N,N′-diethyl and N-ethyl,N′-methyl glyoxal-bridged cyclams: synthesis, characterization, and bleaching activities of the corresponding Mn(II) complexes

Article abstract of DOI:10.1007/s11243-017-0146-8

The synthesis and characterization of N,N′-diethyl (L-Et,Et) and N-ethyl,N′-methyl (L-Et,Me) glyoxal-bridged cyclam ligands are described, together with the X-ray crystal structure of the complex [MnCl₂(L-Et,Me)]. Bleaching of morine in the presence of hydrogen peroxide by the corresponding Mn catalysts [MnCl₂(L-Et,Et)], [MnCl₂(L-Et,Me)] and [MnCl₂(L-Me,Me)] has been studied in aqueous solution at three different pH values (8.0, 8.75, and 9.0). The results clearly show that increasing pH has a different effect on the three catalysts, and that the dimethyl derivative is by far the most active.

Full text of DOI:10.1007/s11243-017-0146-8

Transit Met Chem
DOI 10.1007/s11243-017-0146-8
N,N0-diethyl and N-ethyl,N0-methyl glyoxal-bridged cyclams:
synthesis, characterization, and bleaching activities
of the corresponding Mn(II) complexes
Giovanni Di Mauro1 Alfonso Annunziata1 Maria Elena Cucciolito1
•
•
•
Matteo Lega2 Stefano Resta2 Angela Tuzi1 Francesco Ruffo1
•
•
•
Received: 15 March 2017 / Accepted: 3 April 2017
Ó Springer International Publishing Switzerland 2017
Abstract The synthesis and characterization of N,N0-di-
ethyl (L-Et,Et) and N-ethyl,N0-methyl (L-Et,Me) glyoxal-
bridged cyclam ligands are described, together with the
X-ray crystal structure of the complex [MnCl2(L-Et,Me)].
Bleaching of morine in the presence of hydrogen peroxide
by the corresponding Mn catalysts [MnCl2(L-Et,Et)],
[MnCl2(L-Et,Me)] and [MnCl2(L-Me,Me)] has been
studied in aqueous solution at three different pH values
(8.0, 8.75, and 9.0). The results clearly show that increas-
ing pH has a different effect on the three catalysts, and that
the dimethyl derivative is by far the most active.
catalysis [4, 8], and the development of metal-based
imaging and therapeutic agents in medicine [10].
In particular, manganese(II) complexes of formula
[MnCl2(L-R,R0)] show well-proven peroxide-based
bleaching activity, which has been the object of extensive
studies documented in the patent literature [11–17]. These
complexes were initially targeted as potential oxidation
catalysts because the rigid cross-bridged ligand strongly
binds the manganese ion and prevents it from being
deactivated in the form of MnO2. Additional distinctive
properties are the presence of the alkyl groups R and R0,
which preclude dimerization and consequent deactivation
of the catalyst, and the all-tertiary nature of the nitrogen
atoms, which minimizes the possibility of ligand oxidation
and catalyst destruction.
Introduction
Both [MnCl2(L-Me,Me)] and [MnCl2(L-Et,Et)] are
patented bleach catalysts, which have been heavily inves-
tigated by the laundry detergent industry because of their
ability to activate O2/H2O2 in water and remove stain
molecules from cloth. The crystal structures of both com-
plexes [5, 18] have been recently reported, demonstrating
also the academic interest [19, 20] toward this class of
compounds. Despite this attention, the detailed synthesis
of L-Et,Et has never been reported in the literature, as
well as the preparation of the mixed L-Et,Me species,
which has also been mentioned in the patent literature.
Aiming to fill this gap, this paper presents the synthesis of
L-Et,Et and L-Et,Me (Scheme 1) along with their NMR
characterization. In addition, the preparation of the corre-
sponding MnCl2 complexes, which have been tested in the
bleaching of morine with hydrogen peroxide, in compar-
ison with [MnCl2(L-Me,Me)], and the crystal structure of
[MnCl2(L-Et,Me)] are reported.
Glyoxal-bridged cyclam-based ligands (L-R,R0) have
attracted much interest [1–9] in the last decades, due to
their ability to coordinate mid–late transition metals
(Scheme 1).
These macrocycles can be easily N-functionalized with
various groups, allowing the preparation of a wide range of
ligands suitable for important applications such as for
Electronic supplementary material The online version of this
article (doi:10.1007/s11243-017-0146-8) contains supplementary
material, which is available to authorized users.
& Francesco Ruffo
ruffo@unina.it
1
`
Dipartimento di Scienze Chimiche, Universita di Napoli
Federico II, Complesso Universitario di Monte S. Angelo,
Via Cintia 21, 80126 Naples, Italy
2
Fater SpA, Via Ardeatina 100, 00040 Pomezia, Rome, Italy
123

Transit Met Chem
Scheme 1 Synthesis of the glyoxal-bridged cyclams L-Et,Me and L-Et,Et: (i) glyoxal, MeCN, 50 °C, 5 h; (ii) EtI, MeCN, 55 °C, 5d; (iii) MeI,
MeCN, RT, 3d; (iv) NaBH4, EtOH, RT, 3d; (v) NaBH4, EtOH, RT, 3d
acetonitrile (4 9 25 mL) and diethyl ether (3 9 50 mL),
Experimental
and dried under vacuum (yield 15.7 g, 47%).
Materials and methods
3-Et,Et
All solvents and reagents were purchased from Sigma-
Aldrich and used without further purification. NMR spectra
were recorded in D2O (internal standards: HDO, d 4.80, for
proton spectra, and dioxane, d 67.0, for carbon spectra) or
CD3CN (internal standards: CD2HCN, d 1.96, for proton
spectra, and 13CD3CN, d 1.39, for carbon spectra), using a
Bruker 400 DRX spectrometer. UV visible spectra were
recorded with a JASCO spectrophotometer. The following
abbreviations are used for describing NMR multiplicities:
s, singlet; dd, double doublet; ddd, double double doublet;
dq, double quartet; t, triplet; dt, double triplet; td, triple
doublet; m, multiplet. Precursor 1 was prepared according
to a described procedure [21].
Calcd. (%) for C16H32N4I2: C, 35.97, H, 6.04, N, 10.49;
found (%): C, 35.78, H, 6.12, N, 10.34. 1H NMR
(400 MHz, D2O) d 4.74 (s, 2H, H6), 4.45 (dt, J = 13.2,
4.4 Hz, 2H, Ha4), 3.97 (dq, J = 14.5, 7.2 Hz, 2H, CHHMe),
3.84 (dd, J = 13.0, 4.5 Hz, 2H, He3), 3.64 (dq, J = 14.5,
7.2 Hz, 2H, CHHMe), 3.55 (dt, J = 13.3, 3.9 Hz, 2H, Ha3),
3.36–3.24 (m, 4H, H4e and H5e), 3.24–3.15 (m, 2H, He1), 3.12
(dt, J = 14.1, 3.7 Hz, 2H, Ha5), 2.74 (td, J = 12.6, 3.4 Hz,
2H, Ha1), 2.48–2.27 (m, 2H, H2a), 2.03–1.88 (m, 2H, He2),
1.46 (t, J = 7.2 Hz, 6H, Me). 13C NMR (100 MHz, D2O) d
76.5, 60.3, 55.4, 51.5, 46.6 (x2), 18.4, 6.7. The atom
labelling is shown in Scheme 2.
Synthesis of 3-Et,Me
Synthesis of 3-Et,Et
Ethyl iodide (291 g, 1.86 mol) was added to a solution of 1
(13.8 g, 0.0621 mol) in acetonitrile (450 mL), and the
mixture was stirred for 5 days at 55 °C. After cooling to
room temperature, the suspension was filtered, and methyl
iodide (27.0 g, 0.190 mol) was added to the filtrate, which
was stirred for 3 days at room temperature. The resulting
Ethyl iodide (291 g, 1.86 mol) was added to a solution of 1
(13.8 g, 0.0621 mol) in acetonitrile (450 mL), and the
mixture was stirred for 5 days at 55 °C to give a pale
yellow crystalline solid. After cooling to room temperature,
the product (3-Et,Et) was filtered off, washed with
123

Transit Met Chem
Scheme 2 Atom labelling for 3-Et,Et, 3-Et,Me, L-Et,Me, and L-Et,Et
L-Et,Et
white solid (3-Et,Me) was collected by filtration, washed
with acetonitrile (3 9 20 mL) and diethyl ether
(3 9 20 mL), and dried under vacuum (yield 13.2 g, 41%).
Calcd. (%) for C16H34N4: C, 68.03, H, 12.13, N, 19.83;
found (%): C, 67.86, H, 12.19, N, 19.78. 1H NMR
(400 MHz, CD3CN) d 3.66 (td, J = 11.8, 4.5 Hz, 2H, H3),
3.21 (AA0 of AA0XX0, J = 8.8 Hz, 2H, H6), 2.76 (td,
J = 11.8, 4.0 Hz, 2H, H1), 2.65 (m, 2H), 2.57 (dq,
J = 12.4, 7.2 Hz, 2H, CHHMe), 2.51 (AA0 of AA0XX0,
3-Et,Me
Calcd. (%) for C15H30N4I2: C, 34.63, H, 5.81, N, 10.77;
found (%): C, 34.33, H, 5.89, N, 10.60. 1H NMR
(400 MHz, D2O) d 4.80 (s, 1H, H6), 4.74 (s, 1H, H6), 4.58
(dt, J = 12.8, 4.0 Hz, 1H, Ha4), 4.51 (dt, J = 12.8, 3.6 Hz,
1H, Ha4), 3.95 (dq, J = 14.2, 7.1 Hz, 1H, CHHMe),
3.89–3.78 (m, 2H, He3), 3.70 (dt, J = 13.6, 3.8 Hz, 1H, Ha3),
3.69 (dq, J = 14.2, 7.1 Hz, 1H, CHHMe), 3.60 (dt,
J = 13.6, 4.0 Hz, 1H, Ha3), 3.41 (s, 3H, Me), 3.38–3.10 (m,
8H, He1, He4, H5a and He5), 2.79 (ddd, J = 12.5, 7.8, 3.0 Hz,
2H, Ha1), 2.51–2.31 (m, 2H, H2a), 2.03–1.90 (m, 2H, He2),
1.46 (t, J = 7.1 Hz, 3H, Me). 13C NMR (100 MHz, D2O) d
77.1, 76.4, 65.6, 60.3, 55.7, 51.6 (92), 50.0, 48.6, 47.1,
46.8, 46.5, 18.9, 18.5, 6.8. The atom labelling is shown in
Scheme 2.
0
J = 8.8 Hz, 2H, H6 ), 2.52–2.38 (m, 6H), 2.34 (m, 2H,
0
H3 ), 2.30 (m, 2H, H1 ), 2.16 (dq, J = 12.4, 6.8 Hz, 2H,
0
0
CHHMe), 1.58–1.41 (m, 2H, H2), 1.41–1.09 (m, 2H, H2 ),
1.00 (t, 6H, Me). 13C NMR (100 MHz, CD3CN) d 59.2,
58.8, 57.9, 55.0, 52.1, 49.0, 29.0, 13.8. The atom labelling
is shown in Scheme 2.
L-Et,Me
Calcd. (%) for C15H32N4: C, 67.11, H, 12.02, N, 20.87;
found (%): C, 67.35, H, 12.21, N, 20.63. 1H NMR
(400 MHz, CD3CN) d 3.79 (td, J = 11.5, 4.6 Hz, 1H, H3),
3.62 (td, J = 11.5, 4.6 Hz, 1H, H3), 3.25–3.18 (m, 1H, H6),
3.13–3.06 (m, 1H, H6), 2.76 (td, J = 12.8, 4.0 Hz, 1H, H1),
Synthesis of L-Et,Et and L-Et,Me
0
2.73–2.29 (m, 16H, H1, H1 9 2, H3 9 2, H4 9 2,
0
0
H4 9 2, H5 9 2, H5 9 2, H6 9 2, CHHMe), 2.16 (s, 3H,
0
0
To a suspension of 3-Et,Et (6.8 g, 0.0127 mol) or 3-Et,Me
(6.6 g, 0.0127 mol) in ethanol (200 mL) was slowly added
NaBH4 (4.82 g, 0.127 mol). The reaction mixture was
stirred at room temperature for 3 days. Excess NaBH4 was
decomposed by the addition of concentrated HCl until pH
\2. Absolute ethanol (400 mL) was then added to the
mixture and the solvents were removed under vacuum,
giving a white solid. This was dissolved in KOH 8 M
(75 mL), and the water phase was extracted with toluene
(5 9 150 mL). The combined organic phases were dried
over sodium sulfate, and the solvent was removed under
vacuum to afford the product as a yellow oil (yield
60–70%).
Me), 2.15 (m, 1H, CHHMe), 1.55–1.44 (m, 2H, H2), 1.42–
1.32 (m, 2H, H2 ), 1.0 (t, 3H, Me). 13C NMR (100 MHz,
0
CD3CN) d 61.7, 59.2, 58.8, 57.9, 57.7, 57.0, 56.8, 55.0,
52.2 (92), 49.1, 43.0, 29.0, 28.7, 13.8. The atom labelling
is shown in Scheme 2.
Synthesis of [MnCl2(L-Et,Et)] [15] and
[MnCl2(L-Et,Me)]
Anhydrous MnCl2 (0.97 g, 0.0077 mol) was dissolved in
dry dimethylacetamide (12 mL) under nitrogen at 100 °C
with stirring. To the solution was added the appropriate
123

Transit Met Chem
ligand (0.0077 mol), and the reaction mixture was stirred at
100 °C for 3 h. The system was cooled, and the white
microcrystalline solid was filtered off and washed with
(1.5 9 Ueq for H atoms of methyl groups). Different
Fourier maps showed disorder of the methyl and ethyl
groups of the ligand that, owing to the synthetic route, can
be attached at N4/N2 or at N2/N4 (refined occupancy
factors 0.77 and 0.23, respectively). Thermal ellipsoid plots
were generated using Ortep-3 [27] integrated in the
WINGX suite of programs. Analysis of structures super-
imposition was performed using the program Mercury [28].
Crystal and refinement data for [MnCl2(L-Et,Me)] are
given in Table 1. CCDC 1483874 contains the supple-
mentary crystallographic data for this paper. These data
can be obtained free of charge from the Cambridge Crys-
tallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
dimethylacetamide
(2 9 10 mL),
diethyl
ether
(5 9 10 mL), and dried under vacuum (yield 80–90%).
[MnCl2(L-Et,Me)]: calcd. (%) for C15H32Cl2MnN4: C,
45.69, H, 8.18, N, 14.21; found (%): C, 45.94, H, 8.28, N,
14.02.
Bleaching tests
Preparation of the solutions: Buffer solutions (A) at con-
stant ionic strength (1 M NaCl) were prepared by dis-
solving NaCl (58.4 g, 1.0 mol) and NaHCO3 (8.4 g, 0.10
moL) in water (1.0 L). The pH was then adjusted to the
desired value by the addition of Na2CO3. A solution (B) of
morin (7.5 mM) was prepared by dissolving morin hydrate Results and discussion
(0.018 g, 0.060 9 10-3 mol) in ethanol (8 mL). Solutions
(C) of the catalysts (0.12 mM) were prepared by dissolving
the complexes in the buffered solutions (A, 50 mL).
Catalytic runs: An aliquot of the catalyst solution
C (500 lL) was diluted in the appropriate buffer solution
A (25 mL), and an aliquot of the morin solution (500 lL)
was added with stirring. The volume was then adjusted to
30 mL by the addition of buffer solution A. An aqueous
solution of H2O2 (25 lL, 60% w/w) was then added. The
initial concentrations were as follows: [cata-
lyst] = 2 9 10–3 mM, [morine] = 0.125 mM, [H2O2]
0.05% w/w. Progress of the reaction was monitored by
following the reduction in the absorption at 396 nm
(e = 1.94 9 104 M-1 cm-1).
Synthesis of the macrocycles
The synthesis of macrocycles L-Et,Et and L-Et,Me is
outlined in Scheme 1. The bridged precursor 1 was
Table 1 Crystal data and structure refinement parameters for
[MnCl2(L-Et,Me)]
Empirical formula
Formula weight
Temperature
C15H32Cl2MnN4
394.29
173(2) K
MoKa
˚
0.71073 A
Radiation
Wavelength
Crystal size
0.18 9 0.13 9 0.05 mm
Monoclinic
X-ray structure of [MnCl2(L-Et,Me)]
Crystal system
Space group
P21/c
Colorless block-shaped single crystals of [MnCl2(L-Et,Me)],
suitable for X-ray analysis, were obtained by slow evapo-
ration of a CH3CN solution at ambient temperature. X-ray
data collection was performed on a Bruker–Nonius Kappa-
CCD diffractometer equipped with graphite monochro-
˚
a = 8.435(3) A
Unit cell dimensions
˚
b = 13.768(2) A
˚
c = 15.587(3) A
b = 93.010(18)°
3
˚
˚
Volume
1807.7(8) A
mated MoKa radiation (k = 0.71073 A). Data were col-
Z
4
lected at 173 K under N2 flow using a Cryostream-700
(Oxford Cryosystems). Unit cell parameters were deter-
mined by least-squares refinement of the h angles of 80
reflections in the range 3.084° \ h \ 21.890°. Data
reduction and semiempirical absorption corrections were
done using EvalCCD [22] and SADABS programs [23],
respectively. The structure was solved by direct methods
(SIR97 program) [24] and refined by the full-matrix least-
squares methods on F2 using the SHELXL-97 program
[25] with the aid of the program WinGX [26]. All non-
hydrogen atoms were refined anisotropically. All H atoms
were stereochemically generated and refined by the riding
model with Uiso = 1.2 9 Ueq of the carrier atom
Calculated density
Absorption coefficient
hmaxhmin
1.449 Mg m-3
1.028 mm-1
27.50°, 3.01°
-10 B h B 10
Limiting indices
-17 B k B 17
-20 B l B 20
Reflns collected/unique
Data/restraints/parameters
Final R indices [I [ 2r(I)]
R indices (all data)
16,114/4069 [R(int) = 0.0753]
4069/0/211
R1 = 0.0498, wR2 = 0.0951
R1 = 0.0994, wR2 = 0.1160
0.739/-0.406
-3
)
˚
Max peak/hole (e A
123

Transit Met Chem
prepared by reaction of commercial cyclam with glyoxal
(step i) as reported in the literature [19].
The yellow mother liquor was found to contain a sub-
stantial amount of the mono-ethylated compound (2-Et), as
disclosed by the NMR spectrum of the crude mixture.
Excess MeI was therefore added, and a new precipitate
could be isolated after 5 days of stirring at RT. This pro-
duct, corresponding to 3-Et,Me, was again characterized
by NMR spectroscopy. In this case (Fig. 1b), the diversity
of the substituents on the nitrogen atoms reflects on the
lack of symmetry of the molecule, and the two axial H4
protons are not equivalent (Fig. 1b).
The iodide salts of type 3 were obtained by sequential
alkylation of 1 with the appropriate alkyl iodides (step ii).
This reaction is fairly regioselective due to the availability
of the lone pairs on the two homotopic exo nitrogens [3].
On the other hand, the two endo nitrogens have lone pairs
which are more sterically concealed on the concave face of
the cleft-like structure [3], and hence less prone to function
as bases.
The 1H, 13C, and 2D COSY NMR spectra of the isolated
product were fully consistent with the C2 symmetry of the
molecule, and a unique signal was observed for the couples
of homotopic protons related by the axis. As an example,
Fig. 1a shows the signal attributed to the axial H4 protons
(for numbering, see Scheme 2 in ‘‘Experimental’’ section),
which appear as double triplets.
The two iodide salts 3-Et,Et and 3-Et,Me were then
reduced to the pro-ligands L with a large excess of NaBH4
in ethanol (steps iv and v). The milky white reaction media
were treated with HCl, and after the initial work-up, the
resulting solid was dissolved in 8 M potassium hydroxide.
This treatment was necessary in order to extract the free
b
Scheme 3 Synthesis of complexes [MnCl2(L-Et,Et)] (R = Me) and
[MnCl2(L-Et,Me)] (R = H)
a
4.60
4.50
4.40
Fig. 1 Signals of the axial H4 protons in the 1H NMR spectra (in
D2O) of 3-Et,Et (a) and 3-Et,Me (b)
b
Fig. 3 ORTEP view of [MnCl2(L-Et,Me)]. Thermal ellipsoids are
˚
drawn at 30% probability level. Selected bond lengths (A) and angles
a
(°): Mn1–N1 2.321(3); Mn1–N2 2.333(3); Mn1–N3 2.325(3); Mn1–
N4 2.337(3); Mn1–Cl1 2.4574(11); Mn1–Cl2 2.4517(11); N2–Mn1–
N4 157.82(10); N1–Mn1–N3 76.14(11); Cl1–Mn1–Cl2 98.50(5).
Only the major part of the disordered alkyl groups is shown for clarity
3.85
3.80
3.75
3.70
3.65
3.60
3.55
Fig. 2 Signals of the axial H3 protons in the 1H NMR spectra (in
CD3CN) of L-Et,Et (a) and L-Et,Me (b)
123

Transit Met Chem
ligands with toluene. These molecules act as proton
sponges, so it is necessary to use high concentrations of
base to ensure their complete deprotonation [3]. At lower
pH, the conjugate acid L-Et,Et-H? was extracted, as
confirmed by the presence of a peak at high frequency in its
1H NMR spectrum.
Both pro-ligands were characterized by NMR spec-
troscopy. Also in this case, the number of signals is clearly
related to the symmetry of the ligands, as illustrated in
Fig. 2 for protons H3.
Synthesis and structures of the complexes
The synthesis of the complexes was carried out by mixing
the ligands and anhydrous MnCl2 in dry dimethylacetamide
under a nitrogen atmosphere (Scheme 3).
Colorless block-shaped single crystals of [MnCl2(L-Et,Me)]
suitable for X-ray analysis were obtained by slow evaporation of
a CH3CN solution at ambient temperature. The complex crys-
tallizes in the monoclinic P21/c space group with one molecule
contained in the asymmetric unit. The molecular structure is
shown in Fig. 3. All of the bond distances fall in the expected
ranges.
In this complex, the ligand is topologically constrained
in a rigid conformation. The crystal structure confirms the
expected geometry already found in other Mn(II) com-
plexes containing this kind of ligand [2, 5, 6, 18]. The Mn
atom is hexa-coordinated and occupies the cavity of the
tetradentate ligand, completing its coordination sphere with
two chlorine atoms in a pseudo-octahedral geometry. The
N atoms of the macrobicyclic ligand occupy two axial and
two cis-equatorial sites of the distorted octahedron, while
Fig. 4 Superimposition of the molecular structure of [MnCl2(L-
Et,Me)] with the literature data for [MnCl2(L-Me,Me)] [2, 5]
(orange) and [MnCl2(L-Et,Et)] [16] (magenta). (Color figure online)
Fig. 5 Activities of each catalyst at different pH (a, MnCl2(L-Me,Me); b, MnCl2(L-Et,Me); c, MnCl2(L-Et,Et))
Fig. 6 Comparison of the activities of the three catalysts at different pH values (a, 8.00; b, 8.75; c, 9.00)
123

Transit Met Chem
Acknowledgements This work was supported by Fater SpA.
the chlorine atoms occupy the two remaining cis-equatorial
sites. Owing to the synthetic route and to the different
substituents at N2 and N4 of the cyclam ligand, Me-/Et-
groups can be attached at N4/N2 or at N2/N4 and a dis-
order in their positions is found in the structure of the
complex. Due to the rigidity of the cyclam ligand, only
minor differences in geometric parameters are found with
respect to similar Mn(II) complexes [2, 5, 18] (Fig. 4). In
particular, the structure of [MnCl2(L-Et,Me)] is isomor-
phous with the analogous complex of L-Me,Me [2].
References
1. Weisman GR, Rogers ME, Wong EH, Jasinski JP, Paight ES
(1990) J Am Chem Soc 112:8604
2. Hubin TJ, McCormick JM, Collinson SR, Alcock NW, Busch DH
(1998) Chem Commun 1675
3. Wong EH, Weisman GR, Hill DC, Reed DP, Rogers ME, Condon
JS, Fagan MA, Calabrese JC, Lam K-C, Guzei IA, Rheingold AL
(2000) J Am Chem Soc 122:10561
4. Hubin TJ, McCormick JM, Collinson SR, Buchalova M, Perkins
CM, Alcock NW, Kahol PK, Raghunathan A, Busch DH (2000) J
Am Chem Soc 122:2512
Catalytic activities
5. Hubin TJ, McCormick JM, Alcock NW, Busch DH (2001) Inorg
Chem 40:435
6. Hubin TJ, McCormick JM, Collinson SR, Alcock NW, Clase HJ,
Busch DH (2003) Inorg Chim Acta 346:76
7. Camus N, Halime Z, Le Bris N, Bernard H, Platas-Iglesias C,
Tripier R (2014) J Org Chem 79:1885
8. Jones DG, Wilson KR, Cannon-Smith DJ, Shircliff AD, Zhang Z,
Chen Z, Prior TJ, Yin G, Hubin TJ (2015) Inorg Chem 54:2221
9. Abdulwahaab BH, Burke BP, Domarkas J, Silversides JD, Prior
TJ, Archibald SJ (2016) J Org Chem 81:890
10. Hubin TJ, Amoyawb PN-A, Roewe KD, Simpson NC, Maples
RD, Carder Freeman TN, Cain AN, Le JG, Archibald SJ, Khan
SI, Tekwani BL, Khan MOF (2014) Bioorg Med Chem 22:3239
11. Busch DH, Collinson SR, Hubin TJ (1998) WO 98/39098
12. Hiler GD, Perkins CM (1998) WO 98/39335
13. Hiler GD, Perkins CM (2000) WO 00/32601
14. Perkins CM, Kitko DJ (2002) WO 02/26267
15. Reinhardt G, Janitschek W, Ladwig M (2012) WO 2012/107187
Al
16. Dykstra RR, Tremblay ME, Wang XJ, Danziger JL, Ditullio DD
Jr, Kong C, Cotte-Rodriguez, I (2012) US 20120208739 A1
20120816
17. Dykstra, RR, Ditullio DD Jr, Tremblay ME, Gustwiller ME
(2012) US 20120205581 A1 20120816
The catalytic activities of the three Mn(II) complexes
[MnCl2(L-Et,Et)], [MnCl2(L-Et,Me)], and [MnCl2(L-Me,
Me)] for bleaching of morine were compared in buffered
aqueous solutions at pH 8.0, 8.75, and 9.0, using hydrogen
peroxide as the oxidant. The flavonol morine was chosen
for these experiments, since it is present in fruit and veg-
etables and is a target in the bleaching of laundry [29]. The
concentrations used for the experiments were inspired by
those conceivably acting during laundry processes, that is,
\1 ppm of catalyst and 500 ppm of oxidant. The sub-
strate(morine)/catalyst ratio was set at 60:1. The progress
of the reaction was monitored by following the maximum
of absorption at 396 nm (e = 1.94 9 104 M-1cm-1).
The activities of the three catalysts all depend on pH, but the
trends are not the same. Thus, a clear improvement with
increasing alkalinity was observed only for [MnCl2(L-Me,Me)]
(Fig. 5a), while the differences are more subtle for
[MnCl2(L-Et,Me)] and [MnCl2(L-Et,Et)] (Fig. 5b, c).
Overall, the dimethyl complex is the most active, particu-
larly at higher values of pH (Fig. 6). These results can be
interpreted in light of previous studies [30], which revealed
that mononuclear species are active at low pH values, and
dinuclear at higher values. It is plausible that this association
is favored only for the unhindered dimethyl derivative, and
inhibited for the other more sterically crowded complexes.
18. Yin G, Danby AM, Day V, Baksi Roy S, Carter J, Sheper WM,
Busch DH (2011) J Coord Chem 64:4
19. Xu A, Xiong H, Yin G (2009) J Phys Chem A 113:12243
20. Yin G, Baksi Roy S, Danby AM, Day V, Carter J, Scheper WM,
Busch DH (2011) J Incl Phenom Macrocycl Chem 71:311
21. Weisman GR, Ho SCH, Johnson V (1980) Tetrahedron Lett
21:335
22. Duisenberg AJM, Kroon-Batenburg LMJ, Schreurs AMM (2003)
J Appl Cryst 36:220
23. Bruker-Nonius SADABS (2002) Bruker-Nonius, Delft
24. Altomare A, Burla MC, Camalli M, Cascarano GL, Giacovazzo
C, Guagliardi A, Moliterni GG, Polidori G, Spagna R (1999) J
Appl Cryst 32:115
Conclusion
This work fills a gap in the literature related to macrocyclic
ligands derived from cyclam. We have reported the syn-
thesis and characterization of two glyoxal-bridged ligands,
whose Mn(II) complexes have been described extensively
in the patent literature for their excellent bleaching activity.
The X-ray crystal structure of one complex is also descri-
bed in comparison with closely related compounds. Fur-
thermore, their bleaching activities have been compared in
a benchmark test, revealing that pH has a different effect
on the three catalysts, and that the dimethyl derivative is by
far the most active.
25. Sheldrick GM (2008) Acta Cryst A64:112
26. Farrugia LJ (1999) J Appl Cryst 32:837
27. Farrugia LJ (1997) J Appl Cryst 30:565
28. Macrae CF, Bruno IJ, Chisholm JA, Edgington PR, McCabe P,
Pidcock E, Rodriguez-Monge L, Taylor R, van de Streek J, Wood
PA (2008) J Appl Crystallogr 41:466
29. Dannacher JJ (2006) J Mol Catal A Chem 251:159
30. Hage R, Iburg JE, Kerschner J, Koek JH, Lempers ELM, Martens
RJ, Racherla US, Russell SW, Swarthoff T, van Vliet MRP,
Varnaar JB, van der Wolf L, Krijnen B (1994) Nat Lett 369:637
123