Photocrystallography

Abstract

This review describes the development and application of a new crystallographic technique that is starting to enable the three-dimensional structural determination of molecules in their photo-activated states. So called 'photocrystallography' has wide applicability, particularly in the currently exciting area of photonics, and a discussion of this applied potential is put into context in this article. Studies are classified into four groups: photo-structural changes that are (i) irreversible; (ii) long-lived but reversible under certain conditions; (iii) transient with photo-active lifetimes of the order of microseconds; (iv) very short lived, existing at the nanosecond or even picosecond level. As photostructural changes relative to the 'ground state' can be subtle, this article necessarily concentrates on small-molecule single-crystal X-ray diffraction given that high atomic resolution is possible. That said, where it is pertinent, references are also made to related major advances in photo-induced macromolecular crystallography. The review concludes with an outlook on this new research area, including the future possibility of studying even more ephemeral, femtosecond-lived, photo-active species.

Reversible 100 % Linkage Isomerization in a Single‐Crystal to Single‐Crystal Transformation: Photocrystallographic Identification of the Metastable [Ni(dppe)(η1‐ONO)Cl] Isomer

“…Unlike the light‐induced electronic spin state (LIESST) phenomenon,12 the photoexcitation in the systems studied is not cooperative and the maximum level of excitation observed is 47 % for [Ni(η 5 ‐ C 5 Me 5 )(NO)]13 as is shown in Table 1; although 76 % conversion of the bonding mode of the nitrosyl group has recently been reported in trans ‐[RuCl(py) 4 (NO)][PF 6 ] 2 ⋅0.5 H 2 O (py=pyridine) from an IR investigation 14. The inability to obtain high levels of excitation may be attributed to either the lack of penetration of the laser beam into the crystal or to the generation of unfavorable strain energy within the crystal as the structure changes 1c. This limitation is unfortunate if such materials are to be exploited as data‐storage materials where the control over the linkage isomer formed is essential.…”

Synthesis and Biological Evaluation of 1‐Methyl‐1H‐indole–Pyrazoline Hybrids as Potential Tubulin Polymerization Inhibitors

“…Crystal structure determination of compounds e1 and e8 was carried out on a Nonius CAD4 diffractometer equipped with graphite‐mono chromated MoKa ( k =0.71073 Å) radiation. The structure was solved by direct methods and refined on F 2 by full‐matrix least‐squares methods using SHELX‐97 . All non‐hydrogen atoms of compounds e1 and e8 were refined with anisotropic thermal parameters.…”

“…The structure was solved by direct methods and refined on F 2 by full-matrix least-squares methods using SHELX-97. [24] All non-hydrogen atoms of compounds e1 and e8 were refined with anisotropic thermal parameters. All hydrogen atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms.…”

In situ synthesis, crystallisation, and thin-film processing of single crystals of trans-[Ru(SO2)(NH3)4(H2O)][p-TolSO3]2 bearing SO2 linkage photo-isomers: towards optical device applications

“…[2][3][4][5][6][7][8][9][10] A proportion (11%) of its dark-state, characterised by an η 1 -SO 2 coordination mode and binding to the ruthenium atom via sulfur, was found to photo-isomerise to an η 2 -SO 2 (side-on) coordination mode when exposed to 488 nm light at T = 90 K, whereupon it remained metastable up to T ≤ 250 K. Photo-inducing [Ru]-SO 2 at T = 13 K with a tungsten lamp and subsequently maintaining the sample at this temperature generates a thermally less stable η 1 -OSO configuration (end-on), which coexists in a metastable state with the η 2 -SO 2 isomer in proportions of 36% and 8%, respectively (56% nonphoto-converted isomer). [11][12][13][14] The near-ambient temperature, at which the metastable η 2 -SO 2 photo-isomer of this complex is observable, is important from a practical perspective, given that optical devices usually require operating temperatures as close to room temperature as possible. This means that optical pumping at T = 13 K instead of T = 96 K ultimately generates a significantly higher proportion of the desirable photo-isomer.…”