1. crowmether-host1.ppt
Chiral Recognition by NMR Spectroscopy- A Theoretical approach.
Illustrating modeling strategies with organic molecules
with overtones for Modeling of Bio-molecules
An Abstract
S.Aravamudhan
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4/28/2019 2:24:40 AM
wmbs-II-mzu Dr.Aravamudhan

2. wmbs-II-mzu Dr.Aravamudhan
The Chiral recognition by NMR require:
NMR spectrum of the Host molecule
NMR spectrum of the Guest (Chiral) molecule
NMR spectrum of the Host-guest complex.
Identifying the spectral lines/region which indicates the dependence on the complexing by the guest.
And, monitoring the indicator peaks with the concentration of the Guest molecule This means a theoretical calculation would require calculation of the NMR of the complex molecule for various Stoichio metric proportions and hence Host to Guest molar ratios - 1:2, -1:1, - 2:1, -etc ., to be specifying a few typical ratios. To cover non-integral ratio values, the required integral number of cluster molecules would demand handling large sized molecular cluster than for the above simple integral ratios. For such clusters Host-host, guest-guest interactions and changes in structures of host and guest molecule structures would be factors to reckon with.
This would mean the super molecular system to handle would increase in size depending on the complex as compared to the size of the guest molecule alone or the host molecule alone. The increase in computation time, and while trying to optimize the time factor, what options could be exercised on the theoretical method and basis sets, must be spelt out with the corresponding advantages/disadvantages.
4/28/2019 2:24:40 AM
wmbs-II-mzu Dr.Aravamudhan

3. wmbs-II-mzu Dr.Aravamudhan

4. wmbs-II-mzu Dr.Aravamudhan
Added to these structures would be the Guest Chiral molecules for the recognition of chriality by the distinguishing features
4/28/2019 2:24:40 AM
wmbs-II-mzu Dr.Aravamudhan

5. wmbs-II-mzu Dr.Aravamudhan

6. wmbs-II-mzu Dr.Aravamudhan
The Calculations of NMR spectra after optimizing the molecular ratios 1:2, 2:1 etc., requires more computational time than what is practically possible with the DEMO version of the
(from slide #1) This would mean the super molecular system to handle would increase in size depending on the complex as compared to the size of the guest molecule alone or the host molecule alone. The increase in computation time, and while trying to optimize the time factor, what options could be exercised on the theoretical method and basis sets, must be spelt out with the corresponding advantages/disadvantages.
And, hence in this case this has typically led to the situation of looking for better computation power , and these efforts with this DEMO version has been able to provide significant insight as to what is to look for fist of all at the small molecule level even when an access to better computational facility is gained.
It is these kind of physically realistic criteria to be acquired as essential pre-requisit, which is being enunciated highlighted by those who point out the disadvantages of what they term as “Brute Force Computation”
Return to Slide #2
4/28/2019 2:24:40 AM
wmbs-II-mzu Dr.Aravamudhan