C3-symmetric, dendritic structured, chiral chromophores: synthesis and linear and nonlinear optical properties

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The synthesis of new multifunctional molecular materials is one of the current challenges in synthetic chemistry. This proposal just meets the challenge. On the one side C3 symmetric, dipolar, dendritic structured chromophores with coordinated dia- and paramagnetic metal atoms will be synthesized and their first hyperpolarizability beta will be determined. On the other side these compounds should be chiral in order to study the circulardichroism depending on the second harmonic generation (SHG-CD) and magnetization induced frequency doubling (MSHG) as well as magnetochiral dichroism. Additionally, as another magnetically induced effect, the Faraday rotation of these complexes will be investigated. The metal atoms fix a helical chiral arrangement of the NLO chromophores through chelating coordination and the paramagnetism is believed to enhance the magnetic effects. For the chelating coordination the dipolar single strand NLO chromophore is decorated with 2,2'-bipyridine (bipy) and 2-phenylpyridine (ppy). The substitution of the chelating ligands with electron donating and electron accepting functions in 5 and 5'-position is of particular importance to warrant the communication between the donor and acceptor, and to warrant the dipolar character. The first hyperpolarizability beta will be determined by hyper-Rayleigh scattering with our own set-up, which was provided from the DFG for another project. The HRS set-up is equipped with a Nd:YAG laser and an OPO, which allows to tune the stimulating wavelength (1064 - 1500 nm). Measurements concerning the SHG-CD and the magnetically induced effects will be performed in close collaboration with Verbiest's group at the University of Leuven (Belgium).