Multi-Channel Receptors and Their Relation to Guest Chemosensing and Reconfigurable Molecular Logic Gates

Multiple Molecular Logic Gate Arrays in One System of (2-(2’-Pyridyl)imidazole)Ru(II) Complexes and Trimeric Cyclophanes in Water

Shape-switchable cyclophane hosts allow the controlled capture and release of reactive polypyridineRu(ii) complexes in water. This gives rise to a network of host–guest binding, acid–base reactions in ground and excited states, and chemical redox interconversions. In the case of (2-(2′-pyridyl)imidazole)Ru(ii) complexes, several molecular logic gate arrays of varying complexity emerge as a result. Cyclophane-induced ‘off–on’ switching of luminescence in neutral solution is found to originate from two features of these aromatic hosts: enhancement of radiative decay by the polarizable host and the suppression of nonradiative decay involving deprotonation by reducing the water content within the deep host cavity. These are examples of nanometric coordination chemistry/physics being controlled by inclusion in an open box. The aromatic units of the macrocycle are also responsible for the shape-switching mechanism of wall collapse/erection.

Transactions of a polypyridineRu(ii) complex with photons, protons and shape-switchable hosts show several types of molecular logic.

Single-sensing-unit 3D quantum dot sensors for the identification and differentiation of mucopolysaccharides

Principle of Mn–ZnS⁺ QDs 3D sensors used to identify and differentiate MPSs.

Cancer Cell Discrimination Using Host-Guest "Doubled" Arrays

We report a nanosensor that uses cell lysates to rapidly profile the tumorigenicity of cancer cells. This sensing platform uses host-guest interactions between cucurbit[7]uril and the cationic headgroup of a gold nanoparticle to non-covalently modify the binding of three fluorescent proteins of a multi-channel sensor in situ. This approach doubles the number of output channels to six, providing single-well identification of cell lysates with 100% accuracy. Significantly, this classification could be extended beyond the training set, determining the invasiveness of novel cell lines. The unique fingerprint of these cell lysates required minimal sample quantity (200 ng, ∼1000 cells), making the methodology compatible with microbiopsy technology.

A two-dimensional sensing device based on manganese doped zinc sulfide quantum dots for discrimination and identification of common sugars

A Mn-doped ZnS QD 2D sensor for identification and separation of common sugars.

Highly selective and sensitive colorimetric chemosensors for Hg2+ based on novel diaminomaleonitrile derivatives

Five novel soluble chemosensors in EtOH/H₂O based on Schiff-base diaminomaleonitrile derivatives which were modified by different aromatic functional moieties have been synthesized.

A triple-dimensional sensing chip for discrimination of eight antioxidants based on quantum dots and graphene

A triple-dimensional sensing chip is developed based on simultaneous utilization of fluorescence (FL), electrochemical (ECL) and mass-sensitivity (MS) properties of a novel nanocomposites. The sensing nanomaterial is composed of CdSe/ZnS quantum dots (QDs) and graphene through a one-pot room-temperature reverse microemulsion polymerization. Here, full integration of QDs and graphene on one chip provides triple-dimensional sensing signals. It enables quick and accurate discrimination of eight analytes in a "lab-on-a-nanomaterial" approach and notably improves the overall sensor performance. Unknown samples randomly taken from the training set at concentrations of 0.7 μM are successfully classified by principal component analysis (PCA) with accuracies of 92.5%, compared with the high performance liquid chromatography (HPLC) method. We further apply it to discriminate eight antioxidants from real oil samples, and explore the mechanism.

Bis(acetylacetonato)bis(pyrazolato)ruthenate(iii) as a redox-active scorpionate ligand

The potential of a new anionic octahedral metal complex [Ru(III)(acac)2(pz)2](-) ((-)) (pzH = pyrazole) as a ligand with a scorpionate coordination behaviour like tris(pyrazolyl)borate (tp) and reversible redox activity is presented. Trinuclear metal complexes, [Ru(III)2Zn(II)(acac)4(pz)4] () and [Ru(II)Ru(III)2(acac)4(pz)4] (), were each synthesized by the reaction of ZnCl2 or Ru3(CO)12 with [Ru(III)(acac)2(pz)(pzH)] (H) that is in situ deprotonated and acts as a precursor of (-). Single-crystal X-ray diffraction studies clarified that (-) acts as a scorpionate ligand; two (-) units in and one unit in function as bidentate ligands with two pyrazolates as pincers, while another (-) unit in functions as a tridentate ligand with one oxygen atom as a tail in addition to the two pyrazolate pincers. Moreover, and showed reversible multi-stage redox behaviours based on the Ru(II)/Ru(III) and Ru(III)/Ru(IV) couples of the (-) units in the cyclic voltammetry (CV) measurements. Based on the X-ray, IR, and CV measurements and the comparison with other Ru(ii) complexes with tp derivatives, the (-) unit was found to act as a redox-active scorpionate with electron withdrawing properties compared to the tp.

Aminophenylboronic-acid-conjugated polyacrylic acid-Mn-doped ZnS quantum dot for highly sensitive discrimination of glycoproteins

Discrimination of glycoproteins with different glycans is a significant but difficult issue. We presented here a new strategy for strengthening the discrimination of glycoproteins by introducing a new signaling channel, fluorescence polarization (FP), into a "single probe with three signaling channels" sensor array. The single probe was aminophenylboronic-acid-conjugated poly(acrylic acid)-Mn-doped ZnS quantum dots, and the three signaling channels were FP, room temperature phosphorescence and light scattering. Ten glycoproteins, including ovalbumin, fibrinogen, transferrin, horseradish peroxidase, vascular endothelial growth factor, immunoglobulin G, avidin, hyaluronidase, cellulase R-10, and glucose oxidase, were involved for evaluating the discriminating capability. The introduction of the FP signaling channel improved the discriminating power of the sensor array, so that the 10 glycoproteins at 0.15 μM could be well discriminated both in PBS buffer and in the presence of human serum sample. The identification accuracy of the unknown samples was 96.25% (77 out of 80) at the 0.15 μM level and 97.50% (78 out of 80) at the 0.2 μM level. The integration of the signaling patterns with different responsive principles was demonstrated as the promising way to enhance the discrimination power of the single-probe-based sensor arrays.

Integration of the 1,2,3-triazole "click" motif as a potent signalling element in metal ion responsive fluorescent probes

In a systematic approach we synthesized a new series of fluorescent probes incorporating donor-acceptor (D-A) substituted 1,2,3-triazoles as conjugative π-linkers between the alkali metal ion receptor N-phenylaza-[18]crown-6 and different fluorophoric groups with different electron-acceptor properties (4-naphthalimide, meso-phenyl-BODIPY and 9-anthracene) and investigated their performance in organic and aqueous environments (physiological conditions). In the charge-transfer (CT) type probes 1, 2 and 7, the fluorescence is almost completely quenched by intramolecular CT (ICT) processes involving charge-separated states. In the presence of Na(+) and K(+) ICT is interrupted, which resulted in a lighting-up of the fluorescence in acetonitrile. Among the investigated fluoroionophores, compound 7, which contains a 9-anthracenyl moiety as the electron-accepting fluorophore, is the only probe which retains light-up features in water and works as a highly K(+)/Na(+)-selective probe under simulated physiological conditions. Virtually decoupled BODIPY-based 6 and photoinduced electron transfer (PET) type probes 3-5, where the 10-substituted anthracen-9-yl fluorophores are connected to the 1,2,3-triazole through a methylene spacer, show strong ion-induced fluorescence enhancement in acetonitrile, but not under physiological conditions. Electrochemical studies and theoretical calculations were used to assess and support the underlying mechanisms for the new ICT and PET 1,2,3-triazole fluoroionophores.

Enzyme-based multiplexer and demultiplexer

A digital 2-to-1 multiplexer and a 1-to-2 demultiplexer were mimicked by biocatalytic reactions involving concerted operation of several enzymes. Using glucose oxidase (GOx) and laccase (Lac) as the data input signals and variable pH as the addressing signal, ferrocyanide oxidation in the output channel was selectively activated by one from two inputs, thus mimicking the multiplexer operation. A demultiplexer based on the enzyme system composed of GOx, glucose dehydrogenase (GDH) and horseradish peroxidase (HRP) allowed selective activation of different output channels (oxidation of ferrocyanide or reduction of NAD(+)) by the glucose input. The selection of the output channel was controlled by the addressing input of NAD(+). The designed systems represent important novel components of future branched enzyme networks processing biochemical signals for biosensing and bioactuating.

Multi-channel receptors based on thiopyrylium functionalised with macrocyclic receptors for the recognition of transition metal cations and anions

We report herein the synthesis and characterization of a family of ligands containing different cation binding sites covalently connected to a thiopyrylium signalling reporter. The receptors L1-L6 are able to signal the presence of certain metal cations via three different channels; i.e. electrochemically, fluorogenically and chromogenically. An acetonitrile solution of L1-L6 shows a bright blue colour due to a charge-transfer band in the 575-585 nm region. The colour variation in acetonitrile of L1-L6 in the presence of the metal cations Ag+, Cd2+, Cu2+, Fe3+, Hg2+, Ni2+, Pb2+ and Zn2+ has been studied. A selective hypsochromic shift of the blue band was found for the systems L4-Pb2+ and L5-Hg2+. Additionally, L1-L6 are poorly fluorescent but coordination with certain metal cations induces an enhancement of the fluorescence at ca 500 nm. For instance, the presence of Cu2+ and Fe3+ induced a remarkable 42-fold and 45-fold enhancement in the emission intensity of L1 centred at 500 nm, respectively. Also remarkable was the 18-fold enhancement observed for L4 and L5 in the presence of Fe3+ and Cu2+, respectively. The electrochemical behaviour of receptors L1-L6 was studied in acetonitrile using platinum as a working electrode and [Bu4N][BF4] as a supporting electrolyte. This family of receptors showed a one-electron reversible redox process at ca. -0.46 V versus sce attributed to the reduction of the thiopyrylium group. A moderate anodic shift in the presence of certain metal cations was observed. The effect in the UV-visible spectra of acetonitrile solutions of receptor L1-L6 in the presence of anions was also studied. A remarkable bleaching was found in the presence of cyanide.

Chemical Approaches to Molecular Logic Elements for Addition and Subtraction

Molecular and supramolecular logic gates are candidates for computation at the nanoscale level. Nowadays all common logic operations can be mimicked with molecular devices based on chemical approaches. One step further towards molecular systems with increased logic capabilities is the addition or subtraction of binary digits. This Minireview describes recent developments to attain this goal, including bioinspired systems based on DNA and enzymes. Furthermore, chemical molecular logic gates are discussed and compared critically with regard to alternative concepts.