Cobalt cluster-functionalisation of polyynes : from simple to elaborate dendritic architectures

This work introduces a wide variety of polyyne rich compounds capable of accommodating a dicobalt hexacarbonyl cluster on each alkyne functionality. The aim of the project has been to synthesize and cahracterize these polyynes and the related cluster-rich compounds, from the smallest monoclusters to the heaviest tridecacluster obtained.
After the synthesis and the full characterization of the smallest polyynes, the related cluster-rich compounds were obtained. Furthermore some alkyne building blocks have been combined to obtain species with extended backbones with increasing numbers of polyyne functionalities, and again they have been reacted to form the cluster rich compounds. Finally, some alkyne building blocks have been extended to form dendritic units with an increasing number of alkyne functionalities up to thirteen, on which thirteen clusters have been inserted.
Chapter 1 reports a brief introduction to set the compounds studied in this work in a wider context, giving an overview of synthetic approaches an potential applications of polyynes.
Chapter 2 reports a general discussion about the methodologies adopted for the polyyne synthesis using the well known Sonogashira reaction, and the insertion of dicobalt hexacarbonyl clusters into the polyyne backbones.
Chapter 3 describes the initial approach to the aromatic polyynes shown below. The reaction of the TMS-protected compounds with dicobald octacarbonyl resulted in the cluster-rich compounds shown below. Combination of some aromatic polyynes produced the following higher molecular mass compounds. After the reaction with dicobalt octacarbonyl, the corresponding cobalt derivates were obtained.
Chapter 4 reports the combination of some aromatic polyynes, to produce the following ethynyl-centred compounds. The corresponding cluster-rich compounds could then be obtained.
Chapter 5 discusses the synthesis of asymmetric substituted compounds. After the insertion of dicobalt hexacarbonyl clusters into these compounds, the related cobalt-rich compounds were synthesized.
Chapter 6 reports a variety of phenyl and biphenyl-functionalised compounds, which were used to obtain the following end capped polyynes. After the insertion of dicobalt hexacarbonyl clusters the corresponding compounds were studied.
In chapter 7 substituted benzene cores have been used to produce, by a convergent synthesis, the following benzene-centred dendritic compounds. From the 1,4-disubstituted benzene core it has been possible to insert up to six cobalt clusters and the structures are the following. From the 1,3,5-trisubstituted benzene core it was possible to insert into the backbone up to nine cobalt clusters as shown below. From the 1,2,4,5-tetrasubstituted benzene core it was possible to isolate the following nonacluster and dodecaclusters.
Chapter 8 describes the synthesis fo the ethynyl-centred dendritic compounds by a divergent methodology. In the final step, cobalt-rich compounds with up to thirteen clusters were obtained.
Chapter 9 reports some functionalised butadiyne compounds. Those compounds have been extremely useful in terms of proving the efficiency of the reaction of vicinal polyynes with dicobald octacarbonyl. The insertion has been complete and the following compounds were characterised.
Chapter 10 reports a complete study of the observed spectroscopic data of polyyne compounds. Several trends have been observed in 1H and 13C-NMR spectroscopic data and the overall use of mass spectrometric and IR spectroscopic data in the characterization of polyynes has been assessed.
Chapter 11 reports a complete study of the observed spectroscopic and spectrometric data of the cobalt hexacarbonyl-decorated derivatives of polyyne compounds.
Chapter 12 reports the conclusions from this thesis.