Synthesis and characterization of tetraphenylporphyrin manganese(III) complexes of phenylcyanamide ligands

Article abstract of DOI:10.1016/j.ica.2005.03.012

Several complexes of TPPMn-L, where TPP is the dianion of tetraphenylporphyrin and L is monoanion of 4-methylphenylcyanamide (4-Mepcyd) (1), 2,4-dimethylphenylcyanamide (2,4-Me₂pcyd) (2), 3,5-dimethylphenylcyanamide (3,5-Me₂pcyd) (3), 4- methoxyphenylcyanamide (4-MeOpcyd) (4), phenylcyanamide (pcyd) (5), 2-chlorophenylcyanamide (2-Clpcyd) (6), 2,5-dichlorophenylcyanamide (2,5-Cl ₂pcyd) (7), 2,6-dichlorophenylcyanamide (2,6-Cl₂pcyd) (8), 4-bromophenylcyanamide (4-Brpcyd) (9), and 2,3,4,5-tetrachlorophenylcyanamide (2,3,4,5-Cl₄pcyd) (10), have been prepared from the reaction of TPPMnCl and thallium salt of related phenylcyanamide. Each of the complexes has been characterized by IR, UV-Vis and ¹H NMR spectroscopies. 4-Methylphenylcyanamidotetraphenylporphyrin manganese(III) crystallized with one molecule of solvent CHCl₃ in the triclinic crystal system and space group P1? with the following unit cell parameters of: a = 11.596(6) ?; b = 11.768(9) ?; c = 17.81(2) ?; and α, β, γ are 88.91(9)°, 88.16(7)°, 67.90(5)°, respectively; V = 2251(3) ?³; Z = 2. A total of 4234 reflections with I > 2σ(I) were used to refine the structure to R = 0.0680 and R_w = 0.2297. The Mn(III) shows slightly distorted square pyramidal coordination with the 4-methylphenylcyanamide in the axial position, coordinated from nitrile nitrogen. The reduction of each of the TPPMn-L complexes was also examined in dichloromethane and spectroelectrochemical behavior of (1) was investigated and compared to TPPMnCl.

Full text of DOI:10.1016/j.ica.2005.03.012

Inorganica Chimica Acta 358 (2005) 2967–2974
www.elsevier.com/locate/ica
Synthesis and characterization of tetraphenylporphyrin
manganese(III) complexes of phenylcyanamide ligands
a,
a
a
Nasser Safari *, Behrouz Notash , Jafar Mohammad Nezhad ,
a
b
Hossein Chiniforoshan , Hassan Hadadzadeh , Ali R. Rezvani
b
a
Department of Chemistry, Shahid Beheshti University, 1983963113 Evin, Tehran, Iran
Department of Chemistry, Sistan and Baluchestan University, 98135674 Zahedan, Iran
b
Received 18 July 2004; accepted 6 March 2005
Available online 26 April 2005
Abstract
Several complexes of TPPMn–L, where TPP is the dianion of tetraphenylporphyrin and L is monoanion of 4-methylphenylc-
yanamide (4-Mepcyd) (1), 2,4-dimethylphenylcyanamide (2,4-Me2pcyd) (2), 3,5-dimethylphenylcyanamide (3,5-Me2pcyd) (3),
4-methoxyphenylcyanamide (4-MeOpcyd) (4), phenylcyanamide (pcyd) (5), 2-chlorophenylcyanamide (2-Clpcyd) (6), 2,5-dichlor-
ophenylcyanamide (2,5-Cl2pcyd) (7), 2,6-dichlorophenylcyanamide (2,6-Cl2pcyd) (8), 4-bromophenylcyanamide (4-Brpcyd) (9),
and 2,3,4,5-tetrachlorophenylcyanamide (2,3,4,5-Cl4pcyd) (10), have been prepared from the reaction of TPPMnCl and thallium
salt of related phenylcyanamide. Each of the complexes has been characterized by IR, UV–Vis and 1H NMR spectroscopies.
4-Methylphenylcyanamidotetraphenylporphyrin manganese(III) crystallized with one molecule of solvent CHCl3 in the triclinic
˚
˚
˚
crystal system and space group P1 with the following unit cell parameters of: a = 11.596(6) A; b = 11.768(9) A; c = 17.81(2) A; and a,
3
˚
b, c are 88.91(9)ꢀ, 88.16(7)ꢀ, 67.90(5)ꢀ, respectively; V = 2251(3) A ; Z = 2. A total of 4234 reflections with I > 2r(I) were used to
refine the structure to R = 0.0680 and Rw = 0.2297. The Mn(III) shows slightly distorted square pyramidal coordination with the
4-methylphenylcyanamide in the axial position, coordinated from nitrile nitrogen. The reduction of each of the TPPMn–L
complexes was also examined in dichloromethane and spectroelectrochemical behavior of (1) was investigated and compared to
TPPMnCl.
ꢁ 2005 Elsevier B.V. All rights reserved.
Keywords: Manganese porphyrin; Phenylcyanamide; Axial ligand; Spectroelectrochemistry; X-ray diffraction; 1H NMR
1. Introduction
Mn(III)porphyrin is important and has been the center
of recent attentions. The most studied synthetic manga-
nese porphyrins are those with halide [7] or pseudo-halide
[8], nitrate, perchlorate, carboxylate [9], thiolate [10],
phenolate [11], tetrazolate [12], and some other axial li-
gands [7,13,14]. From these studies in contrast to iron
and cobalt analog, Mn(III)porphyrin shows lower affin-
ity for addition of two axial ligands and formation of
the low-spin d4 complexes is very rare. So, most
Mn(III)porphyrin complexes are high-spin five-coordi-
nate and coordinated solvents readily displace the
anionic ligand to yield solvated complexes [11,15]. Fur-
thermore, molecular materials with special properties,
While unambiguous role of manganese porphyrin in
biological process has not been established [1], synthetic
manganese porphyrins have been used extensively as
models for monoxygenases enzymes [2,3], DNA cleav-
age agent [4,5] and could also be considered as a poten-
tial contrast enhancement agent for magnetic resonance
imaging [6]. Effect of axial ligand on the properties of
*
Corresponding author. Tel.: +98 21 2401765; fax: +98 21 2403041.
E-mail address: n-safari@cc.sbu.ac.ir (N. Safari).
0020-1693/$ - see front matter ꢁ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.03.012

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N. Safari et al. / Inorganica Chimica Acta 358 (2005) 2967–2974
such as one or two dimensional electronic based on pla-
nar p-conjugated molecules, are very active field today,
due to their potential applications in new generation
of electronic, magnetic, and/or photonic devices [16].
In this regard, TCNE in [TPPMn][TCNE] Æ 2PhMe has
shown to act as molecule-based magnet [17–20] and phe-
nylcyanamide in (2,5-dimethyl-N,N0-dicyanoquinonedii-
mine)2Cu has shown to exhibit extremely high
conductivity of 500,000 S cmꢀ1 at 3.5 K [21]. In spite
of these important findings, coordination chemistry of
phenylcyanamide has not been fairly explored. How-
ever, Crutchley et al. [22] have largely investigated the
coordination chemistry of phenylcyanamide ligands, in
both neutral and anionic form mostly with Cu and Ru
as metals.
Therefore, due to large p-conjugated system in por-
phyrins and phenylcyanamides and magnetic properties
of Mn(III), which is usually high-spin in porphyrin com-
plexes, we have prepared tetraphenylporphyrin manga-
nese(III) with phenylcyanamide derivatives as axial
ligand. To the best of our knowledge, there is just one
example for complex of Mn with phenylcyanamide
[23]. We have shown with the use of NMR spectroscopy
as a sensitive probe of spin distribution that cyanamides
are capable to transfer spin in long range through
conjugated bond. These complexes were characterized
by means of electronic, IR spectroscopy and the struc-
ture of 4-methylphenylcyanamidotetraphenylporphyrin
manganese(III) was determined by X-ray diffraction as
well.
used as the working and counter electrodes. A silver wire
functioned as a pseudo-reference electrode. Ferrocene
was used as an internal reference [24]. An optically
transparent thin-layer electrode (OTTLE) cell was used
to perform the spectroelectrochemistry [25,26]. The cell
had interior dimensions of roughly 1 · 2 cm with a path
length of 0.2 mm and was fitted with a silver/silver chlo-
ride (Ag/AgCl) as reference electrode and an ITO (in-
dium-tin oxide) coated glass used for the working and
counter electrodes. E1/2 for all complexes was measured
with differential pulse polarography using a Metrohm-
746 VA Trace Analyzer in 10ꢀ3 M concentration in
the presence of 0.1 M of (TBAH) electrolyte.
2.2. X-ray structural determination of [TPPMn(4-
Mepcyd)] Æ CHCl3 (1)
Dark red block-shape crystals of [TPPMn(4-Mepcy-
d)] Æ CHCl3 were grown by slow evaporation of CHCl3
solution in the temperature range of 0–4 ꢀC under N2
atmosphere. Crystal data are presented in Table 1. Data
were collected on an Enraf-Nonius-CAD-4 diffractome-
ter using the SHELXS-97 [27] with graphite monochro-
˚
mated Mo Ka radiation (k = 0.71073 A) and operating
in the x–2h scan mode. Cell parameters were obtained
from 25 accurately centered reflections in the 2h range.
The space group was confirmed by XPREP routine
[28] in SHELXTL program [29]. Data reduction was per-
formed using a locally modified version of the NRC-2
program [30]. The structure was solved by direct method
using SHELXS-97 and difmap synthesis using SHELXL-97
[31]. All non-H atoms were refined with anisotropic
thermal parameters. H atoms constrained to the parent
site using a riding model; SHELXL-97 defaults, C–H 0.93–
2. Experimental
˚
2.1. Reagents and physical measurements
0.98 A. The isotropic factors, Uiso, were adjusted to 20%
UV–Vis spectra were obtained on a shimadzu 2100
spectrometer in a 1 cm cell in chloroform at room tem-
perature. Infrared spectra (4000–600 cmꢀ1) of solid sam-
ples were taken as 1% dispersion in KBr using a
Shimadzu-470 spectrophotometer. 1H NMR spectra
were recorded on a Bruker AC-250 MHz spectrometer
operating in the quadrature mode. The spectra were col-
lected over a 50-kHz band width with 16 K data points
and a 5-ls 45ꢀ pulse. For a typical spectrum, between
1000 and 5000 transients were accumulated with a 50-
ms delay time. The signal-to-noise ratio was improved
by apodization of the free inducting decay. Cyclic vol-
tammetry was performed using a BAS CV-27 voltam-
mograph and plotted on a BAS XY recorder. The
sample cell consisted of a double-walled glass crucible
with an inner volume of ꢁ15 ml, which was fitted with
a Teflon lid incorporating a three-electrode system and
argon bubbler. The cell temperature was maintained at
(25.0 0.1) ꢀC by means of a HAAKE D8 recirculating
bath. BAS 2013 Pt electrodes (1.6 mm diameter) were
Table 1
Crystal data for [TPPMn(4-Mepcyd)] Æ CHCl3 (1)
Empirical formula
Formula weight
Crystal system
Space group
C52H35MnN6 Æ CHCl3
918.17
triclinic
P1
˚
a (A)
11.596(6)
11.768(9)
17.81(2)
88.91(9)
88.16(7)
67.90(5)
2251(3)
2
˚
b (A)
˚
c (A)
a (ꢀ)
b (ꢀ)
c (ꢀ)
3
˚
V (A )
Z
Dcalc. (Mg mꢀ3
)
1.355
20
T (ꢀC)
k (Mo Ka) (A)
˚
0.71073
0.9300 and 0.8500
0.0680
Maximum and minimum transmission
R factora
Rw factorb
0.2297
P
P
a
R = jjFoj ꢀ jFcjj/ jFoj.
ꢀ
ꢁ
1=2
P
P
2
2
b
Rw
¼
wðj F o j ꢀ j F c j Þ = w j F oj
.

N. Safari et al. / Inorganica Chimica Acta 358 (2005) 2967–2974
2969
higher value of the parent site. A final verification of
possible voids was performed using the VOID routine
of the PLATON program [32].
dry dichloromethane and filtered under Schlenk tech-
nique. The volume of filtrate was reduced to 10 ml and
then 50 ml of dried n-hexane was added in portion while
solution was stirring. The precipitate was removed by
filtration and dried in air. Other compounds were pre-
pared by the above procedure except that 4-Mepcyd
was replaced by related phenylcyanamide derivatives.
The IR, UV–Vis data and the yields of products are
summarized in Table 2.
2.3. Materials
Dichloromethane, N,N-dimethylformamide, metha-
nol, p-chloranil, n-hexane, benzaldehyde, benzophe-
none, I2, Na, and Mg were of reagent grade and
purchased from Merck, pyrrole and tetrabutylammo-
nium hexafluorophosphate was from Fluka and Aldrich,
respectively. Dichloromethane and methanol were pre-
dried and distilled over P2O5 and Mg + I2, respectively,
prior to use. n-Hexane was pre-dried and distilled over
Na and benzophenone. Tetrabutylammonium hexaflu-
orophosphate (TBAH) was twice recrystallized from
ethanol:water (1:1) and vacuum dried at 110 ꢀC. All
manipulations involving phenylcyanamide coordination
to manganese(III)porphyrin were carried out under
nitrogen using standard Schlenk technique. Tetra-
phenylporphyrin (TPPH2) and TPPMnCl were synthe-
sized by Lindsey [33] and Adlerꢀs method [34],
respectively. Extra care to exclude trace of impurity of
l-oxo dimer and pre-treatment of TPPMnCl with HCl
was necessary. Preparation of the thallium salts of phe-
nylcyanamide ligands (pcydꢀTl+) has been previously
reported [35]. Caution: Thallium is toxic.
3. Results and discussion
The synthesis of compounds (1–10) were achieved
according to metathesis reaction at ambient temperature
(Scheme 1).
This reaction is very sensitive to moisture and in less
extent to O2, so existence of water results in the forma-
tion of l-oxo dimer, TPPMn–O–MnTPP, during prepa-
ration. l-Oxo dimer impurity is hard to remove, since
chromatography on silica gel or aluminium oxide may
lead to its additional formation. The reaction yields were
quantitative, although during the process of precipita-
tion 20–30 percent of the products were lost. Com-
pounds (1–10) are slightly sensitive to moisture or
oxygen. No effort was made to exclude air for NMR,
IR and electronic spectroscopy, but crystals of (1) were
grown under N2 atmosphere. All compounds have fair
solubility in all solvents except saturated hydrocarbons.
Addition of HCl, gas or solution, completely converts
the phenylcyanamide derivative complexes to
TPPMnCl.
2.4. Preparation of TPPMn(4-Mepcyd) (1)
80 mg of powders of TPPMnCl (0.11 mmol) and
200 mg of thallium salt of 4-Mepcyd (0.59 mmol) were
placed together in a two-neck round-bottom flask. After
30 min of vacuum and then under nitrogen atmosphere,
50 ml dry methanol was transferred to the reaction flask
and stirred for 24 h. Then, the solvent was removed un-
der reduced pressure and the residue was dissolved in
IR spectroscopy is a proper tool for characterisation
of phenylcyanamide metal complexes. It can differentiate
nitrile versus amine coordination in both anionic and
neutral form of phenylcyanamides [36]. Neutral phenyl-
cyanamide has shown t(C„N) around 2225–2249 cmꢀ1
Table 2
UV–Vis electronic absorptiona and IR datab for TPPMn–L complexes and thallium salts of phenylcyanamide
Complex
UV–Visc
t(NCN)d,e
Yield (%)
Soret band
Q bands
Thallium salt
Complex
TPPMn(4-Mepcyd)
TPPMn(2,4-Me2pcyd)
TPPMn(3,5-Me2pcyd)
TPPMn(4-MeOpcyd)
TPPMn(pcyd)
473
474
470
471
473
477
481
479
475
482
575, 609
580, 617
576, 612
578, 614
581, 619
582, 620
584, 620
583, 620
581, 619
583, 620
2060
2060
2095
2065
2055
2080
2110
2045
2045
2095
2090
2075
2115
2090
2090
2095
2120
2110
2085
2110
80
75
76
72
76
73
73
74
78
76
TPPMn(2-Clpcyd)
TPPMn(2,5-Cl2pcyd)
TPPMn(2,6-Cl2pcyd)
TPPMn(4-Brpcyd)
TPPMn(2,3,4,5-Cl4pcyd)
a
In nm.
In cmꢀ1
b
.
c
d
e
In chloroform.
KBr disk.
Strong.

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N. Safari et al. / Inorganica Chimica Acta 358 (2005) 2967–2974
CH3OH
r.t
confirm existence of Mn(III) oxidation state, since the
TPPMnCl + TlL
TPPMn-L + TlCl ↓
UV–Vis spectra of metalloporphyrins are sensitive to
oxidation state of metals. Fig. 1 also indicates higher
absorption coefficient of (1) in comparison to TPPMnCl,
which is expected for coordination of long p-conjugated
axial ligand.
5
3
6
4
N C N
L
=
1
2
3.1. NMR studies
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
2,3,5,6 H
3,5,6 H
4 Me
2,4 Me
3,5 Me
4 MeO
Proton NMR spectroscopy is found to be highly
informative in terms of evaluation of the axial phenylc-
1
yanamide derivatives (1–10). The H NMR spectra of
2,4,6 H
2,3,5,6 H
2,3,4,5,6 H
3,4,5,6 H
3,4,6 H
chloro substituted phenylcyanamide complexes and
methyl substituted phenylcyanamide complexes are
shown in Figs. 2 and 3, respectively. Full assignment
of signals for compounds (1–10) is presented in Table
3. Assignments are made on the basis of:
2 Cl
2,5 Cl
2,6 Cl
3,4,5 H
2,3,5,6 H
4 Br
2,3,4,5 Cl
(i) previous assignments for Mn(III)tetraarylporphy-
rin complexes,
(ii) relative intensity and line width of the signals,
(iii) comparison of the pattern of signals in phenylcya-
namide complexes (1–10).
(10) 6 H
Scheme 1. Metathesis reaction.
[22], and coordinated nitrile in [TPPMn][TCNE] Æ
2PhMe was reported at 2192 cmꢀ1 [18], where coordina-
tion of anionic phenylcyanamide ligand seems to occur
via nitrile nitrogen and produce a strong bond in the fre-
quency lower than 2150 cmꢀ1. The t(N@C@N) frequen-
cies for thallium salts and compounds (1–10) are listed in
Table 2. In each case, the tCN absorption is consistent
with the presence of Nꢀ@C@N–C6H5 entity. Fig. 1
shows UV–Vis spectrum of (1) in dichloromethane in
comparison to TPPMnCl. This spectrum and the results
for other compounds (1–10) in Table 2 indicate similarity
of electronic spectra of prepared compounds, and
For i.e. trace of (10) in Fig. 2 shows a signal at
13.9 ppm which arises from the only hydrogen present
in ortho position of phenylcyanamide, when compound
(10) is replaced by (8), two kinds of hydrogen, meta and
para in the ratio of 2:1 were assigned in 15.3 and
ꢀ11.9 ppm, respectively, see trace of (8) in Fig. 2. These
1
assignments were reconfirmed with the H NMR spec-
trum of (6) in Fig. 2 and also in comparison to (1–5,
Fig. 2. 1H NMR spectra of manganese(III)porphyrin complexes:
TPPMn(2,3,4,5-Cl4pcyd) (10), TPPMn(2,6-Cl2pcyd) (8), and
TPPMn(2-Clpcyd) (6), in CDCl3 at 300 K.
Fig. 1. UV–Vis spectra of TPPMnCl (––) and TPPMn(4-Mepcyd)
(---), 1.25 · 10ꢀ5 M in dichloromethane.

N. Safari et al. / Inorganica Chimica Acta 358 (2005) 2967–2974
2971
withdrawing groups are present in the phenylcyanamide.
This increase in the pyrrole-H contact shift reflected an
increase in Por ! Mn(III) p charge-transfer as expected.
The same trend has been shown for halide coordination
to Mn(III) tetraphenylporphyrin [8,10].
The axial protons of phenylcyanamides (L) are
clearly resolved and all have smaller line width than pyr-
role protons. The alternating upfield–downfield shift
pattern (+30 to ꢀ20 ppm) for L in TPPMn–L is indica-
tive of contact interaction, which is dominant mecha-
nism in Mn(III) porphyrin [38]. The contact term
arises from the presence of unpaired electron density
on the ligand. This is an interesting system in which spin
delocalisation from Mn reaches to hydrogen that is
˚
more than 10 A away.
3.2. Electrochemistry and spectroelectrochemistry
The electrochemistry of compounds (1–10) involves
many
oxidation/reduction
processes.
Half-wave
potentials for the reduction of MnIII/MnII in 0.1 M tetra-
butylammonium hexafluorophosphate (TBAH) in
dichloromethane are given in Table 4, and a typical cyclic
voltammogram in the ranges of 82 to ꢀ1168 mV is
presented in Fig. 4. Here, we concentrate on the first
reduction/oxidation waves.
Fig. 3. 1H NMR spectra of manganese(III)porphyrin complexes:
TPPMn(pcyd) (5), TPPMn(4-Mepcyd) (1), and TPPMn(3,5-Me2pcyd)
(3), in CDCl3 at 300 K.
7, 9) compounds. Syntheses of these ten substituted phe-
1
nylcyanamide complexes and comparison of H NMR
The first reduction of TPPMn–L (1–10) in dichloro-
methane occurs at E1/2 values between ꢀ0.31 and
ꢀ0.38 V with a peak potential separation, jEa ꢀ Ecj, of
100–150 mV for a potential scan rate of 0.1 V sꢀ1. The
cyclic voltammograms are quasi-reversible and as seen
from Table 4 the reduction of TPPMn–L becomes more
difficult by 70 mV as electron-donating substituents re-
place electron-withdrawing groups on the phenylcyana-
of them unambiguously confirm our assignments. The
pyrrole-H signals of the TPP complexes appear as broad
peaks and are located at ꢀ21 to ꢀ25 ppm. Resonances
for the meta, ortho and para-H of phenyl in TPP are
seen in the range of 7.5–8.3 ppm. These data prove that
Mn in these complexes is Mn(III) and high-spin (S = 2)
[8,10,37]. The position of pyrrole peaks indicates that
phenylcyanamides are pseudo-halide ligands [22], since
the same isotropic shift has been shown to exist for
TPPMn(III)–X (X stand for F, Cl, Br and I). The
pyrrole-H shift increases upfield when more electron-
mides. Kelly and Kadish [39] have shown that MnIII
/
MnII reduction depends on the binding strength of
anionic ligands in TPPMn–X. Comparison of these
half-wave potentials to that of tetraphenylporphyrin
manganese(III) bearing other anionic ligands indicates
Table 3
1H NMR spectral data of TPPMn–L complexesa,b
Complex
pyrr-H
m-H
p-H
H2
H3
H4
24.2
H5
H6
TPPMn(4-Mepcyd)
TPPMn(2,4-Me2pcyd)
TPPMn(3,5-Me2pcyd)
TPPMn(4-MeOpcyd)
TPPMn(pcyd)
ꢀ22.3
ꢀ21.8
ꢀ22.2
ꢀ22.2
ꢀ22.2
ꢀ23.2
ꢀ24.3
ꢀ22.8
ꢀ23.3
ꢀ25.0
8.20
8.20
8.30
8.20
8.20
8.30
8.20
8.20
8.30
8.20
7.50
7.50
7.70
7.50
7.50
7.70
7.60
7.70
7.70
7.70
ꢀ16.2
17.6
17.8
14.4
ꢀ4.4
17.3
17.6
14.1
13.4
15.3
17.2
17.8
14.4
ꢀ4.4
17.3
17.6
14.1
ꢀ16.2
21.1
24.3
ꢀ9.6
ꢀ14.6
ꢀ15c
ꢀ14.4
ꢀ14.6
ꢀ15c
ꢀ14.4
19.8
ꢀ20c
10
d
TPPMn(2-Clpcyd)
TPPMn(2,5-Cl2pcyd)
TPPMn(2,6-Cl2pcyd)
TPPMn(4-Brpcyd)
TPPMn(2,3,4,5-Cl4pcyd)
a
ꢀ13.4
ꢀ12.3
ꢀ11.9
15.3
17.2
ꢀ16c
ꢀ16c
13.9
In CDCl3, data in ppm vs. TMS reference at 0.00 ppm at 300 K.
b
c
The o-H peak is not clearly resolved, but appears to occur as a very broad resonance near CDCl3.
Very broad.
Not observed.
d

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N. Safari et al. / Inorganica Chimica Acta 358 (2005) 2967–2974
Table 4
The first half-wave potentialsa (E1/2) measured by DPP for TPPMn–L
complexes
Complex
Mn(III/II)
TPPMn(4-Mepcyd)
TPPMn(2,4-Me2pcyd)
TPPMn(3,5-Me2pcyd)
TPPMn(4-MeOpcyd)
TPPMn(pcyd)
ꢀ360
ꢀ360
ꢀ340
ꢀ380
ꢀ330
ꢀ340
ꢀ310
ꢀ340
ꢀ340
ꢀ310
TPPMn(2-Clpcyd)
TPPMn(2,5-Cl2pcyd)
TPPMn(2,6-Cl2pcyd)
TPPMn(4-Brpcyd)
TPPMn(2,3,4,5-Cl4pcyd)
a
In mV vs. Ag/AgCl, at 25 ꢀC. In dichloromethane (TBAH 0.1 M)
at a scan rate of 100 mV sꢀ1
.
Fig. 5. Optically transparent thin-layer electrode cell electronic spectra
of (1) (0.1 M TBAH electrolyte) in dichloromethane. Potential range
for forward reaction ꢀ0.7 to ꢀ1.2, for backward reaction ꢀ0.3 to
+0.2 V vs. Ag/AgCl reference electrode.
ciently stable in dichloromethane in spite of quasi-
reversible behavior of their cyclic voltammograms
[12,39,40]. This is an excellent property that makes these
compounds a good candidate as a building block for
metala–L–metalb interaction, which is important for
switching device or material with special magnetic and
electronic properties. Synthesize of dicyanamide metal-
loporphyrins is under consideration in our laboratory.
3.3. Crystal and molecular structure of [TPPMn(4-
Mepcyd)] Æ CHCl3 (1)
Fig. 4. Cyclic voltammogram of (1), 10ꢀ3 M in dichloromethane
shows Mn(III/II) couple in the range of 82 to ꢀ1168 mV, between scan
rates of 50–250 mV sꢀ1 (I–V).
The structure of TPPMn(4-Mepcyd) (1) has been
studied by X-ray diffraction. Two views of (1) are shown
in Fig. 6. Selected bond lengths and angles are presented
in Table 5. The manganese is five-coordinate and struc-
tural parameters are consistent with the parameters ob-
served for high-spin five-coordinate Mn(III) porphyrins.
that phenylcyanamide derivatives used in this work have
binding ability similar to Iꢀ, SCNꢀ, Brꢀ and Clꢀ anions
[39,40], since they have comparable E1/2 under the same
experimental condition.
˚
The Mn–Nporp distance (average 2.00 A) is similar to the
distance found for TPPMnCl and other nitrosoarene
analogous porphyrin complexes [7,14,41]. The equato-
rial Mn–Nporp bond distance is smaller than axial Mn–
Spectroelectrochemical spectrum of compound (1)
with OTTLE cell under the one electron controlled po-
tential reduction at ꢀ1.2 to 0.2 V is shown in Fig. 5.
As the reaction proceeds, the intensity of soret band at
473 nm decreases and new bands at 457 and 395 nm ap-
pear. The spectral changes, indicated in Fig. 5, were
reversible and the spectrum of the original Mn(III)
could be fully regenerated upon controlled potential
up to 0.2 V. The electrogenerated TPPMnII–L deriva-
tives seem to be stable in dichloromethane, so that loss
of the axial ligand does not occur on the spectroelectro-
chemistry time scale (1–2 h). The electrogenerated
TPPMnII–(X), where X = Clꢀ, Brꢀ, Iꢀ, N3ꢀ, were suffi-
˚
N(5) bond distance (2.08 A). This difference in the
Mn–N bond distance can be attributed to a spin-state ef-
fect. It has shown that manganese has an unoccupied
dx2ꢀy2 and an occupied dz2 orbital. The distance from
the Mn(III) to the center of the four pyrrole nitrogen
˚
plane is 0.24 A. This distance was reported to be
˚
0.27 A for TPPMnCl [7].
The phenyl groups in most tetraphenylporphyrin
compounds are almost perpendicular to the mean plane
of the porphyrin ring, this does not allow any p interac-
tion between the benzene p system and the extensive
porphyrin p system. The torsion angle that the phenyl

N. Safari et al. / Inorganica Chimica Acta 358 (2005) 2967–2974
2973
Fig. 6. Thermal ellipsoid plot and numbering scheme of TPPMn(4-Mepcyd). Ellipsoids correspond to 30% probability.
rings make with the porphyrin ring is required to be
greater than 70ꢀ because of interactions between the
phenyl hydrogens and the outer pyrrole hydrogens
[42]. These torsion angles for TPPMn(4-Mepcyd) (1)
are in the range between 87.3ꢀ and 91.1ꢀ.
[(NH3)5Ru]2}[ClO4] [43]. Planarity of the phenylcyana-
mide ligand optimizes the p interaction between the phe-
nyl ring and the cyanamide group. The above crystal
structure observation has important consequences to
metal–phenylcyanamide coupling.
The angle of metal with axial CN is 135.8ꢀ. Crutchley
[22] has shown that this angle ranges from 120ꢀ to 180ꢀ,
depending on the amount of contribution from these
two resonance forms:
The phenylcyanamide has been coordinated to the
Mn from nitrile nitrogen and Mn–N(5) distance is
˚
2.08 A. This is smaller than the distance reported for
coordination of anionic phenylcyanamide to Mn(II),
˚
2.15 A as expected [23]. NCN moiety is almost linear
Ph–N–CBN $ Ph–N@C@N
180ꢂ
120ꢂ
with the N(5)–C(21)–N(22) angle of 174.2ꢀ. Also the tor-
sion angle C(21)–N(22)–C(23)–C(28), 13ꢀ, shows that
the phenyl ring is approximately planar with cyanamide
group. This angle was reported to be 12ꢀ for {l-Dicyd-
Angle of 135.8ꢀ and the N(5)–C(21) distance of
˚
1.17 A confirm some p donation from phenylcyanamide
ligand to manganese d-orbitals [44,45].

2974
N. Safari et al. / Inorganica Chimica Acta 358 (2005) 2967–2974
Table 5
[13] R. Guilard, K. Perie, J.-M. Barbe, D.J. Nurco, K.M. Smith, E.V.
Caemelbecke, K.M. Kadish, Inorg. Chem. 37 (1998) 973.
[14] M.L. Yates, A.M. Arif, J.L. Manson, B.A. Kalm, B.M. Burkhart,
J.S. Miller, Inorg. Chem. 37 (1998) 840.
a
˚
Selected bond lengths (A) and angles (ꢀ) for [TPPMn(4-Mepcy-
d)] Æ CHCl3 (1)
Bond lengths
Bond angles
[15] T.R. Janson, L.J. Boucher, J.J. Katz, Inorg. Chem. 12 (1973) 940.
[16] J.S. Miller, A.J. Epstein, Angew. Chem. Int. Ed. Engl. 33 (1994)
385.
Mn–N(1)
Mn–N(2)
1.972(1)
2.010(1)
2.022(1)
2.011(1)
2.075(1)
1.171(2)
1.250(2)
1.452(2)
1.31(2)
Mn–N(5)–C(21)
N(5)–C(21)–N(22)
C(21)–N(22)–C(23)
N(1)–Mn–N(2)
N(2)–Mn–N(4)
N(4)–Mn–N(3)
N(3)–Mn–N(1)
N(2)–Mn–N(3)
N(1)–Mn–N(4)
N(1)–Mn–N(5)
N(3)–Mn–N(5)
N(4)–Mn–N(5)
135.80(1)
174.20(1)
120.70(1)
89.2(5)
Mn–N(3)
Mn–N(4)
Mn–N(5)
[17] E.J. Brandon, C. Kollmar, J.S. Miller, Am. Chem. Soc. 120
(1998) 1822.
90.1(4)
88.0(4)
89.5(5)
[18] D.K. Rittenberg, J.S. Miller, Inorg. Chem. 38 (1999) 4838.
[19] F. Mascarenhas, K. Falk, P. Klavins, J.S. Schilling, Z. Tom-
kowicz, W. Haase, J. Magn. Magn. Mater. 231 (2001) 172.
[20] C.M. Wynn, M.A. Girtu, W.B. Brinckerhoff, K.-I. Sugiura, J.S.
Miller, A.J. Epstein, Chem. Mater. 9 (1997) 2156.
[21] A. Aumu¨ller, P. Erk, G. Klebe, S. Hu¨nig, J.U. Von Schu¨tz, H.-P.
Werner, Angew. Chem. Int. Ed. Engl. 25 (1986) 740.
[22] R.J. Crutchley, Coord. Chem. Rev. 219 (2001) 125, and references
therein.
N(5)–C(21)
C(21)–N(22)
N(22)–C(23)
C(23)–C(24)
C(23)–C(28)
169.8(5)
161.8(4)
101.3(4)
92.7(5)
1.382(2)
96.8(5)
a
Estimated standard deviations are in parentheses. Torsion angle
C(21)–N(22)–C(23)–C(28): 13(2)ꢀ.
[23] A. Escuer, N. Sanz, R. Vicente, F.A. Mautner, Inorg. Chem. 42
(2003) 541.
[24] T. Gennett, D.F. Milner, M.J. Weaver, J. Phys. Chem. 89 (1985)
2787.
Acknowledgments
[25] M. Krejcik, M. Danek, F. Hartl, J. Electroanal. Chem. 317 (1991)
179.
We thank the research and graduate study councils of
Shahid Beheshti University for financial support, Prof.
R.J. Crutchley (Carleton University, Ottawa) who pro-
vided us with the electrochemical and spectroelectro-
chemical study facilities and Prof. J.F. Harrod (Mac
Gill University) for his help in crystal structure
determination.
[26] C.E.B. Evans, Ph.D Thesis. Carleton University, Canada, 1997.
[27] G.M. Sheldrick, SHELXS-97, Program for Crystal Structure Solu-
tion, University of Go¨ttingen, Germany, 1997.
[28] Bruker, XPREP-97, Version 5.10, X-ray Data Preparation and
Reciprocal Space Exploration Program, Bruker AXS, Inc, Mad-
ison, WI, USA, 1997.
[29] Bruker, SHELXTL-97, Version 5.10, The Complete Software Package
for Single Crystal Structure Determination, Bruker AXS, Inc,
Madison, WI, USA, 1997.
[30] F.R. Ahmed, S.R. Hall, M.E. Pippy, C.P. Huber, NRC crystal-
lographic computer programs for the IBM/360, Accession Nos.
133–147, J. Appl. Cryst. 6 (1973) 309.
Appendix A. Supplementary data
[31] G.M. Sheldrick, SHELXSL-97, Program for the Refinement of
Crystal Structures, University of Go¨ttingen, Germany, 1997.
[32] A.L. Spek, PLATON, Molecular Geometry Program, University
of Utrecht, 2000.
Supplementary data associated with this article can
be found, in the online version at doi:10.1016/
j.ica.2005.03.012.
[33] J.S. Lindsey, I.C. Schreiman, H.C. Hsu, P.C. Kearney, A.M.
Marguerettaz, J. Org. Chem. 52 (1987) 827.
[34] A.D. Adler, F.R. Longo, F. Kampas, J. Kim, J. Inorg. Nucl.
Chem. 32 (1970) 2443.
References
[35] R.J. Crutchley, M.L. Naklicki, Inorg. Chem. 28 (1989) 1955.
[36] R.J. Crutchley, M.L. Naklicki, Inorg. Chem. 28 (1989) 1958.
[37] G.N. La Mar, F.A. Walker, J. Am. Chem. Soc. 95 (1973) 6950.
[38] W.D. Philips, NMR of Paramagnetic Molecules: Principles and
Application, Academic Press, New York, 1973.
[1] L.J. Boucher, Coord. Chem. Rev. 7 (1972) 289.
[2] G. Meunier, D. de Montauzon, J. Bernadou, G. Grassy, M.
Bonnfous, S. Cros, B. Meunier, Mol. Parmacol. 33 (1988) 93.
[3] J.T. Groves, T.E. Nemo, J. Am. Chem. Soc. 105 (1983) 5786.
[4] M. Rodriguez, A.J. Bard, Inorg. Chem. 31 (1992) 1129.
[5] J. Bernadou, G. Pratviel, F. Bennis, M. Girardet, B. Meunier,
Biochemistry 28 (1989) 7268.
[39] S.L. Kelly, K.M. Kadish, Inorg. Chem. 21 (1982) 3631.
[40] K.M. Kadish, M. Sweetland, J.S. Cheng, Inorg. Chem. 17 (1978)
2795.
[6] R. Fawwaz, P. Bohidiewicz, D. Lavallee, T. Wang, S. Oluwole, J.
Newhouse, P. Alderson, Nucl. Med. Biol. 17 (1990) 65.
[7] A. Tulinsky, B.M.L. Chen, J. Am. Chem. Soc. 99 (1977) 3647.
[8] G.N. La Mar, F.A. Walker, J. Am. Chem. Soc. 97 (1975) 5103.
[9] P. Turner, M.J. Gunter, Inorg. Chem. 33 (1994) 1406.
[10] L. Mu, J. Huang, Y. Zhou, P. Shen, Polyhedron 16 (1997) 2885.
[11] G.M. Godziela, D. Tiiotta, H.M. Goff, Inorg. Chem. 25 (1986)
2142.
[41] S.J. Fox, L. Chen, M.A. Khan, G.B. Richter-Addo, Inorg. Chem.
36 (1997) 6465.
[42] E.B. Fleischer, Acc. Chem. Res. 3 (1970) 105.
[43] M.A.S. Aquino, F.L. Lee, E.J. Gabe, C. Bensimon, J.E. Greedan,
R.J. Crutchley, J. Am. Chem. Soc. 114 (1992) 5130.
[44] P.L. Fabre, A.M. Galibert, B. Soula, F. Dahan, P. Castan, J.
Chem. Soc., Dalton Trans. (2001) 1529.
[45] A.R. Rezvani, H. Hadadzadeh, B. Patrick, Inorg. Chim. Acta 336
(2002) 125.
[12] R. Guilard, N. Jagerovic, J.M. Barbe, Polyhedron 14 (1995) 3041.