FROM ACETYLENES TO METAL ACETYLIDE COMPLEXES: CARBON-RICH STRUCTURES FOR MOLECULAR ELECTRONICS

Abstract

Electronics technology is moving so fast that an alternative for the “top-down” approach (lithography on silicon wafer) has to be found. Moore described in the now famous relationship the exponential growth of the number of transistors on a single chip that has become known as “Moore’s Law”, but this rate of progress has nearly reached its physical limits. As a chemist, the molecular scale is the smallest scale that can be manipulated in order to design more specific components. For this reason, the “bottom-up” approach is under rigorous investigation in chemistry and physics. Moreover, organometallic chemistry is increasingly employed for the synthesis of molecules for molecular electronics due to the versatile optoelectronic and structural properties offered by this class of compound (see section 1.5.).
In this thesis, syntheses starting from simple but important carbon-rich organic building blocks to afford complex organometallic molecules are developed. The focus is on carbon-rich molecules such as oligoynes and oligo(phenyleneethynylene) derivatives due their high conjugation giving them good conduction properties.
The preparation of oligoynes with trimethylsilylethynyl and pyridyl linkers and their preliminary single molecule conductivity data are presented in Chapter 2. In this work, a new, simple synthesis of the 1,10-bis(trimethylsilyl)penta-1,3,5,7,9-yne from cross-coupling reactions of 1,6-bis(triphenylphosphinegold)hexa-1,3,5-triyne with 1-iodo-2-trimethylsilylacetylene is developed, which was extended for the synthesis of oligoynes bearing pyridyl termini.

“On complex” synthesis on Ru(II) butadiynyl molecules containing different aryl groups from electrodonating groups (-C6H4OMe-4; N,N-bis(4-methoxyphenyl)4-phenylamine), electroneutral (C6H4Me-4), anchoring groups (2,3-dihydrobenzo[b]thiophene (DHBT); C5H4N) to electrowithdrawing groups (C6H4CN-4) is discussed in Chapter 3. Moreover, elaboration and (spectro)electrochemistry of bimetallic complexes with oligoynes and arylyne bridges are reported and supported by DFT calculations.

Oligo(phenyleneethynylene) metal complexes with various anchoring groups (pyridyl, thioanisole) and a different metal core (Pt and Ru) is explored in Chapter 4, in order to study the influence of the metal together with the linkers on the conductance. Single molecule conductance measurements and (spectro)electrochemistry together with DFT calculations are described.

Finally, an investigation around the coordinating ligand, 2,2’:6’,2”-terpyridine (tpy), and opening new properties such as storage behaviour due to its specific geometry is discussed in Chapter 5. In this last chapter, the preparation of Ru(II) and Fe(II) tpy along with the electrochemical data are reported.