7/6/ :50:10 AMAravamudhan: Chiral Recognition by NMR1 Chiral Recognition by NMR Spectroscopy- A Theoretical approach. Illustrating modeling strategies with organic molecules with overtones for Modeling of Bio-molecules An Abstract This material may be availed as Internet Resource: Display the web subdirectory: Some of the linked files in this.ppt file require the Software “ARGUSLAB” be installed in your system. Download the MS Windows installer “setup.exe” file by clicking on the link below: The setup file is in the folder “arguslab” as mentioned in the link above. Download the contents of the folder, create a folder by name “arguslab” in your sytem, and save all the contents of the link folder in your resident disk-folder If this presentation file is saved to the resident disc, and if the slideshow is running while the internet connection is available in the P.C., then all the hyperlinks would display the appropriate files from the internet. S.Aravamudhan crownether-Host-guest-C-docked.ppt

While trying to find out the host-guest interactions the thrust has also been to make use of (1) an as much versatile software for the theoretical calculations (2) and a software which is also easily accessible for beginners that would enable them to learn the features of a software for theoretical (Quantum mechanics/ Molecular mechanics) Calculations. Such a report of the facts of investigation would put the beginners on the path for learning about the compromises required in a (macro-)molecular modeling. Typically the trade off between molecular sizes and available computer memory, together with the necessity to minimize the computational time (which could be a matter of computational costs). The computational chemistry package used for the current work is the online remote computational facility located at The strong point first of all is the simplicity of access and the student-proof way the web administration manages the Working Demo of this computational chemistry website. The second, but no less important is the fact that this working demo has one of the most advanced features for choosing the computational methods by providing several software engines with each one of them capable of being configured for several properties of molecules to be calculated. Computation, and the way the entire Job parameter can be archived in the resident disc for uploading into the Demo for subsequent calculations at any later time, and the way the results and job parameters can be exported to process and review in off-line mode are not features to which beginners can have access as readily as it is in this working Demo. There is no way as per the current version of the Demo to increase the computational time available per job to more than one minute. This provides an experience in choosing model systems for addressing specific theoretical queries even in the small molecule regime. 18 July 20122Aravamudhan Chiral discrimination NMR

18Crown6ether- Flig1-S-F at6 zaxis 18Crown6ether- Flig1-S-F at6 zaxis-UFF-GO 18Crown6ether- Flig1-S-N at6 zaxis 18Crown6ether-Flig1-S- Nat6zaxis-UFF-GO 18Crown6ether- Flig2-R-Fat6zaxis 18Crown6ether- Flig2-R-Nat6zaxis hyperlink View in Str. Editor View in Str. Editor View in Str. Editor View in Str. Editor 18 July 20123Aravamudhan Chiral discrimination NMR All G.O. are MM Calculations

18Crown6ether- Flig2-R-Nat6zaxis-UFF-GO 18Crown6ether- Flig2-R-Fat6zaxis-UFF-GO 18Crown6ether- Flig2-R-Nat6zaxis 18Crown6ether- Flig2-R-Fat6zaxis hyperlink View in Str. Editor View in Str. Editor View in Str. Editor View in Str. Editor 18 July 20124Aravamudhan Chiral discrimination NMR All G.O. are MM Calculations

The typical constraint of a time limit of 1 min. per job rendered the G.O. by QM ab initio methods as most inconvenient to opt. However the corresponding geometry ( obtained by the G.O. using any other time saving means) of these molecules could be conveniently put through the one-minute jobs for NMR chemical shift calculations at the “WEBMO”. All the NMR spectra of the different isomers (of the C s -several lines in spectrum - and of the D 3d – towlines spectrum ) of the 18Crown6Ether were obtained by ab initio SCF/STO 3G choice with G.I.A.O. for the chemical shift calculation.several lines in spectrum towlines spectrum When it becomes the host (18Crown6ether) –guest (ligand) the NMR calculations exceeded the time limit and hence no calculated spectrum could result for comparison with unbound Host spectrum and the free ligand spectrum (even for the simplest chiral molecule one could envisage as derivative of a methane structure). Thus even before knowing the actualities of binding criteria which enable the Chiral Discrimination, it became necessary to resort to a modeling strategy, essentially to decrease the size of the molecule and thus in detail know about the theoretical explanations for the possible discrimination. With this situation at the outset, a search for a model. Two major criteria emerges from the Calculations of the docking type and the corresponding NMR spectra: 1) as much a simple NMR pattern for assigning the protons to track the distinct changes due to chirality of guest. 2) Much of the complexing is determined by the interaction with the oxygen centers of the host and hence the importance of Crown Ether. 18 July 20125Aravamudhan Chiral discrimination NMR