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Presented By: Mohamed E. A. Safy A new insight for Chalcogen - - PowerPoint PPT Presentation
Presented By: Mohamed E. A. Safy A new insight for Chalcogen - - PowerPoint PPT Presentation
A new insight for the role of chalcogen bond in drug discovery & material science based on point-of-charge approach & MEP Presented By: Mohamed E. A. Safy A new insight for Chalcogen interactions AGENDA INTRODUCTION Sigma-hole &
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introduction
Chalcogen Interactions
The chalcogen group is the group VI atoms in the periodic table and contains O, S, Se, T e, and Po atoms. Chalcogen interaction is attributed to the existence of a positive region called sigma-hole on the chalcogen atom. Sigma-hole is a cap of positive charge appears on the halogen, chalcogen and pnicogen atoms due to the anisotropic distribution of electron density .
A new insight for Chalcogen interactions
The position of sigma hole at the extension of the covalent bond is responsible for the highly directionality of Chalcogen bond. The characteristics of chalcogen bond is still under debate. A wide range applications of chalcogen bond in many fields like polymer chemistry and drug discovery.
CS2 molecule
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Aims & Objectives
The aim of study is to reinvestigate chalcogen bond properties. Redefine the sigma-hole concept as a donor for chalcogen bond. investigate the preferred angle for the chalcogen bond. Indicate the distance effect in the chalcogen bond strength. Study the effect of hybridization in chalcogen bond formation.
A new insight for Chalcogen interactions
Explanation the role of chalcogen bond in sulfa drugs according to our results. Studying the stability of polymer containing sulfur based on the formation of chalcogen bond (four polymers are under of study) .
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computational methods
A new insight for Chalcogen interactions
The study was carried on two model (CX2 and H2X, where X=O, S and Se). Molecular electrostatic potential maps were generated for the studied molecules at B3PW91/6-311G** level.
Molecular Optimization Potential energy surface
The stabilization energy of the molecules was calculated in the presence of a point-of-charge with a value of -0.1, -0.25, -0.5 and -1 a.u at MP2/aug-cc-PVTZ level. 2D and 1D Scanning for the Potential Energy Surface at a distance of 2.5 Å on X-axis with the four charges. The effect of angle in the stabilization energy were studied from 90° to 180°. The studied molecules were firstly optimized at MP2/6-311++G** level. Point-of-charge (PoC) approach for studying non-covalent interactions.
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A new insight for Chalcogen interactions
Software & Facilities
All calculations were carried out using Gaussian09 software. All calculations were carried by using our high-performance computer called (CompChem-HPC).
computational methods
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A new insight for Chalcogen interactions
Molecular electrostatic potential
Molecular electrostatic potential illustrate the charge distributions of molecules three dimensionally. These maps allow us to visualize variably charged regions of a molecule. There is no sigma-hole in the two molecules of oxygen. Sulfur and selenium compounds have a significant sigma hole which give their compound the ability to form chalcogen bond.. The size of sigma-hole increases from Oxygen to selenium which enhance the ability of chlalcogens to form chalcogen bond.
Results & Discussion
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A new insight for Chalcogen interactions
Results & Discussion
2D potential surface scan
2D stabilization energy surface at a distance of 2.5 Å on X-axis was generated for the studied six molecules.
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A new insight for Chalcogen interactions
Results & Discussion
2D potential surface scan
2D stabilization energy surface at a distance of 2.5 Å on X-axis and -1.00 au value of PoC for the six studied molecules
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A new insight for Chalcogen interactions
Results & Discussion
Charge effect on MEP
The PoC effect on the charge distribution around the chalcogen was studied. A significant reorientation for the charge was observed. The reorientation of the charge confirm the important role of charge value on the Lewis base in the interaction energy.
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A new insight for Chalcogen interactions
Results & Discussion
Effect of Distance
Scanning along the carbon chalcogen double bond axis with our four values of negative charge from 2.5 to 8 Å. Scanning along the hydrogen chalcogen bond axis with our four values of negative charge from 2.5 to 8 Å.
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A new insight for Chalcogen interactions
Results & Discussion
Effect of Angle
Angle study of the six studied molecules along hydrogen chalcogen bond and carbon chalcogen bond from 90° to 180°.
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A new insight for Chalcogen interactions
Results & Discussion
Real Chalcogen-Complexes
Distance and angle scanning with a fluoride instead of a PoC was studied.
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Conclusion
A new insight for Chalcogen interactions
The ability of chalcogen atoms to form chalcogen bond increase from oxygen to selenium The preferred bond angle for interaction will be along the extension of sigma bond. The chalcogen bond is the sum of van der walls interaction and electrostatic. The distance effect is related to the chalcogen atom size. Stabilization energy increases with increasing Lewis base strength The point-of-charge approach is a reliable method for studying the noncovalent interaction.
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