Geometry changes of a Cu(I) phenanthroline complex on photoexcitation in a confining medium by time-resolved X-ray diffraction

Using a stroboscopic technique, in which the molecule is repeatedly excited and the structural change is probed more than 5000 times per second immediately after excitation, we performed a 16 K time-resolved single-crystal study of the microsecond lifetime triplet state of the Cu(I)phenanthroline derivative[Cu(I)(dmp)(dppe)][PF6] (dppe = 1,2-bis(diphenylphosphino)ethane). The geometry changes on excitation differ for the two symmetry-independent molecules, but are in the same direction as calculated for an isolated reference molecule, although the flattening distortion in the crystal is significantly smaller, implying that the reorganization energy is greatly affected by the confining medium.     

The first photocrystallographic evidence for light-induced metastable linkage isomers of ruthenium sulfur dioxide complexes

Light-induced metastable linkage isomers of trans-[Ru(NH(3))(4)Cl(SO(2))]Cl and trans-[Ru(NH(3))(4)(H(2)O)(SO(2))](C(6)H(5)SO(3))(2) have been identified for the first time using photocrystallographic methods. In both linkage isomers the SO(2) ligand is side bound, but the Ru-O and Ru-S distances are considerably longer and almost equal in the trans-H(2)O isomer. DFT calculations confirm that both isomers correspond to minima on the ground-state potential energy surface and also predict the existence of a second oxygen-bound isomer for both compounds. The decay of the light-induced species has been studied by both DSC and IR. Activation energies for the thermal back-reaction, as derived from the temperature-dependent disappearance of light-induced IR bands, are 50.0 and 58.4 kJ/mol for the two isomers, which is larger than the corresponding numbers for photoinduced side-bound nitrosyl linkage isomers.     

Formation of pyrene nano-rods within a supramolecular framework

The combination of trimesic acid and the tri-dentate linker 1,3,5-tri(4-pyridyl)-2,4,6-triazine leads to the assembly of a bilayer structure, which contains four pyrene molecules per cavity; adjacent tetrameric aggregates within the channels formed by the superimposed layers combine to yield pyrene nano-rods.     

Direct Observation of the Binding Mode of the Phosphonate Anchor to Nanosized Polyoxotitanate Clusters

The structures of three newly synthesized phosphonate‐substituted polyoxotitanates are reported. The Ti/O core of [Ti₄O(OEt)₁₂(PhenylPO₃)] ( 1 ) is the building block for two larger phosphonate‐substituted nanoclusters, [Ti₂₅O₂₆(OEt)₃₆(PhenylPO₃)₆] ( 2 ) and [Ti₂₆O₂₆(OEt)₃₉(PhenylPO₃)₆]Br ( 3 ). All compounds exhibit a not previously recognized triply bridging binding mode of the phosphonate anchor with short connecting Ti? O bonds, the average of which is 2.010(7) Å. Comparison with previously reported work suggests that the binding mode of the phosphonate anchor is strongly dependent on the structure of the underlying substrate.     

On the crystallography of the TTF-TCNQ salt at reduced temperatures

A structure determination of the one-dimensionally conducting salt tetrathiofulvalinium-tetracyanoquinodimethanide (TTF-TCNQ) at 100°K, and additional measurements at lower temperatures, show that no major change in crystal structure occurs between room temperature and 40°K. At 100°K the interplanar spacings are reduced from 3.47 to 3.43 and from 3.17 to 3.11 Å for the TTF and TCNQ stacks, respectively. The bond lengths at 100°K agree better with the values listed for salts of TCNQ^-0.5, than with those for TCNQ^-1. On cooling a broadening of the b1 axis reflections is observed, which would be compatible with one-dimensional distortions of the crystal lattice.     

Shedding light on the structure of a photoinduced transient excimer by time-resolved diffraction

Time-resolved single-crystal diffraction performed with synchrotron radiation shows that the 53(1) micros phosphorescent state, generated in the crystalline phase of trimeric {[3,5-(CF3)(2)Pyrazolate]Cu}(3) molecules by exposure to 355 nm of light at 17 K, is due to the formation of an excimer rather than the shortening of the intramolecular Cu...Cu distances within the trimeric units, or the formation of a continuous chain of interacting molecules. One of the intermolecular Cu...Cu distances contracts by 0.56 Angstroms from 4.018(1) to 3.46(1) Angstroms;, whereas the interplanar spacing of the trimers is reduced by 0.65 Angstroms; from 3.952(1) to 3.33(1) Angstroms. Density-functional theory calculations support the formation of a Cu...Cu bond through the intermetallic transfer of a Cu 3d electron to a molecular orbital with a large 4p contribution on the reacting Cu atoms.     

Structure and photoluminescence of a benzil nanocolumn in a C-methylcalix[4]resorcinarene-based framework

A new framework based on C-methylcalix[4]resorcinarene and the flexible nonconjugated spacer 1,4-bis(imidazol-1yl-methyl)benzene encloses a large one-dimensional channel, containing benzil nanocolumns. Unlike in a previously reported series of benzil-containing supramolecular solids with conjugated linker molecules, benzil luminescence is observed, but the lifetime of 580 ns at 77 K is considerably shorter than the 145 micros reported for neat benzil at room temperature.