Subject: Summary of NMR chemical shift calculatons

From: [email-masked] (Mori Seiji)
Date: Fri, 8 Dec 1995 14:06:07 +0900

Dear netters,

 Thank you for several replies about my questions for the method of NMR
chemical shift, and so on. 
I think the reliability of IGAIM , CSGT in G94 packages were not known very
much thus we have to check
these methods comparing with known methods. The systematic review of
solvent effects, 
polarity and coordination with donating solvent such as ether have still be
awaited.
As for the concept of anitrosopy and isotropy, thank you for sending me
many replies.
I show  two original questions and corresponding replies.

  Thank you very much for your help.
  Sincerely yours,
  Seiji Mori

---my original question 1 ---

  Dear everybody,

Recently, many letters about NMR chemical shift calculation were posted,
and I am also 
interested in NMR shifts in organic and organometallic complexes in
solution. I have several questions,

1. How is the reliablities of 
   1.1  methods (GIAO, IGAIM, CSGT, IGLO)
   1.2  theory (HF,DFT,MP2...CC) and basis-sets
   1.3  How is the solvent effect of polarity on the NMR shift, coupling
constant
(I think it is not related calcluation , probably it is a fundamental
question about NMR)?
2. Do you know the program or references which one can calculate not only
chemical shift but also 
the coupling constant 
( for example, 1H-1H and 13C-13C) and NOE in quantum chemistry other than
G94? As to 1H-1H 
coupling constant, 
many programs such as PCMODEL was supported but its calculation  is not QC. 

 If you have comments and indicate the references, would you please send me
? I will summarize
replies.

 Thanks in advance,
 Seiji Mori
-------------
Replies
---1---
Received: by zinc.chem.ucalgary.ca (AIX 3.2/UCB 5.64/4.03)
          id AA10813; Fri, 24 Nov 1995 15:29:30 -0700
From: [email-masked]

Hi Seiji,

you have quite a lot of questions in your posting ... I shall try to give
you a few hints, with no intention to be comprehensive.

> 
> 1. How is the reliablities of 
>    1.1  methods (GIAO, IGAIM, CSGT, IGLO)
>    1.2  theory (HF,DFT,MP2...CC) and basis-sets
>    1.3  How is the solvent effect of polarity on the NMR shift, coupling
> constant
> (I think it is not related calcluation , probably it is a fundamental
> question about NMR)?

Good references to start with are three nice reviews, one new, two are older:

D.B.Chesnut:
Annual Reports on NMR Spectroscopy,   published by Academic Press,
Vol.21,1989, p. 51    and ibid, Vol. 29, 1994, p.71.

H.Fukui:
Magn. Res. Rev. 1987, vol. 11, 205

Further, very comprehensive reviews are contained in an annual series, since
1980 written every year by C.Jameson: in Specialist Periodical Report on
Nuclear Magnetic Resonance, Vol.8,1980-... (edited by G.A.Webb, and 
published by the Royal Society of Chemistry, Cambridge)

Now more specific comments on your various questions.

1.1 
Methods with distributed gauge origins (IGLO, LORG, GIAO,...) are 
generally preferable (for a given basis set) over 
methods with a common gauge origin. For examples, see the various reviews.
GIAO seems to converge slightly faster with the size of the basis set
then IGLO (see Wolinski, Hinton, Pulay, JACS 1990, 112, 8251). This
would also make sense from a theoretical point of view.
   I don't know off hand about IGAIM, CSGT.

1.2 Correlation.
there are cases where correlation is necessary, e.g., M.Buehl et al.
J.Phys.Chem.
99, 4000 (1995), and M.Buehl et al. Chem.Phys.Lett. 241 (1995), 248.
These papers contain examples where MP2 fails completely to predict the 
shift while DFT and CCSD are able to achieve quantitative results.
   There are however many other cases where the HF level works just fine
(all the
respective literature up to -- say -- five years ago).

Basis sets.
See about any paper with calculated shifts. E.g., the one by Pulay et al.
mentioned above, or various papers by the Kutzelnigg group, or the various
reviews.

1.3 Solvation effects can be considerable, indeed. Look for experiments
that were
done in the gas phase (in addition to solution studies). A review of gas phase 
NMR was written by C. Jameson:
Chem.Rev.1991, 91, 1375.

> 2. Do you know the program or references which one can calculate not only
> chemical shift but also 
> the coupling constant 
> ( for example, 1H-1H and 13C-13C) and NOE in quantum chemistry other than
> G94? As to 1H-1H 
> coupling constant, 
> many programs such as PCMODEL was supported but its calculation  is not QC. 

Coupling constants are MUCH tougher to calculate than chemical shifts.
The reason is (in my opinion) that you are dealing with operators that 
evaluate the electron density in essentially just one point of space rather
than over an entire region of space.
     Annual reviews of calculations are contained in the same series of books
that was metioned before:
Specialist Periodical Report on Nuclear Magnetic Resonance

Calculations have been done recently, e.g., by Erikson/Malkin/Salahub et al. but
I don't have the references on hand right now.

I am looking forward to your summary!

Yours, Georg

---2---
From: "Steve Gwaltney" <[email-masked]>
Date: Mon, 27 Nov 1995 10:51:20 -0500

> 2. Do you know the program or references which one can calculate not only
> chemical shift but also 
> the coupling constant 
> ( for example, 1H-1H and 13C-13C) and NOE in quantum chemistry other than
> G94? As to 1H-1H 

ACES II can calculate chemical shifts using GIAO's and MBPT(2)
wavefunctions.  ACES II can also calculate CCSD coupling constants.
For information about ACES II contact [email-masked].  I believe
TURBOMOLE can also calculate chemical shifts, but you should check
with them to make sure.

Steve

---3---
From: [email-masked] (Wagener Thomas)
Subject: CCL:NMR shift and coupling constant calculation
Date: Mon, 27 Nov 1995 14:12:47 +0100 (CET)

Dear Seiji Mori,

since I have finished my thesis on the ab-initio calculation a few month
ago, I hopefully can help you with some of your questions.
 
> 1. How is the reliablities of 
>    1.1  methods (GIAO, IGAIM, CSGT, IGLO)
>    1.2  theory (HF,DFT,MP2...CC) and basis-sets
>    1.3  How is the solvent effect of polarity on the NMR shift, coupling
> constant

I had only the opportunity to work with GIAO and IGLO so I can only make a 
statement on these methods.
Basically IGLO and GIAO are quite reliable for the calculation of "standard"
organic compounds though the accuracy of the methods is not as high as the
experimental accuracy. A rough estimate would be an accuracy of about 5ppm
for 13C chemical shifts - probably better. Taking into account that you are
comparing gas phase values at absolute zero with values taken from a sample
in solution at a temperature of, say, 200-300K that is probably as close as
you can get.
The computational effort for the IGLO method is somewhat higher than for the
GIAO calculation (at HF-level) though the information you get from IGLO is 
more extensive. Because IGLO works with localized molecular orbitals (LMOs) 
you get an anlysis of the contribution of the LMOs to the chemical shift 
while you only get the shielding constant out of the GIAO calculation.

IGLO is available at HF level and there is a DFT version using the IGLO
code to calculate chemical shifts. The GIAO method in MO theory is available
up to CC level though the computational effort is extremely high so the
calculation of the shielding constant at such a highly coorelated level is
only possible for small molecules. The GAUSSIAN94 manual states that the GIAO 
module of the program can cope with DFT but I have no experience with that.

> 2. Do you know the program or references which one can calculate not only
> chemical shift but also 
> the coupling constant 
> ( for example, 1H-1H and 13C-13C) and NOE in quantum chemistry other than
> G94? As to 1H-1H coupling constant, 

As far as I know (and I really may not be up to date) the only programs
capable of calculating coupling constants is DeMon with DFT-IGLO and ACESII
(at MP2 level). 

Some useful references are:
- IGLO: Kutzelnigg, W.; Fleischer, U.; Schindler, M.:"The IGLO-Method: Ab-
initio Calculation and Interpretation of NMR chemical Shifts and magnetic
Susceptibilities", NMR Basic Princ. Prog., Vol. 23, Springer-Verlag, Berlin
Heidelberg, 1990, 165
- DFT-IGLO: Malkin, M. G.; Malkina, O. L.; Casida, M. E.; Salahub, D. R.,
JACS, 116(1994), 5898
- HF-GIAO: Wolinski, K.; Hilton, J. F.; Pulay, P., JACS, 112(1990), 8251
- MP2-GIAO: Gauss, J., Chem. Phys. Lett., 191(1992), 614

Hope, this was of some help
                        Thomas Wagener

---my original questions 2 about isotropies...---
  Dear Sirs,

 I posted to CCL about the methods of NMR calculation a fey days ago , and
had an other question.
In G94, I tried to calculate the chemical shifts , there are magnetic
shieldings 
in the output, however, no chemical shift but isotropic  and anitrosopy. 
I examine meaning of these terms in the user's manual of Gaussian 94 and 
several original papers,for example,
M. Schindler, et al. JCP, 1982, 76, 1919
and Pulay et al. JACS, 1990, 112, 8251, and so on which there is replies 
of my previous questions
, but I only know that isotropic terms is "likely" to be 
corresponding to the chemical shifts which was experimentally observed. 
I had had experiments in organic chemistry, and I am now carrying out the 
ab initio calculations but I amn't much familiar to know the theory 
of NMR spectroscopy. 
Would you please tell me the physical meaning of isotropic  and anitrosopy, 
and which is an equivalent of the experimental chemical shift? It is better
that 
you show the references. 

    Sincerely yours,
    Seiji Mori
---- replies----
---1---
Date: Tue, 28 Nov 1995 11:10:24 +0100 (MEZ)
From: Alexander Christian Backes <[email-masked]>

Konichiwa Mori-san,

the chemical shift is always a tensor (a symmetric 3 x 3 matrix). So, this
tensor describes the interchange between several NMR-active nuclei.  The
outerdiagonal elements are only important in spectra of the solid phase
because there the position of the molecules and therefore the observed nuclei
are defined and the shift is therefor anisotropic (CSA = Chemnical shift
anisotropy). In solution the motion of the molecules is randomized, so the
NMR-spectrometer observes the middled shift. This means, the trace of the
matrix is relevant (the trace is the sum of the diagonal elemnts of the
matrix, divided by three, in case of the 3 x 3 matrix). So, in G94 the
calculated isotropic shift is the relevant one for solution. 

Of course you need a standard for the chemical shift; G94 doesn't know to
which reference substance the shifts are related to. So you have to calculate
TMS at exactly the same level as the calculated molecule, and then you have
to subtract the isotropic data of your molecule from the isotropic data of
TMS. (This you have to do each time you use another method and basis set for
geometry optimization and NMR-calculations).  But be careful - the input
geometry of TMS must have Td-symmetry. And therefore you have to precalculate
TMS at MP2-level to make sure it gets Td-Symmetry. This geometry you can use
as standard input for any of the following calculations of geometry and
NMR-parameters. 

References to the first point you can find in any book dealing with 
the theory of NMR-spectroscopy.
The second point has references first our own experience and second 
papers which will be published soon.

Greetings from Germany,
Alexander.
---2---
From: [email-masked]
Date: Tue, 28 Nov 1995 13:41:54 +0100 (MET)
Hi Seiji,

your are probably interested in the isotropic shielding. To convert
from shielding to chemical shift (in delta scale) you have to 
calculate the shielding of a reference compound, say for example
TMS for 1H-, 13C- or Si NMR and substract the calculated shielding
values of your compound. In principle it is also possible to use
smaller references like CH4. In this case you have to take care
of the delta-value of this compound (eg. -2.3 ppm for 13C in CH4).
Just make sure that you use identical basissets for the calculations.

The anisotropic values can sometimes be measured in CPMAS (solid state
nmr). They give the shielding along the princible axis of your system.
For spherical homogeneous compounds like CH4 you will notice that the
anisotropic shieldings are the same as the isotropic. Since solution
nmr gives an average of all possible orientations you alway get the
isotropic shieldings. Only in cases where the molecule can be 
oriented (no rotation) like in the solid state, it is possible to
measure the three anisotropic values independently. 

John
---3---
Date: 28 Nov 1995 14:31:34 +0000
From: "E.A.Moore (Elaine Moore)" <[email-masked]>

G94 and all other ab initio programs used for calculating chemical shifts calula
te chemical shielding. Experiment measures the chemical shift which is the chemi
cal shielding relative to that of a reference molecule such as TMS (tetramethyls
ilane). The relative isotropic shielding is the quantity normally observed, for
example in liquid samples. The anisotropy can be obtained from solid state measu
rements and can be important in relaxation. Chemical shielding is a tensor quant
ity and G94 gives you all 9 components in the frame you have chosen. The isotrop
ic shielding is (sigma xx + sigma yy + sigma zz)/3. The anisotropy is sigma 33 -
 (sigma 11 + sigma 22)/2 where 1,2,3 refer to the principal axis frame  and sigm
a 33> sigma 22 >sigma 11. The chemical shift is sigma (reference)- sigma (compou
nd) where sigma is the isotropic shielding.  Hope this is some help
Elaine A. Moore Chemistry Dept. The Open University UK

 ---4---
From: [email-masked] (Elmer Valderrama)
Date: Tue, 28 Nov 1995 09:28:48 +0000 (GMT)

  Hi,

  Anisotropy only shows up in ordered media (crystalls, liquid-crystals).
  Organic compounds may be in solid state. As such, -e.g. not disolved in
  any solvent-, they may be "measured" in a RMN experiment. If, to this end,
  a direction of the crystal have been chosen, it may happen that the shift
  measured in the perpendicular to this chosen direction shows different. Then
  you'll have a diference which is called anisotropy. Moreover, -and for this
  it's better to read the reference below-, since the chem. shift actually is a
  tensor you'd have to compute three components (the diagonal) relative to
  the chosen direction in the crystal.

  In isotropic media (a mix of crystalls, no direction can be especified,
  or in liquid/solved sample) the shift is just the common measured quantity
  which physically is equal to one third of the trace of the above mencioned
  tensor.
 
  ..my two cents, hope it helps.

  Elmer Valderrama
 
  [1]  K. Eichele, et al. "Phosphorus-31 Chemical Shift of Phosphinidene
       Ligands in Ruthenium Carbonyl Cluster Compounds: A 31-P Single
       Crystal and CP/MAS-NMR Study"
       J.Am.Chem.Soc. 1995,117,6961-6969   [and ref there in]
       (This work includes an orbital study using CACAO and a qualitative
        application of Ramsey's theory)

---5---
From: [email-masked]
To: Mori Seiji <[email-masked]>
Date: Tue, 28 Nov 1995 10:51:13 -0400 (EDT)

Seiji:
I ran into this proble recently and have a suggestion:
1) You need the isotropic part of the shielding tensor.
2) Chemical shifts can be calculated from this isotropic part using some
simple theory:  I recommend the information in chapter 2 of :
Multinuclear NMR, J. Mason Ed., Plenum Press, New York, 1987.
You will also need the isotropic shielding for the chemical shift
standard for your nucleus. (In my case it was (EtO)2.BF3 for 11B NMR).

Steve Williams
Chemistry
Appalachian State University
Boone, NC 28608
[email-masked]

---6---
Date: Wed, 29 Nov 1995 12:08:48 +1000
To: [email-masked] (Mori Seiji)
From: [email-masked] (Hugh Capper)
Dear Mori,
 isotropic =  having the same physical arrangement of moieties around the
atom of interest which in this case is the proton  ( if you are doing proton
specroscopy)
 anitrosopy = is the reverse ie having different moities which cause
diffences around the proton of interest.  anitrosopy is reflected in the
chemical shift.
As for a reference a good basic text is Fundamentals of NMR Spectroscopy by
Derome.
best wishes,
Hugh Capper
Institute for Magnetic Resonance Research
University of Sydney
NSW 2006
Australia

---7---
From: [email-masked] (Mark J Forster )
Date: Tue, 28 Nov 1995 10:03:11 -0800
( You can see in CCL archives.)
---
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