Peraryl Arsoles: Practical Synthesis, Electronic Structures, and Solid-State Emission Behaviors

Article abstract of DOI:10.1002/chem.201801589

2,3,4,5-Tetraaryl-1-phenylarsoles were synthesized by utilizing safely generated diiodophenylarsine and zirconacyclopentadienes. The obtained peraryl arsoles showed aggregation-induced emission (AIE), where intense emission was observed in the solid states (quantum yields up to 0.61), whereas the corresponding solutions were very weakly emissive. The optical and electronic properties were examined by experimental and computational methods. It was elucidated that the aryl groups at the 2,5-positions affected the frontier orbitals and the aromaticity of the arsole core. On the other hand, those at the 1,3,5-positions were perpendicular to the luminophore and effective for a restriction of aggregation-caused quenching. Because the lone pair of the arsenic atom has a sufficient coordination ability due to the low aromaticity of the arsole moiety, a gold(I) chloride complex of 1,2,3,4,5-pentaphenylarsole was synthesized. The complex formation caused a blue shift of the emission from the bare ligand. Interestingly, the complex showed luminescent mechanochromism; grinding the crystals with a blue emission (λ_em=445 nm) gave amorphous samples with a greenish–blue emission (λ_em=496 nm).

Full text of DOI:10.1002/chem.201801589

A Journal of
Accepted Article
Title: Peraryl Arsoles: Practical Synthesis, Electronic Structures, and
Solid-State Emission Behaviors
Authors: Hiroaki Imoto, Aya Urushizaki, Ikuo Kawashima, and Kensuke
Naka
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Peraryl Arsoles: Practical Synthesis, Electronic Structures, and
Solid-State Emission Behaviors
Hiroaki Imoto,[a] Aya Urushizaki,[a] Ikuo Kawashima[a] and Kensuke Naka[a]*
Abstract: 2,3,4,5-Tetraaryl-1-phenylarsoles were synthesized by
utilizing safely generated diiodophenylarsine and
bismole,[9] have been reported. Further diversity of introduced
elements will deepen understanding of heterole chemistry as
well as AIE phenomenon.
zirconacyclopentadienes. The obtained peraryl arsoles showed
aggregation induced emission (AIE), where intense emission was
observed in the solid states (quantum yield = up to 0.61) while their
solutions are very weakly emissive. The optical and electronic
properties were examined by experimental and computational
methods. It was elucidated that the aryl groups at the 2,5-positions
affected the frontier orbitals and aromaticity of the arsole core. On
the other hand, those at the 1,3,5-positions were perpendicular to
the luminophore, and effective for restriction of aggregation caused
quenching. Since the lone pair of the arsenic atom has sufficient
coordination ability due to the low aromaticity of the arsole moiety,
gold(I) chloride complex of 1,2,3,4,5-pentaphenylarsole was
synthesized. The complex formation caused blue-shift of the
emission from the bare ligand. Interestingly, the complex showed
luminescent mechanochromism; grinding the crystals with the blue
emission (445 nm) gave amorphous samples with greenish blue
emission (496 nm).
Recently, experimental studies of arsole have been resumed.
Arsole derivatives were synthesized half a century ago,[10] but
the synthetic routes initially used required volatile and toxic
precursors such as arsenic chlorides[10] and hydrides.[11] Thus,
experimental studies on arsoles had been gradually avoided,
and their optical and electronic properties had been examined
mainly in the field of theoretical chemistry.[12,13] Meanwhile, we
have developed game-changing practical synthetic strategies[14-
16]
for organoarsenic compounds utilizing cyclooligoarsines,[17]
which can be prepared from non-volatile inorganic precursors.
Organoarsenic radicals,[14] electrophiles,[15] and nucleophiles[16]
are efficiently generated in situ through cleavage of the As−As
bonds of the cyclooligoarsines. Especially, arsole skeletons can
be readily constructed utilizing diiodoarsines, which are
quantitatively generated from cyclooligoarsine and iodine
(Scheme
1a).[16,19-21]
Diarylarsoles,[19]
arsafluorenes,[16]
dithienoarsoles,[19] and arsole containing polymers[19a,20] have
been synthesized via substitution reactions with appropriate
nucleophiles. The obtained arsole derivatives with trivalent
arsenic atoms possessed high oxidative resistance in
comparison to the phosphorus analogues. Therefore, their
optical and electronic properties are widely tuned by changing
the electron state through reactions and coordination to the
arsenic atom.[18b,19b,20]
Introduction
Heterole, heteroatom-substituted cyclopentadiene, is one of the
most important motifs to utilize unique natures of elements.[1] For
more than a century, various kinds of heteroatoms have been
incorporated, and the resultant heteroles have contributed to the
diversity of functional organic chemistry. Heterole backbones
have been decorated in a number of manners to control their
electronic properties, stability, and reactivity.[2] Among heterole
derivatives, increasing attention has been given to the molecular
design in which all the corners of the five-membered ring are
substituted by aryl groups.[3-7] In 2001, Tang’s group proposed
aggregation induced emission (AIE) phenomenon of 1-methyl-
1,2,3,4,5-pentaphenylsilole.[3] Propeller-like motions of the aryl
groups consume the excitation energies and only very weak
emission is observed in solution, while these motions are frozen
in the aggregates and the bulky aryl groups circumvent
aggregation caused quenching (ACQ) of the emission.[4] After
this seminal work, AIE luminogens based on peraryl heteroles,
e.g., pyrrole,[5] thiophene,[6] phosphole,[7] tellurophene,[8] and
Scheme 1. Synthetic protocol of arsole derivatives via in-situ-generation of
diiodoarsine.
In this work, as part of our going researches on the practical
syntheses of functional organoarsenic compounds, 2,3,4,5-
tetraaryl-1-phenylarsoles were synthesized as the first examples
of
organoarsenic
AIE
luminogens
by
utilizing
zirconacyclopentadienes. Interestingly, we found that the
emission colors were varied through multiple ways. Chemical
modification and coordination to the luminophore finely tune the
frontier orbital energy levels to control the emission color.
Moreover, the gold(I) complex showed luminescent
mechanochromism. The optical and electronic properties were
investigated by experimental and computational methods.
[a]
Dr. H. Imoto, A. Urushizaki, I. Kawashima and Prof. Dr. K. Naka*
Faculty of Molecular Chemistry and Engineering, Graduate School
of Science and Technology
Kyoto Institute of Technology
Goshokaido-cho, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
E-mail: kenaka@kit.ac.jp
Supporting information for this article is given via a link at the end of
the document.
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Results and Discussion
Synthesis of 2,3,4,5-tetraaryl-1-phenylarsoles
The synthetic route of 1,2,3,4,5-pentaphenylarsole in 1959
employed lithium and dichlorophenylarsine,[9] which are
unfavourable from
a
viewpoint
of
safety. 2,3,4,5-
Tetraarylzirconacyclopentadienes are useful organometallic
reagents for syntheses of heteroles,[20] and Takahashi’s method
improved their nucleophilicity by transmetalation with copper(I)
chloride.[21] Herein, 2,3,4,5-tetraaryl-1-phenylarsoles were
synthesized as shown in Scheme 2. A THF solution of 2 was
prepared by addition of a THF solution of iodine to 1. Reaction of
p-substitued diarylacetylenes 3a-c with a low-valent zirconocene
species Cp2Zr(II) generated zirconacyclopentadienes, and
subsequently addition of copper(I) chloride offered 1,4-dicopper-
1,3-butadienes 4a-c in-situ. The solution of 2 was mixed with the
solutions of 4a-c to give 2,3,4,5-tetraaryl-1-phenylarsoles 5a-c,
Figure 1. ORTEP drawings and selected angles of 5a. Hydrogen atoms are
omitted for clarity. Thermal ellipsoids are drawn at the 50% probability level.
Optical and electronic properties
The UV-vis absorption spectra and photoluminescence (PL)
spectra of the obtained arsoles were measured (Table 1).[25] For
the comparison, these optical measurements of 1,2,5-
triphenylarsole 6 were cited from our previous paper.[18a] The
absorption and emission maxima of 5a-c slightly differ according
to the substituents on the four benzene rings. Density functional
theory (DFT) calculations showed that the highest occupied
molecular orbital (HOMO) of 5a was mainly localized at the 1,4-
diphenyl-1,3-butadiene moiety, while the lowest unoccupied
molecular orbital (LUMO) was expanded to the arsenic atom
through the *-* conjugation (Figure 2a). Therefore, the
substituents on the benzene rings more strongly affected the
HOMO level than the LUMO level. The electron donating methyl
(5b) and methoxy groups (5c) effectively raised their HOMO
levels, resulting in the red-shifted UV-vis and PL spectra. On the
other hand, the phenyl groups at the 3,4-positions of 5a hardly
contributed the -conjugation, compared with those at the 2,5-
positions. Since the frontier orbitals of 6 are located similarly to
those of 5a (Figure 2b), there was no significant difference in
absorption and emission maxima between 5a and 6.
1
respectively. Their chemical structures were determined by H-
and 13C{1H}-NMR spectroscopy, and high resolution mass
spectra (HRMS).
Scheme 2. Synthesis of 2,3,4,5-tetraaryl-1-phenylarsoles 5a-c.
The lifetimes of the solid-state emission (Figure S14) were
3.33 ns (5a), 2.06 ns (5b), and 3.00 ns (5c). In addition, no
significant change in the PL spectrum was observed when the
solid sample of 5a was subjected to the PL measurement under
A
single crystal of 5a suitable for X-ray diffraction
measurement was obtained by slow mixing of
a
dichloromethane (CH2Cl2) solution and methanol (MeOH). The
structure of 5a is shown in Figure 1, and selected parameters
are summarized in Tables S2 and S3.[22] The arsenic atom has a
bare lone pair, meaning that no oxidation occurred during the
synthetic procedure thanks to the high oxidative resistance of
arsenic; oxidized product tends to be obtained in the case of
phosphole.[23] The trivalent arsenic atom has a trigonal pyramidal
structure due to the s-character of the lone pair, differing from
trigonal planar pyrrole derivatives. The phenyl group on the
arsenic atom is perpendicular to the arsole ring: C1−As1−C5
and C4−As1−C5 angles are 103.4(1)° and 100.8(1)°,
respectively (Figure 1a). The phenyl groups at the 2,5-positions
have co-planarity with the arsole center, compared with those at
the 3,4-positions. The torsion angles of these phenyl groups to
the arsole ring are 26.6(4)° (As1−C1−C11−C12), 25.0(5)°
(As1−C4−C29−C34), 64.3(4)° (C1−C2−C17−C18), and 67.6(5)°
(C4−C3−C23−C28) (Figure 1b).
Table 1. Optical properties of 5a-c .
and 6 [a]
solution[b]
solid
[c]
[d]
[e]
[d]
[e]
abs
ex
em
ex
em
[f]
[f]
[nm]
359
361
378
374
[nm]
370
384
400
375
[nm]
476
482
498
465
[nm]
394
382
443
381
[nm]
482
488
498
482
5a
5b
5c
6[g]
0.01
0.03
0.04
0.59
0.61
0.35
0.28
0.21
[a] All the measurements were performed under ambient condition. [b]
Measured in 10-4 M in THF. [c] Longest absorption maximum. [d]
Excitation maximum (emission at the

em). [e] Emission maximum
(excitation at the
reference 18a.
ex). [f] Absolute quantum yield. [g] Cited from
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nitrogen atmosphere at 77 K. These results suggest that their
emissions were fluorescence though a heavy-atom, arsenic, is
contained. Time-dependent DFT (TD-DFT) calculation about 5a
revealed that the HOMO-LUMO transition is responsible for the
absorption and emission; the calculated oscillator strength and
transition energies due to the HOMO-LUMO transition were
0.3650 and 381.76 nm, respectively (B3LYP/6-31G+(d,p)). It is
probable that a lack of orbital participation from the arsenic atom
in the HOMO leads to less spin-orbit coupling, effectively making
phosphorescence less likely.[26]
Figure 3. (a) Intramolecular CH- interactions and (b) packing structures of 5a
with depicting an intermolecular CH- interaction. Thermal ellipsoids are
drawn at the 50% probability level. Red spheres are centroids of the five- or
six-membered rings.
Aromaticity of arsoles
Aromaticity is an important aspect in the chemistry of heterole.
It is well known that in the series of heteroles containing
elements in group 15, pyrrole has high aromaticity, but
phosphole and arsole show much lower aromaticity.[12] This is
because lone pairs of phosphorus and arsenic have higher s-
character compared with nitrogen, resulting in the little
contribution to the -conjugation with the butadiene moiety. Here,
the effect of substituents on the aromaticity of arsoles was
evaluated by nucleus-independent chemical shift (NICS)
Figure 2. Frontier orbitals and photographs (excited at 365 nm) of (a) 5a and
(b) 6.
values.[27]
1,2,3,4,5-Pentaphenylarsole
(6), 1-phenylarsole
(5a),
(7),
1,2,5-
1,2,3,4,5-
triphenylarsole
pentaphenylphosphole (8), 1,2,5-triphenylphosphole (9), and 1-
phenylphosphole (10) were compared (Figure 4). The
geometries of these compounds were determined based on full
optimization by DFT calculation at the B3LYP/6-31G+(d,p) level
of theory. The NICS(1)zz values were estimated at GIAO-
B3LYP/6-311G+(d,p).
Most importantly, the emission efficiencies of the arsoles in
solution and in the solid state were completely different. The
quantum yield of 6 in the solid state ( = 0.21) was lowered from
that in solution ( = 0.59), which is a typical phenomenon in
organic luminogens. In contrast, the solid sample of 5a showed
intense emission ( = 0.61), while little emission was observed
in a solution ( = 0.01). Compounds 5b and 5c exhibited the
same tendency. Similar to another AIE-active peraryl heterole,
propeller-like motions of the aryl groups consumed energy of the
excitons in solutions. On the other hand, those motions were
frozen in the solid states. In the packing structure, no -
interaction is observed (Figure 3). Namely, the twisted phenyl
groups at the 1,2,5-positions prevent the 2,5-diphenylarsole
moiety from forming a stacking structure. Additionally, robust
intra- and intermolecular CH- interactions restrict molecular
motions. Because of these facts, 5a efficiently showed emission
in the solid state. It is possible that the methyl (5b) and methoxy
(5c) groups prevent the formation of the CH- interactions,
resulting in the weaker emission intensity in the solid states:  =
0.35 (5b) and 0.28 (5c). In the case of 6, the co-planarity of 2,5-
diphenyl groups with the arsole center was higher than that of
5a; the torsion angles between the arsole and benzene rings
were 9.9(4)° and 13.0(4)°.[18a] As a result, 6 was the least
emissive in the solid state ( = 0.21).
Figure 4. Chemical structures and NICS(1)zz values of 5a and 6-10;
calculations are based on optimized structures.
First, the arsoles have lower aromaticity than the phospholes,
judging from the NICS(1)zz values of 5a and 6-10. Since a lone
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pair of an arsenic atom has higher s-character compared with
that of
a phosphorus atom, an arsole tends to have
approximately 4 electrons. Cyrañski et al showed the same
tendency by utilizing various parameters besides NICS.[11c] Then,
the NICS(1)zz values of 5a, 6, and 7 indicate that substitution of
the heteroles at the 2,5-positions lowers the aromaticity. This
corresponds well with Nguyen’s paper[27] on phosphole, which
reports that expansion of the -conjugation at the 2- and/or 5-
positions lowers the aromaticity because the cyclic conjugation
of the heterole is weakened by the expanded linear conjugation
including the cis-1,3-butadiene. Actually, in the case of 9 and 10,
the same results have been reproduced here. In addition, we
confirmed that the aromaticity of the arsole ring increases when
the 2,5-diphenyl moieties are twisted relative to the arsole ring
from 0° to 90° (Figure S15). Restriction of the -conjugation
between the arsole and benzene rings is effective for increasing
the aromaticity of the arsole. The arsole rings of 5a and 6 have
similar aromaticity, suggesting that the phenyl groups at the 3,4-
positions hardly affected the aromaticity of the arsole ring. This
is because the phenyl groups at the 3,4-positions much less
contributed the -conjugation than those at the 2,5-positions, as
the DFT calculations suggested (vide supra). In the case of the
phospholes, 8 and 9 showed quite similar aromaticity, meaning
that the phenyl groups at the 3,4-positions hardly affect the
aromaticity of phosphole as well.
Figure 5. ORTEP drawings of [AuCl(5a)]. Thermal ellipsoids are drawn at the
50% probability level. (a) Selected angles and (b) dimer via aurophilic
interaction.
The optical properties of [AuCl(5a)] were measured and
summarised in Table 2. In solutions, the absorption and PL
spectra of [AuCl(5a)] were red-shifted from those of 5a. Since
the arsenic atom contributed to mainly the LUMO as shown in
Figure 2a, lowering the electron density due to the coordination
effectively lowered the LUMO level, resulting in narrower
HOMO-LUMO gap (Figure S16) and the red-shifted spectra.
This is in agreement with the result of 1,2,5-triphenylarsole 6,
which was reported in our previous paper.[17a] On the other hand,
in the solid state, the emission maximum of [AuCl(5a)] was blue-
shifted from that of 5a (Figure 6). Emission lifetime
measurement implied that the emission of [AuCl(5a)] ( = 0.62
ns) is fluorescence, and that the 1,2,3,4,5-pentaphenylarsole is
the luminescent center. DFT calculation revealed that [AuCl(5a)]
has larger HOMO-LUMO gap (Eg = 4.12 eV) than 5a (Eg = 3.68
eV) in the crystalline states (Figure S16). Highly distorted
structure of the 2,5-diphenylarsole moiety in the crystalline of
[AuCl(5a)] restricted the expansion of the -conjugation.
Gold(I) complex and luminescent mechanochromism
An arsenic atom of an arsole has efficient coordination ability
unlikely to the pyrrole analogue because its low aromaticity
localizes the lone pair. In the present study, gold(I) chloride
complex of 5a ([AuCl(5a)]) was synthesized via reaction of 5a
with AuCl in CH2Cl2 (Scheme 3). The obtained products were
subjected to recrystallization by slow mixing of a CH2Cl2 solution
and MeOH, and a single crystal was analysed by X-ray
diffraction (Figure 5).[21] The gold(I) chloride complex forms a
dimer through intermolecular aurophilic interaction (Au−Au bond:
3.533(2) Å). Steric repulsion with the adjacent molecule distorts
the aryl groups at the 2,5-positions, resulting in the larger torsion
Table 2. Optical properties of 5a and [AuCl(5a)].[a]
solution[b]
solid
[c]
[d]
[e]
[d]
[e]
abs
ex
em
ex
em
[f]
[f]
[nm]
359
368
[nm]
370
377
[nm]
476
491
[nm]
394
456
[nm]
482
445
5a
0.01
0.03
0.61
0.03
angles:
69.1(7)°
(As1−C1−C11−C12)
and
53.1(8)°
[AuCl(5a)]
(As1−C4−C29−C34).
[a] All the measurements were performed under ambient condition. [b]
Measured in 10-4 M in THF. [c] Longest absorption maximum. [d]
Excitation maximum (emission at the
em). [e] Emission maximum
(excitation at the ex). [f] Absolute quantum yield.

In the course of the experiments, we found that crystals of
[AuCl(5a)] showed luminescent mechanochromism. That is, the
emission color was changed from blue to greenish-blue by
grinding in a mortar (Figure 6). The crystalline and ground
Scheme 3. Synthesis of gold(I) chloride complex [AuCl(5a)].
samples are here denoted as [AuCl(5a)]cry and [AuCl(5a)]grd
,
respectively. PL measurements revealed that [AuCl(5a)]grd
showed red-shifted spectrum (em = 496 nm) from [AuCl(5a)]cry
(em = 445 nm).
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1. Materials
Bis(cyclopentadienyl) zirconium(IV) dichloride (ZrCl2Cp2), n- butyllithium
(n-BuLi, 1.6 M in hexane), gold(I) chloride (AuCl) were purchased from
Sigma-Aldrich (Hattiesburg, Mississippi, US). Copper(I) chloride (CuCl),
iodine (I2), chloroform (CHCl3), dichloromethane (CH2Cl2), methanol
(MeOH), hexane, tetrahydrofuran (THF, super dehydrated grade), and
ethyl acetate (EtOAc) were purchased from Nacalai Tesque (Kyoto,
Japan). Distilled water and magnesium sulfate (MgSO4) were purchased
from Wako Pure Chemical Industry (Osaka, Japan). Diphenyl acetylene
(3a) was purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo,
Japan). Hexaphenylcyclohexaarsine (1),[17a] bis(p-tolyl)acetylene (3b),[31]
and bis(p-anisyl)acetylene (3c)[31] were prepared according to literature
procedures.
2. Instruments
Figure 6. Photographs (excited at 365 nm) and PL spectra of 5a, [AuCl(5a)]cry
and [AuCl(5a)]grd (excited at 394 nm, 456 nm, and 434 nm, respectively).
,
1H- (400 MHz) and 13C- (100 MHz) NMR spectra were recorded on a
Bruker DPX-400. The following abbreviations are used; s: singlet, d:
doublet, t: triplet, m: multiplet, br: broad. High-resolution mass spectra
(HRMS) were obtained on a JEOL JMS-SX102A spectrometer. UV-vis
spectra were recorded on a JASCO spectrophotometer V-670 KNN.
Emission and excitation spectra were obtained on an FP-8500 (JASCO),
and absolute PL quantum yields (Φ) were determined using a JASCO
ILFC-847S; the quantum yield of quinine sulfate reference was 0.52,
which is in agreement with the literature value.[32] Emission lifetimes were
measured using Quantaurus-Tau (Hamamatsu Photonics, Shizuoka,
Japan). All the optical measurements were performed under ambient
condition.
It is well known that Au−Au bond has generally similar
bonding energy to hydrogen bonds.[29] Since external stimuli can
cleave Au−Au bond, supramolecules constructed through
aurophilic networks have been applied to stimuli-responsive
materials.[30] Here, mechanical stimulus should cleave the
Au−Au bond of the dimers which are shown in the
crystallographic data. Powder XRD measurement of
[AuCl(5a)]grd gave broad signals (Figure S17), meaning that the
grinding process caused crystal-to-amorphous transition. In the
amorphous sample [AuCl(5a)]grd, the distortion of the 2,5-
diarylarsole moiety was probably relieved, resulting in expansion
of the -conjugation to cause the red-shift emission. Actually, the
HOMO-LUMO gap of [AuCl(5a)] adopting the structure
optimized by DFT calculation (Eg = 3.65 eV) is narrower than
that of 5a and [AuCl(5a)] in the crystalline structures (Eg = 3.68
eV and 4.12 eV, respectively) (Figure S16).
3. X-ray crystallographic data for single crystalline products
The single crystal was mounted on a nylon loop. Intensity data were
collected at room temperature on a Rigaku XtaLAB mini with graphite
monochromated Mo Kα radiation. Readout was performed in the 0.073
mm pixel mode. The data were collected at room temperature to a
maximum 2θ value of 55.0°. Data were processed by Crystal Clear.[33] An
empirical absorption correction[34] was applied. The data were corrected
for Lorentz and polarization effects. The structure was solved by direct
method[35] and expanded using Fourier techniques. The non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were refined using
the riding model. The final cycle of full-matrix least-squares refinement on
F2 was based on observed reflections and variable parameters. All
Conclusions
2,3,4,5-Tetraaryl-1-phenylarsoles were synthesized by
practical means utilizing zirconacyclopentadiene reagents and
diiodophenylarsine. The obtained dyes 5a-c are the first
examples of AIE active organoarsenic compounds. The arsenic
atom has the stable trivalent state and coordination ability.
Compatibility of these two features is difficult in the cases of
phosphole and pyrrole derivatives. Gold(I) chloride complex with
5a was readily synthesized and the emission color was
effectively changed by the coordination. Moreover, [AuCl(5a)]
showed luminescent mechanochromism thanks to the dimer
formation via intermolecular aurophilic interaction. The present
results have revealed that emission colors of the peraryl arsole
can be tuned by multiple ways, i.e., chemical modification,
coordination, and mechanical stimulus. This novel design for AIE
luminogen based on heterole backbone will open new avenue of
heteroatom chemistry and functional organic materials.
calculations
were
performed
using
the
CrystalStructure[35]
crystallographic software package except for refinement, which was
performed using SHELXL2013.[36] Crystal data and more information on
X-ray data collection are summarized in Tables S1-3.
4. Computational detail
DFT calculations were carried out to investigate the frontier orbitals and
the NICS values. In addition, the HOMO-LUMO transition energies (E)
and their oscillator strengths (f) were estimated by TD-DFT calculations.
The calculations of the frontier orbital energies and the electron transition
energies employed B3LYP/6-31G+(d,p) (for H, C, N, O, F, S, Cl, As) and
LanL2DZ ECP (for Au) set combination using the Gaussian 09 program
package.[37] The NICS values were calculated at GIAO-B3LYP/6-
311G+(d,p).
5. Synthetic procedure and characterization data
Generation of diiodophenylarsine (2).[15] A THF solution (10 mL) of I2
(0.203 g, 0.80 mmol) was directly added to solid 1 (0.122 g, 0.13 mmol)
Experimental Section
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under N2 atmosphere, and the THF solution of diiodophenylarsine (2)
was immediately prepared. Without isolation, the THF solution was used
for the next reactions.
(eluent: hexane/EtOAc = 20/1 to 10/1 to 5/1, v/v). The solvents were
removed in vacuo, and the residue was subjected to recrystallization
(slow mixing of the CH2Cl2 solution of the product with MeOH at ambient
temperature) to obtain 5c as yellow crystals (0.159 g, 0.253 mmol, 32%).
1H-NMR (acetone-d6, 400 MHz): δ 7.62-7.60 (m, 2H), 7.33-7.30 (m, 3H),
6.95-6.88 (m, 8H), 6.68 (d, J = 12.0 Hz, 4H), 6.61 (d, J = 8.0 Hz, 4H),
2.20 (s, 1H) 2.15 (s, 1H) ppm; 13C{1H}-NMR (CDCl3, 100 MHz): δ 158.0,
157.9, 150.0, 149.3, 137.2, 133.1, 131.5, 131.5, 131.0, 130.4, 128.9,
128.8, 113.3, 113.2, 55.0 ppm. HR-FAB-MS (m/z): calculated for
C38H33O4As [M]+; 628.1595, observed; 628.1580.
1,2,3,4,5-Pentaphenylarsole (5a). A THF solution (15 mL) of ZrCl2Cp2
(0.234 g, 0.80 mmol) was cooled to -78 °C under N2 atmosphere. To the
solution was slowly added a hexane solution of n-BuLi (1.6M, 1.0 mL, 1.6
mmol) with a syringe. After stirring for 15 minutes, a THF solution (5 mL)
of 3a (0.285 g, 1.6 mmol) was added slowly with a syringe. After stirring
overnight at ambient temperature, the reaction mixture was cooled to
0 °C, and CuCl (0.160 g, 1.6 mmol) was added (0.159 g, 1.6 mmol). After
stirring for 20 minutes, the separately prepared THF solution (10 mL) of 2
(0.80 mmol) was slowly added with a syringe. After stirring overnight at
ambient temperature, the reaction was quenched by addition of distilled
water, and the organic layers were extracted by CH2Cl2. The combined
organic layers were dried over MgSO4, and after filtration, the volatiles
were removed in vacuo. The crude product was purified by column
chromatography on silica gel (eluent: hexane/EtOAc = 100/0 to 50/1 to
1/1, v/v). The solvents were removed in vacuo, and the residue was
subjected to recrystallization (slow mixing of the CH2Cl2 solution of the
product with MeOH at ambient temperature) to obtain 5a as yellow
crystals (0.162 g, 0.32 mmol, 40%). 1H-NMR (CDCl3, 400 MHz): δ 7.56-
7.53 (m, 2H), 7.27-7.25 (m, 3H), 7.06-6.91 (m, 20H) ppm; 13C{1H}-NMR
(CDCl3, 100 MHz): δ 152.1, 150.0, 138.7, 138.1, 136.4, 133.1, 130.3,
129.2, 129.0, 127.9, 127.7, 126.6, 126.5, 126.4 ppm. HR-FAB-MS (m/z):
calculated for C34H26As [M+H]+; 509.1245, observed; 509.1243.
Gold(I) chloride complex of 5a ([AuCl(5a)]). A CH2Cl2 solution (8.0 mL)
of 5a (99.5 mg, 0.196 mmol) and AuCl (53.6 mg, 0.231 mmol) was stirred
at ambient temperature under N2 atmosphere. Insoluble impurities were
removed by filtration, and the volatiles were removed from the filtrate in
vacuo. The residue was subjected to recrystallization (slow mixing of the
CH2Cl2 solution of the product with MeOH at ambient temperature) to
obtain [AuCl(5a)] as colorless solids (140 mg, 0.189 mmol, 79%). 1H-
NMR (acetone-d6, 400 MHz): δ 7.97-7.95 (m, 2H), 7.61-7.60 (m, 3H),
7.19-7.91 (m, 20H) ppm; 13C{1H}-NMR (CDCl3, 100 MHz): δ 151.9, 140.1,
136.2, 133.8, 132.8, 132.0, 130.1, 129.9, 129.5, 129.1, 129.5, 129.1,
128.5, 128.2, 127.9 ppm. HR-FAB-MS (m/z): calculated for
C34H25ClAsAu [M]+; 740.0526, observed; 740.0529.
Acknowledgements
1-Phenyl-2,3,4,5-tetra(p-tolyl)arsole (5b). A THF solution (15 mL) of
ZrCl2Cp2 (0.233 g, 0.80 mmol) was cooled to -78 °C under N2
atmosphere. To the solution was slowly added a hexane solution of n-
BuLi (1.6M, 1.0 mL, 1.6 mmol) with a syringe. After stirring for 15 minutes,
a THF solution (5 mL) of 3b (0.330 g, 1.6 mmol) was added slowly with a
syringe. After stirring overnight at ambient temperature, the reaction
mixture was cooled to 0 °C, and CuCl (0.160 g, 1.6 mmol) was added
(0.159 g, 1.6 mmol). After stirring for 20 minutes, the separately prepared
THF solution (10 mL) of 2 (0.80 mmol) was slowly added with a syringe.
After stirring overnight at ambient temperature, the reaction was
quenched by addition of distilled water, and the organic layers were
extracted by CH2Cl2. The combined organic layers were dried over
MgSO4, and after filtration, the volatiles were removed in vacuo. The
crude product was purified by column chromatography on silica gel
(eluent: hexane/EtOAc = 100/0 to 50/1 to 20/1 to 5/1, v/v). The solvents
were removed in vacuo, and the residue was subjected to
recrystallization (slow mixing of the CH2Cl2 solution of the product with
MeOH at ambient temperature) to obtain 5b as yellow crystals (0.049 g,
0.087 mmol, 11%). 1H-NMR (acetone-d6, 400 MHz): δ 7.61-7.58 (m, 2H),
7.33-7.30 (m, 3H), 6.94-6.82 (m, 16H) 2.20 (s, 1H) 2.15 (s, 1H) ppm;
13C{1H}-NMR (CDCl3, 100 MHz): δ 151.1, 150.3, 137.0, 136.0, 135.8,
135.4, 133.2, 130.1, 129.1, 128.8, 128.7, 128.6, 128.4, 21.3, 21.1 ppm.
HR-FAB-MS (m/z): calculated for C38H33As [M]+; 564.1798, observed;
564.1812.
We thank Dr. T. Yumura of Kyoto Institute of Technology for
constructive advice on theoretical calculations. We thank Prof. M.
Shimizu, Mr. K. Nishimura, and Mr. M. Sakai of Kyoto Institute of
Technology for emission lifetime measurements.
This study was supported by JSPS KAKENHI Grant Number
JP17H05369 (Coordination Asymmetry).
Keywords: Arsenic • Fluorescence • Gold • Heterocycles • X-ray
diffraction
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Entry for the Table of Contents (Please choose one layout)
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Peraryl arsoles were readily
H. Imoto, A. Urushizaki, I. Kawashima
and K. Naka*
synthesized by utilizing non-volatile
arsenic precursors. The effect of the
surrounding aryl groups on the
electronic structures were elucidated
in experimental and theoretical
Page No. – Page No.
Peraryl Arsoles: Practical Synthesis,
Electronic Structures, and Solid-State
Emission Behaviors
((Insert TOC Graphic here: max.
width: 5.5 cm; max. height: 5.0 cm))
manners. In addition, the arsole
derivative showed interesting solid-
state emission behaviors, i.e.,
aggregation induced emission and
multi-mode color tuning.
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