Segregated Array Tailoring Charge-Transfer Degree of Organic Cocrystal for the Efficient Near-Infrared Emission beyond 760 nm.

Harvesting the narrow bandgap excitons of charge-transfer (CT) complexes for the achievement of near-infrared (NIR) emission has attracted intensive attention for its fundamental importance and practical application. Herein, the triphenylene (TP)-2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F TCNQ) CT organic complex is designed and fabricated via the supramolecular self-assembly process, which demonstrates the NIR emission with a maximum peak of 770 nm and a photoluminescence quantum yield (PLQY) of 5.4%.

A Rotorlike Supramolecular Assembly, {[K(18-crown-6)]PbI}, with a Reversible Breaking-Symmetry Phase Transition near Room Temperature.

A rotorlike supramolecular crystal, {[K(18-crown-6)]PbI}, is composed of a linear [PbI] chain acting as a stator and [K(18-crown-6)] cations fastened to the [PbI] chain and K-I bond like rotators and axes, respectively. A reversible breaking-symmetry phase transition occurs at ∼305 K. Variable-temperature H NMR spectra and dielectrics were used for the dynamic analysis of [K(18-crown-6)] cations in the crystal.

Vapochromic Behavior of a Chair-Shaped Supramolecular Metallacycle with Ultra-Stability.

A new discrete supramolecular metallacycle functionalized with an alkynylplatinum(II) bzimpy moiety was successfully prepared via coordination-driven self-assembly, and it displayed a reversible color change in the solid state between yellow and red, triggered by CH2Cl2 vapor or mechanical grinding. Notably, unlike many known vapochromic systems, the obtained vapochromic metallacycle exhibits ultra-stability, with the red color remaining unchanged in air for several months at room temperature or even under vacuum for >1 week. Further investigation revealed that the chair conformation of the metallacyclic scaffold, which was thought to prevent intermolecular steric repulsion between the alkyl chain and triethylphosphine, favored close molecular stacking through intermolecular Pt···Pt and π-π stacking interactions, thus allowing such vapochromic behavior with ultra-stability.

Rotor-synchronized dipolar-filter sequence at fast MAS in solid-state NMR.

Dipolar filters are of considerable importance for eliminating the (1)H NMR signal of the rigid components of heterogeneous compounds while selecting the signal of their mobile parts. On the basis of such filters, structural and dynamical information of these compounds can often be acquired through further manipulations (e.g.

Determination of coordination modes and estimation of the 31P-31P distances in heterogeneous catalyst by solid state double quantum filtered 31P NMR spectroscopy.

To overcome the separation difficulty of the palladium-based homogeneous catalyst, the palladium complex can be anchored on various supports such as silica. However, it is difficult to determine the amounts of the two coordination modes of the Pd nucleus, that is, Pd coordinates with one phosphorus atom and Pd coordinates with two phosphorus atoms. Here a (31)P double-quantum filtered (DQ-filtered) method in solid-state NMR is introduced for the palladium-based heterogenous catalyst system.

An investigation into the effect of potassium ions on the folding of silk fibroin studied by generalized two-dimensional NMR-NMR correlation and Raman spectroscopy.

We used generalized two-dimensional NMR-NMR correlation to examine the effect of potassium ions on the conformation transition in silk fibroin to investigate the possibility that the fairly high K+ ion content found in the distal end of silk-secreting ducts in the silkworms could have a bearing on natural formation of the silk fiber. This has enabled us to propose a detailed mechanism for the transition process. Our evidence indicates that increasing the [K+] from 0 to 3.

Generalized two-dimensional correlation analysis of NMR and Raman spectra for structural evolution characterizations of silk fibroin.

Generalized two-dimensional (2D) correlation spectroscopy was used to characterize the structural evolution of silk fibroin as the pH changed from 6.8 to 4.8, demonstrating that the conformational transitions of silk fibroin are induced step by step as the pH decreases.

An NMR approach applicable to biomolecular structure characterization.

A generalized 2D correlation NMR (GEN2D-NMR) scheme capable of substantially reducing the experimental time for two-dimensional correlation NMR experiments is described. The experimental time used in GEN2D-NMR is shortened to less than one-tenth of that required in traditional double Fourier transform 2D-NMR (FT2D-NMR) for a 13C-13C spin diffusion experiment for Nephila edulis spider threads. Experimentally, one needs to acquire many fewer points in GEN2D-NMR than that in FT2D-NMR in the evolution time domain.

Effect of pH and copper(II) on the conformation transitions of silk fibroin based on EPR, NMR, and Raman spectroscopy.

Much attention has been paid to the natural mechanism of silkworm spinning due to the impressive mechanical properties of the natural fibers. Our results in the present work show that the fractional changes of the conformational components in regenerated silk fibroin (SF) extracted from Bombyx mori fibers is remarkably pH- and Cu(II)-dependent as demonstrated by Cu(II) EPR, (13)C NMR, and Raman spectroscopy. Cu(II) coordination atoms in SF are changed from four nitrogens to two nitrogens and two oxygens as well as to one nitrogen and three oxygens when the pH is lowered from 8.