Thermochromic Color Switching to Temperature Controlled Volatile Memory and Counter Operations with Metal–Organic Complexes and Hybrid Gels

Temperature is often not considered as a precision stimulus for artificial chemical systems in contrast to the host–guest interactions related to many natural processes. Similarly, mimicking multi‐state volatile memory operations using a single molecular system with temperature as a precision stimulus is highly laborious. Here we demonstrate how a mixture of iron(II) chloride and bipyridine can be used as a reversible color‐to‐colorless thermochromic switch and logic operators. The generality of the approach was illustrated using Co^II and Ni^II salts that resulted in color‐to‐color transitions. DMSO gels of these systems, exhibited reversible opaque‐transparency switching. More importantly, optically readable multi‐state volatile memory with temperature as a precision input has been demonstrated. The stored data is volatile and is lost instantaneously upon withdrawal or change of temperature. Simultaneous read‐out at multiple wavelengths results in single‐input/multi‐output sequential logic operations such as data accumulators (counters) leading to volatile memory states. The present system provides access to thermoresponsive materials wherein temperature can be used as a precision stimulus.     

A Multistate pH‐Triggered Nonlinear Optical Switch

By using hyper‐Rayleigh scattering experiments and quantum‐chemical calculations, we demonstrate that nonlinear optics can be used to probe unequivocally, within a non‐destructive process, the multiple electronic states that are activated upon pH‐ and light‐triggered transformations of the 4′‐hydroxyflavylium ion. These results open new perspectives in the design of molecular‐scale high‐density optical memory.     

Encoding and Processing of Alphanumeric Information by Chemical Mixtures

A novel infochemical device that is based on ¹H NMR readout of chemical information is presented. This chemical encoding system utilizes two measurable parameters of homogeneous mixtures, chemical shift and peak integration, for three different applications: 1) a text‐encoding device that is based on spectral representation of a sequence of symbols, 2) encoding of 21‐digit binary numbers, each represented by an NMR spectrum, and their algebraic manipulations, such as addition and subtraction, and 3) encoding of 21‐digit decimal numbers. The first application enables molecular information storage and encryption. The relative concentration of each component, as measured by the relevant peak integration, can represent a symbol. The second application of this system, in addition to its obvious memory capability, enables mathematical operations. The NMR spectrum of a given mixture represents a 21‐digit binary number where each of the peaks encodes for a specific digit. In any of the input mixtures (numbers) each compound is either present or absent, representing either 1 or 0, respectively. We used the various binary numbers to carry out addition operations by combining two or more solutions (numbers). Subtraction operations were also preformed by digital processing of the information. The third application is the representation of decimal numbers. As before, each of the peaks encodes for a specific digit. In any of the input mixtures each compound is present in one of 10 different relative concentrations, representing the 10 digits of a decimal number.     

Towards Polyoxometalate‐Cluster‐Based Nano‐Electronics

We explore the concept that the incorporation of polyoxometalates (POMs) into complementary metal oxide semiconductor (CMOS) technologies could offer a fundamentally better way to design and engineer new types of data storage devices, due to the enhanced electronic complementarity with SiO₂, high redox potentials, and multiple redox states accessible to polyoxometalate clusters. To explore this we constructed a custom‐built simulation domain bridge. Connecting DFT, for the quantum mechanical modelling part, and mesoscopic device modelling, confirms the theoretical basis for the proposed advantages of POMs in non‐volatile molecular memories (NVMM) or flash‐RAM.     

Ternary Flexible Electro‐resistive Memory Device based on Small Molecules

Flexible memory devices have continued to attract more attention due to the increasing requirement for miniaturization, flexibility, and portability for further electronic applications. However, all reported flexible memory devices have binary memory characteristics, which cannot meet the demand of ever‐growing information explosion. Organic resistive switching random access memory (RRAM) has plenty of advantages such as simple structure, facile processing, low power consumption, high packaging density, as well as the ability to store multiple states per bit (multilevel). In this study, we report a small molecule‐based flexible ternary memory device for the first time. The flexible device maintains its ternary memory behavior under different bending conditions and within 500 bending cycles. The length of the alkyl chains in the molecular backbone play a significant role in molecular stacking, thus guaranteeing satisfactory memory and mechanical properties.     

Molecular Spintronics Based on Single‐Molecule Magnets Composed of Multiple‐Decker Phthalocyaninato Terbium(III) Complex

Unlike electronics, which is based on the freedom of the charge of an electron whose memory is volatile, spintronics is based on the freedom of the charge, spin, and orbital of an electron whose memory is non‐volatile. Although in most GMR, TMR, and CMR systems, bulk or classical magnets that are composed of transition metals are used, this Focus Review considers the growing use of single‐molecule magnets (SMMs) that are composed of multinuclear metal complexes and nanosized magnets, which exhibit slow magnetic‐relaxation processes and quantum tunneling. Molecular spintronics, which combines spintronics and molecular electronics, is an emerging field of research. Using molecules is advantageous because their electronic and magnetic properties can be manipulated under specific conditions. Herein, recent developments in [LnPc]‐based multiple‐decker SMMs on surfaces for molecular spintronic devices are presented. First, we discuss the strategies for preparing single‐molecular‐memory devices by using SMMs. Next, we focus on the switching of the Kondo signal of [LnPc]‐based multiple‐decker SMMs that are adsorbed onto surfaces, their characterization by using STM and STS, and the relationship between the molecular structure, the electronic structure, and the Kondo resonance of [TbPc₂]. Finally, the field‐effect‐transistor (FET) properties of surface‐adsorbed [LnPc₂] and [Ln₂Pc₃] cast films are reported, which is the first step towards controlling SMMs through their spins for applications in single‐molecular memory and spintronics devices.     

A Molecular Ferroelectric Showing Room‐Temperature Record‐Fast Switching of Spontaneous Polarization

Fast switching of spontaneous polarization (P_s) is one of the most essential requirements for ferroelectrics used in the field of data storage. However, in contrast to inorganic counterparts, the low operating frequency (<500 Hz) for molecular ferroelectrics severely hinders their large‐scale applications. Herein, for the first time, we achieved the room‐temperature fastest switching of the P_s in a new molecular ferroelectric, N‐methylmorpholinium trinitrophenolate ( 1 ), which displays notable ferroelectricity (P_s=3.2 μc cm^?2). Strikingly, electric polarizations of 1 have been switched under a record‐high frequency of 263 kHz, and this performance remains stable without any obvious fatigue after ca. 2×10⁵ switching cycles. To our knowledge, 1 is the first organic ferroelectric to switch polarization at such a high operating frequency, exceeding the majority of organic ferroelectrics, which opens up new possibilities for its potential in the field of non‐volatile memory.     

Ultraviolet–Visible Kinetic Study of the Uncatalyzed Bromate Oscillator with Phenol by Multivariate Curve Resolution

A kinetic study of the uncatalyzed bromate oscillator (UBO) using phenol was carried out by chemometric analysis of the UV/Vis data. The reaction was studied with different starting concentrations of the reagents (sulfuric acid and potassium bromate) and by changing phenol for 2‐bromophenol and 4‐bromophenol. The number of chemical absorbing species involved in the UV/Vis data was established by singular value decomposition and by the residual fit parameter. Multivariate curve resolution with alternating least squares generated valuable information about the different chemical species along the process (spectral and concentration profiles). These results show the presence of four principal components: two intermediates and two products. The products can be assigned as o‐quinone and 4,4′‐diphenoquinone, and the principal components associated with the intermediates represent the linear combination of all the intermediates in the reaction mixture. These data were used to generate a model of the UBO‐phenol oscillator that reproduces qualitatively the experimental results.     

Storage of Electrical Information in Metal–Organic‐Framework Memristors

Single crystals of a cyclodextrin‐based metal–organic framework (MOF) infused with an ionic electrolyte and flanked by silver electrodes act as memristors. They can be electrically switched between low and high conductivity states that persist even in the absence of an applied voltage. In this way, these small blocks of nanoporous sugar function as a non‐volatile RRAM memory elements that can be repeatedly read, erased, and re‐written. These properties derive from ionic current within the MOF and the deposition of nanometer‐thin passivating layers at the anode flanking the MOF crystal. The observed phenomena are crucially dependent on the sub‐nanometer widths of the channels in the MOF, allowing the passage of only smaller ions. Conversely, with the electrolyte present but no MOF, there are no memristance or memory effects.     

Exploring the Fundamental Structures of Life: Non‐Targeted,Chemical Analysis of Single Cells and Subcellular Structures

Cells are a basic functional and structural unit of living organisms. Both unicellular communities and multicellular species produce an astonishing chemical diversity, enabling a wide range of divergent functions, yet each cell shares numerous aspects that are common to all living organisms. While there are many approaches for studying this chemical diversity, only a few are non‐targeted and capable of analyzing hundreds of different chemicals at cellular resolution. Here, we review the non‐targeted approaches used to perform comprehensive chemical analyses, provide chemical imaging information, or obtain high‐throughput single‐cell profiling data. Single‐cell measurement capabilities are rapidly increasing in terms of throughput, limits of detection, and completeness of the chemical analyses; these improvements enable their application to understand ever more complex physiological phenomena, such as learning, memory, and behavior.     

Synthesis,Characterization, and Non‐Volatile Memory Device Application of an N‐Substituted Heteroacene

N‐substituted heteroacenes have been widely used as electroactive layers in organic electronic devices, and only a few of them have been investigated in organic resistive memory devices. Here, a novel N‐substituted heteroacene 2‐(4′‐(diphenylamino)phenyl)‐4,11‐bis((triisopropylsilyl)ethynyl)‐1H‐imidazo[4,5‐b]phenazine ( DBIP ) has been designed, synthesized, and characterized. Sandwich‐structure memory devices based on DBIP have been fabricated and the devices show non‐volatile and stable memory character with good endurance performance.     

Development of ambient sampling chemi/chemical ion source with dielectric barrier discharge

The development of a new configuration of chemical ionization (CI)‐based ion source is presented. The ambient air containing the gaseous sample is sniffed into an enclosed ionization chamber which is of sub‐ambient pressure, and is subsequently mixed with metastable species in front of the ion inlet of the mass spectrometer. Metastable helium atoms (He*) are used in this study as the primary ionizing agents and are generated from a dielectric barrier discharge (DBD) source. The DBD is powered by an AC high‐voltage supply and the configuration of the electrodes is in such a way that the generated plasma is confined within the discharge tube and is not extended into the ionization chamber. The construction of the ion source is simple, and volatile compounds released from the bulky sample can also be analyzed directly by approaching the sample to the sampling nozzle. When combined with heated nitrogen or other desorption methods, its application can also be extended to non‐volatile compounds, and the consumption for helium can be kept minimum solely for maintaining the stable discharge and gas phase ionization. Applications to non‐proximate sample analysis, direct determination of active ingredients in drug tablets and the detection of trace explosive such as hexamethylene triperoxide diamine are demonstrated. Copyright © 2010 John Wiley & Sons, Ltd.     

A Memristive Element Based on an Electrically Controlled Single‐Molecule Reaction

The exponential proliferation of data during the information age has required the continuous exploration of novel storage paradigms, materials, and devices with increasing data density. As a step toward the ultimate limits in data density, the development of an electrically controllable single‐molecule memristive element is reported. In this device, digital information is encoded through switching between two isomer states by applying a voltage signal to the molecular junction, and the information is read out by monitoring the electrical conductance of each isomer. The two states are cycled using an electrically controllable local‐heating mechanism for the forward reaction and catalyzed by a single charge‐transfer process for the reverse switching. This single‐molecule device can be modulated in situ, is fully reversible, and does not display stochastic switching. The I–V curves of this single‐molecule system also exhibit memristive character. These features suggest a new approach for the development of molecular switching systems and storage‐class memories.     

Logic Information Communication in a Fluorescent Molecular Switch

Based on the chemical‐sensitive fluorescence emission behaviors of the molecular switch 4‐bromo‐5‐methoxy‐2‐(2‐pyridyl)thiazole ( 2‐BMPT ), the communication of logic information between two functional units has been realized. With the rational control of the protonation and coordination reaction of 2‐BMPT , an upstream switching unit (a 1:2 demultiplexer) and two downstream data‐processing units are involved and interconnected in the communication. The two output states of the 1:2 demultiplexer serve as the initial input states of the two parallel downstream data‐processing units, which execute the information communication between the two circuit layers. Furthermore, in the parallel data‐processing layer, the logic gates of INHIBIT and YES accomplish their specific logic functions. Therefore, a molecular cascade circuit composed of an upstream switch and two downstream processing units has been constructed based on the chemical‐modulated fluorescence properties of 2‐BMPT .     

分子纳米磁体的研究进展及应用

分子磁学主要研究无机配合物以及有机自由基的电子结构和磁性之间的关系。近些年发展起来的分子纳米磁体可以在单分子尺度上实现磁双稳态,独立作为一个磁功能单元,可能突破尺寸对传统磁性材料的制约,有望实现超高密度磁存储。分子纳米磁体中清晰的量子态也为量子退相干研究提供了化学调控的手段,这将为量子计算机提供物质基础。本文简要介绍了分子纳米磁体的概念和特征,并对研究进展进行了简要综述。     

Cryogenic OrbiSIMS Localizes Semi‐Volatile Molecules in Biological Tissues

OrbiSIMS is a recently developed instrument for label‐free imaging of chemicals with micron spatial resolution and high mass resolution. We report a cryogenic workflow for OrbiSIMS (Cryo‐OrbiSIMS) that improves chemical detection of lipids and other biomolecules in tissues. Cryo‐OrbiSIMS boosts ionization yield and decreases ion‐beam induced fragmentation, greatly improving the detection of biomolecules such as triacylglycerides. It also increases chemical coverage to include molecules with intermediate or high vapor pressures, such as free fatty acids and semi‐volatile organic compounds (SVOCs). We find that Cryo‐OrbiSIMS reveals the hitherto unknown localization patterns of SVOCs with high spatial and chemical resolution in diverse plant, animal, and human tissues. We also show that Cryo‐OrbiSIMS can be combined with genetic analysis to identify enzymes regulating SVOC metabolism. Cryo‐OrbiSIMS is applicable to high resolution imaging of a wide variety of non‐volatile and semi‐volatile molecules across many areas of biomedicine.     

Synthesis of Pyrimidine and Pyran Derivatives with the Related Systems and the Study of Their Behavior in the Liquid Solutions

This study aims to synthesis of condensed and non‐condensed heterocyclic rings with long fatty chains as surface active biological compounds. 2‐Cyano‐3‐(dimethylamino)‐N‐octadecylacrylamide ( 5 ) was used to synthesize pyrimidine, pyran, and other condensed products by interacting with appropriate chemical reagents. These compounds were transferred to nonionic surface‐active agents by condensation with propylene oxide. The surface and biological properties showed that these compounds have a high solubility that helps them in easy absorption and adsorption with other compounds. In addition, they have a high ability to decrease the surface tension of the liquids, good wetting, and emulsification power, which can be used at different temperatures without losing their surface or biological properties and enable them for use in industrial and pharmaceutical purposes easily.     

Open‐Shell‐Character‐Based Molecular Design Principles: Applications to Nonlinear Optics and Singlet Fission

Open‐shell character, e. g., diradical character, is a quantum chemically well‐defined quantity in ground‐state molecular systems, which is not an observable but can quantify the degree of effective bond weakness in the chemical sense or electron correlation strength in the physical sense. Because this quantity also correlates to specific excited states, physicochemical properties concerned with those states are expected to strongly correlate to the open‐shell character. This feature enables us to open a new path to revealing the mechanism of these properties as well as to realizing new design principles for efficient functional molecular systems. This account explains the open‐shell‐character‐based molecular design principles and introduces their applications to the rational design of highly efficient nonlinear optical and singlet fission molecular systems.     

Efficient calculation of open quantum system dynamics and time‐resolved spectroscopy with distributed memory HEOM (DM‐HEOM)

Time‐ and frequency‐resolved optical signals provide insights into the properties of light‐harvesting molecular complexes, including excitation energies, dipole strengths and orientations, as well as in the exciton energy flow through the complex. The hierarchical equations of motion (HEOM) provide a unifying theory, which allows one to study the combined effects of system‐environment dissipation and non‐Markovian memory without making restrictive assumptions about weak or strong couplings or separability of vibrational and electronic degrees of freedom. With increasing system size the exact solution of the open quantum system dynamics requires memory and compute resources beyond a single compute node. To overcome this barrier, we developed a scalable variant of HEOM. Our distributed memory HEOM, DM‐HEOM, is a universal tool for open quantum system dynamics. It is used to accurately compute all experimentally accessible time‐ and frequency‐resolved processes in light‐harvesting molecular complexes with arbitrary system‐environment couplings for a wide range of temperatures and complex sizes. © 2018 Wiley Periodicals, Inc.