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<imcvey #*at*# aquarius.kent.edu> |
| Date: |
Mon, 5 Jun 1995 13:31:27 -0400 (EDT) |
| Subject: |
SUMMARY: Redox potentials from HOMO/LUMO |
Hello All,
A long time ago it seems (at least two weeks) I asked a question
about relating HOMO/LUMO energies to the redox potentials of a
heterogeneous set of molecules. I received a lot of summary requests,
and a number of responses giving excelenent advice.
Thank you to all who responded and here is a summary
My original questions was:
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Greetings All,
I am about to try to generate a corelation
between the HOMO and/or LUMO energies and the redox
potentials for a selection of organic molecules,the
selection of molecules I think I want to study are
likely to be quite heterogeneous (i.e. some aromatics,
aliphatics, olefins etc..)
My question is: has this been done before, and
do you think it will be necessary to use CI in order to
produce reasonable values for the HOMO and LUMO energies
All suggestions warmly welcomed
If requested I will of course supply a summary
Iain McVey
Graduate Student
Department of Chemistry
Kent State University
Kent, Ohio 44242
imcvey(-(at)-)phoenix.kent.edu
and here are the responses:
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From root Thu May 18 15:57:24 1995
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Date: Thu, 18 May 1995 15:59:30 -0400 (EDT)
From: SATYAM;at;vms.cis.pitt.edu
Subject: Re: CCL:redox potentials from HOMO/LUMO
To: imcvey { *at * } Phoenix.kent.edu
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Status: RO
Dear Iain,
Many books discuss this aspect..and treat these correlations from
the prespective of different quantum theory level..e.g. book on
photoinduced electron transfer by M. A. Fox..discusses in tables
the correlations of redox potentials with homo / lumo for different
class of molecules..aromatics, polycyclic etc etc.
Some excellent organic chemistry books also give such relations..
most of them from HMO model ..
should you require more information I will be glad to discuss..
plus I remain interested in your results too.
Best wishes,
Satyam
-----------------------------------------------------------
Dr. Satyam Priyadarshy
905 Chevron Science Center (412) 624 1217
Department of Chemistry Fax (412) 624 8552
University of Pittsburgh Email satyam - at - hathi.chem.pitt.edu
Pittsburgh , PA 15260 satyam <-at-> vms.cis.pitt.edu
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From root Thu May 18 21:18:59 1995
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In-Reply-To: imcvey %-% at %-% Phoenix.kent.edu (McVey Iain )
"CCL:redox potentials from HOMO/LUMO" (May 18, 1:57pm)
References: <9505181757.AA82660-0at0-Phoenix.kent.edu>
X-Mailer: Z-Mail (3.0.0 15dec93)
To: imcvey -AatT- Phoenix.kent.edu (McVey Iain )
Subject: Re: CCL:redox potentials from HOMO/LUMO
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Status: RO
Calibrations were done in the parameterisations of MNDO, AM1, and PM3 on IP's
via Koopmans' theorem . C.I. does not back-influence the Homo and Lumo...
in that they are used directli in the C.I. calculation...
Regards,
John
--
John M. McKelvey email: mckelvey (+ at +) Kodak.COM
Computational Science Laboratory phone: (716) 477-3335
2nd Floor, Bldg 83, RL
Eastman Kodak Company
Rochester, NY 14650-2216
--
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From root Fri May 19 02:57:32 1995
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Date: Fri, 19 May 1995 08:57:45 +0200 (MET DST)
From: Gerd Thys
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To: McVey Iain
Subject: Re: CCL:redox potentials from HOMO/LUMO
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Status: RO
Dear Iain,
I think I have some interesting references for you...
H.S. Rzepa, G.A. Suner, J.Chem.Soc.Chem.Commun. (1993), 1743-1744
R.O. Loutfy, I.W.J. Still, M. Thompson, T.S. Leong, Can.J.Chem. 57
(1979), 638-644
S. Sen, N. Celebi, L. Turker, A.M. Onal, Bull.Soc.Chim.Belg. 102 (1993),
583-587
The first one is mainly dealing with calculation of Redox-potentials,
using semi-empirical methods (MNDO, AM1, PM3) and a solvatation model (COSMO)
The second reference is about comparison of measured IP en Eox...
The article by Sen et al compares calculated IP (by means of
Huckel-theory) with measured Eox.
I'm working on this one myself, comparing PM3-calculated IP with measured
oxidation potentials... I don't think using CI is really necessary,
especially if your main goal is to look at a trend in the relation IP-Eox.
I think it's more important to have a good solvatation model if you want
to calculate this relationship.
If you want some more information on how we do it, feel free to contact me.
Best regards,
Gerd
----------------------------------------------------------------------------
Gerd Thys Ph.D. Student
Structural Chemistry Group
University of Antwerp (UIA)
Universiteitsplein 1 E-mail: thys \\at// uia.ua.ac.be
B-2610 Wilrijk URL: http://www.uia.ac.be/u/thys/index.html
BELGIUM
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From root Fri May 19 04:27:31 1995
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From: "Jens Spanget-Larsen"
Organization: Roskilde Universitetscenter
To: imcvey %! at !% Phoenix.kent.edu (McVey Iain)
Date: Fri, 19 May 1995 10:26:48 +0100
Subject: Re: redox potentials via HOMO/LUMO?
Cc: hyperchem -x- at -x- hyper.com
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Status: RO
Dear McVey Iain!
the correlations you attempt to establish have certainly been
investigated for many years. For example, it is well known that
polarographic half-wave reduction potentials for aromatic
hydrocarbons correlate well with Huckel LUMO-energies (Streitwieser,
"Molecular Orbital Theory for Organic Chemists", Wiley, 1961). It
has little sense to include CI in a calculation MO energies. For an
ordinary closed-shell molecule, consideration of interaction with
singly excited configurations does not affect the SCF ground state
(Brillouin's Theorem). If you include doubly or multiply excited
configurations, you introduce electronic correlation effects and the
ground state is stabilized, but the orbital concept "breaks down".
Yours Sincerely, Jens >--<
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
JENS SPANGET-LARSEN
Department of Chemistry Phone: +45 46757711
Roskilde University (RUC) Fax: +45 46757721
POB 260, DK-4000 Roskilde, Denmark Internet: JSL ^at^ mmf.ruc.dk
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
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From: jeg10 ^at^ po.CWRU.Edu (Jennifer E. Grant)
To: imcvey;at;Phoenix.kent.edu
Subject: Re: redox potentials via HOMO/LUMO?
Reply-To: jeg10 %-% at %-% po.CWRU.Edu (Jennifer E. Grant)
Status: RO
Have you tried searching Bigmed
via Entrez? Your idea sounds really terrific and I would
be very interested to see your paper when it gets published.
Jennifer
Grad student
(Enzyme kinetics)
--
"Wer denkt, schafft"
Jennifer E. Grant
Department of Biochemistry
Case Western Reserve University
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Date: Thu May 18 08:31:47 1995
From: curtisj "-at-" usfca.edu
To: imcvey -x- at -x- Phoenix.kent.edu
Subject: Re: redox potentials via HOMO/LUMO?
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Status: RO
Hi Iian,
Sounds like an interesting effort. I haven't really tried this yet, but I've
been
gearing up for it in the context of some transition metal complexes I care
about. In these cases the solvent-solute interaction is very important to the
potentials, so I've been trying to get that figured out first.
My feeling is that for at least some organic series, you will be able to assume
small or constant solvent contribution to the observed potentials. This should
allow you to to at least get at *relative* potentials (you will need at least one
experimental point to reference your calculated potentials to). Keep in mind
that a redox potential is a measurement of the the free energy change between
reactants and products resulting from an electron transfer reaction. Thus to
get at it from quantum mechanical (and hence heat of formation) data, you are
assuming a constant entropic term throughout your series.
You may be able to get some decent correlations from simple HOMO/LUMO
data, but I suspect that a more rigorous route will be to calculate heats of
formation for both the oxidized and reduced forms of your couples and looking
at the difference. I would expect this quatity to be most directly related to
the
redox potential (or at least that's my plan of attack at the moment for the calcs
I haven't started yet!). This will mean doing calcs using the UHF option so
that the program can geometry optimize the structure of the half of the couple
with an unpaired electron properly. You would then do a single point calcula
tion within the RHF approximation at the optimized geometry in order to get the
best value for the heat of formation of the paramagnetic species.
If you're not familiar with all this UHF/RHF stuff, the Hyperchem manuals touch
on it and any decent textbook on quantum theory will explain it in detail.
Good luck! As you can see, I'm interested in this topic and I would very much
appreciate hearing about how it goes for you. If you end up with any interest-
ing correlations and/or results you wouldn't mind sharing, I'd love to see them.
Best wishes,
-- Jeff Curtis at Univ. of San Francisco
USF Chem Dept.
2130 Fulton St.
SF, CA 94117 v)415-666-6391
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To: hyperchem : at : hyper.com
Subject: redox potentials from MO work
Status: RO
Part of my own interest in computation of redox potentials using
Hyperchem is in determination of antioxidant activity. For a class of
similar antioxidants, I tend to get good correlation between
antioxidant activity and heat of reaction for one-electron oxidantion
of antioxidant, but the correlation breaks down when comparing
different classes of antioxidant.
I consider this to be a limitation of a gas-phase model, where the
change in 'molecular environment' for similar antioxidants should be
about the same and thus cancel, but for widely different antioxidants,
the effect of solution stabilization, polarization, etc., is different
and produces a different effect.
I have attempted to correlate excitation energies with antioxidant
activity to no avail.
I would imagine that the environment to which the electron is being
transferred might affect the redox potential, since redox is always
measured experimentally in reference to a particular 'electrode' and
ionization is measured computationally with the electron going off
into 'nothingness'.
matt harbowy
who can't speak authoritatively on redox to save his soul,
nor is elucidating the views of thomas j. lipton, inc.
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Date: Tue, 23 May 1995 16:58:27 +0100 (MET)
From: "Hr Dr. S. Shapiro"
Sender: toukie -AatT- zui.unizh.ch
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To: imcvey ( ( at ) ) Phoenix.kent.edu
Subject: Redox values from HOMO/LUMO
Status: RO
Dear Mr. McVey;
Re your recent CCL posting, please be advised that Martin et al. calcu-
lated electrode potentials for naphthoquinones using extented Hueckel theory;
see Martin, Y. C., Bustard, T. M., & Lin, K. K., J. Med. Chem. 16: 1089
(1973).
Regards,
S. Shapiro
ZH
toukie %-% at %-% zui.unizh.ch
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Date: Thu, 25 May 1995 15:40:11 -0500 (EST)
From: MARYJO \\at// neu.edu
Subject: Re: CCL:redox potentials from HOMO/LUMO
To: imcvey "-at-" Phoenix.kent.edu
Message-Id: <01HQXB367VWY8ZG2ZF %! at !% neu.edu>
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Status: RO
Hello Iain. As a matter of fact, we just wrote a
paper that involves this. There are references
in our preprint of a few who have done just this
previously.
Previously, Kita has correlated electrochemical
oxidation potentials of a series of tetra-arly
oops, let me try again:
tetra-aryl lithium borate salts. The ox pots
correlate well with the HOMO energies calculated
by MNDO.
Our paper does a series of anions, correlating the
electrochemical ox pot with the IP of the HOMO, using
DFT (very ab initio, in my opinion) and a Transition
Operator method. Correlation is pretty good (corr
coeff = 0.91)
This work is done jointly with a company, and it is
not yet submitted, although I expect that it will
be submitted very soon, perhaps within days.
The title of our paper is "The Intrinsic Anodic
Stability of Several Anions Comprising Solvent-
Free Ionic Liquids"
[STUFF DELETED TO PROTECT THE INNOCENT, IM]
I believe that he plans to submit to the Electrochem
Soc journal
I hope that this helps,
Mary Jo Ondrechen
Professor of Chemistry
Northeastern University
Boston, MA 02115 USA
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That's all folks. THanks again to those of you who replied, I hope to have
results ready for the ACS in Chicago so if you are interested in seeing the
results contact me around the end of August and I'll send you what I've
gotten by then
Iain.
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