Crystal structures and solution spectroscopy of lophine derivatives

Article abstract of DOI:10.1016/j.molstruc.2008.07.003

Lophine (2,4,5-triphenylimidazole) derivatives were synthesized and their physicochemical properties were determined. Spectroscopic and fluorescence behavior of lophine derivatives in methanol at different pH and various solvents were presented. The observed spectroscopic features in the solution are determined by specific interactions of the NH hydrogen. These kinds of interactions are manifested both in the solid state and in solution. The crystal and molecular structures of lophine derivatives with different solvents of crystallization are presented and discussed. In all solvates the solvent molecules link host molecules through hydrogen bonds.

Full text of DOI:10.1016/j.molstruc.2008.07.003

Journal of Molecular Structure 917 (2009) 101–109
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Crystal structures and solution spectroscopy of lophine derivatives
*
Natalya Fridman, Menahem Kaftory , Yoav Eichen, Shammai Speiser
Schulich Faculty of Chemistry, Technion – Israel Institute of Technology, Haifa 32000, Israel
a r t i c l e i n f o
a b s t r a c t
Article history:
Lophine (2,4,5-triphenylimidazole) derivatives were synthesized and their physicochemical properties
were determined. Spectroscopic and fluorescence behavior of lophine derivatives in methanol at different
pH and various solvents were presented. The observed spectroscopic features in the solution are deter-
mined by specific interactions of the NH hydrogen. These kinds of interactions are manifested both in
the solid state and in solution.
Received 13 May 2008
Received in revised form 1 July 2008
Accepted 7 July 2008
Available online 15 July 2008
The crystal and molecular structures of lophine derivatives with different solvents of crystallization are
presented and discussed. In all solvates the solvent molecules link host molecules through hydrogen
bonds.
Keywords:
Lophines
Fluorescence
Crystal structure
Solvates
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
substituted with electron-donating and electron-attracting groups.
MeO- and OH-groups release electrons and activate the ring. In con-
Recently, heterocyclic imidazole derivatives have attracted
considerable attention because of their unique optical properties
[1–3]. These compounds play a very important role in chemistry
as mediators for synthetic reactions, primarily as a means for pre-
paring functionalized materials [4–8]. Imidazole nucleus forms the
main structure of some well-known components of human organ-
isms, i.e. the amino acid histidine, viamin B12, a component of DNA
base structure, purines, histamine and biotin. It is also present in
structure of many natural or synthetic drug molecules, i.e. azomy-
cin, cimetidine and metronidazole [9]. Lophine derivatives have
significant analytical applications utilizing their fluorescene and
chemiluminescence properties [10,11].
Recently, we have studied the crystal structure and thermo-
chromic properties of some nitro-lophine derivatives that form
inclusion compounds with hydrogen-donating or -accepting guest
molecules [12]. We could not study proton transfer in these deriv-
atives, because these are non-fluorescent compounds. The present
work is motivated by our efforts to combine solid state studies
with solution spectroscopy investigations of lophine derivatives
that address the same type of hydrogen bonding interactions.
trast, COOH- and CN-groups withdraw electrons and deactivate the
ring. In this paper we discuss the spectroscopic and fluorescence
behavior and the crystal and molecular structures of lophine
derivatives.
2. Experimental section
Commercially available reagents were purchased from Aldrich
and used without further purification. The molecules 1–24 were
synthesized according to the method of Davidson [13] and were
characterized by 1H NMR. Some of the compounds were crystal-
lized with molecules of solvents.
2.1. Synthesis
Benzil or 4,40-dimethoxybenzil or 4,40-dimethylbenzil (1 mmol),
suitable benzaldehyde (1 mmol), and ammonium acetate (1.2 g)
were dissolved in boiling glacial acetic acid (16 ml) and refluxed
for 3–4 h monitored by TLC. The reaction mixture was poured into
icewater and collected on a filter, washed by cold water, dried and
recrystallized from the suitable solvents (MeOH, EtOH, EtOAc,
(CH3)2CO, CH3COOH). The compounds were obtained in 50–80%
yield.
For this purpose we prepared
a number of fluorescent
compounds based on lophine (2,4,5-triphenylimidazole) (1) (see
Scheme 1) skeleton substituted at the ortho, meta and para posi-
tions of the 2-phenyl ring and p-phenyl, p-tolyl, and p-anisyl rings
in the 4- and 5-aryl rings according to slightly modified procedure
of Davidson et al. [13]. We have chosen to study lophine derivatives,
Lophine (2,4,5-triphenylimidazole) derivatives form solvates
with various solvent molecules. Crystallization of 4-(4,5-diphe-
nyl-1H-imidazole-2-yl)benzoic acid
2
from solution of
ethanol:benzene (1:1) yields solvated colorless prism with the
host–guest ratio of (1:1 ethanol). Crystallization of benzonitrile,
3-[4,5-bis(4-methoxyphenyl)-1H-imidazole-2-yl] 9, from acetone
* Corresponding author. Tel.: +972 4 8293761; fax: +972 4 8295703.
E-mail address: kaftory@tx.technion.ac.il (M. Kaftory).
0022-2860/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2008.07.003

102
N. Fridman et al. / Journal of Molecular Structure 917 (2009) 101–109
Scheme 1.
yields solvated colourless prism with the host–guest ratio of (1:1).
Crystallization of 4,5-bis(4-methoxyphenyl)-2-phenylimidazole 16
from acetic acid yields solvated light yellow plate with the
host–guest ratio of (1:1 AcOꢀ:H2O). Non-solvated lophine deriva-
tives (4, 5, 6, 10, 17) form from solution of methanol:chloroporm.
Crystallization of phenol, 4-(4,5-diphenyl-1H-imidazole-2-yl) 19
from ethyl acetate yields solvated colorless plate with the
host–guest ratio of (1:1). Crystallization of phenol, 2-[4,5-bis(4-
methoxyphenyl)-1H-imidazole-2-yl] 20, from solution of metha-
nol:chloroform (1:1) yields solvated colorless needle with the
host–guest ratio of (1:1 methanol). Crystallization of phenol, 4-
[4,5-bis(4-methylphenyl)-1H-imidazole-2-yl] 22 from ethanol
yields solvated colorless plate with the host–guest ratio of (1:1).
Crystallization of 2-[2,20-bithiophen]-5-yl-(4,5-diphenyl)-1H-
imidazole 24 from solution of ethyl acetate:n-hexane (1:1) yields
non-solvated yellow needles.
2.3. Solution spectroscopy
Absorption spectra were recorded on a Cary 50 UV–Vis spectro-
photometer. Emission and excitation spectra were measured using
a Perkin-Elmer LS 50-B spectro-fluorimeter. For emission and exci-
tation measurements, the sample concentration was maintained at
ꢁ10ꢀ5M. Spectroscopic grade solvents were used for spectral mea-
surement, without further purification. Fluorescence quantum
yield was measured by comparison to lophine (1) which was used
as a reference; it has a quantum yield, Uf, of 0.27 in methanol [19].
Table 1
Absorption and fluorescence data of (1–24) in MeOH
Compounds
kmax (nm)
k(ex)
(nm)
k(em)max (nm)
D
E (cm)ꢀ1 Uf
max
1
2
3
4
5
6
7
8
311.5
312
322
339
346
354
308
315
327
307
300
305
299
300
295
301
316
300
295
320
300
295
317
365
311.5
328.5
338
345
351
360
323
329
344
313
313
312
320
317
315
312
324
313
311
330
317
311
325
369.5
386.5
414.5
447
435
447
473
440
453
478
375
379
395
392
399
389
397
432
380
400
430
399
395
391
454
6229.5
6315.9
7214.4
5997.0
6118.7
6636.1
8232.5
8320.1
8149.3
5282.2
5563.7
6734.8
5739.8
6483.1
6039.1
6862.4
7716.0
5633.1
7154.3
7047.2
6483.1
6837.9
5193.8
5037.2
0.27
0.48
0.42
0.52
0.59
0.60
0.20
0.17
0.06
0.29
0.28
0.18
0.27
0.25
0.20
0.36
0.25
0.24
0.18
0.28
0.25
0.20
0.39
0.24
2.2. Crystal structure determination and refinement
Details of crystallographic data collection and crystal structure
determination for 12 compounds are given in Tables 4–6. All
non-hydrogen atoms of the compounds were refined isotropically.
The diffraction intensities were collected with a Nonius KappaCCD
diffractometer. The software programs used for data collection and
reduction were KappaCCD [14] and DENZO SMN [15] for structure
solution and refinement SHELXS-97 and SHELXL-97 [16] and for
graphic presentations Mercury 1.4.1 for Windows. CCDC 622288–
622299 contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge via www.ccdc.
ac.uk/conts/retrieving.html (or from the Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax
+44 1223 336033). Liu et al. [17] published new crystal structure
of compound 6 and Yashuda and Kimoto [18] published new crys-
tal structure of compound 17 during the preparation of this article
for publishing, it is satisfying to note that our measured structures
are the same.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24

N. Fridman et al. / Journal of Molecular Structure 917 (2009) 101–109
103
Table 2
Excitation
Emission
Absorption and fluorescence data of 10 and 17 in MeCN and MeOH
1000
800
600
400
200
0
4
5
6
Compounds Solvent kmax
k(ex)max
(nm)
k(em)max
(nm)
D
E,cmꢀ1 Uf
(nm)
10
17
MeCN
MeOH
MeCN
MeOH
313
307
317
316
319
313
325
324
381
375
447
432
5101.2
5282.2
8397.9
7716.0
0.28
0.29
0.19
0.25
The dependence of the absorption spectra of compounds 10 and
17 on the pH was measured by adding diluted solutions of HCl and
NaOH to MeCN.
250
300
350
400
450
500
550
Wavelength, nm
Fig. 1. Excitation and fluorescence spectra of 4–6 in MeOH solution: green 4; red 5;
blue 6. (For interpretation of the references to color in this figure legend, the reader
is referred to the web version of this paper.)
3. Results and discussion
3.1. Solution spectroscopy
The fluorescent behavior of the lophine derivatives has been
measured in two solvents which have significantly different polar-
ity: methanol and acetonitrile. Absorption band maxima kmax, the
excitation spectra band maxima k(ex)max, the emission band max-
0.2
ima k(em)max and the associated Stokes shift
DE, together with the
fluorescence quantum yields, are presented in Table 1. The excita-
tion and emission wavelengths were blue shifted in methanol
compared to that observed in non-protonated solvent, e.g. acetoni-
trile. Fluorescence quantum yields of the lophine derivatives were
approximately the same in both solvents. Compounds 4–6 having
a para-CN group showed high fluorescence intensities, while those
having a MeO- and OH-groups gave almost the same intensities as
for non-substituted lophine.
The para CN-substituted lophine derivatives exhibit red shifted
absorption and emission as compared to the meta CN-substituted
lophine derivatives. Both emit at almost the same wavelength. In
case of para substituted 4- and 5-aryl rings and 2-para and meta
CN phenyl rings (compounds 4–6): k(ex)max,k(ex)max increase from
p-phenyl to p-tolyl and p-anisyl rings (see Fig. 1). Stokes shift of the
para CN-lophine derivatives increasing from p-phenyl to p-tolyl
and p-anisyl rings due to increasing dipole moment. The same
behavior has been observed for para COOH-substituted lophine
0.15
17
19
18
0.1
0.05
0
230
280
330
380
Wavelength, nm
Fig. 2. Excitation and fluorescence spectra of 17–19 in MeOH solution: green 17
(ortho); red 18 (meta); blue 19 (para). (For interpretation of the references to color
in this figure legend, the reader is referred to the web version of this paper.)
0.25
0.2
0.2
0.15
0.1
0.15
0.1
0.05
0
0.05
0
230
255
280
305
330
355
380
230
255
280
305
330
355
Wavelength, nm
Wavelength, nm
pH=3.5
pH=12.93
pH=2
pH=0.86
pH=4.33
pH=3.07
pH=0.59
pH=1.1
pH=1.7
pH=12.72
pH=0.8
pH=8.85
pH=9.54
pH=2.58
pH=5.61
pH=7.69
pH=13.57
Fig. 3. Absorption spectra of 10 (left) and 17 (right) at different apparent pH meter readings, in C ꢁ 10ꢀ5 M MeCN solution.

104
N. Fridman et al. / Journal of Molecular Structure 917 (2009) 101–109
Excitaition
Emission
1000
800
600
400
200
0
Excitaion
Emission
1000
800
600
400
200
0
250
300
350
400
450
500
550
250
300
350
400
450
500
Wavelength, nm
Wavelength, nm
pH=0.86
pH=4.33
pH=2
pH=3.07
pH=1.1
pH=1.7
pH=9.54
pH=3.5
pH=0.59
pH=0.8
pH=3.96
pH=13.57
pH=7.69
pH=2.58
pH=12.93
pH=8.85
pH=12.72
Ph2-o-OH in
different pH
1000
800
600
400
200
0
230
330
430
530
Wavelength, nm
pH=0.8 ex
pH=0.59 em
pH=1.1 em
pH=2.58 em
pH=0.59 ex
pH=1.1 ex
pH=2.58 ex
pH=0.8 em
pH=1.7 em
pH=1.7 ex
pH=3.96 em
pH=9.54 em
pH=13.57 em
pH=3.96 ex
pH=9.54 ex
pH=7.69 em
pH=12.72 em
pH=7.69 ex
pH=12.72 ex
pH=13.57 em
Fig. 4. Excitation and fluorescence spectra of 10 (left) and 17 (right) in C ꢁ 10ꢀ5 M MeCN solution.
2.70
3.30
3.28
3.25
2.60
2.50
2.40
2.30
2.20
2.10
2.00
10
17
3.23
3.20
3.18
3.15
10
17
0
2
4
6
8
10
12
14
0
2
4
6
8
10
12
14
pH
pH
Fig. 5. Transition energies of absorption (
references to colour in this figure legend, the reader is referred to the web version of this paper.)
m
a) (left) and emission (
m
f) (right) versus pH for 10 (blue) and17 (red) in C ꢁ 10ꢀ5 M MeCN solution.(For interpretation of the

N. Fridman et al. / Journal of Molecular Structure 917 (2009) 101–109
105
derivatives. The quantum yield of meta CN-substituted lophine
derivatives is significantly smaller than for para CN-substituted lo-
phine analogs. In contrast to CN- and COOH-2-phenyl-substituted
lophine derivatives the excitation and emission wavelengths for
MeO- and OH-2-phenyl-substituted lophine derivatives were blue
shifted. The MeO- and OH-2-phenyl-substituted lophine deriva-
tives absorb at 295–320 nm and emit at 375–432 nm.
In the case of para substituted 4- and 5-aryl rings and 2-MeO-
and OH-phenyl rings, the fluorescence quantum yields decreases
from ortho to meta and para positions. The k(ex)max,k(ex)max and
the Stokes shift of the para substituted 4- and 5-aryl rings and 2-
MeO and OH substituted lophine derivatives is increasing from
p-phenyl to p-tolyl and p-anisyl rings. The excitation and emission
spectra of OH-2-phenyl lophine derivatives 17–19 substituted in
ortho,meta and para positions are presented in Fig. 2. The fluores-
cence quantum yield of OH-2-phenyl substituted lophine deriva-
tically the same independent of the polarity. This may indicate that
specific interactions play the major role in these solvents. The com-
mon feature of these solvents is the presence of a lone pair of elec-
trons, which can form an H-bond with the N–H group of compound
1. This assumption is supported by our previous observations in ni-
tro derivatives of lophine where the N–H group is replaced by N–
Me. In acetic acid, the red shift of the emission may be the result
of the excited state protonation [20].
We checked the halochromic behavior of lophine derivatives 2-
(2-methoxyphenyl)-4,5-diphenylimidazole 10 and 2-(2-hydroxy-
phenyl)-4,5-diphenyl-imidazole 17 with varying pH in acetonitrile
and methanol solution. Both compounds showed halochromic
behavior at different pH. The absorption, excitation and fluores-
cence spectra of 10 and 17 in acetonitrile solution are presented
in Figs. 3 and 4. In case of a very acidic acetonitrile solution for
10 (pH = 0.86) and for 17 (pH = 0.56) the absorbance band ob-
served at kmax(ex) = 321 nm and kmax(ex) = 323 nm, respectively,
whereas in case of very basic acetonitrile solution for 10
(pH = 12.93) it stayed constant and for 17 (pH = 13.57) the absorp-
tion band is red shifted to kmax(ex) = 327 nm. The fluorescence
quantum yield gradually decreases for 17 with increasing pH and
remains unchanged for compound 10. In case of 17 the wave-
lengths of maximum excitation and emission in basic solution
shifted to longer wavelengths compared with those obtained in
neutral solution, which may be caused by the formation of anions
of lophine derivative. The fluorescence band maximum for 10 and
tives decrease from ortho,meta and para. The large
DE value of
2-ortho-MeO 17 is indicative of intramolecular proton transfer
(ESIPT) in the polar protic media. The fluorescence quantum yield
for a series of 2-phenyl-substituted rings for ortho and meta
lophine derivatives varies in the order: OMe ꢁ OH > CN and for
para lophine derivatives: CN > COOH > OMe ꢁ OH.
Absorption band maxima kmax, the excitation spectra band max-
ima k(ex)max, the emission band maxima k(em)max and the associ-
ated Stokes shift
DE together with the quantum yields for 10 and
17 in MeCN are presented in Table 2. The excitation and emission
wavelengths were blue shifted in methanol compared to that ob-
served in the non-polar solvent, e.g. acetonitrile for both com-
pounds. The fluorescence quantum yields and the associated
values for 10 are approximately the same in both solvents. For
17 the quantum yield was larger in polar solvent and E was larger
DE
D
in the non-polar solvent. We have attempted to correlate the ob-
served solvent shifts with some polarity parameters such as
ET(30) but could not find any significant correlation [20]. This is
not surprising since the solvent effects for these bisimidazole
derivatives are a complex mixture of polarity effects as well as
more specific interactions such as hydrogen bonding and the acid-
ity correlated with the –NH proton. Unfortunately these com-
pounds do not dissolve in non-polar solvent such as hexane or
cyclohexane, which usually can provide the reference point for
the discussion of solvatochromism. The excitation and emission
spectra in all solvents except chloroform and acetic acid are prac-
Fig. 6. Hydrogen bonding scheme in the crystal structure of 4.
Me
Me
O
H
O
N +
N
+
+
-H
+H
N
H
N
H
+
10
+
[10+H ]
H
-
H
O
O
H
O
N+
N
N
N
N
+
+
+
-H
-H
+H
+
+H
N
H
H
H
-
+
[17-H ]
+
17
+
[17+H ]
Scheme 2.

106
N. Fridman et al. / Journal of Molecular Structure 917 (2009) 101–109
for 17 is observed at kmax(em) = 392 nm and kmax(em) = 383 nm at
very acidic solution, respectively, whereas at kmax(em) = 383 and
kmax(em) = 479 nm at very basic solution, respectively. One isos-
bestic point observed at 276 nm for 10 and two isosbestic point
at 286 and 314 nm found for 17. Fig. 5 represents the maxima of
that crystallize without solvent molecules (4–6, 10, 24, 17), and
those that crystallize with solvent molecules (2, 9, 16, 19, 20, 22).
In the first group, compounds 4–6 are identical except for the
substituent at the para position of the phenyl rings at 4 and 5 posi-
tions (Scheme 1) (H, Me, or OMe). The three compounds are iso-
morphous; having the same space group and very similar unit
cell dimensions. The five compounds (4–6, 10, 24) have similar
hydrogen bonding scheme (Fig. 6, Figures S4–S6). The molecules
are linked to each other through hydrogen bonds (Table 3) of the
type NH. . .N between the imidazole rings of neighbor molecules
forming infinite one-dimensional chain. It should be noted that
in the crystal structures of the five compounds there are no other
hydrogen bonds and the packing is therefore determined by the
formation of chains with van der Waals intermolecular interac-
tions. There are two crystallographic independent molecules of
24, one of them is disordered. The two molecules are also differing
significantly by the rotation angle of the bithiophene moiety rela-
tived to the plane of the imidazole ring (6.0° and 26.8°). The best
molecular fit is shown in Fig. 7. The crystal structure of compound
17 is different due to the presence of hydroxyl group at an ortho
position of the phenyl of position 2 of the imidazole ring. As a re-
sult, there are intramolecular hydrogen bonds between the hydro-
gen atom of the hydroxyl group and N atom of the imidazole ring
(Fig. 8). The hydroxyl group is also serving as a connector between
neighbor molecules via hydrogen bond. There are two crystallo-
graphic independent molecules in the asymmetric unit. The intra-
molecular hydrogen bond distances are given in Table 3.
the absorption (ma) and emission (mf) transitions of 10 and 17 in
acetonitrile as a function of pH. These spectra are indicative of sev-
eral acid–base equilibria that are possible in these systems (See
also Scheme 2). Moving from acidic to basic environment 17 exists
as the neutral species in the ground state at the range 0 6 pH 6 13,
forming [17–H+]ꢀ as revealed from its absorption spectra at
pH P 13. In contrast, in the excited state, 17 acts as a photoacid
that protonates at pH < 1, forming [17 +;H]+, and deprotonates at
pH P 13, forming [17ꢀH+]ꢀ as revealed from its emission spec-
trum. Comparing systems 17 with 10, a system that lacks the phe-
nolic proton, one can clearly see that the deprotonation step of 10
at around pH = 4 is almost identical to the deprotonation step of
17. This process is attributed to the formation of the neutral spe-
cies 10 out of the protonated system [10 + H+]+. Scheme 2 depicts
the proposed acid-base processes for 10 and 17. All the above phe-
nomena are similar to other proton transfer driven systems [21].
3.2. Crystallography
The molecular conformations of the various lophine derivatives
are very similar. The conformation may be defined by three rota-
tion angles marked as
at 4 and 5 positions are rotated in the same sense (the rotation
of angles and b ranges from 21.2 to 57.1°). The rotation angle
a, b, c in Scheme 1. The two phenyl rings
The second group consists of compounds that crystallize with
solvent molecules and form solvates. The number of acceptors
and donors for hydrogens in the solvent molecules determines
the crystal structures. The six solvates can be divided into two
a
c
is varied from 5.1 to 27.7° (Overlay of molecular structures is given
in Figures S1–S3 of the supplement materials). Although the differ-
ences are significant, the barrier to rotation is small and the rota-
tion can easily be a result of substituent or as a result of packing.
The crystal structure of the 12 compounds 2, 4–6, 9, 10, 16,17,
19, 20, 22, 24 may be divided into two classes; those compounds
Table 4
Crystallographic data and parameters for compounds 2, 4, 5 and 6
Parameters
2
4
5
6
Formula
Mr
C22H16N2Oꢀ2C2H6O C22H15N3
C24H19N3
349.42
Colorless
plate
C24H19N3O2
381.42
Yellow plate
Table 3
Geometry of hydrogen bonds
386.44
321.37
colorless
plate
Crystal color, habit Colorless prism
Compounds D–Hꢂ ꢂ ꢂA
d(D–H) d(Hꢂ ꢂ ꢂA) d(Dꢂ ꢂ ꢂA)
h(D–Hꢂ ꢂ ꢂ A)
(°)
(Å)
(Å)
(Å)
Crystal system Monoclinic
Orthorhombic Orthorhombic Orthorhombic
Crystal size (mm) 0.54 ꢃ 0.36
ꢃ 0.24
0.30 ꢃ 0.15
ꢃ 0.06
Pbca
8.875(2)
16.811(3)
23.825(5)
90
0.48 ꢃ 0.38
ꢃ 0.06
Pbca
9.042(2)
16.722(3)
25.791(5)
90
0.30 ꢃ 0.27
ꢃ 0.06
Pbca
9.806(2)
15.588(3)
26.201(5)
90
2
4
N1–H1N1ꢂ ꢂ ꢂ O2
0.86
0.82
0.82
0.86
1.95
2.04
1.77
2.13
2.784(2)
2.856(2)
2.580(2)
2.877(3)
163
177
169
144
O3–H3ꢂ ꢂ ꢂ N2
O1–H1ꢂ ꢂ ꢂ O3
N1–H1N1ꢂ ꢂ ꢂ N2
Space group
a (Å)
P21/c
11.470(2)
12.450(2)
15.720(3)
90
b (Å)
c (Å)
5
6
9
10
N1–H1N1ꢂ ꢂ ꢂ N2
N1–H1N1ꢂ ꢂ ꢂ N2
N1–H1N1ꢂ ꢂ ꢂ N2
N1–H1N1ꢂ ꢂ ꢂ O1
N1–H1N1ꢂ ꢂ ꢂ N2
N1–H1ꢂ ꢂ ꢂ O1S
N2–H2ꢂ ꢂ ꢂ O1W
O1W–H1W. . . O2S
N1A–H1NAꢂ ꢂ ꢂ O1B
0.92
0.86
0.86
0.86
0.82
0.86
0.86
0.91
0.86
2.05
2.48
2.10
2.29
2.49
2.04
2.06
2.36
1.95
2.881(2)
3.102(3)
2.958(16) 172
2.737(2)
3.314(2)
2.817(3)
2.923(3)
2.922(3)
2.809(2)
149
149
a
(°)
b (°)
113.32(2)
90
2061.5(7)
4
1.245
0.083
816
90
90
90
90
90
90
112
162
149
175
120
176
c
(°)
V (Å3)
3554.6(13)
8
1.201
0.072
1344
3899.61(14) 4005.0(14)
8
16
17
Z
8
Dcalcd. (g cmꢀ3
)
1.190
0.071
1472
50.1
6442
1.265
0.082
1600
50.1
5880
l
(MoK ) (cmꢀ1
)
a
F(000)
2hmax (°)
50.1
47.7
9333
N1B–H1NBꢂ ꢂ ꢂ O1A
O1B–H1OBꢂ ꢂ ꢂ N2B
0.86
0.82
1.97
2.832(2)
174
Reflections
collected
Independent
reflections
6842
1.78
1.76
2.08
2.530(2)
2.516(2)
2.931(3)
151
152
172
3637
2734
3448
3358
O1A–H1OAꢂ ꢂ ꢂ N1B 0.82
19
20
N1–H1N1ꢂ ꢂ ꢂ O1S
0.86
Largest difference 0.287
peak (e Åꢀ3
Largest difference ꢀ0.205
hole (e Åꢀ3
0.086
ꢀ0.086
0.128
ꢀ0.163
0.188
ꢀ0.168
)
O1–H1O1ꢂ ꢂ ꢂ N2
N2–H2N2ꢂ ꢂ ꢂ O1S
0.82
0.86
1.96
2.04
2.780(3)
2.889(2)
174
160
)
No. of parameters 276
228
337
277
O1S–H1Sꢂ ꢂ ꢂ O1
O3–H3O3ꢂ ꢂ ꢂ N1
N2–H2N2ꢂ ꢂ ꢂ O2
O1–H1O1ꢂ ꢂ ꢂ N1
0.96
0.82
0.86
0.82
1.88
1.89
2.04
1.90
2.11
2.830(2)
2.618(2)
2.897(5)
2.719(5)
2.908(3)
171
148
175
171
154
Ra
0.0455
0.1335
0.935
0.0448
0.1310
0.953
0.0443
0.1196
0.921
0.0470
0.1010
0.794
wRa
GOFb
22
24
N2A–H2NAꢂ ꢂ ꢂ N1B 0.86
P
P
P
P
2
2 1=2
a
R ¼
j Fo j ꢀ j Fc j = j Fo j; wR ¼ ½ wðj Fo j ꢀ j Fc j Þ = w j Foj ꢄ
.
P
GOF ¼ ½ wðj Fo j ꢀ j Fc j Þ =ðNO ꢀ NVÞꢄ1=2, where NO is the number of obser-
2
b
N2B–H2NBꢂ ꢂ ꢂ N1A 0.86
2.08
2.919(3)
166
vations and NV is the number of variables.

N. Fridman et al. / Journal of Molecular Structure 917 (2009) 101–109
107
Table 5
Crystallographic data and parameters for compounds 9, 10, 16 and 17
Table 6
Crystallographic data and parameters for compounds 19, 20, 22 and 24
Parameter
Formula
9
10
16
17
Parameter
Formula
19
20
22
24
23H16N2S2
C25H19N3Oꢀ2
C2H6O
439.50
Colorless prism Colorless
needle
C22H18N2O
C23H20N2Oꢀ2C2
H4Oꢀ2H2O
434.48
C
21H16N2O
C21H16N2Oꢀ
C4H8O2
312.36
Colorless
plate
C23H20N2Oꢀ3CH4O C23H20N2Oꢀ
C2H6O
404.45
Colorless needle Colorless
plate
C
Mr
326.38
312.36
Mr
386.48
384.50
Yellow
needle
Crystal color,
habit
Light yellow plate Colorless
Crystal color, habit
plate
Crystal system
Crystal size
(mm)
Space group
a (Å)
Monoclinic
0.57 ꢃ 0.33
ꢃ 0.30
P21/9i
13.807(3)
7.365 (1)
27.088(5)
90
120.16(2)
90
2381.7(6)
4
Monoclinic Monoclinic
Triclinic
Crystal system
Crystal size (mm)
Orthorhombic Monoclinic
Monoclinic Monoclinic
0.54 ꢃ 0.30 0.54 ꢃ 0.18
0.54 ꢃ 0.15 0.48 ꢃ 0.42
0.57 ꢃ 0.45
0.33 ꢃ 0.24
ꢃ 0.18
Pbca
0.57 ꢃ 0.18
ꢃ 0.12
P21/c
ꢃ 0.12
P21/c
ꢃ 0.12
C2/c
ꢃ 0.09
ꢃ 0.09
P21/c
ꢃ 0.06
P21/c
ꢀ
P1
Space group
a (Å)
b (Å)
12.730(3)
13.490(3)
10.060(2)
90
35.716(7)
7.342(2)
21.408(4)
90
10.550(2)
12.454(3)
13.834(3)
68.67(2)
86.63(2)
85.97(2)
1687.9(6)
4
21.578(4)
9.035(2)
22.073(4)
90
10.690(2)
20.770(4)
9.790(2)
90
5.861(2)
34.301(7)
11.912(2)
90
14.981(3)
15.235(3)
18.952 (3)
90
b (Å)
c (Å)
c (Å)
a
(°)
a
(°)
b (°)
97.31(2)
90
126.16(2)
90
b (°)
90
90
104.32(2)
90
117.10(2)
90
112.98(2)
90
c
(°)
c
(°)
V (Å3)
1713.5(7)
4
4532.6(17)
8
V (Å3)
4303.3(15)
8
2106.1(7)
4
2106.1(7)
4
3989.3(2)
8
Z
Z
D
l
Dcalcd. (g cmꢀ3
)
1.226
0.081
928
1.265
0.078
688
1.273
0.089
1840
1.229
0.077
656
calcd.(g cmꢀ3
(MoK ) (cmꢀ1
)
1.236
0.082
1696
1.276
0.087
856
1.204
0.077
824
1.283
0.277
1600
l
(MoK ) (cmꢀ1
)
)
a
a
F(000)
F(000)
2hmax (°)
50.1
50.1
50.1
50.1
2hmax (°)
50.1
50.1
50.1
50.1
Reflections
collected
Independent
reflections
Largest difference 0.172
peak (e Åꢀ3
Largest difference ꢀ0.186
hole (e Åꢀ3
7066
5245
7157
5963
Reflections collected 7158
6268
3714
4937
2959
11672
6983
Independent
reflections
3812
0.353
4218
3005
4003
5963
Largest difference
0.123
0.190
0.204
0.145
ꢀ0.143
0.440
ꢀ0.370
0.195
ꢀ0.182
peak [e Åꢀ3
]
)
Largest difference hole ꢀ0.245
ꢀ0.138
ꢀ0.219
ꢀ0.311
[e Åꢀ3
]
)
No. of parameters
290
290
282
507
No. of parameters 322
228
289
464
Ra
0.0491
0.1472
0.888
0.0385
0.1012
0.892
0.0476
0.1438
0.739
0.0455
0.1108
0.764
Ra
0.0380
0.0923
0.867
0.0387
0.0973
0.802
0.0627
0.2030
1.056
0.0515
0.1466
0.992
wRa
GOFb
wRa
GOFb
P
P
P
P
2
2
1=2
a
R ¼
j Fo j ꢀ j Fc j = j Fo j; wR ¼ ½ wðj Fo j ꢀ j Fc j Þ = w j Foj ꢄ
.
P
P
P
P
P
2
2
1=2
2
R ¼
j Fo j ꢀ j Fc j = j Fo j; wR ¼ ½ wðj Fo j ꢀ j Fc j Þ = w j Foj ꢄ
.
GOF ¼ ½ wðj Fo j ꢀ j Fc j Þ =ðNO ꢀ NVÞꢄ1=2, where NO is the number of obser-
a
b
P
GOF ¼ ½ wðj Fo j ꢀ j Fc j Þ =ðNO ꢀ NVÞꢄ1=2, where NO is the number of obser-
vations and NV is the number of variables.
2
b
vations and NV is the number of variables.
imidazole ring (the hydrogen bond geometry is given in Table 3).
The solvent molecule is hydrogen bonded to the hydrogen donor
(HN) of the imidazole ring. Therefore the three-dimensional pack-
ing is formed by van der Waals interactions between infinite
chains made up by hydrogen bonds.
In the second subgroup the solvent molecule connects neighbor
imidazole molecules by hydrogen bonds. Thus, in 2 (Fig. 11), the
ethanol molecule is hydrogen bonded to the hydrogen acceptor
(N atom) of an imidazole ring, and to an hydroxyl group of a neigh-
bor imidazole molecule (Table 3). The hydrogen donor (HN) of the
imidazole ring is hydrogen bonded to the carboxylic oxygen of a
neighbor imidazole molecule (Table 3). The three-dimensional
main subgroups; in the first (9, 19 and 22) the solvent molecules
do not serve as connectors between neighbor imidazole rings, in
the second subgroup (2, 16 and 20) the solvent molecules serve
as connectors via hydrogen bonds between neighbor imidazole
rings. In 9 (Figure S6) the oxygen atom of the acetone molecule
is hydrogen bonded to the donor for hydrogen atoms (Table 3).
In the absence of other hydrogen bonds, the three-dimensional
packing is determined by van der Waals interactions. In 19 (Fig.
9) and 22 (Fig. 10) the imidazole molecules form chains made up
by hydrogen bonds between the para-hydroxyl group of the phenyl
(at 4-position) and the hydrogen acceptor (N atom) of the neighbor
Fig. 7. Best molecular fit of the two molecules of 24.
Fig. 8. Hydrogen bonding scheme in the crystal structure of 17.

108
N. Fridman et al. / Journal of Molecular Structure 917 (2009) 101–109
Fig. 12. Hydrogen bonding scheme in the crystal structure of 16.
Fig. 9. Hydrogen bonding scheme in the crystal structure of 19.
as connectors via hydrogen bonds between imidazole molecules,
however while in 2 an infinite chain was formed, in the former it
in resulted separated dimers (Figs. 12 and 13). The imidazole ring
in 16 is protonated and the acetic acid is deprotonated. The hydro-
gen bonding scheme is in the order acetateꢂ ꢂ ꢂ imidazoleꢂ ꢂ ꢂ waterꢂ ꢂ ꢂ
acetateꢂ ꢂ ꢂ imidazoleꢂ ꢂ ꢂ waterꢂ ꢂ ꢂ. An acetate molecule is hydrogen
bonded to the hydrogen donor (HN) of imidazole molecule (Table
3) and the water oxygen is hydrogen bonded to another hydrogen
donor (HN) of imidazole molecule (Table 3). Similar hydrogen
bonding scheme is also found in the crystal structure of 20 how-
ever, the connector of two imidazole molecules is methanol. An
intramolecular hydrogen bond is also found (as in 17). The dimers
in 16 are formed parallel to the short b axis and packed in layers
perpendicular to this axis. In 20 the layers are packed in ꢀ101
plane.
4. Conclusions
In this work we have complemented the studies of lophine
derivatives in the solid state with investigation of their spectros-
copy and their photophysical properties in solution. We have stud-
ied the crystal structures of these compounds and their inclusion
compounds. These lophine derivatives form inclusion compounds
with various guest molecules that possess hydrogen donor or
hydrogen acceptor groups. The guest molecules play a crucial role
in building up the three-dimensional structure. The guest mole-
cules link some of the host molecules through hydrogen bonds. A
single-crystal X-ray analysis of 12 crystal structures of lophine
Fig. 10. Hydrogen bonding scheme in the crystal structure of 22.
packing is formed by van der Waals interactions between infinite
chains formed by the above hydrogen bond scheme. The solvent
molecules (acetic acid:water in 16 and methanol in 20) also serve
Fig. 11. Hydrogen bonding scheme in the crystal structure of 2.

N. Fridman et al. / Journal of Molecular Structure 917 (2009) 101–109
109
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.molstruc.2008.07.003.
References
[1] J. Santos, E.A. Mintz, O. Zehnder, C. Bosshard, X.R. Bu, P. Gunter, Tetrahedron
Lett. 42 (2001) 805.
[2] X.R. Bu, H. Li, D. Van DerVeer, E. Mintz, Tetrahedron Lett. 37 (1996) 7331.
[3] H. Li, J. Santos, D. Van DerVeer, E.A. Mintz, X.R. Bu, in: T.L. Coleman, B. White, S.
Goodman (Eds.), Proceedings of the NASA URC Technical Conference, vol. III,
1998, p. 671.
[4] T. Kamidate, K. Yamaguchi, T. Segawa, H. Watanabe, Anal. Sci. 5 (1989) 429.
[5] (a) K. Nakashima, H. Yamasaki, N. Kuroda, S. Akiyama, Anal. Chim. Acta 303
(1995) 103;
(b) K. Nakashima, Biomed. Chromatogr. 17 (2003) 83.
[6] A. MacDonald, K.W. Chan, T.A. Nieman, Anal. Chem. 51 (1979) 2077.
[7] D.F. Marino, J.D. Ingle Jr., Anal. Chem. 53 (1981) 294.
[8] B.H. Lipshutz, Chem. Rev. 86 (1986) 795.
_
[9] U. Üçucu, N.G. Karaburun, I. Isßikdag˘, IL Farmaco 56 (2001) 285.
Fig. 13. Hydrogen bonding scheme in the crystal structure of 20.
[10] K. Nakashima, Y. Taguchi, N. Kuroda, S. Akiyama, G. Duan, J. Chromatogr. 19
(1993) 1.
[11] K. Yagi, C.F. Soong, M. Irie, J. Org. Chem. 66 (2001) 5419.
[12] N. Fridman, S. Speiser, M. Kaftory, Cryst. Growth Des. 6 (2006) 2281.
[13] D. Davidson, M. Weiss, M. Jelling, J. Org. Chem. 2 (1937) 319.
[14] Nonius, COLLECT, Nonius BV, Delft, The Netherlands, 2000.
[15] Z. Otwinowski, W. Minor, in: C.W. Carter Jr., R.M. Sweet (Eds.), Methods in
Enzymology, MolecularCrystallography A, vol. 276, Academic Press, New York,
1997, pp. 307–326.
derivatives has been determined and compared. Spectroscopic
behavior of 10 and 17 at different pH and various solvents were
presented. The observed spectroscopic features in the solution
are determined by specific interactions of the NH hydrogen. These
kinds of interactions are manifested both in the solid state and in
solution.
[16] G.M. Sheldrick, SHELXS-86 and SHELXL-97, University of Göttingen, Germany,
1997.
[17] X. Liu, Z. Zhong, Z. Xu, Acta Crystallogr. E61 (2005) o1976.
[18] G. Yasuda, H. Kimoto, X-ray Struct. Anal. Online 20 (2004) x59.
[19] N. Fridman, S. Speiser, M. Kaftory, Cryst. Growth Des. 6 (2006) 1653.
[20] N. Fridman, M. Kaftory, Y. Eichen, S. Speiser, J. Photochem. Photobiol. A Chem.
188 (2007) 25.
Acknowledgement
This research was supported by the Fund for the Promotion of
Research at the Technion and the Technion VPR Fund.
[21] H. Salman, S. Meltzman, S. Speiser, Y. Eichen, J. Luminescence 102 (2003) 261.