This module explains how detailed information about structure, stereochemistry and the behaviour of chemical species in solution and in the solid state can be obtained by using luminescence spectroscopy, electron paramagnetic resonance (EPR) spectroscopy and diffraction techniques (specifically X-ray diffraction, neutron diffraction and electron diffraction, as well as electron microscopy).

1. describe the principles of luminescence spectroscopy, EPR spectroscopy, X-ray diffraction, neutron diffraction, electron diffraction and electron microscopy;
2. describe the different types of electronically excited states associated with organic and inorganic molecules;
3. describe and interpret the key physical parameters that characterize different excited states;
4. describe the processes that contribute to non-radiative deactivation (quenching) of excited states, including energy transfer mechanisms;
5. understand different classifications of luminescence such as bio-, chemi- and electro-luminescence;
6. apply knowledge of excited state molecules to various applications such as chemosensors and photodynamic therapy;
7. describe the use of the spin Hamiltonian to interpret EPR spectra in solution and in the solid state;
8. explain the major features of EPR spectra, and their correlations with structure;
9. predict the appearance of EPR spectra of organic radicals and simple paramagnetic metal complexes;
10. interpret EPR spectra, assign structures, and explain the methods adopted;
11. describe the basis of Electron Nuclear Double Resonance (ENDOR) spectroscopy and how it is used to resolve small hyperfine interactions;
12. understand the fundamental processes involved in the interaction of X-rays, neutron beams and electron beams with solids;
13. describe the fundamental similarities and differences between X-ray diffraction, neutron diffraction and electron diffraction;
14. understand the types of information about solid state structures that can be obtained from X-ray diffraction, neutron diffraction and electron diffraction techniques;
15. understand the basis of electron microscopy techniques;
16. appreciate the specific areas of application of X-ray diffraction, neutron diffraction and electron diffraction techniques;
17. formulate the optimum experimental strategy for exploring specific aspects of solid-state structure.

The module will be delivered in 22 1-hour lectures, 3 1-hour workshops and 1 1-hour tutorial.

Interpretation of EPR spectra for paramagnetic species in solution and in the solid state;

Formulating optimum experimental strategies (involving the use of one or more of the X-ray diffraction, neutron diffraction, electron diffraction or electron microscopy techniques) for exploring specific aspects of solid-state structure.

On completion of the module a student will be able to select appropriate techniques for determination of structure in solution or in the solid state for a range of chemical situations, and to assess the advantages/disadvantages for each particular purpose.

A written exam will test the student’s knowledge and understanding as elaborated under the learning outcomes. The coursework will allow the student to demonstrate his/her ability to judge and critically review relevant information.

This module describes the fundamentals and applications of luminescence measurements, EPR spectroscopy and diffraction techniques for the determination of structure and other chemical information. The topics covered in each section are as follows.

Luminescence Spectroscopy

Selection rules; quantized description; Jablonski.

Stokes shift; quantum yield; lifetimes.

Fluorescence; phosphorescence.

Types of chromophores; effect of structure on emission; donor-acceptor.

Energy transfer: Dexter versus Förster.

Quenching pathways: O₂; photoinduced electron transfer.

Applications to coordination complexes: TM; lanthanides.

Chemosensors; imaging; LEDs; PDT.

Chemoluminescence; bioluminescence; electroluminescence.

EPR Spectroscopy

Basic principles of Electron Paramagnetic Resonance (EPR).

Origin and significance of the electron Zeeman and nuclear Zeeman effect.

Derivation of a simple spin Hamiltonian for a two spin system (S = ½, I = ½).

Interaction of the electron with its environment and the resulting anisotropy and symmetry effects in EPR spectra.

Applications of EPR for characterization of paramagnetic systems.

Analysis and interpretation of EPR spectra of organic radicals in solution plus main group radicals and transition metal ions in frozen solution. Interpretation of the spin Hamiltonian parameters g and A (hyperfine) values.

Role of advanced EPR techniques, such as ENDOR, for structure determination of paramagnetic species.

Origin of the ENDOR effect.

Diffraction Techniques

Fundamentals:

Properties of X-rays.

Properties of electron beams.

Properties of neutron beams.

Production of X-rays and other radiation (conventional sources and synchrotron radiation).

Fundamentals of diffraction by crystalline solids.

Applications, Scope and Limitations of Techniques:

X-Ray diffraction (XRD) – applications of X-ray diffraction, single-crystal versus powder X-ray diffraction, advantages of using synchrotron radiation, limitations of X-ray diffraction.

Neutron diffraction (ND) – applications of neutron diffraction, neutron diffraction versus X-ray diffraction.

Electron diffraction and electron microscopy – electron diffraction (ED), transmission electron microscopy (TEM), scanning electron microscopy (SEM), low energy electron diffraction (LEED).

An indicative reading list will be included in the Course Handbook. Additional resource material will be available on Learning Central.