Ultra-high Performance Thermochromic Polymers via a Solid-solid Phase Transition Mechanism and Their Applications.

Thermochromic materials are substances that change color in response to temperature variations. Today, sustainability concerns are the main drivers of thermochromic research, with smart, energy-efficient windows being one of the primary applications. While vanadium oxides and leuco dyes are traditionally the main thermochromic materials, hydrogels operating based on change of solvation have risen as some of the most promising materials due to their high optical transparency and good solar modulating abilities.

Thioxanthylium Cations: Highly Reversible Hydrochromic Mate-rials with Tunable Color and Moisture Sensitivity.

Hydrochromic materials, which change color in response to moisture, are highly sought-after due to some unique applications such as moisture detection, humidity monitoring, anti-counterfeiting, and sweat-pore mapping. We herein report a new thioxanthene-9-ols/thioxanthylium cations hydrochromic system. The hydrochromic thioxanthylium cations can be generated/regenerated by exposing a chemically stable thioxanthene-9-ol to trifluoroacetic acid (TFA).

Synthesis and Halochromic Properties of 1,2,6-Tri- and 1,2,3,6-Tetra-aryl Azulenes.

A series of novel 2,6-functionalized azulene molecules Azu1-3 with varied fluorene substituents at the 1- and 3-positions of azulene as well as at the 5'-position of 2-thiophene group were synthesized. Their electronic absorption and emission spectra at neutral and protonated states were examined. It was found that after functionalization with fluorenyl groups, Azu1-3 exhibited absorption maxima at 445, 451 to 468 nm, respectively.

Synthesis of Conjugated Polymers via Transition Metal Catalysed C-H Bond Activation.

Transition metal catalysed C-H bond activation chemistry has emerged as an exciting and promising approach in organic synthesis. This allows us to synthesize a wider range of functional molecules and conjugated polymers in a more convenient and more atom economical way. The formation of C-C bonds in the construction of pi-conjugated systems, particularly for conjugated polymers, has benefited much from the advances in C-H bond activation chemistry.

Carboxylic Acid Directed C-H Arylation of Azulene.

The first example of directed C-H activation for azulene is reported. A variety of 2-arylazulenes are obtainable exclusively from 1-azulene carboxylic acids, with yields of up to 82%. Some heteroaryl groups such as pyridine and thiophene are also tolerated in the reaction.

Modulating the Properties of Azulene-containing Polymers Through Functionalization at the 2-Position of Azulene.

Poly(2-arylazulene-alt-fluorene) and poly(2-arylazulene-alt-thiophene) are synthesized via Suzuki and Stille cross-coupling polymerization, respectively, using 1,3-dibromo-2-arylazulenes as monomers, which are prepared by a novel directed C-H activation method of 2-carboxylic azulene and subsequent bromination reaction. Our study shows that functionalization at the 2-position of azulene monomers influences polymer properties. For instance, different from electron-withdrawing groups that discourage the protonation of azulene, electron-donating aryl groups, however, enhances the sensitivity of response to acid.

Azulene in Polymers and Their Properties.

Azulene, a unique isomer of naphthalene, has received much interest from researchers in different fields due to its unusual chemical structure with a negatively charged 5-membered ring fused with a positively charged 7-membered ring. In particular, incorporation of azulene into polymers has led to many interesting properties. This minireview covers functionalization methods of azulene at its various positions of 5- and 7-membered rings to form azulene derivatives including azulene monomers, and gives an overview of a wide range of azulene-containing polymers including poly(1,3-azulene), azulene-based copolymers with connectivity at 1,3-positions of the 5-membered ring, or 4,7-positions of the 7-membered ring, as well as copolymers with azulene units as side chains.

Diastereoselective C-H carbonylative annulation of aliphatic amines: a rapid route to functionalized γ-lactams.

A palladium(ii)-catalysed C(sp)-H carbonylation of free(NH) secondary aliphatic amines to 2-pyrrolidinones is described. A correlation between the nature of the carboxylate ligand and the diastereoselectivity and yield of the process was observed. As such, under these optimal conditions a range of aliphatic amines were converted to the corresponding trans-4,5-disubstituted 2-pyrrolidines with good d.

Inverse-Electron-Demand Diels-Alder Reactions: Principles and Applications.

Inverse-electron-demand Diels-Alder (iEDDA) reactions are an intriguing class of cycloaddition reactions that have attracted increasing attention for their application in bioorthogonal chemistry, the total synthesis of natural products, and materials science. In many cases, the application of the iEDDA reaction has been demonstrated as an innovative approach to achieve target structures. The theoretical aspects of this class of reactions are of particular interest for scientists as a means to understand the various factors, such as steric strain and electron density of the attached groups, that govern the reaction and thus to elucidate the reaction mechanism.

Cyclization of Tetraaryl-Substituted Benzoquinones and Hydroquinones through the Scholl Reaction.

2,3,5,6-Tetrakis(5'-dodecylthiophen-2-yl)-benzoquinones and 2,3,5,6-tetrakis(5'-dodecylthiophen-2'-yl)-hydroquinones were prepared via the Stille or Suzuki cross-coupling reactions, followed by oxidation by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in the case that aryl groups are dodecylthiophenyl. 2,3,5,6-Tetrakis(5'-dodecylthiophen-2'-yl)benzoquinone and 2,3,5,6-tetrakis(5'-dodecylthiophen-2'-yl)-1,4-bis(dodecyloxy)benzene underwent the Scholl reaction to give their corresponding predictable cyclization products anthra[2,1-b:3,4-b':6,5-b″:7,8-b‴]tetrathiophene-7,14-dione (3) and anthra[1,2-b:4,3-b':5,6-b″:8,7-b‴]tetrathiophene (5), respectively. Cyclization of 2,3,4,5-tetra(p-tert-butyl-phenyl) benzoquinones through the Scholl reaction, however, gave rise to a mixture of two cyclization products including an unusual major product, benzo[4',5']furo[3',2':3,4]triphenyleno[1,2-b]benzofuran (9), with 84% yield and a minor product, 2,3-diphenyltriphenylene-1,4-diol (10), with 11% yield.