Switching in molecular shapes: main chain length driven rod–circle transition of isolated helical polysilanes

Synthesis, characterisation and electronic properties of naphthalene bridged disilanes

Synthesis of naphthalene bridged disilanes 2_R (R = Me, Ph) was performed via catalytic dehydrocoupling. Using RhCl(PPh₃)₃ as a catalyst, an intramolecular Si-Si bond was readily formed from the corresponding disilyl precursors 1_R (R = Me, Ph). For catalytic reactions using (C₆F₅)₃B(OH₂), bridged siloxanes (3_Ph and 3_Me) were observed. Attempts to install the 1,8-naphthalene bridge directly onto a disilane resulted in an unusual product (4), containing two silicon centres bridged through one naphthyl group, and another naphthyl group attached to a single Si centre. In order for this product to form, both a Si to Si hydrogen shift rearrangement as well as Si-Si bond cleavage occurred. The effects of phenyl and methyl substitutions on the structure and electronic properties of the synthesised compounds was investigated by single crystal X-ray diffraction, as well as IR and multinuclear NMR spectroscopic analysis. In addition, theoretical UV-Vis absorption maxima were evaluated using density functional theory (TD-SCF) on a B3LYP/6-31(++)G** level of theory and compared with experimental UV-Vis spectroscopic data.

Metallocene influence on poly(cyclosilane) structure and properties

Poly(cyclosilane)s, conjugated polymers inspired by crystalline silicon, are synthesized by group 4 metallocene-promoted dehydrocoupling polymerization.

Polymers and the p-block elements

A survey of the state-of-the-art in the development of synthetic methods to incorporate p-block elements into polymers is given. The incorporation of main group elements (groups 13-16) into long chains provides access to materials with fascinating chemical and physical properties imparted by the presence of inorganic groups. Perhaps the greatest impedance to the widespread academic and commercial use of p-block element-containing macromolecules is the synthetic challenge associated with linking inorganic elements into long chains. In recent years, creative methodologies have been developed to incorporate heteroatoms into polymeric structures, with perhaps the greatest advances occurring with hybrid organic-inorganic polymers composed of boron, silicon, phosphorus and sulfur. With these developments, materials are currently being realized that possess exciting chemical, photophysical and thermal properties that are not possible for conventional organic polymers. This review focuses on highlighting the most significant recent advances whilst giving an appropriate background for the general reader. Of particular focus will be advances made over the last two decades, with emphasis on the novel synthetic methodologies employed.

Time-dependence structures of coordination network wires in solution

We present a mechanochemistry-based procedure to isolate individual chains on surfaces of a ruthenium MMX polymer. After sonication of solutions containing the two building blocks of the mentioned MMX polymer, time-depending structures are formed in the solution. The architecture of the different structures obtained in this process, as a function of the time, is monitored using atomic force microscopy. The resulting structures exhibit uniform subnanometer diameters over microns length, in agreement with the expected diameter for an individual polymer chain. From the atomic force microscope images, we infer a long persistence length for the linear structures. Finally, the effect of the temperature solution in the formation of the different structures is also addressed.

Polysilanes on surfaces

For chain-like polymers on surfaces, the relationship between chain topology and inherent physical properties has long been puzzling due to the lack of proper models and detection systems with ultrahigh sensitivity and high accuracy. Among various chain-like polymers, soluble organopolysilane is one suitable model for elucidating the uniqueness of chain-like polymers on surfaces because of its (1) controllable molecular length, polydispersity, stiffness, and terminal group by an adequate molecular design, a careful synthesis, and a precise purification, and (2) highly luminescent chromophore due to Siσ-Siσ* transition of the Si main chain. This review comprehensively covers the works on (i) molecular imaging with scanning probe microscopy, (ii) tethering on surfaces by a grafting-to approach, (iii) self-assembly, (iv) structural phase transition, (v) orientational phase transition, and (vi) chiroptical switching, memory and amplification in single and double layer films deposited on solid surfaces. This knowledge and understanding may stimulate advanced studies on polymer-based nanoscience, nanotechnology, and nanofabrication as well as in traditional surface chemistry and polymer physics.

MMX polymer chains on surfaces

Fibres of [Ru(2)Br(micro-O(2)CEt)4]n polymer have been isolated on different surfaces under specific conditions, and morphologically characterised by AFM and STM, showing an unexpected helical internal structure.