scholarly journals Distinct Helical Molecular Orbitals Through Conformational Lock

2020 ◽  
Author(s):  
Ani Ozcelik ◽  
Daniel Aranda Ruiz ◽  
Sara Gil-Guerrero ◽  
Xaquín A. Pola-Otero ◽  
Maria Talavera ◽  
...  
Keyword(s):  
Computational Analysis ◽  
Energy Difference ◽  
Molecular Orbitals ◽  
Theoretical Studies ◽  
Full Characterization ◽  
Exciton Coupling ◽  
Synthetic Strategy ◽  
Optical Responses ◽  
Novel Strategy

Several theoretical studies have proposed strategies to reach helical molecular orbitals (Hel-MOs) in [n]cumulenes. While chiral even-[n] cumulenes feature Hel-MOs, odd-[n] cumulenes may also present them if the terminal groups lie on different planes. However, the hitherto proposed systems have been either experimentally unfeasible or resulted in opposite pseudo-degenerated Hel-MOs, impeding their use in real applicatons. To overcome this challenge, we hereby demonstrate the introduction of a remarkable energy difference between helical orbitals of opposite twist by fixing the torsion angle between the terminal groups in butadiyne fragments. In order to experimentally lock the conformation of the terminal groups, we designed cyclic architectures by combining acetylenes with chiral spirobifluorenes. A straightforward synthetic strategy along with the high stability allowed the isolation and full characterization of systems presenting distinct helical orbitals. Finally, a thorough computational analysis revealed that the most significant optical responses of these systems originate mainly from the exciton coupling between the featured diphenylbutadiyne fragments. This novel strategy opens now access to the development of systems with distinct helical molecular orbitals suitable for their implementation into chiroptical and optoelectronic applications.

scholarly journals Distinct Helical Molecular Orbitals Through Conformational Lock

2020 ◽  
Author(s):  
Ani Ozcelik ◽  
Daniel Aranda Ruiz ◽  
Sara Gil-Guerrero ◽  
Xaquín A. Pola-Otero ◽  
Maria Talavera ◽  
...  
Keyword(s):  
Computational Analysis ◽  
Energy Difference ◽  
Molecular Orbitals ◽  
Theoretical Studies ◽  
Full Characterization ◽  
Exciton Coupling ◽  
Synthetic Strategy ◽  
Optical Responses ◽  
Novel Strategy

Several theoretical studies have proposed strategies to reach helical molecular orbitals (Hel-MOs) in [n]cumulenes. While chiral even-[n] cumulenes feature Hel-MOs, odd-[n] cumulenes may also present them if the terminal groups lie on different planes. However, the hitherto proposed systems have been either experimentally unfeasible or resulted in opposite pseudo-degenerated Hel-MOs, impeding their use in real applicatons. To overcome this challenge, we hereby demonstrate the introduction of a remarkable energy difference between helical orbitals of opposite twist by fixing the torsion angle between the terminal groups in butadiyne fragments. In order to experimentally lock the conformation of the terminal groups, we designed cyclic architectures by combining acetylenes with chiral spirobifluorenes. A straightforward synthetic strategy along with the high stability allowed the isolation and full characterization of systems presenting distinct helical orbitals. Finally, a thorough computational analysis revealed that the most significant optical responses of these systems originate mainly from the exciton coupling between the featured diphenylbutadiyne fragments. This novel strategy opens now access to the development of systems with distinct helical molecular orbitals suitable for their implementation into chiroptical and optoelectronic applications.

scholarly journals Terminal and Internal Alkyne Complexes and Azide-Alkyne Cycloaddition Chemistry of Copper(I) Supported by a Fluorinated Bis(pyrazolyl)borate

Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 16
Author(s):  
Anurag Noonikara-Poyil ◽  
Alvaro Muñoz-Castro ◽  
H. V. Rasika Dias
Keyword(s):  
Coordination Chemistry ◽  
Copper Complexes ◽  
Computational Analysis ◽  
Copper Catalyst ◽  
Dinuclear Complexes ◽  
Orbital Contribution ◽  
Full Characterization ◽  
Alkyne Complexes ◽  
Internal Alkyne

Copper plays an important role in alkyne coordination chemistry and transformations. This report describes the isolation and full characterization of a thermally stable, copper(I) acetylene complex using a highly fluorinated bis(pyrazolyl)borate ligand support. Details of the related copper(I) complex of HCºCSiMe3 are also reported. They are three-coordinate copper complexes featuring η2-bound alkynes. Raman data show significant red-shifts in CºC stretch of [H2B(3,5-(CF3)2Pz)2]Cu(HCºCH) and [H2B(3,5-(CF3)2Pz)2]Cu(HCºCSiMe3) relative to those of the corresponding alkynes. Computational analysis using DFT indicates that the Cu(I) alkyne interaction in these molecules is primarily of the electrostatic character. The π-backbonding is the larger component of the orbital contribution to the interaction. The dinuclear complexes such as Cu2(μ-[3,5-(CF3)2Pz])2(HCºCH)2 display similar Cu-alkyne bonding features. The mononuclear [H2B(3,5-(CF3)2Pz)2]Cu(NCMe) complex catalyzes [3+2] cycloadditions between tolyl azide and a variety of alkynes including acetylene. It is comparatively less effective than the related trinuclear copper catalyst {μ-[3,5-(CF3)2Pz]Cu}3 involving bridging pyrazolates.

scholarly journals Reviving the Coordination Chemistry of Sulfonium Cations

2021 ◽  
Author(s):  
Ruiping Li ◽  
Nitsan Barel ◽  
Vasudevan Subramaniyan ◽  
Orit Cohen ◽  
Francoise Tibika ◽  
...  
Keyword(s):  
Coordination Chemistry ◽  
Computational Analysis ◽  
Acid Catalysis ◽  
Phosphine Ligands ◽  
Pincer Complexes ◽  
Full Characterization ◽  
Sulfonium Ions ◽  
The Stability ◽  
First Time

ABSTRACT: More than a century old, sulfonium ions are still intriguing species in the landscape of organic chemistry. On one hand they have found broad applications in organic synthesis and material science, but on the other hand, while isoelectronic to the ubiquitous tertiary phosphine ligands, their own coordination chemistry has been neglected for the last three decades. Here we report the synthesis and full characterization of the first Rh(I) and Pt(II) complexes of sul-fonium. Moreover, for the first time, the coordinating ability of an aromatic sulfonium has been established. A thorough computational analysis of the exceptionally short S-Rh bonds obtained attests for the strongly π-accepting nature of sul-fonium cations and places them among the best π-acceptor ligands available today. Our calculations also show that when embedded within a pincer framework their π-acidity is enhanced. Therefore, in addition to the stability and modularity that these frameworks offer, our pincer complexes might open the way for sulfonium cations to become powerful tools in π-acid catalysis.

A Thorough Theoretical Exploration of Intriguing Characteristics of Cyclo[18]carbon: Geometry, Bonding Nature, Aromaticity, Weak Interaction, Reactivity, Excited States, Vibrations, Molecular Dynamics and Various Molecular Properties

2019 ◽  
Author(s):  
Tian Lu ◽  
Qinxue Chen ◽  
Zeyu Liu
Keyword(s):  
Molecular Dynamics ◽  
Excited States ◽  
Electronic Excitation ◽  
Ring Structure ◽  
Molecular Properties ◽  
Molecular Vibration ◽  
Full Characterization ◽  
Long Time ◽  
Almost All

Although cyclo[18]carbon has been theoretically and experimentally investigated since long time ago, only very recently it was prepared and directly observed by means of STM/AFM in condensed phase (Kaiser et al., <i>Science</i>, <b>365</b>, 1299 (2019)). The unique ring structure and dual 18-center π delocalization feature bring a variety of unusual characteristics and properties to the cyclo[18]carbon, which are quite worth to be explored. In this work, we present an extremely comprehensive and detailed investigation on almost all aspects of the cyclo[18]carbon, including (1) Geometric characteristics (2) Bonding nature (3) Electron delocalization and aromaticity (4) Intermolecular interaction (5) Reactivity (6) Electronic excitation and UV/Vis spectrum (7) Molecular vibration and IR/Raman spectrum (8) Molecular dynamics (9) Response to external field (10) Electron ionization, affinity and accompanied process (11) Various molecular properties. We believe that our full characterization of the cyclo[18]carbon will greatly deepen researchers' understanding of this system, and thereby help them to utilize it in practice and design its various valuable derivatives.

A Thorough Theoretical Exploration of Intriguing Characteristics of Cyclo[18]carbon: Geometry, Bonding Nature, Aromaticity, Weak Interaction, Reactivity, Excited States, Vibrations, Molecular Dynamics and Various Molecular Properties

2019 ◽  
Author(s):  
Tian Lu ◽  
Qinxue Chen ◽  
Zeyu Liu
Keyword(s):  
Molecular Dynamics ◽  
Excited States ◽  
Electronic Excitation ◽  
Ring Structure ◽  
Molecular Properties ◽  
Molecular Vibration ◽  
Full Characterization ◽  
Long Time ◽  
Almost All

Although cyclo[18]carbon has been theoretically and experimentally investigated since long time ago, only very recently it was prepared and directly observed by means of STM/AFM in condensed phase (Kaiser et al., <i>Science</i>, <b>365</b>, 1299 (2019)). The unique ring structure and dual 18-center π delocalization feature bring a variety of unusual characteristics and properties to the cyclo[18]carbon, which are quite worth to be explored. In this work, we present an extremely comprehensive and detailed investigation on almost all aspects of the cyclo[18]carbon, including (1) Geometric characteristics (2) Bonding nature (3) Electron delocalization and aromaticity (4) Intermolecular interaction (5) Reactivity (6) Electronic excitation and UV/Vis spectrum (7) Molecular vibration and IR/Raman spectrum (8) Molecular dynamics (9) Response to external field (10) Electron ionization, affinity and accompanied process (11) Various molecular properties. We believe that our full characterization of the cyclo[18]carbon will greatly deepen researchers' understanding of this system, and thereby help them to utilize it in practice and design its various valuable derivatives.

Computationally Augmented Retrosynthesis: Total Synthesis of Paspaline A and Emindole PB

2018 ◽  
Author(s):  
Timothy Newhouse ◽  
Daria E. Kim ◽  
Joshua E. Zweig
Keyword(s):  
Chemical Synthesis ◽  
Total Synthesis ◽  
Small Molecules ◽  
First Principles ◽  
Quantum Chemical ◽  
Computational Analysis ◽  
Empirical Evaluation ◽  
Synthetic Strategy ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions

The diverse molecular architectures of terpene natural products are assembled by exquisite enzyme-catalyzed reactions. Successful recapitulation of these transformations using chemical synthesis is hard to predict from first principles and therefore challenging to execute. A means of evaluating the feasibility of such chemical reactions would greatly enable the development of concise syntheses of complex small molecules. Herein, we report the computational analysis of the energetic favorability of a key bio-inspired transformation, which we use to inform our synthetic strategy. This approach was applied to synthesize two constituents of the historically challenging indole diterpenoid class, resulting in a concise route to (–)-paspaline A in 9 steps from commercially available materials and the first pathway to and structural confirmation of emindole PB in 13 steps. This work highlights how traditional retrosynthetic design can be augmented with quantum chemical calculations to reveal energetically feasible synthetic disconnections, minimizing time-consuming and expensive empirical evaluation.

scholarly journals Full Characterization of Minimal Linear Codes as Cutting Blocking Sets

2021 ◽  
pp. 1-1
Author(s):  
Chunming Tang ◽  
Yan Qiu ◽  
Qunying Liao ◽  
Zhengchun Zhou
Keyword(s):  
Linear Codes ◽  
Blocking Sets ◽  
Full Characterization

scholarly journals Special Issue: Advances in Computational Electromagnetics

2021 ◽  
Vol 7 (6) ◽  
pp. 89
Author(s):  
Valerio De Santis
Keyword(s):  
Rare Earth ◽  
Magnetic Materials ◽  
Permanent Magnets ◽  
Computational Electromagnetics ◽  
Superconducting Materials ◽  
Special Issue ◽  
Full Characterization ◽  
Recent Advances

Recent advances in computational electromagnetics (CEMs) have made the full characterization of complex magnetic materials possible, such as superconducting materials, composite or nanomaterials, rare-earth free permanent magnets, etc [...]

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