Synthesis and solid state structure of oxacalix[4]arenes bearing four nitro groups and four tert-butyl groups at their extra-annular positions

Four oxacalix[4]arene derivatives, in which 1,3-dinitrobenzene units and 1,3-di-tert-butylbenzene units are incorporated in alternating order, were synthesized by aromatic nucleophilic substitution. The introduction of the tert-butyl groups increased the stability of the macrocycles against nucleophilic C-O bond cleavage. X-ray crystal structure analyses reveal that the oxacalixarenes adopt an unsymmetrical 1,3-alternate conformation. The bulky substituents did not disturb the conjugation between the bridging oxygen atoms and the dinitrobenzene rings.     

Highly Elastic and Deformable Hydrogel Formed from Tetra‐arm Polymers

After decades of efforts by many researchers, we have succeeded in realizing a near‐ideal polymer network. This network, the Tetra network, is made by cross‐end‐coupling of tetra‐arm polymer modules. The mechanical energy dissipation was extremely low (tan δ ≈ 10⁻⁴). The macroscopic stress–strain relationship of the Tetra network was in good agreement with that of microscopic elastic blobs. The maximum breaking strength was extremely high (≥27 MPa). These results indicate that the Tetra network is closer to an ideal polymer network than any other conventional model networks. Because the Tetra network can be treated as uniformly packed elastic blobs, it should help apply the knowledge of single polymer chains seamlessly to the design of polymer materials and help further develop the theory of rubber elasticity.

     

Doubly N‐Confused Calix[6]phyrin Bis‐Organopalladium Complexes: Photostable Triplet Sensitizers for Singlet Oxygen Generation

Triplet photosensitizers that generate singlet oxygen efficiently are attractive for applications such as photodynamic therapy (PDT). Extending the absorption band to a near‐infrared (NIR) region (700 nm≈) with reasonable photostability is one of the major demands in the rational design of such sensitizers. We herein prepared a series of mono‐ and bis‐palladium complexes ( 1‐Pd‐H₂ , 2‐Pd‐H₂ , 1‐Pd‐Pd , and 2‐Pd‐Pd ) based on modified calix[6]phyrins as photosensitizers for singlet oxygen generation. These palladium complexes showed intense absorption profiles in the visible‐to‐NIR region (500–750 nm) depending on the number of central metals. Upon photoirradiation in the presence of 1,5‐dihydroxynaphthalene (DHN) as a substrate for reactive oxygen species, the bis‐palladium complexes generated singlet oxygen with high efficiency and excellent photostability. Singlet oxygen generation was confirmed from the characteristic spectral feature of the spin trapped complex in the EPR spectrum and the intact ¹O₂ emission at 1270 nm.     

An STM for molecules and wide-bandgap crystal

We are all influenced by Nicolai Delone’s research. Through much of his career, his influence reached Canada through his published papers. However, Professor Delone visited the National Research Council of Canada’s laboratories at least three times from about 1989 to 1995. At that time he was primarily interested in stabilization. Stabilization refers to the fact that, as the intensity of laser light illuminating an atom is increased, the ionization rate passes through a maximum, then falls. Surprisingly the atom becomes stable against ionization at very high intensities.     

Reaction of pyrex type borosilicate glass with water in autoclave

Pyrex glass tubes have been autoclaved for varied times with distilled water in the temperature range from 200 to 260°C. The glass tubes take up quite a large amount of water above 220°C, although the appearance of the glass surface is essentially unchanged. The amount of B₂O₃ extracted from the glass continues to increase linearly with time, while the rates of the Na₂O and SiO₂ extractions approach zero when the aqueous solutions are saturated with the extracted SiO₂. Infrared spectra measured on the autoclaved thin films of pyrex glass show the existence of both molecular water and hydroxyl groups.     

Titanium and zirconium complexes of preorganized tripodal triaryloxide ligands

Tri(2-oxy-3,5-di-tert-butylphenyl)methane, [O3]3- has been used to prepare titanium and zirconium complexes of the general formula [O3]MX (M = Ti, X = NEt2, Cl, CH2Ph; M = Zr, X = CH2Ph). The tripodal [O3] ligand in titanium complexes adopt the syn- and the anti-conformation, while the syn complex of zirconium undergoes facile C-H activation to give a 5-carbametalatrane [O3C]Zr(THF)3.