scholarly journals Interplay of Rotational and Pseudorotational Motions in Flexible Cyclic Molecules

2021 ◽  
Author(s):  
Lorenzo Paoloni ◽  
Assimo Maris
Keyword(s):  
Cyclic Molecules

Synthetic Routes to 2-Iminothiazolidines: State-of-the-Art 2006-2020

2020 ◽  
Vol 24 (24) ◽  
pp. 2823-2844
Author(s):  
Aditya Bhattacharyya
Keyword(s):  
State Of The Art ◽  
Biological Significance ◽  
Review Article ◽  
Synthetic Methods ◽  
Pharmacological Properties ◽  
Cyclic Molecules ◽  
Synthetic Routes

: Multiheteroatom-containing small-sized cyclic molecules such as 2- iminothiazolidines are often found to possess beneficial pharmacological properties. In this review article, the biological significance of 2-iminothiazolidines is discussed and the literature reports published in the last 15 years spanning from 2006 to 2020 describing various preparative routes to access 2-iminothiazolidine derivatives have been categorically and chronologically described. The notable synthetic methods discussed here involve ringexpansion transformations of nonactivated and activated aziridines, thiiranes, epoxides, and other miscellaneous reactions.

scholarly journals Impact of Deuteration and Temperature on Furan Ring Dynamics

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2889
Author(s):  
Przemyslaw Dopieralski ◽  
Iryna V. Omelchenko ◽  
Zdzislaw Latajka
Keyword(s):  
Conformational Changes ◽  
Furan Ring ◽  
Computational Studies ◽  
Significant Progress ◽  
Dynamic Simulations ◽  
Cyclic Molecules ◽  
Ring Dynamics ◽  
Different Temperatures ◽  
Long Time ◽  
Shape And Size

Despite significant progress in conformational analysis of cyclic molecules, the number of computational studies is still limited while most of that available in the literature data have been obtained long time ago with outdated methods. In present research, we have studied temperature driven conformational changes of the furan ring at three different temperatures. Additionally, the effect of deuteration on the ring dynamics is discussed; in addition, the aromaticity indices following the Bird and HOMA schemes are computed along all trajectories. Our ab initio molecular dynamic simulations revealed that deuteration has changed the furan ring dynamics and the obvious consequences; in addition, the shape and size of molecule are expected to be different.

scholarly journals Cellular Orientation on Repeatedly Stretching Gelatin Hydrogels with Supramolecular Cross-Linkers

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2095
Author(s):  
Dae Hoon Lee ◽  
Yoshinori Arisaka ◽  
Asato Tonegawa ◽  
Tae Woong Kang ◽  
Atsushi Tamura ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Cellular Response ◽  
Linear Polymer ◽  
Cross Linking ◽  
Adherent Cells ◽  
Cell Cultivation ◽  
Supramolecular Compound ◽  
Synthetic Materials ◽  
Cyclic Molecules

The cytocompatibility of biological and synthetic materials is an important issue for biomaterials. Gelatin hydrogels are used as biomaterials because of their biodegradability. We have previously reported that the mechanical properties of gelatin hydrogels are improved by cross-linking with polyrotaxanes, a supramolecular compound composed of many cyclic molecules threaded with a linear polymer. In this study, the ability of gelatin hydrogels cross-linked by polyrotaxanes (polyrotaxane–gelatin hydrogels) for cell cultivation was investigated. Because the amount of polyrotaxanes used for gelatin fabrication is very small, the chemical composition was barely altered. The structure and wettability of these hydrogels are also the same as those of conventional hydrogels. Fibroblasts adhered on polyrotaxane–gelatin hydrogels and conventional hydrogels without any reduction or apoptosis of adherent cells. From these results, the polyrotaxane–gelatin hydrogels have the potential to improve the mechanical properties of gelatin without affecting cytocompatibility. Interestingly, when cells were cultured on polyrotaxane–gelatin hydrogels after repeated stress deformation, the cells were spontaneously oriented to the stretching direction. This cellular response was not observed on conventional hydrogels. These results suggest that the use of a polyrotaxane cross-linking agent can not only improve the strength of hydrogels but can also contribute to controlling reorientation of the gelatin.

scholarly journals Optically transparent, high-toughness elastomer using a polyrotaxane cross-linker as a molecular pulley

2018 ◽  
Vol 4 (10) ◽  
pp. eaat7629 ◽  
Author(s):  
Hiroaki Gotoh ◽  
Chang Liu ◽  
Abu Bin Imran ◽  
Mitsuo Hara ◽  
Takahiro Seki ◽  
...  
Keyword(s):  
External Force ◽  
Matrix Material ◽  
Three Dimensional ◽  
Cross Linking ◽  
High Toughness ◽  
Dimensional Network ◽  
Cyclic Molecules ◽  
Optically Transparent ◽  
The Matrix ◽  
Special Challenge

An elastomer is a three-dimensional network with a cross-linked polymer chain that undergoes large deformation with a small external force and returns to its original state when the external force is removed. Because of this hyperelasticity, elastomers are regarded as one of the best candidates for the matrix material of soft robots. However, the comprehensive performance required of matrix materials is a special challenge because improvement of some matrix properties often causes the deterioration of others. For example, an improvement in toughness can be realized by adding a large amount of filler to an elastomer, but to the impairment of optical transparency. Therefore, to produce an elastomer exhibiting optimum properties suitable for the desired purpose, very elaborate, complicated materials are often devised. Here, we have succeeded in creating an optically transparent, easily fabricated elastomer with good extensibility and high toughness by using a polyrotaxane (PR) composed of cyclic molecules and a linear polymer as a cross-linking agent. In general, elastomers having conventional cross-linked structures are susceptible to breakage as a result of loss of extensibility at high cross-linking density. We found that the toughness of the transparent elastomer prepared using the PR cross-linking agent is enhanced along with its Young’s modulus as cross-linking density is increased.

scholarly journals The hetero-Friedel-Crafts-Bradsher Cyclizations with Formation of Ring Carbon-Heteroatom (P, S) Bonds, Leading to Organic Functional Materials

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4751
Author(s):  
Joanna Skalik ◽  
Marek Koprowski ◽  
Ewa Różycka-Sokołowska ◽  
Piotr Bałczewski
Keyword(s):  
Flame Retardants ◽  
Bond Formation ◽  
Functional Materials ◽  
Semiconducting Materials ◽  
Conjugated Molecules ◽  
Comprehensive Review ◽  
Ring Carbon ◽  
New Methods ◽  
Cyclic Molecules ◽  
Methods Of Synthesis

The interest in functional materials possessing improved properties led to development of new methods of their synthesis, which allowed to obtain new molecular arrangements with carbon and heteroatom motifs. Two of the classical reactions of versatile use are the Friedel-Crafts and the Bradsher reactions, which in the new heteroatomic versions allow to replace ring carbon atoms by heteroatoms. In the present work, we review methods of synthesis of C–S and C–P bonds utilizing thia- and phospha-Friedel-Crafts-Bradsher cyclizations. Single examples of C–As and lack of C–Se bond formation, involving two of the closest neighbors of P and S in the periodic table, have also been noted. Applications of the obtained π-conjugated molecules, mainly as semiconducting materials, flame retardants, and resins hardeners, designed on the basis of five- and six-membered cyclic molecules containing ring phosphorus and sulfur atoms, are also included. This comprehensive review covers literature up to August 2020.

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