Reversible Single-Crystal to Single-Crystal Transformations of a Zn(II)–Salicyaldimine Coordination Polymer Accompanying Changes in Coordination Sphere and Network Dimensionality upon Dehydration and Rehydration

A fluorescent Zn­(II)–salicyaldimine coordination polymer, [Zn­(L^salpyca)­(H₂O)]_<i>n</i> (<b>1</b>; H₂L^salpyca = 4-hydroxy-3-(((pyridin-2-yl)­methylimino)­methyl)­benzoic acid), showing a one-dimensional (1D) zigzag chain structure has been hydro­(solvo)­thermally synthesized. Removal of coordination water molecules in <b>1</b> by thermal dehydration gives rise to the dehydration product [Zn­(L^salpyca)]_<i>n</i> (<b>1</b>′), which has a dizinc-based two-dimensional (2D) gridlike (4,4)-layer structure. X-ray powder diffraction (XRPD) patterns, thermogravimetric (TG) analyses, and infrared (IR) spectra all clearly indicate that the structure of <b>1</b> is quite flexible as a result of a reversible 1D–2D single-crystal to single-crystal (SCSC) transformation upon removal and rebinding of coordination water molecules, which accompanies changes in coordination sphere and network dimensionality. Additionally, Zn­(II)–salicyaldimine polymers <b>1</b> and <b>1</b>′ exhibit different solid-state photoluminescences at 458 and 480 nm, respectively. This is reasonably attributed to the close-packing effect and/or the influences of the differences on the conformation and the coordination mode of the L^salpyca ligand and the coordination geometry around the Zn­(II) center

The functionalised hexa-<i>peri</i>-hexabenzocoronenes by Sonogashira coupling method to modify the columnar mesophase behaviour

<div><p>In this paper, we present a series of different thermotropic discotic columnar liquid crystalline forms of mono-substituted functionalised hexabenzocoronene (HBC) carrying five alkyl chains. Using the Sonogashira coupling reaction, 1-ethynyl-4-alkylbenzene, 1-ethynyl-4-alkoxybenzene, and alkyl-4-ethynyl benzoate groups were introduced into mono-bromohexabenzocoronenes to obtain compounds <b>5–7</b>. These compounds obtained were characterised by ¹H and ¹³C-NMR, UV-Vis, and MALDI-MS spectrometry. The thermotropic liquid crystalline (LC) properties of the compounds were investigated by polarising optical microscopy (POM), differential scanning calorimetry (DSC), and powder X-ray diffractometry (XRD).</p></div

Broad Ranges and Fast Responses of Single-Component Blue-Phase Liquid Crystals Containing Banana-Shaped 1,3,4-Oxadiazole Cores

In this study, we synthesized two novel 1,3,4-oxadiazole-based bent-core liquid crystals (<b>OXD7*</b>, <b>OXD5B7F*</b>) containing a chiral tail that display broad ranges of the blue phase III (34 and 7 K, respectively); we characterized them using polarized optical microscopy, differential scanning calorimetry, and circular dichroism. The electro-optical responses of both of these liquid crystals are much faster than those of previously reported single-component blue-phase liquid crystals. To optimize its electro-optical performance, we mixed <b>OXD7*</b> (the blue-phase range of which is broader than that of <b>OXD5B7F*</b>) with its analogue <b>OXD6</b> (at weight ratios of 6:4 and 4:6). We also performed molecular modeling of single-component BPLCs (<b>OXD7*</b> and <b>OXD5B7F*</b>) to analyze the possible parameters affecting their blue phase ranges

Converting Nonliquid Crystals into Liquid Crystals by <i>N</i>‑Methylation in the Central Linker of Triazine-Based Dendrimers

Two triazine-based dendrimers were successfully prepared in 60–75% yields. These newly prepared dendrimers <b>2a</b> and <b>2b</b> containing the −NMe­(CH₂)₂NMe– and the −NMe­(CH₂)₄NMe– linkers between two G₃ dendrons, respectively, exhibit columnar phases during the thermal process. However, the corresponding dendrimers <b>1a</b> and <b>1b</b> containing the −NH­(CH₂)₂NH– and the −NH­(CH₂)₄NH– linkers between two G₃ dendrons, respectively, do not show any LC phases on thermal treatment. Computational investigations on molecular conformations reveal that <i>N</i>-methylation of the dendritic central linker leads dendrimers to possess more isomeric conformations and thus successfully converts non-LC dendrimers (<b>1a</b> and <b>1b</b>) into LC dendrimers (<b>2a</b> and <b>2b</b>)

Triboluminescence and Metal Phosphor for Organic Light-Emitting Diodes: Functional Pt(II) Complexes with Both 2‑Pyridylimidazol-2-ylidene and Bipyrazolate Chelates

We report the utilization of both pyrid-2-yl-imidazolylidene and dianionic bipz chelates as constituents in syntheses of a new series of charge-neutral Pt­(II) complexes <b>1</b>–<b>4</b>, among which complex <b>4</b> revealed remarkable triboluminescence, i.e., generation of photoemission upon grinding or cracking of the solid sample. The triboluminescence is found to be sensitive to the subtle changes of the associated substituents of pyrid-2-yl-imidazolylidene chelate, as verified by the disappearance of the triboluminescence for complexes <b>1</b>–<b>3</b>. Alternatively, the well-ordered solid packing of <b>3</b>, as indicated by the grazing incidence X-ray scattering experiment, serves as an ideal emitter for the fabrication of highly efficient OLEDs, rendering high external quantum efficienciy (25.9%) and luminesce efficiency (90 cd A^<b>–</b>1) at the practical brightness of 100 cd m^<b>–</b>2. The rather low roll-off in efficiency (24.4%, 85 cd A^<b>–</b>1 at high brightness of 1000 cd m^–2) is attributed to the short excited-state lifetime of <b>3</b> (∼800 ns) in the solid state, which in turn is associated with the MMLCT transition character