Structural changes in non-planar octaaryl substituted phthalocyanine phosphorus complexes

Article abstract of DOI:10.1142/S1088424615500364

Phosphorus complexes of non-planar α-octaaryl phthalocyanine derivatives ((α-Ar)8Pc), 3a and 3b have been synthesized by introduction of phosphorus(V) ions into free-base Pcs 2a and 2b. 3a and 3b were characterized by MS, 1H and 31P NMR spectra. The solid state structure of 3a indicated a ruffled Pc structure due to the small atomic radius of phosphorus, although the corresponding free-base Pc 2a has a saddled Pc structure. The phosphorus complexes showed intense absorption bands (Q-bands) in the near-IR region, while the introduction of electron-donating groups at the peripheral phenyl groups was efficient for additional red-shifting of the Q-band. Electrochemical data revealed that the red-shift of the Q-band is attributable to a decrease in the HOMO-LUMO gap due to significant and moderate stabilization of the LUMO and HOMO, respectively. MO calculations suggested that the phosphorus(V) ion intensified the electronic interaction between the peripheral aryl moieties and the Pc macrocyclic core.

Full text of DOI:10.1142/S1088424615500364

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2015; 19: 1–10
DOI: 10.1142/S1088424615500364
Published at http://www.worldscinet.com/jpp/
Structural changes in non-planar octaaryl substituted
phthalocyanine phosphorus complexes
Taniyuki Furuyama◊, Ryosuke Harako and Nagao Kobayashi*◊
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
Dedicated to Professor Shunichi Fukuzumi on the occasion of his retirement
Received 28 October 2014
Accepted 7 January 2015
ABSTRACT: Phosphorus complexes of non-planar a-octaaryl phthalocyanine derivatives ((a-Ar)8Pc),
3a and 3b have been synthesized by introduction of phosphorus(V) ions into free-base Pcs 2a and 2b. 3a
1
and 3b were characterized by MS, H and 31P NMR spectra. The solid state structure of 3a indicated a
ruffled Pc structure due to the small atomic radius of phosphorus, although the corresponding free-base
Pc 2a has a saddled Pc structure. The phosphorus complexes showed intense absorption bands (Q-bands)
in the near-IR region, while the introduction of electron-donating groups at the peripheral phenyl groups
was efficient for additional red-shifting of the Q-band. Electrochemical data revealed that the red-shift
of the Q-band is attributable to a decrease in the HOMO–LUMO gap due to significant and moderate
stabilization of the LUMO and HOMO, respectively. MO calculations suggested that the phosphorus(V)
ion intensified the electronic interaction between the peripheral aryl moieties and the Pc macrocyclic core.
KEYWORDS: phosphorus phthalocyanine, ruffled structure, electronic structure, near-infrared
absorption.
peripheral substituents, and the macrocyclic core appears
INTRODUCTION
critical, in order to obtain novel absorption properties.
Phthalocyanines (Pcs) are some of the most well-
A rigid planar structure for the macrocycle is also a
known and successful artificial dyes and pigments in
feature of Pcs. However, we [4], Cook [5], and McKeown
modern materials chemistry. Pcs have a symmetrical 18p
electron aromatic macrocycle, and an intense absorption
band (the so-called Q-band) appears in the visible
[6] reported “non-planar Pcs” with bulky peripheral
substituents at the so-called a positions of Pcs. X-ray
crystallography revealed that this type of derivative has a
(650–700 nm) region. The optical properties of Pcs often
highly-saddled conformation due to the steric hindrance
correlate with their function in practical applications, so
of the peripheral substituents. These Pcs also retain
that changing the absorption properties of Pcs is one of
the most attractive research topics in their chemistry
18p aromaticity, namely curved p-conjugation [7], and
an intense Q absorption band still appears. In the case
[1]. Recently, we reported that the introduction of
of octraaryl-substituted non-planar Pcs, these show a
phosphorus(V) ions into appropriate Pcs can shift their
significantly red-shifted Q-band (at around 800 nm) [4a],
Q-band beyond 1000 nm [2]. Interestingly, the effect of
while the Q-bands of octaalkyl-substituted non-planar Pcs
the phosphorus atom is completely different between
appear at a similar wavelength to typical Pcs (at around
Pcs and tetraazaporphyrins (TAPs) [3], the congeners of
700 nm) [5]. On the other hand, Kojima and Fukuzumi
Pc. Hence, the combination of a central phosphorus ion,
demonstrated that the saddled structure of Pcs could
assemblewithprotonatedporphyrins, andthattheresulting
complex undergoes photoinduced intrasupramolecular
◊ SPP full member in good standing
electron transfer [8]. Moreover, unique effects dependent
on phenyl substitution [9] and the central element [10]
*Correspondence to: Nagao Kobayashi, email: nagaok@m.
tohoku.ac.jp, tel/fax +81 22-795-7719
Copyright © 2015 World Scientific Publishing Company

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T. FURUYAMA ET AL.
of octaphenyl-substituted non-planar Pcs have also
been reported by our group. Although the effect of aryl
groups is still not completely clear, the modified octaaryl-
substituted non-planar Pcs may be attractive targets in
materials chemistry. In this paper, we report the synthesis
and properties of phosphorus(V) complexes of non-
planar a-octaaryl phthalocyanine derivatives (a-Ar)8Pc).
The crystallographic structures of Pc [2] and TAP [3a]
phosphorus complexes show ruffled configurations due
to the small atomic radius of the phosphorus. Peripheral
substitution effects in the phosphorus complexes are also
significant, where the absorption envelope of phosphorus
TAP was proven to be changed markedly by changing the
peripheral moieties, since the aryl substituents are directly
linked to the TAP core. Hence, phosphorus(V) complexes
of arylated non-planer Pc ((a-Ar)8PcP(V)) appear to
be attractive subjects for examining their structural and
spectroscopic properties.
diffractometer with Bruker Helios multilayered confocal
mirrormonochromatizedMoKaradiation(l=0.71073Å)
at -173°C. The structures were solved by a direct method
(SIR2004) [11] and refined using a full-matrix least
squares technique (SHELXL-97) [12]. Yadokari-XG
2009 software was used as a GUI for SHELXL-97 [13].
All non-hydrogen atoms were refined anisotropically.
The positions of all hydrogen atoms were calculated
geometrically, and refined by applying riding models.
Some large electron peaks due to solvent molecule(s)
were found in the unit cell. As we failed to model these
properly, the rest of the molecules were refined without
the effect of the solvent molecules by the Platon squeeze
technique [14].
Synthesis
Free-base phthalocyanines 2a [4] and 2b [9] were
prepared according to the literature.
Preparation of (a-Ph)8Pc phosphorus(V) complex
(3a). POBr3 (150 mg, excess) was added to a solution of
2a (30 mg, 26.7 mmol) in 2 mL of pyridine and stirred for
1 h at room temperature. After removing the solvent in
vacuo, the residue was dissolved in a solution of CH2Cl2/
MeOH (2/1 v/v) and stirred for 1 h at room temperature.
The organic layer was collected, washed with water,
and the solvent removed, to yield a dark red product
(phosphorus(V) Pc). The resulting solid was dissolved in
CH3CN/CH2Cl2 (1/1 v/v), then KPF6 (25 mg, 140 mmol)
added. After stirring the mixture for 3 h at room
temperature, the solvent was removed, and the residue
recrystallized from CH2Cl2/n-hexane. The title compound
EXPERIMENTAL
Measurements
Electronic absorption spectra were recorded on a
JASCO V-570 spectrophotometer. Magnetic circular
dichroism (MCD) spectra were obtained on a JASCO J-725
spectrodichrometer equipped with a JASCO electromagnet
capable of producing magnetic fields of up to 1.03 T (1 T =
1 tesla) with both parallel and antiparallel fields. The
magnitudes were expressed in terms of molar ellipticity
per tesla ([q]M, deg.M-1.cm-1.T ). NMR spectra were
-1
1
was obtained (20 mg, 55%) as a red powder. H NMR
obtained on a Bruker AVANCE III 500 spectrometer using
CDCl3 as solvent unless otherwise noted. Chemical shifts
and coupling constants are expressed in d(ppm) values
(500 MHz, CDCl3): d, ppm 7.89 (s, 8H), 7.37–7.33 (m,
24H), 7.28–7.26 (m, 16H), 0.01 (d, 6H, 3JPH = 28.5 Hz).
31P NMR (200 MHz, CDCl3): d, ppm -144 (septet, PF6,
J = 700 Hz), -173 (s, P(OMe)2). HRMS-MALDI: m/z
calcd. for C82H54N8O2P [M – PF6]+ 1213.4102. Found
1213.4101. Anal. calcd. for C82H54F6N8O2P2: C, 72.46; H,
4.00; N, 8.24. Found C, 72.40; H, 4.37; N, 7.98. UV-vis
(CH2Cl2): lmax, nm (10-5 e) 852 (1.10).
Preparation of (a-4-OMe-Ph)8Pc phosphorus(V)
complex (3b). The procedure described for 3a was used
with 2b, to give the title compound as a gray powder
(72%). 1H NMR (500 MHz, CDCl3): d, ppm 7.87 (s, 8H),
7.41 (d, 16H, J = 8.5 Hz), 6.79 (d, 16H, J = 8.5 Hz), 3.97
(s, 24H), 0.16 (d, 6H, 3JPH = 28.5 Hz). 31P NMR (200 MHz,
CDCl3): d, ppm -144 (septet, PF6, J = 700 Hz),
-172 (s, P(OMe)2). HRMS-MALDI: m/z calcd. for
C90H70N8O10P [M – PF6]+ 1453.4947. Found 1453.4948.
UV-vis(CH2Cl2): lmax, nm (10-5 e) 916 (1.01).
1
and in hertz (Hz), respectively. H NMR spectra were
referenced to the residual solvent as an internal standard.
31P NMR spectra were referenced to external 85% H3PO4
solution (0.0 ppm). The following abbreviations are used:
s = singlet, d = doublet, and m = multiplet. High-resolution
mass spectra (HRMS) were recorded on a Bruker
Daltonics Apex-III spectrometer. CV measurements were
recorded with a Hokuto Denko HZ5000 potentiostat under
a nitrogen atmosphere in o-dichlorobenzene (o-DCB)
with 0.1 M of tetrabutylammonium perchlorate (TBAP)
as a supporting electrolyte. Measurements were made
with a glassy carbon electrode (area = 0.07 cm2), an Ag/
AgCl reference electrode, and a Pt wire counter electrode.
The concentration of the solution was fixed at 1.0 mM and
the sweep rates were set to 100 mV/s. The ferrocenium/
ferrocene (Fc+/Fc) couple was used as an internal standard.
Computational details
Crystallographic data collection
Geometry optimization for all molecules was
performed at the DFT level, by means of the hybrid
Becke3LYP[15] (B3LYP) functional, as implemented
in Gaussian 2009 [16]. The 6-31G* basis set was used
A red, plate shaped single crystal of 3a 0.20 × 0.10 ×
0.05 mm, was selected for measurement. The diffraction
data were collected using a Bruker APEXII CCD
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STRUCTURAL CHANGES IN NON-PLANAR OCTAARYL SUBSTITUTED PHTHALOCYANINE PHOSPHORUS COMPLEXES
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for all atoms. After the geometry optimization, time-
dependent (TD) DFT calculations [17] were performed
to evaluate the stick absorption spectrum employing
BLYP functionals with long-range correction (LC) [18]
(LC-BLYP) using the same basis set.All stationary points
were optimized without any symmetry assumptions, and
characterized by normal coordinate analysis at the same
level of the theory (number of imaginary frequency,
Nimag, 0).
structure in solution. The 31P NMR spectra exhibit
only one peak at -173 ppm for 3a and -172 ppm for 3b,
supporting hexa-coordinated phosphorus representations
[19] lying within the central cavity of the Pc macrocycle.
Solid-state structure
The structure of 3a was unambiguously elucidated by
X-ray diffraction analysis of crystals obtained from the
diffusion of n-pentane into a CH2Cl2 solution of 3a. The
X-ray crystallographic structure of 3a is shown in Fig. 2.
Figure3showsthedisplacementofthe24coreatomsfrom
the 4N mean plane of 2a (crystallographic data was taken
from Ref. 4b) and 3b. The degree of distortion of the core
(Dr), which was calculated as the square root of the sum
of square of the deviation of each atom from the mean
plane, rationalizes the nonplanarity of the Pcs. Although
the Dr value of 3a (0.57) is close to that of 2a (0.58), the
type of distortion is different. 3a has a ruffled structure
rather than the typical saddled structure reported for
non-planar Pcs. The distances between the two pyrrole-
nitrogen atoms at opposite sides in the core (3.675(4) and
3.685(4) Å) for 3a are shorter than those of 2a (3.804(5)
and 3.983(4) Å) and reported metallo and free-base Pcs
(3.8–4.0 Å) [2a]. The small macrocyclic Pc core of 3a
originates from the small atomic radius (106 pm) of the
phosphorus(V) atom, resulting in a bond length of 1.84 Å
between phosphorus and nitrogen in the core of 3a,
which is reasonable for a single bond of hexacoordinated
phosphorus(V)–nitrogen [20]. Therefore, the structural
influence of only one phosphorus(V) atom is stronger
than the bulky phenyl substituents at the peripheral
position.
RESULTS AND DISCUSSION
Synthesis
The synthetic procedures for the phosphorus(V)
complexes are shown in Scheme 1. Free-base Pcs 2a
and 2b were first prepared according to the literature
procedures in moderate yields. For the introduction of
a phosphorus ion into the macrocyclic core, phosphorus
oxybromide was used, as previously reported. Finally,
the desired complexes 3a (a-octa(phenyl)) and 3b
(a-octa(p-methoxyphenyl)) were isolated as the hexa-
fluorophosphate salts. The color of 3a and 3b is red and
gray, respectively, rather than the typical blue-green color
of Pc. 3a and 3b showed excellent solubility in general
organic solvents, and could be fully characterized by
NMR and HR-MALDI-FT-ICR mass spectroscopy. The
observed MS spectrum of 3a and calculated isotropic
distributions are shown in Fig. 1. The strongest peak was
found at m/z = 1213.4101, and the isotropic distribution
patterns provided a reasonable match with experiment for
the compound whose molecular formula is C82H54N8O2P
as a cationic part of 3a ([M – PF6]+). The 1H NMR spectra
show only one kind of peripheral aryl group, at the
b-position of the Pc macrocycle, and a doublet assignable
to axial methoxy groups at high field (ca. 0 ppm); hence
the conformation of the phosphorus(V) complexes
appears to retain a highly symmetrical, unaggregated
Electronic absorption and MCD spectroscopy
The absorption and MCD spectra of the Pcs in
CH2Cl2 are shown in Fig. 4. The absorption spectra
of all compounds show intense Q-bands in the near-IR
+
R
R
R
R
R
MeO
N
N
N
NH
N
N
N
N
P
CN
CN
(i)
(ii), (iii)
R
R
R
R
R
R
R
R
–
N
N
N
PF6
N
HN
N
N
N
OMe
R
1a (R = H)
1b (R = OMe)
2a 23%
2b 19%
3a 55%
3b 72%
R
R
R
R
Scheme 1. Synthesis of octaaryl substituted phthalocyanine phosphorus(V) complexes. Reagents and conditions: (i) nBuOLi (4 eq),
nBuOH, reflux, 1 h; (ii) POBr3 (20 eq), pyridine, rt, 1 h, then MeOH, rt, 1 h; (iii) KPF6, CH3CN/CH2Cl2, rt, 3 h
Copyright © 2015 World Scientific Publishing Company
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T. FURUYAMA ET AL.
Fig. 1. Observed high-resolution mass spectrum (a) of 3a and the theoretical distribution pattern for C82H54N8O2P ([M – PF6]+) (b)
Fig. 2. X-ray crystal structure of 3a. The thermal ellipsoids were scaled to the 50% probability level. (a) top view; (b) side view.
H atoms, and solvent molecules have been omitted for clarity
region. The Q-bands of free-base Pc 2a and 2b might
be split theoretically into four peaks, but they show
only two peaks or shoulders (Q00 and Q01 bands). In
the MCD spectra of 2a and 2b, dispersion-type signals
were observed corresponding to their Q00 bands. It is
considered that the splitting of the Q-band is so small that
the superimposition of two oppositely signed Faraday
B terms give seemingly A term-like MCD signals, the
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STRUCTURAL CHANGES IN NON-PLANAR OCTAARYL SUBSTITUTED PHTHALOCYANINE PHOSPHORUS COMPLEXES
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Fig. 3. Views of the skeletal deviation of the atoms from the 4N mean plane for (a) 2a (crystallographic data was taken from Ref. 4b)
and (b) 3a. The black circles indicate carbon atoms. The black squares and gray triangles indicate nitrogen atoms at the meso-
position and coordinating nitrogen atoms, respectively
so-called pseudo Faraday A term. As we previously
reported [4, 9], the introduction of eight aryl groups at
the a positions can shift the Q-band to the near-IR region;
in particular, 2b has a sharp Q-band in the region beyond
800 nm. The insertion of a phosphorus(V) ion into 2a
produces a red-shift of ca. 70 nm (ca. 990 cm-1), while
the difference between the free-base a-(ArS)8Pc and its
phosphorus(V) complex is ca. 210 nm (ca. 2500 cm-1)
[2]. The extent of the red-shift upon phosphorus insertion
into the core of the Pc was different from substituent
to substituent, so that octaaryl substitution at the a
position is not efficient for further red-shifting beyond
1000 nm by the phosphorus(V) ion, which is different
from the case of a-octathioaryl group substituted Pc [2].
In contrast, the substitution effect at the aryl group is
enhanced by phosphorus insertion. The difference in
Q-band position between methoxy substituted 3a and
3b (64 nm, ca. 820 cm-1) is significantly larger than that
between unsubstituted 2a and 2b (25 nm, ca. 390 cm-1).
The Q-band of 3b appears at 916 nm, which is sufficiently
long enough for application in the near-IR photodynamic
therapy of cancer [21]. Since Pcs having a Q-band at
around 900 nm are still rare, the combination of a central
phosphorus atom and appropriate aryl groups at the a
position appears to be an efficient method for accessing
near-IR light at around 900 nm. The Faraday A MCD term
of 3a and 3b in the Q-band region further indicates that the
practical chromophore symmetry of these complexes is
close to D4h, similarly to typical metallo Pcs.A broad, weak
absorption band appeared between the Soret and Q-bands
(at around 500 nm) for the phosphorus complexes. The
MCD spectra corresponding to these absorptions cannot
be interpreted simply, since their complex character
suggests an overlap of several transitions. Although
the detailed assignment will be discussed later, these
bands could be assigned to a charge-transfer (CT) band
from peripheral aryl groups to the macrocyclic Pc core.
Emission of phosphorus(V) complexes are very weak (FF
< 0.01), so that the fluorescence spectra of both 3a and 3b
could not be obtained.
Electrochemistry
It is well-established that the HOMO and LUMO
energies of Pc derivatives correlate well with their first
oxidation and reduction potentials [22]. Estimating the
values of the redox potentials is also important in order
to determine the origins of the effect of phosphorus
insertion. Fig 5 displays cyclic voltammograms of the
Pcs in o-dichlorobenzene (DCB) with 0.1 M nBu4NClO4
as the supporting electrolyte. The gap between the first
redox potentials (E1ox – E1red) correlate well with the
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T. FURUYAMA ET AL.
Fig. 4. UV-vis-NIR absorption (bottom) and MCD (top) spectra of Pcs in CH2Cl2. (a): 2a (gray dashed line) and 3a (black solid line).
(b): 2b (gray dashed line) and 3b (black solid line)
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STRUCTURAL CHANGES IN NON-PLANAR OCTAARYL SUBSTITUTED PHTHALOCYANINE PHOSPHORUS COMPLEXES
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Fig. 5. Cyclic voltammetry data for (a) 2a and 3a, and (b) 2b and 3b. Cyclic voltammograms were acquired from 1.0 mM solutions
of analyte in 0.1 M nBu4NClO4/o-DCB. Ferrocene was used as an internal standard and set to 0 V
Fig. 6. Partial molecular energy diagram and orbitals of 2a and cationic part of 3a (top) and their calculated absorption spectra
(bottom). Calculations were performed at the LC-BLYP/6-31G*//B3LYP/6-31G* level
positions of the Q-bands. Both of the redox potentials of
2b are shifted cathodically from those of 2a, so that it
is concluded that the electron donating group (OMe) on
the exterior of the p-conjugated system of the Pc ligand
can affect the electronic structure of a-octaarylated Pc.
After the introduction of a phosphorus(V) ion into the
Pc, both the redox potentials are shifted anodically. For
2a and 3a, the first reduction potential, which is related
to the LUMO level, shifted from -1.35 V to -0.59 V,
while the first oxidation potential, which is related to
the HOMO level, shifted from -0.02 to 0.66 V. These
potentials indicate that the stabilization of the LUMO
is larger than that of the HOMO after the phosphorus
introduction. Similar changes in redox potentials were
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T. FURUYAMA ET AL.
Table 1. Calculated excited wavelength (l) and oscillator strengths (f) for components of
selected transition energies
Compound
l, nm
f
Composition, %a
2a
838.0
798.4
343.8
332.3
312.4
0.43
0.49
0.20
0.46
0.18
288→294 (7%), 293→295 (92%)
288→295 (4%), 293→294 (94%)
290→295 (11%), 292→294 (11%), 293→297 (66%)
284→294 (12%), 288→294 (58%), 293→295 (6%)
284→295 (3%), 288→295 (31%), 291→294 (31%)
292→297 (3%), 293→298 (10%)
3a+
917.8
904.0
370.0
349.2
0.42
0.41
0.19
0.07
299→318 (3%), 316→317 (91%), 316→318 (4%)
299→317 (3%), 316→317 (4%), 316→318 (91%)
313→318 (29%), 314→317 (33%), 316→320 (21%)
313→317 (10%), 313→318 (22%), 313→320 (2%)
314→317 (13%), 314→318 (4%), 315→317 (26%)
313→317 (6%), 313→318 (18%), 314→317 (17%)
314→320 (2%), 315→317 (26%), 315→318 (6%)
313→317 (4%), 314→317 (8%), 315→317 (9%)
315→318 (51%), 315→320 (3%), 316→319 (4%)
346.8
345.8
0.07
0.06
observed on going from 2b to 3b. In particular, the
cathodic shift (0.22 V) of the first oxidation potential
on going from phosphorus-containing 3a (0.66 V) to 3b
(0.44 V) is larger than that observed (0.08 V) on going
from free-base 2a (-0.02 V) to 2b (-0.10 V), supporting
the conclusion that the substitution effect is enhanced by
the phosphorus introduction.
orbitals in Gouterman’s model [23], respectively. The
central phosphorus(V) ion significantly stabilizes both
the HOMO and LUMO, with a higher extent for the
LUMO, as expected from the CVs of 2a and 3a (Fig. 5).
The calculated bands (370, 349, 347 and 346 nm) of
3a+ are composed of transitions from the HOMO-1,
HOMO-2 and HOMO-3 to the nearly-degenerate
LUMOs. The HOMO-1 to HOMO-3 transitions are
localized on the peripheral phenyl rings, so that these
bands can be assigned to CT transitions. The complicated
transitions in the calculated spectrum indicate quite
complicated MCD signals of 3a at around 500 nm. We
also calculated the absorption spectrum and molecular
orbitals of [b-Ph8PcP(OMe)2]+ [3a], which is a positional
isomer of [a-Ph8PcP(OMe)2]+ having phenyl groups
at eight b-positions, however, the positions of these
transitions were estimated to lie in a shorter wavelength
region (356–336 nm) than those of 3a+, supporting the
conclusion that the substitution effect of a-arylated Pc
(3a vs. 3b) is larger than b-arylated Pc.
Molecular orbital calculations
In order to enhance the interpretation of the electronic
structures of (a-Ar)8PcP(V), MO calculations of free-
base Pc 2a and the cationic part of the phosphorus
complex 3a (3a+) have been performed. The molecular
geometries were first optimized at the DFT level using
B3LYP/6-31G(d). Since a CT interaction between
peripheral aryl groups and the Pc macrocyclic core can
be expected from the observed absorption spectrum of
3a, we applied the LC-BLYP [3, 18]/6-31G(d) level to the
calculations for the molecular orbitals and excited states
of 2a and 3a+. Partial MO energy diagrams showing the
calculated absorption spectra are shown in Fig. 6, with
the calculated transition energies, oscillator strengths (f),
and configurations summarized in Table 1. The lowest-
energy bands (the Q-bands) of 2a are calculated to lie at
838 and 798 nm, while those of 3a+ are calculated to lie at
918 and 904 nm, supporting the experimental absorption
spectra. These bands are composed mainly of HOMO →
LUMO or HOMO → LUMO+1 transitions (ca. 90%),
and the HOMO, LUMO, and LUMO+1 orbitals included
in the transitions correspond to the a1u-, egy-, and egx-like
CONCLUSION
Non-planar a-octaaryl phthalocyanine phosphorus(V)
complexes have been prepared in order to estimate
the effect of peripheral substituents and a central
phosphorus(V)ion.Thenon-planarstructureofa-octaaryl
free-base Pcs does not prevent the introduction of the
phosphorus ion into the core of the Pc. The synthesized
phosphorus(V) Pcs can be fully characterized by MS
and NMR spectra; moreover, the X-ray crystallographic
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STRUCTURAL CHANGES IN NON-PLANAR OCTAARYL SUBSTITUTED PHTHALOCYANINE PHOSPHORUS COMPLEXES
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structure of 3a could be obtained. The crystal of 3a has
a distorted, ruffled structure, while that of non-metalated
2a adopts a saddled structure, supporting the premise that
the small atomic radius of the phosphorus ion can switch
the structure of the macrocyclic core, even in Pcs with
bulky substituents. The Q-bands of the phosphorus(V)
complexes show a significant red shift from those of
free-base Pcs. The introduction of an electron-donating
methoxy group into the peripheral aryl groups at eight
a-positions is quite efficient for shifting the Q-band, so
that the Q-band of 3b appeared beyond 900 nm. Cyclic
voltammograms of the Pcs also support the red-shifted
Q-bands and the substitution effect of phosphorus(V)
Pcs, while MO calculations can explain the experimental
results. Thus, the combination of a-octaaryl Pcs and a
central phosphorus ion can manipulate both the near-IR
absorption properties and the solid-state structures,
indicating that this strategy can be applied for developing
novel near-IR absorbing functional dyes and pigments.
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This work was partly supported by Grant-in-Aids
for Scientific Research on Innovative Areas (25109502,
“Stimuli-responsive Chemical Species”), Scientific
Research (B) (No. 23350095), Challenging Exploratory
Research (No. 25620019) and Young Scientist (B) (No.
24750031) from the Ministry of Education, Culture,
Sports, Science, and Technology (MEXT). The authors
thank Prof. Takeaki Iwamoto and Dr. Shintaro Ishida
(Tohoku University) for X-ray measurements. Some of
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Supporting information
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Cambridge Crystallographic Data Centre (CCDC) under
number CCDC-1030507. Copies can be obtained on
request, free of charge, via 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: data_request@ccdc.cam.
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