C O M M U N I C A T I O N S
Table 1. Properties of Select Materials
The photoluminescence (PL) intensity of these materials drops
off as phosphorus atoms are substituted for olefinic carbons. The
PL intensities of 2a-c are approximately equal to that of (E)-
stilbene, while that of B is only 8% that of (E)-stilbene, and
diphosphene-containing 3 does not exhibit appreciable PL. This
may be due to fluorescence quenching by interaction with phos-
phorus lone pairs.8a
In conclusion, a conveniently synthesized bifunctional ligand
capable of simultaneously supporting two heavier main group
multiple bonds has been reported. This ligand was employed in
the synthesis of new phospha-PPVs including the first conjugated
polymer incorporating PdP linkages along the polymer backbone.
Ligand 1 should allow access to a variety of linear conjugated
materials having multiply bonded elements previously excluded for
polymer synthesis.
PL
M
UV/vis (nm)
λπ-π*(log ꢀ)
UV/vis (nm)
n-π*(log ꢀ)
PL max intens b
(nm)
n
X
n
(g mol-1
)
λ
(%)
PDI
1a (na)
2a 4.5
1175
5000
7200
7300
5900
6500
399 (4.63) (na)
435 (4.76) (na)
427 (4.87) (na)
416 (4.65) 473 (4.54)
435 (4.63) 481 (4.42)
445 (4.03) (na)
460
481
486
481
(na)
545
620
80
130
110
∼0
8
(na)
2.3
2.2
1.9
2.1
(na)
2b
6
2c 6.5
3
B
5.8
6
a UV/vis and PL spectra in CHCl3. b Relative to (E)-stilbene.
Previous studies of DmpPdPMe3 showed that the diphosphene
DmpPdPDmp is produced in high yields by photolytic extrusion
of PMe3.13 Photolysis (C6D6, rt) of bifunctional analogue 1c does
indeed result in extrusion of two equivalents of volatile PMe3 and
formation of desired red polymer 3 in near quantitative yield
(Scheme 1).10 Thermolysis of 1c (neat, 250 °C) also effects the
same transformation and is the preferred method as it is very rapid
(ca. 2 min), is readily applied to larger quantities, and leads to fewer
side products. While reduction of ArPCl2 using magnesium or other
metals is a classic avenue to diphosphenes (ArPdPAr),14 low yields
rendered this route inappropriate for achieving polymers. To the
best of our knowledge, 3 is the first example of a polymer featuring
multiple bonds between two heavier main group elements along a
polymer backbone. More importantly, the successful stabilization
of diphosphene units by 1 suggests its viability in stabilizing other
E-E multiple bonds which may be incorporated into conjugated
polymer backbones.15
Acknowledgment. We thank Akshay Kokil, J. Benjamin Beck,
Prof. Christoph Weder, Prof. Stuart J. Rowan, and Prof. Malcolm
E. Kenney for helpful discussions and use of instrumentation, and
the National Science Foundation (CHE-0202040) for support.
Note Added after ASAP: In the version published on the Web
2/4/2004, two asterisks were missing from the column headings in
Table 1. The version posted 2/6/2004 and the print version are
correct.
Supporting Information Available: Details for synthesis and
characterization of 1-3. This material is available free of charge via
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JA0394683
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