Structure-property relationship in organometallic compounds regarding SHG

Structure-property relationships based on experimental as well as theoretical results will be elucidated. For this purpose different dipolar organometallic compounds were synthesized and characterized. The alteration of the donor and acceptor termini in mono- and dinuclear sesquifulvalene complexes results in spectroscopic and even structural modifications. The structural and ¹H NMR spectroscopic changes correlate with the experimentally obtained first hyperpolarizability. The potent electron-donating (D) group [(CpFeCO)₂(μ-CO)(μ-C=CH-)] is combined with different electron-accepting units (A), yielding the push-pull complexes [(CpFeCO) ₂(μ-CO)(μ-C=CH-CH=A)]. The extent of electron derealization within the π-bridge connecting the donor D and the acceptor A can be monitored by means of ¹H NMR spectroscopy. A correlation between the ³J(H_β-H_γ) coupling constants and the first hyperpolarizability is found, which very much resembles the dependence of the first hyperpolarizability on the bond length alternation. In order to elucidate the dependence of the NLO response on the conformation of triply branched NLOphores, a new series of dendritic D-π-A structures has been synthesized. A combined approach of experiments and computational predictions was applied both on the dendrimers and on the corresponding single-strand chromophores. These results demonstrate that theoretical calculations are able to reproduce experimental results and show the tendency of the effects due to structural changes.