Structures and properties of multifunctional molecular materials: combining chirality and conductivity

Lopez, J.R., 2017. Structures and properties of multifunctional molecular materials: combining chirality and conductivity. PhD, Nottingham Trent University.

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Abstract

The objective of this thesis is to investigate the influence of chirality upon conducting materials through the synthesis of charge-transfer salts by diffusion or electrocrystallisation of enantiopure/racemic donor molecules and anions.

This thesis presents the characterisation of new charge-transfer salts from two new donor molecules: BHM-EDT-TTF and BHM-BEDT-TTF. BHM-EDT-TTF has produced a family of 1:1 semiconductors with tetrahedral and octahedral anions BF4, ClO4 and PF6. The room temperature resistivities and activation energies are similar for all enantiopure salts but slightly different for their racemic/meso forms. The racemic donor BHM-BEDT-TTF forms a semiconducting 2:1 salt with chloride, and an insulating 1:1 salt with TCNQ which has an interesting packing arrangement in that the donors are segregated into stacks consisting of only a single enantiomer in the mode SS:SS:RR:RR:SS:SS.

The first charge-transfer salts have been synthesised and characterised from BEDT-TTF with racemic spiroboronate anions. Five salts of BEDT-TTF with either B(malate)2, B(mandelate)2, or B(glycolate)2 show a variety of novel packing arrangements and conducting properties. These salts are also the first examples of preferential diastereomeric induction within the electrocrystallisation environment. Using spiroboronate anions with enantiopure ligands has also produced crystals having a macromolecular helical morphology.

The first examples of charge-transfer salts containing racemic and chiral lanthanide anions are reported including the spontaneous resolution of the racemic [Gd(dipicolinato)3]3- anion in the presence of BEDT-TTF and bromobenzene to produce a chiral, paramagnetic, semiconductor. A new molecular superconductor, β”-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3].18-crown-6, has been synthesised. This is the 2D superconductor with the widest gap between conducting layers where only a single donor packing motif is present (β”). Superconducting critical temperatures at ambient pressure observed by electrical transport and magnetic measurements are 4.0-4.9 and 2.5 K, respectively. The strong 2D nature of this system strongly suggests that the superconducting transition is a Kosterlitz-Thouless transition.

Item Type: Thesis
Creators: Lopez, J.R.
Date: August 2017
Rights: This work is the intellectual property of the author, and may also be owned by the research sponsor(s) and/ or Nottingham Trent University. You may copy up to 5 % of this work for private study, or personal, non-commercial research. Any re-use of the information contained within this document should be fully referenced, quoting the author, title, university, degree level and pagination. Queries or requests for any other use, or if a more substantial copy is required, should be directed in the first instance to the author.
Divisions: Schools > School of Science and Technology
Depositing User: Jill Tomkinson
Date Added: 10 Apr 2019 11:14
Last Modified: 10 Apr 2019 11:14
URI: http://irep.ntu.ac.uk/id/eprint/36221

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