A reversibly transformable chromatic system of the (octaethylporphyrin)-(dihexylbithiophene)-(Lewis base) triads. An evaluation of stereo-electronically controlled effects of dihexylbithiophene and Lewis base on its sensitivity and stability to trifluoroacetic acid

Article abstract of DOI:10.1016/j.tet.2014.12.025

The extended π-electronic conjugation system of the (octaethylporphyrin)-(dihexylbithiophene)-(Lewis base) triads [OEP-DHBTh-LB] exhibits the proton-mediated reversible changes in both ¹H NMR and UV-vis spectra via two-step processes, reflecting the structural features of DHBTh and LB constituents. The spectral changes of OEP-DHBTh-LB with trifluoroacetic acid (TFA) were quantitatively examined by means of ¹H NMR spectral measurement and comparatively analyzed in terms of stereo-electronically controlled effects of DHBTh and LB constituents on its reversibly transformable chromatic system. Successively, based on the minimum amount of TFA necessary for completion of spectral changes at respective steps, the sensitivity and stability of OEP-DHBTh-LB to TFA were evaluated, from the viewpoint of the interactive behavior of the lone pair electrons on N atom in LB with the extended OEP constituent. The present study provides a useful guideline of the molecular design for further sophisticated OEP-based chromatic system with proton-sensing functionality.

Full text of DOI:10.1016/j.tet.2014.12.025

Accepted Manuscript
A reversibly transformable chromatic system of the (octaethylporphyrin)-
(dihexylbithiophene)-(Lewis base) triads.An evaluation of stereo-electronically
controlled effects of dihexylbithiophene and Lewis base on its sensitivity and stability
to trifluoroacetic acid
Hideto Kempe , Junro Yoshino , Naoto Hayashi , Hiroyuki Higuchi
PII:
S0040-4020(14)01715-3
10.1016/j.tet.2014.12.025
TET 26246
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 10 October 2014
Revised Date: 1 December 2014
Accepted Date: 6 December 2014
Please cite this article as: Kempe H, Yoshino J, Hayashi N, Higuchi H, A reversibly transformable
chromatic system of the (octaethylporphyrin)-(dihexylbithiophene)-(Lewis base) triads.An evaluation
of stereo-electronically controlled effects of dihexylbithiophene and Lewis base on its sensitivity and
stability to trifluoroacetic acid, Tetrahedron (2015), doi: 10.1016/j.tet.2014.12.025.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
A reversibly transformable chromatic system of the
(octaethylporphyrin)-(dihexylbithiophene)-(Lewis base) triads.
An evaluation of stereo-electronically controlled effects of
dihexylbithiophene and Lewis base on its
sensitivity and stability to trifluoroacetic acid
Hideto Kempe,a Junro Yoshino,b Naoto Hayashi,b and Hiroyuki Higuchia,b*
aGraduate School of Innovative Life Science, University of Toyama,
bGraduate School of Science and Engineering, University of Toyama,
3190 Gofuku, Toyama, Toyama 930-8555, Japan
*E-mail address: higuchi@sci.u-toyama.ac.jp (H. Higuchi)
Tel/Fax: +81-(0)76-445-6616
Abstract: The extended π-electronic conjugation system of the
(octaethylporphyrin)-(dihexylbithiophene)-(Lewis base) triads
[OEP-DHBTh-LB] exhibits the proton-mediated reversible changes
in both 1H NMR and UV-VIS spectra via two-step processes,
reflecting the structural features of DHBTh and LB constituents.
The spectral changes of OEP-DHBTh-LB with trifluoroacetic
acid (TFA) were quantitatively examined by means of 1H NMR
spectral measurement and comparatively analyzed in terms of stereo-
electronically controlled effects of DHBTh and LB constituents
on its reversibly transformable chromatic system. Successively,
based on the minimum amount of TFA necessary for completion of
spectral changes at respective steps, the sensitivity and stability of
OEP-DHBTh-LB to TFA were evaluated, from the viewpoint of the
interactive behavior of the lone pair electrons on N atom in LB
with the extended OEP constituent. The present study provides a
useful guideline of the molecular design for further sophisticated
OEP-based chromatic system with proton-sensing functionality.
Key words: octaethylporphyrin, dihexylbithiophene, Lewis base, TFA,

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lone pair electrons, chromatic system
Introduction
Over the last half a century, a great deal of effort has been continuously paid for the
construction of porphyrin-based system and the like to develop the new organic
functional materials, for example, a reversibly transformable molecular system between
well-defined structures in an equilibrium state by means of various outside stimuli such
as electronic and photonic operations.1 In relation with functional materials science
aiming at such a reversibly transformable molecular system, we have been also engaged
in the studies of light-, heat-, and proton-mediated molecular behaviors.2 Among them,
designing our original functional porphyrin-based derivatives with proton-mediated
spectral changes, we synthesized the (octaethylporphyrin)-(dihexylbithiophene)-
(pyridin-4-yl) triad 1 [OEP-DHBTh-(4)Py] and preliminarily reported its functional
behavior (Chart 1).3 The three constituents in 1 are simply connected with the rigid but
mobile linkage of 1,3-butadiyne (diacetylene), which is useful not only for
well-definition of these constituents in this system but also for extension of π-electronic
conjugation with various π-electronic system (πES). In the OEP-DHBTh-(4)Py triad, it
was shown that on adding trifluoroacetic acid (TFA) into its chloroform solutions, both
1H NMR and electronic absorption spectra regularly changed via two-step processes,
reflecting the conjugation planarity related with an orientation (head-to-head; HH or
tail-to-tail; TT) of two 3-hexylthiophene rings in DHBTh.4,5 In both spectral
measurements, the first-step process corresponds to the change due to the simple
protonation of TFA on N atom of Py and the second-step process to the change due to
the direct affection of TFA toward OEP ring, respectively (see section 3). It was also
revealed that the original spectra of 1 are recovered by quenching TFA with ordinary
bases like triethylamine (Et3N). As compared with the Py derivative 1, the
corresponding N,N-dimetylaminobenzene derivative 26 [OEP-DHBTh-(4)DMAB] was
also examined to ascertain the generality of those phenomena, proving that both 1 and 2
are the OEP-based chromatic system with the proton-mediated transformable function
via two-step processes (Chart 1).

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As expected, the sensitivity of 1 and 2 to TFA in their spectral changes at each step
was apparently different between them, depending on the nature of lone pair electrons
on N atom in Py and DMAB as well as an orientation of DHBTh (Chart 2). Even
though the N-protonated species of Py and DMAB, i.e., these conjugated acids
themselves possess almost the same pKa value as each other (5.14 for Py-H+ and 5.06
for DMAB-H+),7 ca. 10 times amount of TFA (pKa 0.23)7 was necessary for completion
1
of the first-step process in the H NMR spectral measurement for 2, as compared with
the necessary amount of TFA for 1. As deduced from both residential orbital for the lone
pair electrons and their conjugationally movable area (described as a delta minus in
Chart 2), this result clearly indicates that the basicity (proton-accepting ability) of N
atom as a Lewis base (LB) in this system substantially differs between them. The lone
pair electrons of Py in 1 locate on N atom stubbornly, while those of DMAB in 2 take
part in π-electronic conjugation with the external πES to considerable extent to spread
over the molecule before TFA protonates onto them.
On one hand, the higher the proton-sensing ability is attained, the lower the
reversible stability is accompanied, since the cationic species formed by N-protonation
are generally fragile under the highly acidic conditions. In fact, a large excessive
amount of TFA is known to proceed to an extrusion reaction of Ni2+ ion from the OEP
ring, though gradually and slightly at room temperature,8 lowering the quality of
reversible stability as a material function in consequence (vide supra). Accordingly, it is
very important to derive a guideline of molecular design for further enhancement of the
reversible stability together with the proton-sensing ability.

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In our continuous investigations of the OEP-based chromatic system, in order to
search for the structural requirements for such molecular design through the
structure-property relationships, the derivatives 3 and 4 with HH- and TT-orientational
DHBTh constituents have been synthesized, in which the amino group as a
proton-accepting site of DMAB is attached at 3- and/or 5-positions to the external
conjugation system (Chart 3). In both cases of 3 [OEP-DHBTh-(3)DMAB] and 4
[OEP-DHBTh-(3,5)DMAB], the lone pair electrons do not take part in π-electronic
conjugation with the external πES, in contrast with those in 2, just delocalizing
definitely within the benzene ring (Chart 2, C). Yet, the positive charge introduced by

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the protonation onto N atom of DMAB would also distribute at the definitive sites
(described as a delta plus in Chart 2) on the benzene ring in 3 and 4, conjugationally
apart from the external OEP constituent, through the orbital-orbital interaction
mechanism.9 In other words, the lone pair electrons on N atom of LB in 3 and 4 do not
participate in π-electronic conjugation with the external πES, but possess the stabilizing
ability not only for themselves but also for the cationic species in a different way from
the spread manner over the molecule.
In this paper, the characteristic behaviors of 3 and 4 between before and after the
N-protonation processes at each step were quantitatively examined mainly by means of
1H NMR spectral measurements and were comparatively analyzed by the
stereo-electronically controlled effects of DHBTh and LB on their spectral changes.
Then, their relative sensitivity and reversible stability to TFA were evaluated, on the
basis of the minimum amount of TFA necessary for completion of respective spectral
changes, as compared with those of related compounds 1 and 2. Furthermore, in the
course of this study, a peculiar phenomenon was eventually observed in 4, rightly after
the completion of its first N-protonation process, distinct from 3. From the
structure-property relationships of 1-4, a guideline of the molecular design for more
sensing and stable chromatic OEP-DHBTh-LB system to TFA will be proposed.
Results and Discussions
1. Synthesis of OEP-DHBTh-DMAB 3 and 4.
According to our conventional way,4 the title compounds 3 and 4 were synthesized,

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by oxidative cross coupling reaction of the isomeric OEP-DHBTh acetylene 54 or 64
with corresponding DMAB acetylene 710 or 811 under the modified Eglinton conditions
(Scheme 1, also see Experimental part).12 The reactions of 7 with 5 and 6 were carried
out in a mixture of Py and methanol (MeOH) (5:1 in v/v) in the presence of excessive
copper(II) acetate [Cu(OAc)2]. Ordinarily, the reaction mixtures were chromotographed
on silica-gel (SiO2) column to afford the orientational isomers 3HH and 3TT in 35% and
23% yields, respectively, together with the corresponding homo-coupling dimers 913
and 1010. The reactions of 8 with 5 and 6 under the similar conditions gave the
corresponding isomers 4HH and 4TT in 28% and 32% yields, respectively, together with
913 and 11. All the highly extended OEP derivatives 3 and 4 formed dark purple
microcrystallines from CHCl3-methanol and proved to be stable under the room light at
an ambient temperature.
1
2. H NMR Spectra of OEP-DHBTh-DMAB 3 and 4.
The spectra of 4HH as well as the corresponding reactants of terminal acetylenes 5
and 8, for example, are shown in Fig. 1. Reflecting its skeletal feature, the spectrum of
4HH is fairly simple, similar to that of the corresponding TT-isomer. It proved that all the
proton signals belonging to OEP and DMAB of 4 appeared at nearly the same chemical
shifts as each other, regardless of an orientation of DHBTh, affording OEP
meso-protons (meso-H) at around 9.40 ppm (3H), DMAB aromatic-protons (Ar-H) at

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around 6.35 (2H) and 6.10 ppm (1H), and DMAB methyl-protons (Me-H) at around
2.95 (12H) ppm, respectively. On the other hand, the protons due to the DHBTh
constituent subtly show a crucial difference in their spectral behavior between these
orientational isomers. 4HH affords thiophene-protons (Th-H) at 7.28 (1H) and 7.19 (1H)
ppm as a pair of singlet signals and thienylmethylene-protons (Th-CH2) at around 2.50
(4H) ppm as a batch of signals, while 4TT affords Th-H at 6.97 (1H) and 6.94 (1H) ppm
at the little higher field as a pair of singlet signals and Th-CH2 more clearly at 2.75 (2H)
and 2.65 (2H) ppm as a pair of triplet signals. These results apparently indicate that the
diamagnetic ring current effect of the diacetylene linkage influences those protons
closer to the triple bond to a much greater extent, such as Th-H of 4HH and Th-CH2 of
4TT, moving them to the lower field from the corresponding protons in the opposite
isomer. Such a diamagnetic ring current effect of the diacetylenic OEP constituent also
slightly but firmly perturbed the particular protons of 3, almost similar to those of 4,
except for an inherently different feature of Ar-H signals in DMAB (δ ca. 7.2 ppm (1H),
ca. 6.9 ppm (2H), and ca. 6.6 ppm (1H) for both HH- and TT-isomers of 3). Yet, it might
be worthy to mention that Ar-H of 4 appeared in the higher field region by ca. 0.5 ppm
than the corresponding ones of 3, clearly indicating that the amino group efficiently
increases the electron density on its ortho- and para-carbons by sending its lone pair
electrons to participate into a resonant conjugation of the benzene ring, as deduced in
Chart 2.
The facts obtained above evidently show that the molecular structures of 3 and 4
hold respective skeletal features of all the reactants 5, 6 7, and 8, respectively. Thus, it
concludes that since all the constituents in these derivatives 3 and 4 are connected with
the rigid and straight linkage of diacetylene, the molecular skeletons are firmly defined
for analytical study and are well adjusted to systematic modification of the electronic
properties, which is of importance for evaluation of their functional efficiency as well.
In addition, as a preliminary experimental result of 4, it should be noted that the Ar-H
signal Hb positioned between two neighboring amino groups appear at the higher field
than the Ar-H signal Ha under the neutral conditions, while those Ha and Hb signals
completely exchange their positions under the acidic conditions (vide infra).

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Fig. 1. 1H NMR spectra of (A) for 8, (B) for 5, and (C) for 4HH (300 MHz, in CDCl3, 25
C).
3. Reversible Spectral Changes of 1-4 under the Neutral and Acidic Conditions.
In the electronic absorption spectral measurements, on adding TFA into their CHCl3
solutions (adjusted to the sample concentration of ca. 2.5 x 10-5 mol/103 cm3 in CHCl3,
also see Experimental part), the spectra of 3 and 4 gradually and evidently change in a
visible region due to the OEP nucleus from the point at around 103 eq. TFA via two-step
processes in common. The spectral changes are also accompanied by a striking change
in color appearance of the solution from dark green to pale yellow, similar to those of 1
and 2.3,6 For example, the changes of 4HH at the first-step process are just related with a
gradual decrease of the intensity of Soret-Band (Fig. 2). However, the changes at the
second-step process are quite complicated, mostly exhibiting a drastic reformation of
Soret-Band in both intensity and absorption curve, with reflecting an orientation of
DHBTh, and simultaneously giving rise to a gradual displacement of Q-Band with the
new band in the much longer wavelength region. These spectral changes of 1-4 are

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almost reversible, to recover the original spectra by neutralization of the
TFA-containing solution with NEt3 at any stages.
Fig. 2. Electronic absorption spectral changes with adding TFA to the CHCl3 solution of
4HH at 25 C. The first-step: (dark blue) 1.0 x 103 eq., (purple) 1.0 x 104 eq., and (brown)
2.0 x 104 eq. to 4HH. The second-step: (green) 6.0 x 104 eq., (light blue) 8.0 x 104 eq.,
and (orange) 1.0 x 105 eq. TFA to 4HH.
1
Similar to such a peculiar behavior in their electronic spectral changes, H NMR
spectra of all the derivatives 1-4 (adjusted to the sample concentration of ca. 8.5 x 10-3
mol/103 cm3 in CDCl3, also see Experimental part) also characteristically exhibit the
proton/amine-mediated reversible changes via two-step processes, as seen in typical
examples of 3HH (Fig. 3) and 4HH (Fig. 4). At the first-step process, all the proton
signals belonging to LB just shifted to the lower field region in accordance with the
added amount of TFA, with other protons belonging to both OEP and DHBTh
constituents almost remained as they are. This result clearly indicates that TFA interacts
first with the N atom of LB for protonation to introduce the positive charge into the LB
ring, undoubtedly referring to the first-step process observed in their electronic

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absorption spectra where the Soret-Band gradually weakens its intensity.
Successively after completing the N-protonation onto LB, some further excessive
amount of TFA simply started to broaden the particular signals of meso-H and
OEP-CH2 without changing their chemical shifts, and then faded them out into the base
line finally. An embarrassing behavior observed in these proton signals on the OEP
1
periphery is exactly the common phenomenon at the second-step process in their H
NMR spectral changes, which should correspond to the drastic reformation process in
the electronic structure of OEP nucleus in their electronic spectral changes. In any
respects, the phenomenon at the second-step process indicates that an excess of TFA
directly interacts with the OEP ring somehow.3
As shown in Fig. 3, the derivative 3HH exhibited a typical behavior of 1H NMR
spectral changes, in which on adding TFA all the Ar-H signals (δ 7.20-6.74 ppm)
gradually and regularly moved to the lower field, gathered together within a narrow area
of 7.7-7.5 ppm, and found their respective stationary positions after completion of the
protonation onto N atom of DMAB of 3HH. Then, at the second-step process, the
particular protons belonging to OEP started to broaden and finally faded out into the
base line. Similarly, on adding TFA to a CDCl3 solution of 4HH (Fig. 4), at the first-step
process, the Ar-H signals due to Ha (δ 6.35 ppm) and Hb (δ 6.09 ppm) both gradually
shifted to the lower field with exchanging their respective positions and then stopped
moving at the stationary positions of δ 7.00 and 6.80 ppm, which was a consequence
just after addition of 2 eq. TFA to 4HH (Fig. 4c). The complete reverse of Ha and Hb in
chemical shift under the neutral and acidic conditions suggests that an inductive effect
of the ammonium moiety on these protons is intensive enough to exceed a diamagnetic
ring current effect of the triple bond, in addition to a particular feature of the Hb-linking
carbon which is the synchronously neighboring position between two amino groups
(Chart 2 and Chart 5, A). Anyhow, the above result of 4HH should indicate that
mono(N-protonation) or bis(N-protonation) process onto DMAB was completed, as is
similarly the case for the other derivatives 1-3. However, at around 20 eq. TFA, both
Ar-H signals of Ha and Hb again started moving toward the further low field region and
then stopped moving at around 50 eq. TFA to reach their final stationary positions (δ
7.02 and 6.96 ppm). Moreover, at the same time, in a range between 30 eq. and 60 eq.
TFA, the meso-H signals also changed to broaden and completely disappeared into the
base line. A series of spectral changes observed in 4HH would lead to a rational

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interpretation that the mono(N-protonation) process onto DMAB completes at 2 eq.TFA
Fig. 3. 1H NMR spectral changes in a range of 6-10 ppm with adding TFA to the CDCl3
solution of 3HH (300 MHz at 25 C). The first-step: (a) 0 eq., (b) 1.0 eq., (c) 2.0 eq., (d)
3.0 eq., (e) 4.0 eq., and (f) 5.0 eq. TFA to 3HH. The second-step: (g) 10 eq., (h) 15 eq., (i)
20 eq., (j) 25 eq., (k) 30 eq., and (l) 35 eq. TFA to 3HH.

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Fig. 4. 1H NMR spectral changes in a range of 6-10 ppm with adding TFA to the CDCl3
solution of 4HH (300 MHz at 25 C). The first-step: (a) 0 eq., (b) 1.0 eq., (c) 2.0 eq., (d)
3.0 eq., (e) 4.0 eq., (f) 5.0 eq., (g) 10 eq., and (h) 20 eq. TFA to 4HH. The second-step: (i)
30 eq., (j) 40 eq., (k) 50 eq., and (l) 60 eq. TFA to 4HH.
and the bis(N-protonation) process starts at 20 eq. TFA and finishes at 50 eq. TFA, to
reach the final equilibrium state. It is also undoubtedly indicated that the broadening
and fading process of the meso-H signals of 4HH starts at least after completion of the
mono(N-protonation) process onto LB, similar to that of the other derivatives 1-3. In all
cases, though the OEP-DHBTh-LB system is very stable even in such a highly acidic
solution, it might be wise to avoid adding TFA further unnecessarily after the point

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where the meso-H signals completely disappear into the base line, in order to prevent
the N-protonated species from some acid-base over-reactions (vide supra).
Although all the derivatives 1-4 exhibited the same behavior as mentioned above in
common in their reversible spectral changes, regardless of orientation of DHBTh, the
derivative 4 showed a peculiar behavior additionally at an intermediate stage between
after completion of the mono(N-protonation) process and before start of the
bis(N-protonation) process onto DMAB. Thus, on further adding TFA into the solution
of the mono(N-protonated) species of 4, the Ha signal almost retained its stationary
position, while the Hb signal slightly but evidently exhibited a gradual high-field shift
unexpectedly up to 20 eq. TFA (Fig. 4d-h). Fortunately, the spinning side band (ssb)
signals of CHCl3 are helpful to grasp the moving behavior of these protons in this
region. Regarding this peculiar phenomenon, it is quite unlikely to presume that further
addition of TFA increases the electron density on the Hb-linking carbon through
π-electronic conjugation with the external πES, because the meta-position to the amino
substituent in 4 can not be a more electron-deficient cationic site (Chart 2). Even if it
were possible somehow, the other Ha signal would also show the high-field shift similar
to Hb. Alternatively, as a plausible interpretation for this curious phenomenon in 4, an
additional equilibrium between monomeric form 4-H+(M) and dimeric form 4-H+(D) is
tentatively proposed for stabilization of the mono(N-protonated) species (Scheme 2). In
such a cyclic form 4-H+(D) (Chart 5B), the ring proton of Hb would be affected more
intensively by a diamagnetic ring current effect of the opposite benzene ring. Thus, it
would move to the higher field more or less than that in a monomeric form 4-H+(M), on
adding TFA until reaching their equilibrium state. Nevertheless, since the dimeric form
4-H+(D) formed by the hydrogen bonds is too fragile to hold its metacyclophane-like
frameworks, the contribution of 4-H+(D) to this equilibrium should substantially be
small. In practice, the spectral changes by further adding TFA indicated that 4-H+(D)
readily collapses by an intramolecularly repulsive interaction between doubly-positive
charges introduced by the second-step protonation onto DMAB, again generating the
monomeric form 4-2H+ gradually and completely.

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C
S
6H13
NR2
Hb
Ha
Ha
N
N
N
N
S
Ni
- H+
NR2
R=CH3
C6H13
+ H+
4
C6H13
NR2
H
N
N
N
N
S
C6H13
C6H13
S
NR2
NR2
NR2
N
H
Ni
+ H+
N
N
N
N
S
S
N
N
N
N
S
Ni
NR2
Ni
C6H13
S
H
R2
C6H13
6H13
4-H+ (D)
- H+
R
S
NR2
NR2
- H+
N
N
N
N
S
+ H+
+ H+
Ni
H
C6H13
- H+
4-H+ (M)
C
S
6H13
R2
N
N
H
H
N
N
S
Ni
N
N
R
R2
4-2H+
Scheme 2
4. Sensitivity and Stability of 1-4 to TFA in Reversible Spectral Changes.
As mentioned briefly in section 3, the addition of TFA into CHCl3 solution of
OEP-DHBTh-LB induced to change its electronic absorption spectra in both Soret- and
Q-Bands with regard to their intensity and absorption curve, and successively afforded
the new bands at the longer wavelength region (Fig. 2). Among them, the selected band
maxima characteristic of the OEP nucleus under the neutral and fully acidic conditions
were summarized in Table 1, clearly showing that both DHBTh and LB constituents
characteristically influence their maxima.
In the absence of TFA, the spectra of all the derivatives 1-4 simply exhibited almost
the same behavior as each other, affording a broad Soret-Band at around 450 nm (62.2
kcal mol-1) for their HH derivatives and a separated Soret-Band at around 450 and 475
nm (59.0 kcal mol-1) for their TT derivatives.3,6 Similarly, the Q-Band maxima of all

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Table 1. Selected absorption maxima of OEP-DHBTh-LB (λmax/nm, in CHCl3)
Without TFA
With TFA
New Band
690
Soret-Band
449
Q-Band
589
OEP-DHBTh-LB
1
DHBTh
HH
TT
445, 476
448
594
725
HH
TT
590
700
2
3
4
449, 478
449
596
730
HH
TT
590
690
451, 474
449
596
712
HH
TT
593
692
451, 476
595
709
All experiments were carried out at 25 C using the sample solutions adjusted to the concentration of
ca. 2.5 x 10-5 mol/103 cm3.
the HH derivatives appeared at around 590 nm (47.5 kcal mol-1), while those of the TT
derivatives appeared in the longer wavelength region only by 2-6 nm (0.15-0.50 kcal
mol-1) from the corresponding HH isomers, in consequence of the higher conjugation
planarity of TT-DHBTh constituent.4,5 In the presence of TFA, the difference in their
absorption maxima is somewhat more explicit, reflecting the structural features of both
DHBTh and LB. In particular, the new bands of the three HH derivatives in 1, 3 and 4
appeared at nearly the same maxima of 690 nm (40.6 kcal mol-1) as each other, while
the new band of the HH derivative 2 appeared at 700 nm (40.0 kcal mol-1). In spite of
such a suggestive behavior of the HH derivative 2, all the TT derivatives 1-4 exhibited
much longer wavelength shift and changed their new bands in an irregular trend to all
appearance, affording the maxima at 725 nm (38.6 kcal mol-1) for 1, 730 nm (38.4 kcal
mol-1) for 2, 712 nm (39.3 kcal mol-1) for 3, and 709 nm (39.5 kcal mol-1) for 4,
respectively. As a result, the derivative 1 showed the largest energy difference (2.0 kcal
mol-1) between HH and TT orientational isomers in their new band maxima, while the
derivative 4 showed the smallest energy difference (1.1 kcal mol-1) between HH and TT
isomers.
The spectral behavior of 1-4 under the acidic conditions should be attributed to the
practical efficiency of the lone pair electrons on N atom of LB in π-electronic
conjugation over the molecule, as well as to the efficient degree of π-electronic

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conjugation planarity of the DHBTh constituent. In case of the derivatives 1 and 2, the
electron-deficient cationic sites of the N-protonated Py9 and DMAB14 rings are
distributed also on the carbon directly connected with the external OEP constituent and
thus potentially spread over the molecule (Chart 2, A and B), in which the conjugation
planarity of DHBTh reflects severely on their stabilization efficiency. This results in a
large difference of the HOMO-LUMO gap of the N-protonated species between
orientational isomers. To the contrary, though the N-protonated species of 3 and 4 can
be similarly stabilized by a conjugation effect in a limited area of the benzene ring,
these species are in principle forbidden to bring their electron-deficient cationic sites
into the external OEP constituent. Thus, the electron-deficient cationic sites are not
extended across the DHBTh over the molecule, resulting in a little difference of the
HOMO-LUMO gap between HH- and TT-DHBTh isomers (Chart 2). In consequence, it
is proved that the derivative 1 possesses the highest sensitivity to an orientation effect of
DHBTh on this system under the acidic conditions, while the derivative 4 possesses the
lowest sensitivity to the DHBTh orientation. Furthermore, as compared with the
differences of the new bands between 2 and 1 or 3 or 4, regardless of orientation of
DHBTh, it is evidently proved that when the lone pair electrons on N atom of LB play a
cooperative role in π-electronic interaction with the extended OEP constituent both
inductively and conjugationally, the new bands in this system appear in the longer
wavelength region than otherwise more or less (Chart 2 and Table 1).
Table 2 shows the minimum amount of TFA necessary for completion of the
respective spectral changes at each step process in the OEP-DHBTh-LB system, which
1
was examined by H NMR spectral measurements. Similar to the absorption spectral
experiment, the amount of TFA in the 1H NMR spectral experiment proved to be a very
little difference between HH- and TT-DHBTh isomers, where the TT isomers needed
just a bit larger amount than the corresponding HH isomers. Especially in the case of 4,
no practical difference in the amount of TFA was found between these DHBTh isomers.
Such a small difference in the amount of TFA between them is probably due to the
highly proton-donating ability of TFA (pKa 0.23) to LB in the present extended OEP
system (pKa 5.14 for Py-H+, pKa 5.06 for DMAB-H+, and pKa(1) 2.65 for (1,3)DMAB-
2H+, pKa(2) 4.88 for (1,3)DMAB-H+).7,15 Besides, practically in order to attain the
concentration of the species, at the fairly high concentrated samples of 1-4 essential for
1H NMR spectral measurement, very small amount of TFA are enough to reach the

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equilibrium state, while at the fairly low concentrated samples of 1-4 essential for
absorption spectral measurement, quite large amount of TFA are necessary. Taking these
facts into consideration, an adoption of the amount of TFA as a measure in accurate
evaluation of the orientation effect of DHBTh on the extended OEP system is to face a
technical difficulty.
Anyhow, as shown in Table 2, one is the minimum value for the first-step process
corresponding to the completion of mono(N-protonation) onto LB of TT isomers of 1-4,
the other is the minimum value for the second-step process corresponding to the
completion of their meso-H signal disappearance into the base line. The former can be
regarded as a measure of sensitivity of this system to the acidic media, the latter as a
measure of its stability in the fully acidic media, both of which are critical factors for
the development of a chromatic system with the reversibly transformable functions.1
Table 2. Minimum amount of TFA necessary for completion of the respective step processes in the
TT-DHBTh derivatives of OEP-DHBTh-LB examined by means of 1H NMR spectral experiments
Added TFA (eq.)
Role of lone pair electrons
on N atom of LB
OEP-DHBTh-LB
Step 1
1.1
Step 2
2.5
mono-positive charge effect
localization in pyridine N-atom
mono-positive charge effect
resonance effect with the external πES
mono-positive charge effect
delocalization in the benzene ring
di-positive charges effect
1
2
3
4
10
5.0
1.5
25
35
60
delocalization in the benzene ring
All experiments were carried out at 25 C using the sample solutions adjusted to the concentration of
ca. 8.5 x 10-3 mol/103 cm3. The step 1 is for completion of the mono-protonation onto LB. The step 2
is for completion of the disappearance of meso-H signals.
In relation to versatile features of the lone pair electrons on N atom in LB (vide
supra), several useful findings for the functional materials can be led from these results.
Among 1-4, the derivative 1 proved to be the most sensitive to TFA, in which the lone
pair electrons taken in an sp2 hybridized orbital do not make conjugation with any other
p electrons of Py, localize rightly on N atom of LB, and thus fully play a role for

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accepting a proton from TFA to bring a positive formal charge on the N atom of Py ring
(Chart 2, A).14 As compared with 1 carrying such stubborn lone pair electrons on N
atom of LB, the derivative 3 in which the lone pair electrons taken in an sp3 hybridized
orbital are unable to make conjugation with the external πES but are able to delocalize
even definitely within the benzene ring fairly lowers the sensitivity to TFA into nearly
one-fifth efficiency. Similarly, as expected, the derivative 2 in which the lone pair
electrons spread over the molecule through the conjugation system further lowers its
sensitivity into an almost one-tenth efficiency based on 1 (Chart 2, B and C). These
results apparently conclude that in order to enhance its sensitivity to TFA the lone pair
electrons on N atom of LB in this system should not participate in any π-electronic
conjugation as much as possible, which is exactly in a guideline for molecular design,
compatible with a general principle of acid-base interaction.7 In this respect, it is notable
that the derivative 4 showed its sensitivity to TFA almost the same as 1. Such a high
sensitivity of 4 to TFA indicates that an additional amino group to 3 can compensate
sufficiently for the disadvantage in proton-accepting ability of 3 reduced by
delocalization within the benzene ring, by donating the lone pair electrons from the
additional N atom to the benzene ring in an opposite way (Chart 4).
On the other hand, the range in reversible stability of the spectral changes proved to
depend on LB much distinctly, reflecting the role of its lone pair electrons on N atom.
Besides LB, taking the fact into consideration that there are several reactive π-base sites
to TFA such as OEP ring, diacetylene linkage, and sulfur atom of 3HTh in the present
OEP-DHBTh-LB system, the spectral reversibility of this system should be limited for
an absolute guarantee up to the point where the meso-H signals completely disappear
just into the base line under the fully but certain acidic conditions (see section 3).8
Therefore, the values at the second-step process in Table 2 represent the minimum
amount necessary for each OEP-DHBTh-LB derivative reaching such a definite point
under the applied conditions. Especially, the spectral changes at the second-step process

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undoubtedly correspond to the direct interaction between TFA and OEP ring, after the
completion of protonation onto N atom of LB, though mechanistically in a vague.3,6
Thus, the necessary amount of TFA would also be regarded as the strength of
proton-accepting ability of OEP ring as a Lewis base in the N-protonated species of LB
of this system. The smaller value corresponds to the higher proton-accepting ability of
OEP ring, resulting in the less reversible stability of the system, and vice versa. In other
words, the effect of cationic LB at one terminal position on the electron-donating ability
of OEP ring at another terminal position in this system is to be evaluated by the amount
of TFA necessary for completion of the second-step process.
Since the broadening of meso-H signals starts at least after completion of the
mono-protonation on N atom in LB (section 3), it might be natural that the derivative 1
with the most sensitive to TFA shows the least stability to TFA in reverse. In case of the
mono-protonated species from 2, its stability increased into 10 times efficiency based on
1, due to the effective delocalization of electron-deficient cationic sites up to the OEP
ring through the conjugation effect (Chart 2, B). Similarly, the derivative 3 showed the
higher stability to TFA than 2, in spite of the 2 times higher sensitivity based on 2 (Chart
2, C). This result suggests that for stabilizing the N-protonated species of LB the
delocalization of the electron-deficient cationic sites in a π-electronic cyclic system of
the benzene ring is more efficient than in an extended π-electronic conjugation over the
molecule (Chart 6). The trend of this type in stabilizing the N-protonated species was
observed much further efficiently in the derivative 4, resulting in more than 2 times
higher stability based on 2 and ca. 25 times higher stability based on 1, respectively.
Under such acidic conditions, the Lewis base strength of OEP ring in this system is
to be weakened resonantly by a cationic conjugation system over the molecule, but
much further efficiently by a cationic benzenoid system like an electron-withdrawing
substituent to the extended OEP constituent (Chart 6). Especially in the case of 4, it is
again stressed that an additional amino substituent to 3 at the meta-position stabilizes
the electron-deficient cationic sites specifically. And yet, since the broadening process
of meso-H signal and the bis(N-protonation) step onto DMAB start almost
simultaneously in the present mono(N-protonated) species, the DMAB carrying two
ammonium moieties plays a much effective role for reduction of the Lewis base
strength of OEP ring as a further intensified electron-withdrawing substituent (Charts 2
and 4). In addition, an inherent equilibrium between 4-H+(M) and 4-H+(D) should be

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taken into consideration as one of the promising mechanisms for its stabilization
(Scheme 2). As a whole, at present, it could be concluded that the stability in reversible
spectral changes of the present OEP system is controlled critically not only by the
stabilization efficiency for the N-protonated species of LB in the applied media, but also
by the multiple N-protonation sites definitely playable in a benzenoid area.
Conclusion
It was proved that in the OEP-DHBTh-LB system the DMAB derivative 4 possesses
not only nearly the highest sensitivity but also the highest stability to TFA, with regard
to the reversibly transformable spectral changes of the OEP ring. For further
enhancement of its sensitivity and stability as a functional OEP derivative, the results
obtained from this study provide it as a guideline for molecular design that (i) the higher
proton-acceptable lone pair electrons on N atom should be incorporated into LB and (ii)
the N-protonated species should stabilize its positive charge rather preferably by a
delocalization in π-electronic cyclic system of the benzene ring to by an extension in
π-electronic conjugation with the extended πES constituent over the molecule. And, just
recently, an electronically mobile but thermally stable 1,4-phenylene moiety like in the
anthracene (Anth) ring has been found much effective for dramatic reformation of the
electronic structure of the OEP ring, potentially providing a promising transmissible

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spacer to respond with much smaller energy stimuli.16 Therefore, along the line obtained
from this study, further study of the new OEP-Anth-LB derivatives in place of DHBTh
is now in progress, aiming at further visually sophisticated proton-mediated OEP system
with the much greater outputs such as chromic effect and shift.
Experimental
Melting points (Mp.) were determined on a hot-stage apparatus and are uncorrected.
The EI and FAB mass spectra were recorded with a JEOL JMS-700 spectrometer, and
the ESI-FT-ICR mass spectra were performed with a Bruker BioAPEX 70e
spectrometer equipped with a 7 T superconducting magnet, using a sample in a solution
of CHCl3-MeOH (3:2). IR spectra were measured on a Jasco FT/IR 7300
spectrophotometer as KBr disk or neat sample; only significant absorptions are recorded
in ν value (/cm-1).17 1H NMR spectra were measured in CDCl3 solution on a JEOL
ECX-300A (300 MHz) or a JEOL JMN-EPC 600 (600 MHz) spectrometer, and were
recorded in δ value (/ppm) with TMS as an internal standard, unless otherwise specified.
Similarly, 13C NMR spectra of all the new compounds (Scheme 1) were measured on a
JEOL JMN-EPC 600 (150 MHz) spectrometer, in which their signals were not certainly
assigned to each carbon yet.17 The coupling constants (J) are given in Hz. Electronic
absorption spectra were measured in CHCl3 solution on a Shimadzu UV-2200A
spectrophotometer and absorption maxima of respective bands are reported in λmax
value (/nm) with their extinction coefficient (ε) (sh=shoulder). SiO2 (Fujisilysia BW
820MH or BW 127ZH) was used for column chromatography, unless otherwise stated.
Reactions were followed with TLC on aluminum sheets precoated with Merck SiO2 F254
or with Merck alumina (Al2O3) GF254. Organic extracts were dried over anhydrous
sodium sulfate (Na2SO4) or magnesium sulfate (MgSO4) prior to removal of the
solvents.
All the terminal acetylenes 5-8 as the coupling reactants for the new isomeric
compounds of 3 and 4 were prepared, by a tandem reaction of the corresponding bromo
derivatives with trimethylsilylacetylene (TMS-acetylene) under the Sonogashira
cross-coupling conditions18 and the deproctection of TMS group with K2CO3/MeOH,
according to our conventional way.3,4,6 The general preparation procedure for the
terminal acetylenes is shown as follows, taking a typical example of 8.
3,5-Bis(N,N-dimethylamino)phenylacetylene (8): To a solution of 1-bromo-3,5-

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bis(N,N-dimethylamino)benzene19 (544 mg, 2.3 mmol), (Ph3P)2PdCl2 (32 mg, 0.045
mmol), and CuI (9.3 mg, 0.049 mmol) in diisopropylamine (20 cm3) was added
TMS-acetylene (1.28 cm3, 9.5 mmol). The mixture was stirred at ambient temperature
for 10 h. The reaction mixture was poured into water and extracted with CHCl3. The
extracts were washed with brine and then dried. The residue obtained after removal of
the solvent was passed through a short column on SiO2. A solution of the crude mixture
was stirred in MeOH-THF (90 cm3, 2:1) containing K2CO3 (430 mg, 3.1 mmol) at
ambient temperature under Ar atmosphere for 10 h. Poured into water, the reaction
mixture extracted with CHCl3. The residue was chromatographed on Al2O3 (Wako,
Alumina 90) short column with ethyl acetate to afford 8 (287 mg, 68%) as brownish oil.
8: MS (EI) m/z 189 (M++1) for C12H16N2 (MW 188.27, based on H=1.008); IR (nujol) ν
1
3314 (C:::CH), 2110 (C:::C); H NMR δ 6.30 (2H, d, J=2.4, Ar-H), 6.04 (1H, t, J=2.4,
Ar-H), 2.93 (1H, s, C:::CH), 2.92 (12H, s, NCH3); Uv-vis λmax 242 (13800), 273 (9900),
352 (4850), 395 (2250, sh) with weak absorption band tailing up to 700 nm.
54: 78% yield. Dark bluish green powder (CHCl3-methanol); Mp. 255-260 C (dec); MS
(FAB) m/z 997.1 (M++1) for C62H72N4S2Ni (MW 996.07, based on Ni=58.69); IR (KBr)
ν 3310 (C:::CH), 2145 (C:::C); 1H NMR δ 9.42 (2H, s, meso-H), 9.39 (1H, s, meso-H),
7.28 (1H, s, Th-H), 7.16 (1H, s, Th-H), 4.13 (4H, q, J=7, CH2), 3.81-3.77 (12H, qm,
CH2), 3.39 (1H, s, C:::CH), 2.49 (4H, tm, Th-CH2), 1.81-1.71, 1.25-0.87 (46H, m, CH3
and Th-CH2CH2CH2CH2CH2CH3).
64: 83% yield. Dark bluish green microcrystallines (CHCl3-methanol); Mp. 273-280 C
(dec); MS (FAB) m/z 997.0 (M++1) for C62H72N4S2Ni (MW 996.07, based on
1
Ni=58.69); IR (KBr) ν 3300 (C:::CH), 2140 (C:::C); H NMR δ 9.42 (2H, s, meso-H),
9.39 (1H, s, meso-H), 6.97 (1H, s, Th-H), 6.96 (1H, s, Th-H), 4.13 (4H, q, J=7, CH2),
3.82-3.77 (12H, qm, CH2), 3.53 (1H, s, C:::CH), 2.77 (2H, t, J=7, Th-CH2), 2.67 (2H, t,
J=7, Th-CH2), 1.81-1.72, 1.66-0.87 (46H, m, CH3 and Th-CH2CH2CH2CH2CH2CH3).
710: 77% yield. Pale yellow oil; MS (EI) m/z 145 (M+) for C10H11N (MW 145.20, based
on H=1.008); IR (Nujol) ν 3311 (C:::CH), 2110 (C:::C); 1H NMR; δ 7.17 (1H, td, J=8.1
and 0.8, Ar-H), 6.90-6.81 (2H, m, Ar-H), 6.71 (1H, br d, J=8.1 Ar-H), 3.01 (1H, s,
C:::CH), 2.94 (6H, s, NCH3).
All the OEP-DHBTh-DMAB isomeric derivatives of 3 and 4 were synthesized by our
conventional way.4 As a typical reaction procedure, the synthesis of 3HH is described in
the following. A mixture of 54 (80 mg, 0.08 mmol) and 710 (116 mg, 0.8 mmol, 10 eq. to

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5) in a mixed solution of pyridine and MeOH (5:1 in v/v, 150 cm3) was added dropwise
at 40 C with stirring into a solution of pyridine and MeOH (5:1, 50 cm3) containing an
excessive amount of Cu(OAc)2 (728 mg, 4.0 mmol) over 1.5 hr. Then, the reaction
mixture was kept stirring at 40 C for 12 hr. Poured into water, the reaction mixture was
extracted with CHCl3. The extracts were washed with diluted HCl aq., with brine
several times successively, and then dried. After removal of the solvents under reduced
pressure, the residue obtained was chromatographed on SiO2 column with
hexane-CHCl3 (4:1) as an eluent, to afford DMAB homo-dimer 10, desired compound
3HH, and OEP-DHBTh homo-dimer 9HH in order.
1010: 33% yield (from the reaction for 3HH) and 25% yield (from the reaction for 3TT).
Pale yellow plates (benzene); Mp. 160-165 C; MS (EI) m/z 288 (M+) for C20H20N2
1
(MW 288.38, based on H=1.008); IR (KBr) ν 2136 (C:::C), 1593 and 1563 (C::C); H
NMR; δ 7.19 (2H, tm, J=8.5, A-H), 6.88 (2H, dm, J=8.5, Ar-H), 6.87 (2H, bs, Ar-H),
6.73 (2H, dm, J=8.5, Ar-H), 2.97 (12H, s NCH3); Uv-vis λmax 296 (17800, sh), 313
(19800), 326 (17100) and 359 (7600, sh).
3HH: 35% yield. Black purple microcrystallines (CHCl3-methanol); Mp. over 280 C
(dec); MS (FAB) m/z, 1139.0 (M+) for C72H81N5S2Ni (MW 1139.25, based on
Ni=58.69); IR ν 2921 and 2853 (C-H), 2183 and 2130 (C:::C); 1H NMR; δ 9.42 (2H, s,
meso-H), 9.40 (1H, s, meso-H), 7.29 (1H, s, Th-H), 7.21 (1H, s, Th-H), 7.20 (1H, dd,
J=8.0 and 7.5, Ar-H), 6.88 (1H, d, J=8.0, Ar-H), 6.77 (1H, br s, Ar-H), 6.74 (1H, d,
J=7.5 Ar-H), 4.18-4.08 (4H, qm, J=6.5, CH2), 3.82-3.75 (12H, qm, CH2), 2.96 (6H, s,
NCH3), 2.52 (4H, tm, Th-CH2), 1.82-1.70, 1.57-1.25, and 0.90-0.86 (46H, CH3 and
Th-CH2CH2CH2CH2CH2CH3); 13C NMR; δ 145.7(8), 145.0(5), 144.6(7), 143.7(5),
143.2(7), 143.0(0), 142.1(8), 140.3(3), 140.1(4), 137.7(5), 133.3(6), 130.8(8), 128.8(1),
126.6(8), 123.5(5), 120. 0(8), 115.8(6), 111.3(4), 108.6(3), 107.3(5), 106.0(7), 97.9(4),
96.3(3), 93.8(8), and 92.6(3) for the sp2-C, 85.7(8), 85.6(8), 80.4(5), 78.6(4), 74.5(1),
74.1(4), 73.1(3) and 72.5(0) for the sp-C, 40.4(0), 32.1(2), 31.6(0), 31.2(7), 30.6(1),
30.3(8), 29.7(1), 28.9(6), 28.8(6), 24.5(2), 23.7(6), 22.6(9), 22.5(7), 22.4(1), 21.7(4),
19.5(4), 19.4(7), 18.1(5), 17.2(8), 14.1(3), and 14.0(7) for the sp3-C; Uv-vis λmax 346
(34800), 449 (126000), 572 (13200, sh) and 590 (14300).
9HH13: 18% yield. Black microcrystallines (CHCl3-methanol); Mp. over 300 C; MS
(ESI-FT-ICR) m/2z 994.94 (M+) for C124H142N8Ni2S4 (MW 1990.01, based on

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1
Ni=58.69); IR (KBr) ν 2150 and 2125 (C:::C); H NMR (THF-d8) δ 9.48 (4H, s,
meso-H), 9.46 (2H, s, meso-H), 7.44 (2H, s, Th-H), 7.37 (2H, s, Th-H), 4.16 (8H, q,
J=6.5, CH2CH3), 3.87-3.78 (24H, qm, CH2CH3), 2.57-2.51 (8H, tm, Th-CH2), 1.84-1.24
and 0.92-0.86 (92H, m, OEP-CH2CH3 and Th-CH2CH2CH2CH2CH2CH3).
Similarly, the oxidative cross-coupling reaction between 64 and 710 afforded the
TT-DHBTh isomer 3TT, together with 9TT and 1010.
3TT: 23% yield. Black purple microcrystallines (CHCl3-methanol); Mp. over 280 C
(dec); MS (FAB); m/z, 1138.9 (M+) for C72H81N5S2Ni (MW 1139.25, based on
Ni=58.69); IR ν 2924 and 2868 (C-H), 2178 and 2128 (C:::C); 1H NMR; δ 9.42 (2H, s,
meso-H), 9.39 (1H, s, meso-H), 7.20 (1H, dd, J=8.1 and 7.5, Ar-H), 6.99 (1H, s, Th-H),
6.97 (1H, s, Th-H), 6.90 (1H, d, J=8.1 Ar-H), 6.87 (1H, br s, Ar-H), 6.76 (1H, d, J=7.5,
Ar-H), 4.14-4.10 (4H, qm, CH2), 3.82-3.75 (12H, qm, CH2), 2.96 (6H, s, NMe-H), 2.75
(2H, t, J=8.0, Th-CH2), 2.71 (2H, t, J=8.0, Th-CH2), 1.82-1.71, 1.56-1.25, and 0.95-0.86
(46H, CH3 and Th-CH2CH2CH2CH2CH2CH3); 13C NMR; δ 151.9(0), 151.7(3), 150.2(2),
145.7(4), 144.9(4), 143.7(0), 142.9(8), 142.1(4), 140.3(0), 140.1(6), 137.7(8), 137.7(3),
129.1(4), 125.3(2), 125.0(8), 122.0(6), 120.5(8), 117.3(2), 116.8(8), 115.7(9), 113.7(7),
97.9(1), 97.7(8), 92.6(8) and 91.1(5) for the sp2-C, 86.0(1), 86.0(0), 85.0(6), 82.4(8),
81.8(1), 81.3(9), 73.8(3) and 72.9(4) for the sp-C, 40.3(6), 31.6(2), 30.2(2), 30.2(0),
30.0(0), 29.8(0), 29.7(1), 29.0(1), 28.9(0), 22.6(3), 22.6(1), 21.7(7), 19.5(3), 19.5(1),
19.5(0), 18.1(5), 18.2(0), 17.3(0), 17.2(2), 14.1(2) and 14.1(1) for the sp3-C; Uv-vis λmax
368 (28500), 406 (46400, sh), 461 (102000), 474 (109000), 570 (14200, sh) and 596
(21800).
9TT13: 30% yield. Black microcrystallines (CHCl3-methanol); Mp. over 300 C; MS
(ESI-FT-ICR) m/2z 994.95 (M+) for C124H142N8Ni2S4 (MW 1990.01, based on
1
Ni=58.69); IR (KBr) ν 2150 and 2125 (C:::C); H NMR (THF-d8) δ 9.51 (4H, s,
meso-H), 9.49 (2H, s, meso-H), 7.24 (2H, s, Th-H), 7.22 (2H, s, Th-H), 4.18 (8H, q,
J=6.6, CH2CH3), 3.89-3.81 (24H, qm, CH2CH3), 2.83 (4H, t, J=7.5, Th-CH2), 2.75 (4H,
t, J=7.5, Th-CH2), 1.85-1.29 and 0.93-0.88 (92H, m, OEP-CH2CH3 and
Th-CH2CH2CH2CH2CH2CH3).
The derivatives of 4HH and 4TT were synthesized by the cross-coupling reaction
between 8 and 5 or 6, according to the same procedure as for the derivative 3HH.
4HH: 28% yield. Black purple microcrystallines (CHCl3-methanol); Mp. over 280 C
(dec); MS (FAB) m/z, 1181.7 (M+) for C74H86N6S2Ni (MW 1182.32, based on

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1
Ni=58.69); IR ν 2922 and 2854 (C-H), 2182 and 2132 (C:::C); H NMR δ 9.42 (2H, s,
meso-H), 9.39 (1H, s, meso-H), 7.28 (1H, s, Th-H), 7.19 (1H, s, Th-H), 6.35 (1H, s,
Ar-H), 6.09 (1H, s, Ar-H), 4.16-4.08 (4H, qm, CH2), 3.82-3.77 (12H, qm, CH2), 2.94
(12H, s, NMe-H), 2.51 (4H, tm, Th-CH2), 1.82-1.70, 1.56-1.25, and 0.89-0.85 (46H,
CH3 and Th-CH2CH2CH2CH2CH2CH3); 13C NMR; δ 145.7(8), 145.0(6), 144.4(7),
143.7(5), 142.9(9), 142.1(8), 140.3(3), 140.1(4), 137.7(5), 137.1(9), 133.3(6), 130.8(8),
128.8(1), 126.6(8), 123.5(5), 120. 0(8), 115.7(9), 111.3(4), 106.0(7), 97.9(3), 97.0(2),
94.0(4), and 93.0(3) for the sp2-C, 86.9(3), 86.4(8), 79.3(6), 78.7(8), 74.4(5), 74.1(4),
73.8(3) and 72.5(0) for the sp-C, 40.6(5), 31.9(3), 31.6(0), 31.2(7), 30.5(5), 30.3(8),
29.7(1), 28.9(4), 28.8(6), 24.5(2), 23.7(6), 22.6(9), 22.5(8), 22.4(1), 21.7(5), 19.5(4),
19.4(7), 18.1(4), 17.2(9), 14.1(2), and 14.0(1) for the sp3-C; Uv-vis λmax 352 (26500),
378 (25700), 449 (90000), 568 (14600, sh) and 593 (10500).
4TT: 32% yield. Black purple microcrystallines (CHCl3-methanol); Mp. over 280 C
(dec); MS (FAB); m/z, 1181.6 (M+) for C74H86N6S2Ni (MW 1182.32, based on
1
Ni=58.69); IR ν 2925 and 2853 (C-H), 2178 and 2129 (C:::C); H NMR δ 9.42 (2H, s,
meso-H), 9.39 (1H, s, meso-H), 6.99 (1H, s, Th-H), 6.97 (1H, s, Th-H), 6.90 (1H, d,
J=8.1 Ar-H), 6.35 (2H, br s, Ar-H), 6.08 (1H, br s, Ar-H), 4.17-4.12 (4H, qm, CH2),
3.82-3.77 (12H, qm, CH2), 2.95 (12H, s, NMe-H), 2.77 (2H, t, J=8.0, Th-CH2), 2.72
(2H, t, J=8.0, Th-CH2), 1.82-1.71, 1.57-1.25, and 0.91-0.86 (46H, CH3 and
Th-CH2CH2CH2CH2CH2CH3); 13C NMR; δ 151.6(9), 151.3(4), 145.6(9), 144.8(8),
143.6(6), 142.9(2), 142.1(1), 140.2(7), 140.1(3), 137.7(3), 137.6(9), 125.2(1), 125.0(1),
122.0(9), 117.1(8), 116.9(8), 105.9(2), 98.6(7), 98.2(0), 97.8(7), 97.7(4), 92.6(6), and
91.1(5) for the sp2-C, 87.1(3), 85.0(2), 82.7(8), 82.0(0), 81.4(2), 73.1(8), 71.8(9) and
67.7(7) for the sp-C, 40.6(2), 31.5(9), 30.3(5), 30.1(2), 29.9(3), 29.7(4), 29.6(9), 28.9(1),
23.7(3), 22.9(7), 22.6(1), 22.5(9), 21.7(6), 19.5(1), 19.4(8), 19.4(3), 18.1(5), 18.1(3),
17.2(2), 14.1(2) and 14.0(9) for the sp3-C; Uv-vis λmax 368 (19500), 406 (31400, sh),
451 (61000), 476 (66000), 570 (16100, sh) and 595 (15000).
11: 37% yield (from the reaction for 4HH) and 25% yield (from the reaction for 4TT);
Pale yellow plates (CHCl3-hexane); Mp. 182-188 C; MS (EI) m/z, 374 (M+) for
C24H30N4 (MW 374.52, based on H=1.008); IR ν 2139 (C:::C), 1592 and 1572 (C::C);
1H NMR δ 6.34 (4H, d, J=2.4, Ar-H), 6.07 (2H, t, J=2.4, Ar-H), 2.93 (24H, s, NCH3);
13C NMR; δ 151.3(4), 112.4(3), 106.1(7) and 98.5(6) for the sp2-C, 82.8(0) and 72.0(3)

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for the sp-C, 40.6(6) for the sp3-C; Uv-vis λmax 295 (17200, sh), 322 (17500), 343
(17200) and 376 (7740, sh).
The spectral change experiments with TFA: both electronic absorption and 1H NMR
spectral measurements were carried out at 25 C, 10 min after preparation of the sample,
as shown in the following procedure. For electronic absorption spectra; the 4 cm3
solutions of OEP-DHBTh-LB (3; 0.35 mg, 4; 0.37 mg, both ca. 3.1 x 10-4 mmol
dissolved in 10 cm3 CHCl3) were admixed with TFA (d=1.53 g/cm3) in each equivalent
ratio (Fig. 2), and then diluted with CHCl3 to adjust their sample concentration adequate
for electronic absorption spectral measurements (total 5 cm3, both ca. 2.5 x 10-5 mol/103
cm3 for OEP- DHBTh-LB). For 1H NMR spectra; OEP-DHBTh-LB (3; 4.78 mg and 4;
5.02 mg, both ca. 4.25 x 10-3 mmol) was admixed with the stock solution of TFA (965
mg=8.46 mmol dissolved in 1 cm3 CDCl3) in each equivalent ratio (Figs. 3 and 4), and
1
then diluted with CDCl3 to adjust their sample concentration adequate for H NMR
(total 0.5 cm3 CDCl3, ca. 8.5 x 10-3 mol/103 cm3 for OEP-DHBTh-LB).
Acknowledgments
Financial support by a Grant-in-Aid for Scientific Research from the Ministry of
Education, Science, Sports, Culture and Technology (Nos. 23550046 and 26410039), is
gratefully acknowledged. HH is also grateful to Center of Instrumental Analyses at
University of Toyama for their supporting measurements of physical properties of the
new compounds.
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15. To our best knowledge, the pKa(1) and pKa(2) values of conjugated acid
1,3-bis(N,N-dimethylamino)benzene are unknown yet. The pKa value (4.58) of
conjugated acid, aniline-H+ with aniline in water at 25 C, is known to be slightly
smaller, i.e., a little higher acidity, as compared with that of 5.15 between DMAB
and DMAB-H+.7 Thus, based on this fact, the pKa(1) and pKa(2) values of the
conjugated acid of 1,3-bis(N,N-dimethylamino)benzene could be expected to be