Modular Synthesis of Spirocyclic Germafluorene-Germoles: A New Family of Tunable Luminogens

Article abstract of DOI:10.1002/chem.201503377

The zirconium-mediated synthesis of a new class of air-stable spirocyclic germafluorene-germole (SGG) luminogens is reported. These species contain ring-fused germafluorene and germole units that display color-tunable fluorescence when peripheral aryl sub

Full text of DOI:10.1002/chem.201503377

DOI: 10.1002/chem.201503377
Full Paper
&
Luminescence
Modular Synthesis of Spirocyclic Germafluorene–Germoles: A New
Family of Tunable Luminogens
[
a]
Olena Shynkaruk, Gang He, Robert McDonald, Michael J. Ferguson, and Eric Rivard*
Abstract: The zirconium-mediated synthesis of a new class
of air-stable spirocyclic germafluorene–germole (SGG) lumi-
nogens is reported. These species contain ring-fused germa-
fluorene and germole units that display color-tunable fluo-
rescence when peripheral aryl substituents are appended.
Three distinct pathways are introduced for SGG modification
(Stille, Suzuki–Miyaura, and zirconocene-mediated cou-
plings), which enable the preparation of new libraries of mo-
lecular and polymeric SGG light-emitters with tunable lumi-
nescence and desirable thermal- and photo-stability.
Introduction
synthesis of structurally related phosphorescent tellurophenes
by an efficient zirconium-mediated alkyne-coupling/atom-sub-
[
9,10]
Red, blue, and green are the three main chromic components
stitution process.
A similar protocol has been used to
[1]
for achieving full-color displays. However obtaining long-
term blue luminescence is very challenging due to the high
propensity for material degradation during device operation.
For example, the widely studied blue-emitting 9,9’-dialkylfluor-
enes tend to form oxidized green-emitting ketonic products
access photoluminescent metalloles that contain main-group
[
11]
elements,
and Tilley and co-workers have also prepared
a number of neutral and dianionic siloles and germoles by
5
[12]
using Negishi’s reagent “Cp Zr” (Cp=h -C H ; Scheme 1). In
2
5
5
a promising recent development, the Staubitz group synthe-
sized polystannoles with the help of Zr/Sn element-substitu-
[
2]
over time. One strategy being explored to counteract unde-
sired oxidation upon excitation is to construct heterofluorene
emitters that feature Si, Ge, or Sn atoms within a metallole
ring which leads to enhanced s*–p* conjugation and a lower-
[
13]
tion chemistry.
[
3]
energy LUMO. Another viable approach to increase the per-
[3e,4]
formance of emissive heterofluorenes
is to orthogonally
link two fluorene units within a spirocyclic arrangement: this
process decreases the intermolecular quenching interactions
and concurrently improves the solubility and processability of
[5]
the resulting materials. However, the widespread implemen-
tation of spirocyclic compounds as light-emitting device com-
ponents has been hampered by limited synthetic ap-
[
6]
proaches.
Five-membered metalloles R EC R’ (R and R’=various sub-
2
4
4
stituents; E=Si, Ge, Sn, or Pb) represent a prominent class of
Scheme 1. Zirconocene-mediated synthesis of germoles and the structure of
the new SGGs introduced in this paper.
[
7]
conjugated material with useful reported properties, such as
efficient aggregation-induced emission (AIE) and colorimetric
analyte sensing. Moreover, the peripheral R and R’ groups and
inorganic element (E) in the ring can be altered, which leads to
In order to create materials with enhanced processability (as
found for the spirofluorenes) and incorporate the tunable lumi-
nescence available to metallole units, we prepared the new
hybrid materials spirocyclic germafluorene–germoles (SGGs;
[8]
luminescence tailoring. Recently, our group has explored the
[
a] O. Shynkaruk, Dr. G. He, Dr. R. McDonald, Dr. M. J. Ferguson,
Prof. Dr. E. Rivard
[14]
Scheme 1). We have shown that a potentially vast array of
Department of Chemistry
structurally distinct SGGs can be obtained by a highly modular
synthetic approach and that on/off switching of the emission
from each heterocyclic luminophore is possible by functional-
group control. This property should open the door to dual-
light emission, which has recently been used to achieve white
University of Alberta
11227 Saskatchewan Drive
Edmonton, T6G 2G2
Alberta (Canada)
Fax: (+1)780-492-8231
E-mail: erivard@ualberta.ca
[
15]
photoluminescence from a single molecular entity.
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201503377.
Chem. Eur. J. 2016, 22, 248 – 257
248
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
lengths in 2 and 3 fall within a narrow range (1.932(4)–
Results and Discussion
1
.955(4) Š), and are similar to the GeÀC bond lengths found in
[17]
This project began with the preparation of SGGs that con-
tained tetraethylcyclogermole (GeC Et ) as the core unit to
known germafluorenes.
To verify whether the dibrominated SGG 3 could undergo
Stille coupling with an aromatic partner to yield an emissive
species with potentially extended p conjugation, 3 was reacted
under microwave-assisted conditions with trimethylstannylben-
4
4
impart solubility in common organic solvents (Scheme 2). The
[
18]
[19]
zene (2 equiv)
or 2-(trimethylstannyl)thiophene (2 equiv)
(
Scheme 3). In each case, BrSnMe3 elimination transpired to
Scheme 3. Preparation of SGGs 4 and 5 by Stille coupling.
yield phenyl- and thiophene-capped SGGs 4 and 5 as colorless
solids with unoptimized isolated yields of 31 and 14%, respec-
tively, after column chromatography. Notably, the use of 2-
Scheme 2. Synthesis of alkylated SGGs 2 and 3.
(
tributylstannyl)thiophene as a coupling partner with 3 afford-
first analogue FlGeC Et (2; Fl=fluorenyl) was prepared by
ed pure 5 with an elevated recrystallized yield of about 50%.
The thiophene-substituted SGG 5 yielded crystals suitable
for X-ray analysis (Figure 2); however, the phenyl-capped ana-
logue 4 consistently afforded poorly formed crystals upon re-
crystallization, and thus only the atom connectivity could be
determined. Notably, the thiophene groups in 5 are positional-
ly disordered over two sites and exist in nearly co-planar ar-
rangements with the proximal germafluorene unit (e.g., S1(A)-
C13(A)-C3(A)-C2(A) torsion angle=6.3(10)8).
4
4
condensation of readily available 2,2’-dilithiofluorene with the
[12]
known dichlorogermole Cl GeC Et (1). Compound 2 is air-
2
4
4
and moisture-stable, yet non-emissive in solution and in the
solid state. Attempts to directly install bromine substituents
onto the germafluorene unit by treating 2 with N-bromosucci-
nimide (NBS) failed because undesired GeÀC bond-scission
transpired. Instead, we condensed a prebrominated dilithio-
fluorene with 1 to yield the dibromo-functionalized SGG 3
(
Scheme 2). The structures of these SGGs were confirmed by
[16]
single-crystal X-ray crystallography (Figure 1) and, as expect-
ed, perpendicular arrangements existed between the linked
germole and germafluorene units: interplanar angles between
each fused Ge heterocycle are 89.79(15)8 and 84.82(6)8 for
compounds 2 and 3, respectively. The central GeÀC bond
Figure 2. Thermal-ellipsoid plot (30% probability) of thiophene-capped SGG
5
with hydrogen atoms omitted for clarity; only one molecule of the two in
the asymmetric unit is shown. Selected bond lengths [Š] and angles [8] (pa-
rameters for the second molecule in the asymmetric unit are given in square
brackets): Ge(1A)ÀC(1A) 1.945(2) [1.954(2)], Ge(1A)ÀC(24A) 1.937(2)
[1.942(3)]; C(1A)-Ge(1A)-C(12A) 89.06(9) [89.36(10)], C(24A)-Ge(1A)-C(21A)
90.91(9) [90.92(11)].
Figure 1. Thermal-ellipsoid plot (30% probability) of 3 with hydrogen atoms
omitted for clarity. Selected bond lengths [Š] and angles [8]: GeÀC(1)
1
9
.9494(14), GeÀC(7) 1.9359(14); C(1)-Ge-C(1A) 88.78(8), C(7A)-Ge-C(7)
0.77(9).
Chem. Eur. J. 2016, 22, 248 – 257
www.chemeurj.org
249
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
SGGs 4 and 5 emit violet-blue light in solution in THF when
irradiated. Compound 4 fluoresces at lemission(em) =377 nm
[
lexcitation(ex) =332 nm; quantum yield (F)=0.03], while 5 emits
at 386 and 407 nm (F=0.83) when excited at l =348 nm
em
[16]
(
Figure S18 in the Supporting Information). This optical be-
havior mirrors that noted for the analogous phenyl- and thio-
phene-substituted dioctylfluorenes 6 and 7 prepared by Le-
[
20]
clerc (Scheme 3); however, the phenyl-substituted fluorene 6
has a significantly higher quantum yield in solution in THF
(
F=0.64) relative to its germanium congener 4. The optical,
thermal, and the photo-oxidative properties of thiophene-
[
20d]
capped germafluorene 5 and dioctylfluorene 7 (F=0.75),
were compared in more detail due to their similarly high F
values. Notably, 5 and 7 each show maximum absorption at
l=355 nm in THF (Figure S14 in the Supporting Informa-
[
16]
tion). However, their fluorescence spectra have discernable
vibronic features, which suggests a high level of rigidity within
these molecules in the first excited singlet state that leads to
[20a]
a narrow distribution of possible conformers.
The fluores-
cence spectra of each species in the solid state is redshifted by
about 30 nm relative to the solution spectra (Figure S18 and
[16]
S19 in the Supporting Information); this effect can be ex-
plained by enhanced heterofluorene–thiophene co-planarity.
Both 5 and 7 exhibit fluorescence based on the lifetimes
found: t=0.94 ns and t=1.05 ns, respectively. The close simi-
larity of the absorption and emission profiles of 5 and 7
(
Figure 3) suggest that the p manifolds within the bis(thienyl)-
biaryl portion of the germafluorene and fluorene residues are
[20e]
primarily involved in luminescence,
with little influence
from the spirolinked Ge atom or the germole unit in 7.
To determine whether the incorporation of Ge within the
spirocycle could increase photo-oxidative stability for display
applications, preliminary comparative photobleaching experi-
ments on thin films of 5 and 7 were performed under aerobic
conditions (Figure 4). To the best of our knowledge, this is the
first example of such a study for heterofluorenes, and it is of
potential use to identify candidates for the development of
light-emitting diodes (LEDs) that work without substantial en-
Figure 3. Emission (a) and excitation (c) spectra of a) 5 and b) 7 in so-
lution in THF.
[
21]
capsulation.
Initially films of 5 and 7 were irradiated in air with a 450 W
mercury lamp. However, total sample decomposition (verified
by UV/Vis spectroscopy) and loss of emission were observed
within 5 min. These data suggested that the light source was
too strong to obtain the requisite comparative data, therefore
subsequent photostability trials were conducted with the 65 W
xenon lamp found within our fluorimeter. We calculated the
percent fluorescence intensity and the I/I ratio based on the
0
Figure 4. Time dependence of the fluorescence emission intensity of drop-
photoluminescence intensity at lmax. The data presented in
Figure 4 shows that SGG 5 displays enhanced photostability in
relation to fluorene analogue 7 in the solid state: 42% reten-
tion of the emission intensity in 5 versus 26% retention in 7
after 40 min exposure. We also compared the photobleaching
of 5 and 7 in the film state to that obtained in solution in THF
cast thin films of 5 (*) and 7 (
) upon exposure to a 65 W mercury lamp in
&
air.
were irradiated with a 450 W mercury lamp for 10 min SGG 5
retained only 71% of its initial emission intensity, whereas fluo-
rene 7 maintained 94% of its initial photoluminescence. These
initial photobleaching experiments reveal that although the re-
ported SGGs have similar emission abilities to known fluorenes,
they can exhibit improved photo-oxidative stability in the solid
À5
[16]
(
c=1.8”10 m; Figure S24 in the Supporting Information).
For these solution studies, the use of a 65 W xenon lamp as
the irradiation source did not lead to any noticeable photode-
gradation of either 5 or 7. However, when solutions of 5 and 7
Chem. Eur. J. 2016, 22, 248 – 257
www.chemeurj.org
250
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
state. Whether these differences are due to inherent chemical
stability or changes in film morphologies in the solid state re-
mains to be verified, and we are cautious about drawing gen-
eralizations from this preliminary study. We will soon conduct
a more comprehensive comparative photostability study (aug-
mented by computational studies) by using molecular spirocy-
cles that differ only by C-atom substitution with heavier
group 14 elements; fortunately the modular synthetic routes
outlined in this paper will enable us to accomplish this task.
In addition, the onset of thermal decomposition (5% weight
loss), Tdec, of 5 and 7 were evaluated under an argon atmos-
phere by TGA (Figure 5). Compound 5 began to decompose at
Scheme 4. Preparation of thiophene-substituted zirconocene 8, dihaloger-
mole 9, and SGG 10.
sitive zirconacycle 8 as a red solid. In a subsequent step, com-
pound 8 underwent metallacycle transfer with GeCl to yield
4
dichlorogermole 9 (see Figure S4 in the Supporting Informa-
[
16]
tion).
Compound 9 was converted into the target thio-
phene-decorated SGG 10 by treatment with 2,2’-dilithiobi-
phenyl (Scheme 4). Compound 10 is an air- and moisture-
stable yellow solid that is non-emissive in solution. However,
unlike 2, SGG 10 emits a bright-yellow color in the solid state
(
lem =560 nm) due to the restricted rotation of the peripheral
thiophene groups. SGG 10 forms emissive aggregated states
in THF/water mixtures when the water content exceeds
7
0% v/v (Figure 6). A luminescence lifetime of t=3.22 ns was
Figure 5. TGA thermograms of 5 (c) and 7 (a) measured under an Ar
atmosphere (108Cmin ) air.
À1
Tdec =3198C, which is somewhat higher than observed for bis-
(
thienyl)dioctylfluorene 7 (Tdec =2908C). These early results are
encouraging and indicate a high degree of thermal stability
[5]
within the SGG molecular construct.
The similar nature of the emission profiles between the
abovementioned SGGs 4 and 5 and their related organic fluo-
rene counterparts 6 and 7 point towards a non-emissive
nature of the fused tetraethylgermole cores in 4 and 5. A pos-
sible explanation is that inherently high degrees of free rota-
tion are available to the ethyl group, which encourages non-ra-
[22]
diative decay processes.
Thus, we prepared an analogous
SGG, FlGeC (2-thienyl) (10; Scheme 4) that contained thio-
4
4
phene units around the germole core. Motivation for this mo-
lecular design also came from prior work on emissive metal-
[7e,23]
loles that contained aromatic side groups,
and a desire to
demonstrate an improved method of placing potentially light-
[4a–c,24]
harvesting thiophene groups about a metallole ring.
It is
expected that the disruption of intermolecular interactions and
restrictive intramolecular motion within the flanking thiophene
units could suppress non-radiative decay pathways and en-
[
4d,8b]
hance AIE,
which would make the resulting SGGs efficient
emitters in the solid state. Kafafi and co-workers constructed
an efficient green LED based on highly emissive (F=0.87) spi-
rocyclic silafluorene–silole that contained linked silafluorene
[25]
Figure 6. a) Photoluminescence (PL) spectra of SGG 10 in solution in THF/
water mixtures. b) Emission intensity of SGG 10 as the THF/water ratio is al-
tered. Inset: the aggregates viewed under UV light (lex. =365 nm);
[10]ꢀ10À4 m.
and tetraphenylsilole units.
The synthetic route to 10 first involved alkyne coupling of
two bis(2-thienyl)alkyne units to “Cp Zr” to yield moisture-sen-
2
Chem. Eur. J. 2016, 22, 248 – 257
www.chemeurj.org
251
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
found for pure films of 10 drop-coated from a solution of 10
in THF (absolute F=0.021), which indicated that the light
[16]
emission is fluorescence. Also, the emission band was repro-
ducibly blueshifted in 70% v/v water in THF by about 20 nm
relative to aggregates in solutions with a higher percentage of
water. A pronounced shift of l was not found during AIE of
em
[10]
our tellurophene phosphors, however significant changes in
lem as a function of the degree of aggregation has been noted
in related systems based on silicon heterocycles and was at-
tributed to conformational changes within the flexible side
[
8e]
groups upon increasing aggregation.
Scheme 5. Synthesis of dihalogermole 11 and BPin-capped SGG 12. Suzuki–
Miyuara coupling of 12 to obtain thiophene-capped SGG 13.
Crystals of 10 suitable for X-ray crystallographic analysis
were obtained from solution in CH Cl /hexanes and revealed
2
2
the expected perpendicular arrangement between the fused
germafluorene and germole units (Figure 7). Interestingly, the
yield of 85% (Scheme 5). Subsequent incorporation of a fluo-
rene unit at Ge to give SGG 12 was achieved by combining 11
[
26]
with 2,2’-dilithiobiphenyl generated in situ.
The structures of 11 (Figure S6 in the Supporting Informa-
[
16]
tion) and 12 (Figure 8) were determined by single-crystal X-
Figure 7. Thermal-ellipsoid plot (30% probability) of SGG 10 with hydrogen
atoms omitted for clarity; only the major orientation of the disordered thien-
yl group is shown. Selected bond lengths [Š] and angles [8]: GeÀC(1)
1
.938(2), Ge-ÀC(12) 1.928(2), GeÀC(13) 1.947(19), GeÀC(16) 1.943(2); C(12)-
Ge-C(1) 89.99(9), C(13)-Ge-C(16) 90.26(9).
Figure 8. Thermal-ellipsoid plot (30% probability) of 12 with hydrogen
atoms omitted for clarity. Selected bond lengths [Š] and angles [8] (values
due to the disordered BPin group are given in square brackets): GeÀC(1)
thiophene substituents closest to the germafluorene array
(
germole 2,5-positions) lie almost co-planar with respect to the
1
.9488(14), GeÀC(8) 1.9345(14), GeÀC(32) 1.9469(15), GeÀC(21) 1.9391(15),
germole GeC ring, whereas the remaining thiophene groups
B(1)ÀO(1) 1.360(3) [1.392(5)], B(1)ÀO(2) 1.365(3) [1.369(6)], B(2)ÀO(3)
4
are significantly tilted (by 83.62(5)8); the GeÀC bond lengths
are similar to those observed for the abovementioned SGGs 2,
1.3706(19); C(1)-Ge-C(8) 90.96(6), C(21)-Ge-C(32) 89.11(7), O(3)-B(2)-O(4)
112.33(14), O(1)-B(1)-O(2) 113.41(18) [109.9(3)].
3
, and 5.
Compound 10 absorbs at lmax =434 nm in THF, which is red-
shifted relative to alkylated SGG 2 (lmax =276 nm); this is most
likely to be a direct result of the conjugated thienyl units pres-
ent in 10. In addition, 10 is thermally stable up to Tdec =2388C,
whereas Tdec =2078C for the ethyl-substituted congener 2. In-
terestingly, 10 should be amenable to further postfunctionali-
zation, such as selective halogenation or lithiation of the pe-
ripheral thiophene groups, which would enable the construc-
tion of extended structures and polymers containing 10 as a lu-
minescent core unit.
ray crystallography. As noted for previously reported BPin-sub-
[
10]
stituted tellurophenes, the flanking BPin groups in 12 are ar-
ranged in a slightly twisted fashion relative to the central met-
allole ring (by about 12.58 to 14.58). However, in contrast to
the BPin-capped tellurophenes, which are phosphorescent in
the solid state, compound 12 is non-emissive both in solution
and in the condensed phase. To verify if the BPin groups
caused the luminescence quenching we explored the coupling
of 12 with 2-bromothiophene to yield SGG 13, in which the
BPin groups are replaced by aromatic residues.
Given our prior experience of using Suzuki–Miyaura cross-
[10a]
couplings to yield metallole-based polymers
(e.g., polytel-
Under unoptimized Suzuki–Miyaura cross-coupling condi-
[
27]
lurophenes), we prepared an SGG containing pinacolborane
tions, we obtained 13 with a crude yield of 60% (Scheme 5).
After rigorous purification, pure 13 was obtained as a yellow
solid that absorbs at lmax =423 nm in solution in THF; which is
comparable to tetrathienyl-substituted SGG 10 (lmax =434 nm).
(
BPin) groups. Specifically we combined the known pinacolbor-
[10a,b]
ane-capped zirconacycle precursor B-Zr-6-B
with excess
GeCl to generate halogermole 11 as a yellow solid with a high
4
Chem. Eur. J. 2016, 22, 248 – 257
www.chemeurj.org
252
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Compound 13 exhibits green luminescence in solution in THF
F=0.058). Therefore, it appears that in these SGGs the pres-
(Ace Glass Inc., Vineland, NJ, USA). Photobleaching experiments on
films were performed with a PTI MP1 fluorescence system (65 W
xenon lamp).
(
ence of flanking BPin group has a quenching effect (as seen
for 12). After optimization of the reaction conditions, the use
of 12 as a co-monomer for future polymerization trials will be
explored.
Synthetic procedures
Compound 1: Compound 1 was synthesized by modification of
[12]
a known procedure. GeCl (138 mL, 1.2 mmol) was added to a so-
4
Conclusion
lution of Cp ZrC Et (0.390 g, 1.0 mmol) in THF (10 mL) at room
2 4 4
temperature, and the mixture was stirred overnight to give a pale-
yellow solution. The volatile compounds were removed under
vacuum and the product was extracted with hexanes (10 mL). The
extract was filtered through a 1 cm plug of silica gel, and the sol-
vent was evaporated under reduced pressure to give 1 (0.265 g,
We prepared a series of light-emitting, thermally stable SGGs
by metallacycle transfer and microwave-assisted Stille or
Suzuki–Miyaura cross-couplings. By altering the nature of the
peripheral substituents photoluminescence from the optically
active germafluorene and germole units could be turned on or
off, which led to blue, green, and orange-yellow emission.
Future work will involve the attempted preparation of “on/on”
8
5%) as a colorless oil, which was used without further purifica-
1
13
1
tion. The corresponding H and C{ H} NMR spectral data matched
[12]
those reported previously by the Tilley group.
Compound 2: solution of 2,2’-dibromobiphenyl (0.177 g,
.57 mmol) in Et O (6 mL) was cooled to À358C, and nBuLi
[15]
A
dual-emission molecular SGGs, with particular attention paid
to obtaining white-light emission within molecular or polymer-
ic frameworks.
0
2
(
454 mL, 2.5m in hexanes, 1.1 mmol) was added dropwise. The re-
action mixture immediately became yellow and was stirred for 3 h
at room temperature. The mixture, which contained dilithiobiphen-
yl, was cooled to À358C. A solution of 1 (0.175, 0.57 mmol) in Et O
2
Experimental Section
(4 mL) was added then the mixture was stirred for 12 h at room
temperature, and a pale-yellow solution formed over a white pre-
cipitate. The precipitate was allowed to settle and the yellow
mother liquor was filtered through Celite. The solvent was re-
moved from the filtrate under vacuum to yield crude 2 (0.203 g,
Materials and instrumentation
General: All reactions were performed by using standard Schlenk
and glovebox (MBraun) techniques under a nitrogen atmosphere.
Solvents were all dried and degassed by means of a Grubbs-type
9
2%) as a yellow oil, which solidified upon standing. The product
[28]
was purified by column chromatography (silica gel, hexanes). Cool-
solvent-purification system
(Innovative Technology, Inc.), and
ing a saturated solution of 2 in hexanes to À308C resulted in the
stored under a nitrogen atmosphere prior to use. 1,7-Octadiyne
and 2,2’-bipyridine were obtained from GFS Chemicals, germanium
tetrachloride and zirconocene dichloride from Strem Chemicals
Inc., and 1,2-dibromobenzene from Alfa Aesar; all other chemicals
were obtained from Sigma–Aldrich. Commercially obtained chemi-
formation of colorless crystals of 2 (0.135 g, 61%) suitable for X-ray
1
crystallography. M.p. 80–828C (melts); H NMR (400 MHz, CDCl ):
3
3
3
d=7.91 (d, J(H,H)=7.9 Hz, 2H; ArH), 7.55 (d, J(H,H)=7.2 Hz, 2H;
ArH), 7.42 (td, J(H,H)=7.6 Hz, J(H,H)=1.3 Hz, 2H; ArH), 7.25 (td,
J(H,H)=7.2 Hz, J(H,H)=0.9 Hz, 2H; ArH), 2.41 (q, J(H,H)=7.6 Hz,
4H; CH CH ), 2.26 (q, J(H,H)=7.5 Hz, 4H; CH CH ), 1.11 (t, J(H,H)=
2 3 2 3
7.5 Hz, 6H; CH CH ), 0.68 ppm (t, J(H,H)=7.5 Hz, 6H; CH CH );
2 3 2 3
C{ H} NMR (100 MHz, CDCl ): d=153.2, 146.9, 137.5, 135.8, 133.5,
3
3
4
3
4
3
[26a]
[12]
cals were used as received. 2,2’-Dibromobiphenyl,
Cp ZrC Et ,
2
4
4
[18]
3
3
[29]
4
,4’-dibromo-2,2’-di-iodobiphenyl, trimethylstannylbenzene, 2-
3
[19]
[30]
trimethylstannylthiophene,
tributylstannylthiophene,
1,2-di-
13
1
[
31]
[32]
(
thiophen-2-yl)ethyne,
2,5-dibromothiophene,
9,9’-dioctyl-2,7-
[33]
[10a]
129.5, 127.6, 121.6 (Fl-C and Ar-C), 23.5, 21.4 (CH CH ), 15.9,
2 3
dibromofluorene, and B-Zr-6-B
literature procedures. H, C{ H}, and B{ H} NMR spectra were re-
corded with a Varian DD2 MR-400 spectrometer and were refer-
were prepared according to
1
13
1
11
1
15.1 ppm (CH CH ); UV/Vis (THF): lmax (e)=276 nm (1.42”
2 3
4
À1
3
À1
1
0 mol dm cm ); HRMS (EI): m/z calcd for C H Ge: 390.1403;
24 28
+
1
13
1
found: 390.1405 [M] ; elemental analysis calcd (%) for C H Ge: C
enced externally to SiMe4 ( H and C{ H} NMR) or F3B·OEt2
24 28
11
74.08, H 7.25; found: C 73.61, H 7.29.
(
B NMR). Elemental analyses were performed by the Analytical
and Instrumentation Laboratory at the University of Alberta. Small
molecule mass spectra were collected by using a MS-50G system
Compound 3: A solution of 4,4’-dibromo-2,2’-diiodobiphenyl
(1.967 g, 3.5 mmol) in Et O (20 mL) was precooled to À788C and
2
(
Kratos Analytical). Melting points were recorded in sealed glass ca-
nBuLi (2.8 mL, 2.5m in hexanes, 7.0 mmol) was added dropwise
over 1 h. The mixture was stirred for an additional 1 h at À788C,
and then a precooled (À788C) solution of 1 (1.074 g, 3.5 mmol) in
pillary tubes under a nitrogen atmosphere with a MelTemp melt-
ing-point apparatus and are uncorrected. UV/Vis measurements
were performed with a Varian Cary 300 Scan spectrophotometer.
The fluorescence measurements were conducted with a Photon
Technology International (PTI) MP1 fluorescence system. All solu-
tion quantum yields were measured relative to quinine sulfate in
Et O (15 mL) was added. The mixture was warmed to room tem-
2
perature and stirred for 12 h. The mixture was diluted with Et O
2
(50 mL) then washed with water (100 mL) and brine (100 mL), and
the isolated organic layer was dried over MgSO . The solvent was
4
[34]
1
n H SO by assuming F=0.55.
Photoluminescence lifetimes
removed under vacuum to give crude 3 (1.105 g, 58%) as a color-
less solid. Colorless crystals of 3 (0.770 g, 40%) suitable for X-ray
crystallography were obtained by slow cooling a warm (ꢀ408C)
2
4
were measured on a time-correlated single-photon-counting fluo-
rescence spectrometer (Edinburgh Instruments FLS920) equipped
with an EPL-375 picosecond pulsed diode laser with vertical polari-
zation (70.3 ps pulse width) as an excitation source; absolute quan-
tum yields were measured with an integrating sphere system
within the same spectrometer. Microwave reactions were per-
formed in a Biotage Initiator Classic microwave reactor (Biotage,
LLC, Charlotte, NC, USA). Photobleaching experiments in solution
were performed by using an Ace-Hanovia 450 W mercury lamp
1
solution of 3 in hexanes to 08C. M.p. 192–1948C (melts); H NMR
3
(400 MHz, CDCl ): d=7.71 (d, J(H,H)=8.2 Hz, 2H; ArH), 7.64 (d,
3
3
3
4
J(H,H)=2.0 Hz, 2H; ArH), 7.54 (dd, J(H,H)=8.5 Hz, J(H,H)=1.9 Hz,
2H; ArH), 2.39 (q, J(H,H)=7.5 Hz, 4H; CH CH ), 2.25 (q, J(H,H)=
7.5 Hz, 4H; CH CH ), 1.10 (t, J(H,H)=7.5 Hz, 6H; CH CH ), 0.67 ppm
(t, J(H,H)=7.5 Hz, 6H; CH CH ); C{ H} NMR (100 MHz, CDCl ): d=
3
3
2
3
3
2
3
2
3
3
13
1
2
3
3
154.1, 144.7, 140.2, 136.0, 134.8, 132.7, 123.2, 122.7 (Fl-C and Ar-C),
Chem. Eur. J. 2016, 22, 248 – 257
www.chemeurj.org
253
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
2
3.4, 21.6 (CH CH ), 15.9, 15.0 ppm (CH CH ); UV/Vis (THF): l
max
Compound
7:
9,9’-Dioctyl-2,7-dibromofluorene
(0.307 g,
2
3
2
3
4
À1
3
À1
(e)=288 nm (2.11”10 mol dm cm ); HRMS (EI): m/z calcd for
0.56 mmol), 2-trimethylstannylthiophene (197 mL, 1.1 mmol), and
Pd(PPh3)4 (0.032 g, 0.028 mmol) were dissolved in THF (5 mL) in
a sealed 5 mL microwave vial. The solution was subjected to micro-
wave irradiation (70 min, 1408C), and then the crude product was
+
C H Br Ge: 545.9613; found: 545.9599 [M] ; elemental analysis
calcd (%) for C H Br Ge: C 52.71, H 4.79; found: C 52.53, H 4.82.
24
26
2
2
4
26
2
Compound 4: Compound 3 (0.162 g, 0.30 mmol), trimethylstannyl-
benzene (108 mL, 0.61 mmol), and Pd(PPh ) (0.017 g, 0.015 mmol)
were dissolved in THF (3 mL) in a sealed microwave vial (5 mL).
The solution was subjected to microwave irradiation (70 min,
purified by column chromatography (silica gel, hexanes/THF=
3
4
1
2
0:1) to yield 7 (0.182 g, 59%) as a light green oil. H and
C{ H} NMR spectral data matched those reported previously by
1
3
1
[
20b,d]
the Leclerc group.
TGA: Tdec =2908C; HRMS (EI): m/z calcd for
1
408C) then the mixture was filtered. The volatile compounds
C H S : 554.3041; found: 554.3054; elemental analysis calcd (%)
37
46 2
were removed from the filtrate, and the residue was purified by
column chromatography (silica gel, hexanes/THF=20:1) to yield 4
for C H S : C 80.09, H 8.36, S 11.56; found: C 79.58, H 8.30, S
37
46 2
11.03.
(
0.050 g, 31%) as a spectroscopically pure white solid. Colorless
crystals of suitable quality for X-ray analysis were obtained by cool-
Compound 8: A solution of nBuLi (1.63 mL, 2.5m solution in hex-
ing a hexane/diethyl ether solution of 4 at À308C. M.p. 217–2208C
anes, 4.1 mmol) was added dropwise to a solution of [Cp ZrCl ]
2
2
1
3
(
melts); H NMR (400 MHz, CDCl ): d=8.01 (d, J(H,H)=8.0 Hz, 2H;
(0.610 g, 2.1 mmol) in THF (15 mL) at À788C The reaction mixture
was stirred at À788C for 1 h then a solution of 1,2-di(thiophen-2-
yl)ethyne (0.794 g, 4.2 mmol) in THF (15 mL) was added at À788C.
The temperature was allowed to rise to room temperature, and
the mixture was stirred for a further 24 h. The solvent was re-
moved under reduced pressure, the product was extracted with
toluene (25 mL), and the mixture was filtered through Celite. The
volatile compounds were evaporated under reduced pressure to
give crude 8 as an orange-red powder (1.080 g, 86%), which was
washed with cold hexanes (5 mL; À308C) to give a red solid
3
3
FlH), 7.84 (d, J(H,H)=1.7 Hz, 2H; FlH), 7.72–7.67 (m, 6H; FlH and
3
PhH), 7.46 (t, J(H,H)=7.6 Hz, 4H; PhH), 7.36 (m, 2H; PhH), 2.46 (q,
3
3
J(H,H)=7.5 Hz, 4H; CH CH ), 2.33 (q, J(H,H)=7.5 Hz, 4H; CH CH ),
2
3
2
3
3
3
1
6
1
.16 (t, J(H,H)=7.5 Hz, 6H; CH CH ), 0.76 ppm (t, J(H,H)=7.5 Hz,
2 3
H; CH CH ); C{ H} NMR (100 MHz, CDCl ): d=153.5, 145.8, 141.2,
40.3, 138.5, 135.8, 132.1, 128.8, 128.6, 127.2, 127.1, 122.0 (Fl-C and
1
3
1
2
3
3
Ph-C), 23.6, 21.5 (CH CH ), 16.0, 15.2 ppm (CH CH ); UV/Vis (THF):
2
3
2
3
4
À1
3
À1
lmax (e)=318 nm (6.28”10 mol dm cm ); fluorescence: l
=
em
3
77 nm (THF, lexcitation(ex) =332 nm); F=0.03, relative to quinine sul-
1
fate in 1.0n H SO ; HRMS (EI): m/z calcd for C H Ge: 542.2029;
(0.913 g, 73%). M.p. 145–1488C (decomp., turns brown); H NMR
2
4
36 36
+
3
4
found: 542.2021 [M] ; elemental analysis calcd (%) for C H Ge: C
(400 MHz, CDCl ): d=7.12 (dd, J(H,H)=5.0 Hz, J(H,H)=1.0 Hz, 2H;
36
36
3
3
4
7
9.88, H 6.70; found: C 79.66, H 6.82.
thienylH), 7.04 (dd, J(H,H)=5.1 Hz, J(H,H)=1.0 Hz, 2H; thienylH),
.79–6.76 (m, 4H; thienylH), 6.50 (dd, J(H,H)=3.3 Hz, J(H,H)=
.0 Hz, 2H; thienylH), 6.41 (s, 10H; CpH), 5.87 ppm (dd, J(H,H)=
.6 Hz, J(H,H)=1.1 Hz, 2H; thienylH);
3
4
6
1
3
Compound 5: Compound 3 (0.162 g, 0.30 mmol), 2-trimethylstan-
nylthiophene (104 mL, 0.59 mmol), and Pd(PPh3)4 (0.012 g,
3
4
13
1
C{ H} NMR (100 MHz,
0
.011 mmol) were dissolved in THF (3 mL) in a sealed 5 mL micro-
wave vial. The solution was subjected to microwave irradiation
70 min, 1408C) then the volatile compounds were removed under
CDCl ): d=185.7, 148.9, 142.6, 137.0, 127.8, 126.3, 126.0, 125.4,
3
1
4
25.0, 124.0 (thienyl-C), 112.2 ppm (Cp); UV/Vis (THF): l
22 nm (9.09”10 mol dm cm ); HRMS (MALDI): m/z calcd for
(e)=
max
(
3
À1
3
À1
vacuum, and the crude product was purified by column chroma-
tography (silica gel, hexanes/THF=20:1) to give 5 (0.017 g, 14%)
as a white solid. Colorless crystals of 5 of suitable quality for X-ray
analysis were obtained by cooling a hot (408C) hexanes solution of
C H S Zr: 599.9662; found: 599.9646; elemental analysis calcd (%)
30
22 4
for C H S Zr: C 59.86, H 3.68, S 21.30; found: C 59.32, H 3.92, S
30
22 4
1
9.26.
5
to room temperature. M.p. 209–2128C (melts); TGA: T =3198C;
Compound 9: GeCl (99 mL, 0.87 mmol) was added to a dark-red
dec
4
1
3
H NMR (400 MHz, CDCl ): d=7.89 (d, J(H,H)=8.1 Hz, 2H; FlH),
solution of 8 (0.349 g, 0.58 mmol) in THF (10 mL) at room tempera-
ture, and the mixture was stirred overnight to give a light-red solu-
tion. The solvent was removed under vacuum, and the product
was extracted with hexanes (50 mL) by means of a Soxhlet appara-
tus for 1 h. The solvent was evaporated under reduced pressure to
afford 9 (0.267 g, 88%) as an orange solid. Orange crystals of 8
suitable for X-ray analysis were obtained upon recrystallization
3
4
3
7
.82 (d, J(H,H)=1.9 Hz, 2H; FlH), 7.69 (dd, J(H,H)=8.1 Hz,
4
3
4
J(H,H)=1.9 Hz, 2H; FlH), 7.37 (dd, J(H,H)=3.6 Hz, J(H,H)=1.2 Hz,
3
4
2
H; thienylH), 7.29 (dd, J(H,H)=5.1 Hz, J(H,H)=1.2 Hz, 2H; thie-
3
4
nylH), 7.09 (dd, J(H,H)=5.1 Hz, J(H,H)=3.6 Hz, 2H; thienylH), 2.46
3
3
(
q, J(H,H)=7.5 Hz, 4H; CH CH ), 2.32 (q, J(H,H)=7.5 Hz, 4H;
2 3
3
3
CH CH ), 1.17 (t, J=7.5 Hz, 6H; CH CH ), 0.74 ppm (t, J=7.5 Hz,
2
3
2
3
1
3
1
6
1
H; CH CH ); C{ H} NMR (100 MHz, CDCl ): d=153.6, 145.8, 144.6,
from Et O/hexanes at room temperature (0.091 g, 30%). M.p. 170–
2
3
3
2
1
38.6, 135.7, 133.6, 130.7, 128.1, 127.4, 124.7, 123.1, 122.0 (Fl-C,
1738C (decomp. to a dark-red oil); H NMR (400 MHz, CDCl ): d=
7.48 (dd, J(H,H)=3.7 Hz, J(H,H)=1.1 Hz, 2H; thienylH), 7.40 (dd,
J(H,H)=5.1 Hz, J(H,H)=1.2 Hz, 2H; thienylH), 7.23 (dd, J(H,H)=
5.1 Hz, J(H,H)=1.2 Hz, 2H; thienylH), 7.00 (m, 4H; thienylH),
6.87 ppm (dd, J(H,H)=3.5 Hz, J(H,H)=1.2 Hz, 2H; thienylH);
C{ H} NMR (100 MHz, CDCl ): d=139.5, 138.0, 135.5, 131.5, 129.4,
3
3
3
4
thienyl-C, and Ar-C), 23.6 (CH CH ), 21.6 (CH CH ), 15.9 (CH CH ),
2
3
2
3
2
3
3
4
3
1
1
5.1 ppm (CH CH ); UV/Vis (THF): lmax (e)=355 nm (4.92”
0 mol dm cm ); fluorescence: l =386 and 407 nm (THF,
2
3
À1
4
À1
3
4
em
3
4
l =348 nm); F=0.83, relative to quinine sulfate in 1.0n H SO ;
ex
2
4
À5
13
1
t=0.94 ns (c=1”10
C H GeS : 554.1157; found: 554.1161 [M] ; elemental analysis
calcd (%) for C H GeS : C 69.46, H 5.83, S 11.59; found: C 69.59, H
m
in THF); HRMS (EI): m/z calcd for
+
129.2, 128.5, 128.1, 127.5, 126.8 ppm (thienyl-C); UV/Vis (THF): l
max
32
32
2
4
À1
3
À1
(e)=452 nm (1.51”10 mol dm cm ); HRMS (MALDI): m/z calcd
for C H Cl GeS : 523.8411; found: 523.8396. Compound 9 was
3
2
32
2
5
.71, S 11.56.
Alternate preparation of 5 from 2-tributylstannylthiophene:
Compound (0.102 g, 0.19 mmol), 2-tributylstannylthiophene
119 mL, 0.38 mmol), and Pd(PPh ) (0.011 g, 0.009 mmol) were dis-
20
12
2
4
typically contaminated with [Cp ZrCl ] (5–10%) due to their similar
2
2
solubilities. As a result, crude 9 was used in subsequent reactions.
3
(
Compound 10: solution of 2,2’-dibromobiphenyl (0.109 g,
A
3
4
solved in THF (3 mL) in a sealed 5 mL microwave vial. The solution
was subjected to microwave irradiation (70 min, 1408C) then the
volatile compounds were removed under reduced pressure and
the remaining product was purified by column chromatography
0.35 mmol) in Et O (4 mL) was cooled to À358C and nBuLi (279 mL,
2
2.5m solution in hexanes, 0.70 mmol) was added dropwise. The
mixture immediately turned yellow and was stirred for 3 h at room
temperature. The mixture (containing 2,2’-dilithiobiphenyl) was
(
silica gel, hexanes/THF=20:1) to give 5 (0.053 g, 51%) as a white
cooled to À358C then a solution of 9 (0.183 g, 0.35 mmol) in Et O
2
solid.
(9 mL) was added. The reaction mixture was stirred for 12 h, during
Chem. Eur. J. 2016, 22, 248 – 257
www.chemeurj.org
254
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
which time a dark-orange solution formed over a precipitate. The
precipitate was allowed to settle, and the mother liquor was fil-
tered through silica gel. The volatile compounds were evaporated
from the mother liquor under reduced pressure and cold (À308C)
acetone (5 mL) was added to yield a yellow solid (0.040 g, 19%).
The crude product was extracted with CH Cl (10 mL), the volatile
compounds were evaporated under reduced pressure, and then
cold (À308C) acetone (3 mL) was added to afford 10 as a yellow
solid. The supernatant was decanted and the volatile compounds
were evaporated under reduced pressure to yield a second crop of
THF=10:1) and slow evaporation of a solution of 12 in hexanes/
THF at room temperature gave colorless crystals of 12 (0.114 g,
1
35%) suitable for X-ray analysis. M.p. 189–1938C (melts); H NMR
3
(400 MHz, C D ): d=7.76 (d, J(H,H)=7.6 Hz, 2H; ArH), 7.62 (d,
6
6
3
3
J(H,H)=7.2 Hz, 2H; ArH), 7.18 (t, J(H,H)=7.6 Hz, 2H; ArH), 7.05 (t,
J(H,H)=7.6 Hz, 2H; ArH), 3.23 (m, 4H; C=CCH CH ), 1.60 (m, 4H;
C=CCH CH ), 0.82 ppm (s, 24H; CH ); C{ H} NMR (126 MHz, C D ):
2 2 3 6 6
3
2
2
2
2
13
1
d=169.9, 148.1, 137.0, 133.7, 129.6, 127.6, 121.9 (Fl-C and Ar-C),
82.6 (C(CH ) ), 32.7 (C=CCH CH ), 24.6 (CH3), 23.8 ppm (C=
3
2
2
2
1
1
CCH CH ); B NMR (128 MHz, C D ): d=30.8 ppm (brs); UV/Vis
2
2
6
4
6
À1
3
À1
1
0 (0.034 g, 16%). Recrystallization of the combined products 10
(THF): lmax (e)=312 nm (1.25”10 mol dm cm ); HRMS (EI): m/z
from a solution in CH Cl /hexanes at room temperature resulted in
calcd for C H B GeO : 584.2324; found: 584.2322; elemental anal-
2
2
32 40
2
4
the formation of yellow crystals (0.025 g, 12%) suitable for X-ray
analysis. M.p. 221–2238C (decomp., turns brown); TGA: T
ysis calcd (%) for C H B GeO : C 65.94, H 6.92; found: C 66.97, H
32 40 2 4
7.10.
=
dec
1
3
2
388C; H NMR (400 MHz, CDCl ): d=8.07 (d, J(H,H)=7.7 Hz, 2H;
3
3 4
Compound 13: Compound 12 (0.200 g, 0.34 mmol), 2-bromothio-
phene (73 mL, 0.75 mmol), cesium fluoride (0.313 g, 2.06 mmol),
and Pd(PPh ) (0.020 g, 0.017 mmol) were dissolved in acetonitrile
ArH), 7.82 (dd, J(H,H)=7.2 Hz, J(H,H)=0.6 Hz, 2H; ArH), 7.56 (m,
2
7
3
4
H; ArH), 7.39 (dd, J(H,H)=5.1 Hz, J(H,H)=1.1 Hz, 2H; thienylH),
3
4
3
4
.34 (m, 2H; ArH), 7.01 (dd, J(H,H)=5.1 Hz, J(H,H)=3.4 Hz, 2H;
(
4 mL) in a sealed 5 mL microwave vial. The solution was subjected
to microwave irradiation (40 min, 1408C), poured into water
100 mL), and extracted with CHCl (20 mL). The organic layer was
3
4
thienylH), 6.97 (dd, J(H,H)=5.0 Hz, J(H,H)=1.1 Hz, 2H; thienylH),
3
4
6
.92 (dd, J(H,H)=3.5 Hz, J(H,H)=1.1 Hz, 2H; thienylH), 6.56 (dd,
(
3
3
4
J(H,H)=5.1 Hz, J(H,H)=3.9 Hz, 2H; thienylH), 6.42 ppm (dd,
washed with water (100 mL) and brine (2”100 mL). The aqueous
fractions were combined and extracted with CHCl3 (10 mL) then
the organic layer was washed with brine (100 mL). The organic
3
4
13
1
J(H,H)=3.7 Hz,
J(H,H)=1.1 Hz, 2H; thienylH);
C{ H} NMR
(
100 MHz, CDCl ): d=146.4, 143.5, 141.5, 138.4, 135.7, 134.4, 131.9,
3
1
C
1
5
30.9, 130.0, 128.8, 128.6, 127.5, 127.4, 127.3, 126.3, 122.3 ppm (Ar-
and thienyl-C); UV/Vis (THF): lmax (e)=434 nm (2.59”
0 mol dm cm ); fluorescence: l (solid state, l =365 nm)=
em ex
layer was dried over MgSO then the solvent was removed under
4
reduced pressure and the residue was purified by column chroma-
4
À1
3
À1
tography (silica gel, hexanes/CH Cl =5:1) and washed with pen-
2
2
60 nm; F (solid state)=0.0208; t (solid state)=3.22 nm; HRMS
tane (2”5 mL) to give 13 (0.010 g, 6%) as a yellow solid. M.p.
(
MALDI): m/z calcd for C H GeS : 605.9660; found: 605.9647; ele-
1
3
2
20
4
1308C (decomp., turns brown); TGA: Tdec =2148C; H NMR
mental analysis calcd (%) for C H GeS : C 63.49, H 3.33, S 21.18;
3
3
2
20
4
(400 MHz, CDCl ): d=8.01 (d, J(H,H)=7.9 Hz, 2H; ArH), 7.61 (d,
3
found: C 60.07, H 3.89, S 20.18. Despite repeated attempts, com-
bustion analysis gave consistently low values for the carbon and
sulfur content. See Figures S8 and S9 in the Supporting Informa-
3
3
4
J(H,H)=7.3 Hz, 2H; ArH), 7.49 (td, J(H,H)=7.6 Hz, J(H,H)=1.1 Hz,
H; ArH), 7.25 (td, J(H,H)=7.3 Hz, J(H,H)=0.9 Hz, 7H; ArH, over-
laps with solvent peak), 7.14 (dd, J(H,H)=5.1 Hz, J(H,H)=0.7 Hz,
H; thienylH), 7.09 (dd, J(H,H)=5.1 Hz, J(H,H)=3.7 Hz, 2H; thi-
enylH), 6.45 (dd, J(H,H)=3.4 Hz, J(H,H)=0.7 Hz, 2H; thienylH),
2.94 (m, 4H; C=CCH CH ), 1.89 ppm (m, 4H; C=CCH CH );
C{ H} NMR (100 MHz, CDCl ): d=148.7, 146.6, 142.3, 136.5, 134.1,
3
4
2
3
4
[16]
tion for copies of the NMR spectra.
3
4
2
3
4
Compound 11: GeCl (253 mL, 2.2 mmol) was added to a solution
4
[10a]
2
2
2
2
of B-Zr-6-B
(0.827 g, 1.4 mmol) in THF (25 mL) at room tempera-
13
1
3
ture, and the mixture was stirred overnight to give a pale-yellow
solution. The solvent was removed under vacuum, the product
was extracted with hexanes (15 mL), and the extract was filtered
through a 1 cm plug of Celite. The solvent was evaporated from
the filtrate under reduced pressure to afford 11 as a yellow solid
1
30.4, 128.3, 127.7, 127.1, 125.5, 125.4, 122.0 (Fl-C, thienyl-C, and
Ar-C), 30.9 (C=CCH CH ), 23.2 ppm (C=CCH CH ); UV/Vis (THF): l
2
2
4
2
2
max
À1
3
À1
(
e)=423 nm (1.13”10 mol dm cm ); fluorescence: l
(THF,
em
lex =419 nm)=506 nm; F=0.058, relative to quinine sulfate in
.0N H SO ; HRMS (MALDI): m/z calcd for C H GeS : 496.0375;
1
2
4
28 22
2
(
0.610 g, 85%). Crystals of 11 (0.125 g, 16%) suitable for X-ray anal-
found: 496.0369; elemental analysis calcd (%) for C H GeS : C
28
22
2
ysis were obtained by recrystallization from hexanes at À358C.
1
67.91, H 4.48, S 12.95; found: C 67.08, H 4.89, S 11.76. Despite re-
peated attempts, combustion analysis gave consistently low values
for the sulfur content (by about 1%). See Figure S10 and S11 in
M.p. 124–1278C (melts); H NMR (400 MHz, C D ): d=2.85 (m, 4H;
6
6
C=CCH CH ), 1.24 (m, 4H; C=CCH CH ), 1.07 ppm (s, 24H; CH );
2
2
2
2
3
1
3
1
C{ H} NMR (126 MHz, C D ): d=166.7 (GeÀC=C), 83.6 (C(CH ) ),
6
6
3 2
[
16]
11
the Supporting Information for copies of the NMR spectra.
3
0.8 (C=CCH CH ), 24.8 (CH ), 22.4 ppm (C=CCH CH ); B NMR
2 2 3 2 2
(
(
160 MHz, C D ): d=29.5 ppm (brs); UV/Vis (THF): l (e)=327 nm
6
6
À1
max
3
3
À1
8.78”10 mol dm cm );
HRMS
(EI):
m/z
calcd
for
Acknowledgements
C H B Cl GeO : 502.1076; found: 502.1066; elemental analysis
20
32
2
2
4
calcd (%) for C H B Cl GeO : C 47.89, H 6.43; found: C 48.73, H
2
0
32
2
2
4
This work was supported by the Natural Sciences and Engi-
neering Research Council (NSERC) of Canada, the Canada
Foundation for Innovation, and Alberta Innovates-Technology
Futures (New Faculty Award to E.R.) We are also grateful to
Prof. Dr. Yu Fang (Key Laboratory of Applied Surface and Col-
loid Chemistry, Shaanxi Normal University) for his assistance
with the optical measurements. We also would like to thank
Dr. Wayne Moffat for useful discussions.
5
.90.
Compound 12:
A
solution of 2,2’-dibromobiphenyl (0.175 g,
0
2
.56 mmol) in Et O (6 mL) was cooled to À358C and nBuLi (449 mL,
2
.5m solution in hexanes, 1.1 mmol) was added dropwise. The mix-
ture immediately turned yellow and was stirred for 3 h at room
temperature. The mixture, which contained 2,2’-dilithiobiphenyl,
was cooled to À358C then a solution of 11 (0.281 g, 0.56 mmol) in
Et O (4 mL) was added. The mixture was stirred for 12 h, during
2
which time a pale-yellow solution formed over a white precipitate.
The precipitate was allowed to settle and the yellow mother liquor
was filtered through Celite. The solvent was evaporated from the
filtrate under vacuum to yield crude 12 as a yellow solid. The prod-
uct was purified by column chromatography (silica gel, hexanes/
Keywords: fluorescence · germafluorenes · germoles · solid-
state emission · spiro compounds
Chem. Eur. J. 2016, 22, 248 – 257
www.chemeurj.org
255
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[
1] a) T. Jüstel, H. Nikol, C. Ronda, Angew. Chem. Int. Ed. 1998, 37, 3084–
103; Angew. Chem. 1998, 110, 3250–3271; b) S. Reineke, M.
Thomschke, B. Lüssem, K. Leo, Rev. Mod. Phys. 2013, 85, 1245–1293;
c) H. Wu, L. Ying, W. Yang, Y. Cao, Chem. Soc. Rev. 2009, 38, 3391–3400;
d) B. W. D’Andrade, S. R. Forrest, Adv. Mater. 2004, 16, 1585–1595;
e) K. T. Kamtekar, A. P. Monkman, M. R. Bryce, Adv. Mater. 2010, 22, 572–
[10] a) G. He, L. Kang, W. Torres Delgado, O. Shynkaruk, M. J. Ferguson, R.
McDonald, E. Rivard, J. Am. Chem. Soc. 2013, 135, 5360–5363; b) G. He,
W. Torres Delgado, D. J. Schatz, C. Merten, A. Mohammadpour, L. Mayr,
M. J. Ferguson, R. McDonald, A. Brown, K. Shankar, E. Rivard, Angew.
Chem. Int. Ed. 2014, 53, 4587–4591; Angew. Chem. 2014, 126, 4675–
4679; c) G. He, B. D. Wiltshire, P. Choi, A. Savin, S. Sun, A. Mohammad-
pour, M. J. Ferguson, R. McDonald, S. Farsinezhad, A. Brown, K. Shankar,
E. Rivard, Chem. Commun. 2015, 51, 5444–5447; d) E. Rivard, Chem. Lett.
2015, 44, 730–736.
3
5
2
1
82; f) M. C. Gather, A. Kçhnen, K. Meerholz, Adv. Mater. 2011, 23, 233–
48; g) M. H. Crawford, IEEE J. Sel. Top. Quantum Electron. 2009, 15,
028–1040.
[
[
2] a) H. Jiang, J. Wan, W. Huang, Sci. China Ser. B: Chem. 2008, 51, 497–
20; b) M. Kuik, G. J. A. H. Wetzelaer, J. G. LaddØ, H. T. Nicolai, J. Wilde-
man, J. Sweelssen, P. W. M. Blom, Adv. Funct. Mater. 2011, 21, 4502–
509.
3] a) J. J. McDowell, I. Schick, A. Price, D. Faulkner, G. Ozin, Macromolecules
013, 46, 6794–6805; b) R. F. Chen, Q. L. Fan, S. J. Liu, R. Zhu, K. Y. Pu,
[11] a) X. Yan, C. Xi, Acc. Chem. Res. 2015, 48, 935–946; b) T. Baumgartner, R.
RØau, Chem. Rev. 2006, 106, 4681–4727; c) Y. Matsumura, M. Ueda, K.
Fukuda, K. Fukui, I. Takase, H. Nishiyama, S. Inagi, I. Tomita, ACS Macro
Lett. 2015, 4, 124–127; d) W.-M. Zhou, I. Tomita, J. Inorg. Organomet.
Polym. 2009, 19, 113–117.
5
4
[12] W. P. Freeman, T. D. Tilley, L. M. Liable-Sands, A. L. Rheingold, J. Am.
Chem. Soc. 1996, 118, 10457–10468.
2
W. Huang, Synth. Met. 2006, 156, 1161–1167; c) G. Lu, H. Usta, C. Risko,
L. Wang, A. Facchetti, M. A. Ratner, T. J. Marks, J. Am. Chem. Soc. 2008,
[13] J. Linshoeft, E. J. Baum, A. Hussain, P. J. Gates, C. Näther, A. Staubitz,
Angew. Chem. Int. Ed. 2014, 53, 12916–12920; Angew. Chem. 2014, 126,
1
30, 7670–7685; d) K. L. Chan, S. E. Watkins, C. S. K. Mak, M. J. McKiern-
an, C. R. Towns, S. I. Pascu, A. B. Holmes, Chem. Commun. 2005, 5766–
768; e) K. Geramita, Y. Tao, R. A. Segalman, T. D. Tilley, J. Org. Chem.
010, 75, 1871–1887; f) K. H. Lee, J. Ohshita, D. Tanaka, Y. Tominaga, A.
13130–13134.
[
14] For a report of polygermoles and their use in bulk heterojunction solar
cells, see: a) N. Allard, R. Badrou A ¨ı ch, D. Gendron, P. L. T. Boudreault, C.
Tessier, S. Alem, S. C. Tse, Y. Tao, M. Leclerc, Macromolecules 2010, 43,
5
2
Kunai, J. Organomet. Chem. 2012, 710, 53–58; g) M. Saito, S. Imaizumi,
T. Tajima, K. Ishimura, S. Nagase, J. Am. Chem. Soc. 2007, 129, 10974–
2328–2333. For related studies involving dithienylgermole units, see:
b) J. Ohshita, M. Miyazaki, D. Tanaka, Y. Morihara, Y. Fujita, Y. Kunugi,
Polym. Chem. 2013, 4, 3116–3122; c) J. Ohshita, Y. M. Hwang, T.
Mizumo, H. Yoshida, Y. Ooyama, Y. Harima, Y. Kunugi, Organometallics
1
0975.
4] a) M. Katkevics, S. Yamaguchi, A. Toshimitsu, K. Tamao, Organometallics
998, 17, 5796–5800; b) O. Fadhel, D. Szieberth, V. Deborde, C. Lescop,
[
1
2011, 30, 3233–3236.
L. Nyulµszi, M. Hissler, R. RØau, Chem. Eur. J. 2009, 15, 4914–4924; c) T.
Benincori, V. Bonometti, F. De Angelis, L. Falciola, M. Muccini, P. R. Mussi-
ni, T. Pilati, G. Rampinini, S. Rizzo, S. Toffanin, F. Sannicolo, Chem. Eur. J.
[
[
15] Z. Xie, C. Chen, S. Xu, J. Li, Y. Zhang, S. Liu, J. Xu, Z. Chi, Angew. Chem.
Int. Ed. 2015, 54, 7181–7184; Angew. Chem. 2015, 127, 7287–7290.
16] See the Supporting Information for full details. CCDC 1416938 (2),
2
010, 16, 9086–9098; d) J. Luo, Z. Xie, J. W. Y. Lam, L. Cheng, H. Chen,
C. Qiu, H. S. Kwok, X. Zhan, Y. Liu, D. Zhu, B. Z. Tang, Chem. Commun.
001, 1740–1741.
1
1
416939 (3), 1416940 (5), 1416943 (9), 1416944 (10), 14169441 (11), and
416942 (12) contain the supplementary crystallographic data for this
2
paper. These data are provided free of charge by The Cambridge Crys-
tallographic Data Centre.
[
5] T. P. I. Saragi, T. Spehr, A. Siebert, T. Fuhrmann-Lieker, J. Salbeck, Chem.
Rev. 2007, 107, 1011–1065.
6] J. P. Amara, T. M. Swager, Macromolecules 2006, 39, 5753–5759.
7] a) R. Hu, N. L. C. Leung, B. Z. Tang, Chem. Soc. Rev. 2014, 43, 4494–4562;
b) J. Mei, Y. Hong, J. W. Y. Lam, A. Qin, Y. Tang, B. Z. Tang, Adv. Mater.
[
17] a) K. Ogawa, Y. Takeuchi, G. Manuel, R. Boukherroub, Acta Crystallogr.
Sect. C 1994, 50, 1337–1339; b) A. V. Zabula, B. S. Dolinar, R. West, J. Or-
ganomet. Chem. 2014, 751, 458–461.
[
[
[
[
[
18] T. Mutai, J.-D. Cheon, S. Arita, K. Araki, J. Chem. Soc. Perkin Trans. 2
2014, 26, 5429–5479; c) S. J. Toal, K. A. Jones, D. Magde, W. C. Trogler, J.
2
001, 1045–1050.
19] F. C¸ . Cebeci, H. Geyik, E. Sezer, A. Sezai Sarac, J. Electroanal. Chem. 2007,
10, 113–121.
Am. Chem. Soc. 2005, 127, 11661–11665; d) B. Dedeo g˘ lu, V. Aviyente,
A. S. Özen, J. Phys. Chem. C 2014, 118, 6385–6397; e) B. Dedeoglu, A.
Monari, T. Etienne, V. Aviyente, A. S. Özen, J. Phys. Chem. C 2014, 118,
6
20] a) S. Tirapattur, M. BelletÞte, N. Drolet, J. Bouchard, M. Ranger, M. Le-
clerc, G. Durocher, J. Phys. Chem. B 2002, 106, 8959–8966; b) M. Belle-
tÞte, J. F. Morin, S. BeauprØ, M. Ranger, M. Leclerc, G. Durocher, Macro-
molecules 2001, 34, 2288–2297; c) M. BelletÞte, J. F. Morin, S. BeauprØ,
M. Leclerc, G. Durocher, Synth. Met. 2002, 126, 43–51; d) S. Tirapattur,
M. BelletÞte, N. Drolet, M. Leclerc, G. Durocher, Macromolecules 2002,
2
3946–23953; f) H. Sohn, M. J. Sailor, D. Magde, W. C. Trogler, J. Am.
Chem. Soc. 2003, 125, 3821–3830; g) D. Ding, K. Li, B. Liu, B. Z. Tang,
Acc. Chem. Res. 2013, 46, 2441–2453; h) J. Ohshita, K. Murakami, D.
Tanaka, Y. Ooyama, T. Mizumo, N. Kobayashi, H. Higashimura, T. Naka-
nishi, Y. Hasegawa, Organometallics 2014, 33, 517–521; i) M. Saito,
Coord. Chem. Rev. 2012, 256, 627–636; j) M. Saito, M. Sakaguchi, T.
Tajima, K. Ishimura, S. Nagase, Phosphorus Sulfur Silicon Relat. Elem.
3
5, 8889–8895; e) M. BelletÞte, S. BeauprØ, J. Bouchard, P. Blondin, M.
Leclerc, G. Durocher, J. Phys. Chem. B 2000, 104, 9118–9125.
2010, 185, 1068–1076; k) D. Yan, J. Mohsseni-Ala, N. Auner, M. Bolte,
[21] A. P. Ghosh, L. J. Gerenser, C. M. Jarman, J. E. Fornalik, Appl. Phys. Lett.
J. W. Bats, Chem. Eur. J. 2007, 13, 7204–7214; l) J. L. Mullin, H. J. Tracy,
in Aggregation-Induced Emission: Fundamentals and Applications, Vol. 1
and 2 (Eds. A. Qin and B. Z. Tang), Wiley, Hoboken, 2013, Chapter 2.
8] a) Z. Li, Y. Dong, B. Mi, Y. Tang, M. Häussler, H. Tong, Y. Dong, J. W. Y.
Lam, Y. Ren, H. H. Y. Sung, K. S. Wong, P. Gao, I. D. Williams, H. S. Kwok,
B. Z. Tang, J. Phys. Chem. B 2005, 109, 10061–10066; b) Y. Hong, J. W. Y.
Lam, B. Z. Tang, Chem. Soc. Rev. 2011, 40, 5361–5388; c) J. Liu, J. Y. Lam,
B. Tang, J. Inorg. Organomet. Polym. 2009, 19, 249–285; d) J. Chen,
C. C. W. Law, J. W. Y. Lam, Y. Dong, S. M. F. Lo, I. D. Williams, D. Zhu, B. Z.
Tang, Chem. Mater. 2003, 15, 1535–1546; e) B. Chen, H. Nie, P. Lu, J.
Zhou, A. Qin, H. Qiu, Z. Zhao, B. Z. Tang, Chem. Commun. 2014, 50,
2
005, 86, 223503.
[
[
22] Y. Hong, J. W. Y. Lam, B. Z. Tang, Chem. Commun. 2009, 4332–4353.
23] a) K. Amro, S. Clement, P. Dejardin, W. E. Douglas, P. Gerbier, J.-M. Janot,
T. Thami, J. Mater. Chem. 2010, 20, 7100–7103; b) G. Zhang, F. Hu, D.
Zhang, Langmuir 2015, 31, 4593–4604.
[
[
[
[
24] T. Araki, A. Fukazawa, S. Yamaguchi, Angew. Chem. Int. Ed. 2012, 51,
5
484–5487; Angew. Chem. 2012, 124, 5580–5583.
25] L. C. Palilis, H. Murata, M. Uchida, Z. H. Kafafi, Org. Electron. 2003, 4,
13–121.
1
26] a) T. K. Dougherty, K. S. Y. Lau, F. L. Hedberg, J. Org. Chem. 1983, 48,
5273–5280; b) C. J. Berger, G. He, C. Merten, R. McDonald, M. J. Fergu-
son, E. Rivard, Inorg. Chem. 2014, 53, 1475–1486.
4
500–4503; f) T. C. Bozeman, K. A. Edwards, K. M. Fecteau, M. G. Ver-
de, Jr., A. Blanchard, D. L. Woodall, N. Benfaremo, J. R. Ford, J. L. Mullin,
C. K. Prudente, H. J. Tracy, J. Inorg. Organomet. Polym. 2011, 21, 316–
[27] For a recent example that illustrates the high sensitivity of Suzuki–
Miyaura coupling to catalyst/base, see: A. W. Baggett, F. Guo, B. Li, S. Y.
Liu, F. Jäkle, Angew. Chem. Int. Ed. 2015, 54, 11191–11195; Angew. Chem.
2015, 127, 11343–11347.
[28] A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen, F. J. Timmers,
Organometallics 1996, 15, 1518–1520.
3
26; g) J. L. Mullin, H. J. Tracy, J. R. Ford, S. R. Keenan, F. Fridman, J.
Inorg. Organomet. Polym. 2007, 17, 201–213; h) H. J. Tracy, J. L. Mullin,
W. T. Klooster, J. A. Martin, J. Haug, S. Wallace, I. Rudloe, K. Watts, Inorg.
Chem. 2005, 44, 2003–2011.
[
9] a) P. J. Fagan, W. A. Nugent, J. Am. Chem. Soc. 1988, 110, 2310–2312;
b) E. Negishi, F. E. Cederbaum, T. Takahashi, Tetrahedron Lett. 1986, 27,
[29] C. W. Keyworth, K. L. Chan, J. G. Labram, T. D. Anthopoulos, S. E. Watkins,
M. McKiernan, A. J. P. White, A. B. Holmes, C. K. Williams, J. Mater. Chem.
2011, 21, 11800–11814.
2
829–2832.
Chem. Eur. J. 2016, 22, 248 – 257
www.chemeurj.org
256
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[
[
[
30] S. Gçker, G. Hızalan, Y. A. Udum, L. Toppare, Synth. Met. 2014, 191, 19–
7.
[33] S. J. Liu, Q. Zhao, R. F. Chen, Y. Deng, Q. L. Fan, F. Y. Li, L. H. Wang, C. H.
Huang, W. Huang, Chem. Eur. J. 2006, 12, 4351–4361.
[34] D. F. Eaton, Pure Appl. Chem. 1988, 60, 1107–1114.
2
31] M. J. Mio, L. C. Kopel, J. B. Braun, T. L. Gadzikwa, K. L. Hull, R. G. Brisbois,
C. J. Markworth, P. A. Grieco, Org. Lett. 2002, 4, 3199–3202.
32] J. Yu, T. L. Shen, W. H. Weng, Y. C. Huang, C. I. Huang, W. F. Su, S. P. Rwei,
K. C. Ho, L. Wang, Adv. Energy Mater. 2012, 2, 245–252.
Received: August 26, 2015
Published online on November 25, 2015
Chem. Eur. J. 2016, 22, 248 – 257
www.chemeurj.org
257
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim