Quantum Chemical Modeling Of Some Organic Molecules With Non-Linear Optical Properties: Metal Sandwiched Cyclophanes

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Date
2015-05-25
Authors
Mohamed ,Mohamed Zaki Nagmeldin
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Publisher
University of Khartoum
Abstract
In this work we studied the non-linear optical properties of the Paracyclophane molecules with molecular modeling. We used the semiemprical quantum chemical methods to calculate the dipole moment and polarizability using MOPAC package of programmes. The modeling was based on selecting the two substituents methoxy group (MeO) as a donor and the cyano group (CN) as an acceptor group. These substituents were permuted among eight positions on the two rings. The metals Berlium, Magnesium and Zinc were selected for complexing these ring system to afford metal sandwiched compounds. In the model the metals were placed at the centre of the cage molecule. The two benzene rings in the cyclophanes are bridged by alkane (Single bond) and an alkyne’s(Triple Bond). Two patterns of substitution have been adopted; the dipolar and the octupolar. The later based on group theory is meant to eliminate the possibility of centrosymmetric crystal. The molecules were geometry optimized and the dipole moment and polarizability were calculated. The highest value obtained for the hyperpolarizability was 569006 atomic units with Magnesium ion and octupolar system with triple bond bridge. The effect of substituents varies on dipolar systems and depends on the number of substituents and their push-pull arrangement. High values however were obtained with octupolar systems with few substituents attached
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129 Pages
Keywords
Dielectric Coefficient;Beryllium;Magnesium;crystal;hyperpolarizability
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