bipy)]n, which was characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction analysis. The ZnIIions are connected by the 4,4′-bipy ligands to form a one-dimensional zigzag chain and the chains are decorated with anionic NBA ligands which interact further through aromatic π–π stacking interactions, expanding the structure into a threefold interpenetrated two-dimensional supramolecular architecture. The solid-state fluorescence analysis indicates a slight blue shift compared with pure 4,4′-bipyridine and HNBA.

scholarly journals Towards computer-guided tuning of the crystal packing of porous organic cages

2014 ◽  
Vol 70 (a1) ◽  
pp. C667-C667
Author(s):  
Angeles Pulido ◽  
Ming Liu ◽  
Paul Reiss ◽  
Anna Slater ◽  
Sam Chong ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Engineering ◽  
Molecular Sieves ◽  
Structure Prediction ◽  
Crystal Packing ◽  
Aromatic Aldehydes ◽  
Lattice Energy ◽  
Building Blocks ◽  
Molecular Assembly ◽  
Computational Techniques

Among microporous materials, there has been an increasing recent interest in porous organic cage (POC) crystals, which can display permanent intrinsic (molecular) and extrinsic (crystal network) porosity. These materials can be used as molecular sieves for gas separation and potential applications as enzyme mimics have been suggested since they exhibit structural response toward guest molecules[1]. Small structural modifications of the initial building blocks of the porous organic molecules can lead to quite different molecular assembly[1]. Moreover, the crystal packing of POCs is based on weak molecular interactions and is less predictable that other porous materials such as MOFs or zeolites.[2] In this contribution, we show that computational techniques -molecular conformational searches and crystal structure prediction- can be successfully used to understand POC crystal packing preferences. Computational results will be presented for a series of closely related tetrahedral imine- and amine-linked porous molecules, formed by [4+6] condensation of aromatic aldehydes and cyclohexyl linked diamines. While the basic cage is known to have one strongly preferred crystal structure, the presence of small alkyl groups on the POC modifies its crystal packing preferences, leading to extensive polymorphism. Calculations were able to successfully identify these trends as well as to predict the structures obtained experimentally, demonstrating the potential for computational pre-screening in the design of POCs within targeted crystal structures. Moreover, the need of accurate molecular (ab initio calculations) and crystal (based on atom-atom potential lattice energy minimization) modelling for computer-guided crystal engineering will be discussed.

scholarly journals Exploring the Internal Radiative Efficiency of Selective Area Nanowires

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
A. Cavalli ◽  
J. E. M. Haverkort ◽  
E. P. A. M. Bakkers
Keyword(s):  
Solar Cell ◽  
High Growth ◽  
Optical Emission ◽  
Building Blocks ◽  
Growth Conditions ◽  
Material System ◽  
Solar Cell Application ◽  
Precise Control ◽  
Radiative Efficiency ◽  
Selective Area

Nanowires are ideal building blocks for next-generation solar cell applications. Nanowires grown with the selective area (SA) approach, in particular, have demonstrated very high material quality, thanks to high growth temperature, defect-free crystalline structure, and absence of external catalysts, especially in the InP material system. A comprehensive study on the influence of growth conditions and device processing on optical emission is still necessary though. This article presents an investigation of the nanowire optical properties, performed in order to optimize the internal radiative efficiency. In an initial preamble, the motivation for this study is discussed, as well as the morphology and crystallinity of the nanowires. The effect on the nanowire photoluminescence of several intrinsic and extrinsic parameters and factors are then presented in three sections: first, the influence of basic growth conditions such as the temperature and the precursor ratio is studied. Subsequently, the effects of varying dopant molar flows are explored, keeping in mind the intended solar cell application. Third, the manner in which the processing and the passivation affect the nanowire optical emission is discussed. Precise control of the growth conditions allows maximizing the nanowire internal radiative efficiency and thus their performance in solar cells and other optoelectronic devices.

Directional control of π-stacked building blocks for crystal engineering: the 1,8-naphthalimide synthon

2005 ◽  
pp. 4068 ◽  
Author(s):  
Daniel L. Reger ◽  
J. Derek Elgin ◽  
Radu F. Semeniuc ◽  
Perry J. Pellechia ◽  
Mark D. Smith
Keyword(s):  
Crystal Engineering ◽  
Building Blocks ◽  
Directional Control
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