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DOI: 10.1039/C5CC07005H
COMMUNICATION
Journal Name
(DMF) at 85°C with a catalyst system consisting of 1,5-
Structures of the two polymers were assessed by 13C NMR
cyclooctadiene (COD), 2,2’-bipyridine and Ni(COD)2 (Yamamoto spectra. As model dimers, 5,5’-bi-1,10-phenanthroline (Phen dimer)
coupling polymerization).11 The obtained poly(Phen) was and 5,5’-bi-2,9-dibutyl-1,10-phenanthroline (DBPhen dimer) were
purified
by
washing
with
toluene,
aq. synthesized. Fig. 1 indicates the 13C NMR spectra of poly(Phen)
ethylenediaminetetraacetic acid (EDTA), water, and benzene in (entry 1 in Table 1), poly(DBPhen) (entry 3 in Table 1), the model
this order. Poly(Phen) was almost insoluble in pure organic dimers, and 1,10-phenanthroline (Phen) and 2,9-dibutyl-1,10-
solvents such as DMF, methanol, and dimethyl sulfoxide phenanthroline (DBPhen) as unit models. The spectrum of
(DMSO), and was soluble in DMF containing a small amount of poly(Phen) was taken in D2O containing 35% DCl and those of the
aq. HCl or trifluoroacetic acid and in aq. HCl (DCl). Quaternary others in CDCl3.
salt formation of the polymer may weaken inter-chain
The 13C NMR spectra of the polymers showed broader spectral
interactions. The DMF-insoluble poly(Phen) was mainly patterns compared with the corresponding models, and signal
broadening was also confirmed in 1H NMR spectra (ESI, Fig. S40).
The broad signals may arise from chain rigidity and also from non-
subjected to analyses hereafter.
Table 1. Synthesis of poly(Phen) and poly(DBPhen) using a Ni catalyst uniformity of magnetic environment in a polymer chain.
in DMF at 85 °Ca.
The signal assignments of Phen,12 Phen dimer, DBPhen, and
DBPhen dimer were conducted using the HMQC, HMBC and
DEPT45 methods starting from the H6(7) signals of Phen and
DBPhen and the H7 signals of the dimers (ESI, Figs. S7-S11, S13-S17,
S25-S31, and S33-S39). These signals were identified as they were
the only singlet ones in the aromatic region of each compound in
the 1H NMR spectra (ESI, Figs. S7, S13, S25, and S33). The 13C NMR
spectra of the four model compounds indicate that formation of a
single bond between monomeric units down-field shifts the signal
of the carbon at which the new bond is formed (C6 and C6’ of the
dimer models). The signals of C6 and C6’ of Phen dimer and
DBPhen dimer appeared at around 135 ppm while the C6(7) signals
of Phen and DBPhen at around 126 ppm and 125 ppm, respectively.
Poly(DBPhen) indicated a spectral pattern similar to that of DBPhen
dimer where the signals at around 135 ppm can be assigned to C6
and C7, supporting its chemical structure. On the other hand, the
a[Monomer] 0.04 M, [Ni] 0.12 M, DMF 12 mL. bWashed with toluene,
aq. EDTA (pH = 5) , aq. EDTA (pH = 9), aq. KOH (2 M), water and
c
benzene in this order. Determined by SEC (Column Shodex Asahapak
GF-310HQ; Flow rate 0.5 mL/min) in DMF containing 30 mM LiCl (vs.
standard poly(2-vinylpyridine)). dSamples for injection were dissolved
in 1 mL of DMF containing 0.01 mL of conc. aq. HCl. eSamples for
injection were dissolved in pure DMF. fThe DMF-soluble materials did
not show any clear signals in H NMR spectra and SEC, suggesting that
they are impurities.
1
In order to improve solubility of polymer, 2,9-di-n-butyl-5,6- spectral comparison between Phen dimer and poly(Phen) was
dibromo-1,10-phenanthroline was synthesized as new difficult due to the different solvents and also possibly due to
2,9-di-n-butyl-1,10- partial quaternary salt formation of poly(Phen) with DCl. 13C
monomer by bromination of
phenanthroline which was obtained through reaction of 1,10- spectra of Phen and Phen dimer were also measured in D2O-DCl;
phenanthroline with n-butyllithium. This compound was the spectrum of Phen dimer indicated rather complicated pattern
polymerized in the same manner as that for 5,6-dibromo-1,10- probably due to partial quaternary salt formation (ESI, Fig. S41).
phenanthroline. The obtained polymer was washed with
toluene, aq. EDTA, water, and benzene in this order.
Poly(DBPhen) was found to be partially soluble in DMF; the
DMF-soluble part was soluble in CHCl3, methanol, DMSO, DMF
containing a small amount of aq. HCl or trifluoroacetic acid and
was insoluble in aq. HCl (DCl). The two n-butyl groups per unit
seem to prevent aggregation of chains. The DMF-soluble
poly(DBPhen) was mainly subjected to analyses hereafter.
Although a [Ni]/[monomer] ratio of 1.5 is often used in
Yamamoto coupling polymerization,11 in the polymerization of
the two monomers, reaction was not effectively induced at
this ratio and proceeded smoothly at a ratio of 3. Coordination
of the 1,10-phenanthroline moiety of the monomers to Ni may
reduce activity of the catalyst system. The monomers were
almost completely consumed under the conditions indicated in
Fig. 1. 100 MHz 13C NMR spectra of Phen (i), Phen dimer (ii) and poly(Phen)
Table 1. For both poly(Phen) and poly(DBPhen) syntheses, a
(entry 1 in Table 1) (iii) (panel A) and those of DBPhen (i), DBPhen dimer (ii)
higher molar mass was attained for a longer reaction time.
and poly(DBPhen) (entry 3 in Table 1) (iii) (panel B). The spectrum in A-iii
was taken in D2O containing 35% DCl with 4,4-dimethyl-4-silapentane-1-
Although the apparent molar masses of poly(Phen)s were
higher than those of poly(DBPhen)s, fair comparison might be
difficult because the two polymers have different chemical
structures.
sulfonic acid sodium salt (DDS) standard and the others in CDCl3 at room
temperature.
2 | J. Name., 2012, 00, 1-3
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