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Abstract(s)
This dissertation presents and discusses the preparation of molecular wires (MW)
candidates that would then be probed for electron transfer properties. These wires are bridged by 1,4-diethynylbenzene derivatives with alkoxy side chains with palladium and ruthenium metal complex termini. Characterization of these compounds was performed by usual spectroscopic
techniques like 1H, 13C{1H} and 31P{1H} NMR, MS, FTIR and UV-Vis as well as by cyclic
voltammetry which allowed classifying the candidates in the Robin–Day system and
determination of bridges side chain and length effects on electronic transport.
Preparation of the 1,4-diethynylbenzene derivatives was done with synthetic pathways
that relied heavily in palladium catalyzed cross-couplings (Sonogashira). A family of single ringed 1,4-diethynylbenzene ligands with different length alkoxy side chains (OCH3, OC2H5, OC7H15) was thus prepared allowing for the influence of these ring decorations to be assessed.
The ruthenium binuclear rods showed communication between metal centres only when
the shorter ligands were used whereas the longer Ru complexes showed only one redox pair in CV studies which is in agreement to non-communicating metal centres.
Cyclic voltammetry studies show irreversible one wave processes for palladium dinuclear complexes, making these rods function as molecular insulators.
Fluorescence decay studies performed on the prepared compounds (ligands and complexes) show a pattern of decreasing decay times upon coordination to the metal centres
which can due to ligand charge redistribution upon coordination leading to non-radiative relaxation paths.
Regarding the X-ray structures, two new ligand related structures were obtained as well as new structure for a palladium rod.
The effect of the side chains was observed to be important to the wires’ electronic
properties when comparing with the analogues without a side chain. The effect brought by longer chains is nevertheless almost negligible.
Description
Keywords
Molecular wires X-ray diffraction Sonogashira cross-coupling Palladium Ruthenium Química . Centro de Ciências Exatas e da Engenharia