Meso -1,4-phenylene bridged nickel norcorrole dimer

Article abstract of DOI:10.1142/S1088424619501074

Nickel norcorrole dimer 3 linked with a phenylene bridge was prepared by a nickel-mediated homolytic cross-coupling of meso-phenylene bisdipyrrin nickel(II) dimer 2b. The structures of 2b and 3 were elucidated by X-ray diffraction analysis. Each nickel norcorrole fraction of the nickel norcorrole dimer 3 exposed a bowl-like structure, which conserved anti-conformation. Structural distinctions between the monomeric and dimeric nickel norcorroles were established by vibrational spectroscopic analysis and assessed with density functional theory calculations. Enhanced flexibility of the norcorrole planes in solution states of monomeric nickel norcorrole was compromised to that of bowl-shaped norcorroles in the solid states of nickel norcorrole dimer 3, where C2v was the formulated conformation. The deformation of the planarity derived from the objection of laser pulses effectuated vibration shifts of specific Raman-active motions toward a higher-frequency region, as associating with a paratropic nature of the π-electron delocalization circuit of norcorrole. Computational simulation exposed a reliable drift of the Raman frequencies.

Full text of DOI:10.1142/S1088424619501074

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2019; 23: 1–9
DOI: 10.1142/S1088424619501074
Published at http://www.worldscinet.com/jpp/
Meso-1,4-phenylene bridged nickel norcorrole dimer
Ji-Young Shin*
Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering,
Nagoya University, Nagoya 464-8603, Japan
Dedicated to Professor Atsuhiro Osuka on the occasion of his 65th birthday.
Received 28 May 2019
Accepted 23 July 2019
ABSTRACT: Nickel norcorrole dimer 3 linked with a phenylene bridge was prepared by a nickel-
mediated homolytic cross-coupling of meso-phenylene bisdipyrrin nickel(II) dimer 2b. The structures
of 2b and 3 were elucidated by X-ray diffraction analysis. Each nickel norcorrole fraction of the nickel
norcorrole dimer 3 exposed a bowl-like structure, which conserved anti-conformation. Structural
distinctions between the monomeric and dimeric nickel norcorroles were established by vibrational
spectroscopic analysis and assessed with density functional theory calculations. Enhanced flexibility
of the norcorrole planes in solution states of monomeric nickel norcorrole was compromised to that of
bowl-shaped norcorroles in the solid states of nickel norcorrole dimer 3, where C2v was the formulated
conformation. The deformation of the planarity derived from the objection of laser pulses effectuated
vibration shifts of specific Raman-active motions toward a higher-frequency region, as associating with
a paratropic nature of the p-electron delocalization circuit of norcorrole. Computational simulation
exposed a reliable drift of the Raman frequencies.
KEYWORDS: norcorrole, nickel complex, crystal structure, dimer, antiaromaticity, vibration
spectroscopy.
enhanced by the metal coordination. Norcorrole first was
introduced in a DFT analysis by Ghosh and coworkers
INTRODUCTION
Conformational distortion of the p-conjugated system
in 2005 [10] and a further-stabilized dimerization of
has had an increase in interest due to the dynamics of
norcorrole was reported in his recent research [11].
their electronic configurations [1]. Porphyrins that exhibit
The first isolation and spectroscopic characterization
18p-electronconjugationnetworksstabilizetheelectronic
of norcorrole was succeeded with Fe(III) norcorrole by
configurations by the delocalization of p electrons [2].
Bröring et al. in 2008 [12]. Shinokubo and coworkers
Vibrations of the porphyrin skeletons arising from
have reported an efficient gram-scale synthetic method
artificial bulky substituents such as saddling, waving, and
of NiNC, which also promoted further investigations
twisting have been induced with spectroscopic methods
[13–16]. The main skeleton of norcorrole exhibited
[3–7]. Notably, captivations deliberated from their
conformational dependencies upon the chelated metals
powerful aromatic features, various metal coordination
due to its smaller cavity compared to the cores of typical
capabilities as well as their abundance in nature are
porphyrins [16]. A highly planar structure of mesityl
all aspects that have inspired the various biochemical/
NiNC was elucidated by X-ray diffraction analysis [13].
biotechnological investigations [8, 9].
Cu(II) norcorrole exposed a higher planarity than both
Nickel norcorrole (NiNC) has been introduced as
free-base and Pd(II) norcorroles, in which significant sets
a unusually stable antiaromatic molecule exhibiting
of resolved signals were detected in hyperfine and super-
a 16p-electron conjugation, whose stabilization was
hyperfine couplings of single unpaired electrons with Cu
(I = 3/2) and four Ns (I = 1/2) nuclei, respectively due to
the small norcorrole cavity. Furthermore, the palladium
norcorrole exhibited a substantial level of antiaromaticity
*Correspondence to: Ji-Young Shin, tel.: +81 52-789-3188,
e-mail: jyshin@chembio.nagoya-u.ac.jp.
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J.-Y. SHIN
and a bowl shape. NiNC has shown common antiaromatic
behaviors and proficiency for practical applications such
as active electrode materials in organic batteries [17, 18].
NiNC has been developed to dimeric NiNCs. In 2015,
Chmielewski and coworkers reported that hydrogenation
of NiNC in the presence of Raney nickel produced a
highly hydrogenated species, and advanced oxidation of
the species with p-chloranil yielded a heterodimerized
NiNC molecule [19]. Homodimerized NiNC molecules
have also been introduced in recent research by
Shinokubo and coworkers [20]. However, NiNCs that
were linked by meso-arylene were not reported. A
convenient synthetic method of NiNC dimers having
simple 1,4-phenylene linkers was accomplished as
shown in Scheme 1. Herein, we prepared a novel NiNC
dimer 3 having a 1,4-phenylene linker whose molecular
structure was elucidated by X-ray diffraction analysis
(Scheme 1). The unique antiaromatic behaviors of NiNC
are still detected with the NiNC dimer 3. Furthermore, an
enhanced/upright implementation of interacting waves
of two NiNC fractions was investigated in comparison
with the spectroscopic performance of the monomeric
NiNC origin. Spectral analysis and computational
calculation were also investigated for the confirmation of
coherence between the actual analysis and the theoretical
calculation.
Scheme 2. Preparation method of the precursor 2b for the
meso-phenylene bridged NiNC nickel complex dimer 3
features through metal coordination. Tetrahedral nickel
complexes exhibit paramagnetic properties due to the
two unpaired d-orbital electrons of the nickel center,
whose hyperfine (electron-nuclear) couplings enlarge the
range of the magnetic field. The degree of the dihedral
angles between two nickel-chelated dipyrrin-planes plays
an essential role in associating the magnetic distinction
[21–23]. The steric factor on external a positions of
pyrroles is, therefore, the key controlling the distorted
angles as well as the magnetic behaviors of nickel
complexes. Metal coordination of dipyrrin dimers often
resulted in high degree polymerizations [24]. On the
other hand, such cascades are inhibited by interruptions
of monomeric dipyrrins, which become the terminating
blocks of polymers. a,a′-dibromodipyrrin dimer 1 was
associated with the nickel complexation of meso-mesityl-
a,a′-dibromodipyrrin, which acts as a controller of the
metallation degree (Scheme 2). Modifications to the
synthetic method somewhat improved the yield of the
target product 2b. However, the result of the reaction was
still a mixture of the products, 2a–2d, having a different
degrees of Ni-metallations. Precursor 2b was then
conducted to the nickel-mediated homo coupling to form
the nickel norcorrole dimer 3 (Scheme 1).
RESULTS AND DISCUSSION
The precursor 2b was prepared in a similar method
to that earlier reported in the literature (Scheme 1) [21].
Tetradentate nickel complex dimer 2b was then conducted
to the nickel-mediated homo coupling to produce the
target, nickel norcorrole dimer 3 (Scheme 1). Tetradentate
nickel complexes have responded distinctly to external
magnetic fields in accordance with distorted angles of
the coordination ligands. Dipyrrins are monoanionic
and bidentate ligands that form neutral complexes with
numerous metal ions and have shown self-assembling
Single crystals of 2b were grown in an CH2Cl2 solution
by a vapor diffusion of n-hexane (Fig. 1) [25].Alignments
of the molecular units revealed a channel in the unit
lattices. Hexane solvent molecules were disordered to
fill the space of channels and located close to each other
(Fig. S1). The growth of single crystals of 2c was also
accomplished successfully in the same solvent system
chosen for 2b (Fig. 2) [26]. No solvent molecule was
Scheme 1. Nickel-mediated reductive coupling of dipyrrin
nickel complex dimer 2b toward meso-phenylene NiNC dimer 3
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Meso-1,4-PHENYLENE BRIDGED NICKEL NORCORROLE DIMER
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Fig. 1. Crystal structures of the bisdipyrrin Ni(II) complex dimer 2b: Thermal ellipsoids are scaled at the 50% probability level
Fig. 2. Crystal structure of the bisdipyrrin Ni(II) complex trimer 2c: Thermal ellipsoids are scaled at the 50% probability level
found in the crystal lattice. Loss of the linearity of the
overall structure as the degree of metallation increased
was significant.
distance from one side terminal mesityl to the other
terminal mesityl (approximately, 0.7 Å was shortened).
The packing diagram of the crystal is presented in
Fig. 4, in which intermolecular stacking was observed
in each half-molecular shifted position. The distance
between the terminal mesityl carbons in 2b was 30.891 Å
while the distance in the crystal data of NiNC dimer 3
was 30.126 Å. The solubility of 3 in particular organic
solvents was drastically reduced after the crystallization.
The well-aligned packing was perhaps a critical reason
for the reduced solubility.
Moreover, very few single crystals of hemi-molecule of
2c were obtained in the same sample for the crystal growth
of 2c [27]. The crystal shape and color of hemi-molecule
of 2c were precisely distinguishable with those of 2c
crystals. Since only a few crystals of the hemi-molecule
were found, it was presumed that the demetallation of the
central nickel happened in a tiny amount during a long-
term process of the single-crystallization.
Preparation of 3 was successful in nickel mediated
cross coupling of the precursor 2b by using the consistent
method of NiNC [13] and it was improved by the use
of 2,2′-bipyridine and Ni(cod)2 to a ca. 30% yield.
The growth of single crystals of 3 was successful in a
reversible vapor diffusion of methanol and chloroform.
The molecular structure of the NiNC dimer was then
elucidated by the crystallographic method [28]. No
solvent molecule was found in the unit lattice. The
structure of dimeric NiNC projected an immense
distinction to the structure of monomeric NiNC, in which
the main norcorrole planes bulged in opposite vectoring
axial directions from the nickel centers. As a result,
the overall dimeric structure presented waved planes,
exposing a particular interaction between the two NiNC
segments. As shown in Fig. 3, the structure of 3 showed a
curved plane for each unit, which resulted in a shortened
All dipyrrin nickel complexes 2a–2d exhibited
extended ranges of chemical shifts (-5.1–60 ppm) in
1
the respective H NMR spectra (Fig. S5). On the other
1
hand, the H NMR spectrum of the norcorrole dimer 3
presented its proton peaks in a range typical of chemical
shifts for diamagnetic Ni complexes. The spectral data
awarded symmetric configuration of the two reflecting
NiNC units centering the 1,4-phenylene bridge, in which
a paratropic ring current of antiaromatic norcorrole
was observed (Fig. S6). Four doublets at 2.00, 1.52,
1.49, and 1.41 ppm were assigned as the peaks of bHs
of norcorrole. HH COSY NMR (Fig. S7) exposed two
respective correlations for the sets of the doublets.
As shown in Fig. 5, the overall pattern of absorption
bands for 3 overlapped mostly with the absorption bands
of NiNC monomer. Those were somewhat broadened and
extended over 1100 nm. The broad absorptions express
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J.-Y. SHIN
Fig. 3. Crystal structure of 3: (a) top view and (b) side view. Thermal ellipsoids are scaled at the 50% probability level
Fig. 4. Packing diagram of NiNC dimer 3: (a) top view and (b) side view. Thermal ellipsoids are scaled at the 50% probability level
intermolecular interaction. The molecular arrangement
observed in a crystalline state (Fig. 4) could be a frozen
conformation. Intermolecular interactions would be
enhanced with the enlarged molecular surfaces in the
NiNC dimer. The TD-DFT calculation data was in
high agreement with the measured absorptions (Fig. 6).
As the concentration of 3 increases in CH2Cl2 solutions,
the absorbance of the absorption band, appearing at the
long wavelength area, was enhanced. Furthermore,
the absorption band up to 1100 nm was retained in the
absorption spectra, even with a very diluted CH2Cl2
Fig. 5. Absorption spectra of 3 and NiNC monomer in CH2Cl2
solution of 3.
The cyclic voltammogram of 3 shown in Fig. 7
was associated with a 1.0 V/s scan rate. The cyclic
voltammogram of 3 proposed stepwise oxidation of four
electrons and stepwise reduction of four electrons. A
split of the first oxidation potential was observed. It is
hypothesized that an imbalanced two-electron oxidation
precise interactions between the NiNC units through
the covalently linked phenylene. The forbidden S0–S1
transition was buried in an extended wavelength area in
the monomeric NiNC, which was appreciated with the
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Meso-1,4-PHENYLENE BRIDGED NICKEL NORCORROLE DIMER
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symmetric center (nickel for NiNC and 1,4-phenylene for
the NiNC dimer 3). Out-of-plane vibration of meso-aryls
at 748 cm-1, with motion aligning in the same direction
were split into two vibrations, one for the external
meso-mesityls and the other for 1,4-phenylene. This
is due to the better planarity of norcorrole than of the
bisdipyrrin Ni(II) complex. Three meso-aryls of 2b are
largely distorted. The dihedral angles increased among
the aryl planes compared to the angles for the meso-
aryls of 3. Two vibration bands of 3 are found at 739
and 743 cm-1 (Fig. S22). On the other hand, bisdipyrrin
nickel complexes 2a and 2b disclosed an identical pattern
of IR-responded vibration bands between monomer and
dimer (spectra a and b) in the FT-IR spectra, as judging
from the sum of the vibrations of two independent
monomeric metal complexes. Changes of the vibration
energies were understood to be a bumped-up orientation
of the nickel center of NiNC in 3, where out-of-plane
vibrations were created. A different composition of the
dipole moments at the two metal coordination sites gave
rise to the change of vibration energies and appearance of
new vibration bands.
Resonance Raman spectroscopy resulted in resembled
Raman-active bands for a CH2Cl2 solution of NiNC and
a crystalline sample of 3. On the other hand, both CH2Cl2
solution and crystalline state of NiNC contributed
the reliable vibration sequences in the Raman spectra
(spectra a and c in Fig. S14). The strong correlation
between structural distortions of nickel porphyrins and
their consequent vibration bands was reported by Dietsek
and coworkers [29]. Core-size marker lines are one of
the most significant sequences for the recognition of
the structural relationship of either the molecular core
sizes or Ni–N distances and the vibration frequencies
of the group. The associated results were reported with
tetrapyrrole-containing, Ni-chelated proteins, whose
vibrations have been observed in ~1300–1500 cm-1 [30]:
Fingerprint regions were considered to account for the
types of oop (out-of-plane) distortions. The distortion
momentum commenced shifts of the structural sensitive
ip (in-plane) modes to lower frequencies. Compared with
porphyrins, norcorrole has a condensed core size whose
complexes bear high repulsions between the electrons
filled in d-orbitals of nickel and the ligation electrons
donated from four Ns of norcorrole. Raman resonance
sequences of the high planar NiNC whose structure was
Fig. 6. TD-DFT spectra of 3 in CH2Cl2: (a) measured and
(b) calculated (TD-DFT/B3LYP/SDD) spectra
proceeded. Once both NiNC segments were oxidized,
with one electron each, a second oxidation happened
identically with a reversible redox potential. However,
the first reduction involving two electrons happened
equally and reversibly and the second reductions were
imbalanced (Fig. S11). When the measurement was
speed up (0.05 V/s to 0.1 V/s), the second reduction
potentials became irreversible, and further speeding up
broadened and flurried the reduction potentials, which
were eventually undetectable. The HOMO–LUMO
gap of 3 (the difference of the first oxidation and first
reduction potentials) was slightly smaller than that of
NiNC monomer (0.92 V and 1.08 V for 3 and NiNC,
respectively).
Vibration spectroscopic experiments were attempted in
ordertorationalizethestructuraldynamics.Measurements
of the vibration bands were accompanied with single
crystals of the corresponding molecules. Figure 8 shows
the FT-IR spectra of the precursors of NiNC monomer
and NiNC dimer 3 and the NiNC molecules in solid states.
Those crystalline states of monomeric NiNC and dimeric
3 resulted in characteristically distinct vibration bands
(Figs 8c and 8d) in the FT-IR spectra (Fig. 8), as judging
from the partial alternation in between those structures.
Some single vibration bands that appeared in Fig. 8c were
found as two separated vibration bands in Fig. 8d. For
example, a symmetric and in-plane scissoring vibration
was split into two vibration bands due to the different
Fig. 7. Cyclic voltammograms of 3 in CH2Cl2 (0.1 MnBu4NPF6). Working electrode: glassy carbon, counter electrode: Pt, reference
cell: Ag/AgCl4, and Fc/Fc+: ferrocene/ferrocenium couple
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J.-Y. SHIN
Fig. 8. FT-IR spectra of (a) 2a, (b) 2b, (c) NiNC monomer, and
(d) 3, measured in respective neat solid states and zoomed in at
a range of 400–2000 cm-1
Fig. 9. Low Frequency region of the 532 nm excited Resonance
Raman spectra of NiNC monomer in CH2Cl2 solution: (a) 1st time
and (b) 2nd time laser excitations (5 scans with 15 s irradiation
interval)
supported by crystallographic results gave an opposite
observation to nickel porphyrin. Ni(II) is suitable to fit in
the core of norcorrole due to the reduced size of the core
in the absence of two meso-methines, which provide a
planar structure with a minimum N–Ni distance. The N–
Ni distance increases with the formation of bowl-shaped
NiNC because of the bump-up orientation of the metal
center from the norcorrole plane. On the other hand,
a large core in porphyrin with the small radius Ni(II)
distorts the planarity and reduces the N–Ni distance.
Ni–N distance is maximized in the enhanced planarity
of Ni(II) porphyrin. For porphyrins, due to the existence
of four methine groups, the contribution of dom (A2u)-
deformation (Dom is consistent with a bowl shape in this
paper and, considering the citation [16]), is relatively
smaller than others in the symmetric normal-coordinate
deformations: sad (B2u), ruf (B1u), wav (Egx), wav (Egy),
and pro (A1u) [31]. However, the norcorrole macrocycle
desired to gross the orientation, dom-deformation, which
was retained in the X-ray structure of 3, suggesting
the main symmetric deformation. Another substantial
difference of norcorrole from porphyrin is the paratropic
ring current of p-electron density delocalization [14–16].
The distinct magnetism was also hypothesized to
switch the normal behaviors of frequency shifts on the
distortion motion. Entire vibration frequencies of NiNC
in respective solution and solid (single crystals were used
for the spectroscopic study) states, measured with the
first-time radiations in 532 nm, were virtually identical.
An improved planar C2h structure was estimated with
the NiNC monomer in both the initial solution and solid
states, as supported by its crystal structure reported
earlier [13]. Further Raman spectroscopy of the NiNC
samples with correspondingly extended time intervals of
resonance irradiations provided different sequences of
Raman spectra.
Fig. 10. 532 nm excited Resonance Raman spectra of NiNC
monomer in CH2Cl2 solution: (a) 1st time and (b) 2nd time laser
excitations (5 scans with 15 s irradiation interval)
(Figs 9 and 10). As shown in Fig. 9, the oop-mode
frequency appeared around 262 cm-1 (spectrum a)
shifted to 282 cm-1 (spectrum b), performing an
opposite directional shift of typical aromatic porphyrins.
Calculated Raman-active oop-mode frequencies were
obtained at 164 and 169 cm-1 for the planar and bowl-
like structures of NiNC, respectively (Fig. S24 a and b).
Furthermore, ip scissoring vibrations of NiNC, which
associate with the symmetric plane, dividing two dipyrrin
groups, shifted from 434 cm-1 (planar) to 440 cm-1 (bowl-
shaped). There was no significant Raman active frequency
at 200–300 cm-1 obtained from the calculated vibrations.
Two ip rocking vibrations (1481 and 1490 cm-1) of planar
NiNC were calculated to take a closer location (1481 and
1486 cm-1) in bowl-shaped NiNC (Fig. S24, spectra c
and d). The two separated bands appeared to become a
broadened single band as shown in Fig. 10. The similar
aspect was seen around 870 cm-1, in high aggreement
with the calculated vibrations (Fig. S24, spectra e and f).
A single vibration band found at 686 cm-1 was observed
by the first excitation. By the second excitation, an
A CH2Cl2 solution sample of NiNC gave rise to
executed band disappearances and band shifts in
2nd-time excitations using a 532 nm laser pulse
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Meso-1,4-PHENYLENE BRIDGED NICKEL NORCORROLE DIMER
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additional weak vibration band appeared at 650 cm-1
with a vibration band at 692 cm-1. The measured Raman
frequencies were consistent with the calculated Raman
frequencies, supporting the conformation change from
the planar structure to the bowl-shaped structure for
NiNC. The influences appeared to suggest the increase
of Ni–N distances and enhancement of planarity, based
on Raman projection of porphyrin. Dynamic processes
on the double-dipole model of ring current effects have
been investigated to improve the deformation of planarity
of porphyrin plane and p-electron delocalized aromatic
system in nuclear magnetic resonances. Those dynamics
that were deliberated on antiaromatic norcorroles
influenced an opposite chemical shift. It was assured
that the results of Raman motions were reflected with
the paratropic sequence of overall electron-spin vectors.
The degree of flexibility in a solution state enabled the
consequent dynamics. Accordingly, the enhanced ring
distortion resulted in the vibration shifts toward a low
frequency. Still, no subsequent changes of vibration
bands were observed with a crystalline sample of NiNC
(Fig. S14, spectrum d). Two frequencies appeared around
1433 and 1485 cm-1 at spectrum a in Fig. 10 shifted to a
higher frequency region, 1468 and 1565 cm-1 at spectrum
b in Fig. 10, respectively. These results complemented
those presented in the literature [29, 30]. Furthermore, it
was found that the vibrations shown in the spectrum of
NiNC excitation state in a solution corresponded greatly
with the spectral vibrations of dimeric NiNC 3 in a crystal
(spectra b and c in Fig. S15). Crystals of 3 were also
subjected to the Raman spectroscopy with extended time
intervals of resonance irradiation, where no changes were
observed (Fig. S16). Consequently, the solution state of
the NiNC monomer in the excited state was concluded to
adopt a consistent conformation with the crystal structure
of 3, with the distortion of the planarity. Based on the
crystal structure of 3, a bowl-shaped conformation on
each skeleton of NiNC cycles of 3 was then considered
to be a reliable conformation with the monomeric NiNC.
Structurally flexible NiNC molecules in a solution are
forced to take lower symmetric conformations when
photon energies are introduced to the NiNC molecules.
single crystal of the compound 2 were collected at 141 K,
with a Varimax Saturn N instrument and operated using
the Rigaku operation software package. The structure
was solved using direct methods with SHELXS97 and
refined using SHELXL97. All hydrogen atoms were
placed in the calculated positions, respectively.
Computation methods
TD-DFT calculation for the optical property of 3
was set with the B3LYP basis parameters and a CH2Cl2
solvent system. Structure parameters of crystal data,
found in the Crystallographic Information File (CIF),
were initially used for structure optimization with the
symmetric factors. The Gaussian 09 software package
performed DFT calculations with a basis set of B3LYP,
and the existence of a local minimum was verified for
vibration frequency calculation modes. The initial point
group symmetries of the bowl and planar NiNCs were
set to C2v and C2h, respectively, to constrain the structures
for further computations. The wave-shaped structure of
3 was set with the point group of symmetric parameters.
Ci was chosen and carried on the further calculation of
the vibration frequencies. For comparison, vibrational
frequencies were calculated in parallel, without any
operating parameter of the symmetric point-group.
Preparation of compound 3
A Schlenk tube containing 100 mg (61 mmol) of 2b
and 47.63 mg (305 mmol) of 2,2′-bipyridine was moved
into a glove box and 83.9 mg (305 mmol) of Ni(cod)2 was
added into the tube. The resulting solution was stirred
for 1 h at 35°C after the tube was sealed completely. 3
was isolated by the column chromatography on alumina
using a mixed eluent of CH2Cl2 and hexane. A dark
yellow fraction of 3 was separated after a trace amount
of pale yellow fraction, oxacorrole which was generated
by the oxidation of 3. Glossy crystals of 3 were obtained
by a recrystallization from CH2Cl2/MeOH Yield 20 mg
(33%), Spectral data of 3: HRMS (MALDI-TOF): m/z
1
992.1858 (calcd. for [M = C60H42N8Ni2]+ 992.2213) H
NMR (300 MHz; CDCl3: Me4Si; 25°C) TMH, ppm 6.195
(4H, s, mesity-H), 5.119 (4H, s, Ph), 2.848 (12H, s,
mesity-CH3), 1.771 (6H, s, mesity-CH3), 1.362 (4H, d,
J = 4.2, pyrrole-H), 1.263 (4H, d, J = 3.9, pyrrole-H),
1.250 (4H, d, J = 3.9, pyrrole-H), 1.208 (4H, d, J = 4.2,
pyrrole-H); TMC NMR (125.8 MHz; CDCl3; Me4Si;
26.1°C) dC, 148.2, 147.6, 133.2, 130.7, 129.5, 128.1,
127.1, 128.0, 127.8, 127.7, 119.3, 114.63. 25.6, 17.33.
EXPERIMENTAL
General
All the reagents from commercial suppliers were
used without further purification. Chromatographic
separations were carried out by silica gel column
chromatography (Silica gel 300) and gel permeation
chromatography. NMR data of the compounds were
measured with Bruker Avance 300 and 500 MHz NMR
spectrometers in a CDCl3 solvent, with the use of an
internal standard of TMS. The standard Bruker software
was used for homonuclear 1D and homonuclear as well as
heteronuclear 2D experiments. X-ray diffractions of the
CONCLUSION
Nickel norcorrole (NiNC) dimer 3, linked with a
phenylene bridge, was prepared by nickel-mediated
homo-coupling of meso-phenylene bisdipyrrin nickel(II)
dimer 2b. The result of the X-ray diffraction analysis
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J.-Y. SHIN
revealed a uniquely mobilized conformation from the
core planarity of monomeric NiNC. The individual
norcorrole site of the norcorrole dimer 3 showed a bowl-
like (A2u) conformation where the convex and concave
sites were switched between each of the two norcorroles.
As a result, the overall structure (Ci structure) conserved
an letter-S-like conformation. The chemical properties
of dimer 3 were established with optical and vibrational
spectroscopic analysis and assessed with the TD-DFT
calculation data. Enhanced flexibility in solution states of
the monomeric NiNC was highly compromised to solid
states of bowl-shaped NiNC dimer 3. The formulated
conformation is also in good agreement with the DFT
calculation result.
Nevertheless, the crystal structure of the NiNC
monomer took a D2h (Eg) conformation in which high
planarity of the NiNC skeleton was exhibited. It differed
significantly from the excited solution state of the
precursor monomeric NiNC and the crystalline state of
dimeric 3. On the other hand, Raman resonance of the
solution states of NiNC exhibited relatively identical
sequences of the vibration momenta with the norcorrole
dimer 3. Investigation of various extended NiNC systems
and their chemical/magnetic properties are proceeding in
our further norcorrole research.
REFERENCES
1. Shaik S, Shurki A, Danovich D and Hiberty PC.
Chem. Rev. 2001; 101: 1501–1539.
2. Falk JE and Smith KM. In Porphyrins and Metal-
loporphyrins, Elsevier: New York, 1975, pp. 3–28.
3. Keith TA and Bader RFW. Can. J. Chem. 1996; 74:
185–200.
4. Pawlicki M and Latos-Granz˙yn´ski L. Chem. —
Asian J. 2015; 10: 1438–1451.
5. Cissell JA, Vaid TP and Yap GPA. Org. Lett. 2006;
8: 2401–2404.
6. Cho S, Yoon ZS, Kim KS, Yoon MC, Cho DG, Ses-
sler JL and Kim D. J. Phys. Chem. Lett. 2010; 1:
890–900.
7. Valiev RR, Fliegl H and Sundholm D. Phys. Chem.
Chem. Phys. 2017; 19: 25979–25988.
8. Sternberg ED, Dolphin D and Brückner C. Tetrahe-
dron 1998; 54; 4151–4202.
9. Sessler JL, Hemmi G, Mody TD, Murai T, Burrell A
and Young SW. Acc. Chem. Rev. 1994; 27: 43–50.
10. Ghosh A, Wasbotten IH, Davis W and Swarts JC.
Eur. J. Inorg. Chem. 2005; 4479–4485.
11. Conradie J, Foroutan-Nejad C and Ghosh A. Sci.
Rep. 2019; 9: 4852.
12. Bröring M, Köhler S and Kleeberg C. Angew.
Chem. 2008; 120: 5740–5743, Angew. Chem., Int.
Ed. 2008; 47: 5658–5660.
Acknowledgments
13. Ito T, Hayashi Y, Shimizu S, Shin JY, Kobayashi
N and Shinokubo H. Angew. Chem. 2012; 124:
8670–8673; Angew. Chem., Int. Ed. 2012; 51:
8542–8545.
Grant-in-Aid for Scientific Research supported this
research from NEXT (Japan). We also acknowledge
the G30 program foundation of Nagoya University for
the support of this work. J-Y. Shin acknowledges Prof.
Hiroshi Shinokubo at the Department of Molecular
and Macromolecular Chemistry, Graduate School of
Engineering, Nagoya University for his support. Also,
J-Y. Shin thanks Mr. Ryota Ashikaga and Prof. Atsushi
Satsuma at the Department of Materials Chemistry,
Graduate School of Engineering, Nagoya University
Nagoya for Raman spectroscopy.
14. Fukuoka T, Uchida K, Sung YM, Shin JY, Ishida S,
Lim JM, Hiroto S, Furukawa K, Kim D, Iwamoto T
and Shinokubo H. Angew. Chem. 2014; 126: 1532–
1535; Angew. Chem., Int. Ed. 2014; 53: 1506–1509.
15. Nozawa R,Yamamoto K, Shin JY, Hiroto S and Shi-
nokubo H. Angew. Chem. 2015; 127: 8574–8577;
Angew. Chem., Int. Ed. 2015; 54: 8454–8457.
16. Yonezawa T, Shafie SA, Hiroto S and Shinokubo
H. Angew. Chem. 2017; 129: 11984–11987; Angew.
Chem., Int. Ed. 2017; 56: 11822–11825.
17. Shin JY, Yamada T, Yoshikawa H, Awaga K and
Shinokubo H. Angew. Chem. 2014; 126: 3160–3165;
Angew. Chem., Int. Ed. 2014; 53: 3096–3101.
18. Fujii S, Margués-González S, Shin JY, Shinokubo
H, Masuda T, Nishino T, Arasu NP, Vázquez H and
Kiguchi M. Nat. Com. 2017; 8: 15984.
Supporting information
Crystal structures, NMR spectra, HRMS spectra,
cyclic voltammograms, Raman spectra and computa-
tion data (Figs S1–S24 and Table S1) are given in the
supplementary material. This material is available free of
charge via the Internet at http://www.worldscinet.com/
jpp/jpp.shtml. Crystallographic data have been deposited
at the Cambridge Crystallographic Data Centre (CCDC)
under numbers CCDC-1876767 (2b), CCDC-1877278
(2c), CCDC-1877028 (hemi-molecule of 2c) and CCDC
1845468 (3). Copies can be obtained on request, free of
charge, via http://www.ccdc.cam.ac.uk/data_request/cif
or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223-
336-033 or email: deposit@ccdc.cam.ac.uk).
19. Liu B, Li X, Stepien´ M and Chmielewski PJ. Chem.
— Eur. J. 2015; 21: 7790–7797.
20. Nozawa R, Tanaka H, Cha WY, Hong Y, Hisaki I,
Shimizu S, Shin JY, Kowalczyk T, Irle S, Kim D
and Shinoklubo H. Nat. Comm. 2016; 7: 13620.
21. Miao Q, Shin JY, Patrick BO and Dolphin D. Chem.
Commun. 2009; 2541–2543.
22. Brückner C, Karunaratne V, Rettig SJ and Dolphin
D. Can. J. Chem. 1996; 74: 2182–2193.
Copyright © 2019 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2019; 23: 8–9

Meso-1,4-PHENYLENE BRIDGED NICKEL NORCORROLE DIMER
9
23. Brückner C, Zhang Y, Rettig SJ and Dolphin D.
Inorg. Chim. Acta 1997; 263: 279–186.
size = 0.098 × 0.068 × 0.002 mm3, Mo radiation,
orthorhombic, space group Pbca (#61), (#2), a =
9.3075 (1) Å, b = 19.1142 (4) Å, c = 46.6877 (8) Å,
24. Maeda H, Hasegawa M, Hashimoto T, Kakimoto T,
Nishio S and Nakanishi T. J. Am. Chem. Soc. 2006;
128: 10024–10025.
a = b = g = 90°, V = 8306.0 (2) Å3, Z = 8, Pcalcd.
=
1.847 g/cm, R1(F) = 0.0484 (I > 2s(l)), wR2(F2) =
0.1228 (all), GoF = 1.156.
.
25. Crystal data of 2b (CCDC1876767): C60H42N8Br8Ni2
(C6H14) Mr = 1717.88, T = 93 (2) K, Crystal
size = 0.10 × 0.10 × 0.02 mm3, Mo radiation,
triclinic, space group P-1 (#2), a = 7.847 (2) Å,
b = 11.996 (4) Å, c = 19.330 (6) Å, a =
94.573 (7)°, b = 97.154 (7)°, g = 91.271 (5)°,
V = 1798.7 (9) Å3, Z = 1, Pcalcd. = 1.586 g/cm,
R1(F) = 0.0643 (I > 2s(l)), wR2(F2) = 0.1757 (all),
GoF = 1.075.
28. Crystal data of 3 (CCDC 1845468): C60H42N8Ni2,
Mr = 992.43, T = 141 K, Crystal size = 0.074 ×
0.04 × 0.01 mm3, Mo radiation, triclinic, space group
P-1 (#2), a = 9.2609 (11) Å, b = 11.1338 (16) Å,
c = 12.279 (2) Å, a = 86.131 (7)°, b = 76.463 (7)°,
g = 66.489 (5)°, V = 1128.2 (3) Å3, Z = 1, Pcalcd.
=
1.461 g/cm, R1(F) = 0.0717 (I > 2s(l)), wR2(F2) =
0.1717 (all), GoF = 1.067.
29. Schindler J, Kupfer S, Ryan AA, Flanagan KJ,
Senge MO and Dietzek B. Coord. Chem. Rev. 2018;
360: 1–16.
30. Shelnutt JA, Medforth CJ, Berber MD, Barkigia
KM and Smith KM. J. Am. Chem. Soc. 1991; 113:
4077–4087.
31. Shelnutt JA, Song XZ, Ma JG, Jia SL, Jentzen W
and Medforth CJ. Chem. Soc. Rev. 1998; 27: 31–41.
26. Crystal data of 2c (CCDC1877278): C84H54N12Br12Ni3
Mr = 2366.44, T = 93 K, Crystal size = 0.08 × 0.05 ×
0.01 mm3, Mo radiation, triclinic, space group P-1
(#2), a = 13.6554 (4) Å, b = 17.2256 (5) Å, c =
18.9596 (6) Å, a = 88.008 (3)°, b = 72.754 (3)°, g =
79.889 (3)°, V = 4192.4 (2) Å3, Z = 2, Pcalcd. = 1.875
g/cm, R1(F) = 0.0515 (I > 2s(l)), wR2(F2) = 0.1427
(all), GoF = 1.014.
27. Crystaldataofhemi-moleculeof2c(CCDC1877028):
C42H28N6Br6Ni1 Mr = 1154.87, T = 93 K, Crystal
Copyright © 2019 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2019; 23: 9–9