The first observation of cis and trans isomers for bibenzo[d]imidazole- based compounds influenced by halogen substituent effects

Article abstract of DOI:10.1016/j.inoche.2014.01.019

A pair of bibenzo[d]imidazole-based cis-trans positional isomers have been obtained via the condensation between biphenyl-3,3′,4,4′-tetraamine and 3,5-dichloro-2-hydroxybenzaldehyde, and they can be isolated by the following spontaneous crystallization in N,N-dimethylformamide (DMF) and manual separation. Halogen substituent effects are believed to be responsible for the successful isolation of cis and trans isomers, which could be further supported by density function theory (DFT) calculations. To our knowledge, this is the first structural report on the cis-trans isomerism for this family of compounds.

Full text of DOI:10.1016/j.inoche.2014.01.019

Inorganic Chemistry Communications 42 (2014) 23–28
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
The first observation of cis and trans isomers for bibenzo[d]imidazole-
based compounds influenced by halogen substituent effects
⁎
Jiao Geng, Tao Tao, Hui-Qing Chen, Wei Huang
State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A pair of bibenzo[d]imidazole-based cis–trans positional isomers have been obtained via the condensation
between biphenyl-3,3′,4,4′-tetraamine and 3,5-dichloro-2-hydroxybenzaldehyde, and they can be isolated by
the following spontaneous crystallization in N,N-dimethylformamide (DMF) and manual separation. Halogen
substituent effects are believed to be responsible for the successful isolation of cis and trans isomers, which
could be further supported by density function theory (DFT) calculations. To our knowledge, this is the first
structural report on the cis–trans isomerism for this family of compounds.
Received 3 January 2014
Accepted 24 January 2014
Available online 31 January 2014
Keywords:
Cis–trans isomers
Bibenzo[d]imidazoles
Crystal structures
DFT computations
© 2014 Elsevier B.V. All rights reserved.
Recently, bibenzo[d]imidazole derivatives [1] are significant
heterocyclic compounds and they are particularly useful as biologically
active compounds and intermediates in pharmaceutical chemistry [2].
As we know, there is cis–trans constitutional isomerism in this family
of compounds because the two protons of imidazole rings (NH) can
point toward the same (cis) or the opposite (trans) direction of molecu-
lar plane. Unlike the traditional cis–trans isomerism in the double-bond
system, free rotation of the central single bond between the two benzo
[d]imidazole units can be restricted also generating the cis–trans tau-
tomerism, because of the large steric hindrance effects of the attached
groups on both sides. Constigurational isomerism [3–6], as one of the
geometrical isomerisms, is not only important to the fine chemical man-
ufacturers but also to other areas of chemistry. Tautomers in distinctive
isomeric forms have different properties such as pharmacological
effects, crystal habits, helicity and chirality in the solid state and in the
bulk [7–10]. Single-crystal X-ray diffraction method is proved to be the
most powerful tool to characterize various geometrical isomerisms by
its measured bond lengths and angles, dihedral and torsion angles, etc.
The subtle alteration of functional groups, the different tautomeric
forms and crystallographic arrangements help to decide their properties.
In this paper, an isomeric pair of bibenzo[d]imidazole-based
compounds (cis and trans positional isomers of BBI-4Cl), together with
a cis isomer of BBI-4Br, have been obtained via the classical condensa-
tion [11] between biphenyl-3,3′,4,4′-tetraamine and 3,5-dichloro-2-
hydroxybenzaldehyde (or 3,5-dibromo-2-hydroxybenzaldehyde) and
the following spontaneous crystallization [12–14] in DMF and mechan-
ical separation. Halogen substituent effects, intramolecular O\H⋯N
hydrogen bonds and molecular planarity are believed to help the suc-
cessful formation of cis and trans isomers of BBI-4Cl simultaneously
[15]. Distinguishable single-crystal growing habits of them make possi-
ble the separation and structural characterization. DFT calculations have
been done to further compare the differences between the molecular
conformations and spectral properties of these cis and trans isomers.
To the best of our knowledge, this is the first structural report on
cis–trans isomerism for this family of compounds.
Compounds BBI-4Cl and BBI-4Br, having the same bibenzo[d]imidazole/
phenol skeleton shown in Scheme 1, were prepared in satisfactory yields
(62 and 56%) [16]. It is worthwhile to note that this synthetic method has
the advantages of easy to operate, easy work-up and few by-products.
When DMF was used as the reaction solvent and 4 Å molecular sieves
were added as the catalyst in the synthetic process, the yields have been
slightly increased. The proposed formation mechanism [11,17] for com-
pounds BBI-4Cl and BBI-4Br was given in Scheme SI1. At first, the con-
densation between biphenyl-3,3′,4,4′-tetraamine and halogenated
salicylaldehyde afforded the bis-Schiff base 1, and then the intramolecular
nucleophilic addition reaction took place to produce bis-imidazolidine 2.
Finally, the bisimidazole compound was obtained by the oxidative
cyclodehydrogenation of intermediate 2.
UV–Vis absorption and fluorescence emission spectra of compounds
BBI-4Cl and BBI-4Br in their methanol solutions with the same concen-
tration of 1.0 × 10−4 mol/L were recorded at room temperature,
respectively, in order to compare the differences originated from their
molecular structures. Similar optical properties have been shown in
this case, which agree well with the following theoretical results. As il-
lustrated in Fig. 1, due to the presence of large delocalized π-system,
strong absorption bands at 359 (ε = 64600) and 361 (ε = 70900) nm
are assigned to the π–π* transition between the bibenzo[d]imidazole
rings and the phenol units in compounds BBI-4Cl and BBI-4Br, which
are analogous to the previously reported aromatic bis(o-aminoanils)
compounds (340–360 nm) [11,17]. The fluorescence spectra of com-
pounds BBI-4Cl and BBI-4Br at room temperature illustrate a large
⁎
Corresponding author. Tel.: +86 25 83686526; fax: +86 25 83314502.
E-mail address: whuang@nju.edu.cn (W. Huang).
1387-7003/$ – see front matter © 2014 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.inoche.2014.01.019

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J. Geng et al. / Inorganic Chemistry Communications 42 (2014) 23–28
Scheme 1. Molecular structures of different cis and trans isomers for BBI-4Cl and BBI-4Br having the same bibenzo[d]imidazole/phenol skeleton.
Stokes shift, where strong green emission peaks at 476 and 478 nm are
found for BBI-4Cl and BBI-4Br, respectively, upon the same excitation
at 290 nm. A small bathochromic shift of 2 nm from BBI-4Cl to BBI-
4Br is suggested to originate from the halogenated effects in their
molecular structures.
crystal diffraction determination. However, the attempt to obtain the
trans isomer of BBI-4Br has not been successful. The phase purity of
three compounds in this work has been further confirmed by the
PXRD patterns (Fig. SI2 in Supporting information), in which the simu-
lated patterns generated from the results of single-crystal diffraction
data and as-synthesized ones are almost identical, demonstrating
good phase purity of the products.
X-ray structural analyses of three compounds trans-BBI-4Cl·
(DMF)2, cis-BBI-4Cl·(DMF)2 and cis-BBI-4Br·(DMF)2 reveal that the
cis and trans isomers have obviously different unit cells and cis-BBI-
4Cl·(DMF)2 and cis-BBI-4Br·(DMF)2 are isomorphous structures. As
can be seen in Fig. 2, the two protons of imidazole rings point toward
the opposite direction of molecular plane of trans-BBI-4Cl·(DMF)2,
while they point to same direction of molecular planes in the cases
of cis-BBI-4Cl·(DMF)2 and cis-BBI-4Br·(DMF)2. The middle two
benzoimidazole rings of three compounds are essentially coplanar
with the dihedral angles of zero for trans-BBI-4Cl·(DMF)2 and 4.3(5)
and 1.2(8)° for cis-BBI-4Cl·(DMF)2 and cis-BBI-4Br·(DMF)2. It is
worthwhile to mention that strong intramolecular O\H⋯N hydrogen
bonding interactions (Table SI2) are found with the H⋯A distances of
1.82(1) Å in trans-BBI-4Cl·(DMF)2, 1.80(1) and 1.81(1) Å in cis-BBI-
The dark-yellow single crystals of trans-BBI-4Cl·(DMF)2, cis-BBI-
4Cl·(DMF)2 and cis-BBI-4Br·(DMF)2 suitable for X-ray diffraction mea-
surement were grown from DMF by slow evaporation in air at room
temperature for 2–3 weeks [18]. It is very interesting to point out that
the spontaneous formation of single crystals for the cis and trans posi-
tional isomers of BBI-4Cl can be attained in DMF. The yellow crystals
of two structural isomers have different shapes and growing habits.
Namely, the needle crystals of trans-BBI-4Cl·(DMF)2 grow radially as
a single colony from the first-appearing nucleus, while the block crystals
of cis-BBI-4Cl·(DMF)2 grow separately at the bottom of the beaker. So
they can be collected individually by careful manual separation and
used for X-ray single-crystal diffraction measurement successfully. In
contrast, the same experimental protocol has been used to prepare
the cis and trans isomers of BBI-4Br, where the four chlorine atoms of
two side phenol rings are replaced by bromine atoms. As a result, only
cis-BBI-4Br·(DMF)2 is obtained and further verified by X-ray single-
Fig. 1. UV–Vis absorption (left) and fluorescence emission (right) spectra of compounds BBI-4Cl and BBI-4Br recorded in their methanol solutions with the same concentration
of 1.0 × 10−4 mol/L.

J. Geng et al. / Inorganic Chemistry Communications 42 (2014) 23–28
25
Fig. 2. ORTEP drawings of trans-BBI-4Cl·(DMF)2 (a), cis-BBI-4Cl·(DMF)2 (b) and cis-BBI-4Br·(DMF)2 (c) with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30%
probability level. Solvent molecules are omitted for clarity.
4Cl·(DMF)2, 1.81(1) and 1.83(1) Å in cis-BBI-4Br·(DMF)2. As a result,
six-membered C3NOH hydrogen-bonding rings are formed, which
should be helpful to fix the configuration between the substitutional
phenol and imidazole skeleton. Because of the steric hindrance effects
of two fused four-ring units on both sides, the free rotation of the middle
C\C single bond (1.49(1) Å in length, Table SI1) is blocked to some
extent and the presence of different cis and trans positional isomers is
possible in the solid state.
As can be shown in Fig. 3, similar crystal packing modes are found for
three compounds trans-BBI-4Cl·(DMF)2, cis-BBI-4Cl·(DMF)2 and cis-
BBI-4Br·(DMF)2, where contiguous molecules are linked by different
intermolecular hydrogen-bonding and π–π stacking interactions into
two-dimensional supramolecular networks.
On the one hand, distinguishable results on the structures of cis and
trans isomers of BBI-4Cl and BBI-4Br prompt us to seek further theoretic
supports on the halogen substituent effects since the only structural dif-
ference is the replacement of four chlorine atoms with four bromine
atoms at the same positions of two side phenol rings. On the other
hand, single-crystal diffraction data for a pair of cis and trans positional
isomers generally are good candidates for density function theory (DFT)
computational studies on comparing the highest occupied molecular or-
bital (HOMO) and the lowest unoccupied molecular orbital (LUMO)
gaps and energy barriers of different isomers with their spectral data.
Based upon the above-mentioned considerations, DFT computation-
al studies are carried out to make contrastive studies, where the fixed
atom coordinates of four compounds are used for the isomeric energy
barrier and HOMO–LUMO gap calculations. All calculations are carried
out with Gaussian03 programs [19] by B3LYP method and 6-31G*
basis set without any symmetry constraints. The computational results
given in Table 1 reveal that the resultant HOMO–LUMO gaps for cis
and trans isomers of BBI-4Cl and BBI-4Br are 3.66, 3.61, 3.65 and
3.60 eV, which are in agreement with their UV–Vis absorptions. As
depicted in Fig. 4, subtle changes are observed in the calculated spatial
representations of HOMOs and LUMOs because of the influences of
introducing different halogen groups (four Cl versus four Br) in
the two side phenol rings. The middle C\C single bond length is also
similar to the single-crystal data, and the dihedral angles between
the benzoimidazole and the phenol units and those between the

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J. Geng et al. / Inorganic Chemistry Communications 42 (2014) 23–28
Fig. 3. Perspective view and schematic illustration of the packing structures of compounds trans-BBI-4Cl·(DMF)2 (a), cis-BBI-4Cl·(DMF)2 (b) and cis-BBI-4Br·(DMF)2 (c).
benzoimidazole rings are very close to zero showing excellent planarity
of the whole molecules. Nevertheless, it is noted that the energy barrier
for cis and trans isomers (isomerization energy ΔEcis–trans) of BBI-4Cl
and BBI-4Br is significantly different (4.95 versus 1.75 kJ/mol), since dif-
ferent halogen with different heavy atom effects can impact the energy
barrier between the constigurational isomerism. As we know, too large
or too small isomerization energy tends to form only one type of stable
isomer, but suitable isomerization energy will make possible the suc-
cessful isolation of cis and trans isomers individually in the process of
crystallization. So in our case, BBI-4Cl has more suitable isomerization
energy for the isolation of cis and trans isomers individually in
comparison with BBI-4Br, which can be verified by our experimental
results. Furthermore, DMF molecules are believed to play an important
role in the kinetic control of the solvent-induced crystallization.
In summary, this is a study on the supramolecular cis–trans isomeri-
zation and spontaneous crystallization in the solid state. We have de-
scribed herein the single-crystal structures of a pair of cis–trans isomers
of bibenzo[d]imidazole-based compounds trans-BBI-4Cl·(DMF)2 and
cis-BBI-4Cl·(DMF)2 together with a cis isomer of BBI-4Br·(DMF)2.
They are prepared via the condensation between biphenyl-3,3′,4,4′-
tetraamine and 3,5-dichloro-2-hydroxybenzaldehyde (or 3,5-dibromo-
2-hydroxybenzaldehyde), and they can be isolated by the following
spontaneous crystallization in DMF and manual separation. Halogen sub-
stituent effects, intramolecular O\H⋯N hydrogen bonds and molecular
planarity are believed to be responsible for the successful formation of
cis and trans isomers of BBI-4Cl. Distinguishable growing habits of cis
and trans single crystals of BBI-4Cl make possible the separation and
structural characterization of them.
Specifically, the real issue here is the interconversion between the cis
and trans isomers in the solution state. The fact that the cis and trans
crystals are observed for BBI-4Cl would mean that both the cis and
trans configurations are present in significant proportions in solution.
As for BBI-4Br, it seems that the cis isomer is dominant in solution.
DFT calculations have been done to give a theoretic support on the pos-
sible isolation of cis and trans positional isomers individually, where a
Table 1
Calculated HOMO–LUMO gaps and energy barriers for cis and trans isomers of BBI-4Cl and
BBI-4Br for comparisons.
[d]
C\C
Compound
Egopt[a] (eV)
Egcalcd[b] (eV)
ΔE[c] (kJ/mol)
d
(Å)
cis-BBI-4Cl
3.45
3.62
3.66
3.61
3.65
4.95
1.493
1.485
trans-BBI-4Cl
cis-BBI-4Br
trans-BBI-4Br
3.43
1.75
aOptical gap from normalized absorption spectra.
bHOMO–LUMO gap calculated by DFT B3LYP/6-31G* level.
cEnergy barrier for cis and trans isomers.
dMean middle C\C single bond length after full optimization.

J. Geng et al. / Inorganic Chemistry Communications 42 (2014) 23–28
27
Fig. 4. The HOMO and LUMO energy levels and their molecular orbital distributions of compounds trans-BBI-4Cl, cis-BBI-4Cl, trans-BBI-4Br and cis-BBI-4Br.
[3] W.J. Zhang, A. Berglund, J. Kao, J.P. Couty, M. Gershengorn, G. Marshall, J. Am. Chem.
Soc. 125 (2003) 1221–1235.
[4] W. You, H.Y. Zhu, W. Huang, B. Hu, Y. Fan, X.Z. You, Dalton Trans. 39 (2010)
7876–7880.
[5] S. Owens, D. Smith, C. Lake, G. Grey, Eur. J. Inorg. Chem. 30 (2008) 4710–4718.
[6] J.H. Cheng, Y.H. Zhang, X.F. Ma, X.G. Zhou, H.F. Xiang, Chem. Commun. 49 (2013)
11791–11793.
[7] D. Fox, P. Metrangolo, D. Pasini, T. Pilati, G. Resnati, G. Terraneo, CrystEngComm 10
(2008) 1132–1136.
more suitable ΔEcis–trans value for BBI-4Cl is found. So, it is suggested
that the cis and trans isomers of BBI-4Br convert to each other more
easily than BBI-4Cl, and this assumption can explain our experimental
and computational result. To the best of our knowledge, this is the
first structural report on the cis–trans structural isomers and a special
case of spontaneous crystallization in the bibenzo[d]imidazole system.
[8] J.E. Lee, H.J. Kim, M.R. Han, S.Y. Lee, W.J. Jo, S.S. Lee, J.S. Lee, Dyes Pigments 80 (2009)
181–186.
[9] A. Kennedy, P. Andrikopoulos, J.B. Arlin, D. Armstrong, N. Duxbury, D. Graham, J.
Kirkhouse, Chem. Eur. J. 15 (2009) 9494–9504.
[10] T. Tao, F. Xu, X.C. Chen, Q.Q. Liu, W. Huang, X.Z. You, Dyes Pigments 92 (2012)
916–922.
[11] N. Coville, E. Neuse, J. Org. Chem. 42 (1977) 3485–3491.
Acknowledgments
This work was financially supported by the Major State Basic Research
Development Programs (Nos. 2013CB922101 and 2011CB933300), the
National Natural Science Foundation of China (No. 21171088), and the
Natural Science Foundation of Jiangsu Province (Grant BK20130054).
[12] I. Bernal, J. Cetrullo, Inorg. Chim. Acta 134 (1987) 105–112.
[13] W. Huang, T. Ogawa, Polyhedron 25 (2006) 1379–1385.
[14] H.F. Qian, W. Huang, Transit. Met. Chem. 31 (2006) 347–352.
[15] Y.H. Luo, B.W. Sun, CrystEngComm 15 (2013) 7490–7497.
[16] Synthesis of BBI-4Cl: A 50 mL round-bottom flask was flame-dried under reduced
pressure, and then biphenyl-3,3′,4,4′-tetraamine (0.21 g, 1.0 mmol), 3,5-dichloro-
2-hydroxybenzaldehyde (0.42 g, 2.2 mmol), and ethanol (20 mL) were added
under nitrogen. After 14 h' refluxing, yellow solid precipitated in the reaction mix-
ture. The precipitate was filtered, washed with ethanol and chloroform, and then
dried to obtain the product BBI-4Cl (0.34 g, 62%). M.p. N 300 °C. Anal. Calcd. for
[C26H14Cl4N4O2]: C, 56.14; H, 2.54; N, 10.07%. Found: C, 55.72; H, 3.02; N, 10.55%.
Main FT-IR absorptions (KBr pellets, cm−1): 3418 (m), 2105 (w), 1640 (w), 1128
(vs), 615 (m). 1H NMR (500 MHz, d6-DMSO) δ: 8.12 (s, 2H, phenol), 7.88 (s, 2H,
phenol), 7.64 (s, 2H, benzoimidazole), 7.63 (d, 2H, benzoimidazole), 7.54 (d, 2H,
benzoimidazole). ESI-TOF-MS (m/z): Calcd. for [C26H14Cl4N4O2]+ 556.2, found
555.6. Synthesis of BBI-4Br: The synthesis of BBI-4Br was similar to that described
for BBI-4Cl. Yield, 0.41 g, 56%. M.p. N 300 °C. Anal. Calcd. for [C26H14Br4N4O2]: C,
42.54; H, 1.92; N, 7.63%. Found: C, 42.08; H, 2.40; N, 8.01%. Main FT-IR absorptions
(KBr pellets, cm−1): 3386 (m), 2927 (m), 2360 (m), 1660 (m), 1455 (s), 1256 (m),
800 (m), 683 (m). 1H NMR (500 MHz, d6-DMSO) δ: 8.35 (s, 2H, phenol), 7.95 (s, 2H,
phenol), 7.92 (s, 2H, benzoimidazole), 7.80 (d, 2H, benzoimidazole), 7.74 (d, 2H,
benzoimidazole). ESI-TOF-MS (m/z): Calcd. for [C26H14Br4N4O2]+ 734.0, found
733.1.
Appendix A. Supplementary material
CCDC reference numbers 896866–896868 for compounds trans-BBI-
4Cl·(DMF)2, cis-BBI-4Cl·(DMF)2 and BBI-4Br·(DMF)2 contain the
supplementary crystallographic data for this paper. These data can be
obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html
[or from the Cambridge Crystallographic Data Centre, 12, Union Road,
Cambridge CB2 1EZ, UK; fax: (internet) +44 1223/336 033; e-mail:
deposit@ccdc.cam.ac.uk]. Supplementary data to this article can be
found online at http://dx.doi.org/10.1016/j.inoche.2014.01.019.
References
[1] W.S. Huang, J.T. Lin, C.H. Chien, Y.T. Tao, S.S. Sun, Y.S. Wen, Chem. Mater. 16 (2004)
2480–2488.
[2] C. Mizuno, A. Chittiboyina, F. Shah, A. Patny, T. Kurtz, H. Pershadsingh, R. Speth, V.
Karamyan, P. Carvalho, M. Avery, J. Med. Chem. 53 (2010) 1076–1085.
[17] F. Johnson, I. Cabasso, Macromolecules 43 (2010) 3634–3651.

28
J. Geng et al. / Inorganic Chemistry Communications 42 (2014) 23–28
[18] Three single-crystal samples were covered with glue and mounted on glass fibers
for data collection at 291(2) K with Mo-Kα radiation (λ = 0.71073 Å) and a Bruker
SMART 1 K diffractometer equipped with a CCD camera. Data collection was per-
formed by using the SMART program, and cell refinement and data reduction
were made with the SAINT program. The structures were solved by direct methods
and refined by least-squares methods on Fo2 by using the SHELXTL software pack-
age. trans-BBI-4Cl·(DMF)2, C26H14Cl4N4O2·(C3H7NO)2, Mr = 702.40, triclinic space
Å3, Z = 2, Dc = 1.766 g·cm−3, crystal size (mm) = 0.10 × 0.12 × 0.14, 8335 reflec-
tions measured, 5738 unique (Rint = 0.056), S = 0.78, R1 = 0.0433 and wR2
0.0988. Selected bond distances and bond angles are given in Table SI1. Moreover,
intermolecular N\H⋯O and C\H⋯O hydrogen bonding interactions are given in
Table SI2.
=
[19] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, J.A.
Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar, J.
Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson, H.
Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian,
J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O.
Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma,
G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels,
M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J.V.
Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko,
P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A.
Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C.
Gonzalez, J.A. Pople, Gaussian 03, Revision D 02, Gaussian Inc., Wallingford CT, 2004.
group P 1 ,
a = 8.059(2), b = 9.181(3), c = 11.255(3) Å, α = 78.189(4),
β = 82.367(4), γ = 83.072(4)°, V = 804.1(4) Å3, Z = 1, Dc = 1.451 g·cm−3
,
crystal size (mm) = 0.06 × 0.08 × 0.16, 4036 reflections measured, 2785 unique
(Rint = 0.052), S = 0.82, R1 = 0.0512 and wR2 = 0.1372; cis-BBI-4Cl·(DMF)2,
C26H14Cl4N4O2·(C3H7NO)2, Mr = 702.40, triclinic space group P1, a = 10.2554(10),
b = 12.1015(12), c = 13.8172(13) Å, α = 85.911(2), β = 71.909(1), γ =
79.359(1)°, V = 1601.8(3) Å3, Z = 2, Dc = 1.456 g·cm−3, crystal size (mm) =
0.12 × 0.14 × 0.16, 8183 reflections measured, 5576 unique (Rint = 0.032),
S = 0.83, R1 = 0.0472 and wR2 = 0.1225. cis-BBI-4Br·(DMF)2, C26H14Br4N4O2·(C3-
H7NO)2, Mr = 880.20, triclinic space group P1, a = 10.3067(16), b = 12.3701(19),
c = 13.878(2) Å, α = 85.703(2), β = 72.457(2), γ = 78.861(2)°, V = 1655.0(4)