Molecular all-photonic encoder-decoder

In data processing, an encoder can compress digital information for transmission or storage, whereas a decoder recovers the information in its original form. We report a molecular triad consisting of a dithienylethene covalently linked to two fulgimide photochromes that performs as an all-photonic single-bit 4-to-2 encoder and 2-to-4 decoder. The encoder compresses the information contained in the four inputs into two outputs. The inputs are light of four different wavelengths that photoisomerize the fulgimide, dithienylethene, or both. The outputs are absorbance at two wavelengths. The two decoder inputs are excitation at two wavelengths, whereas the four outputs, which recover the information compressed into the inputs, are absorbance at two wavelengths, transmittance at one wavelength, and fluorescence emission. The molecule can be cycled through numerous encoder and decoder functions without significant photodecomposition. Molecular photonic encoders and decoders could potentially be used for labeling and tracking of nano- and microscale objects as well as for data manipulation.     

Multi-input photonic molecular logic gates based on the styrylpyridine–benzomerocyanine dyad

The efficiency of interphotochromic energy transfer in the biphotochromic styrylpyridine?benzomerocyanine dyad is 66% due to spatial and spectral separation of two photochromes. Therefore, both photochromes conserve their ability to photoisomerization. By using the photoisomerization of the photochromes for switching between different photostationary states, it has been shown that the dyad can function as photonic three- and four-input molecular logic gates, particularly a 4-to-2 encoder and a parity checker.     

Multiphotochromic Systems Based on Hybrid Organic–Inorganic Nanoparticles as “Super-Photochromes” for Photonic Molecular Logic Gates

High Energy Chemistry - When photochromes function as a photonic molecular logic gate (MLG), the problem of uncertainty of the final state of the gate arises at the level of a single molecule,...     

Molecular AND and INHIBIT gates based on control of porphyrin fluorescence by photochromes

A molecular triad consisting of a porphyrin (P) covalently linked to two photochromes-one from the dihydroindolizine family (DHI) and one from the dihydropyrene family (DHP)-has been synthesized and found to act as either a molecular AND logic gate or an INHIBIT gate, depending on the inputs and initial state of the photochromes. The basis of these functions is quenching of porphyrin fluorescence (output of the gates) by the photochromes. The spiro form of DHI does not quench porphyrin fluorescence, whereas its betaine isomer strongly quenches by photoinduced electron transfer. DHP also quenches porphyrin fluorescence, but its cyclophanediene isomer does not. The triad has been designed using suitable energetics and electronic interactions, so that although these quenching phenomena may be observed, independent isomerization of the attached photochromes still occurs. This makes it possible to switch porphyrin fluorescence on or off by isomerization of the photochromes using various combinations of inputs such as UV light, red light, and heat.     

A differential ICT based molecular probe for multi-ions and multifunction logic circuits

This paper presents anthraquinone and benzimidazole based hybrid molecular architect as the state of the art for multifunctional molecular logic circuits. The moleculator exhibits differential output behavior towards F(-), Zn(2+) and Cu(2+) ions to provide opportunities for elaboration of XOR, INHIBIT, XNOR, AND, OR, NOR, logic functions and their integrated logic functions half-adder, half-subtractor and comparator within a single molecule. These integral logic functions can be reprogrammed by self-annihilation or by another additional input in the same cell. This single molecule behaves uniquely where different logic functions can be operated and reset by using different inputs and outputs.     

Light‐Driven Reversible Intermolecular Proton Transfer at Single‐Molecule Junctions

Photoresponsive molecular systems are essential for molecular optoelectronic devices, but most molecular building blocks are non‐photoresponsive. Employed here is a photoinduced proton transfer (PIPT) strategy to control charge transport through single‐molecule azulene junctions with visible light under ambient conditions, which leads to a reversible and controllable photoresponsive molecular device based on non‐photoresponsive molecules and a photoacid. Also demonstrated is the application of PIPT in two single‐molecule AND gate and OR gate devices with electrical signal as outputs.     

Multiple molecular logic functions and molecular calculations facilitated by surfactant's versatility

Two isomeric compounds and , combining intramolecular charge transfer (ICT) and photoinduced electron transfer (PET) mechanisms together, were designed and used as logic gates with configurable multiple outputs; ten different logic functions (AND, NAND, OR, NOR, XNOR, INHIBIT, YES, NO, PASS 1 and PASS 0) were achieved by varying the inputs threshold or by altering the inputs; furthermore, half addition and half subtraction were performed within (or ); the concept demonstrated here may provide a strategy for constructing more integrated molecular level devices with multiple functions.     

Data and signal processing using photochromic molecules

Photochromes are chromophores that are reversibly isomerized between two metastable forms using light, or light and heat. When photochromes are covalently linked to other chromophores, they can act as molecular photonic analogues of electronic transistors. As bistable switches, they can be incorporated into the design of molecules capable of binary arithmetic and both combinatorial and sequential digital logic operations. Small ensembles of such molecules can perform analogue signal modulation similar to that carried out by transistor amplifiers. Examples of molecules that perform multiple logic functions, act as control elements for fluorescent reporters, and mimic natural photoregulatory functions are presented.     

A fluorescent molecular logic gate with multiply-configurable dual outputs

A simple molecule, L, diethylenetriamine bearing anthracene fragments at both ends, behaves as a fluorescent molecular logic gate with "multiply-configurable dual outputs", capable of demonstrating five different logic functions operated by proton (H+) and transition metal cations (Mn+) as inputs.     

Highly Sensitive INHIBIT and XOR Logic Gates Based on ICT and ACQ Emission Switching of a Porphyrin Derivative

Fluorescence‐switch‐based logic devices are very sensitive compared with most of the reported devices based on UV/Vis absorption systems. Herein, we demonstrate that a simple molecule, 5,10,15,20‐tetra‐(4‐aminophenyl)porphyrin (TAPP), shows protonation‐induced multiple emission switches through intramolecular charge transfer and/or aggregation‐caused quenching. Highly sensitive INHIBIT and XOR logic gates can be achieved by combining the intermolecular assembly with the intramolecular photoswitching of diprotonated TAPP (TAPPH₂²⁺). In addition, molecular simulations have been performed by DFT for a better understanding of the emission‐switching processes.     

Determination of the Degree of Charge‐Transfer Contributions to Surface‐Enhanced Raman Spectroscopy

We explore the application of a previously suggested formula for determining the degree of charge transfer in surface‐enhanced Raman scattering (SERS). SERS is often described as a phenomenon which obtains its enhancement from three major sources, namely the surface plasmon resonance, charge‐transfer resonances as well as possible molecular resonances. At any chosen excitation wavelength, it is possible to obtain contributions from several sources and this has led to considerable confusion. The formula for the degree of charge transfer enables one to separate these effects, but it requires that spectra be obtained either at two or more different excitation wavelengths or as a function of applied potential. We apply this formula to several examples, which display rather large charge‐transfer contributions to the spectrum. These are p‐aminothiophenol (PATP), tetracyano‐ ethylene (TCNE) and piperidine. In PATP we can show that several lines of the same symmetry give the same degree of charge transfer. In TCNE we are able to identify the charge‐transfer transition, which contributes to the effect, and are able to independently determine the degree of charge transfer by wavenumber shifts. This enables a comparison of the two techniques of measurement. In piperidine, we present an example of molecule to metal charge transfer and show that our definition of charge transfer is independent of direction.     

含氧化还原活性基团的荧光分子开关构建与门

报道了一个基于光致电子转移(PET)机理的双稳态荧光分子开关,其中具有氧化还原活性的二茂铁基团作为荧光团蒽PET过程的氧化还原控制单元,通过双Schiff碱C=N键与蒽相连。研究了不同条件下蒽的荧光发射行为。以不同的化学试剂作为体系的输入信号,以不同的荧光发射强度作为输出信号,利用荧光分子开关的质子化反应和氧化反应实现了一个分子水平的逻辑功能。输入信号及其相应的输出结果在分子水平上符合数字逻辑与门的真值表。     

Digital processing with a three-state molecular switch

Certain molecular switches respond to input stimulations producing detectable outputs. The interplay of these signals can be exploited to reproduce basic logic operations at the molecular level. The transition from simple logic gates to complex digital circuits requires the design of chemical systems able to process multiple inputs and outputs. We have identified a three-state molecular switch that responds to one chemical and two optical inputs producing two optical outputs. We have encoded binary digits in its inputs and outputs applying positive logic conventions and demonstrated that this chemical system converts three-digit input strings into two-digit output strings. The logic function executed by the three-state molecular switch is equivalent to that of a combinational logic circuit integrating two AND, two NOT, and one OR gate. The three states of the molecular switch are a colorless spiropyran, a purple trans-merocyanine, and its yellow-green protonated form. We have elucidated their structures by X-ray crystallography, (1)H NMR spectroscopy, COSY and NOE experiments, as well as density functional calculations. The three input stimulations controlling the interconversion of the three states of the molecular switch are ultraviolet light, visible light, and H(+). The two outputs are the absorption bands in the visible region of the two colored states of the molecular switch. We have monitored the switching processes and quantified the associated thermodynamic and kinetic parameters with the aid of (1)H NMR and visible absorption spectroscopies.     

Anion Sensors as Logic Gates: A Close Encounter?

Computers have become smarter, smaller, and more efficient due to the downscaling of silicon‐based components. Top‐down miniaturisation of silicon‐based computer components is fast reaching its limitations because of physical constraints and economical non‐feasibility. Therefore, the possibility of a bottom‐up approach that uses molecules to build nano‐sized devices has been initiated. As a result, molecular logic gates based on chemical inputs and measurable optical outputs have captured significant attention very recently. In addition, it would be interesting if such molecular logic gates could be developed by making use of ion sensors, which can give significantly sensitive output information. This review provides a brief introduction to anion receptors, molecular logic gates, a comprehensive review on describing recent advances and progress on development of ion receptors for molecular logic gates, and a brief idea about the application of molecular logic gates.     

Integrated Molecular Logic Using a Multistate Electrochromic Platform

Herein, we present an approach that integrates molecular logic functions using surface-confined metallo-organic assemblies. These assemblies are electrochromic and mimic the behaviour of logic elements. The logic elements are addressed individually by electrochemical methods, and their outputs are simultaneously read-out optically by UV/Vis absorption spectroscopy. The versatility of our setup is demonstrated by the integration of two multi-component assemblies; each acting as ternary logic elements. We used also a laminated cell configuration to demonstrate color-to-color and color-to-transparent transitions. This concept offers a route for the future development of devices with multiple logic states.     

Picking Out Logic Operations in a Naphthalene β-Diketone Derivative by Using Molecular Encapsulation,Controlled Protonation,and DNA Binding

On–off switching and molecular logic in fluorescent molecules are associated with what chemical inputs can do to the structure and dynamics of these molecules. Herein, we report the structure of a naphthalene derivative, the fashion of its binding to β-cyclodextrin and DNA, and the operation of logic possible using protons, cyclodextrin, and DNA as chemical inputs. The compound crystallizes out in a keto-amine form, with intramolecular N−H⋅⋅⋅O bonding. It shows stepwise formation of 1:1 and 1:2 inclusion complexes with β-cyclodextrin. The aminopentenone substituents are encapsulated by β-cyclodextrin, leaving out the naphthalene rings free. The binding constant of the β-cyclodextrin complex is 512 m⁻¹. The pK_a value of the guest molecule is not greatly affected by the complexation. Dual input logic operations, based on various chemical inputs, lead to the possibility of several molecular logic gates, namely NOR, XOR, NAND, and Buffer. Such chemical inputs on the naphthalene derivative are examples of how variable signal outputs based on binding can be derived, which, in turn, are dependent on the size and shape of the molecule.     

Molecule-based photonically switched half and full adder

A single molecule logic gate using electronically excited states and ionization/fragmentation can take advantage of the differences in cross-sections for one and two photon absorption. Fault tolerant optically pumped half adder and full adder are discussed as applications. A full adder requires two separate additions, and the logic concatenation that is required to implement this is physically achieved by an intramolecular transfer along the side chain of 2-phenylethyl-N,N-dimethylamine (PENNA). Solutions of the kinetic equations for the temporal evolution of the concentration of different states in the presence of time-varying laser fields are used to illustrate the high contrast ratios that are potentially possible for such devices.     

Photochrome-coupled metal complexes: molecular processing of photon stimuli

The frontiers of novel photoresponsive materials constructed with photochromes and transition metal complexes are surveyed in this review. Strategies to develop new photofunctions are categorized into four types. In the first category, intramolecular electronic interactions between photochromes and metal complexes produce entangled responses such as redox-regulated photochromic reactions or tristable photochromism. In the second, light-induced molecular structural rearrangements of photochromes induce the transformation of flexible and labile coordination structures, which can be applied to complex photomechanics or photoelectron conversion. In the third, the photochromic moiety also acts as a photonic switch, transmitting a metal-metal interaction when it is located between two metal complex moieties. The last category concerns the development of new photochromic reactions, involving metal-ligand bond rearrangements. These reactions potentially induce drastic electronic tuning of the metal center, and can be used to develop light-driven molecular machines.     

A molecular full-adder and full-subtractor, an additional step toward a moleculator

Over the past decade, there has been remarkable progress in the development of molecular logic and arithmetic systems, which has brought chemists closer to the realization of a molecular scale calculator (a Moleculator). This paper describes a significant step in this direction. By integrating past and new approaches for molecular logic reconfiguration, we were able to load advanced arithmetic calculations onto a single molecular species. Exchanging chemical inputs, monitoring at several wavelengths simultaneously, as well as using negative logic for the transmittance mode significantly increase the input and output information channels of the processing molecule. Changing the initial state of the processor is an additional approach used for altering the logical output of the device. Finally, introducing degeneracy to the chemical inputs or, alternatively, controlling their interactions to form identical chemical states minimizes the complexity of realizing three-bits addition and subtraction at the molecular scale. Consequently, using a commercially available fluorescein molecule, acid and base chemical inputs, and a simple UV-vis measurement setup, integration of a full-adder and, for the first time, a full-subtractor is now possible within individual molecules.     

Modular multi-level circuits from immobilized DNA-based logic gates

One of the fundamental goals of molecular computing is to reproduce the tenets of digital logic, such as component modularity and hierarchical circuit design. An important step toward this goal is the creation of molecular logic gates that can be rationally wired into multi-level circuits. Here we report the design and functional characterization of a complete set of modular DNA-based Boolean logic gates (AND, OR, and AND-NOT) and further demonstrate their wiring into a three-level circuit that exhibits Boolean XOR (exclusive OR) function. The approach is based on solid-supported DNA logic gates that are designed to operate with single-stranded DNA inputs and outputs. Since the solution-phase serves as the communication medium between gates, circuit wiring can be achieved by designating the DNA output of one gate as the input to another. Solid-supported logic gates provide enhanced gate modularity versus solution-phase systems by significantly simplifying the task of choosing appropriate DNA input and output sequences used in the construction of multi-level circuits. The molecular logic gates and circuits reported here were characterized by coupling DNA outputs to a single-input REPORT gate and monitoring the resulting fluorescent output signals.