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 example: [Br] and [Cl] in ionic liquids [Br] in [C 4 mim][Tf 2 N] (ppm) Recovery rates (%) RSD (%) [Cl] in [C 4 mim][OAc] (ppm) Recovery rates (%) RSD (%)

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. N 2 cooled Ge CCD detector Required sample: mg Surface Enhancement possible (SERS)

Raman example: adsorption of 1H-benzotriazole on silver substrate in [Ag(MeCN) 4 ] 2 [Ag(Tf 2 N) 3 ] text 1H-benzotriazole (0.1 M)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 mixturesTamman 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: 1 H, 13 C, 31 P, 19 F –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 ][Tf 2 N] –Melting point 65 °C New Ag-LMS of formula [Ag(MeCN) ~2 ][Tf 2 N] –Melting point 18 °C Slow cooling of Ag-LMS gave good quality crystals Structure determined as [Ag(MeCN) 4 ] 2 [Ag(Tf 2 N) 3 ]

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

Overview Sample prep required Amount sample Experiment time Analysis time Difficulty TXRFYesppm<1 hour1 hourEasy IRNo<5 mg2-5 minutes15 minutesEasy RamanNo50-500mg0.5-4 hours1 hourMedium DSCNo2-5 mgSeveral hours15 minutesEasy NMRYes5-20 mg0.5-4 hours1 hourMedium SC-XRDYesone crystal1 day1+ weekHard

Assorted other equipment Mass spectrometry Absorption spectroscopy (UV-VIS-IR) –Varian Cary 5000: UV-VIS-NIR spectrophotometer ( 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 to notify interest –Set up meeting to discuss how to proceed Tom Vander Hoogerstraete (Chemistry) M. Ganapathi (MTM) Practicalities Acknowledgements