Calculations of the Contribution of Ring Currents to the Chemical Shielding Anisotropy

2002 ◽  
Vol 124 (9) ◽  
pp. 1832-1833 ◽  
Author(s):  
Jonathan Boyd ◽  
Nikolai R. Skrynnikov
Keyword(s):  
Chemical Shielding ◽  
Ring Currents

scholarly journals [2.2.2.2]Paracyclophanetetraenes (PCTs): cyclic structural analogues of poly(p‑phenylene vinylene)s (PPVs)

2021 ◽  
Vol 1 ◽  
pp. 111
Author(s):  
Matthias Pletzer ◽  
Felix Plasser ◽  
Martina Rimmele ◽  
Martin Heeney ◽  
Florian Glöcklhofer
Keyword(s):  
Conjugated Polymers ◽  
Electronic States ◽  
Phenylene Vinylene ◽  
Photoluminescence Intensity ◽  
Redox Potentials ◽  
Cyclic Structure ◽  
Chemical Shielding ◽  
Ring Currents ◽  
Conjugated Macrocycles ◽  
Structural Analogues

Background: Poly(p-phenylene vinylene)s (PPVs) and [2.2.2.2]paracyclophanetetraene (PCT) are both composed of alternating π-conjugated para-phenylene and vinylene units. However, while the former constitute a class of π-conjugated polymers that has been used in organic electronics for decades, the latter is a macrocycle that only recently revealed its potential for applications such as organic battery electrodes. The cyclic structure endows PCT with unusual properties, and further tuning of these may be required for specific applications. Methods: In this article, we adopt an approach often used for tuning the properties of PPVs, the introduction of alkoxy (or alkylthio) substituents at the phenylene units, for tuning the optoelectronic properties of PCT. The resulting methoxy- and methylthio-substituted PCTs, obtained by Wittig cyclisation reactions, are studied by UV-vis absorption, photoluminescence, and cyclic voltammetry measurements, and investigated computationally using the visualisation of chemical shielding tensors (VIST) method. Results: The measurements show that substitution leads to slight changes in terms of absorption/emission energies and redox potentials while having a pronounced effect on the photoluminescence intensity. The computations show the effect of the substituents on the ring currents and chemical shielding and on the associated local and global (anti)aromaticity of the macrocycles, highlighting the interplay of local and global aromaticity in various electronic states. Conclusions: The study offers interesting insights into the tuneability of the properties of this versatile class of π-conjugated macrocycles.

An Experimental and Theoretical Investigation of the Chemical Shielding Tensors of13Cαof Alanine, Valine, and Leucine Residues in Solid Peptides and in Proteins in Solution

2001 ◽  
Vol 123 (42) ◽  
pp. 10362-10369 ◽  
Author(s):  
Robert H. Havlin ◽  
David D. Laws ◽  
Hans-Marcus L. Bitter ◽  
Lori K. Sanders ◽  
Haihong Sun ◽  
...  
Keyword(s):  
Theoretical Investigation ◽  
Chemical Shielding ◽  
Shielding Tensors

scholarly journals On the generation of electronic ring currents under vibronic coupling effects

2020 ◽  
Vol 153 (22) ◽  
pp. 224308
Author(s):  
Krishna Reddy Nandipati ◽  
Oriol Vendrell
Keyword(s):  
Vibronic Coupling ◽  
Coupling Effects ◽  
Ring Currents

Phosphorus-31 chemical shieldings in a fused cis-1,2,3-benzothiadiphosphole: a dipolar NMR study

1992 ◽  
Vol 70 (4) ◽  
pp. 1229-1235 ◽  
Author(s):  
Gang Wu ◽  
Roderick E. Wasylishen ◽  
William P. Power ◽  
Graziano Baccolini
Keyword(s):  
Line Shape ◽  
Magic Angle Spinning ◽  
Pair Approximation ◽  
Magic Angle ◽  
Single Bond ◽  
Chemical Shielding ◽  
Spin Pair ◽  
Nmr Study ◽  
Shielding Tensors ◽  
Angle Spinning

Phosphorus-31 NMR static powder spectra and high-resolution magic angle spinning spectra have been obtained for a new heterocyclic compound, cis-2,10-dimethyl[1,2,3]benzothiadiphospholo[2,3b][1,2,3]benzothiadiphosphole (1), which contains a P(III)—P(III) single bond. The homonuclear 31P–31P dipolar interaction manifests itself in both the magic angle spinning spectra and the non-spinning line shape. Under the AX spin pair approximation, analysis of the spinning sidebands in the MAS experiment yields a full characterization of the two 31P chemical shielding tensors. This approximation is confirmed by the exact powder line shape simulation for a homonuclear spin pair. Analysis of the dipolar subspectra also yields the absolute sign of 1J(P,P), which is found to be negative. Keywords: phosphorus–phosphorus single bond, chemical shielding tensors, dipolar NMR, MAS, static line shape.

Coherent Ring Currents in Chiral Aromatic Molecules Induced by Linearly Polarized UV Laser Pulses

2013 ◽  
Vol 543 ◽  
pp. 381-384 ◽  
Author(s):  
Manabu Kanno ◽  
Hirohiko Koho ◽  
Hirobumi Mineo ◽  
Sheng Hsien Lin ◽  
Yuichi Fujimura
Keyword(s):  
Aromatic Ring ◽  
Quantum Dynamics ◽  
Ring Current ◽  
Molecular System ◽  
Laser Pulses ◽  
Uv Laser ◽  
Aromatic Molecules ◽  
Ring Currents ◽  
Linearly Polarized ◽  
Coherent Ring

In recent years, laser control of electrons in molecular system and condensed matter has attracted considerable attention with rapid progress in laser science and technology [. In particular, control of π-electron rotation in photo-induced chiral aromatic molecules has potential utility to the next-generation ultrafast switching devices. In this paper, we present a fundamental principle of generation of ultrafast coherent ring currents and the control in photo-induced aromatic molecules. This is based on quantum dynamics simulations of π-electron rotations and preparation of unidirectional angular momentum by ultrashort UV laser pulses properly designed. For this purpose, we adopt 2,5-dichloro [(3,6) pyrazinophane (DCPH) fixed on a surface, which is a real chiral aromatic molecule with plane chirality. Here π electrons can be rotated along the aromatic ring clockwise or counterclockwise by irradiation of a linearly polarized laser pulse with the properly designed photon polarization direction and the coherent ring current with the definite direction along the aromatic ring is prepared. This is contrast to ordinary ring current in an achiral aromatic ring molecule with degenerate electronic excited state, which is prepared by a circularly polarized laser [2]. In this case, π electrons rotate along the Z-axis of the laboratory coordinates, while for the present case electrons rotate along the z-axis in molecular Cartesian coordinates. It should be noted that signals originated from the coherent ring currents prepared by linearly polarized ultrashort UV lasers are specific to the chiral molecule of interest.

Ring Currents in Large [4n + 2]-Annulenes

ChemInform ◽  
2004 ◽  
Vol 35 (16) ◽  
Author(s):  
Alessandro Soncini ◽  
Patrick W. Fowler ◽  
Leonardus W. Jenneskens
Keyword(s):  
Ring Currents
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