Three air-stable tetrahedral manganese(ii) dihalide complexes [MnX2(DPEPO)] (DPEPO = bis[2-(diphenylphosphino)phenyl]ether oxide; X = Cl, Br and I) were prepared. All of the obtained compounds were structurally characterized by single-crystal X-ray diffraction analyses, which reveal that they crystallize in centrosymmetric space groups and feature an isolated mononuclear structure with Mn(2+) in a tetrahedral environment. Interestingly, these complexes show excellent photoluminescent performance in neat solid form, with the highest total quantum yield (Φtotal) of up to 70% recorded for the dibromide complex. Intense green flashes of light could be observed by the naked eye when rubbing the manganese(ii) complexes.

Intrinsic isotropic near-zero thermal expansion is discovered in borate crystal Zn B O with high transparency in the ultraviolet region. First-principles calculations demonstrate that the very low thermal expansion originates mainly from the invariability of the solid [B O ] truncated octahedra that are fixed by the [Zn O ] clusters in the ZBO structure.

Advancement in explosive systems toward miniaturization and enhanced safety has prompted the development of primary explosives with powerful detonation performance and relatively low sensitivities. Energetic coordination polymers (ECPs) as a new type of energetic materials have attracted wide attention. However, regulating the energetic characters of ECPs and establishing the relationship between structure and energetic property remains great challenges. In this study, two isomorphic 2D π-stacked solvent-free coordination polymers, [M(N 3 ) 2 (atrz)] n (M = Co 1, Cd 2; atrz = 4,4′-azo-1,2,4-triazole), were hydrothermally prepared and structurally characterized by X-ray diffraction. The two compounds exhibit reliable stabilities, remarkable positive enthalpies of formation, and prominent heats of detonation. The enthalpy of formation of 1 is 4.21 kJ•g −1 , which is higher than those of all hitherto known primary explosives. Repulsive steric clashes between the sensitive azide ions in 1 and 2 influence the mechanical sensitivities deduced from the calculated noncovalent interaction domains. The two energetic π-stacked ECPs 1 and 2 can serve as candidates for primary explosives with an approved level of safety.

Photochromism of N-methyl-4,4'-bipyridinium (MQ(+)) salts and their metal complexes has never been reported. A series of MQ(+) coordinated halozinc complexes [(MQ)ZnX(3)] (X = Cl (1), Br (2), I (3)) and [(MQ)ZnCl(1.53)I(1.47)](2)(MQ)ZnCl(1.68)I(1.32) (4), with better physicochemical stability than halide salts of the MQ(+) cation, have been found to exhibit different photochromic behaviors. Compounds 1-3 are isostructural, but only 1 and 2 show photochromism. Introduction of partial Cl atoms to nonphotochromic compound 3 yields compound 4, which also displays photochromism. The photochromic response of 1, 2, and 4 indicates the presence of their long-lived charge separation states, which originate from X → MQ(+) electron transfer according to ESR and XPS measurements. Studies on the influence of different coordinated halogen atoms demonstrate that the Cl atom may be a more suitable electron donor than Br and I atoms to design redox photochromic metal complexes.

Proton conductivity research on single crystals is essential to elucidate their conduction mechanism and guide the unidirectional crystal growth to improve the performance of electrolyte materials. Herein, we report a highly anisotropic proton-conductive 2D metal−organic framework (MOF) [Cu 2 (Htzehp) 2 (4,4′-bipy)]•3H 2 O (1•3H 2 O, H 3 tzehp = N-[2-(1Htetrazol-5-yl)ethyl]-L-hydroxyproline) with definite crystal structures showing single-crystal to single-crystal transformation between the anhydrate (1) and trihydrate (1•3H 2 O) phases. The hydrogen bonded chains consisted of well-defined lattice water molecules and hydroxyl functional groups of the Htzehp 2− ligand array inside the 2D interlayer spaces along the crystallographic a-axis ([100] direction) in 1•3H 2 O. Temperature-and humidity-dependent proton conductivity was achieved along the [100] and [010] directions, respectively. The anisotropic proton conductivity of σ[100]/σ[010] in a single crystal of 1•3H 2 O was as high as 2 orders of magnitude. The highest proton conductivity of 1.43 × 10 −3 S cm −1 of 1•3H 2 O at 80 °C and 95% relative humidity was observed among the reported 2D MOF crystals. The relation between the proton conductivity and structure was also revealed. The hydrogen bonded chain in 1•nH 2 O plays a significant role in the proton transport. The time-dependent proton conductivity and single-crystal X-ray diffraction measurements demonstrated that 1•3H 2 O is temperature-and humidity-stable and acts as an underlying electrolyte material for fuel cell applications.

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Discovering materials that exhibit zero linear compressibility (ZLC) behavior under hydrostatic pressure is extremely difficult. To date, only a handful of ZLC materials have been found, and almost all of them are ultrahard materials with densified structures. Here, to explore ZLC in nondense materials, a structural model analogous to the structure of the "Lu-Ban stool," a product of traditional Chinese woodworking invented 2500 years ago, is proposed. The application of this model to borates leads to the discovery of ZLC in AEB O (AE = Ca and Sr) with the unique "Lu-Ban stool"-like structure, which can obtain a subtle mechanical balance between pressure-induced expansion and contraction effects. Coupled with the very wide ultraviolet transparent windows, the ZLC behavior of AEB O may result in some unique but important applications. The applications of the "Lu-Ban stool" model open a new route for pursuing ZLC materials in nondense structural systems.

Deep eutectic mixtures were deployed for the preparation of porous layered [Sn3Se7]n2n- single crystals. The perforation on the layers accentuates the negative temperature dependence of its band gap, resulting in remarkable thermochromic performance. Substitution of the hydroxo group by the methyl group provides an enhanced hydrophobicity for the organic template, leading to an anhydrous product with a remarkably improved thermal stability and thus reversible thermochromic properties.