Synthesis, conformational parameters and packing considerations of methyl bispyridyl ketones

Article abstract of DOI:10.1016/j.molstruc.2015.06.020

The crystal structures of two bispyridyl ketones featuring either two methyl residues or one methyl and one bromomethyl residue, respectively, are presented. In order to elucidate the influence of the substituents, a comprehensive comparison with the non-methylated mother compound has been performed. A special focus lies thereby on the relative position of the heteroatoms and their free electron pairs. The two methyl groups at the bispyridyl ketone result in two molecules in the asymmetric unit adopting rather different conformations. Due to the fast crystallization conditions and a melting point differing from the literature, a polymorph close to a local minimum in the energy hypersurface seems possible. After introducing a bromine atom to one of the two methyl groups, the molecular conformation is very similar to the unsubstituted molecule. The packing of both title compounds is dominated by weak contacts of the C-H...π and C-H...Y type (Y = O, N) and C-H...Br- and Br...π-contacts for the brominated molecule.

Full text of DOI:10.1016/j.molstruc.2015.06.020

Accepted Manuscript
Synthesis, conformational parameters and packing considerations of methyl bispyridyl
ketones
Christian Weck, Felix Katzsch, Tobias Gruber
PII:
S0022-2860(15)30049-1
10.1016/j.molstruc.2015.06.020
MOLSTR 21572
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 7 May 2015
Revised Date: 4 June 2015
Accepted Date: 5 June 2015
Please cite this article as: C. Weck, F. Katzsch, T. Gruber, Synthesis, conformational parameters and
packing considerations of methyl bispyridyl ketones, Journal of Molecular Structure (2015), doi: 10.1016/
j.molstruc.2015.06.020.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Synthesis, conformational parameters and packing
considerations of methyl bispyridyl ketones
Christian Weck, Felix Katzsch, Tobias Gruber*
Institute of Organic Chemistry, Technische Universität Bergakademie Freiberg,
Leipziger Strasse 29, Freiberg/Sachsen, Germany; Email: Tobias.Gruber@chemie.tu-
freiberg.de
*
Corresponding author. Tel.: +49-3731-39-2390.
E-mail address: Tobias.Gruber@chemie.tu-freiberg.de (T. Gruber)
Keywords:
Bispyridyl ketone
Conformational properties
Single crystal X-ray structure
C-H···π-interaction
Br···π-contacts
1

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Abstract
The crystal structures of two bispyridyl ketones featuring either two methyl residues or
one methyl and one bromomethyl residue, respectively, are presented. In order to
elucidate the influence of the substituents, a comprehensive comparison with the non-
methylated mother compound has been performed. A special focus lies thereby on the
relative position of the heteroatoms and their free electron pairs. The two methyl
groups at the bispyridyl ketone result in two molecules in the asymmetric unit
adopting rather different conformations. Due to the fast crystallization conditions and
a melting point differing from the literature, a polymorph close to a local minimum in
the energy hypersurface seems possible. After introducing a bromine atom to one of
the two methyl groups, the molecular conformation is very similar to the unsubstituted
molecule. The packing of both title compounds is dominated by weak contacts of the
C-H···π and C-H···Y type (Y = O, N) and C-H···Br- and Br···π-contacts for the
brominated molecule.
2

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1
. Introduction
Bidentate ligands are well-known for their ability to form cation-complexes. When
they are added to a pre-existing complex of monodentate ligands in most cases a more
stable complex will be formed. In this respect, molecules featuring a combination of
rigidity on the one hand and flexibility on the other have proven to be successful
ligands. Putative examples deliver the combination of two pyridine rings linked via
single bonds with a carbonyl group resulting in so-called bispyridyl ketones. These are
well known for their variable modes of metal coordination, which is especially true for
pyridines that are substituted in the α-position, i.e. 2,2′-bispyridyl ketones (Scheme 1).
N,O-coordination will generate a five-membered chelate ring and N,N-coordination is
delivering a six-membered chelate [1]. Due to their pertinent reactivity and easy
preparation bispyridyl ketones have found frequent application as ligands for metal
complexes used in biological [2] as well as in materials chemistry [3] or studied for
their electrochemical properties [4]. Moreover, they have proven useful for the
preparation of anticancer agents [5] and as versatile building blocks for the generation
of tripodal systems [6], coordination polymers [7] or macrocycles [8]. Only recently,
the use of 1 as a ligand for aminoacetoxylation of unactivated alkenes has been
described [9].
O
N
N
1
Scheme 1 2,2′-Bispyridyl ketone (1)
The properties of bispyridyl ketone 1 have already been studied in detail which is
true for its dipole moment [10], vibrational assignment [11] and X-ray crystal structure
[12]. When electron donating methyl groups are added to the pyridine rings of 1 a
change of electronic and conformational properties are expected. Prompted by these
considerations, we prepared the title ketones 2 and 3 (Scheme 2) featuring either two
additional methyl residues or one methyl and one bromomethyl residue, respectively,
each in α-position to the pyridine nitrogen. Furthermore, we present their X-ray
structures and discuss their conformational behavior. A special focus lies thereby on
the relative position of the heteroatoms and their free electron pairs [13].
Scheme 2 Synthesis of bispyridyl ketones 2 and 3. a) n-BuLi, ethyl chloroformate, THF; b) NBS,
CCl4.
3

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2
. Experimental
2
.1. Synthesis
General
The melting points were measured on a microscope heating stage PHMK Rapido
1
13
(
VEB Dresden Analytik) and are uncorrected. H and C NMR spectra were obtained
1
13
from a Bruker Avance 500 at 500.1 ( H) and 125.8 MHz ( C) using TMS as internal
standard. Chemical shifts for proton and carbon resonances are given in ppm (δ).
Signal multiplicity is characterized by s (singlet), d (doublet), dd (double doublet) and
t (triplet). Mass spectra were recorded on a Hewlett Packard 5890 Series II/MS 5971
A. Elemental analyses have been performed on a Heraeus CHN-Rapid Analyzer.
Analytical TLC was performed on precoated silica gel plates (60 F , Merck). The
2
54
reagents and solvents were used as purchased from the chemical suppliers.
Bis(6-methylpyridin-2-yl)methanone (2)
Title ketone 2 has been synthesized by a coupling reaction between 2-bromo-6-
methylpyridine [14] and ethyl chloroformate following a literature procedure [15].
Inconsistent with the literature we found a melting point of 46-48 °C (lit. [15]: 6 °C).
We assume that the literature describes an amorphous solid or a polymorph. All other
analytical data are in coherence.
(6-(Bromomethyl)pyridin-2-yl)(6-methylpyridin-2-yl)methanone (3)
Monobromo derivative 3 has been reccovered as a side product from the double
bromination of 2 using N-bromosuccinimide and AIBN as described in the literature
[
15]. 10 g of ketone 2 delivered 2.72 g of the respective dibromide (yield: 15.6 %) and
14 mg of monobromide 3 (yield: 2.3%) after chromatographic purification (SiO2;
dichloromethane/ethyl acetate = 20:1). Mp. 155-160 °C (decomp.). R : 0.27 [SiO ,
3
f
2
1
2
ethyl acetate/ hexane, 1:1 ν/ν], H-NMR (500 MHz, CDCl , δ [ppm]): 8.10 (dd, J=5
3
3
3
3
Hz, 1H), 8.02 (d, J=8 Hz, 1H), 7.80 (t, J=8 Hz, 1H), 7.64 (t, J=7.5 Hz, 1H), 7.39
3
3
13
(
dd, J=8 Hz, 1H), 7.31 (d, J=7.5 Hz, 1H), 4.59 (s, 2H), 2.65 (s, 3H); C-NMR (500
MHz, CDCl , δ [ppm]): 190.8 (CO), 158.3 (C5), 156.5 (C8), 153.7 (C12), 152.9 (C1),
3
1
37.7 (C10), 137.0 (C3),. 126.5 (C9), 126.3 (C2), 124.8 (C11), 123.2 (C4), 33.4
+
(CH Br), 24.4 (CH ). GC-MS: Calculated: 291, Found: 291 [M] (GC/MS: 120°C, 3
2 3
min, 20°C/min).
2
.2. X-ray structure determination
Colourless crystals of 2 suitable for single-crystal X-ray diffraction have been
grown by recrystallization from n-hexane at -20 °C. Respective crystals of 3 have been
recovered after crystallization from ethanol/THF (1:1).
The single crystal X-ray diffraction data of compounds 2 and 3 have been collected
at 100 K on a Bruker Kappa diffractometer equipped with an APEX II CCD area
detector and graphite-monochromatized Mo Kα radiation (λ = 0.71073 Å) employing
φ and ω scan modes. The data were corrected for Lorentz and polarization effects.
4

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Semi-empirical absorption correction was applied using the SADABS program [16].
The SAINT program [16] was used for the integration of the diffraction profiles. The
crystal structure was solved by direct methods using SHELXS-97 [17] and refined by
full-matrix least-squares refinement against F2 using SHELXL-97 [17]. All non-
hydrogen atoms have been refined anisotropically. The hydrogen atoms were
generated at ideal geometrical positions and refined with the appropriate riding model.
Geometrical calculations were performed using PLATON [18] and molecular graphics
were generated using SHELXTL [17]. Details of the data collection and refinement
calculations can be found in Table 1; geometrical parameters are displayed in Tables
S1 and S2 (Supplementary Material).
Crystallographic data for the structures in this paper have been deposited with the
Cambridge Crystallographic Data Centre (CCDC 1062341 for 2 and CCDC 1062342
for 3). Copies of these data can be obtained free of charge via
www.ccdc.cam.ac.uk/datarequest/cif, by e-mailing data-request@ccdc.com.ac.uk or
by contacting the Cambridge CB21 EZ, U.K.; Fax, +44 1223 336033.
Table 1
Crystal data and selected details of the data collection and refinement calculations of compounds 2 and 3
Compound
2
3
empirical formula
C H N O
C H BrN O
13 11 2
1
3
12
2
formula weight
crystal system
space group
a/Å
b/Å
c/Å
212.25
triclinic
P-1
291.15
monoclinic
P2 /c
1
8.8258(2)
10.8715(2)
12.4172(2)
74.260(1)
84.811(1)
73.105(1)
1097.17(3)
4
6.5371(7)
20.097(2)
9.3715(10)
90
α
β
/°
/°
101.221(3)
90
γ
V/Å
/°
3
1207.7(2)
4
Z
F(000)
448
1.285
584
1.601
-
3
D /g cm
c
-
1
µ
/mm )
0.08
3.39
data collection:
temperature/K
100(2)
100(2)
no. of collected reflections
18043
9257
within the
θ
-limit (°)
2.03-25.00
2.08-24.98
index ranges ±h, ±k, ±l
no. of unique reflections
Rint
-10/10, -12/12, -14/14
3857
0.025
-7/7, -23/23, -11/11
2122
0.033
refinement calculations:
2
full-matrix least-squares on all F values
a
2
2
2
-1
2
2
2
-1
weighting expression w
[
σ
(F )+(0.0442P) +0.3582P]
[σ (F )+(0.0411P) +0.63365P]
0
0
no. of refined parameters
293
155
no. of F values used [I>2
final R-Indices:
σ
(I)]
3299
1862
R(=Σ|∆F| / Σ|F |)
wR on F
S (=Goodness of fit on F )
0.035
0.027
o
2
0.093
1.06
0.072
1.05
2
-
3
Final ∆ρmax/∆ρmin /e Å
0.31, -0.28
0.49, -0.43
a
2
2
o c
P =(F + 2F )/3.
5

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3
. Results and discussion
3
.1. X-ray single crystal structure
Compound 2 crystallizes from n-hexane at -20 °C in the triclinic space group P-1
with two molecules in the asymmetric unit. In both independent molecules the two
aromatic rings vary from perpendicularity (70.3 and 68.4 °) and develop a
considerable higher dihedral angle than found for the mother bispyridylketone (55.8 °)
[
12]. By way of interest, the so-called pitch angles, i.e. the angles between the planes
of each aromatic unit and the plane defined by C -C -C , are rather different
aryl bridge aryl
within molecule 1 and, however, more or less identical in molecule 2 (Fig. 1). The
pyridine rings in both molecules in 2 adopt a syn conformation. As we found no
intramolecular interactions this conformation seems only to be determined by
electronic and packing properties.
Fig. 1. The independent molecular components of 2 showing the atom-labelling
scheme. Displacement ellipsoids are drawn at the 50 % probability level.
Table 2
Selected conformational parameters for the molecular structures of 2 and 3
a
b
Compound Caryl-Cbridge-Caryl angle (°) Dihedral angle φ (°) Pitch angle ψ (°)
1
2
2
3
[12]
(1)
119.8
119.7
119.8
119.8
55.8
70.3
68.4
54.1
44.6; 13.1
22.1; 59.6
37.9; 38.9
35.3; 25.0
(2)
a
Dihedral angle between the planes of the heteroaromatic units
Angle between the plane of each heteroaromatic unit and the plane defined by Caryl-Cbridge-Caryl
b
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Table 3
Distances and angles of hydrogen bond type and other interactions
distances (Å) angle (°)
atoms
symmetry
D···A H···A D–H···A
2
C(6)-H(6B)···O(2)
C(15)-H(15)···O(2)
C(22)-H(22)··· N(3)
C(24)-H(24)···O(1)
C(16)-H(16) ···centroid (B)
1-x, 2-y, -z
-x, 1-y, -z
1-x, 1-y, -z
2-x, 1-y, 1-z
1-x, 1-y, -z
3.443(2) 2.51
3.437(2) 2.52
3.398(2) 2.74
3.299(2) 2.42
3.318(1) 2.94
165
168
128
158
106
a
3
C(4)-H(4)···Br(1)
C(6)-H(6B)···O(1)
C(6)-H(6B)···N(1)
C(9)-H(9)···centroid (A)
C(2)-H(2)···centroid (C)
1+x, y, z
1-x, 1-y, 1-z
1-x, 1-y, 1-z
1-x, 1-y, -z
x, y, z
3.745(2) 3.02
3.323(3) 2.63
3.356(3) 2.46
3.776(3) 2.92
2.982(3) 2.65
134
119
150
151
101
155
a
a
a
C(6)-Br(1)···centroid (D)
1-x, -1/2+y, 1/2-z 3.368(3)
a
Centroid means the ‘centre of gravity’ of the respective aromatic system, centroid
A) = N(1)-C(1)-C(2)-C(3)-C(4)-C(5), centroid (B) = N(2)-C(8)-C(9)-C(10)-C(11)-
(
C(12), centroid (C) = N(2)-C(8), centroid (D) = C(10)-C(11).
a)
b)
Fig. 2. a) Packing detail in the structure of bispyridyl ketone 2. Broken lines indicate
hydrogen contacts. b) Specifics of the aromatic contacts in 2 (view down the a axis).
In the packing of 2 both carbonyl oxygen atoms are actively involved in
intermolecular network. We pinpointed three C-H···O-contacts involving one of the
methyl groups and aromatic hydrogen atoms [d(H···O) = 2.42-2.52 Å]; atom O(2) is
thereby engaged into a bifurcated contact. Additionally, we observed a C-H···N-
7

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interaction [d(H···N) = 2.74 Å] (Fig. 2a). The heteroaromatic rings B and A’ are
pairwise connected (B with B and A’ with A’) and develop rather short distances
suggesting π···π-stacking [d(centroid B···centroid B) = 3.597(2) Å; d(centroid
A’···centroid A’) = 3.375(2) Å]. Rings A’ and B are inclined by an angle of 24.4 ° to
each other and connected via a rather weak C-H···π-contact [d(H···π) = 2.94 Å] (Fig.
2
b). This is reminiscent of sandwich-herringbone structures [19], though these develop
in most cases higher angles between the π-stacked pairs.
Crystallization of monobromide 3 from ethanol/THF (1:1) gives monoclinic crystals in
the space group P2 /c. The introduction of a bromo substituent at one of the methyl
1
groups is accompanied by decreasing dihedral and pitch angles (Table 2). Thus, the
molecule of 3 is less bulky than 2. The molecular conformation is to a certain extent
determined by an intramolecular C-H···π-interaction between C(2) and the π-system
of atoms N(2) and C(8) [d(H···centroid C) = 2.65 Å].
Fig. 3. Molecular structure of 3 at 50 % probability level.
Within the packing of 3 we observed intense stacking along the crystallographic c
axis. Thereby, two pyridine rings A develop a distance of 3.406(3) Å and H9 is
engaged into C-H···π-contact towards ring A. Noteworthy, we found stacking-like
interactions between two carbonyl groups [d = 3.143(3) Å]. This feature can also be
found in the structure of the mother compound (d = 3.182 Å), though not in bispyridyl
2
. The resulting piles of molecules are further connected by methylene hydrogen atom
H(6B) links two molecules via a mixed invers-bifurcated C-H···Y-contact (Y = O, N).
By way of interest the bromine atom avoids bromine-bromine contacts, though is
engaged into C-H···Br- and Br···π-contacts.
8

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Fig. 4. Packing diagram of 3 viewed down the crystallographic a axis. Broken lines
indicate hydrogen bonding.
3
.2. Comparison of bispyridyl ketones 1, 2 and 3
When dealing with bispyridyl ketones, the position of the two pyridine nitrogen atoms
to each other and with respective to the carbonyl oxgen is of special interest. Bock and
co-workers [20] studied the conformation of mother ketone 1 and found one of its
pyridines turned toward the carbonyl group [angle(N1-C1-C7-O1) = 41 °] and one
turned away from carbonyl oxygen [angle(N2-C8-C7-O1) = -163 °] to avoid a clash of
the respective lone pairs (symmetry point group C ). In order to secure comparability
1
with the methyl derivatives 2 and 3 discussed here, we executed energy minimizations
(MacroModel V.9.8, OPLS_2005 forcefield, MCMM, 1,000 steps) of all three
compounds discussed here. The resulting conformational parameters for 1 are rather
similar to its X-ray structure. By way of interest, the modelling also delivered
coinciding data for 2 and 3 (Fig. 5).
1
2
3
: τ = -35 °; τ = 158 °; d = 2.84 Å
1 2
: τ = -33 °; τ = 156 °; d = 2.84 Å
1
2
: τ = -33 °; τ = 156 °; d = 2.83 Å
1
2
Fig. 5. Conformational parameters in compounds 1-3 as found by energy-
minimization (1: R = R‘ = H; 2: R = R‘ = CH ; 3: R = CH Br, R‘ = CH ).
3
2
3
In contrast to the bispyridyl mother compound (1), the nitrogen atoms in both
molecules of 2 adopt a syn conformation deviating more (molecule 1) or less
(
molecule 2) from the C point group. Unlike as suggested by the energy
2
9

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minimization, the two nitrogen atoms develop a rather short distance of 3.18(2) and
3
.09(2) Å, respectively (Fig. 6). Due to the rather similar conformation after energy-
minimization, we reasoned that 2 could have a relative energy comparable to 1: while
the mother compound (1) crystallizes in an anti conformation, energetically situated
between the global maximum and a global minimum, the syn conformation of
dimethyl bispyridyl ketone 2 resembles a local maximum in the energy hypersurface
[
20]. Due to a fast crystallization at -20 °C and more than one molecule in the
asymmetric unit a polymorphic structure is possible, which is also suggested by a
different melting point of 2 compared to literature, 46-48 °C vs. 6 °C [15].
In 3, similar to mother compound 1 the heterocyclic rings approach an anti
conformation (symmetry point group C ) being in coherence with the energy-
1
minimized structure (Fig. 5, Fig. 6). It seems astonishing that a large CH Br
2
substituent has a smaller influence over the molecular conformation of the bispyridyl
ketone than a methyl group alone. Obviously, due to a slow crystallization process a
more favorable geometry is adopted, than observed for 2.
1
[12]
d(N···O) = 2.79(2) Å
2
(1)
d(N···N) = 3.18(2) Å
2
(2)
d(N···N) = 3.09(2) Å
3
d(N···O) = 2.76(3) Å
Fig. 6. Torsion angles, spacefilling representations and typical
distances of O and N atoms of the bispyridyl ketone structures
discussed in this paper.
10

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4
. Conclusions
The crystal structures of two methylated bispyridyl ketones (2 and 3) have been
determined. In order to elucidate the influence of the substituents, a comprehensive
comparison with the non-methylated mother compound (1) has been performed. (1)
The C -Cbridge-Caryl angle (°) is not influenced by differently substituted pyridyl rings.
aryl
(2) In the structure of the double methylated ketone 2 the two molecules of the
asymmetric unit adopt rather different conformations. However, both pyridine rings
are in a syn arrangement. (3) Due to the fast crystallization conditions and a melting
point differing from the literature, we suspect that we found a polymorph close to a
local minimum in the energy hypersurface. (4) After introducing a bromine atom to
one of the two methyl groups as in compound 3, the molecular conformation is very
similar to the unsubstituted molecule; an anti conformation has been observed. (5) The
packing of both title compounds is dominated by weak contacts of the C-H···π and C-
H···Y type (Y = O, N). For 3, C-H···Br- and Br···π-contacts have been found.
Acknowledgment
Financial support from ‘Fonds der Chemischen Industrie’ and the Institute of
Organic Chemistry, TU Bergakademie Freiberg, is gratefully acknowledged.
Furthermore, we thank C. Hübler for his helpful advice.
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Highlights:
•
•
•
•
•
•
Single crystals of methylated bispyridyl ketones are determined by X-ray diffraction.
Comparison with the parent compound reveals conformational relations.
Two CH groups at the ketone core result in two conformational different molecules.
3
Both adopt rather different conformations with the nitrogen in a syn arrangement.
Α bromine atom at one CH gives a conformation similar to the parent molecule.
3
The packing is dominated by C-H···π-, Br···π- and C-H···Y-contacts (Y = O, N, Br).

ACCEPTED MANUSCRIPT
Supplementary Material for
Journal of Molecular Structure
Synthesis, conformational parameters and packing
considerations of methyl bispyridyl ketones
Christian Weck, Felix Katzsch, Tobias Gruber*
Institute of Organic Chemistry, Technische Universität Bergakademie Freiberg,
Leipziger Strasse 29, Freiberg/Sachsen, Germany;
Email: Tobias.Gruber@chemie.tu-freiberg.de
S1

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Table S1
Geometrical parameters (Å, °) for compound 2
N2-C8 = 1.3390(18)
N2-C12 = 1.3444(18)
C1-C2 = 1.3848(19)
C1-C7 = 1.4920(19)
C2-C3 = 1.377(2)
C2-H2 = 0.9300
N4-C25 = 1.3418(17)
N4-C21 = 1.3449(17)
C14-C15 = 1.3843(18)
C14-C20 = 1.4939(18)
C15-C16 = 1.387(2)
C15-H15 = 0.9300
C3-C4 = 1.380(2)
C3-H3 = 0.9300
C16-C17 = 1.376(2)
C16-H16 = 0.9300
C4-C5 = 1.3973(19)
C4-H4 = 0.9300
C17-C18 = 1.392(2)
C17-H17 = 0.9300
C5-C6 = 1.4974(19)
C6-H6A = 0.9600
C6-H6B = 0.9600
C6-H6C = 0.9600
C7-C8 = 1.4998(19)
C8-C9 = 1.382(2)
C9-C10 = 1.380(2)
C9-H9 = 0.9300
C18-C19 = 1.4978(19)
C19-H19A = 0.9600
C19-H19B = 0.9600
C19-H19C = 0.9600
C20-C21 = 1.4979(18)
C21-C22 = 1.3869(19)
C22-C23 = 1.3847(19)
C22-H22 = 0.9300
C10-C11 = 1.377(2)
C10-H10 = 0.9300
C11-C12 = 1.389(2)
C11-H11 = 0.9300
C12-C13 = 1.498(2)
C13-H13A = 0.9600
C13-H13B = 0.9600
C13-H13C = 0.9600
C23-C24 = 1.379(2)
C23-H23 = 0.9300
C24-C25 = 1.396(2)
C24-H24 = 0.9300
C25-C26 = 1.4964(19)
C26-H26A = 0.9600
C26-H26B = 0.9600
C26-H26C = 0.9600
C5-N1-C1 = 117.66(11)
C8-N2-C12 = 117.29(12)
N1-C1-C2 = 124.05(12)
N1-C1-C7 = 115.99(11)
C2-C1-C7 = 119.73(12)
C3-C2-C1 = 117.81(13)
C3-C2-H2 = 121.1
C18-N3-C14 = 117.28(11)
C25-N4-C21 = 117.34(11)
N3-C14-C15 =124.44(12)
N3-C14-C20 = 116.14(11)
C15-C14-C20 = 119.28(12)
C14-C15-C16 = 117.64(13)
C14-C15-H15 = 121.2
C1-C2-H2 = 121.1
C16-C15-H15 = 121.2
C2-C3-C4 = 119.32(13)
C2-C3-H3 = 120.3
C17-C16-C15 = 118.56(13)
C17-C16-H16 = 120.7
C4-C3-H3 = 120.3
C15-C16-H16 = 120.7
C3-C4-C5 = 119.48(13)
C3-C4-H4 = 120.3
C16-C17-C18 = 120.28(13)
C16-C17-H17 = 119.9
C5-C4-H4 = 120.3
C18-C17-H17 = 119.9
N1-C5-C4 = 121.64(12)
N1-C5-C6 = 116.65(12)
C4-C5-C6 = 121.71(12)
C5-C6-H6A = 109.5
N3-C18-C17 = 121.69(13)
N3-C18-C19 = 117.19(12)
C17-C18-C19 = 121.10(12)
C18-C19-H19A = 109.5
S2

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C5-C6-H6B = 109.5
C18-C19-H19B = 109.5
H19A-C19-H19B = 109.5
C18-C19-H19C = 109.5
H19A-C19-H19C = 109.5
H19B-C19-H19C = 109.5
O2-C20-C14 = 120.38(12)
O2-C20-C21 = 119.78(12)
C14-C20-C21 = 119.83(11)
N4-C21-C22 = 124.17(12)
N4-C21-C20 = 116.44(11)
C22-C21-C20 = 119.32(12)
C23-C22-C21 = 117.79(13)
C23-C22-H22 = 121.1
H6A-C6-H6B = 109.5
C5-C6- H6C = 109.5
H6A-C6-H6C = 109.5
H6B-C6-H6C = 109.5
O1-C7-C1 = 120.65(13)
O1-C7-C8 = 119.60(12)
C1-C7-C8 = 119.66(11)
N2-C8-C9 = 124.13(13)
N2-C8-C7 = 116.84(12)
C9-C8-C7 = 118.97(13)
C10-C9-C8 = 117.98(14)
C10-C9-H9 = 121.0
C8-C9-H9 = 121.0
C21-C22-H22 = 121.1
C11-C10-C9 = 118.86(14)
C11-C10-H10 = 120.6
C9-C10-H10 = 120.6
C24-C23-C22 = 118.98(13)
C24-C23-H23 = 120.5
C22-C23-H23 = 120.5
C10-C11-C12 = 119.70(14)
C10-C11-H11 = 120.1
C12-C11-H11 = 120.1
N2-C12-C11 = 121.95(13)
N2-C12-C13 = 116.49(13)
C11-C12-C13 = 121.56(13)
C12-C13-H13A = 109.5
C12-C13-H13B = 109.5
H13A-C13-H13B = 109.5
C12-C13-H13C = 109.5
H13A-C13-H13C = 109.5
H13B-C13-H13C = 109.5
C23-C24-C25 = 119.67(13)
C23-C24-H24 = 120.2
C25-C24-H24 = 120.2
N4-C25-C24 = 121.99(13)
N4-C25-C26 = 116.91(12)
C24-C25-C26 = 121.10(12)
C25-C26-H26A = 109.5
C25-C26-H26B = 109.5
H26A-C26-H26B = 109.5
C25-C26-H26C = 109.5
H26A-C26-H26C = 109.5
H26B-C26-H26C = 109.5
C5-N1-C1-C2 = 1.47(19)
C5-N1-C1-C7 = -173.03(11)
N1-C1-C2-C3 = -0.3(2)
C18-N3-C14-C15 = 0.95(19)
C18-N3-C14-C20 = -174.78(11)
N3-C14-C15-C16 = 1.8(2)
C7-C1-C2-C3 = 174.02(12)
C1-C2-C3-C4 = -1.4(2)
C20-C14-C15-C16 = 177.45(12)
C14-C15-C16-C17 = -2.3(2)
C15-C16-C17-C18 = 0.1(2)
C14-N3-C18-C17 = -3.28(18)
C14-N3-C18-C19 = 175.70(11)
C16-C17-C18-N3 = 2.8(2)
C2-C3-C4-C5 = 1.8(2)
C1-N1-C5-C4 = -0.98(19)
C1-N1-C5-C6 = 178.73(11)
C3-C4-C5-N1 = -0.6(2)
C3-C4-C5-C6 = 179.67(13)
N1-C1-C7-O1 = 153.09(13)
C2-C1-C7-O1 = -21.67(19)
N1-C1-C7-C8 = -23.48(17)
C2-C1-C7-C8 = 161.76(12)
C12-N2-C8-C9 = 1.8(2)
C12-N2-C8-C7 = -175.30(12)
O1-C7-C8-N2 = 123.04(14)
C16-C17-C18-C19 = -176.11(13)
N3-C14-C20-O2 = 140.14(13)
C15-C14-C20-O2 = -35.83(19)
N3-C14-C20-C21 = -39.05(16)
C15-C14-C20-C21 = 144.98(12)
C25-N4-C21-C22 = 1.17(18)
C25-N4-C21-C20 = -175.78(11)
O2-C20-C21-N4 = 141.12(13)
S3

ACCEPTED MANUSCRIPT
C1-C7-C8-N2 = -60.36(16)
O1-C7-C8-C9 = -54.21(18)
C1-C7-C8-C9 = 122.39(14)
N2-C8-C9-C10 = 0.8(2)
C14-C20-C21-N4 = -39.68(16)
O2-C20-C21-C22 = -35.98(18)
C14-C20-C21-C22 = 143.22(12)
N4-C21-C22-C23 = 1.18(19)
C20-C21-C22-C23 = 178.04(12)
C21-C22-C23-C24 = -2.07(19)
C22-C23-C24-C25 = 0.7(2)
C7-C8-C9-C10 = 177.80(13)
C8-C9-C10-C11 = -2.7(2)
C9-C10-C11-C12 = 2.2(2)
C8-N2-C12-C11 = -2.38(19)
C8-N2-C12-C13 = 178.57(12)
C10-C11-C12-N2 = 0.4(2)
C10-C11-C12-C13 = 179.43(14)
C21-N4-C25-C24 = -2.62(18)
C21-N4-C25-C26 = 178.13(11)
C23-C24-C25-N4 = 1.7(2)
C23-C24-C25-C26 = -179.05(13)
Table S2
Geometrical parameters (Å, °) for compound 3
Br1-C6 = 1.972(2)
N1-C5 = 1.339(3)
N1-C1 = 1.340(3)
N2-C12 = 1.345(3)
N2-C8 = 1.348(3)
O1-C7 = 1.219(3)
C1-C2 = 1.393(4)
C1-C7 = 1.514(3)
C2-C3 = 1.392(4)
C2-H2 = 0.9500
C3-C4 = 1.378(4)
C3-H3 = 0.9500
C4-C5 = 1.399(3)
C4-H4 = 0.9500
C5-C6 = 1.495(3)
C6-H6A = 0.9900
C6-H6B = 0.9900
C7-C8 = 1.502(4)
C8-C9 = 1.391(4)
C9-C10 = 1.384(4)
C9-H9 = 0.9500
C10-C11 = 1.380(4)
C10-H10 = 0.9500
C11-C12 = 1.392(4)
C11-H11 = 0.9500
C12-C13 = 1.503(4)
C13-H13A = 0.9800
C13-H13B = 0.9800
C13-H13C = 0.9800
C5-N1-C1 = 117.6(2)
C12-N2-C8 = 117.7(2)
N1-C1-C2 = 123.6(2)
N1-C1-C7 = 114.5(2)
C2-C1-C7 = 121.8(2)
C3-C2-C1 = 118.2(2)
C3-C2-H2 = 120.9
C1-C2-H2 = 120.9
C4-C3-C2 = 118.8(2)
C4-C3-H3 = 120.6
C2-C3-H3 = 120.6
C3-C4-C5 = 119.2(2)
C3-C4-H4 = 120.4
C5-C4-H4 = 120.4
O1-C7-C1 = 119.9(2)
C8-C7-C1 = 119.8(2)
N2-C8-C9 = 123.7(2)
N2-C8-C7 = 117.4(2)
C9-C8-C7 = 118.9(2)
C10-C9-C8 = 118.1(3)
C10-C9-H9 = 120.9
C8-C9-H9 = 120.9
C11-C10-C9 = 118.7(2)
C11-C10-H10 = 120.7
C9-C10-H10 = 120.7
C10-C11-C12 = 120.2(3)
C10-C11-H11 = 119.9
C12-C11-H11 = 119.9
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ACCEPTED MANUSCRIPT
N1-C5-C4 = 122.5(2)
N1-C5-C6 = 116.2(2)
C4-C5-C6 = 121.3(2)
C5-C6-Br1 = 111.04(17)
C5-C6-H6A = 109.4
Br1-C6-H6A = 109.4
C5-C6-H6B = 109.4
Br1-C6-H6B = 109.4
H6A-C6-H6B = 108.0
O1-C7-C8 = 120.3(2)
N2-C12-C11 = 121.7(2)
N2-C12-C13 = 116.5(2)
C11-C12-C13 = 121.8(2)
C12-C13-H13A = 109.5
C12-C13-H13B = 109.5
H13A-C13-H13B = 109.5
C12-C13-H13C = 109.5
H13A-C13-H13C = 109.5
H13B-C13-H13C = 109.5
C5-N1-C1-C2 = -1.1(4)
C5-N1-C1-C7 = -177.7(2)
N1-C1-C2-C3 = -2.0(4)
C7-C1-C2-C3 = 174.3(2)
C1-C2-C3-C4 = 2.3(4)
C2-C3-C4-C5 = 0.4(4)
C1-N1-C5-C4 = 4.0(4)
C1-N1-C5-C6 = -173.5(2)
C3-C4-C5-N1 = -3.7(4)
C3-C4-C5-C6 = 173.7(2)
N1-C5-C6-Br1 = -83.4(2)
C4-C5-C6-Br1 = 99.1(2)
N1-C1-C7-O1 = 33.9(3)
C2-C1-C7-O1 = -142.8(2)
N1-C1-C7-C8 = -146.9(2)
C2-C1-C7-C8 = 36.5(3)
C12-N2-C8-C9 = 0.1(4)
C12-N2-C8-C7 = 178.7(2)
O1-C7-C8-N2 = -155.2(2)
C1-C7-C8-N2 = 25.6(3)
O1-C7-C8-C9 = 23.5(4)
C1-C7-C8-C9 = -155.8(2)
N2-C8-C9-C10 = -0.6(4)
C7-C8-C9-C10 = -179.1(2)
C8-C9-C10-C11 = 0.4(4)
C9-C10-C11-C12 = 0.2(4)
C8-N2-C12-C11 = 0.4(4)
C8-N2-C12-C13 = -179.8(2)
C10-C11-C12-N2 = -0.6(4)
C10-C11-C12-C13 = 179.7(3)
S5