Alkylated Trimethylene-Bridged Bis(p-Phenylenediamines)

para-Phenylenediamine Dimer as a Redox-Active Guest for Supramolecular Systems

Redox-active components are highly valuable in the construction of molecular devices. We combined two p-phenylenediamines (p-PDA) with a biphenyl (BiPhe) unit to prepare a supramolecular guest 4 consisting of three binding sites for cucurbit[7/8]uril (CBn) and/or cyclodextrins (CD). Supramolecular properties of 4 were investigated using NMR, UV-vis, mass spectrometry and isothermal titration calorimetry. Our analysis revealed that 4 forms higher-order host-guest complexes, wherein a CD unit occupies the central BiPhe site, secured by two CBn units at the terminal p-PDA sites. Additionally, 1 : 1 complexes with α-CD and β-CD, a 1 : 2 complex with γ-CD and 2 : 1 complexes with CB7 and CB8 were identified. Through UV-vis and cyclic voltammetry, redox processes leading to the formation of a stable, deep blue dication diradical of 4 are elucidated. Furthermore, it is demonstrated that CB7 selectively protects oxidised 4 from reduction in the presence of a reducing agent. The supramolecular and redox properties of the structural motif represented by 4 render it an interesting candidate for the construction of supramolecular devices.

Structures and Oxidation Properties of Phenylene-Bridged Diazacycloalkanes: Ring Size Effects on Structures and Properties

Phenylenediamine derivatives have been investigated as functional molecules because of their characteristic oxidation properties. In this study, phenylene-bridged diazacycloalkanes, that is, C10, C12, and C14, in which numbers indicate the lengths of a side chain, were synthesized, and the effects of the macroring size on their structures and oxidation properties were investigated. X-ray crystallography revealed that the structures around the nitrogen atoms were remarkably dependent on the chain lengths. The benzene plane of C10 is arranged almost perpendicular to the macroring to avoid steric contact. However, the benzene plane of C14 and alkyl frame were co-planar. Stabilization resulting from conjugation was comparable to destabilization caused by macroring strain according to DFT calculations. Structural differences between C10 and C14 caused changes in the NMR chemical shifts of the inner methylene protons and first oxidation potentials in solution. Notably, the properties of C12 can be analyzed as those of distributed structures, which is of interest with respect to exploiting the metastable structure of the molecules. The observed relationships between the steric structures and properties can facilitate the design of functional molecules containing phenylenediamine moieties.

Novel silver-phosphine coordination polymers incorporating a Wurster's blue - like radical cation with enhanced photoelectric properties

Tetraphosphine ligand dpppda reacts with AgNO3 to generate two 1D coordination polymers containing cubic and chair-like [Ag4(NO3)4] clusters. ESR spectroscopy supported by DFT calculations indicated the presence of dpppda˙+, a Wurster's blue - like radical cation formed by intramolecular ligand-to-metal charge transfer (LMCT). This LMCT results in higher AgI → Ag0 potentials and good photocurrent responses.

A mononuclear iron carbonyl complex [Fe(μ-bdt)(CO)2(PTA)2] with bulky phosphine ligands: a model for the [FeFe] hydrogenase enzyme active site with an inverted redox potential

A mononuclear hexa-coordinated iron carbonyl complex [Fe(μ-bdt)(CO)₂(PTA)₂] 1 (bdt = 1,2-benzenedithiolate; PTA = 1,3,5-triaza-7-phosphaadamantane) with two bulky phosphine ligands in the trans position was synthesized and characterized by X-ray structural analysis coulometry data, FTIR, electrochemistry and electronic structure calculations. The complex undergoes a facilitated two-electron reduction 1/1^2- and shows an inverted one-electron reduction for 1/1^- at higher potentials. Electrochemical investigations of 1 are compared to the closely related [Fe(bdt)(CO)₂(PMe₃)₂] compound. A mechanistic suggestion for the hydrogen evolution reaction upon proton reduction from acid media is derived. The stability of 1 in both weak and strong acids is monitored by cyclic voltammetry.

Polymers for electronics and spintronics

This critical review is devoted to semiconducting and high spin polymers which are of great scientific interest in view of further development of the organic electronics and the emerging organic spintronic fields. Diversified synthetic strategies are discussed in detail leading to high molecular mass compounds showing appropriate redox (ionization potential (IP), electron affinity (EA)), electronic (charge carrier mobility, conductivity), optoelectronic (electroluminescence, photoconductivity) and magnetic (magnetization, ferromagnetic spin interactions) properties and used as active components of devices such as n- and p-channel field effect transistors, ambipolar light emitting transistors, light emitting diodes, photovoltaic cells, photodiodes, magnetic photoswitches, etc. Solution processing procedures developed with the goal of depositing highly ordered and oriented films of these polymers are also described. This is completed by the description of principal methods that are used for characterizing these macromolecular compounds both in solution and in the solid state. These involve various spectroscopic methods (UV-vis-NIR, UPS, pulse EPR), electrochemistry and spectroelectrochemistry, magnetic measurements (SQUID), and structural and morphological investigations (X-ray diffraction, STM, AFM). Finally, four classes of polymers are discussed in detail with special emphasis on the results obtained in the past three years: (i) high IP, (ii) high |EA|, (iii) low band gap and (iv) high spin ones.