Conjugated organometallic polymers containing Vollhardt's cyclobutadiene complex: aggregation and morphologies

Advances in Fabrication Materials of Honeycomb Structure Films by the Breath-Figure Method

Creatures in nature possess almost perfect structures and properties, and exhibit harmonization and unification between structure and function. Biomimetics, mimicking nature for engineering solutions, provides a model for the development of functional surfaces with special properties. Recently, honeycomb structure materials have attracted wide attention for both fundamental research and practical applications and have become an increasingly hot research topic. Though progress in the field of breath-figure formation has been reviewed, the advance in the fabrication materials of bio-inspired honeycomb structure films has not been discussed. Here we review the recent progress of honeycomb structure fabrication materials which were prepared by the breath-figure method. The application of breath figures for the generation of all kinds of honeycomb is discussed.

Metal‐Containing Polymers

The article provides an overview of the synthesis, properties, and applications of metal‐containing polymers. The past decade has shown an exponential increase in synthetic methods, resulting in metal‐containing polymers, their characterization techniques, and their potential application into a variety of fields, including chemistry, medicine, biotechnology, and more.

Highly Regio- and Stereoselective Synthesis of Tetrasubstituted Cyclobutenes via Cyclodimerization of Alkynes Mediated by Zirconium

Zirconium-induced cyclodimerization of a variety of heteroaryl-substituted alkynes is described. This method provides a facile synthesis of tetrasubstituted cyclobutenes with high regio- and diastereoselectivity. A ligand-induced reductive elimination mechanism accounting for this novel cyclodimerization is suggested.

Templated Ceramic Microstructures by Using the Breath-Figure Method

We describe the synthesis of two cyclobutadiene(cyclopentadienyl)cobalt-containing poly(p-phenylene ethynylene)s (PPEs) and their use as precursors for stable ceramic surface coatings. Organometallic PPEs were shaped into hexagonally ordered assemblies by using the breath-figure method. Such breath figures can be washed away with an appropriate solvent. Upon pyrolysis at 500 degrees C under either nitrogen or air, the bubble arrays persist as ceramics and are insoluble in organic solvents or water. The formed pyrolyzed bubble arrays were analyzed by optical and scanning electron microscopy, as well as energy dispersive X-ray microanalysis (EDX). The composition of the ceramic materials is discussed based on EDX and IR data.

Highly Metallized Polymers: Synthesis, Characterization, and Lithographic Patterning of Polyferrocenylsilanes with Pendant Cobalt, Molybdenum, and Nickel Cluster Substituents

High molecular weight, soluble, air- and moisture-stable, highly metallized (>25 wt% metal) polyferrocenylsilanes (PFS) [Fe(eta-C5H4)2Si(Me){Co2(CO)6C2Ph}]n (Co-PFS), [Fe(eta-C5H4)2Si(Me){Mo2-Cp2(CO)4C2Ph}]n (Mo-PFS), and [Fe(eta-C5H4)2Si(Me){Ni2Cp2C2Ph}]n (Ni-PFS) containing pendant cobalt, molybdenum, and nickel clusters, respectively, have been prepared via macromolecular clusterization of an acetylide-substituted PFS [Fe(eta-C5H4)2Si(Me)C(triple bond)CPh]n with [Co(2)(CO)8], [{MoCp(CO)(2)}2], or [{NiCp(CO)}2]. The extent of clusterization achieved was in the range of 70-75%. All three highly metallized polymers were demonstrated to function as negative-tone resists in electron-beam lithography, while Co-PFS and Mo-PFS were successfully patterned by UV-photolithography, allowing the fabrication of micron-sized bars, dots, and lines. These studies suggest that the highly metallized polymers may be useful in the fabrication of patterned arrays of alloy nanoparticles for both materials science and catalytic applications.

Pyridine-Capped, Oligomeric (o-Phenyleneethynylene)s

The synthesis, optical properties, and solid-state structures of a series of o-(aryleneethynylene) oligomers containing three to seven aryl units is described. The main chain in all examples is composed of between one and five 4,5-dimethoxybenzene rings which are capped on each end by 2-pyridyl rings. These oligomers demonstrate pH-dependent emission and absorption spectra. Single crystals were obtained from the aryleneethynylenes containing three to five arene rings. These single crystals were investigated by X-ray diffraction.

Photolytic Living Anionic Ring-Opening Polymerization (ROP) of Silicon-Bridged [1]Ferrocenophanes via an Iron-Cyclopentadienyl Bond Cleavage Mechanism

A new living anionic ring-opening polymerization (ROP) method for sila[1]ferrocenophane 1 was developed using UV irradiation in the presence of Na[C5H5] as a promoter to afford controlled molecular weight polymers (Mn = 9.3 x 103 to 7.0 x 104, PDI = 1.04-1.21). A ring-opened ferrocenylsilane with a dangling silyl-substituted cyclopentadienyl anion, which was obtained from a near-stoichiometric photoreaction of 1 with Li[C5H4Me], indicates an Fe-Cp bond cleavage mechanism for the photolytic ROP.

Transition metal-catalyzed formation of boron-nitrogen bonds: catalytic dehydrocoupling of amine-borane adducts to form aminoboranes and borazines

A mild, catalytic dehydrocoupling route to aminoboranes and borazine derivatives from either primary or secondary amine-borane adducts has been developed using late transition metal complexes as precatalysts. The adduct Me(2)NH.BH(3) thermally eliminates hydrogen at 130 degrees C in the condensed phase to afford [Me(2)N-BH(2)](2) (1). Evidence for an intermolecular process, rather than an intramolecular reaction to form Me(2)N=BH(2) as an intermediate, was forthcoming from "hot tube" experiments where no appreciable dehydrocoupling of gaseous Me(2)NH.BH(3) was detected in the range 150-450 degrees C. The dehydrocoupling of Me(2)NH.BH(3) was found to be catalyzed by 0.5 mol % [Rh(1,5-cod)(mu-Cl)](2) in solution at 25 degrees C to give 1 quantitatively after ca. 8 h. The rate of dehydrocoupling was significantly enhanced if the temperature was raised or if the catalyst loading was increased. The catalytic activity of various other transition metal complexes (Ir, Ru, Pd) for the dehydrocoupling of Me(2)NH.BH(3) was also demonstrated. This new catalytic method was extended to other secondary adducts RR'NH.BH(3) which afforded the dimeric species [(1,4-C(4)H(8))N-BH(2)](2) (2) and [PhCH(2)(Me)N-BH(2)](2) (3) or the monomeric aminoborane (i)Pr(2)N=BH(2) (4) under mild conditions. A new synthetic approach to the linear compounds R(2)NH-BH(2)-NR(2)-BH(3) (5: R = Me; 6: R = 1,4-C(4)H(8)) was developed and subsequent catalytic dehydrocoupling of these species yielded the cyclics 1 and 2. The species 5 and 6 are postulated to be intermediates in the formation of 1 and 2 directly from the catalytic dehydrocoupling of the adducts R(2)NH.BH(3). The catalytic dehydrocoupling of NH(3).BH(3), MeNH(2).BH(3), and PhNH(2).BH(3) at 45 degrees C to give the borazine derivatives [RN-BH](3) (10: R = H; 11: R = Me; 12: R = Ph) was demonstrated. TEM analysis of the contents of the reaction solution for the [Rh(1,5-cod)(mu-Cl)](2) catalyzed dehydrocoupling of Me(2)NH.BH(3) together with Hg poisoning experiments suggested a heterogeneous catalytic process involving Rh(0) colloids.

Metal‐Containing Polymers

The focus of this article is on the synthesis, properties, and applications of metal‐containing polymers. These polymers may be classified based on the types of metal–ligand bonding, and whether the metal is an integral part of the polymer backbone or pendent to the polymer backbone. The first class of polymers discussed are those with metals σ‐bonded to organic spacers in their backbones. Examples of metal–metal single and multiple bonds are also described. Metallocenes and coordination polymers are two classes of polymers where the metal is π‐coordinated to the organic ligands. The coordination of metals to porphyrins, phthalocyanines, Schiff base ligands, as well as to many other types of ligands are described. Another major class of polymers are those where the metal is pendent to the polymer backbone. These polymers include materials with metallic moieties π‐coordinated to unsaturated ligands in their backbones. Polymers with metallic moieties in their side chains are also described. A brief overview of star polymers and dendrimers is also included.

Supramolecular chirogenesis in zinc porphyrins: equilibria, binding properties, and thermodynamics

Complexation mechanism, binding properties and thermodynamic parameters of supramolecular chirality induction in the achiral host molecule, syn (face-to-face conformation) ethane-bridged bis(zinc porphyrin), upon interaction with chiral monoamine and monoalcohol guests have been studied by means of the UV-vis, CD, (1)H NMR, and ESI MS techniques. It was found that the chirogenesis process includes three major equilibria steps: the first guest ligation to a zinc porphyrin subunit of the host (K(1)), syn to anti conformational switching (K(S)), and further ligation by a second guest molecule to the remaining ligand-free zinc porphyrin subunit (K(2)), thus forming the final bis-ligated species possessing supramolecular chirality. The validity of this equilibria model is confirmed by the excellent match between the calculated and experimentally observed spectral parameters of the bis-ligated species. The second ligation proceeds in a cooperative manner as K(2) > K(1) for all supramolecular systems studied, regardless of the structure of the chiral ligand used. The binding properties are highly dependent on the nature of the functional group (amines are stronger binders than alcohols) and on the structure of the chiral guests (primary and aliphatic amines have overall binding constant values greater than those of secondary and aromatic amines, respectively).

Poly(p-phenyleneethynylene)s by alkyne metathesis

Alkyne metathesis was effected by mixtures of Mo(CO)(6) and phenols at elevated temperatures based on an improved version of the method reported by Mortreux and Mori. When propynylated arenes are subjected to these reaction conditions, the formation of diarylalkynes is often quantitative and likewise allows the synthesis of alkyne-bridged macrocycles and polymers of high molecular weight. Alkyne metathesis made high-molecular weight poly[p-(dialkylphenylene)ethynylene]s (PPEs) accessible that show promise as active layers in organic semiconductor devices.