University of Otago, New Zealand

Chemistry

Te Tari Hua-Ruanuku

Matthew Reish

contact photo
Matthew Reish
Supervisor: Prof. Keith C. Gordon
Tel: (03) 479 7930
Location: Science II, 5c1
mreish@chemistry.otago.ac.nz


Non-linear optics has become an important part of the photonics field; however the full realization of the potential in for organic NLO chromophores has not been reached. The goal of this project is to discover ways to optimize non-linear optical response of chromophore compounds for use in low polarity media. Some challenges associated with optimizing NLO response are the effects of electron redistribution based on the polarity of the surrounding media and aggregation of the chromophores of in low polarity media. The following is an example of an NLO compound we use a test case for optimization.

Figure 1: Optimized Structure of Pyr3pi

Figure 1 shows the optimized structure of pyr3pi with monomer on the left and dimer on the right. To check the accuracy of the these structures we compare the calculated raman spectra with experimental spectra.

To address these problems in our test compounds we are modelling the chromophores using solvent approximation and use we spectroscopy to probe the electronic changes and vibrational characteristics of these molecules. We use UV-Vis, NMR and Raman spectroscopy to interpret the reliability of calculation as well as interpreting the electronic effects of the solvent on the ground and excited structures of the chromophores.

Figure 2: Calculated and Experimental Raman Spectra

Figure 2 is a comparison of the calculated (B3LYP 6-31G*) spectra of the dimer (top) and monomer (middle) to the experimental spectra of Pyr3pi. This comparison is used to gage the accuracy of the calculation.

References:

  1. A.J. Kay, A.D. Woohouse, Y. Zhao, K. Clay (2004) Synthesis and linear/nonlinear optical properties of a new class of RHS NLO chromophore. J. Mat. Chem. 14:1321-1330
    - First reported synthesis of NLO chromophores we are working with
  2. C.M. McGoverin, T.J. Walsh, K.C. Gordon, A.J. Kay, A.D. Woolhouse Predicting nonlinear optical properties in push–pull molecules based on methyl pyridinium donor and 3-cyano-5,5-dimethyl-2(5H)-furanylidene-propanedinitrile acceptor units using vibrational spectroscopy and density functional theory. Chem. Phys. Lett. 443: 298-303
    - Example publication from previous research students