23: Molecular Crystals and Light: Chemical Reactions in Cages (1982)


  • David Parker Craig Research School of Chemistry, The Australian National University


The Liversidge Research Lecture, delivered before the Royal Society of New South Wales, 20th May 1982. Reproduced by permission of the Royal Society of New South Wales from J. Proc. Roy. Soc. N.S.W., 1982, 115, 61-7.

"The kinetics, mechanisms, and stereochemistry of solid state photochemical reactions are different in fundamental ways from reactions in fluids, and constitute a distinct set of problems. Molecules in crystals below the melting point are confined by intermolecular forces to sharply defined regions, or 'cages'. Reactions take place between molecules within such cages in positions and orientations known from crystal structure analysis or in positions related to the perfect crystal structure by dislocations or local disordering."

"New concepts are being developed to advance understanding in this field. The best known is that of 'topochemistry', which is that static lattice constraints restrict the products of a photochemical reaction to those preformed in the parent crystal. Also recent theory leads to the proposal that there may be impulsive molecular displacements following light absorption and lasting only a few picoseconds that bring neighbour molecules close together and promote chemical change or excimer formation. The theory of this concept of 'dynamical preformation' is described and possible examples discussed."

Author Biography

David Parker Craig, Research School of Chemistry, The Australian National University


Born in Sydney, David Parker Craig spent much of his career at the University of Sydney, including as the Chair of Physical Chemistry in 1952–1956. When the Australian National University was founded, he was appointed a Foundation Chair of the new Research School of Chemistry. He also spent time at University College, London, as a Visiting Professor. From 1990–1994, Craig was President of the Australian Academy of Science. He sadly died in 2015, after this transcript was compiled.


For additional biographical information, photographic permissions, references and a list of honours, awards and publications, please see pages 2–4 of the transcript.


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Cohen, M.D. and Schmidt, G.M.J., 1964. 'Topochemistry. Part I. A survey.' J. Chem. Soc., 1996-2000.

Collins, M.A. and Craig, D.P., 1981. 'A simple model of photoinduced lattice instability.' Chem. Phys., 54, 305-321.

Collins, M.A. and Markey, B.R., 1982. (To be published).

Craig, D.P. and Mallett, C.P., 1982. 'Dynamic instabilities in excited molecular crystals. Packing calculations in anthracene systems.' Chem. Phys., 65, 129-142.

Craig, D.P. and Mallett, C.P., 1982. (To be published).

Craig, D.P. and Markey, B.R., 1980. 'Stereochemical constraints and lattice relaxation in crystal photochemistry.' Mol. Cryst. Liq. Cryst., 58, 77-94.

Craig, D.P., Mason, R., Pauling, P. and Santry, D.P., 1965. Molecular packing in crystals of the aromatic hydrocarbons.' Proc. Roy. Soc., A286, 98-116.

Craig, D.P. and Rajikan, J., 1977. 'Site selective photochemical change in anthracene crystals doped with 2-hydroxyanthracene.' Chem. Phys. Letters, 47, 20-22.

Craig, D.P. and Sarti-Fantoni, P., 1966. 'Photochemical dimerisation in crystalline anthracenes.' Chem. Comm., 742-743.

Liptay, L. and Schlosser, H.-J., 1972. 'The anisotropic polarizability of a few aromatic hydrocarbons.' Z. Naturforsch., 27a, 1336-1344.

Liptay, L., Walz, G., Baumann, L., Schlosser, H.-J., Deckers, H. and Dexter, L., 1971. 'Die Beeinflussung der optischen Absorption von Molekülen durch ein elektrisches Feld.' Z. Naturforsch., 26a, 2020-2038.

Mathies, R. and Albrecht, A.C., 1974. 'Experimental and theoretical studies on the excited state polarizabilities of benzene, naphthalene, and anthracene.' J. Chem. Phys., 60, 2500-2508.

Mellor, D.P., 1957. 'Founders of Australian Chemistry. Archibald Liversidge.' Proc. R.A.C.I, 24, 415-421.

Wegner, G., 1972. 'Topochemical polymerization of monomers with conjugated triple bonds.' Die Makromolekulare Chemie, 154, 35-48.

Williams, D.E., 1966. 'Nonbonded potential parameters derived from crystalline aromatic hydrocarbons.' J. Chem. Phys., 45, 3770-3778.

Portrait of David Parker Craig