Synthesis and crystal structure ofN,N′-DicyclohexylpiperazineN,N′-dioxide octahydrate

N,N-DicyclohexylpiperazineN,N-dioxide octahydrate, C₁₆H₄₆N₂O₁₀,M _r=426.55, monoclinic, space groupC2/m (No. 12),a=12.961(4),b=11.533(4),c=7.907(1) Å, =98.37(2)^o,V=1169.3(6) ų,Z=2. The structure was solved by the direct method and refined toR=0.045 for 1192 observed MoK reflections. TheN,N-dioxide molecule occupies a site of symmetry 2/m. The piperazine ring takes the chair form with the two N–O bonds oriented axially in atrans configuration. Hydrogen bonding between the water molecules, as well as between theN-oxide groups and water molecules, gives rise to a puckered layer composed of edge-sharing four-membered, five-membered, six-membered, and eight-membered rings. Adjacent layers are cross-linked by theN,N-dicyclohexylpiperazine moieties lying between them, thereby generating a sandwich structure consolidated by covalent and hydrogen bonding. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82062 (8 pages).     

Structural and process controls of AIEgens for NIR-II theranostics

Aggregation-induced emission (AIE) is a cutting-edge fluorescence technology, giving highly-efficient solid-state photoluminescence. Particularly, AIE luminogens (AIEgens) with emission in the range of second near-infrared window (NIR-II, 1000–1700 nm) have displayed salient advantages for biomedical imaging and therapy. However, the molecular design strategy and underlying mechanism for regulating the balance between fluorescence (radiative pathway) and photothermal effect (non-radiative pathway) in these narrow bandgap materials remain obscure. In this review, we outline the latest achievements in the molecular guidelines and photophysical process control for developing highly efficient NIR-II emitters or photothermal agents with aggregation-induced emission (AIE) attributes. We provide insights to optimize fluorescence efficiency by regulating multi-hierarchical structures from single molecules (flexibilization) to molecular aggregates (rigidification). We also discuss the crucial role of intramolecular motions in molecular aggregates for balancing the functions of fluorescence imaging and photothermal therapy. The superiority of the NIR-II region is demonstrated by fluorescence/photoacoustic imaging of blood vessels and the brain as well as photothermal ablation of the tumor. Finally, a summary of the challenges and perspectives of NIR-II AIEgens for in vivo theranostics is given.

Structural and process controls of NIR-II AIEgens realize manipulating of radiative (R) and nonradiative (NR) decay for precise theranostics.     

Thermal and mass spectrometric fragmentation of esters of deuterated long chain carboxylic acids

A method combining thermal fragmentation and mass spectrometry for the determination of the position of double bonds in an unsaturated ester is presented. The thermal fragmentation of methyl esters of deuterated long chain carboxylic acids yields a homologous series of olefins plus a homologous series of unsaturated esters. The positions of the deuterium atoms in the original ester are revealed by the deuterium content of its fragments as determined by mass spectrometry. Therefore, the positions of double bonds of a polyunsaturated acid can be determined by pyrolysis after saturation by deuterium. The structures of the unsaturated fragments are ascertained by mass spectrometric method, and the formation of the ion [M – 32] in the mass spectrometric fragmentation of unsaturated methyl esters is studied by means of deuterium labeling.     

The dynamics of impacting water droplets on alkanethiol self-assembled monolayers with co-adsorbed CH3 and CO2H terminal groups

The impact of water droplets (diameter 3.6 mm) at a fixed Weber number of 59 on solid surfaces with precisely tailored surface wettabilities was studied experimentally using a high-speed imaging camera at 2500 frames per second. Solid surface wettability was varied using four fractional mixtures of self-assembled monolayers of 1-octadecanethiol and 16-mercaptohexadecanoic acid. The surfaces so obtained are characterized for contact angle and chemical functionality using the axisymmetric drop shape analysis profile (ADSA-P) technique and Fourier transform infrared spectroscopy (FT-IR). Our results correlate the wetting effects of the impacting droplets with the surface energy and contact angle measurements of the tailored surfaces. Literature models for the maximum spreading diameter are employed and compared with those from our experiments. An equation is also proposed for the maximum spreading diameter which makes use of the correct contact angles and results in the least error among the models considered. As a consequence of Young's equation, the correct contact angles to be used for droplet impact dynamics should be the corresponding advancing angles on a smooth substrate of interest. We also conclude that accurate examination of literature models requires careful experimentation on impact dynamic data on well-prepared and characterized surfaces such as those presented here.     

Regioselective Synthesis of Polycyclic and Heptagon-embedded Aromatic Compounds through a Versatile π-Extension of Aryl Halides

A versatile π-extension reaction was developed based on the three-component cross-coupling of aryl halides, 2-haloarylcarboxylic acids, and norbornadiene. The transformation is driven by the direction and subsequent decarboxylation of the carboxyl group, while norbornadiene serves as an ortho-C−H activator and ethylene synthon via a retro-Diels–Alder reaction. Comprehensive DFT calculations were performed to account for the catalytic intermediates.     

Polymer and azo-dye composite: a photo-alignment layer for liquid crystals

In this article, we disclose a method to fabricate polymer-stabilised azo-dye photo alignment layers for liquid crystal. The idea includes the introduction of polymer network in the alignment layer, in optimal concentration, followed by two-step irradiation. The stabilised photo-alignment layer has been explored for different aspects of the display-related parameters, viz. anchoring energy, stability for various display-related environments as a function of concentration of monomer and irradiation, residual DC and voltage holding ratio. The composite photo-alignment layer offers well-suited parameters for the liquid crystal alignment and therefore could find application in a variety of modern photonic and display devices.     

Exact Meromorphic Stationary Solutions of the Real Cubic Swift‐Hohenberg Equation

We show that all meromorphic solutions of the stationary reduction of the real cubic Swift‐Hohenberg equation are elliptic or degenerate elliptic. We then obtain them all explicitly by the subequation method, and one of them appears to be a new elliptic solution.