Use this URL to cite or link to this record in EThOS:
Title: The design and synthesis of organic materials with large nonlinear optical effects
Author: Whittaker, S. D.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2003
Availability of Full Text:
Access from EThOS:
Calculations have been carried out on the structures of donor-acceptor azobenzenes, phenylazothiophenes, benzylideneanilines and extended conjugated systems (incorporation benzene and thiophene connected by azo and amino bridges) using the AM1 and PM3 molecular orbital methods. The results show that AM1 method gives the best results overall when compared to the X-ray data, but the PM3 method tends to give better results for sulfur contain systems. The dipole moments, transition energies and molecular hyperpolarisabilities, of the donor-acceptor structure listed above, have been calculated by the CNDOSVB method from the optimised AM1 calculations. Analysis of the calculated results for the azo dyes shows a slight increase in hyperpolarisability when increasing the number of electron acceptors on the chromophore, but a substantial increase when benzene is replace by thiophene. The benzylideneanilines show similar effects as the azo dye, when the number of electron acceptor groups are increased, but the substitution of the thiophene ring into the benzylideneaniline system produces differing effects on the magnitude of the hyperpolarisability depending on whether it replaces the benzene ring attached to the electron donor or the benzene ring attached to the electron attracting groups within the chromophore. Attempts have been made to synthesise the molecules with the largest hyperpolarisabilities. These include azo dyes, 4-N,N-bis(2-hydroxyethyl)amino-2',4'-dinitroazobenzene and (3',5'-dinitrothiopheneazo)-4-[N,N-bis(2-hydroxyethyl)aniline] which were synthesised in 60 and 40% yields by coupling either 2,4-dinitroanilne or 2-amino-3,5-dinitrothiophene with N-phenyldiethanolamine respectively. Benzylideneanilines were also synthesised, including some promising examples such as N,N-diethyl-N-(p-nitrobenzylidene)-p-phenylenediamine and N,N-diethyl-N-[(5-nitrothien-2-yl) methylene]-p-phenylenediamine which were synthesised in 60-70% yields by either condensing p-nitrobenzaldehyde or 5-nitrothiophene-2-carboxaldehyde with N,N-diethyl-phenylenediamine respectively. More complex systems were also synthesised, including 4-{[4- (N,N-bis(2-hydroxyethyl)amino)phenyl]diazenyl}-N-[(4-nitrophenyl)methylene]aniline which was synthesised in a 45% yield by condensing the azo dye 4-N,N-bis(2-hydroxyethyl)amino-4'-aminoazobenzene with p-nitrobenzaldehyde.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available