MNF-chem5008

Final Year Project for Exchange Students in Chemistry


Within this project the following position is available:


Title of the project

Synthesis, Structures and Physical Properties of Coordination Polymers that shows Cooperative Magnetic Phenomena


Introduction

Recently, investigations on the synthesis of new coordination polymers, metal organic frameworks or inorganic organic hbride compounds has become of increasing interest. This also includes materials that shows cooperatie magnetic exchange interactions. In this context we are especially interested in coordination polymers based on transition metal thiocyanates and neutral N-donor co-ligands.  To generate cooperative magnetic phenomena compounds must be prepared in which the transition metal cations are linked by µ-1,3-bridging thiocyanato anions into chains. In several cases these compounds can directly be prepared by the reaction of the reactands in solution but in other cases only compounds are available by this route, in which the thiocyanato anions are N-terminal bonded. In this case the terminal bonded coordination compounds can be transformed into the desired µ-1,3-bridiging compounds by thermal decomposition, in which a part of the neutral N-donor co-ligands are removed.

Magnetic measurements reveal that dependent on the metal cation different cooperative phenomena are observed like e.g. antiferro-, ferro- or metamagnetism. For some of these compounds based on Co(II) or Fe(II) cations we have observed single chain magnetic behavior which is a very rare phenomena. Such compounds have some potential for future application in high-density storage materials.

Based on these findings we have started a project on systematic investigations on the influence of the structure and chemical composition on the magnetic properties of such compounds. Investigations which are absolutely needed for a deeper understanding of these phenomena and for any optimization of such materials. The exchange project will be a part of this more general project.


Supervisor

Prof. Dr. Christian Näther


Requirements

Interest in solid state and coordination chemistry


Experimental tasks within this project

  • Literature search
  • Structure search in the Cambridge Structural Database (CSD)
  • Preparation of the coordination compounds from the liquid phase using different stoichiometric amounts of the reactands
  • Characterization of these compounds by C,H.N,S analysis, IR spectroscopy and XRPD
  • If only compounds with N-terminal bonded thiocyanato anions are present, they must be investigated for their thermal properties by DTA-TG-MS and DSC measurements in order to prepare the desired µ-1,3-bridging compounds by thermal decomposition
  • Preparation of single crystals of all compounds for structure determination (if possible)
  • Structure determination by single crystal X-ray analysis
  • Investigations on the identity and homogeneity of all compounds by XRPD
  • Magnetic measurements if the compounds are obtained as phase pure materials


Methods that will be used within this project

  • Single crystal X-ray diffraction for the determination of the 3D structures (Data measurement is performed as service, the structure will be solved and refined by the student)
  • X-ray powder diffraction (XRPD) for the identification of compounds and for the determination of their purity (Data collection and their analysis will be performed by the student)
  • C, H, N, S analysis for the determination of the organic content (Measurement is performed as service, data analysis will be done by the student)
  • IR spectroscopy for the experimental prove if N-terminal or µ-1,3-bridiging anions are present (Measurement is performed as service, data analysis will be done by the student)
  • Magnetic measurements for investigations on the magnetic properties (Measurement is performed as service, data analysis will be done by the student)
  • Differential thermoanalysis (DTA and thermogravimetry (TG) coupled to mass spectroscopy (MS) as well as differential scanning calorimetry (DSC) and thermomicroscopy for investigations on the thermal properties of these compounds and for the preparation of the desired µ-1,3-bridiging coordination polymers ((Data collection and their analysis will be performed by the student)


Methods that are additionally available if needed for some special problems

  • Mößbauer spectroscopy for the characterization of iron compounds
  • Energy dispersive X-ray analysis (EDX) in combination with scanning electron microscopy (SEM) for qualitative and quantitative analysis
  • Atom absorption spectroscopy (AAS) for quantitative analysis


Benefit

General introduction into the synthesis of solid state compounds and how these compounds can be characterized using different analytical methods.

Basic knowledge especially on the practical aspects of analytical methods

Basic knowledge on data analysis using standard computer programs

Good mentoring because we are only a very small group

Introduction into the presentation of scientific results


If additional information is needed please contact me by e-mail

cnaether@ac.uni-kiel.de