(Pro2H+)2(TCNQ.−)2⋅TCNQ: An Amino Acid Derived Semiconductor

Solvent-, Cation- and Anion-Induced Structure Variations in Manganese-Based TCNQF4 Complexes: Synthesis, Crystal Structures, Electrochemistry and Their Catalytic Properties

The reaction of Mn(BF₄ )₂ ⋅x H₂ O with (Pr₄ N)₂ TCNQF₄ (TCNQF₄ =2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) in a mixture of CH₃ OH/CH₂ Cl₂ gives a 2:3 stoichiometric complex of (Pr₄ N)₂ [Mn₂ (TCNQF₄ )₃ (CH₃ OH)₂ ] (1). If the solvent system used for the crystallisation of 1 is changed to CH₃ OH/DMF, then a different product, [Mn(TCNQF₄ )(DMF)₂ ]⋅(CH₃ OH)₂ (2), is obtained. The use of Li₂ TCNQF₄ instead of (Pr₄ N)₂ TCNQF₄ leads to the generation of [Mn₂ (TCNQF₄ )₂ (DMF)₄ ]⋅3 DMF (3). An unexpected mixed oxidation state network with a composition of [Mn^II ₄ Mn^III ₁₆ O₁₀ (OH)₆ (OCH₃ )₂₄ (TCNQF₄ )₂ ](NO₃ )₂ ⋅24 CH₃ OH (4), is formed if Mn(NO₃ )₂ ⋅x H₂ O is used in place of Mn(BF₄ )₂ ⋅x H₂ O in the reaction that leads to the formation of 3. Compounds 1-3 have been characterised by X-ray crystallography; FTIR, Raman and UV/Vis spectroscopy; and electrochemistry. Compound 4 has only been analysed by X-ray crystallography and vibrational spectroscopy (Raman, FTIR), owing to rapid deterioration of the compound upon exposure to air. These results indicate that relatively minor changes in reaction conditions have the potential to yield products with vastly different structures. Compound 1 adopts an anionic 2D network with unusual π-stacked dimers of the TCNQF₄ ^2- dianion, whereas 2 and 3 are composed of similar neutral sheets of [Mn(TCNQF₄ )(DMF)₂ ]. Interestingly, the solvent has a significant influence on the stacking of the sheets in the structures of 2 and 3. In compound 4, clusters with a composition of [Mn^II ₄ Mn^III ₁₆ O₁₀ (OH)₆ (OCH₃ )₂₄ (CH₃ OH)₄ ]⁶⁺ serve as eight-connecting nodes, whereas TCNQF₄ ^2- ligands act as four-connecting nodes in a 3D network that has the same topology as fluorite. Compound 3 exhibits an exceptionally high super-catalytic activity for the electron-transfer reaction between ferricyanide and thiosulfate ions in aqueous media.

Exploring polymorphism and stoichiometric diversity in naproxen/proline cocrystals

This work studies a multitude of cocrystals obtained by combining chiral and/or racemic naproxen and proline, 17 in total.

Solvent-tuned charge-transfer properties of chiral Pt(ii) complex and TCNQ˙− anion adducts

A new pair of adducts comprising one chiral Pt(ii) complex cation, [Pt((−)-L₁)(Dmpi)]⁺ ((−)-1) or [Pt((+)-L₁)(Dmpi)]⁺ ((+)-1) [(−)-L₁ = (−)-4,5-pinene-6′-phenyl-2,2′-bipyridine, (+)-L₁ = (+)-4,5-pinene-6′-phenyl-2,2′-bipyridine, Dmpi = 2,6-dimethylphenylisocyanide], together with one TCNQ˙⁻ anion have been obtained, and the structures have been confirmed via single-crystal X-ray crystallography and infrared (IR) spectroscopy. The chiral Pt(ii) cation and TCNQ˙⁻ anion are dissociated in MeOH solution, while charge transfer adducts are formed in H₂O solution, leading to perturbation of the electronic structure and alteration of the chiral environment, as evidenced by the differences in the UV-vis absorption and electronic circular dichroism spectra. The solvent-tuned charge-transfer properties also have been validated through emission and resonance light scattering spectra. The interesting findings may have potential applications in the development of black absorbers and wide band gap semiconductors.

A new couple of charge transfer adducts comprising of one chiral Pt(ii) complex cation together with one TCNQ˙⁻ anion have been prepared, and solvent-induced variances of absorption, luminescence as well as chiral spectra have been investigated.

Three alkaline-earth metal complexes with 3D networks constructed from a 7,7,8,8-tetracyanoquinodimethane ligand: synthesis, structure and electrochemical properties

Three new 7,7,8,8-tetracyanoquinodimethane (TCNQ) alkaline-earth metal complexes, namely {[M2(TCNQ)3(H2O)6]·TCNQ}n (M = Ca (1), Sr (2) and Ba (3)) have been synthesized by salt elimination reactions. X-ray crystallographic analysis reveals that complexes 1, 2 and 3 are isomorphic featuring a unique 3D structure. Cyclic and differential pulse voltammograms for complexes 1-3 show a reversible one-electron oxidation and a reversible one-electron reduction within the electrochemical window of CH3CN. Their electrochemical HOMO-LUMO gap and reversibility are examined.