Research Infrastructure at the Department of Chemistry

Neil Brooks

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

TXRF – Total X-ray Fluoresence Spectroscopy

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)

TXRF: technique

TXRF: technique

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

[Br] in [C4mim][Tf2N] (ppm)

Recovery rates (%)

RSD (%)

10000 105 6

4000 105 9

2000 113 4

1000 100 6

100 100 60 2000 4000 6000 8000 10000

0

2000

4000

6000

8000

10000

12000

Mea

sure

d Br

conc

. in [C

4mim

][Tf 2N

] (pp

m)

Expected Br conc. in [C4mim][Tf2N] (ppm)

0 2000 4000 6000 8000 10000

0

2000

4000

6000

8000

10000

Mea

sure

d Cl

conc

. in [C

4mim

][OAc

] (pp

m)

Expected Cl conc. in [C4mim][OAc] (ppm)

[Cl] in [C4mim][OAc] (ppm)

Recovery rates (%)

RSD (%)

10000 92 74000 90 82000 94 141000 97 5400 91 10200 96 10100 98 13

IR/Raman Spectroscopy

IR: technique

• FT-IR spectrometer Bruker Vertex 70 with Raman module Bruker RAM II

• Vibrational spectroscopy– Key information: identification of particular bond vibrations

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

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)

Raman example: adsorption of 1H-benzotriazole on silver substrate in

[Ag(MeCN)4]2[Ag(Tf2N)3]

• text

1H-benzotriazole (0.1 M)Pure Ag-LMS

Pure Ag-LMS

Pure benzotriazole

0.1M benzotriazole in Ag-LMS (bulk)

0.1M benzotriazole in Ag-LMS on Ag surface

DSC – Differential Scanning Calorimetry

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.

DSC example: eutectic behaviour of DMSO2/acetamide mixtures

DSC traces of DMSO2/acetamide mixtures Tamman plot

NMR – Nuclear Magnetic Resonance Spectroscopy

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

Single Crystal X-ray Crystallography (SC-XRD)

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

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)

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]

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

Overview

Sample prep required

Amount sample

Experiment time

Analysis time

Difficulty

TXRF Yes ppm <1 hour 1 hour Easy

IR No <5 mg 2-5 minutes 15 minutes Easy

Raman No 50-500mg 0.5-4 hours 1 hour Medium

DSC No 2-5 mg Several hours 15 minutes Easy

NMR Yes 5-20 mg 0.5-4 hours 1 hour Medium

SC-XRD Yes one crystal 1 day 1+ week Hard

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

• 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)

Practicalities

Acknowledgements