Masterproject - Novel Chemistry

Supervisor: Associate professor Björn Martin Valldor

The combination of two (or more) anions, e.g. S^2- and O^2- in one compound to form a sulfide oxide, is a relatively new strategy to synthesize novel materials with huge potential for finding exotic properties. For example, if S^2- and O^2- coordinate to the same cation, a so-called heteroleptic coordination, the cation will be pushed away from the coordination centre, because the two anions are different in sizes. In a similar situation with two differently charged anions, like O^2- and Cl^-, the cation (as forced by Nature) might behave even more “irrational”. The situations are extremely rare so far and this project would aim to find more compounds with two (or more) different anions in a crystal structure.

The novel coordination possibilities can result in many different and interesting properties, such as magnetic, optical, and electrical properties, much depending on what cations are involved.

The ultimate goal is to find something that was never seen before, but also to get further understanding of the trinity: crystal structure – chemical composition – physical properties.

To synthesize the mixed-anion compounds, we will use an exact method: the closed system reaction. All constituents (chemicals) you place in the reaction should end up somewhere! And nothing unknown comes in. By this technique, we can force Nature to adapt to our suggests – if there is a possibility for a mixed-anion compound, we will see the way, and then follow it. You will perform almost holistic research, which can end up with anything from a novel compound, a new crystal structure, all the way to a (for example) new superconductor.

To the most important analyses, you will perform x-ray diffraction – on single crystals and powder – and evaluate those data with great accuracy (and several different software packages). From those data we can simulate the atomic arrangements that describe the whole crystals, including ordering of anions and rare coordinations. From the crystal structure simulation, bond distances and angles are of revealed and of essence to get further understanding for the inorganic chemist. Electron microscopy investigations will reveal the true composition of samples, apart from showing the morphology of the crystallites. With each novel compound, we need to measure some “global” properties, like magnetism, to complete the trinity.

Figure: Two anions (red and yellow balls, respectively) can cause strange (heteroleptic) coordination of a cation (in the centre), as compared to the homoleptic coordination found in a single-anion lattice.