Normal and defective perylene substitution sites in alkane crystals

Abstract

Articles you may be interested inLow temperature single molecule spectroscopy using vibronic excitation and dispersed fluorescence detection The Shpol'skii system perylene in n-hexane: A computational study of inclusion sitesWe examine experimentally and computationally the nature of substitution of perylene in polycrystalline solid alkane matrices ͑Shpol'skii systems͒. The technique of low temperature excitation-emission matrix spectroscopy is used to determine all substitution sites in alkane matrices from hexane to decane. A theoretical method from the group of Jortner ͓Shalev et al., J. Chem. Phys. 95, 3147 ͑1991͔͒, which was extended and applied by us to this problem in the past ͓Wallenborn et al., J. Chem. Phys. 112, 1995 ͑2000͔͒, allows one to separate the perylene sites in all alkanes into normal and defective sites. Normal sites are obtained by direct substitution of two alkane molecules by a perylene molecule, while defective sites are derived from normal sites by eliminating one of the four nearest neighbors of perylene in the lattice planes parallel to the chromophore. We discuss the strengths and limitations of the present theoretical treatment, which can serve as a valuable supplement and guide to line-narrowing and single-molecule spectroscopic investigations of impurity centers in low-temperature solids.

Surface Structure of Organoclays

“…The 2C 12 ions are fully organized into islands. The result is supported by the close match between experimental and computed basal-plane spacings for 2C 18 -mica and 2C 12 -mica (Table 1).…”

“…In Figure 2, the computed basal-plane spacings for one-phase and two-phase surfaces are compared with the experimental values [7] at low and high temperatures. Both graphs indicate that the 2C 18 chains are homogeneous with the alkali ions on the surface. With decreasing chain length, a trend towards phase segregation between organic chains and alkali ions is apparent.…”

“…At elevated temperatures, some ammonium ions change to another cavity, especially in the homogeneous structures where rearrangements are geometrically easier to achieve. A representative example of ammonium headgroup positions for 2C 18 ions in the homogeneous phase is displayed in Figure 1b.…”

“…100 snapshots are subsequently taken at intervals of 1 ps to compute the system's properties, such as basal-plane spacings and conformations of the alkyl chains. We conduct our calculations with the extended consistent force field 91, which is accurate in modeling organically modified silicates and was previously described together with other simulation details, [13,18,19] using the Discover program from MSI. [20] We note that the NpT ensemble is not required for the simulation (instead of NVT)…”

Excited-State Distortions of Cyclometalated Ir(III) Complexes Determined from the Vibronic Structure in Luminescence Spectra

“…Such systems have been widely used to obtain narrow spectral lines from planar aromatic hydrocarbons. [34][35][36][37] In a recent study, sharp line vibronic structure from a planar organometallic compound in a Shpol'skii matrix was reported. 38 It is surprising that an octahedral organometallic ion can be incorporated in a Shpol'skii matrix.…”