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Polyoxometalate (POM)-based materials are ideal candidates for implementing molecular memories, and rational POM molecule design is key to higher resistive switching (RS) performance. In this work, in order to obtain a deep structure–property correlation of POM-based memristors, three Anderson-based hybrids, i.e. two-component hybrids (MV)3(MnMo6O18L2)2·4DMF (1) and (MV)2[Cu(DMF)2](MnMo6O18L1)2·6DMF (2), and the three-component one (MV)2(Cu2I3)(MnMo6O18L2)·4CH3CN (3) (L = 2-(hydroxymethyl)-2-(pyridine-4-yl)-1,3-propanediol) have been structurally determined. These hybrids together with the precursors (methyl viologen (MV2+), CuI, and (MnMo6O18L2)) were further fabricated as memristors with the structure of ITO/active layer/Ag. Interestingly, three precursors are RS silent or have bad RS performance, but the incorporation of MV2+ in 1 and 2 can trigger the RS performances, and the further decoration of iodocuprate in 3 can render enhanced RS behavior (ON/OFF ratio: 2.32 × 102) with high thermal-tolerance temperature (240 °C) and extremely long-term stability. The RS mechanism could be assigned to the valence change (VC) induced by oxygen vacancy migrations. The presence of air-stable (MnMo6O18L2)3−-MV2+ donor–acceptor couples can stabilize the oxygen vacancies, which not only trigger the RS behaviors in ITO/1/Ag and ITO/2/Ag, but also result in extremely long-term stability in ITO/3/Ag. Besides, the oxygen vacancies can also be stabilized by Cu2I3 with intense cuprophilic interactions, which corresponds to enhanced RS properties in ITO/3/Ag. This mechanism could be validated by the following structural characters in 3: the stronger POM-MV2+ interactions, the better planarity of MV2+, the very short Cu⋯Cu distances and the ABAB-type packing fashion. The structure–property correlation in this work can provide a new strategy for the development of highly efficient and reliable memristors. [ABSTRACT FROM AUTHOR]

On the basis of variable-temperature single-crystal X-ray diffraction, variable-temperature/frequency dielectric analysis, variable-temperature solid-state nuclear magnetic resonance spectroscopy, and molecular dynamics simulations, here we present a new model of crystalline supramolecular rotor (i-PrNHMe2)[CdBr3], where a conformationally flexible near-spherical (i-PrNHMe2)+ cation functions as a rotator and a rod-like anionic coordination polymer {[CdBr3]−}∞ acts as the stator, and the adhesion of them is realized by charge-assisted hydrogen bonds. [ABSTRACT FROM AUTHOR]

The study about the effect of the stacking mode on the photo/electrical performance of crystalline organic/inorganic hybrids will be beneficial for the design of new photo/electrically active materials. In this work, D–π–A stilbazolium-type chromophores bearing novel ortho-N-alkyl substituents were synthesized and incorporated with iodoargentates to generate three crystalline stilbazolium/iodoargentate hybrids, i.e., [(CMAMP)(Ag2I3)]n (1), [(HMAMP)(Ag2I3)]n (2), and [(HMAHP)2(Ag5I7)]n (3). When the substitutes on the amine group range from –C2H5CN (for CMAMP+) to –C2H5OH (for HMAMP+), the same (Ag2I3)nn− anions will be produced, and the π⋯π stacking interactions among stilbazoliums will be observed from absence to presence (weak head-to-head H-aggregation). Furthermore, when the substituent on the ortho-N of pyridine was also set as –C2H5OH (for HMAHP+), more electron-rich (Ag5I7)n2n− anion can be generated, and strong head-to-tail H-aggregation among HMAHP+ cations will happen. The enhanced aggregation strengthening in 3 can lead to its larger blue-shift photoluminescence, higher photocurrent, and better resistive switching performance (much higher ON/OFF ratio of 4.51 × 102). Their binary resistive switching mechanism can be explained as the SCLC model, and the better photo/electrical performances of 3 stem from its stronger head-to-tail H-aggregations, more negatively charged (Ag5I7)n2n− anion, and stronger (Ag5I7)n2n−–HMAHP+ interaction. The highly delocalized π antibonding orbitals between the empty p-orbitals of ethylene in its LUMO of (HMAHP)22+ dimer of 3 also support this conclusion. The good structure–property correlation based on accurate structural information in these stilbazolium/iodoargentate hybrids will be beneficial for the design of next-generation memory devices. [ABSTRACT FROM AUTHOR]

Two new copper(I) iodide-based hybrids, i.e. (Py3P–O–PPy3)(Cu2I4) (1) and (Py3P–O–PPy3)(Cu4I6) (2) (Py = pyrrolidine), have been prepared, in which the tripodal diphosphonium (Py3P–O–PPy3)2+ is in situ generated in the one-pot synthesis. The disordered (Cu4I6)2− tetramers are rare with two sets of tetracuprate centers. Interestingly, 1 exhibits sensitive luminescence mechanochromism, which is ascribed to the disturbed cuprophilic Cu⋯Cu interactions and the crystalline packing adjustment by destroying C–H⋯I hydrogen bonds during mechanical force. In particular, the luminescence thermochromism is unique, whose fluorescence intensity is strengthened with the elevated temperature. This could be due to the S2–S1 internal conversion on the linear P–O–P backbone, which will be bent upon heating. Simultaneous luminescence thermo/mechanochromism can also be monitored in 1. However, no luminescence thermo/mechanochromic performances can be detected in 2, so the luminescence thermo/mechanochromism of 1 could be quenched with DMF. The conclusions in this work might provide a new large-scale synthesis strategy for intelligent responsive luminescent materials. [ABSTRACT FROM AUTHOR]

Studies on the recycling of uranium, such as its usage as new materials, can promote the safe treatment of nuclear waste. In this work, with the direction of transition-metal complex cations, three uranyl–organic frameworks (UOFs) with different dimensions have been synthesized via a hydrothermal reaction, i.e. [Cu(phen)2(SO4)(UO2)(TDC)·H2O]n (1), {[Zn(phen)3][(UO2)2(TDC)3(TDC)]·6H2O}n (2), and {[Cd(phen)3][(UO2)2(TDC)2(OX)·2H2O]}n (3), (TDC = thiophene-2,5-dicarboxylic acid, OX = oxalate, and phen = 1,10-phenanthroline). With the presence of SO42−, 1 presents a rare neutral 1-D Cu/U heterometallic chain. Under the similar [Zn(phen)3]2+ and [Cd(phen)3]2+ templates, 2 is a 2-D [(UO2)2(TDC)3]n planar non-interpenetrated honeycomb layer, but 3 presents an interesting twofold interpenetrated (6,3) sheet structure, which is led by the larger cavity of the hexagonal motif with the presence of the second ligand OX. This trend could be helpful for the oriented construction of UOFs. Intra- and inter-layer hydrogen bonds between the honeycomb structure and guest cations and π–π stacking interactions contribute to the stabilization of the overall framework. Complete quenching of uranyl luminescence via nonradiative decay can be observed in 1, and 2 and 3 emit yellow fluorescence with well-resolved vibronic fine structures. The interpenetrated arrangements could give rise to weakened uranyl emission. [ABSTRACT FROM AUTHOR]

Strong electron-poor cation diphenyliodonium was firstly incorporated with transition metal thiocyanates to obtain three new photo-sensitive hybrids, (DPI)3[Mn(SCN)5(H2O)]·0.25H2O (α-1), {(DPI)2[Ni(SCN)4]}n (α-2) and {(DPI)6[Cd3(SCN)12]}n (α-3) (DPI+ = diphenyliodonium), whose photo-induced structural transformations to corresponding β-phases have been disclosed. After irradiating, all the MX6 octahedrons stretch clearly along the M–S directions, and C–H⋯π interactions and the secondary hypervalent I(III)⋯S halogen bonds are weakened. The hydrogen bonds are also weakened, except for those in 1. Time-dependent solid-state UV-vis spectra, PXRD patterns and EPR spectra before and after irradiating were obtained to prove the irreversible structural transformations of the hybrids, during which minor structural adjustments occurred. Consequently, the fluorescence emission changed from blue (α-3) to yellow (β-3) upon irradiation. Interestingly, obvious photomagnetization on 1 with a χMT increase of 14.89% and photodemagnetization on 2 with a χMT decrease of 12.82% can be observed. Finally, these hybrids can be used as long-term inkless and erasable print media. This work demonstrates the potential application of diphenyliodonium-based hybrids in some photo-sensitive functional materials. [ABSTRACT FROM AUTHOR]

The use of crystalline metal-organic complexes with definite structures as multilevel memories can enable explicit structure-property correlations, which is significant for designing the next generation of memories. Here, four Zn-polysulfide complexes with different degrees of conjugation have been fabricated as memory devices. ZnS 6 (L) 2 -based memories (L = pyridine and 3-methylpyridine) can exhibit only bipolar binary memory performances, but ZnS 6 (L)-based memories (L = 2,2'-bipyridine and 1,10-phenanthroline) illustrate non-volatile ternary memory performances with high ON2/ON1/OFF ratios (10 4.22 /10 2.27 /1 and 10 4.85 /10 2.58 /1) and ternary yields (74% and 78%). Their ON1 states stem from the packing adjustments of organic ligands upon the injection of carriers, and the ON2 states are a result of the ring-to-chain relaxation of S 6 2- anions. The lower conjugated degrees in ZnS 6 (L) 2 result in less compact packing; consequently, the adjacent S 6 2- rings are too long to trigger the S 6 2- relaxation. The deep structure-property correlation in this work provides a new strategy for implementing multilevel memory by triggering polysulfide relaxation based on the conjugated degree regulation of organic ligands.