Research Infrastructure at the Department of Chemistry

1. Research Infrastructure at the Department of Chemistry Neil Brooks

2. Outline • Overview, basics and examples of core infrastructure • Total X-ray Fluoresence Spectroscopy – TXRF • IR/Raman spectroscopy • Differential Scanning Calorimetry (DSC) • Nuclear Magnetic Resonance (NMR) • Single Crystal X-ray Crystallography (SC-XRD) • Summary • Assorted other equipment

3. TXRF – Total X-ray Fluoresence Spectroscopy

4. TXRF: key parameters • Two Bruker S2 Picofox TXRF spectrometers in the group • Key information: accurate elemental compositions/ratios • Fast and easy • Low detection limit possible (e.g. ppb) • Multi-element sample analysis • Difficult to detect elements lighter than chlorine • Ejected X-rays from lighter elements low in energy (matrix effects)

5. TXRF: technique

6. TXRF: technique

7. TXRF example: [Br] and [Cl] in ionic liquids

8. IR/Raman Spectroscopy

9. IR: technique • FT-IR spectrometer Bruker Vertex 70 with Raman module Bruker RAM II • Vibrational spectroscopy • Key information: identification of particular bond vibrations

10. IR: technique • FT-IR spectrometer Bruker Vertex 70 with Raman module Bruker RAM II • Vibrational spectroscopy • Key information: identification of particular bond vibrations • Spectral range 4500 to 400 cm-1 • Transmittance mode (sample prep necessary) • Attenuated total reflection • Diamond or ZnSe crystal • Fast (ca. 1-2 minutes) • Far infrared (400 to 40 cm-1) also possible • Variable resolution (e.g. 1, 2, 4 cm-1) • Required sample: <5 mg

11. Raman: technique • FT-IR spectrometer Bruker Vertex 70 with Raman module Bruker RAM II • Different selection rules to IR • Nd-YAG laser λ = 1064 nm • Variable laser power (1-500 mW) • Fluoresence can be problem • Spectral range 3600 to 40 cm-1 • Variable resolution (e.g. 1, 2, 4 cm-1) • Sample dependent collection time (typically 2 minutes – 2 hours) • No background collection • Liq. N2 cooled Ge CCD detector • Required sample: 50-500 mg • Surface Enhancement possible (SERS)

12. Raman example: adsorption of 1H-benzotriazole on silver substrate in [Ag(MeCN)4]2[Ag(Tf2N)3] • text Pure Ag-LMS 1H-benzotriazole (0.1 M) 0.1M benzotriazole in Ag-LMS on Ag surface 0.1M benzotriazole in Ag-LMS (bulk) Pure benzotriazole Pure Ag-LMS

13. DSC – Differential Scanning Calorimetry

14. DSC: technique • Mettler-Toledo DSC822e module • Key information: phase transition temperatures/energetics • Required sample: 2-5 mg • Temperature range -60 to 250 °C • Variable heating rate (typically 10 °C/min) • Complimented with polarised optical microscopy (thermomicroscopy) on an Olympus BX-60 polarising microscope equipped with a Linkam THMS 600 hot stage. Temperature range: -196°C - 600°C.

15. DSC example: eutectic behaviour of DMSO2/acetamide mixtures DSC traces of DMSO2/acetamide mixtures Tamman plot

16. NMR – Nuclear Magnetic Resonance Spectroscopy

17. NMR: technique • Energy states of spin active nuclei split from degeneracy inside a magnetic field • E/M radation applied to populate the higher energy state • Difference in energy of higher and lower states measured is a function of the nucleus and its environment • Key information: chemical information about nucleus environment • 300, 400 and 600 MHz spectrometers available • Nucleus must be NMR active • Most common nuclei: 1H, 13C, 31P, 19F • Can not have unpaired electrons • Must have sufficient natural abundance • Liquid state: sample must be a liquid or disolved in a solvent • Required sample: 5-20 mg

18. Single Crystal X-ray Crystallography (SC-XRD)

19. SC-XRD: technique • Key information: absolute three-dimensional crystal structure • Allows the resolution of atom positions up to ±0.001 Å • Accurate bond and intermolecular distances • Scattering (diffraction) of X-rays from ordered array of molecules in a crystal leads to diffraction pattern (Bragg’s law: nλ=2dsinθ) • Diffraction pattern is directly related to the three-dimensional electron density pattern • Phase problem • Imperfect crystals

20. SC-XRD: practicalities • Must have (good quality) single crystal! • Crystal size (each dimension) must be 0.05 to 0.5 mm • Larger crystals can be cut to size • Smaller crystals may be possible but will take longer • Crystal growth • Evaporation of saturated solution • Addition of antisolvent • Growth from melt by slow cooling • What can be determined? • Can be used for phase identification • Crystal structure already known (unit cell check) • New structure determination • Elemental composition (on specific lattice sites)

21. SC-XRD example: structure of Ag-LMS • First synthesised a Cu-LMS of formula [Cu(MeCN)4][Tf2N] • Melting point 65 °C • New Ag-LMS of formula [Ag(MeCN)~2][Tf2N] • Melting point 18 °C • Slow cooling of Ag-LMS gave good quality crystals • Structure determined as [Ag(MeCN)4]2[Ag(Tf2N)3]

22. SC-XRD: case study structure of Ag-LMS • If [Ag(MeCN)4]2[Ag(Tf2N)3] is heated at 50 °C for a period of time new crystals appear • Crystal structure analysis shows the new compound is [Ag(MeCN)Tf2N] • One-dimensional polymeric structure • Melting point 90 °C

23. Overview

24. Assorted other equipment • Mass spectrometry • Absorption spectroscopy (UV-VIS-IR) • Varian Cary 5000: UV-VIS-NIR spectrophotometer (175-3300 nm) • Luminescence spectrometers • Viscosimetry • Brookfield cone plate viscosimeter (LVDV-II+ Programmable Viscometer) with cone spindle CPE-40 • X-ray powder diffraction setup with rotating Mo-anode • SAXS and WAXS • CHN microanalysis • CE Instruments EA-1110 CHN elemental analyser

25. Practicalities • Contact me by email: neil.brooks@chem.kuleuven.be to notify interest • Set up meeting to discuss how to proceed • Tom Vander Hoogerstraete (Chemistry) • M. Ganapathi (MTM) Acknowledgements