We report photoexcited-state crystal structures for two new members of the ͓Ru͑SO 2 ͒͑NH 3 ͒ 4 X͔Y family: 1 : X =H 2 O, Y = ͑ Ϯ ͒-camphorsulfonate 2 ; 2 : X = isonicotinamide, Y = tosylate 2 . The excited states are metastable at 100 K, with a photoconversion fraction of 11.1͑7͒% achieved in 1, and 22.1͑10͒% and 26.9͑10͒% at the two distinct sites in 2. We further show using solid-state density-functional-theory calculations that the excited-state geometries achieved are strongly influenced by the local crystal environment. This result is relevant to attempts to rationally design related photoexcitation systems for optical data-storage applications.

The photoinduced O-bound coordination mode in RuSO(2) complexes, previously observed only at 13 K, has been generated at 100 K in tetraammineaqua(sulfur dioxide)ruthenium(II) (±)-camphorsulfonate. This coordination state, often denoted MS1, decays to the η(2)-bound MS2 state, with an estimated half-life of 3.4(8) h and a long-lived population of 2.9(4)% at 120 K.

X-ray diffraction measurements and analyses were developed and used to examine the phase transition in KCl shocked to 7 GPa. Diffraction data were obtained below and above the transition stress, and related quantitatively to macroscopic compression in the two phases. Interplanar spacing measurements revealed isotropic compression of the unit cell. Above the transition stress, a diffraction peak from the (110) planes in phase II was observed consistently and the orientation of the transformed crystal structure was determined with respect to the phase I structure. This determination provides a mechanism for the atomic rearrangement from the rocksalt to the cesium chloride structure in KCl shocked along [100].

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