Synthesis and crystal structure of some macrocyclic ring compounds

Article abstract of DOI:10.1080/00397911.2010.481752

A bola-shaped diester-dicarboxylic acid (L1H₂) synthesized with ethanediol spacer and phthalic anhydride head group is demonstrated to form various macrocyclic ring compounds such as M₁, M₂, and M₃. Compound M₁, containing both lactam [-C(=O)-N-H)] and lactone [-C(=O)-O-] functional groups, has a [16]-membered macrocyclic ring, while compound M₂, composed of only lactones [-C(=O)-O-], exists with a [19]-membered macrocyclic ring. Similarly, compound M₃, composed of Cu(II) metal ions, exists with a macrocycle-like [15]-membered chelate ring. In addition to the ₁H NMR spectra, the single crystals obtained for M₁ and M₃ thoroughly established, the formation of the ring structures. This article demonstrates the versatile capability of diester-dicarboxylic acid for forming various types of ring compounds, such as bis-chelate rings in M₃ and lactam cum lactone-type macrocyclic rings in M₁ and M₂.

Full text of DOI:10.1080/00397911.2010.481752

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Synthesis and Crystal Structure of Some
Macrocyclic Ring Compounds
Paulraj Mosae Selvakumar a , Neha Carpenter a , Eringathodi Suresh a
& Palani Sivagnana Subramanian a
a Analytical Science Division, Central Salt and Marine Chemicals
Research Institute (CSIR) , Bhavnagar , Gujarat , India
Published online: 30 Mar 2011.
To cite this article: Paulraj Mosae Selvakumar , Neha Carpenter , Eringathodi Suresh & Palani
Sivagnana Subramanian (2011) Synthesis and Crystal Structure of Some Macrocyclic Ring Compounds,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 41:9, 1309-1319, DOI: 10.1080/00397911.2010.481752
To link to this article: http://dx.doi.org/10.1080/00397911.2010.481752
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Synthetic Communications1, 41: 1309–1319, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.481752
SYNTHESIS AND CRYSTAL STRUCTURE OF SOME
MACROCYCLIC RING COMPOUNDS
Paulraj Mosae Selvakumar, Neha Carpenter,
Eringathodi Suresh, and Palani Sivagnana Subramanian
Analytical Science Division, Central Salt and Marine Chemicals Research
Institute (CSIR), Bhavnagar, Gujarat, India
GRAPHICAL ABSTRACT
Abstract A bola-shaped diester–dicarboxylic acid (L1H2) synthesized with ethanediol
spacer and phthalic anhydride head group is demonstrated to form various macrocyclic ring
compounds such as M1, M2, and M3. Compound M1, containing both lactam [-C(¼O)-N-
H)] and lactone [-C(¼O)-O-] functional groups, has a [16]-membered macrocyclic ring,
while compound M2, composed of only lactones [-C(¼O)-O-], exists with
a
[19]-membered macrocyclic ring. Similarly, compound M3, composed of Cu(II) metal
ions, exists with a macrocycle-like [15]-membered chelate ring. In addition to the 1H
NMR spectra, the single crystals obtained for M1 and M3 thoroughly established, the for-
mation of the ring structures. This article demonstrates the versatile capability of
diester-dicarboxylic acid for forming various types of ring compounds, such as bis-chelate
rings in M3 and lactam cum lactone-type macrocyclic rings in M1 and M2.
Keywords Bis-chelate; carboxylic acid; lactam; lactone; macrocycles; Steglich reaction
Received December 10, 2009.
Address correspondence to Palani Sivagnana Subramanian, Analytical Science Division, Central
Salt and Marine Chemicals Research Institute (CSIR), Gijubhai Badheka Marg, Bhavnagar 364002,
Gujarat, India. E-mail: siva@csmcri.org
1309

1310
P. M. SELVAKUMAR ET AL.
INTRODUCTION
Macrocyclic compounds possessing varieties of ring size are well recognized for
their potential applications in host–guest chemistry[1] and as sensors for many metal
ion and anion recognition, etc. Ever since the discovery of crown ether by Pedersen,[2]
an extensive literature on the synthesis of macrocyclic compounds possessing a var-
iety of ring sizes with various functional groups that have diverse uses are evidence
of its importance. Lactones are cyclic esters, which can be obtained upon conden-
sation of an alcoholic OH with carboxylic COOH group. Similarly, nitrogen analogs
and sulfur analogs of lactones, having the carboxamide or sulfoxamide group (i.e., -
CO-NH- or SO-NH) as a part of a ring or ring system are named lactams[3] and sul-
tams,[4] respectively. Among these, the lactams possesses significant biological impor-
tance. Several compounds of many antibiotic families such as penicillins,[5]
madumycin,[6] streptogramin,[7] trienomycin,[8] and iejimalides[9] have emerged as
highly potent antibiotics. In this regard, compounds possessing both lactam and lac-
tones have gained significant importance because of their potential antibiotic nature.
Hence, the synthesis of macrocyclic lactones gains significant importance, and the
synthetic methods generally involve the reaction of dicesium salts of acids with dibro-
mides,[10] reaction of acid chlorides with glycols,[11] condensation of dipotassium salt
of acid with dibromides,[12] condensation of dicarboxylic acids with benzyl bro-
mides,[13] reaction of acid chlorides with x-bromo alcohols,[14] condensation of diacid
chlorides with diols under phase-transfer catalysis,[15] cyclization of sulfonium salts in
the presence of cesium carbonate,[16] and the reaction assisted by alkaline metals.[17]
In this direction, the synthetic strategy of desymmetrization of anhydrides using
diol[18] has gained significant importance in the synthesis of macrocyclic tetralactones
and dilactones because of its simplified procedure and good yield. Thus, there are
many reports that explore lactam- or lactone-based macrocycles.
We recently have undertaken research that involves synthesis of novel dicar-
boxylic compounds constituting various functional groups such as N and S in
addition to COOH and are currently involved in exploring their application in
material and biological chemistry. In this endeavor, we have already synthesized a
huge number of diester–dicarboxylic acids and a few such diester–dicarboxylic acids
recently demonstrated their tubular formation.[19a] In the present article, in addition
to reporting the synthesis of lactam=lactone-based macrocyclic ring, we further
explore the synthesis of one such representative dicarboxylic acid and its versatile
capability for the synthesis of various macrocycles and macrocycle-like bis-chelate
rings. Accordingly, we report three ring compounds (M1, M2, and M3) that differ
by their ring components. While the ring in the M2 exists with the lactone functional
group, the compound M1 is derived with both lactone and lactam functional groups.
Similar to various ring compounds, metallomacrocycles deserve significant
importance because of their potential applications in varieties of interdisciplinary
research. Macrocycles, possessing a cyclic ring and a metal active site, are impor-
tant[20] because of their bifunctional role in host–guest chemistry and catalysis.
The macrocycle-like bis-chelate Cu(II) compound, M3, reported possesses both these
potential characteristics (i.e., cavity and metal site) which creates some special inter-
est. With this in mind, we recently reported the formation of various bis-chelate ring
compounds with 15 to 19-members.[21] In the present investigation, we report the

MACROCYCLIC RING COMPOUNDS
1311
synthesis of the macrocycle-like Cu(II) bis-chelate rings derived from bola-shaped
diester–dicarboxylic acid in addition to the lactam=lactone ring compounds. The
structures of these compounds are established by electrospray ionization–mass spec-
trometry (ESI-MS), infrared (IR), and NMR spectroscopic methods in addition to
single crystal x-ray structure, wherever applicable.
RESULTS AND DISCUSSION
The Steglich reaction,[22,23] influenced by DCC (dicyclohexyl-carbodiimide, as
dehydrating agent) and DMAP (dimethylaminopyridine as catalyst), is known to
provide dilactone-based compounds. Though there are significant numbers of
macrocycles available in the literature with lactone [-C(¼O)-O-]–based rings, the lac-
tam [-C(¼O)-N-H)]–based macrocycles are rare in the literature. With an aim to syn-
thesize the macrocyclic compound possessing both lactone and lactam functional
groups, we have adapted the Steglich reaction condition in the present synthesis.
Accordingly, the bola-shaped diester–dicarboxylic precursor compound (L1H2)[19]
was obtained by desymmetrizing phthalic anhydride using ethanediol.[19,23]
Scheme 1 represents the various synthetic strategies adapted for the formation
of three different cyclic compounds, M1, M2 and M3, using this L1H2. Treating
L1H2 and diol as well as adapting DCC and DMAP gave the compound M2 per
the Steghlich reaction. Similarly, the precursor diester–dicarboxylic acid L1H2 was
treated with diethanolamine in place of diethyleneglygol and expected to form M4.
Under this condition, interestingly we repeatedly ended up with only M1 and not
M4. The compounds M1 and M2 were synthesized with [16]- and [19]-membered
macrocyclic rings, while the complex M3 (i.e., [Cu2L2(S)2] where S ¼ methanol)
Scheme 1. Synthesis of macrocyclic compounds M1, M2, M3, and M4.

1312
P. M. SELVAKUMAR ET AL.
was obtained upon reacting L1H2 and cupric acetate, which bears [15]-member bis-
chelate ring.
In general, the synthesis of macrocycles with lactones were performed by treat-
ing the diol and anhydride in the presence of DCC and DMAP. In our attempt to
understand the formation of M1 instead of M4, we propose the mechanism shown
in Scheme 2. The DCC attacks both the COOH groups of L1H2 equally and removes
two water molecules from each terminal carboxylic group, mediated through di-o-
acylurea intermediate formation, as well as removes DHU (dicyclohexylurea) as
indicated in Scheme 2. However, while using diethanolamine, which bears one NH
group at its center and two terminal OH groups, the reaction takes place between
the central NH group of diethanolamine and the OH group of the diethanolamine
followed by ester-type condensation at any one of the terminal COOH and OH
groups of the carboxylic acid and alcohol. However, the reaction is supposed to
undergo a similar diol-like condensation reaction. Interestingly, instead of the con-
densation process taking place at the terminal COOH group, it actually takes place
with one COOH and the middle NH group, leaving the other terminal OH group
unaltered. This experiment indicates that DCC and DMAP are an efficient dehydrat-
ing agent and strong nucleophile, respectively, in the case of NH even in the presence
of the COOH group. The mechanism proposed in Scheme 2 clearly states that the
secondary amine in the diethanolamine seems more reactive than its terminal
hydroxyl group. In this attempt, as shown in Scheme 1, the experiments (i) and
(iv) conducted without DMAP were unsuccessful in eliciting any useful product.
Similar to M1 and M2, the chelate ring in the Cu(II)-complex (M3) was also obtained
Scheme 2. Proposed mechanism for M1.

MACROCYCLIC RING COMPOUNDS
1313
on the same diester–dicarboxylic acid upon treatment with 1:1 Cu(II)salt and L1H2
by dissolving in methanol.
As stated previously, replacing the diol by diethanolamine in our synthetic
approach changed the size of the rings of the compounds M1 and M4, though they
possessed similar chemical components. The former compound has a [16]-membered
macrocycle, and the latter compound M4 has a [19]-membered, comparatively larger
macrocyclic ring. In our attempt, we could successfully isolate the [16]-membered
macrocyclic ring M1, whereas the [19]-membered macrocyclic ring M4 failed to form.
1
1
Both these compounds M1 and M2 were characterized by H NMR. The H
NMR of compound M1 provides two set of multiplets with respect to the number
of hydrogens in the aromatic and aliphatic regions. The aromatic region, attributable
to d7 to 8.5, corresponded to eight hydrogens while the aliphatic region d3 to 5 cor-
responded to 12 hydrogens, matching well with the structure obtained from a single
crystal. The broad feature observed at around 2.0d can be attributed to the NH
1
hydrogen of diethanolamine. Similarly to M1, the H NMR spectra (S6) recorded
for compound M2 also provides multiple peaks at aromatic regions corresponding
to d7.4–7.8, matching with 8H, representing the phthalyl hydrogens. The three
well-resolved peaks obtained at aliphatic regions 3.79, 4.48, and 4.61d with integral
ratio 4H, 4H, and 4H are attributed to the ethane and diethylene spacer moiety. To
1
further confirm the compound, the H-1H correlation spectroscopy (COSY) 45ꢀ
NMR spectra of M2 was recorded in CDCl3 (S9), which establishes the connectivity
within the molecule. Among the three 1H resonances at the aliphatic region, two sig-
nals at d4.48, 3.79 belonging to diethyleneglycol shows cross peaks, while the other
ethane spacer gives singlet at d4.61 indicating a separate block because of the
absence of any connectivity.
Single Crystal X-Ray Structures
As shown in Scheme 1, the multidentate ligand L1H2 was already demon-
strated for formation of oxygen-based tetralactone-type compound.[23a] However,
there are no reports for the formation of both oxo- and nitrogen-based tetralac-
tone-type macrocycles in the literature. This report illustrates the formation of inter-
esting macrocycles, in which oxygen and nitrogen are present in framing the ring
system. We are successfully able to get the crystal structure for M1. The respective
ORTEP diagram with atom numbering scheme is shown in Fig. 1. The structure
of M1 consists of a [16]-membered macrocyclic ring with three lactone (-OCO-)
=
and one lactam (O C-N-) moieties as ring-constructing components. The phenyl
rings are oriented perpendicular to each other. The O8A oxygen of the pendant
OH group attached with the ethylenic collar shows some unusual distortion because
of its strong flexibility.
Two equivalents of diester dicarboxylic acid L1H2, treated with cupric acetate,
resulted in a pale blue bis-chelate complex M3. ORTEP diagram of the dimeric
Cu(II) bis-chelate complex M3, with deprotonated L1H2 is depicted in Fig. 2. Two
symmetrically disposed ligand moieties are involved in the coordination through
both the oxygen atoms of the carboxylic acid with the metal centers in generating
‘‘paddle-wheel’’ type dimeric Cu2 complex. The detailed bond distance and bond
angles are given in S12. The molecule possesses a center of symmetry located at

1314
P. M. SELVAKUMAR ET AL.
Figure 1. ORTEP diagram of the macrocyclic compound with the atom numbering scheme (30% prob-
ability factor for the thermal ellipsoids; only one site for the disordered N-ethyl alcohol and ketonic oxy-
gen O5 is shown in the figure for clarity).
˚
the midpoint of the Cu1 . . . Cu1a axis, which is 2.6438(13) A long. The symmetrically
disposed ligand moieties generates two [15]-membered chelate rings on both sides of
the Cu-Cu axis. Each metal center in the dimeric unit has square-pyramidal coordi-
nation with the square base provided by the oxygen atoms of the carboxylic acid.
The symmetry-related ligands moieties are oriented to make effective coordi-
nation by utilizing the terminal carboxylic oxygen’s O1 and O2, O7 and O8 in syn
mode with the adjacent Cu(II) metals of the dimeric unit, making a slightly distorted
square base. The average Cu . . . O distance of the carboxylic acid oxygen is 1.954(4)
ꢀ
ꢀ
˚
A, and the square base cis angles ranges from 87.08(17) to 91.49(17) , whereas the
trans angles shows considerable deviation [<O(8)–Cu(1)–O(1) ¼ 168.76(16)ꢀ, O(2)–
Cu(1)–O(7) ¼ 167.21(17)ꢀ] from ideal value for the square planar arrangement.
Figure 2. ORTEP diagram with atom numbering scheme (30% probability factor for the thermal ellip-
soids) for M3, [Cu(L1) ꢁ CH3OH]2.

MACROCYCLIC RING COMPOUNDS
1315
This may be due to the Cu . . . Cu interaction within the dimeric unit, and the paddle
wheel–type coordination of the carboxylate oxygen with the metal center. The longer
apical coordination is provided by the oxygen atom O9 of the methanol molecule at
˚
a distance of Cu(1)–O(9) ¼ 2.129(4) A. The carboxylate oxygens of the Cu(II) square
˚
base is almost in the same plane with the Cu(II) atom sitting at 0.165 A above this
plane to make longer apical coordination with the methanol molecule.
In conclusion, we have synthesized three different macrocyclic ring com-
pounds, using simple L1H2 diacid. The synthesis of compound M1 with a lactam
cum lactone–based macrocyclic ring, M2 with only a lactone ring, and compound
M3 with bis-chelate ring are established unequivocally. The single-crystal x-ray struc-
ture establishes the formation of [16]- and [15]-membered rings in compounds M1
and M3 respectively along with the formation of [19]-membered M2. Anhydrides
are used generally for synthesizing such macrocyclic compounds. The incorporation
of diethanolamine in place of diol in the present synthetic route indicates that
although the OH and NH are competitive, the NH predominates in framing the
macrocyclic ring. The single-crystal x-ray structure confirms the formation of macro-
cyclic and chelate rings in M1 and M3. In the diester–dicarboxylic acid, a multiden-
tate ligand, the flexible spacer successfully forms a paddle-wheel dinuclear Cu2
complex upon incorporating the Cu(II) metal ion and demonstrates the formation
of an important bis-chelate ring. The formation of the macrocyclic ring in M1 and
M2 and the formation of the bis-chelate ring in M3 thus provide the versatile capa-
bility of the simple diester–dicarboxylic acid L1H2.
EXPERIMENTAL
Instrumentation
All reagents were of commercial quality (Aldrich) and were used as received.
Solvents were dried and purified using standard techniques. Reactions were moni-
tored by thin-layer chromatography (TLC) on silica and all reactions were carried
out under an atmosphere of N2. IR spectra were recorded using KBr pellets on a
Perkin–Elmer Spectrum GX Fourier transform (FT)–IR spectrometer. High-
resolution mass analyses were performed using positive ESI technique on a Water
QTof–micromass spectrometer. Elemental analytical data were recorded on a
1
Perkin-Elmer 4100 elemental analyzer. H and 13C NMR spectra were recorded
(500.13 MHz and 125.76 MHz respectively) on a Bruker Advance DPX 500 NMR
1
spectrometer using methanol-d4 or CDCl3. All H NMR spectra were calibrated
with respect to tetramethylsilane (TMS), and TMS was used as an internal reference
for solvents such as CDCl3 and CD3OD.
Synthesis of L1H2, M1, M2, and M3
L1H2. An oven-dried, round-bottom flask under nitrogen gas was charged
with phthalic anhydride (5.92 g, 0.04 mol) and ethane 1,2-diol (1.11 ml, 0.02 mol),
in dry dichloromethane (DCM) and stirred constantly. The reaction mixture was
then cooled to 0 ꢀC, and 3 equivalents of 0.06 mol of triethylamine (TEA) were
added. The reaction was continued for 4 h at 0 ꢀC and further at room temperature

1316
P. M. SELVAKUMAR ET AL.
for 5 h. The reaction was monitored by TLC. After all the anhydride was reacted, the
solvent was evaporated. The residue was cooled to 0 ꢀC, and 200 ml of saturated
sodium bicarbonate solution were added and extracted with dietylether. The aque-
ous layer was cooled to 0 ꢀC and acidified with dilute hydrochloric acid followed
by the extraction with DCM (4 ꢂ 100 ml). The entire organic layers were combined
and evaporated under reduced pressure to provide the corresponding pure dicar-
boxylic acid as white precipitate, which was filtered, washed by water thoroughly,
and dried. Yield (75%). Elemental analysis (%) calcd for C18H14O8: calc. (found)
C, 60.33 (60.65); H, 3.93 (4.10). ES-MS: calc. for C18H14O8Na (M þ Na)þ, 381.06;
1
found: 381.12. H NMR (CD3OD, d, TMS, 200.16 MHz): 7.66 (m, Ar, 2H), 7.62
(m, 2H), 7.58 (m, 4H), 4.60 (-CH2,4H). 13C NMR [CD3OD, d, TMS, 50.3 MHz]:
=
=
169.58 (C O), 168.86 (C O), 132.36, 132.01 (quat-C), 131.37, 131.05, 129.04,
128.53 (¼CH), 63 (-CH2). IR spectra: (n, cmꢃ1): nCOO ¼ 3400–3100 (br), 3020,
2970, 1723, 1694, 1419, 1315, 1290, 1127, 970, 744.
M1. L1H2 (3.58 g, 0.01 mol), diethanolamine (0.9581 ml, 0.01 mol), dicyclohex-
ylcarbodiimide (DCC) (4.12 g, 0.02 mol), and a catalytic amount of DMAP are used
to prepare M1 as per this procedure. The product was purified through column chro-
matography filled with silica gel as the stationary phase and acetonitrile as the
mobile phase. Yield (45%). Elemental analysis calcd. for C22H21O8N: calc. (found)
C, 61.82 (61.02); H, 4.95 (5.00); N, 3.28 (3.20). ES-MS: calc. for C22H21O8N
(Mþ), 427.13; found: 427.93. 1H NMR (CDCl3, d, TMS, 500.13 MHz):
8.204–7.311 (m, Ar, 8H), 4.785–3.286 (-CH2,12H), 2.5–1.6 (br, OH). 13C NMR
=
=
=
(CDCl3, d, TMS, 125.75 MHz]: 172.123 (C O), 168.641 (C O), 166.69 (C O),
=
165.72 (C O), 137.40, 133.34, 133.29 (quat-C), 132.69, 132.60, 131.99, 131.16,
131.10, 129.64, 128.92, 128.64, 128.50, 127.44, 127.27, 127.18 (¼CH), 66.12
(-CH2), 65.76 (-CH2), 64.42 (-CH2), 64.02 (-CH2), 62.16 (-CH2), 60.37 (-CH2),
51.09 (-CH2), 48.76 (-CH2). IR spectra: (n, cmꢃ1): 3500–3200 (br-OH), 3062, 2952,
=
1724 (st, C O), 1622, 1496, 1444, 1428, 1368, 1279, 1135 (C-O), 1076, 1041, 748.
M2. L1H2 (3.58 g, 0.01 mol), diethyleneglygol (0.948 ml, 0.01 mol),
dicyclohexyl-carbodilimide (DCC) (4.12 g, 0.02 mol), and a small amount of DMAP
were used to prepare M2 as per this procedure. The product was purified through
column chromatography filled with silica gel as the stationary phase and acetonitrile
as the mobile phase as described previously. Yield (60%). Elemantal analysis (%)
calcd. for C22H21O9: calc. (found) C, 61.54 (61.42); H, 4.93 (4.81). ES-MS: calc.
for C22H21O9 (M þ 1)þ, 429; found: 429.01. 1H NMR (CDCl3, d, TMS,
500.13 MHz): 7.756–7.736 (m, Ar, 2H), 7.723–7.705 (m, 2H), 7.558–7.516 (m, 4H),
4.613 (-CH2,4H), 4.483–4.466 (-CH2,4H), 3.801–3.784 (-CH2,4H). 13C NMR
=
=
(CDCl3, d, TMS, 125.75 MHz): 167.934 (C O), 167.174 (C O), 132.198 (quat-C),
131.420, 131.307, 131.138, 129.274, 129.110 (¼CH-aromatic), 68.896 (-CH2),
65.107 (-CH2), 62.772 (-CH2). IR spectra: (n, cmꢃ1) nCOO ¼ 3038, 2929, 2852,
1731, 1626, 1576, 1443, 1281, 1117, 1047, 743.
M3[Cu(L1) ꢁ CH3OH]2. The methanolic solution of [Cu(CH3COO)2] ꢁ H2O
(0.398 g, 0.002 mol) and L1H2 (0.0716 g, 0.002 mmol) were mixed together and
allowed for constant stirring followed by addition of triethyleamine (5.5 ml,
0.004 mmol). The color change from green to pale blue was observed, indicating

MACROCYCLIC RING COMPOUNDS
1317
the complexation. A resultant precipitate was separated, washed with water, and
dried. Suitable pale blue single crystals were obtained from methanol–chloroform
solvent mixture upon slow evaporation at room temperature in 48 h. Yield (70%).
Elemental analysis (%) calcd. (found) for C38H34Cu2O18: C, 50.39 (50.47); H, 3.78
(3.58). ES-MS calcd. for C38H34Cu2O18 (M þ 1), 905.04; found: 906.12. UV-vis:
(CH3CN, k, nm, e) 269 (1950), 699 (516). IR spectra (n, cmꢃ1) 3069, 2967, 2358,
1719, 1631, 1595, 1401, 1283, 1255, 1121 1082, 838, 753.
Crystallographic Data
M1. CCDC No. 736229. Mol. formula C22H16NO8, FW 422.36, space group
˚
Pbca, orthorhombic, unit cell a ¼ 19.4811(17), b ¼ 7.7079(7), c ¼ 26.465(2) A;
a ¼ b ¼ c ¼ 90ꢀ, V ¼ 3974.0(6) A3, Z ¼ 8, g (calc.) ¼ 1.412 mg=m3. Final R indices
[I > 2sigma(I)] R1 ¼ 0.0765, wR2 ¼ 0.2022.
M3. CCDC No. 736230. Mol. formula C40H40Cu2O20, FW 967.80, space
˚
group C2=c, monoclinic, unit cell a ¼ 8.2896(11), b ¼ 22.558(3), c ¼ 21.858(3) A;
a ¼ 90, b ¼ 97.682ꢀ, c ¼ 90ꢀ, V ¼ 4050.7(9)A3, Z ¼ 4, g (calc.) ¼ 1.587 mg=m3. Final
R indices [I > 2sigma(I)] R1 ¼ 0.0776, wR2 ¼ 0.1408.
ACKNOWLEDGMENTS
The authors are grateful to the Department of Science and Technology, New
Delhi, India, for financial support (Project Number SR=S1=IC-19=2005). P. M. S.
K. acknowledges the Council of Scientific and Industrial Research (CSIR), India,
for a senior research fellowship.
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