A versatile dithienylethene-functionalized Ph-diazabutadiene (DAB) ligand: From photoswitchable main-group molecules to photochromic polymers

Article abstract of DOI:10.1002/chem.201301086

Within the past decade photochromic materials, specifically dithienylethenes (DTEs), have received increased interest because of their ability to function as potential photoswitchable molecular devices and optical memory storage systems. Current research in this area has focused on incorporating organic architectures to functionalize the DTE framework and alter the resulting photophysical properties; however, their syntheses are often not trivial. In this context, we have designed a simple and versatile diimine (2) containing adjacent 2,5-dimethyl(thienyl) rings in the backbone. This redox active diimine (2) acts as a precursor to a novel photochromic ligand and has been used to coordinate to both boron and phosphorus elements, along with the synthesis of a phosphorane-side-chain functionalized polymer without further functionalization to the parent DTE framework. A study of the resulting photochromic properties of these compounds revealed that 1) the UV-visible absorption spectra of the closed-ring isomer were dependent of the element present in the N,N′-chelating pocket and 2) incorporating the dithienylethene into a side-functionalized phosphorane polymer greatly increased the closed-/open-ring reversibility and decreased the formation of by-products. Switching it up! A versatile redox-active diazabutadiene (DAB) ligand containing photochromic dithienylethene rings in the backbone has been synthesized. The coordination of both B^III and P^III has been demonstrated, along with the facile functionalization of the P ^III heterocycle with a polymerizable group and the synthesis of a photochromic side-chainfunctionalized polymer (see figure). Copyright

Full text of DOI:10.1002/chem.201301086

FULL PAPER
DOI: 10.1002/chem.201301086
A Versatile Dithienylethene-Functionalized Ph-Diazabutadiene (DAB)
Ligand: From Photoswitchable Main-Group Molecules to Photochromic
Polymers
Jacquelyn T. Price and Paul J. Ragogna*[a]
Abstract: Within the past decade pho-
tochromic materials, specifically
dithienylethenes (DTEs), have re-
diimine (2) containing adjacent 2,5-
dimethyl(thienyl) rings in the back-
tion to the parent DTE framework. A
study of the resulting photochromic
properties of these compounds re-
vealed that 1) the UV-visible absorp-
tion spectra of the closed-ring isomer
were dependent of the element present
in the N,N’-chelating pocket and 2) in-
corporating the dithienylethene into a
side-functionalized phosphorane poly-
mer greatly increased the closed-/open-
ring reversibility and decreased the for-
mation of by-products.
AHCTUNGTRENNUNG
G
bone. This redox active diimine (2) acts
as a precursor to a novel photochromic
ligand and has been used to coordinate
to both boron and phosphorus ele-
ments, along with the synthesis of a
phosphorane-side-chain functionalized
polymer without further functionaliza-
ceived increased interest because of
their ability to function as potential
photoswitchable molecular devices and
optical memory storage systems. Cur-
rent research in this area has focused
on incorporating organic architectures
to functionalize the DTE framework
and alter the resulting photophysical
properties; however, their syntheses
are often not trivial. In this context, we
have designed a simple and versatile
Keywords: boron
ethenes · phosphorus · photochem-
istry · photochromism
·
dithienyl-
AHCTUNGTRENNUNG
Introduction
During the past decade, photochromic materials have re-
ceived considerable attention because of their ability to
function as a potential workhorse within photoswitchable
molecular devices and optical memory-storage systems. Of
these materials, dithienylethenes (DTE) have proven to
have the greatest promise in this field because of their high
fatigue resistance and thermal irreversibility.[1,2] Under irra-
diation with UV light, the open-ring DTE chromophore that
exists in both the antiparallel and parallel states can under-
go a conrotatory cyclization from the antiparallel conforma-
tion generating the closed-ring isomer (Figure 1). Extensive
studies have focused on reversible DTE systems contained
within organic frameworks, however, recent explorations, in
which the DTE fragment incorporates transition-metal com-
plexes, have begun to produce results. These modifications
have shown distinct enhancements in the stability of the
photochromic system and in modulating the photochromic
reactivity.[3]
Figure 1. Photogeneration of the closed-ring isomer from the open-ring
antiparallel conformation.
Although diazabutadiene (DAB) ligands are known for
their ability to be redox active, bind to transition metals,
and support low-valent, low-oxidation-state main-group ele-
ments,[4–6] there has been no report on the modification of
this ligand class with a diarylethene. We envisioned that the
incorporation of a DTE functionality into the diazabuta-
diene framework would open new pathways and opportuni-
ties for the development of photochromic materials because
this ligand set would have the potential to bind to a wide va-
riety of elements from all areas of the periodic table. Ulti-
mately, this could reveal new discoveries for photochromic
reactivity. The incorporation of p-block elements into DTE
systems are particularly well suited for optoelectronic mate-
rials and sensing,[7–12] but these derivatives are limited. Yam
and co-workers have tethered a diketonate onto a thio-
[a] J. T. Price, Prof. P. J. Ragogna
Department of Chemistry, University of Western Ontario
The Centre for Materials and Biomaterials Research (CAMBR)
1151 Richmond St, London, Ontario, N6A 3 K7 (Canada)
E-mail: pragogna@uwo.ca
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201301086.
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phene-substituted DTE, which was used to incorporate BIII[7]
and ultimately generated a gated “lock/unlock” system with
triphenylborane.[8] Another key development in main-group
DTE chemistry was reported by Bielawski and co-workers,
in which they were able to attenuate the activity of their N-
heterocyclic carbene (NHC)–DTE catalyst by using UV
light to promote trans-esterification and amidation reactions.
The catalytic activity of the corresponding organocatalyst
could be remotely tuned by exposure to visible and UV
light.[13,14] These results have been critical in the expansion
of DTE chemistry, however, the synthesis of these com-
pounds (especially, those containing the hexafluorocylopen-
tene ring, Figure 1) requires expensive starting materials,
Scheme 1. Synthesis of BIII-substituted DTE. a) TiCl4, CH2Cl2, 12 h, 76%;
b) 1. Li(s), Et2O, two days, RT; NEt3HCl, 2 h; 2. CH2Cl2, BBr3 or BCl2Ph,
RT, 12 h; 3. EtACTHNUTRGNE(UNG iPr)2N, 2 h (X =Br: 32%, X=Ph: 48%).
À
difficult metal-catalyzed C C coupling chemistry, and time-
consuming purification steps, which can preclude their ap-
plicability in larger-scale and broader applications. In this
context, we have developed a new diazabutadiene frame-
work containing photochromic thiophene rings, which can
be synthesized over a small number of simple, high-yielding
standard transformations. We have demonstrated the poten-
tial versatility of this new ligand system by synthesizing both
boron and phosphorus heterocycles. A key feature in the de-
velopment of our small molecules is that these units can be
further functionalized with a polymerizable group without
the need for any modification to the diarylethene frame-
work and then subsequently converted to the corresponding
polymer. This final polymeric material retains the “switch-
ing” features one expects from DTE systems and as an
added bonus has excellent recyclability with no apparent
degradation when polymerized. Substitution of our ligand
system reveals varied photophysical properties, in which one
could envision a wide expansion by the incorporation of
other p-, d- or f-block elements. These results represent a
completely new and versatile DTE ligand set with the po-
tential for the incorporation of a wide variety of elements
through simple donor–acceptor chemistry.
Figure 2. Solid-state structures of compounds 2, 3, 4, and 7. Thermal ellip-
soids are drawn at the 50% probability level. Hydrogen atoms and sol-
vent molecules are removed for clarity.
Results and Discussion
The DAB (2) was synthesized from a condensation reaction
of 1,2-bis(2,5-dimethyl-3-thienyl)ethanedione (1) with ani-
line and TiCl4 (1:8:1) giving the target product as a yellow
solid in 78% yield (Scheme 1). Single crystals suitable for
XRD studies were obtained from a concentrated solution of
EtOH confirming the formation of 2 (Figure 2).
tion completion, the mixture was quenched with (iPr)2NEt,
filtered, concentrated, and washed with CH3CN giving a
white solid.[15] Subsequent 11B NMR spectroscopy of the
product revealed a single broad resonance at dB =21 and
26 ppm for compounds 3 and 4, respectively. Crystals of
compounds 3 and 4 suitable for XRD studies were obtained
from a concentrated solution of benzene or in CH2Cl2 at
À308C. XRD experiments on these samples confirmed the
expected connectivity (Figure 2).
1
Upon examination of the H NMR spectrum of 2, all thio-
phene signals were shifted upfield significantly (methyl
group: dH =2.72 to 2.49 ppm; 3-position: dH =6.91 to
6.87 ppm). Subsequent reaction of compound 2 with BBr3 or
BPhCl2 gave the air-sensitive boron
(III) compounds 3 and 4,
Ligand versatility was an important feature in the design
and synthesis of this particular dithienylethene, and the
facile installation of different elements into the ligand
framework was a key goal. Thus, from boron, our next
target was the incorporation of phosphorus. This was accom-
plished through a two-electron reduction of the ligand with
PI3, as was developed by Cowley and co-workers, to give the
respectively, as white solids in 32 to 48% yields (Scheme 1).
The complexes 3 and 4 were synthesized by the reduction of
2 with three stoichiometric equivalents of Li(s), in which the
resulting reaction mixture was then quenched with
NEt3·HCl. The product amine was redissolved in CH2Cl2,
and BBr3 or BPhCl2 were subsequently added. After reac-
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Dithienylethene-Functionalized Ph-DAB Ligand
FULL PAPER
2 has shorter C=N bond lengths (1.269(3) and 1.273(3) ꢁ)
À
consistent with double bonds and a longer C C connection
(1.516(4) ꢁ). The phenyl groups are arranged in a cis posi-
tion, with the thiophene rings oriented parallel to each
other (Figure 2). The C2N2B five-membered ring in 3 has
À
two C N single bonds (1.414(3)–1.426(3) ꢁ vs. 1.271 ꢁ
(average) double bonds, 2) and a C(5)=C(6) double bond
(1.371(3) ꢁ compared with 1.518(4) ꢁ in 2). The lengthen-
À
À
ing of the C N and shortening of the C C bonds are evi-
dence of the two-electron reduction of the diimine frame-
work, as was expected from the reduction of 2 with lithium.
The thiophene rings have adopted an antiparallel geometry,
and the planes of the thiophene ring are twisted with respect
to the five-membered borane ring with interplanar angles of
44.1–46.98. This was also observed for compound 4, in which
À
Scheme 2. Synthesis of compounds 5, 6, and 7. a) CH2Cl2, PI3, 12 h, 95%;
b) CH2Cl2, PBr3, 12 h, 92%; c) THF, NEt3, HEA, S8, 65%.
a shortening of the C(5) C(6) bond (1.355(5) ꢁ compared
À
with 1.518(4) ꢁ in 2 and a lengthening of the C N to two
single bonds (1.419(4)–1.415(4) ꢁ vs. 1.271 ꢁ (average)) was
observed. Also similar is the adoption of an anti-parallel ge-
ometry of the thiophene rings, which are twisted with re-
spect to the C2N2B core with inter-planar angles of 55.33
and 56.758 (Figure 2). Compound 7 also exhibits the hall-
marks of two-electron reduction of the ligand with a short-
corresponding phosphenium cation (5; Scheme 2) as an
orange powder in 78% yield.[16] The orange powder was dis-
solved in CDCl3, and upon examination of the 31P{1H} NMR
spectrum, two peaks were observed at dP =191 and 192 ppm
attributed to both the parallel and antiparallel conforma-
tions in solution.[2] Single crystals suitable for XRD studies
were grown from a concentrated CH2Cl2 solution confirming
the structure of 5. Unfortunately, upon exposure to UV
light, there was no observable change in the UV/Vis spec-
À
ening of the C(5) C(6) bond (1.341(4) ꢁ) and lengthening
À
of the C N bond (1.43 average) compared with that of the
free ligand and the thiophene rings with an interplanar
angle of 57.12 and 51.258 with respect to the five-membered
C2N2P ring.
À
trum, and it was suspected that the presence of the I3 anion
To synthesize the polymer 8, reversible addition/fragmen-
tation chain-transfer polymerization (RAFT) conditions
were used to polymerize the acrylate-functionalized mono-
mer (7). The side-chain dithienylethene polymer was pre-
pared by using the side-chain transfer reagent (9) in the
presence of a radical initiator azobisisobutylnitrile (AIBN)
in deoxygenated benzene at 808C (Figure 3). The reaction
quenched the desired ring-closing reaction. Therefore, an al-
ternate route was chosen to avoid this counterion, and
newly established procedure of reacting the diimine of
choice (2) with PBr3 and excess cyclohexene to give the
cyclic diaaminobromophosphine (6) was utilized.[17] Upon
the addition of PBr3, the colorless solution turned orange,
and examination of the crude mixture by 31P{1H} NMR spec-
troscopy showed two new signals at dP =163 and 164 ppm,
again attributed to an equilibrium of parallel and antiparal-
lel conformation present in solution along with a disappear-
ance of the PBr3 resonance (dP =220 ppm). Upon no further
change, the reaction mixture was concentrated and washed
with n-pentane giving the desired product as a white solid,
which was confirmed by XRD studies, and was isolated in
92% yield. The bromophosphine (6) was then dissolved in
THF, and NEt3 and hydroxyethylacrylate (HEA) were
added. 31P{1H} NMR spectrum of the crude reaction mixture
revealed the disappearance of 6 (dP =163 and 164 ppm) and
the appearance of a new single peak (dP =100 ppm). To this
mixture, 1/8 stoichiometric equivalents of S8 were added,
and upon no further reaction as indicated by 31P{1H} NMR
spectroscopy (12 h; dP =68 ppm), a white solid (7) was iso-
lated in 65% yield. Single crystals suitable for XRD studies
were grown from a concentrated solution of hexanes and
confirmed the formation of 7 (Figure 2).
1
was monitored by H NMR spectroscopy, and the formation
of the polymer increased linearly with time, which is charac-
teristic of a controlled polymerization. Examination of the
1H NMR spectrum of the polymer 8 showed the disappear-
Single crystals of compounds 2, 3, 4, and 7 were grown
from various vapor-diffusion combinations and were ana-
lyzed by single-crystal XRD methods (Figure 2). Compound
Figure 3. Polymerization of monomer 7. a) AIBN, C6H6, 808C, 8 h, 42 %.
1H NMR spectra of monomer (bottom) and polymer (top) in CDCl3.
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P. J. Ragogna and J. T. Price
Figure 4. Changes in the UV/Vis absorption spectra (for 4) in n-pentane
(5ꢂ10À5 m) irradiated at l=254 nm as a function of time.
ance of the vinylic protons (d=5.7–6.3 ppm) and a general
broadening of the signals (Figure 3). Molecular weights and
polydispersity indexes (PDIs) were determined by gel-per-
meation chromatography (GPC), which indicated that 8 is a
low-molecular-weight polymer (Mn =4200 gmolÀ1) with a
narrow PDI (1.1). The thermogravimetric analysis (TGA) of
the polymer revealed that it was stable up to 2928C and dif-
ferential scanning calorimetry (DSC) experiments gave a
glass-transition temperature (Tg) of 79.78C.
Figure 5. Changes in the fluorescence spectra (for 4) in n-pentane (5ꢂ
10À5 m) irradiated at l=254 nm as a function of time.
All complexes were found to be soluble in n-pentane with
the exception of the polymer 8, which was soluble in tol-
uene. The electronic spectra of compounds 2–8 showed an
intense absorption band at l=270–300 nm attributed to
both p–p* and n–p* transitions. Upon the photoexcitation
of compounds 4, 7, and 8, each exhibited reversible photo-
chromism, as was revealed by changes in the UV/Vis ab-
sorption spectra (Figures 4 and 5) with a well-defined iso-
sbestic point, whereas compounds 3, 5, and 6 did not. Photo-
excitation of compound 4 with l=254 nm light brings about
the appearance of a lower energy absorption at lmax
498 nm corresponding to the closed-ring isomer with an isos-
bestic point at l=304 nm. Ring opening of compound 4 was
achieved by irradiation with visible light and was marked by
the disappearance of the lower energy absorption at lmax
=
ACHTUNGTRENNUNG
=
498 nm. Excited with l=300 nm light, compound 4 fluores-
ces blue in the open-ring state with lmax =378 nm, and
orange—in the closed-ring state with lmax =558 nm, again
with isosbestic points at 335 and 443 nm (Figure 6).
1
Examination of the H NMR spectra of compound 4 irra-
diated in [D12]cyclohexane at l=250 nm light generated
three new signals (dH =4.49, 2.00, and 1.65 ppm) from the
reversible closed-ring isomer, as well as signals (dH =5.36,
2.43, 2.39, and 1.52 ppm) attributed to possibly six-mem-
bered irreversible rearrangement product (see irreversible
rearrangement (IR) spectra in Figure 7). This was further
confirmed after leaving the sample under ambient light:
only those resonances consistent with the closed-ring isomer
Figure 6. Top: changes in the UV/Vis absorption spectra of 7 in n-pen-
tane (1ꢂ10À5 m) irradiated at l=254 nm and its decomposition after five
cycles. Bottom: changes in the UV/Vis absorption spectra of 8 in toluene
(1ꢂ10À5 m) at l=254 nm light and its decomposition after five cycles.
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Dithienylethene-Functionalized Ph-DAB Ligand
FULL PAPER
very high recyclability with almost no decomposition after
five cycles. These compounds represent the first example
when DTE has been used as a ligand, in which different ele-
ments can be easily incorporated into its framework. Future
work will consist of incorporating both transition and lan-
thanide metals into this manifold.
Acknowledgements
The authors would like to thank the Natural Sciences and Engineering
Research Council of Canada (NSERC), the Canada Foundation for Inno-
vation (CFI), the Ontario Ministry of Research and Innovation, and
Western University for their generous financial support and the Worken-
tin, Hudson, and Stillman research groups for the use of their equipment.
1
Figure 7. Stacked H NMR spectra of compound 4, in which o=open, c=
closed, and IR=irreversible rearrangement product. a) The open-ring
isomer before irradiation; b) after irradiation for 90 min at l=254 nm
light; and c) after being left out in ambient light for 8 h.
[1] Molecular Switches (Ed.: B. L. Feringa), Wiley-VCH, Weinheim,
Germany, 1990.
[2] M. Irie, Chem. Rev. 2000, 100, 1685–1716.
were no longer present, whereas those belonging to the irre-
versible rearrangement product remained (Figure 7).[18,19]
Upon irradiation of the phosphorus(V) monomer 6 and
polymer 7, a new band was observed at lmax =448 nm, signi-
fying the formation of the closed-ring isomer, which is at a
shorter wavelength than the boron derivative 4. This was
also confirmed by the 31P{1H} NMR spectra of an irradiated
sample of compound 6, in which a new phosphorus peak
was observed further downfield from dP =69.0 to 69.5 ppm
in [D12]cyclohexane. Again, these reactions were reversible
and when exposed to longer wavelength visible light, the
open-ring isomer was observed, which can be monitored by
the disappearance of the low-energy band at l=448 nm.
The recyclability of these compounds was measured, and it
was found that the monomer 6 underwent a 65% decompo-
sition after five cycles, however, in the case of the polymer,
very little decomposition was observed and after five cycles
with only 5% decomposition detected (Figure 6).
[3] For examples of DTE-containing transition-metal complexes, see:
a) M. N. Roberts, C.-J. Carling, J. K. Nagle, N. R. Branda, M. O.
Wolf, J. Am. Chem. Soc. 2009, 131, 16644–16645; b) Y. Hasegawa,
T. Nakagawa, T. Kawai, Coord. Chem. Rev. 2010, 254, 2643–2651;
c) Y.-W. Zhong, N. Vila, J. C. Henderson, H. D. Abruna, Inorg.
Chem. 2009, 48, 991–999; d) H.-L. Wong, C.-H. Tao, N. Zhu, V. W.-
W. Yam, Inorg. Chem. 2011, 50, 471–481; e) M. N. Roberts, J. K.
Nagle, M. B. Majewski, J. G. Finden, N. R. Branda, M. O. Wolf,
Inorg. Chem. 2009, 48, 4956–4966; f) S. Fraysse, C. Coudret, J.-P.
Launay, Eur. J. Inorg. Chem. 2000, 1581–1590; g) J. C.-H. Chan,
W. H. Lam, H.-L. Wong, N. Zhu, W.-T. Wong, V. W.-W. Yam, J. Am.
Chem. Soc. 2011, 133, 12690–12705; h) P. H.-M. Lee, C.-C. Ko, N.
Zhu, V. W.-W. Yam, J. Am. Chem. Soc. 2007, 129, 6058–6059.
[4] D. Gudat, Acc. Chem. Res. 2010, 43, 1307–1316.
[5] M. Asay, C. Jones, M. Driess, Chem. Rev. 2011, 111, 354–396.
[6] K. G. Van, K. Vrieze, Adv. Organomet. Chem. 1982, 21, 151–239.
[7] C.-T. Poon, W. H. Lam, H.-L. Wong, V. W.-W. Yam, J. Am. Chem.
Soc. 2010, 132, 13992–13993.
[8] C.-T. Poon, W. H. Lam, V. W.-W. Yam, J. Am. Chem. Soc. 2011, 133,
19622–19625.
[9] H.-L. Wong, W.-T. Wong, V. W.-W. Yam, Org. Lett. 2012, 14, 1862–
1865.
[10] V. W.-W. Yam, J. K.-W. Lee, C.-C. Ko, N. Zhu, J. Am. Chem. Soc.
2009, 131, 912–913.
[11] V. Lemieux, M. D. Spantulescu, K. K. Baldridge, N. R. Branda,
Angew. Chem. 2008, 120, 5112–5115; Angew. Chem. Int. Ed. 2008,
47, 5034–5037.
[12] D. Sud, R. McDonald, N. R. Branda, Inorg. Chem. 2005, 44, 5960–
5962.
[13] B. M. Neilson, V. M. Lynch, C. W. Bielawski, Angew. Chem. 2011,
123, 10506–10510; Angew. Chem. Int. Ed. 2011, 50, 10322–10326.
[14] B. M. Neilson, C. W. Bielawski, J. Am. Chem. Soc. 2012, 134, 12693–
12699.
[15] A similar procedure was used for the synthesis of compounds 3 and
4, see: Y. Segawa, Y. Suzuki, M. Yamashita, K. Nozaki, J. Am.
Chem. Soc. 2008, 130, 16069–16079.
[16] G. Reeske, C. R. Hoberg, N. J. Hill, A. H. Cowley, J. Am. Chem.
Soc. 2006, 128, 2800–2801.
[17] J. W. Dube, G. J. Farrar, E. L. Norton, K. L. S. Szekely, B. F. T.
Cooper, C. L. B. Macdonald, Organometallics 2009, 28, 4377–4384.
[18] H. Taniguchi, A. Shinpo, T. Okazaki, F. Matsui, M. Irie, Nippon
Kagaku Kaishi 1992, 1992, 1138–1140.
[19] M. Irie, T. Lifka, K. Uchida, S. Kobatake, Y. Shindo, Chem.
Commun. 1999, 747–750.
Conclusion
A new class of dithienylethenes (DTE) incorporated into a
diazabutadiene ligand framework were prepared in high
yields without the use of column chromatography or any C
C coupling reactions that often require expensive metal cat-
alysts. A possibility to utilize the DTE as a ligand has ena-
bled easy incorporation of different elements into the C2N2
framework without any modification to the parent ligand.
The final compounds displayed vastly different photophysi-
cal properties depending on the nature of the incorporated
main-group element. When BIII was incorporated, the photo-
À
excitation of the closed-ring isomer was observed at lmax
=
498 nm, whereas the PV monomer and polymer both showed
absorption at lmax =448 nm, a hypsochromic shift of 50 nm.
Also, the BIII DTE fluoresced blue in the open conformation
but orange in the closed state. The facile functionalization
of the DTE with an acrylate group also enabled the forma-
tion of a side-chain functionalized polymer, which had a
Received: March 21, 2013
Published online: && &&, 0000
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P. J. Ragogna and J. T. Price
Switching it up! A versatile redox-
active diazabutadiene (DAB) ligand
containing photochromic dithienyl-
Photochemistry
J. T. Price, P. J. Ragogna* . . &&&& — &&&&
AHCTUNGTRENGNeUN thene rings in the backbone has been
AVersatile Dithienylethene-Function-
alized Ph-Diazabutadiene (DAB)
Ligand: From Photoswitchable Main-
Group Molecules to Photochromic
Polymers
synthesized. The coordination of both
BIII and PIII has been demonstrated,
along with the facile functionalization
of the PIII heterocycle with a polymer-
izable group and the synthesis of a
photochromic side-chain functionaliza-
ble polymer (see figure).
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