3 research outputs found
Organometallic Oligomers Based on Bis(arylacetylide)bis(P-chirogenic phosphine)platinum(II) Complexes: Synthesis and Photonic Properties
A series of P-chirogenic
oligomers of the type (īøCī¼Cīø<b>aryl</b>īøCī¼CīøPtL<sub>2</sub>īø)<i><sub>n</sub></i> [L = (<i>R</i>)- and (<i>S</i>)-PĀ(Ph)Ā(<i>i</i>Pr)Ā(C<sub>17</sub>H<sub>35</sub>); <b>aryl</b> =
1,4-benzene, 2,1,3-benzothiadiazole] along the corresponding achiral
analogues (L = PBu<sub>3</sub>) and model complexes PhCī¼CPtL<sub>2</sub>Cī¼CPh were prepared from the ephedrine strategy and
were fully characterized [<sup>1</sup>H, <sup>31</sup>P NMR; IR; small-angle
X-ray scattering (SAXS); gel permeation chromatography (GPC); thermal
gravimetric analysis (TGA); circular dichroism, UVāvis, and
luminescence spectroscopy; photophysics, and degree of anisotropy
measurements]. From the CD measurements, the chiral environment of
the phosphine ligands is modestly felt by the aryl moieties. Concurrently,
the TGA shows that the PĀ(C<sub>17</sub>H<sub>35</sub>)Ā(Ph)Ā(<i>i</i>-Pr)-containing materials are more stable than those containing
the shorter chain ligand PBu<sub>3</sub>, and exhibits red-shifted
absorption and emission bands compared to those including the PBu<sub>3</sub> ligands. The presence of the long chain on the phosphorus
atoms does not greatly alter the photophysical parameters, notably
the emission lifetimes, and fast triplet energy transfer terminal*
ā central unit has been deduced from the absence of luminescence
arising from the terminal units
Luminescent PāChirogenic Copper Clusters
P-chirogenic
clusters of the cubanes [Cu<sub>4</sub>I<sub>4</sub>L<sub>4</sub>]
(L = chiral phosphine) were prepared from (+)- and (ā)-ephedrine
with L = (<i>S</i>)- or (<i>R</i>)-(R)Ā(Ph)Ā(<i>i</i>-Pr)P (with R = CH<sub>3</sub> (seven steps) or C<sub>17</sub>H<sub>35</sub> (10 steps)) with e.e. up to 96%. The X-ray structure
of [Cu<sub>4</sub>I<sub>4</sub>((<i>R</i>)-(CH<sub>3</sub>)Ā(Ph)Ā(<i>i</i>-Pr)ĀP)<sub>4</sub>] confirmed the cubane
structure with average CuĀ·Ā·Ā·Cu and CuĀ·Ā·Ā·I
distances of 2.954 and 2.696 Ć
, respectively. The cubane structure
of the corresponding [Cu<sub>4</sub>I<sub>4</sub>((<i>S</i>)-(CH<sub>3</sub>)Ā(Ph)Ā(<i>i</i>-Pr)ĀP)<sub>4</sub>] was
established by the comparison of the X-ray powder diffraction patterns,
and the opposite optical activity of the (<i>S</i>)- and
(<i>R</i>)-ligand-containing clusters was confirmed by circular
dichroism spectroscopy. Small-angle X-ray scattering patterns of one
cluster bearing a C<sub>17</sub>H<sub>35</sub> chain exhibit a weak
signal at 2Īø ā¼ 2.8Ā° (<i>d</i> ā¼
31.6 Ć
), indicating some molecular ordering in the liquid state.
The emission spectra exhibit two emission bands, both associated with
triplet excited states. These two bands are assigned as follows: the
high energy emission is due to a halide-to-ligand charge transfer,
XLCT, state mixed with LXCT (ligand-to-halide-charge-transfer). The
low energy band is assigned to a cluster-centered excited state. Both
emissions are found to be thermochromic with the relative intensity
changing between 77 and 298 K for the clusters in methylcyclohexane
solution. Several differences are observed in the photophysical parameters,
emission quantum yields and lifetimes for R = CH<sub>3</sub> and C<sub>17</sub>H<sub>35</sub>. The measurements of the polarization along
the emission indicate that the emission is depolarized, consistent
with an approximate tetrahedral geometry of the chromophores
Luminescent PāChirogenic Copper Clusters
P-chirogenic
clusters of the cubanes [Cu<sub>4</sub>I<sub>4</sub>L<sub>4</sub>]
(L = chiral phosphine) were prepared from (+)- and (ā)-ephedrine
with L = (<i>S</i>)- or (<i>R</i>)-(R)Ā(Ph)Ā(<i>i</i>-Pr)P (with R = CH<sub>3</sub> (seven steps) or C<sub>17</sub>H<sub>35</sub> (10 steps)) with e.e. up to 96%. The X-ray structure
of [Cu<sub>4</sub>I<sub>4</sub>((<i>R</i>)-(CH<sub>3</sub>)Ā(Ph)Ā(<i>i</i>-Pr)ĀP)<sub>4</sub>] confirmed the cubane
structure with average CuĀ·Ā·Ā·Cu and CuĀ·Ā·Ā·I
distances of 2.954 and 2.696 Ć
, respectively. The cubane structure
of the corresponding [Cu<sub>4</sub>I<sub>4</sub>((<i>S</i>)-(CH<sub>3</sub>)Ā(Ph)Ā(<i>i</i>-Pr)ĀP)<sub>4</sub>] was
established by the comparison of the X-ray powder diffraction patterns,
and the opposite optical activity of the (<i>S</i>)- and
(<i>R</i>)-ligand-containing clusters was confirmed by circular
dichroism spectroscopy. Small-angle X-ray scattering patterns of one
cluster bearing a C<sub>17</sub>H<sub>35</sub> chain exhibit a weak
signal at 2Īø ā¼ 2.8Ā° (<i>d</i> ā¼
31.6 Ć
), indicating some molecular ordering in the liquid state.
The emission spectra exhibit two emission bands, both associated with
triplet excited states. These two bands are assigned as follows: the
high energy emission is due to a halide-to-ligand charge transfer,
XLCT, state mixed with LXCT (ligand-to-halide-charge-transfer). The
low energy band is assigned to a cluster-centered excited state. Both
emissions are found to be thermochromic with the relative intensity
changing between 77 and 298 K for the clusters in methylcyclohexane
solution. Several differences are observed in the photophysical parameters,
emission quantum yields and lifetimes for R = CH<sub>3</sub> and C<sub>17</sub>H<sub>35</sub>. The measurements of the polarization along
the emission indicate that the emission is depolarized, consistent
with an approximate tetrahedral geometry of the chromophores