A 3D antiferromagnetic ground state in a quasi-1D π-stacked charge-transfer system

With the rising interest in organic based materials for spintronic and multiferroic applications it is important to fully understand their electrical and magnetic properties and to identify correlations between their structural and physical attributes. One material that still holds some ambiguity is triethylammonium bis-7,7,8,8-tetracyanoquinodimethane (TEA(TCNQ)2). This charge transfer compound has one electron delocalised across two TCNQ molecules along quasi-1D stacks. Previous work has shown that there is magneto-electrical coupling associated with the magnetic transition at ∼120 K, however the magnetism and magnetic ground-state are not well understood. Within this manuscript we provide evidence for a long range magnetic order that is 3D in nature

No evidence for room temperature ferromagnetism in the high temperature metal-organic material: Ni2TCNQ

The search for ferromagnetic organic-based compounds has been a particular challenge to both chemists and physicists over the past few decades. The synthesis of the Ni2A, where A is an organic acceptor; tetracyanoethene (TCNE), 3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) or 7,7,8,8-tetracyanoquinodimethane (TCNQ) (Jain et al 2007 Nature 445 291), was reported to be a great advancement with claims that the ferromagnetism persisted to well above room temperature. There were, however some substantial flaws in the methodology associated with the synthesis and physical characterisation. Our work solely studies the Ni2TCNQ compound where we find no evidence for the existence of inherent ferromagnetism within the material that was reported in the original paper. Instead, we find that the magnetism is due to superparamagnetic nickel nanoparticles embedded in an amorphous matrix. It is hoped that our work will also show that one must be careful when using Ni(COD)2 as a precursor in the synthesis of magnetic materials and that the usefulness of the reported synthetic method is extremely limited

Orientation and solvatochromism of dyes in liquid crystals.

The orientation and solvatochromism of some dye molecules in a liquid crystal have been investigated. Interactions with the host and the structure of the dye molecule affect the macroscopic alignment of dichroic dye molecules in a liquid crystal: It was observed that some dye molecules show a large bathochromic shift of their absorption maxima in the liquid crystal host relative to the situation in isotropic solvents. It is suggested that this is due to the occurrence of a much weaker reaction field in the anisotropic, rigid host. These dye molecules show little or no apparent order in the anisotropic host despite the observation of a reduction in the electro optic switching time when the dye is present. The highest degree of macroscopic alignment was observed for a merocyanine compound, which showed the smallest solvatochromic shift in the liquid crystal host. These results are discussed in terms of the steric, dipolar and hydrogen bond interactions between the guest and the host