Homopolycyclotrimerization of A4‐type tetrayne: A new approach for the creation of a soluble hyperbranched poly(tetraphenylethene) with multifunctionalities

A tetraphenylethene‐containing A₄‐type tetrayne, named 1,1,2,2‐tetrakis(4‐ethynylphenyl)ethene is synthesized and its TaCl₅‐Ph₄Sn catalyzed homopolycyclotrimerization affords hyperbranched poly(tetraphenylethene) with high molecular weight (M_w = 280,000) in high yield (97%). The polymer shows good solubility and high thermal stability. It is aggregation‐enhanced emission (AEE)‐active and functions as a fluorescent chemosensor for explosive detection with a superamplification effect and large quenching constants up to 758,000 M^?1. The polymer shows high and tunable refractive indices (RI = 1.9288?1.6746) in a wide wavelength region. Porous fluorescent polymer thin film is prepared by breath figure (BF) methods and real‐time monitoring of the elusive BF formation process is realized. Photolithography of the thin films readily generates well‐resolved fluorescent photopattern without and with porous secondary structure. The polymer is metallified and pyrolysed to give magnetic ceramics with high magnetic susceptibilities (M_s = 83 emu/g) and near‐zero coercivity (H_c = 0.08 kOe). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4752–4764     

The monotonic property of the generalized root mean square

The link between a differential equation and its initial conditions is not quite as simple as usually imagined. Several examples illustrate the complications that can arise.     

Iridium α-Carboxyimine Complexes Hyperpolarized with para-Hydrogen Exist in Nuclear Singlet States before Conversion into Iridium Carbonates

The formation and hyperpolarization of an [Ir(H)₂(amine)(IMes)(η²-imine)]Cl complex that can be created in a hyperpolarized nuclear singlet state is reported. These complexes are formed when an equilibrium mixture of pyruvate, amine (benzylamine or phenylethylamine), and the corresponding imine condensation product, react with preformed [Ir(H)₂(amine)₃(IMes)]Cl. These iridium α-carboxyimine complexes exist as two regioisomers differentiated by the position of amine. When examined with para-hydrogen the hydride resonances of the isomer with amine trans to hydride become strongly hyperpolarized. The initial hydride singlet states readily transfer to the corresponding ¹³C₂ state in the labelled imine and exhibit magnetic state lifetimes of up to 11 seconds. Their ¹³C signals have been detected with up to 420 fold signal gains at 9.4 T. On a longer timescale, and in the absence of H₂, further reaction leads to the formation of neutral carbonate containing [Ir(amine)(η²-CO₃)(IMes)(η²-imine)]. Complexes are characterized by, IR, MS, NMR and X-ray diffraction.     

Eigenvalue Comparison on Bakry-Emery Manifolds

We prove a comparison theorem on the modulus of continuity of the solution of a heat equation with a drifting term on Bakry-Emery manifolds. A direct consequence of the result is an alternate proof of an eigenvalue comparison result of Bakry-Qian. Examples are given to show that the estimate is sharp. Discussions on an explicit lower estimate for the corresponding ODE and an application to the diameter lower bound for gradient shrinking solitons are also included.     

Structural and Theoretical Insights into the AIE Attributes of Phosphindole Oxide: The Balance Between Rigidity and Flexibility

Multiple intramolecular motions consume the excited‐state energy of luminogenic molecules upon photoexcitation and lower the emission efficiency. The low frequency rotational motion of aromatic rings can be facilely restricted by steric constraint in the condensed phase, but the high frequency bond stretching motion can hardly be suppressed by aggregation. In this work, three phosphorus‐containing heterocycles, 1,2,3,4,5‐pentaphenylphosphole‐1‐oxide (PPPO), 1,2,3‐triphenylphosphindole‐1‐oxide (TPPIO), and 1,2,3‐triphenylphosphindole (TPPI), were synthesized and characterized. Their optical properties, crystal‐packing manners, electronic features, and fluorescence dynamics were systematically investigated, and theoretical calculations were performed to decipher structure–property relationships. The results reveal that these luminogens are weak emitters in solutions but show strong emission in aggregates, exhibiting obvious aggregation‐induced emission (AIE) features. The aggregation‐insensitive stretching motion, which is dominant in PPPO, is lowered in TPPIO, enabling TPPIO to fluoresce much more efficiently than PPPO in aggregates. The stretching motion is even more lowered in TPPI, but its relatively planar conformation suffers emission quenching due to strong π–π stacking interactions in aggregates. Therefore, a twisted molecular conformation consisting of a rigid stator and a rotatable periphery is demonstrated to be a rational design for more efficient AIE luminogens.