A photocrystallographic study of packing effects on linkage isomerism Ben Coulson and Lauren Hatcher Cardiff University, UK Linkage photoisomerism is a phenomenon whereby transition metal complexes alter the coordination mode of a ligand upon interaction with light. This process can be characterised using photocrystallography, whereby single crystals of photoactive complex are irradiated during x-ray diffraction measurements to observe the nature and extent of the isomerism present. 1, 2
Figure 1: Linkage photoisomerism in nitro-complex of metal [M] Linkage photoisomerism occurs in certain metal-nitro complexes, wherein the nitrogen-bound nitro- ligand isomerises to the metastable oxygen-bound nitrito- mode (Figure 1). A family of novel palladium nitro- complexes has been synthesised by varying the functionality of an ester group distant from the metal centre. It is demonstrated that chemically altering these distant moieties has little impact on the electronics of metal centre in the solution state. However, adjusting the molecular shape impacts molecular packing in the crystal state, which in turn alters the photophysics of the system in the solid state. By varying temperature and irradiance, the kinetic stability of the metastable state has been investigated for each compound. Crystal data is then used as a basis to simulate the systems and visualise the mechanism of the isomerism process. It is suggested that the geometry change caused by linkage photoisomerism may be translatable into an induced dielectric dipole if used to change the steric environment of an within a suitable host material. Metal-organic frameworks (MOFs) are ordered, porous structures containing metal nodes and organic struts surrounding uniform pores. Novel MOF materials have been synthesized containing the palladium moieties already studied in molecular systems, and the implications of the results gained from molecular systems are considered in the context of utilising linkage photoisomerism as a pathway to control macroscopic properties. References 1. Hathaway, G. Crevatin, D. Omar, B. H. Williams, B. A. Coulson, C. C. Wilson and P. R. Raithby, Communications Chemistry , 2022, 5 , 102. 2. P. Coppens, I. Novozhilova and A. Kovalevsky, Chem Rev , 2002, 102 , 861-884.
P04
© The Author(s), 2023
Made with FlippingBook Learn more on our blog