Synthesis, spectra and crystal structure of a novel 18-metallacrown-6 [Mn6(4-ohashz)6(CH3OH)6] · 12CH3OH

Article abstract of DOI:10.1016/j.inoche.2004.12.007

A new macrocyclic manganese(III) 18-azametallacrown-6 compound with the formula of [Mn₆(4-ohashz)₆(CH₃OH)₆] · 12CH₃OH (4-ohashz = N-acetyl-(4-hydroxysalicylhydrazidate)) was synthesized and characterized. In this complex, the metal ion is forcing the stereochemistry of the ligands arranged into a propeller shape with alternating Λ/Δ configurations. The disc-shaped hexanuclear complex has a cavity in the center with a dimension of 8.69′ in diameter and 3.13′ in thickness and aligned approximately along the crystallographic c-axis, one-dimensional channels are formed.

Full text of DOI:10.1016/j.inoche.2004.12.007

Inorganic Chemistry Communications 8 (2005) 216–218
www.elsevier.com/locate/inoche
Synthesis, spectra and crystal structure of a novel
18-metallacrown-6 [Mn6(4-ohashz)6(CH3OH)6] Æ 12CH3OH
*
Bo Li, Dong-Dong Han, Gong-Zhen Cheng, Zhen-Ping Ji
College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, PR China
State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing, Jiangsu 210093, PR China
Received 15 November 2004; accepted 4 December 2004
Abstract
A new macrocyclic manganese(III) 18-azametallacrown-6 compound with the formula of [Mn6(4-ohashz)6(CH3OH)6] Æ 12-
CH3OH (4-ohashz = N-acetyl-(4-hydroxysalicylhydrazidate)) was synthesized and characterized. In this complex, the metal ion is
forcing the stereochemistry of the ligands arranged into a propeller shape with alternating K/D configurations. The disc-shaped
hexanuclear complex has a cavity in the center with a dimension of 8.690 in diameter and 3.130 in thickness and aligned approxi-
mately along the crystallographic c-axis, one-dimensional channels are formed.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Metallacrown; Manganese complex; Crystal structure
Metallacrown and its analogies, as the first of a new
class of molecule known as metallamacrocycles, have at-
tracted considerable attention on supramolecular chem-
istry, self-assembly, host–guest chemistry and molecular
recognition since the first report [1]. There are two types
of metallacrown molecules. The first type has a cyclic
structure with interlinked [M–N–O]n repeat unit as 9-
metallacrown-3 [1,2], 12-metallacrown-4 [3,5–8], 15-
metallacrown-5 [4,5], one or two metal ions could be
coordinated in the center of the ring. Another type of
metallacrown has a [M–N–N]n repeat unit, forming
18-metallacrown-6 [9–11], 24-metallacrown-8 [12] and
30-metallacrown-10 [13]. In this type of metallacrown,
nitrogen atoms replace all oxygen atoms in the cyclic
structure, while there is no central metal ion in the center
of the ring structure. One, two or three dimensions of
networks of metallacrown could be connected via facial
interactions and anion bridging [14].
In the present communication, we report the synthesis,
characterization and crystal structure of the manganese
18-metallacrown-6. The ligand N-acetyl-(4-hydrox-
ysalicylhydrazide) [15] (1) (H34-ohashz, Scheme 1) was
synthesized by reacting 4-hydroxy-salicylhydrazide
(1.68, 10 mmol) with acetic anhydride (1.13 g, 12 mmol)
in 30 ml of chloroform at 0 °C, then slowly warmed to
room temperature and stirred for 2 h. The resulting white
precipitate was filtered and rinsed with chloroform and
diethyl ether.
H34-ohashz (0.105 g, 0.5 mmol) was dissolved in 20
ml methanol, manganese(II) acetate tetrahydrate
(0.1235 g, 1.0 mmol) in 20 ml methanol was added
and stirred. Dark brown rectangular crystals of
[Mn6(4-ohashz)6(CH3OH)6] Æ 12CH3OH] (2) [16] were
obtained after slow evaporation.
In the IR spectra of the complex the band of C@O
is shifted to lower frequencies comparing with the li-
gand suggesting the coordination of carbonyl oxygen
atom to the metal ion. The stretching vibration band
d (N–H) are significantly weakened in the spectra of
the complex indicating the deprotonation of the group
*
Corresponding author. Tel.: +86 2787218274; fax: +86
2787647617.
E-mail address: jizp@chem.whu.edu.cn (Z. Ji).
1387-7003/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2004.12.007

B. Li et al. / Inorganic Chemistry Communications 8 (2005) 216–218
217
˚
A for the van der Waals radius of manganese), and
˚
approximately 3.13 A in depth. All manganese atoms
O
OH
O
O
Mn
in the title compound are in a distorted octahedral
Mn(ONO)(NO)(O) environment. The typical Jahn–
Teller elongation along the z-axis was observed be-
cause of the high-spin d4 manganese(III) ion. The
average axial bond distance (the average values of
N
O
O
N
H
N
Mn
HO
N
H
HO
˚
Mn1–O1 and Mn1–N1 bond distances: 2.260 A) is
Scheme 1. Ligand H34-ohashz and basic binding sites in the complex.
˚
about 0.345 A longer than the average equatorial
bond distance (the average value of Mn1–O2, Mn1–
˚
O3, Mn1–O4 and Mn1–N2 bond distances: 1.915 A).
and coordination of the hydrazide nitrogen atom to the
metal ion. The bands of C–N at 1266 and 1331 cmꢀ1
are shifted to 1519 cmꢀ1 due to the deprotonation of
NH group.
The ligands are arranged into propeller shape with
altering K/D stereochemistry as DKD or KDK configu-
rations [18].
There are intramolecular and intermolecular hydro-
gen bonds in the title compound. They are between
the O–H of coordinated methanol molecules and the
oxygen atoms of solvent methanol molecules, and be-
tween the O–H of solvent methanol molecules and phe-
nol oxygen atoms.
The structural representation of the title metalla-
crown molecule [17] is shown in Fig. 1, six Mn(III)
ions and six N-acetyl-4-hydroxysalicyhydrazide(4-
ohashz3ꢀ) ligands construct a planar 18-membered
ring which forms the manganese metallacrown core.
The average neighboring Mn–Mn interatomic
˚
The crystal packing structure of the complex shows
that the disc-shaped hexanuclear clusters are aligned
approximately along the crystallographic c-axis. The
cavities of the clusters in the crystal structure are also
aligned, and one-dimensional channels are formed,
shown in Fig. 2. These channels could contain molecules
with certain dimensions [11].
distances is 4.8558 A. The average Mn–Mn–Mn inter-
atomic angles is 112.963°. The approximate dimension
of the oval-shaped cavity in the molecule of the title
compound, measured between the opposite carbon
atoms (C10–C10E, less 0.77 A for the van der Waals
˚
radius of carbon), is 3.44 A at the entrance, about
˚
˚
8.69 A at its largest diameter (Mn1–Mn1E, less 0.60
Fig. 1. Molecular structure of the title compound with atom labeling. H atoms are omitted for clarity.

218
B. Li et al. / Inorganic Chemistry Communications 8 (2005) 216–218
References
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1595 (2002).
Fig. 2. Perspective view of [Mn6(4-ohashz)6(CH3OH)6] Æ 12CH3OH
along the c-axis. H atoms are omitted for clarity.
[12] C. Dendrinou-Samara, M.C. Zaleski, A. Evagorou, J.W. Kampf,
V.L. Pecoraro, D.P. Kessissoglou, Chem. Commun. 2668 (2003).
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Acknowledgement
[15] H34-ohashz: Anal. Calcd. C9H10N2O4 requires: C, 51.42; H, 5.01;
N, 13.32; Found: 50.98; H, 4.65; N, 13.13%. IR (cmꢀ1, KBr):
m = 3070, 1680, 1648, 1547, 1331, 1226. 1H NMR (DMSO-d6,
ppm) d: 12.176; 10.242; 10.184–9.993 (s, 3H, Hs of amides and
phenolic OH); 7.708–6.259 (br s, 3H at phenyl); 1.893(t, 3H at –
CH3).
We are grateful to the National Natural Science
Foundation of China for the financial support (Grant
No. 20171035).
[16] Mn6(4-ohashz)6(CH3OH)6] Æ 12CH3OH: crystal of compound 2 is
air-sensitive and loses its solvents of crystallization within 1 min
IR (cmꢀ1, KBr): m = 1640, 1612, 1070.
Appendix A. Supplementary material
[17] Crystal
data
C72H108Mn6N12O42
for
,
[Mn6(4-hashz)6(CH3OH)6] Æ 12CH3OH:
Crystallographic data for the structural analysis
have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC reference numbers
240166 for compound 2. Copies of this information
may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(Fax: +44 1223 336 033; e-mail: deposit@ccdc.cam.a-
c.uk or www.ccdc.cam.ac.uk).
ꢀ
M = 2143.34, trigonal, space group R3,
3
˚
˚
a = 30.217(2), c = 9.322(1) A, c = 120.00°, V = 7371.3(10) A ,
Z = 3, Dc = 1.449 g/cm3, F(000) = 3330, l = 0.839 mmꢀ1, 12238
observed reflections, 2869 independent reflections Rint = 0.0918.
The final agreement factors are R1 = 0.0373, wR2 = 0.0804 with
I > 2r(I).
[18] The K/D stereochemistry was defined using a skew line convention
for the six-coordinated complexes based on the octahedron as
described in Inorg. Chem. 1 (1970) 9.