Molecular structures of Cu(II), Rh(III) complexes of 2-N substituted N-confused porphyrin inner C-oxide

Article abstract of DOI:10.1016/j.poly.2012.05.018

The crystal structures of a paramagnetic copper(II) complex 2-aza-2-(3′-phenoxypropyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N, N′,N″-O) copper(II) [Cu(2-NCH₂CH₂CH ₂-O-C₆H₅NCTPPO; 7)] and a diamagnetic rhodium(III) complex chloro (2-aza-2-benzyl-5,10,15,20-tetraphenyl-21- carbaporphyrinato-N,N′,N″-O) rhodium(III) [Rh(2-N-CH ₂C₆H₅NCTPPO)Cl; 8] have been established. The coordination sphere around the Cu²⁺ ion in 7 is distorted square planar, whereas for Rh³⁺ in 8, it is a distorted octahedron. A copper(II) complex 7 has been isolated and characterized by electron spin resonance spectroscopy with a structure incorporating an Cu-O-C unit. The Rh-O 2.043(2) ? and Rh-C(17) 2.170(3) ? distances in 8 suggests a direct interaction between the rhodium center and the π electron density on the carbonyl group in a η² fashion.

Full text of DOI:10.1016/j.poly.2012.05.018

Polyhedron 42 (2012) 243–248
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Molecular structures of Cu(II), Rh(III) complexes of 2-N substituted N-confused
porphyrin inner C-oxide
b
c
Wen-Chain Lin a, De-Zhi Hsaio a, Wen-Pin Chang a, Jyh-Horung Chen a, , Shin-Shin Wang , Jo-Yu Tung
⇑
a Department of Chemistry, National Chung Hsing University, Taichung 40227, Taiwan
b Material and Chemical Research Laboratories, ITRI, Hsin-Chu 300, Taiwan
c Department of Occupational Safety and Health, Chung Hwai University of Medical Technology, Tainan 717, Taiwan
a r t i c l e i n f o
a b s t r a c t
The crystal structures of a paramagnetic copper(II) complex 2-aza-2-(30-phenoxypropyl-5,10,15,20-tetra-
phenyl-21-carbaporphyrinato-N,N0,N00-O) copper(II) [Cu(2-NCH2CH2CH2-O-C6H5NCTPPO; 7)] and
diamagnetic rhodium(III) complex chloro (2-aza-2-benzyl-5,10,15,20-tetraphenyl-21-carbaporphyrina-
to-N,N0,N00-O) rhodium(III) [Rh(2-N-CH2C6H5NCTPPO)Cl; 8] have been established. The coordination
sphere around the Cu2+ ion in 7 is distorted square planar, whereas for Rh3+ in 8, it is a distorted octahe-
dron. A copper(II) complex 7 has been isolated and characterized by electron spin resonance spectroscopy
with a structure incorporating an Cu–O–C unit. The Rh–O 2.043(2) Å and Rh–C(17) 2.170(3) Å distances
Article history:
Received 16 April 2012
Accepted 17 May 2012
Available online 26 May 2012
a
Keywords:
X-ray diffraction
Rhodium(III) N-confused porphyrin
Copper(II) N-confused porphyrin
N-confused porphyrin inner C-oxide
Electron spin resonance
in 8 suggests a direct interaction between the rhodium center and the
p electron density on the carbonyl
group in a g2 fashion.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
oxygenated Co(CTPPO)(NO) (4) from the reaction of Co(HCTPP)
with nitric oxide in CH2Cl2 [7].
An N-confused porphyrin NCP is a porphyrin isomer with an in-
verted pyrrole ring. There are three main reaction sites in the con-
fused pyrrole ring, i.e., 2-N, 21-C and 3-C [1]. At the external
nitrogen of NCP (2-N), an electrophilic reaction can take place result-
ing in the formation of alkylated products [1,2]. Ziegler and cowor-
ker reported the synthesis of the 2-N-allyl-5,10,15,20-tetraphenyl
N-confused porphyrin 2-NC3H5NCTPPH [3]. Here in this study, the
allyl group of 2-NC3H5NCTPPH is modified to a bulky 30-phenoxy-
propyl [or benzyl (Bz)] group to derive the free base 2-aza-2-(30-
phenoxypropyl)-5,10,15,20-tetraphenyl N-confused porphyrin,
2-NCH2CH2CH2-O-C6H5NCTPPH (1) [or 2-N-benzyl-5,10,15,20-tet-
raphenyl N-confused porphyrin, 2-NCH2C6H5NCTPPH (2)] [4,5].
Unlike the NH tautomerism that exists in NCTPPH2, the free base 1
(or 2) has only one stable form. The N-confused porphyrin 1 (or 2)
can provide N3 or N3C coordinated sites.
Rachlewicz reported that an insertion of oxygen atom into the
performed FeIII–C(21) bond in FeIII(HCTPP)Br produced a paramag-
netic complex, [FeIII(CTPPO)Br]ꢀ (5) [8]. The species 5 can be con-
verted into the high-spin derivative FeIII(HCTPPO) Br (6) after
addition of the acid (TFA) [8]. All the reported C-oxide complexes
3, 4, and 6 are M(III) paramagnetic species. The shortfall in the study
on M(III) diamagnetic complex of an N-confused porphyrin inner
C-oxide prompted us to undertake the synthesis and structural
characterization on metallation of 2, leading to the new diamagnetic
rhodium(III) complex chloro (2-aza-2-benzyl-5,10,15,20-tetraphe-
nyl-21-carbaporphyrinato-N,N0,N00-O) rhodium(III) [Rh(2-N-CH2
C6H5NCTPPO)Cl; 8] (Scheme 1). In order to investigate the range of
metal ions that can be inserted into 1, the structure and spectro-
scopic properties of a paramagnetic copper(II) complex 2-aza-
2-(30-phenoxypropyl-5,10,15,20-tetraphenyl-21-carbaporphyrina-
to-N,N0,N00-O) copper(II) [Cu(2-NCH2CH2CH2-O-C6H5NCTPPO; 7)]
formed by insertion of Cu(II) ion into 1 (Scheme 1) was initially de-
scribed. The bulky benzyl group in 2 and a flexible (or loosely-ar-
ranged) 3-phenoxypropyl group in 1 of this system enhance the
crystallization of complexes 7 and 8. In this paper, we report the
results of the X-ray structural investigation of the metallation of 2
(or 1) leading to a novel rhodium complex 8 (or a new copper com-
plex 7). In particular rhodium(III), was chosen for this study because
it was likely to give a diamagnetic product which would be easily
characterized by 1H NMR spectroscopy.
When an oxygen atom is inserted into the M–C bond in a metal
N-confused porphyrin complex, it becomes the metal complex of
an N-confused porphyrin inner C-oxide. This kind of N-confused
prophyrin C-oxide metal complex is quite rare. Dolphin reported
a paramagnetic Ni(III) complex of a N-confused porphyrin inner
C-oxide Ni(CTPPO)(pyridine) (3) [6]. Hung reported a paramagnetic
⇑
Corresponding author. Tel.: +886 4 228 40411x612; fax: +886 4 228 62547.
E-mail address: JyhHChen@dragon.nchu.edu.tw (J.-H. Chen).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.05.018

244
W.-C. Lin et al. / Polyhedron 42 (2012) 243–248
Ph
Ph
N
R
Cu(OAc)2
N
N
Cu
18
19
17
16
O
CH3CN/CH2Cl2, reflux 12 h
Ph
Ph
20
N
15
14
N
24
R
1
4
2
Ph
Ph
13
12
N
21
NH
23
H
(7)
R1 =CH2CH2CH2-OC6H5
3
11
22
60.5 %
N
5
10
Ph
9
6
Ph
Ph
Ph
8
7
N
R
R =CH2CH2CH2-OC6H5 = R1 (1)
R = CH2C6H5 = R2 (2)
Cl
[Rh(CO)2Cl]2
N
N
Rh
O
CH3CN/CH2Cl2, reflux 12 h
N
Ph
Ph
(8)
R2 = CH2C6H5
R1 =
R2 =
CH2CH2CH2-O
26.9 %
H
C
H
Scheme 1.
Table 1
Crystal data for 1, 7 and 8.
Compound
1
7
8
Formula
C
53H40N4O
C53H38CuN4O2
826.41
P21/c
monoclinic
17.0625(5)
17.1599(4)
13.8711(3)
90
98.613(2)
90
4015.5(2)
4
C51H34ClN4ORh
857.18
P1
Formula weight
Space group
Crystal system
a (Å)
b (Å)
c (Å)
748.89
P1
ꢀ
ꢀ
triclinic
10.3822(3)
13.8621(4)
14.2609(5)
105.414(3)
95.339(3)
102.612(2)
1905.8(1)
2
triclinic
12.1950(4)
13.5012(6)
13.6656(6)
69.970(4)
70.508(4)
82.786(3)
1966.2(1)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
F(000)
788
1.305
0.078
1716
1.367
0.593
876
1.448
0.548
Dcalc (g cmꢀ3
)
l(Mo K
a
) (mmꢀ1
)
S
0.982
1.013
1.038
Crystal size (mm)
h (°)
T (K)
0.46 ꢁ 0.40 ꢁ 0.28
2.87–29.25
110(2)
0.42 ꢁ 0.36 ꢁ 0.32
2.89–29.17
110(2)
0.72 ꢁ 0.62 ꢁ 0.36
2.93–29.30
110(2)
Number of reflections measured
Number of reflections observed
8744
5928
0.0441
0.1056
9339
5632
0.0634
0.1321
9031
6995
0.0504
0.1315
a
R1
b
wR2
P
P
a
R1 = [ ||Fo| ꢀ |Fc||/ |Fo|].
P
P
2
2 1=2
wR2 ¼ ½ wðF2o ꢀ Fc2Þ = wðF2oÞ ꢂ
.
b
by column chromatographic with EtOAc/CH2Cl2 [1:9 (v/v)] as the
eluent and collected a light green band on silica gel (230–400 mesh,
25 g). Further recrystallization from CH2Cl2/hexane [2:2 (v/v)] affor-
ded 1 (0.13 g, 0.17 mmol, 35.4%) as a purple solid. Compound 1 was
redissolved in CH2Cl2 and layered with hexane to afford purple crys-
tals for single-crystal X-ray analysis. 1H NMR (599.94 MHz, CDCl3,
20 °C) d: 7.99 [m, 2H, Hb(2, 3), 3J(H–H) = 3.2 Hz]; 7.82 [t, 2H,
o-H(40, 44) of phenyl group, 3J(H–H) = 3.6 Hz]; 7.64 [m, 2H,
2. Experimental
2.1. Preparation of 1
A solution of NCTPPH2 (0.30 g, 0.49 mmol) and 3-phenoxypropyl
bromide (2 ml, 12.6 mmol) in dry p-xylene (10 ml) in the presence of
Cs2CO3 (0.45 g, 1.56 mmol) was heated at 110 °C for 2 h. After cool-
ing downto roomtemperature, the mixturewas filteredand purified

W.-C. Lin et al. / Polyhedron 42 (2012) 243–248
245
Table 2
Compound 7 was dissolved in CH2Cl2 and layered with EtOAc
[CH2Cl2/EtOAc = 2:2 (v/v)] to afford pure crystals of 7 (0.020 g,
0.024 mmol, 60.5%) for single-crystal X-ray analysis. Anal. Calc.
for C51H38CuN4O2: C, 77.03; H, 4.63; N, 6.76. Found: C, 76.88; H,
4.66; N, 6.99%. MS(ESI), m/z (assignment, rel. intensity): 826.4
Selected bond distances (Å) and angles (°) for compounds 7 and 8.
7
Bond lengths (Å)
Cu–O(1)
Cu–N(1)Cuꢃ ꢃ ꢃC(17)
Bond angles (°)
O(1)–Cu–N(1)
O(1)–Cu–N(2)
1.900(2)
2.004(3)2.530(3) Cu–N(3)
Cu–N(2)
1.909(3)
1.994(3)
([M]+, 100%). UV–Vis spectrum, k (nm) [
e
ꢁ 10ꢀ3 (Mꢀ1 cmꢀ1)] in
CH2Cl2: 406 (62.3), 472 (75.2), 528 (13.7), 568 (7.6), 626 (3.6).
89.1(1)
152.6(1)
N(1)–Cu–N(2) 94.1(1)
N(1)–Cu–N(3) 164.1(1)
N(2)–Cu–N(3) 94.8(1)
O(1)–Cu–N(3)Cu–O(1)–C(17) 89.1(1)102.6(2)
2.3. Preparation of 8
8
Bond lengths (Å)
Rh–Cl
Rh–O
Rh–C(17)
C(17)–O
C(18)–C(19)
A mixture of 2-NCH2C6H5NCTPPH (2) (0.03 g, 0.043 mmol) and
tetracarbonyldi-l-chlorodirhodium (0.015 g, 0.039 mmol) were
2.3743(9)
2.043(2)
2.170(3)
1.330(4)
1.376(5)
Rh–N(1)
Rh–N(2)
Rh–N(3)
C(16)–C(17)
C(17)–C(18)
2.038(3)
2.056(3)
2.047(3)
1.446(4)
1.458(4)
refluxed in CH3CN (3 ml) and CH2Cl2 (3 ml) for 12 h [4,5]. After
concentrating the reaction mixture, the residue was dissolved in
5 ml of CH2Cl2 and filtered. The filtrate was concentrated and the
residue was purified over a silica gel (230–400 mesh, 10 g) using
EtOAc/CH2Cl2 [1:20 (v/v)] as the eluent to yield a deep red solution
of 8. Removal of the solvent gave 8 as dark blue solid (0.009 g,
0.010 mmol, 26.9%). Compound 8 was dissolved in CH2Cl2 and lay-
ered with EtOAc [EtOAc/CH2Cl2 = 1:1 (v/v)] to afford dark blue
crystals for single-crystal X-ray analysis. 1H NMR (599.94 MHz,
CDCl3, 20 °C) d: 8.28 [d, 1H, Hb(3), 3J(H–H) = 5.4 Hz]; 8.24 [m, 2H,
o-H(40) and o-H(22) of phenyl group]; 8.19 [d, 1H, Hb(7),
3J(H–H) = 4.8 Hz]; 8.18 [d, 1H, Hb(8), 3J(H–H) = 5.4 Hz]; 8.05 [d,
1H, Hb(12), 3J(H–H) = 4.8 Hz]; 7.99 [d, 1H, Hb(2), 3J(H–H) =
4.8 Hz]; 7.92 [d, 1H, Hb(13), 3J(H–H) = 5.4 Hz]; 7.89 [s, 1H,
Bond angles (°)
Cl–Rh–C(17)
Cl–Rh–O
Cl–Rh–N(1)
Cl–Rh–N(2)
118.86(9)
155.50(7)
91.76(8)
86.00(8)
95.73(8)
89.5(1)
O–Rh–N(1)
O–Rh–N(2)
O–Rh–N(3)
O–Rh–C(17)
Rh–O–C(17)
Rh–C(17)–O
N(1)–Rh–N(2) 89.2(1)
N(1)–Rh–N(3) 172.4(1)
N(2)–Rh–N(3) 90.1(1)
88.7(1)
118.5(1)
85.0(1)
36.6(1)
76.9(2)
66.5(2)
Cl–Rh–N(3)
C(17)–Rh–N(1)
C(17)–Rh–N(2)
C(17)–Rh–N(3)
155.1(1)
88.0(1)
H (19)]; 7.86 [d, 1H, o-H(44) of phenyl group, 3J(H–H) = 7.2 Hz];
a
o-H(22, 26) of phenyl group, 3J(H–H) = 2.2 Hz ]; 7.28 [d, 1H, H (19)];
a
7.76–7.62 [m, o-H and m-H and p-H of phenyl group]; 7.58 [m,
1H, o-H(34) of phenyl group]; 6.74 [t, 1H, p-H(49) of benzyl (Bz)
group, 3J(H–H) = 7.2 Hz]; 6.60 [t, 2H, m-H(48, 50) of Bz group,
3J(H–H) = 7.8 Hz]; 5.69 [d, 2H, o-H(47, 51) of Bz group, 3J(H–H) =
7.8 Hz]; 5.33 [d, 1H, H(45A) of Bz group, 2J(H–H) = 16.2 Hz]; 5.13
[d, 1H, H(45B) of Bz group, 2J(H–H) = 16.2 Hz]. MS(ESI), m/z
(assignment, rel. intensity): 821.3 ([MꢀCl]+, 100%). UV–Vis spec-
7.15 [t, 2H, m-H(50, 52) of phenoxypropyl group, 3J(H–H) = 7.8 Hz];
6.89 [t, 1H, p-H(51) of phenoxypropyl group, 3J(H–H) = 7.2 Hz]; 6.54
[d, 2H, o-H(49, 53) of phenoxypropyl group, 3J(H–H) = 7.8 Hz]; 3.91
[t, 2H, H(45) of phenoxypropyl group, 3J(H–H) = 6.9 Hz]; 3.29 [t,
2H, H(47) of phenoxypropyl group, 3J(H–H) = 5.4 Hz ]; 1.71 [m, 2H,
H(46) of phenoxypropyl group, 3J(H–H) = 6.3 Hz]; 1.38 [d, 1H,
H(17), 3J(H–H) = 1.8 Hz]. Anal. Calc. for C53H40N4Oꢃ0.15CH2Cl2ꢃ
0.1EtOAcꢃ0.5hexane: C, 83.49; H, 5.96; N, 6.89. Found: C, 83.59; H,
trum, k (nm) [
(69.2), 484 (39.9), 584 (22.0).
e
ꢁ 10ꢀ3, Mꢀ1 cmꢀ1] in CH2Cl2: 320 (81.0), 348
5.70; N, 6.74%. UV–Vis spectrum, k (nm) [
CH2Cl2: 362 (51.6), 447 (128.4), 610 (8.6), 659 (14.2), 715 (18.3).
e
ꢁ 10ꢀ3 (Mꢀ1 cmꢀ1)] in
2.4. Spectroscopy
2.2. Preparation of 7
ESR spectra were measured on an X-band Bruker EMX-10 spec-
trometer equipped with an Oxford Instruments liquid helium cryo-
stat. Magnetic field values were measured with a digital counter.
The X-band resonator was a dual-mode cavity (Bruker ER 4116
DM). Proton NMR spectra were recorded at 599.95 MHz on a Var-
ian Unity Inova-600 spectrometer locked on deuterated solvent
and referenced to the solvent peak. Proton NMR is relative to CDCl3
at d = 7.24. The mass spectra [MS(ESI)] were recorded on a Finnigan
A mixture of 1 (0.03 g, 0.04 mmol) and Cu(OAc)2 (0.05 g,
0.27 mmol) are refluxed in CH3CN (10 ml) and CH2Cl2 (10 ml) for
12 h. After concentrating the reaction mixture, the residue was dis-
solved in 5 ml CH2Cl2 and filtered. The filtrate was concentrated
and the residue was purified over a silica gel (230–400 mesh,
15 g) using EtOAc/CH2Cl2 [1:19 (v/v)] as the eluent to yield a deep
red solution of 7. Removal of the solvent gave 7 as a purple solid.
Fig. 1. Molecular configuration and atom-labeling scheme for (a) [2-NCH2CH2CH2-O-C6H5NCTPPH; 1]; (b) [Cu(2-NCH2CH2CH2-O-C6H5NCTPPO); 7] and (c) [Rh(2-
N-CH2C6H5NCTPPO)Cl; 8], with 30% thermal ellipsoids. Hydrogen atoms are omitted for clarity.

246
W.-C. Lin et al. / Polyhedron 42 (2012) 243–248
Fig. 2. (a) X-band ESR spectra for 7 in CH2Cl2 at 293 K. ESR conditions for perpendicular mode of spectrum: microwave frequency of 9.866 GHz, microwave power of
10.086 mW, modulation amplitude of 5.0 G, and modulation frequency of 50.00 kHz. (b) X-band ESR spectra for 7 in CH2Cl2 at 77 K. ESR conditions for perpendicular mode of
spectrum: microwave frequency of 9.483 GHz, microwave power of 10.090 mW, modulation amplitude of 4.0 G, and modulation frequency of 50.00 kHz.
TSQ Ultra EMR mass spectrometer with ESI source. UV–Vis spectra
3. Results and discussion
were recorded at 20 °C on a Hitachi U-3210 spectrophotometer.
3.1. Structure of 1
The X-ray structure of 1 with atom numbering is displayed in
Fig. 1a. The atomsof the porphyrincore are nonplanar, while thepyr-
role rings [N(1)], [N(2)], [N(3)] and [N(4)] are individually planar.
The three pyrrole nitrogens N(1), N(2), and N(3) are coplanar which
defined the 3N reference plane. The CH2CH2CH2OC6H5-substituted
pyrrole N(4) is highly canted from the 3N plane (29.9°). The N-pro-
tonated pyrrole N(2) is tilted by 11.4° while the other two pyrroles
are tilted by 16.6° [N(3)] and 11.4° [N(1)]. The N–H protons (or C–
H proton) is attached to N(2) atom [or C(17) atom] in 1. The devia-
tions from the 3N plane of the atoms C(17) and H(17A) are 0.34
and 0.8 Å, respectively. Likewise H(2A) is located on the same side
at 0.14 Å from the 3N plane.
2.5. Crystallography
Table 1 presents the crystal data as well as other information for
1, 7 and 8. Measurements for 1, 7 and 8 were taken on a Oxford Dif-
fraction Gemini S diffractometer and using monochromatized Mo
Ka radiation (k = 0.71073 Å). Semi-empirical absorption corrections
were made for all complexes. The structures were solved by direct
methods (SHELXTL-97) [9] and refined by the full-matrix least-squares
method. All nonhydrogen atoms were refined with anisotropic
thermal parameters, whereas all hydrogen atoms were placed in
calculated positions and refined with a riding model. Table 2 lists
selected bond distances and angles for complexes 7 and 8.

W.-C. Lin et al. / Polyhedron 42 (2012) 243–248
247
Soret Band
320 nm
348 nm
3.2. Structures of 7 and 8
1.0
0.8
0.6
0.4
0.2
0.0
Insertion of copper(II) acetate to 1 in a methylene chloride–ace-
tonitrile solution in the presence of atmospheric oxygen results in
the formation of a four-coordinate paramagnetic complex 7 in
60.5% yield (Scheme 1). Insertion of rhodium into 2 was carried
out by refluxing the ligand 2 and excess [Rh(CO)2Cl2]2 in methy-
lene chloride–acetonitrile solution in the presence of atmospheric
oxygen yielding a six-coordinate complex 8 (Scheme 1). The X-ray
framework is depicted in Fig. 1b for 7 and in Fig. 1c for complex 8.
All these two structures, four-coordinate distorted square-planar
(DSP) copper complex of 7 and six-coordinate rhodium complex
of 8, show bonding with three nitrogen atoms of the porphyrin
and one extra oxygen atom in common, but compound 8 has, in
additional, one Clꢀ ligand in the axial site and one carbon atom
in the equatorial site. The metal–ligand distances and the angles
are summarized in Table 2.
Q Bands
484 nm
584 nm
300
400
500
600
700
800
wavelength (nm)
Fig. 3. Electronic spectra of 8 in CH2Cl2 solution at 20 °C.
Fig. 4. 1H NMR spectra of 8 at 599.95 MHz in CDCl3: (a) 20 °C, entire spectrum; (b) expansion of the region of 7.5–8.4 ppm of (a) showing six different b-pyrrole protons Hb
and phenyl protons (o-H, m, p-H).

248
W.-C. Lin et al. / Polyhedron 42 (2012) 243–248
The coordination bond lengths Cu–O(1) 1.900(2) Å, Cu–N(1)
3.5. 1H NMR spectroscopic data for 8 in CDCl3
2.004(3) Å, Cu–N(2) 1.909(3) Å and Cu–N(3) 1.994(3) in 7 are with-
in the limit found for Cu(II) porphyrins.
The C(17) in 7 is no longer bonded to copper as indicated by its
longer internuclear distance, 2.530(3) Å for Cuꢃ ꢃ ꢃC(17). This
Cuꢃ ꢃ ꢃC(17) bond distance is largely compared to that observed in
copper(II) square planar complexes [2.007(4) Å] [10].
In solution, the 1H NMR spectrum exhibits six pyrrole reso-
nances [Hb(12), Hb(13), Hb(2), Hb(3), Hb(7), Hb(8)] for 8 (Fig. 4).
The doublet at 8.05 ppm is assigned as Hb(12) with 3J(H–
H) = 4.8 Hz and the other doublet at 7.92 ppm is due to Hb(13) with
3J(H–H) = 5.4 Hz (Fig. 4b). The doublet at 8.28 ppm is assigned as
Hb(3) with 3J(H–H) = 5.4 Hz and the other doublet at 7.99 ppm is
due to Hb(2) with 3J(H–H) = 4.8 Hz. The doublet at 8.19 ppm is as-
signed as Hb(7) with 3J(H–H) = 4.8 Hz and the other doublet at
8.18 ppm is due to Hb(8) with 3J(H–H) = 5.4 Hz. The external benzyl
ligand (Bz) unit in 8 gave rise to series of 1H resonances at 6.74 [t,
1H, p-H(49), 3J(H–H) = 7.2 Hz], 6.60 [t, 2H, m-H(48, 50), 3J(H–
H) = 7.8 Hz], 5.69 [d, 2H, o-H(47, 51), 3J(H–H) = 7.8 Hz], 5.33 [d,
1H, H(45A), 3J(H–H) = 16.2 Hz] and 5.13 [d, 1H, H(45B), 3J(H–
H) = 16.2 Hz] (Fig. 4a). The diamagnetic property of 8 was inferred
from its diamagnetic 1H NMR spectra in CDCl3 (Fig. 4).
The Rhꢃ ꢃ ꢃC(17) distance of 2.170(3) Å in 8 is slightly longer than
that observed in [Rh]–CHCl [2.050(7)–2.161(2)] complexes con-
taining the Rh–CH2Cl moiety [11]. The short distance 2.170(3) Å
for Rh–C(17) clearly signifies as
g
2 interaction between the Rh cen-
ter and the inner carbonyl group. Such a coordination mode was
previously reported by Dolphin and co-workers for Ni(CTTPPO)
(pyridine) (3) [6], by Hung for Co(CTPPO)(NO) (4) [7] and by Rach-
lewicz for Fe(CTPPO)Br (6). This Rh–C(17) contact may be de-
scribed as a weak covalent bond [8]. The geometry around Rh3+
in 8 is described as a distorted octahedron. The bond distance (Å)
for 8 are Rh–Cl = 2.3743(9) and Rh–C(17) = 2.170(3) and the mean
Rh–N(p) = 2.047(3) (Table 2).
4. Conclusion
We adopt the plane of the three strongly bound pyrrole nitro-
gen atoms [i.e., N(1), N(2) and N(3)] as a reference plane 3N for
7–8. The oxygen atom O(1) (or O) in 7 (or 8) is located considerably
far from the 3N plane. In 7, Cu and O(1) are located on the same
sides at 0.21 and 1.27 Å from its 3N plane. In 8, Rh3+ and O are lo-
cated on the different sides at 0.14 and ꢀ1.59 Å from its 3N plane.
The C(17) pyrrole rings bearing the CH2CH2CH2OC6H5 group (or
CH2C6H5) in 7 (or 8) deviate mostly from the 3N plane, thus orient-
ing separately in a dihedral angle of 35.7° (or 25.4°) for 7 (or 8),
whereas a small angle of 9.4°, 3.3° and 3.9° occur with N(1), N(2)
and N(3) pyrrole for 7 and the corresponding angles are 11.7°,
8.9° and 11.5° with N(1), N(2) and N(3) pyrrole for 8. Overall, the
carbon atom [C(17)] which is bonded to oxygen is not bonded to
the copper ion in 7 whereas the rhodium ion, in complex 8, is
bonded to both the oxygen atom and C(17). Complex 8 is diamag-
netic and structurally similar to an C-oxide with paramagnetism in
Ni(CTPPO)(py) (3) [6], Co(CTPPO)(NO) (4) [7], and Fe(HCTPPO)Br
(6) [8].
We have investigated two new inverted N-confused porphyrin
inner C-oxide metal complexes, namely paramagnetic 7 and dia-
magnetic complex 8, and their X-ray structures were established.
Complex 8 has been prepared and characterized by 1H NMR and
O
UV–Vis spectroscopy to have a structure incorporating an
Rh
C
unit. A copper(II) complex 7 has been isolated and characterized
by electron spin resonance spectroscopy.
Acknowledgements
The financial support from the National Science Council of the
ROC under Grants NSC 100-2113-M-005-002 is gratefully
acknowledged. We thank Dr. S. Elango for helpful discussions.
Appendix A. Supplementary data
CCDC 870784, 870785 and 870786 contain the supplementary
crystallographic data for 1, 7 and 8. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
3.3. ESR studies
Complex 7 is paramagnetic because of the d9 configuration of
Cu(II). The unpaired electron resides in the dx2 ꢀ y2 orbital, which
leads to characteristic ESR spectra of 7 in CH2Cl2 at 293 K: four peaks
due to the nuclear spin (I = 3/2) of the Cu and a seven-line pattern
due to the hyperfine interactions with the three nitrogens (I = 1)
of the porphyrin. The ESR spectra are typical for the planar cop-
References
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14N) = 13.0 G for 7 in CH2Cl2 at 293 K (Fig. 2a) and with
so
g = 2.125 and A (63Cu) = 173 for 7 in CH2Cl2 at 77 K (Fig. 2b). These
k
k
hyperfine couplings are similar in magnitude to those of giso = 2.060,
Aiso
(
63Cu) = 79.7 G and Aiso 14N) = 13.0 G obtained from Cu(tpp–N–
(
O) (monomer) in CHCl3 (or CH2Cl2) solution at 293 K [12].
3.4. UV–Vis absorption spectra for compound 8
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The visible spectrum of 8 is shown in Fig. 3 that has a ligand field
of close to Oh symmetry. The spectrum shows an intense near-UV
Soret band, consisting of 320 nm (
e
= 81.0 ꢁ 103 Mꢀ1 cmꢀ1) and a
shoulder at 348 nm (
e
= 69.2 ꢁ 103 Mꢀ1 cmꢀ1), together with two
weaker visible bands at 484 nm (
e
= 39.9 ꢁ 103 Mꢀ1 cmꢀ1) and
584 nm
(e
= 22.0 ꢁ 103 Mꢀ1 cmꢀ1
) assignable to Q bands. As
expected from the Tanabe-Sugano diagram of d6, the electronic
spectrum consists of two bands owing to the transitions
1A1g ? 1T1g (584 nm) and 1Ag ? 1T2g (484 nm) (Fig. 3) [13,14].