An Old Crystallization Technique as a Fast, Facile, and Adaptable Method for Obtaining Single Crystals of Unstable "Li2TCNQF4" and New Compounds of TCNQ or TCNQF4: Syntheses, Crystal Structures, and Magnetic Properties

Detailed structural information is essential for understanding the properties of TCNQ and TCNQF₄ compounds (TCNQ = 7,7,8,8-tetracyanoquinodimethane; TCNQF₄ = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane). The ineludible requirement of obtaining crystals of a size and quality sufficient to yield a successful X-ray diffraction analysis has been challenging to satisfy because of the instability of many of these compounds in solution. Crystals of two new complexes of TCNQ, [trans-M(2ampy)₂(TCNQ)₂] [M = Ni (1), Zn (2); 2ampy = 2-aminomethylpyridine], as well as unstable [Li₂(TCNQF₄)(CH₃CN)₄]·CH₃CN (3), can be prepared in minutes by a horizontal diffusion technique and can be harvested easily for X-ray structural studies. Compound 3, previously described as "Li₂TCNQF₄," forms a one-dimensional (1D) ribbon. Compounds 1 and 2 can also be obtained as microcrystalline solids from methanolic solutions of MCl₂/LiTCNQ/2ampy. Their variable-temperature magnetic studies confirmed a contribution of strongly antiferromagnetically coupled pairs of TCNQ^•- anion radicals at higher temperatures with exchange coupling J/k_B = -1206 K and J/k_B = -1369 K for 1 and 2, respectively, estimated using a spin dimer model. The presence of magnetically active anisotropic Ni(II) atoms with S = 1 in 1 was confirmed, and the magnetic behavior of 1, representing an infinite chain of alternating S = 1 sites and S = 1/2 dimers, was described by a spin-ring model suggesting ferromagnetic exchange coupling between Ni(II) sites and anion radicals.

Development of lab-on-chip biosensor for the detection of toxic heavy metals: A review

Recently, a decrease in water availability and quality has been raised due to rapid industrialization, unsustainable agricultural activities and anthropogenic activities. Heavy metals are considered significant pollutants in the water environment, cause environmental hazards and health effects to humans. For monitoring water contaminants utilized different conventional techniques. Still, they have some drawbacks, such as cost expensive, ecological issues, and processing time, requiring technicians and researchers to operate them effectively. Biosensors have become reasonable devices for screening and identifying environmental contaminants because of their different benefits contrasted with other detecting techniques. This review summarizes the toxic effect of heavy metal and their source, occurrence. A detailed discussion is provided on the heavy metal recognition materials for detecting heavy metals in wastewater. Lab on chip (LOC) is an emerging micro-electrical mechanical system (MEMS) device that intakes liquid and makes it move through the micro-channels, to accomplish fast, cost-effective and profoundly sensitive analysis with significant yield. LOC also provided a discussion on numerous laboratory functions on a single platform. This article attempts to discuss the detection of heavy metals using lab on a chip by suitable recognition materials. Further, the design and fabrication mechanism and their recognition abilities of LOC were also reviewed. The review mainly focuses on the application of LOC biosensors, pros, and cons, and suggests a roadmap towards future development to enhance the practical use in pollutant monitoring.

Architectural diversity in the solid-state behaviour of crown ether and [2.2.2]-cryptand complexes of K+TCNQ˙− salts

Ionophore complexes of K(TCNQ˙−)(TCNQ0)n adopt a variety of stacking motifs such as wave-like infinite TCNQ columns separated by K+-cryptates (left) and K+-π-dimerised cation complexes separated by infinite slipped TCNQ stacks (right).

Dynamics of proton, ion, molecule, and crystal lattice in functional molecular assemblies

Dynamic molecular processes, such as short- or long-range proton (H⁺) and ion (M⁺) motions, and molecular rotations in electrical conducting and magnetic molecular assemblies enable the fabrication of electron-H⁺ (or M⁺) coupling systems, while crystal lattice dynamics and molecular conformation changes in hydrogen-bonded molecular crystals have been utilised in external stimuli responsive reversible gas-induced gate opening and molecular adsorption/desorption behavior. These dynamics of the polar structural units are responsible for the dielectric measurements. The H⁺ dynamics are formed from ferroelectrics and H⁺ conductors, while the dynamic M⁺ motions of Li⁺ and Na⁺ involve ionic conductors and coupling to the conduction electrons. In n-type organic semiconductors, the crystal lattices are modulated by replacing M⁺ cations, with cations such as Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺. The use of polar rotator or inversion structures such as alkyl amides, m-fluoroanilinium cations, and bowl-shaped trithiasumanene π-cores enables the formation of ferroelectric molecular assemblies. The host-guest molecular systems of ESIPT fluorescent chromic molecules showed interesting molecular sensing properties using various bases, where the dynamic transformation of the crystal lattice and the molecular conformational change were coupled to each other.

Novel TCNQ-stacking motifs in (12-crown-4)-complexes of alkali metal TCNQ salts

An unusual crossed dimer motif is present in the solid state in the infinite TCNQ˙− columns of the bis-12-crown-4 complexes of Li and NaTCNQ.