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).

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.

Crown ether alkali metal TCNQ complexes revisited – the impact of smaller cation complexes on their solid-state architecture and properties

Water molecules play a key structure-organising role in the crystallisation of 15-crown-5 complexes of lithium and sodium TCNQ in the presence of excess TCNQ⁰.

Spectroscopic investigation of the donor-acceptor interaction between o-phenylenediamine and tetracyanoethylene in dichloromethane

The interaction between the electron donor o-phenylenediamine (o-phendn) and the pi-acceptor tetracyanoethylene (TCNE) has been investigated spectrophotometrically in dichloromethane at 25 degrees C. The results indicate that the reaction proceeds via two major steps. The formation of the 1:2 charge-transfer complex [(o-phendn)2, (TCNE)4] in which two o-phenylenediamine molecules undergoes slow N-substitution by one TCNE forming the final reaction product 2,2-di-o-aminoaniline-1,1-dicyanoethylene and 2HCN molecules. The reaction was studied using electronic, infrared, photometric titration and cyclic voltametric measurements. A general mechanism for the reactions is proposed.

The Origin of the Surprising Stabilities of Highly Charged Self-Assembled Polymetallic Complexes in Solution

The thermodynamics of electrochemical and complexation reactions involving the heterobimetallic triple-stranded helicates [MA(L5)3]n+ (M=Ru(II), Cr(III) and A=Ca(II), Lu(III)) reveal that solvation processes mask intramolecular intermetallic repulsions in solution, a phenomenon at the origin of the surprising stabilities of highly charged self-assembled polymetallic complexes in solution. A judicious combination of Born-Haber cycles and the Born equation restores the expected electrostatic trend in the gas phase, in which intermetallic interactions can be simply modeled using a standard Coulombic approach. Semiquantitative estimation and prediction of the contribution of the intermetallic repulsion to the total free energy of the formation of discrete polymetallic assemblies in solution become thus accessible. This point is crucial for programming stable metallosupramolecular architectures in solution.

Ionic channel structures in [(M+)x([18]crown-6)][Ni(dmit)2]2 molecular conductors

The [(M+)x[18]crown-6)] supramolecular cations (SC+), in which M+ and [18]crown-6 are alkali metal ions (M+ = Li+, Na+, and Cs+) and 1,4,7,10,13,16-hexaoxacyclooctadecane, respectively, form ionic channel structures through the regular stacks of [18]crown-6 in [Ni(dmit)2]-based molecular conductors (dmit2+ = 2-thioxo-1,3-dithiole-4,5-dithiolate). In addition to the [Ni(dmit)2] salts that have the ionic channel structures (these salts are abbreviated as type I salts), Li+ and Na+ form dimerized [(M+)2([18]crown-6)2] units in the crystals (type II salts). The K+ and Rb+ are coordinated tightly into the [18]crown-6 cavity to form typical disk-shape SC+ units in the corresponding [Ni(dmit)2] salts (type III salts). The type I, II, and III salts have typical stoichiometries of [(M+)x([18]crown-6)][Ni(dmit)2]2, [(M+)([18]crown-6)(H2O)x(CH3CN)(1.5 - x)][Ni(dmit)2]3 (x = 1 for Li+ or 0.5 for Na+), and [M+([18]crown-6)][Ni(dmit)2]3, respectively: the salts of the same type are isostructural. In agreement with the trimer structures of [Ni(dmit)2] in the type II and III salts, they exhibit semiconducting behavior with electrical conductivities at 300 K (sigma(300 K)) of 0.01-0.1 S cm(-1). Type I salts contain a regular stack of partially oxidized [Ni(dmit)2] units, which form a quasi one-dimensional metallic band within the tight-binding approximation regime. The electrical conductivities at 300 K are 10-30 S cm(-1), and an almost temperature-independent conductivity was observed at higher temperatures. However, the one-dimensional electronic structures in these salts are strongly influenced by the static and dynamic structures of the coexisting ionic channel. The Na+ salt is a semiconductor, whose magnetic behavior is described by the disordered one-dimensional antiferromagnetic chain. On the other hand, the Cs+ salt is a exhibits metallic properties with 2 kF instability at room temperature. The Li+ salt shows a gradual transition from the high-temperature metallic phase to the low-temperature one-dimensional antiferromagnetic semiconductor phase, which was associated with the freezing of Li+ motion at lower temperatures. The preferential crystallization of type I salts was possible by controlling the equilibrium constant (Kc) of the complex formation between M+ ions and the [18]crown-6 molecule. The ionic channel structures were obtained when the KC was low in the electrocrystallization solution, while type II or III salts were formed in the high Kc region.