How Do Ring Currents Affect1H NMR Chemical Shifts?

2003 ◽  
Vol 5 (5) ◽  
pp. 605-608 ◽  
Author(s):  
Chaitanya S. Wannere ◽  
Paul von Ragué Schleyer
Keyword(s):  
Chemical Shifts ◽  
Nmr Chemical Shifts ◽  
Ring Currents

Ring currents, NMR chemical shifts, and homoaromaticity: the homotropylium ion revisited

1984 ◽  
Vol 106 (20) ◽  
pp. 5974-5978 ◽  
Author(s):  
Ronald F. Childs ◽  
Michael J. McGlinchey ◽  
Aravamuthan Varadarajan
Keyword(s):  
Chemical Shifts ◽  
Nmr Chemical Shifts ◽  
Ring Currents

Investigation of1H NMR Chemical Shifts of Organic Dye with Hydrogen Bonds and Ring Currents

2011 ◽  
Vol 115 (13) ◽  
pp. 2830-2836 ◽  
Author(s):  
Sung Soo Park ◽  
Yong Sun Won ◽  
Woojin Lee ◽  
Jae Hong Kim
Keyword(s):  
Hydrogen Bonds ◽  
Chemical Shifts ◽  
Organic Dye ◽  
Nmr Chemical Shifts ◽  
Ring Currents

COMPUTATIONAL NICS AND 13C NMR ChARACTERIZATION OF SUBSTITUTION PATTERNS OF C60-nNn FULLERENES (n = 1–12)

2013 ◽  
Vol 12 (03) ◽  
pp. 1350009 ◽  
Author(s):  
MARYAM ANAFCHEH ◽  
REZA GHAFOURI ◽  
FERESHTEH NADERI
Keyword(s):  
Dft Calculations ◽  
13C Nmr ◽  
Chemical Shifts ◽  
Nmr Chemical Shifts ◽  
Ring Currents ◽  
Nmr Characterization ◽  
Dopant Atoms ◽  
Isotropic Chemical Shifts ◽  
Stable Structures

DFT calculations are applied to evaluate the effects of atomic arrangements of dopant atoms on electronic features of the most stable structures of C 60−n N n(n = 1–12) fullerenes. Our study reveals that 13 C isotropic chemical shifts (δiso) of the nuclei at C–N pentagon–hexagon (ph) junctions appear at downfield values while there are no tangible values of δiso for the nuclei at C–N hexagon–hexagon (hh) junctions; the carbon sites attached to the first neighbors of nitrogen at hh junctions (the second neighboring effect) yield upfield values of δiso. Moreover, compensation between diatropic and paratropic ring currents leads to slightly less negative NICS value in C59N heterofullerene (-3.6) compared to the parent fullerene C60 (-4.25). However, with incorporating more nitrogen atoms into the cage the aromaticity first increases, up to the 66π-system C54N6 and C53N7 , yielding the most negative NICS values of -26.3 and -26.8, respectively, and then decreases so that NICS finally reaches the value of -6.6 ppm for C48N12 heterofullerene. On the basis of distinct value predicted for each heterofullerene, one expects that NICS values may also be useful for identification of the molecules through their endohedral 3 He NMR chemical shifts.

scholarly journals Is (benzene)Cr(CO)3 really more aromatic than benzene?

2017 ◽  
Vol 95 (3) ◽  
pp. 263-270 ◽  
Author(s):  
Amnon Stanger
Keyword(s):  
Local Ring ◽  
Excellent Agreement ◽  
Ring Current ◽  
Chemical Shifts ◽  
Experimental Results ◽  
Nmr Chemical Shifts ◽  
Ring Currents ◽  
Global And Local

(benzene)Cr(CO)3 was claimed to be more aromatic than benzene, based on the central 1H Me chemical shifts in dimethyldihydropyrene annulated to it. In this paper, several dihydropyrenes are computationally investigated. NICS-scan methods are used to assess the ring current properties, and NMR calculations are used for obtaining NMR chemical shifts. The parent and four benz-annulated dihydropyrenes show excellent agreement with the experimental results, reported by R. Mitchell in several papers. The effect of annulating the antiaromatic cyclobutadiene was shown to be larger than that of benzene and to change the type of ring currents; while benz-annulated dihydropyrenes maintain local 14-annulene and local benzenic ring currents, the cyclobutadiene-annulated dihydropyrenes show global (and local) ring currents. A NICS-scan study of (benzene)Cr(CO)3 and a NICS-XY-scan study of the (CO)3Cr(C6H4)-annulated to dihydropyrene show that the benzene in the Cr complex is at most aromatic as benzene, probably somewhat less. A detailed study of the 1H chemical shifts suggests that the experimental results were somewhat misinterpreted, and that (benzene)Cr(CO)3 is at most as aromatic as benzene.

Relativistic and Dynamic effects are needed to correctly model the 1H NMR Chemical Shifts of an Iridium Polyhydride Cluster

2020 ◽  
Author(s):  
Abril C. Castro ◽  
David Balcells ◽  
Michal Repisky ◽  
Trygve Helgaker ◽  
Michele Cascella
Keyword(s):  
1H Nmr ◽  
Chemical Shifts ◽  
Dynamic Effects ◽  
Nmr Chemical Shifts

Accurate prediction of 195Pt NMR chemical shifts for a series of Pt(ii) and Pt(iv) antitumor agents by a non-relativistic DFT computational protocol

2014 ◽  
Vol 43 (14) ◽  
pp. 5409-5426 ◽  
Author(s):  
Athanassios C. Tsipis ◽  
Ioannis N. Karapetsas
Keyword(s):  
Dft Calculations ◽  
Anticancer Agents ◽  
Antitumor Agents ◽  
Chemical Shifts ◽  
Accurate Prediction ◽  
Nmr Chemical Shifts ◽  
Relativistic Dft ◽  
Square Planar ◽  
Wide Range ◽  
Computational Protocol

Exhaustive benchmark DFT calculations reveal that the non-relativistic GIAO-PBE0/SARC-ZORA(Pt)∪6-31+G(d)(E) computational protocol predicts accurate 195Pt NMR chemical shifts for a wide range of square planar Pt(ii) and octahedral Pt(iv) anticancer agents.

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