Spectroscopic, crystallographic and theoretical studies of lasalocid complex with ammonia and benzylamine

Article abstract of DOI:10.1016/j.saa.2014.01.083

A natural antibiotic - Lasalocid is able to form stable complexes with ammonia and organic amines. New complexes of lasalocid with benzylamine and ammonia were obtained in the crystal forms and studied using X-ray, FT-IR, ¹H NMR, ¹³C NMR and DFT methods. These studies have shown that in both complexes the proton is transferred from the carboxylic group to the amine group with the formation of a pseudo-cyclic structure of lasalocid anion complexing the protonated amine or NH4+ cation. The spectroscopic and DFT studies demonstrated that the structure of the complex formed between Lasalocid and benzylamine in the solid is also conserved in the solution and gas phase. In contrast, the structure of the complex formed between lasalocid and ammonium cation found in the solid state undergoes dissociation in chloroform solution accompanied with a change in the coordination form of the NH4+ cation.

Full text of DOI:10.1016/j.saa.2014.01.083

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 297–307
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Spectroscopic, crystallographic and theoretical studies of lasalocid
complex with ammonia and benzylamine
a,
b
a
a
⇑
´
Adam Huczynski , Jan Janczak , Jacek Rutkowski , Bogumil Brzezinski
a Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan´, Poland
b Institute of Low Temperature and Structure Research, Polish Academy of Sciences, PO Box 1410, 50950 Wrocław, Poland
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
The presence of band at 1684 cm–1 and 1401 cm–1 present in the FT-IR spectrum of crystalline complex
formed between ionophore antibiotic lasalocid acid and ammonia are no longer observed in chloroform
solution. This phenomenon is accompanied by a change in the coordination geometry of NHþ4 cation.
ꢀ
ꢀ
New Lasalocid complexes were
synthesized.
Lasalocid is a useful ligand for
complexation of NHþ4 and
benzylamine.
ꢀ
ꢀ
The crystal structure of the
complexes were studied.
Structures of Lasalocid complexes
were visualised using DFT method.
a r t i c l e i n f o
a b s t r a c t
Article history:
A natural antibiotic – Lasalocid is able to form stable complexes with ammonia and organic amines. New
complexes of lasalocid with benzylamine and ammonia were obtained in the crystal forms and studied
using X-ray, FT-IR, 1H NMR, 13C NMR and DFT methods. These studies have shown that in both complexes
the proton is transferred from the carboxylic group to the amine group with the formation of a pseudo-
cyclic structure of lasalocid anion complexing the protonated amine or NHþ4 cation. The spectroscopic and
DFT studies demonstrated that the structure of the complex formed between Lasalocid and benzylamine
in the solid is also conserved in the solution and gas phase. In contrast, the structure of the complex
formed between lasalocid and ammonium cation found in the solid state undergoes dissociation in chlo-
roform solution accompanied with a change in the coordination form of the NHþ4 cation.
Ó 2014 Elsevier B.V. All rights reserved.
Received 19 November 2013
Received in revised form 8 January 2014
Accepted 16 January 2014
Available online 24 January 2014
Keywords:
FT-IR
Crystal structure
Hydrogen bonds
DFT calculations
Ionophores
X-537A
Introduction
performed intensively for many years. The information gathered
help to understand better the individual contributions of different
Structural and spectroscopic studies of synthetic and natural
receptors for inorganic and organic ammonium cations have been
forces involved in ammonium cation binding [1–3]. Many types of
synthetic and natural receptors of organic ammonium ion are
available, ranging from crown ethers [1–3], cryptands [1,4], cyclo-
dextrins [5], and cyclopeptides [1,6], cucurbiturils [1,7] natural
ionophores [1,8–9]. Typical interactions observed in the complexes
⇑
Corresponding author. Tel.: +48 618291287.
E-mail address: adhucz@amu.edu.pl (A. Huczyn´ ski).
http://dx.doi.org/10.1016/j.saa.2014.01.083
1386-1425/Ó 2014 Elsevier B.V. All rights reserved.

´
A. Huczynski et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 297–307
298
of amines are ionic and dipolar interactions, dispersive forces such
as van der Waals or hydrogen bonds [1,10].
Preparation of LASðꢁÞ ꢁ BnNHð3þÞ and LASðꢁÞ ꢁ NH4ðþÞ complexes
Lasalocid acid (LASH, Scheme 1) also known as X-537A isolated
from Streptomyces lasaliensis is a well-known representative of
polyether antibiotics – highly bioactive molecule which exhibits
interesting activities such as antibacterial, antifungal, antiparasitic,
antimalarial, antiviral and anti-inflammatory [11–12]. LASH is cur-
rently used as a growth-promoting agent and as a coccidiostat in
veterinary medicine [13].
The structural studies of polyether antibiotics and their deriva-
tives together with the elucidation of their biological activity have
recently become a very important field of research. It has been
shown that some polyether antibiotics (e.g. salinomycin, monen-
sin) exhibit high activity against the proliferation of various cancer
cells, including those that display multidrug resistance (MDR) and
cancer stem cells (CSC) [14–20]. Furthermore, polyether iono-
phores are recognized as potential anticancer drugs [21,22] and
preclinical and clinical studies of their therapeutic potential are
in progress [23,24].
Lasalocid sodium salt (1.0 g, 1.70 mmol) was dissolved in
dichloromethane (150 ml) and stirred vigorously with a layer of di-
luted aqueous sulphuric acid (pH = 1.5) (100 ml). The organic layer
containing Lasalocid acid (LASH) was washed three times with dis-
tilled water. Subsequently dichloromethane was evaporated under
reduced pressure to dryness giving LASH (0.75 g; 1.27 mmol).
The crystals of 1:1 complex of LASðꢁÞ ꢁ BnNH4ðþÞ and 1:1 com-
plex of LASðꢁÞ ꢁ NHð4þÞ were obtained by crystallization from aceto-
nitrile solution using a 1:1 M ratio of LASH and benzylamine
(BnNH2) and ammonium hydroxide (NH4OH), respectively.
Mp = 179–181 °C (LASðꢁÞ ꢁ BnNH3ðþÞ) and 183–186 °C (LASðꢁÞꢁ
NHð4þÞ). Elemental Analysis: Calculated for LASðꢁÞ ꢁ BnNH3ðþÞ com-
plex (C41H63NO8): C, 70.56; H, 9.10; N, 2.01; Found:70.44; H,
9.23; N, 2.03; Calculated for LASðꢁÞ ꢁ NH4ðþÞ complex (C34H57NO8):
C,67.19; H, 9.45; N, 2.30;C, Found: C, 67.02; H, 9.66; N, 2.23.
X-ray measurements
Our previous studies have clearly demonstrated that the biolog-
ical activity of derivatives of polyether ionophores depends
strongly on their structures [25–30]. Thus, it is very important to
obtain detailed information on their structures. Recently we have
discovered that LASH is able to form stable complexes with N-
bases such as 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) [31],
1,1,3,3-tetramethylguanidine (TMG) [32] and several amines such
as allylamine [33], phenylamine and butylamine [34]. In previous
studies we have shown that the complex of LASH with allylamine
has higher antibacterial activity than pure LASH [33] and also that
LASH and its complexes with phenylamine and butylamine are rel-
atively strong cytotoxic agents towards cancer cell lines [34]. It is
interesting to note that the cytostatic activity of LASH and its com-
plexes with amines against human cancer cell lines is higher than
that of cisplatin – a standard anticancer drug [34].
Single crystal X-ray diffraction measurements of LASðꢁÞꢁ
BnNHð3þÞ (1) and LASðꢁÞ ꢁ NHð4þÞ (2) were carried out at 295 K on a
four-circle KUMA KM4 diffractometer equipped with two-dimen-
sional CCD area detector. Graphite monochromatized Mo K
a radi-
ation (k = 0.71073 Å) and -scan technique ( = 1°) were used
x
Dx
for data collection. Data collection and reduction along with
absorption correction were performed using CrysAlis software
package [35]. The structures were solved by direct methods using
SHELXS-97 [36], which revealed the positions of almost all
non-hydrogen atoms. The remaining atoms were located from
subsequent difference Fourier syntheses. The structure was refined
using SHELXL-97 [36] with the anisotropic thermal displacement
parameters. Visualizations of the structures were made with the
Diamond 3.0 program [37]. Details of the data collection
parameters, crystallographic data and final agreement parameters
are collected in Table 1.
As a continuation of these studies, we synthesized two new
hydrogen-bonded complexes of the LASH with the benzylamine
(BnNH2) and ammonia (NH3) and characterised them using X-ray
crystallography, FT-IR and NMR spectroscopy, as well as DFT
calculations.
DFT calculations
Theoretical calculations with geometry optimization of
LASðꢁÞ ꢁ BnNH3ðþÞ and LASðꢁÞ ꢁ NHð4þÞ as well as the lasalocid acid
(LASH) and its dissociated LAS(ꢁ) anion were performed with the
Gaussian03 program package [38]. All calculations were carried
out with the DFT level using the Becke3–Lee–YangParr correlation
functional (B3LYP) [39–40] with the 3-21 + Gꢂ basis set assuming
the geometry resulting from the X-ray diffraction study as the
starting structure. As convergence criterions the threshold limits
of 0.00025 and 0.0012 a.u. were applied for the maximum force
and the displacement, respectively.
Experimental
General
Lasalocid sodium salt was isolated from veterinary premix –
AvatecÒ 20 (Alpharma Inc.), which contains about 20% pure Lasalo-
cid sodium salt.
Benzylamine (BnNH2), ammonium hydroxide (NH4OH) water
solution (5.0 mol dmꢁ3) and solvents were obtained from Sigma–
Aldrich or Fluka and used without any further purification.
Spectroscopic measurements
O(1) O(2)
31
32
33
O
O
H
CH3
The 1H and 13C NMR spectra of LASH, LASðꢁÞ ꢁ BnNHð3þÞ and
LASðꢁÞ ꢁ NHð4þÞ (0.1 mol dmꢁ3) were recorded in CDCl3 solutions
using Bruker Avance 600 MHz spectrometer. All spectra were
locked to deuterium resonance of CDCl3. The 1H NMR measure-
ments were carried out at the operating frequency 600.0018 MHz
and the 13C NMR spectra at the operating frequency
150.885 MHz and temperature 298.0 K using TMS as the internal
standard in both cases. No window function or zero filling was
used. The errors of the 1H and 13C NMR chemical shift values were
0.01 ppm and 0.1 ppm, respectively. The 1H and 13C NMR signals
were assigned using 2-D (COSY, HETCOR, NOESY and HMBC). 2-D
spectra were recorded using standard pulse sequences from Bruker
pulse-sequence libraries.
H
O
CH3 CH3
1
2
30
CH3
O(3)
11
13
3
8
16
14
10
12
15
18
28
CH3
OH
O(4)
O
O
H33C4
O(5) O(6)
27
19
O
O(7)
26
CH3
23
22
H32C4
OH25
O(8)
Scheme 1. The formula and atom numbering of LASH.

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Table 1
Crystal data and refinement parameters for LASðꢁÞ ꢁ BnNHð3þÞ and LASðꢁÞ ꢁ NHð4þÞ
.
LASðꢁÞ ꢁ BnNHð3þÞ
LASðꢁÞ ꢁ NHð4þÞ
Formula
C41H63NO8
697.92
295(2)
Orthorhombic
P 212121 (No 19)
13.512(2)
C34H57NO8
607.81
295(2)
Orthorhombic
P 212121 (No 19)
12.903(2)
Molecular weight
Temperature (K)
Crystal system
Space group
0
a (AÅ)
0
13.829(2)
21.552(3)
4027.2(10)
13.567(2)
19.921(3)
3487.3(9)
b (AÅ)
0
c (AÅ)
0
V (ÅA3)
Z
4
4
Dcalc/Dexp (g cmꢁ1
Wavelength, k (Å)
)
1.151/1.15
0.71073
0.079
1.158/1.15
0.71073
0.081
l
(mmꢁ1
)
F(000)
1520
1328
Crystal size (mm3)
h range(°)
0.37 ꢄ 0.29 ꢄ 0.21
2.95–28.00
0.9731/0.9856
56,263/10,460/5247
0.0911
0.34 ꢄ 0.25 ꢄ 0.22
2.99–28.49
0.9778/0.9843
49,125/8698/4464
0.0669
Tmin/Tmax
Total/unique/Obs refls
Rint
R [F2 > 2
R
(F2)]a
0.0779
0.1161
0.0774
0.1594
wR [F2 all refls]b
Goodness-of-fit, S
1.005
0.144, ꢁ0.153
1.001
0.141, ꢁ0.148
0
D
qmax
,
D
qmin (eAÅꢁ3
)
a
R =
R
||Fo| ꢁ |Fc||/
R
Fo.
1=2
P
2
P
P
wR ¼ f ½wðF2o ꢁ F2c Þ2ꢅ= wF4o g ; wꢁ1
¼
ðF2o Þ þ ðaPÞ þ bP where P ¼ ðF2o þ
2
b
2F2c Þ=3. The a and b parameters are 0.032 and 0 for LASðꢁÞ ꢁ BnNHð3þÞ and 0.0449 and
1.2094 for LASðꢁÞ ꢁ NH4ðþÞ
.
In the mid infrared region, the FT-IR spectra of LASH,
LASðꢁÞ ꢁ NH4ðþÞ complex and LASðꢁÞ ꢁ BnNHð3þÞ complex were re-
corded in chloroform solution (0.1 mol dmꢁ3) and the FT-IR spectra
of and LASðꢁÞ ꢁ BnNHð3þÞ crystals were recorded in Nujol and
fluorolube mulls. For solutions, a cell with Si windows and
wedge-shaped layers was used to avoid interferences (mean layer
thickness 170 lm). The spectra were taken with an IFS 113v FT-IR
Fig. 1. View of the molecular structure of host–guest complexes: (a)
LASðꢁÞ ꢁ BnNHð3þÞ and (b) LASðꢁÞ ꢁ NHð4þÞ. The dashed lines represent the intra- and
intermolecular hydrogen bonds.
spectrophotometer (Bruker, Karlsruhe) equipped with a DTGS
detector; resolution 2 cmꢁ1, NSS = 64. The Happ-Genzel apodiza-
tion function was used.
Results and discussion
Table 2
Description of the crystal structure of LASðꢁÞ ꢁ NH4ðþÞ and
LASðꢁÞ ꢁ BnNHð4þÞ complexes
Comparison of the selected geometrical parameters (Å, °) of LASðꢁÞ ꢁ BnNH3ðþÞ and
LASðꢁÞ ꢁ NH4ðþÞ in the crystal and gas-phase.
LASðꢁÞ ꢁ BnNHð3þÞ
LASðꢁÞ ꢁ NHð4þÞ
Lasalocid acid molecule (LASH) contains several chiral carbon
atoms (C10R, C11S, C12S, C14R, C15S, C16S, C18S, C19R, C22R and
C23S, Scheme 1), therefore the studied here LASðꢁÞ ꢁ BnNH3ðþÞ and
LASðꢁÞ ꢁ NHð4þÞ supramolecular complexes crystallise in the non-
centrosymmetric space group P212121 of the orthorhombic system
with four molecular complexes in the unit cell (Table 1). The
molecular structure of the LASðꢁÞ ꢁ BnNHð3þÞ and LASðꢁÞ ꢁ NHð4þÞ
supramolecular host–guest complexes with the labelling scheme
is illustrated in Fig. 1a and b, respectively. The molecular dimen-
sions (bond lengths and angles, Table 2) are consistent with the
structural formula shown in Scheme 1. X-ray analysis shows that
in both complexes the carboxylic group is deprotonated, whereby
the proton from COOH of LASH is transferred to the benzylamine
or NH3 molecules forming LASðꢁÞ ꢁ BnNHð3þÞ and LASðꢁÞ ꢁ NHð4þÞ
supramolecular host–guest complexes, respectively. In the crys-
tals, all atoms of these supramolecular complexes lay in general
positions. The conformation of the LAS(ꢁ) anion is determined by
the intramolecular OAHꢃ ꢃ ꢃO hydrogen bonds (Table 3). The great
flexibility of the neutral LASH molecule and its deprotonated LAS(ꢁ)
X-ray
DFT
X-ray
DFT
C1AO1
C1AO2
C3AO3
C11AO4
C13AO5
C15AO6
C18AO6
C19AO7
1.258(4)
1.237(4)
1.356(4)
1.431(4)
1.214(4)
1.431(3)
1.461(3)
1.436(3)
1.435(3)
1.438(4)
1.470(4)
122.3(4)
ꢁ18.3(5)
ꢁ74.2(4)
ꢁ58.9(4)
41.9(4)
1.312
1.289
1.358
1.465
1.242
1.496
1.502
1.471
1.474
1.471
1.516
120.54
6.03
ꢁ88.02
ꢁ54.50
64.34
76.50
71.05
64.65
71.76
1.276(4)
1.234(4)
1.347(4)
1.430(5)
1.221(4)
1.443(4)
1.456(4)
1.432(4)
1.443(4)
1.438(4)
–
123.5(4)
ꢁ5.5(5)
ꢁ84.4(5)
ꢁ54.9(5)
51.0(5)
74.4(4)
66.9(4)
66.2(4)
–
1.315
1.288
1.357
1.469
1.240
1.495
1.502
1.472
1.478
1.469
–
C23AO7
C22AO8
C35AN1
O1AC1AO2
O1AC1AC2AC3
C2AC7AC8AC9
C9AC10AC11AO4
C11AC12AC13AO5
C13AC14AC15AO6
O6AC18AC19AO7
O7AC23AC22AO8
N1AC35AC36AC37
120.53
4.38
ꢁ86.32
ꢁ56.89
58.04
77.30
71.35
64.38
–
69.2(3)
74.9(3)
63.8(4)
83.3(5)

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A. Huczynski et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 297–307
300
Table 3
bonds. The first of the hydrogen bonds, i.e. O8AHꢃ ꢃ ꢃO1 hydrogen
bond links the terminal hydroxyl group at C(22) with the carboxyl-
ate group (Fig. 1a and b). This head-to-tail hydrogen bond con-
strains the LAS(ꢁ) anion into a pseudo-cyclic structure, while the
second O4AHꢃ ꢃ ꢃO2 hydrogen bond is responsible for stabilization
of this pseudo-cyclic conformation. In addition, the intramolecular
O3AHꢃ ꢃ ꢃO1 hydrogen bond is very short most likely due to the
overcrowding effect of the two adjacent substituents in a rigid
Hydrogen bonding geometry (Å, °) in the crystal of LASðꢁÞ ꢁ BnNH3ðþÞ and
LASðꢁÞ ꢁ NHð4þÞ
DAHꢃ ꢃ ꢃA
.
DAH
Hꢃ ꢃ ꢃA
Dꢃ ꢃ ꢃA
DAHꢃ ꢃ ꢃA
(a) LASðꢁÞ ꢁ BnNHð3þÞ
O3AHꢃ ꢃ ꢃO1
O4AHꢃ ꢃ ꢃO2
O8AHꢃ ꢃ ꢃO1
N1AHꢃ ꢃ ꢃO2
N1AHꢃ ꢃ ꢃO8
N1AHꢃ ꢃ ꢃO7
N1AHꢃ ꢃ ꢃO6
N1AHꢃ ꢃ ꢃO5
(b) LASðꢁÞ ꢁ NHð4þÞ
O3AHꢃ ꢃ ꢃO1
O4AHꢃ ꢃ ꢃO2
O8AHꢃ ꢃ ꢃO1
N1AHꢃ ꢃ ꢃO3i
N1AHꢃ ꢃ ꢃO8
N1AHꢃ ꢃ ꢃO7
N1AHꢃ ꢃ ꢃO2
N1AHꢃ ꢃ ꢃO6
0.92(5)
0.98(3)
0.98(4)
0.95(3)
0.97(3)
0.97(3)
0.89(3)
0.89(3)
1.68(5)
1.92(4)
1.74(4)
1.98(3)
2.05(3)
2.21(3)
2.22(3)
2.23(3)
2.484(4)
2.762(4)
2.686(4)
2.888(4)
2.766(4)
3.081(4)
2.972(4)
2.904(4)
145(5)
142(3)
162(3)
160(3)
129(3)
149(3)
141(3)
132(3)
fragment of conjugated
p-electron system. This intramolecular
interaction makes the carboxylate group almost coplanar with
the aromatic ring. A similar cyclic conformation has been observed
in the crystal of non-dissociated lasalocid acid that exists in the
monomeric or dimeric forms [40–41]. The above mentioned fea-
ture of LAS(ꢁ) anion with such pseudo-cyclic conformation is the
central hole consisting of electronegative polarized oxygen atoms
that enclose the NHþ3 group of benzylammonium or NHþ4 cations
forming host–guest supramolecular complexes. Ionic and NAHꢃ ꢃ ꢃO
hydrogen bonding interactions between the oppositeþly charged
units of host LAS(ꢁ) and guest (benzylammonium or NH4 ) stabilize
the whole conformation of the host–guest supramolecular com-
plexes. The set of hydrogen bonds saturates all H donors in
LASðꢁÞ ꢁ BnNHð3þÞ, but leaves some H-acceptor sites unlinked. The
arrangement of LASðꢁÞ ꢁ BnNH3ðþÞ molecules in the crystal is mainly
determined by the van deer Waals and the crystal packing forces
(Fig. S1 Supplementary material) since no strong directional inter-
molecular hydrogen bonds have been observed. The arrangement
of LASðꢁÞ ꢁ NH4ðþÞ molecules (Fig. S2) as well as that of
LASðꢁÞ ꢁ BnNHð3þÞ molecules, is determined, besides the van der
1.01(5)
0.75(5)
0.86(4)
1.05(5)
0.81(4)
0.81(4)
0.95(6)
0.96(7)
1.50(5)
1.94(5)
1.96(4)
1.89(5)
2.02(4)
2.61(4)
2.13(6)
1.96(8)
2.421(4)
2.682(4)
2.812(4)
2.916(5)
2.795(5)
3.085(5)
2.979(5)
2.908(5)
149(4)
170(4)
167(4)
166(4)
162(3)
119(3)
148(4)
171(6)
Symmetry code: (i) ꢁ x + 2, y + 1/2, ꢁz + 1/2.
anion together with the attractive interactions between the O8AH
hydroxyl group as a donor and the O1 oxygen atom of carboxylate
as an acceptor as well as between the O4AH hydroxyl group as a
donor and the other O2 oxygen atom of carboxylate group as an
acceptor, lead to formation of intramolecular OAHꢃ ꢃ ꢃO hydrogen
Fig. 2. View of the gas-phase conformation of LASH (a) and it deprotonated LAS(ꢁ) anion (b) and their molecular electrostatic potential (ꢁ0.05 eÅꢁ1, red and +0.05 eÅꢁ1, blue)
mapped on the surface of total electron density (0.008 eÅꢁ3) (c) and (d), respectively. (For interpretation of the references to colour in this figure legend, the reader is referred
to the web version of this article.)

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LASðꢁÞ ꢁ NHð4þÞ supramolecular complexes, the theoretical calcula-
tions for these complexes as well as for the neutral molecule of
LASH and its dissociated LAS(ꢁ) anion were performed. The opti-
mised gas-phase geometries of neutral LASH acid molecule and
its LAS(ꢁ) anion are illustrated in Fig. 2a and b, respectively. The
gas-phase conformations of the LASH molecule and its deproto-
nated LAS(ꢁ) anion are also pseudo-cyclic and their geometrical
parameters are comparable (Table S1, in Supplementary material).
The small differences in the geometrical parameters between the
LASH and LAS(ꢁ) result from deprotonation of the carboxylic group
of LASH. The great flexibility of the LASH and its LAS(ꢁ) anion to-
gether with the attractive interactions between the hydrogen
bonding sites are responsible for the folding of the LASH and LAS(ꢁ)
anion into pseudo-cyclic conformation. This conformation of LASH
and its LAS(ꢁ) anion in the gas-phase is stabilised by the intramo-
lecular OAHꢃ ꢃ ꢃO hydrogen bonds (Table 4). As can be seen from
Fig. 2a and b, deprotonation of the carboxylic group of LASH with
formation of LAS(ꢁ) anion does not change significantly the confor-
mation of the whole skeleton, since the proton of the carboxylic
group is not involved in the hydrogen bond. In addition, the geom-
etry of the hydrogen bonds does not change significantly and the
pseudo-cyclic conformation is preserved after dissociation of the
LASH acid. Thus, the conformation of LASH and LAS(ꢁ) results from
intramolecular interactions between the oppositely polarised sites
within the skeletons of LASH or LAS(ꢁ) and therefore the molecular
electrostatic potential of LASH and LAS(ꢁ) was calculated (see the
Table 4
Geometry of the intramolecular hydrogen-bonds (Å, °) in the gas-phase of non-
dissociated LASH and its LAS(ꢁ) anion obtained by DFT calculations.
DAHꢃ ꢃ ꢃA
(a) LASH
DAH
Hꢃ ꢃ ꢃA
Dꢃ ꢃ ꢃA
DAHꢃ ꢃ ꢃA
O3AHꢃ ꢃ ꢃO1
O4AHꢃ ꢃ ꢃO2
O8AHꢃ ꢃ ꢃO1
1.014
0.996
1.001
1.673
2.081
1.897
2.555
2.913
2.894
142.7
139.8
174.9
(b) LAS(ꢁ)
O3AHꢃ ꢃ ꢃO1
O4AHꢃ ꢃ ꢃO2
O8AHꢃ ꢃ ꢃO1
1.070
1.014
1.018
1.447
1.625
1.736
2.445
2.616
2.749
152.3
164.4
172.4
Waals and the crystal packing forces, also by the intermolecular
N1AH1ꢃ ꢃ ꢃO3i (symmetry code as in Table 3) hydrogen bonds.
Therefore, the molecular conformation of LASðꢁÞ ꢁ BnNH3ðþÞ and
LASðꢁÞ ꢁ NHð4þÞ host–guest complexes is plausibly determined by
the intramolecular hydrogen bonding interactions inside the LAS(ꢁ)
anion and the hydrogen bonds between the oppositely charged
units of host–guest complexes.
Gas-phase structure
For better understanding of the host–guest interactions be-
tween the units that form the studied here LASðꢁÞ ꢁ BnNH3ðþÞ and
Fig. 3. View of the gas-phase conformation of host–guest complexes: LASðꢁÞ ꢁ BnNHð3þÞ (a) and LASðꢁÞ ꢁ NH4ðþÞ (b) and their molecular electrostatic potential (ꢁ0.05 eÅꢁ1, red
and +0.05 eÅꢁ1, blue) mapped on the surface of total electron density (0.008 eÅꢁ3) (c) and (d), respectively. (For interpretation of the references to colour in this figure legend,
the reader is referred to the web version of this article.)

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A. Huczynski et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 297–307
302
for the coplanar orientation of the COOH and COOꢁ groups with
the aromatic ring. The torsion angle O1AC1AC2AC3 describing
the orientation of COOH in LASH and COO– in LAS(ꢁ) anion is
ꢁ20.0o and 7.7o, respectively. This effect contributes to stabiliza-
tion of the whole molecule due to partial delocalisation of the
Table 5
Geometry of the intramolecular hydrogen-bonds (Å, °) in the gas-phase obtained by
DFT calculations.
DAHꢃ ꢃ ꢃA
DAH
Hꢃ ꢃ ꢃA
Dꢃ ꢃ ꢃA
DAHꢃ ꢃ ꢃA
(a) LASðꢁÞ ꢁ BnNHð3þÞ
O3AHꢃ ꢃ ꢃO1
O4AHꢃ ꢃ ꢃO2
O8AHꢃ ꢃ ꢃO1
N1AHꢃ ꢃ ꢃO2
N1AHꢃ ꢃ ꢃO8
N1AHꢃ ꢃ ꢃO7
N1AHꢃ ꢃ ꢃO6
N1AHꢃ ꢃ ꢃO5a
(b) LASðꢁÞ ꢁ NHð4þÞ
O3AHꢃ ꢃ ꢃO1
O8AHꢃ ꢃ ꢃO1
O4AHꢃ ꢃ ꢃO2
N1AHꢃ ꢃ ꢃO8
N1AHꢃ ꢃ ꢃO7
N1AHꢃ ꢃ ꢃO2
N1AHꢃ ꢃ ꢃO6
p-bond of the C1@O double bond within the ring formed by the
1.043
1.014
1.038
1.059
1.070
1.070
1.051
1.051
1.495
1.613
1.574
1.672
1.627
2.479
1.750
2.881
2.455
2.593
2.610
2.723
2.637
3.100
2.779
3.243
150.1
161.1
176.3
170.9
155.3
115.9
165.3
100.5
O3AHꢃ ꢃ ꢃO1 hydrogen bond.
The pseudo-cyclic skeleton of LAS(ꢁ) is preserved in the gas-
phase conformation of the host–guest LASðꢁÞ ꢁ BnNH3ðþÞ and
LASðꢁÞ ꢁ NHð4þÞ supramolecular complexes (Fig. 3a and b). The
gas-phase conformation of LASðꢁÞ ꢁ BnNHð3þÞ and LASðꢁÞ ꢁ NHð4þÞ is,
in general, similar to that found in the crystal (Table 2 and
Table S2). The hydrogen bonding system within the lasalocid
skeleton is responsible for preservation of its pseudo-cyclic confor-
mation upon formation of the host–guest LASðꢁÞ ꢁ BnNH3ðþÞ and
LASðꢁÞ ꢁ NHð4þÞ complexes (Table 5). Since the LAS(ꢁ) anion as a host
contains several unsaturated hydrogen bonding sites, therefore its
easily interacts with the benzylammonium or NHþ4 as a guest unit,
forming hydrogen bonded LASðꢁÞ ꢁ BnNHð3þÞ and LASðꢁÞ ꢁ NHð4þÞ
supramolecular complexes.
1.044
1.044
1.014
1.079
1.079
1.055
1.057
1.488
1.534
1.622
1.597
2.584
1.740
1.680
2.449
2.575
2.595
2.613
3.154
2.777
2.735
150.1
175.1
159.3
154.5
112.2
166.3
176.1
a
The Hꢃ ꢃ ꢃA distance is too long (2.881 Å) comparing to that in the crystal.
Molecular electrostatic potential
next section). The overcrowding effect of the adjacent substituents
in the rigid aromatic conjugated -electron ring leads to formation
of relatively short O3AHꢃ ꢃ ꢃO1 hydrogen bond and is responsible
p
The electrostatic potential V(r) that the electrons or nuclei of a
molecule generate at each point r in the surrounding space can
Fig. 4. View of the gas-phase conformation benzylamine (a) and its benzylammonium cation (b) and theirs molecular electrostatic potential (ꢁ0.05 eÅꢁ1, red and +0.05 eÅꢁ1
,
blue) mapped on the surface of total electron density (0.008 eÅꢁ3) (c) and (d), respectively. Figure (e) and (f) display the 3D MESP for NH3 and NHþ4 , respectively. (For
interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

´
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R
P
be calculated from the equation V(r) =
(ZA/(RA ꢁ r)) –
(
q
(r0)/
charged units, i.e. LAS(ꢁ) anion and benzylammonium cation, lead
to formation of NAHꢃ ꢃ ꢃO hydrogen bonds between these units
and change the charge distribution into that of the formed host–
guest LASðꢁÞ ꢁ BnNHð3þÞ supramolecular complex (Fig. 3c).
A
|r0 ꢁ r|)dr, where ZA is the charge on nucleus A having a position
vector RA and the
q
(r0) is the electron density function of the mol-
ecule. The molecular electrostatic potential (MESP) carries a wealth
of quantitative and qualitative information and is widely used as a
reactivity map displaying the most probable regions of the mole-
cule for the electrophilic attack of reagents. The MESP is useful as
a powerful predictive and interpretative tool in several fields of or-
ganic and inorganic chemistry, biology and crystal engineering, for
example in the rational drug design, folding of supramolecules,
protein–ligand interactions, catalysis, nucleophilic reaction and
intermolecular interactions and organisation of molecules in solids
[42–46]. In these studies, colourful maps of MESP are used to ratio-
nalise chemical properties of the atoms in molecules, noncovalent
interactions and binding in host–guest complexes [46].
The three-dimensional MESP maps are obtained on the basis of
the DFT (B3LYP) optimized geometries of molecules. The calculated
3D MESP maps mapped onto the total electron density isosurface
(0.008 eÅꢁ3) for each molecule are shown in Figs. 2–4. The colour
code of MESP is in the range of ꢁ0.05 (red) to 0.05 eÅꢁ1 (blue). Re-
gions of negative MESP are usually associated with the lone pair of
electronegative atoms, whereas the regions of positive MESP are
associated with the electropositive atoms.
Interaction between the neutral LASH (Fig. 2a and c) and NH3
(Fig. 4e) molecules is very similar to that between LASH and ben-
zylamine, and leads to the proton transfer from COOH group of
LASH to the negatively polarised N atom of NH3 (Fig. 4c) with for-
mation of the oppositely charged units, i.e. LAS(ꢁ) anion and NH4þ
cation. From the sterþeochemical point of view, the interaction be-
tween LAS(ꢁ) and NH4 involves the negatively polarised central re-
gion of LAS (Fig. 2d) and the three hydrogen atoms of NHþ4 . As a
result, the three NAHꢃ ꢃ ꢃO hydrogen bonds between the oppositely
charged LAS(ꢁ) and NHþ4 units are formed to give the host–guest
LASðꢁÞ ꢁ NHð4þÞ supramolecular complex, in which, as illustrated
in Fig. 3d, a change in charge distribution relative to that of LAS(ꢁ)
and NHþ4 ions (Figs. 2d and 4f) is evidenced by the MESP. The
unsaturated hydrogen atom of ammonium group of the host–guest
LASðꢁÞ ꢁ NHð4þÞ supramolecular complex with positive value of
MESP (blue colour in Fig. 2d) can form intermolecular NAHꢃ ꢃ ꢃO
hydrogen bond as observed in the crystal.
Spectroscopic studies
For a neutral molecule of LASH, the calculated 3D MESP map
displays the nucleophilic regions (red colour) near each oxygen
atom of LASH and electrophilic regions (blue colour) near the
hydrogen atoms (Fig. 2c). However, as can be seen in Fig. 2a and
c, near the oxygen atom O1, which is involved into two hydrogen
bonds, the negative value of MESP is significantly lower than that
near the unsaturated oxygen atoms. In addition, less negative val-
ues of MESP than those near the oxygen atoms are observed across
A comparison of the FT-IR spectra of crystalline LASH (dashed
line) and its crystalline complexes LASðꢁÞ ꢁ BnNH3ðþÞ (dashed-
dotted line) and LASðꢁÞ ꢁ NH4ðþÞ (solid line) given in Fig. 5a–c, points
the
p-electron conjugation on both sides of the phenyl ring. The
100
(a)
calculated 3D MESP, upon deprotonation of LASH and formation
of LAS(ꢁ) anion, displays significantly greater region of negative va-
lue of MESP, especially in the central hole of the pseudo-cyclic form
of lasalocid due to its anionic character (Fig. 2d). Therefore, this
form of lasalocid anion can easily interact with small cations form-
ing host–guest supramolecular complexes. The calculated 3D MESP
map of LASH and LAS(ꢁ) are helpful for understanding the
interactions within LASðꢁÞ ꢁ BnNH3ðþÞ and LASðꢁÞ ꢁ NHð4þÞ host–guest
supramolecular complexes (Fig. 3). In addition, the calculated
three-dimensional MESP for benzylamine and NH3 (Fig. 4c and e)
as well as for their cationic form, i.e. benzylammonium and NH4þ
(Fig. 4d and f), are helpful for understanding the interactions be-
tween the neutral molecules and the proton transfer between
LASH acid and the respective base (benzylamine and NH3) leading
to formation of the LASðꢁÞ ꢁ BnNH3ðþÞ and LASðꢁÞ ꢁ NHð4þÞ host–guest
supramolecular complexes. The interaction between LASH (Fig. 2a
and c) and benzylamine (Fig. 4a and c) leads to the proton transfer
from COOH group of LASH to the negatively polarised N amine
atom of benzylamine (red colour in Fig. 4a). As a result of the pro-
ton transfer the oppositely charged units, i.e. LAS anion (Fig. 2b and
d) and benzylammonium cation (Fig. 4d), are formed. Protonation
of benzylamine and formation of benzylammonium cation leads to
a change in orientation of the ammonium group in relation to the
phenyl ring with respect to that of amine group in the neutral
benzylamine molecule. In the gas-phase the torsion angle
C37AC36AC35AN1 describing the orientation of the amine/
ammonium group in relation to the phenyl ring is 153.79o in the
neutral benzylamine molecule and 88.56o in the benzylammonium
cation (Table S3).
50
LAS(-)-NH4
(+)
LAS
LAS(-)-BnNH3
(+)
0
4000
3500
3000
2500
2000
1500
1000
500
100
(b)
50
0
3900
3600
3300
3000
2700
2400
2100
1800
(c) 100
1684
50
0
1401
1400
1652
1700
1600
1500
It is clearly evidenced by the MESP of LAS(ꢁ) anion (Fig. 2d) and
benzylammonium cation (Fig. 4d) that the interactions between
them involve the central region of LAS(ꢁ) with a negative value of
MESP and the NHþ3 group of benzylammonium cation with the po-
sitive value of MESP. The interactions between these oppositely
Wavenumber [cm-1]
Fig. 5. The FT-IR spectra of crystals of: (dashed) LASH, (solid) LASðꢁÞ ꢁ NH4ðþÞ
complex and (dashed-dotted) LASðꢁÞ ꢁ BnNHð3þÞ complex recorded in Nujol/fluorol-
ube mulls; (a) 4000–400 cmꢁ1; (b) 3700–2300 cmꢁ1; (c) 1800–1500 cmꢁ1
.

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A. Huczynski et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 297–307
304
to clear differences between these structures, especially regarding
the formation of hydrogen bonds. The most important information
provided by the FT-IR spectra, concerning the structures of
LASðꢁÞ ꢁ BnNH3ðþÞ and LASðꢁÞ ꢁ NHð4þÞ complexes, is included in the
region 1750–1500 cmꢁ1 (Fig. 5c). In the spectrum of LASH (dashed
tetrahedral geometry (Td) of this cation (Fig. 8) [47–48]. Extensive
studies of the FT-IR spectra of ammonium cation salts have been
discussed previously in literature and four normal modes of tetra-
hedral NHþ4 cation have been found (Fig. 8) [47–48]. Consequently,
the bands observed in the FT-IR spectrum of the crystalline
LASðꢁÞ ꢁ NH4ðþÞ complex at 1684 cmꢁ1 and 1401 cmꢁ1 are assigned
line) the band assigned to the m(C@O) vibrations of the carboxylic
group is observed at 1652 cmꢁ1. In the spectra of both complexes
this band is no longer observed and instead, a new complex band
arises in the region below 1600 cmꢁ1. This new complex band is
to the m2 and m4 modes of vibration of the tetrahedral NHþ cation,
4
respectively.
The band assigned to the m(C@O) vibrations of the ketone group
a superposition of the
whereby the presence of the band at about 1596 cmꢁ1assigned to
the
as(COOꢁ) vibrations indicates a proton transfer from the
m
as(COOꢁ),
m
(C@C) and d(N+AH) vibrations,
in the spectrum of LASH is observed at ca. 1712 cmꢁ1. In the spec-
tra of LASðꢁÞ ꢁ BnNHð3þÞ, the band assigned to
m(C@O) is observed at
m
very near position of ca. 1710 cmꢁ1, while in the spectrum of
LASðꢁÞ ꢁ NHð4þÞ this band is shifted to 1718 cmꢁ1 indicating that
ketone group is not involved in any hydrogen bond.
carboxylic group of LASH to the benzylamine and ammonium
molecules within the LASðꢁÞ ꢁ BnNHð3þÞ and LASðꢁÞ ꢁ NHð4þÞ
complexes, respectively.
According to the X-ray data, in the spectra of the
LASðꢁÞ ꢁ BnNHð3þÞ and LASðꢁÞ ꢁ NHð4þÞ complexes, the bands labelled
in Fig. 5b should be assigned to the inter- and intra-molecular
hydrogen bonds of different strength that exist within the struc-
tures of these complexes. The hydrogen bonds and their parame-
ters are given in Table 3. The strongest hydrogen bond observed
in both complexes is that formed between O(3)AH group and O1
atom of the carboxylic group. This intramolecular hydrogen bond
belongs to the quasi-aromatic hydrogen bonds [49] characterized
by a very low intensity of the band assigned to the stretching
protonicꢁ1vibrations occurring usually in the region ca. 2200–
Furthermore, in the FT-IR spectrum of LASðꢁÞ ꢁ NH4ðþÞ complex
in the solid state two additional bands at 1684 cmꢁ1 and
1401 cmꢁ1 are observed. The presence of these bands is strictly
connected with the formation of a hydrogen bond system and
the vibrational mode of NHþ4 cation within the structure of the
crystalline LASðꢁÞ ꢁ NH4ðþÞ complex. According to the crystallo-
graphic data (Table 3), the NHþ4 cation is coordinated by relatively
weak N–Hꢃ ꢃ ꢃO hydrogen bonds. Three hydrogen atoms of NHþ4 cat-
ion are engaged in formation of intermolecular hydrogen bonds
within the pseudo-cyclic structure of the LAS(ꢁ) molecule. The
fourth hydrogen atom of the NHþ4 cation is engaged in the forma-
tion of one intermolecular hydrogen bond with the oxygen atom
of the neighbouring lasalocid anion. This system of complexation
of the NHþ4 cation by two lasalocid anion molecules results in the
3000 cm
[50–51]. Thus, the broad band with a maximum at
2653 cmꢁ1 observed in the FT-IR spectra of LASðꢁÞ ꢁ BnNHð3þÞ
should be assigned to the
m
(NHþ3 ) vibrations of the protonated
and hydrogen bonded amine group.
100
(a)
(a) 100
50
50
LAS(-)-BnNH3 in KBr
(+)
(-)
(+)
in KBr
LAS(-)-BnNH3 in CHCl3
(+)
LAS -NH
4
0
(-)
LAS -NH
(+)
in CHCl
3
4
4000
3500
3000
2500
2000
1500
1000
500
0
4000
3500
3000
2500
2000
1500
1000
500
100
(b)
(c)
(b)100
3208
3376
3298
50
50
2653
3357
3600
3155
3216
3300
3178
3350
3300
0
0
3900
3600
3000
2700
2400
2100
1800
3900
3000
2700
2400
2100
1800
100
50
0
(c) 100
1585
1684
50
0
1708
1568
1708
1595
1573
1596
1573
1710
1700
1401
1400
1718
1700
1600
1500
1600
1500
1400
Wavenumber [cm-1]
Wavenumber [cm-1]
Fig. 6. The FT-IR spectra of: (solid) chloroform solution of LASðꢁÞ ꢁ BnNH3ðþÞ
complex and (dashed-dotted) crystals of LASðꢁÞ ꢁ BnNH3ðþÞ recorded in Nujol/
Fig. 7. The FT-IR spectra of: (dashed) chloroform solution of LASðꢁÞ ꢁ NH4ðþÞ complex
and (solid) crystals of LASðꢁÞ ꢁ NH4ðþÞ recorded in Nujol/fluorolube mulls: (a) 4000–
fluorolube mulls: (a) 4000–400 cmꢁ1; (b) 3800–3200 cmꢁ1; (c) 1800–1500 cmꢁ1
.
400 cmꢁ1; (b) 3800–3200 cmꢁ1; (c) 1800–1500 cmꢁ1
.

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A. Huczynski et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 297–307
of the possible structures of the LASðꢁÞ ꢁ NH4ðþÞ complex present
in the solution and gas phase were presented above. These results
also clearly demonstrate that in contrast to the solid phase, in the
solution the NHþ4 cation is coordinated only by one lasalocid anion
molecule and only three hydrogen atoms of NHþ4 cation are en-
gaged in the formation of intermolecular hydrogen bonds (Table 5).
The most important 1H and 13C NMR signals of LASH and its
LASðꢁÞ ꢁ BnNHð3þÞ and LASðꢁÞ ꢁ NHð4þÞ complexes are given in Table 6.
The most sensitive are the signals of the C(1) atom of the carbox-
ylic group and its C(2) neighbouring atom (Scheme 1). In the 13C
NMR spectrum of LASH, the chemical shifts of these carbon atoms
are found at 173.2 ppm and 111.0 ppm, respectively. In the spectra
of LASðꢁÞ ꢁ BnNH3ðþÞ and LASðꢁÞ ꢁ NHð4þÞ complexes, the signals of
these carbon atoms are shifted toward 175.5 (175.7) ppm and
115.6 (115.8) ppm, as a result of the proton transfer from the car-
boxylic group to the amine or ammonia, respectively.
H
H
H
H
N+
N+
N+
N+
H
H
H
H
H
H
H
H
H
H
H
H
ν1
3040 cm-1
ν2
ν3
ν4
1680 cm-1
3145 cm-1
1400 cm-1
Fig. 8. Arrows in the figure indicate the direction of motion but are not to scale with
the amplitude.
According to the crystal data (Table 3), in the spectrum of
LASðꢁÞ ꢁ BnNH3ðþÞ complex, the bands with maxima at 3350 cmꢁ1
and 3178 cmꢁ1 are assigned to O4AHꢃ ꢃ ꢃO2ꢁ and O8AHꢃ ꢃ ꢃO1ꢁ
intramolecular hydrogen bonds, respectively.
The shift of the 13C NMR signal of the carbon atom from the ke-
tone group in the spectra of LASðꢁÞ ꢁ NHð3þÞ and LASðꢁÞ ꢁ BnNHð3þÞ
complexes to 217.5 ppm and 218.2 ppm, respectively, in compari-
son with the signal in the spectrum of LASH arising at 214.4 ppm,
may suggest that the oxygen atom of ketone group interacts with
protonated amines by a weak hydrogen bond. However, the band
in the FT-IR spectra of both complexes, assigned to the C@O
stretching vibrations of the ketone group is very slightly shifted to-
ward lower or higher wavenumbers in comparison to the position
of this band in the FT-IR spectrum of LASH. The FT-IR observations
indicate that the ketone group is not engaged in the hydrogen bond
formation neither with NH3þ group nor NHþ4 cation and the shifts of
the carbonyl carbon atom signals in 13C NMR should be connected
with the conformational changes in the lasalocid molecule fol-
lowed by complexation of the respective amines. This conclusion
is also in agreement with the DFT calculations which show that
in the most energetically favourable structure, the oxygen atom
of the ketone group of the LAS(ꢁ) anion is not engaged in the hydro-
gen bond formation (Fig. 3, Table 5).
In the spectrum of LASðꢁÞ ꢁ NHð4þÞ complex, the bands with max-
ima at ca. 3350 cmꢁ1 and 3178 cmꢁ1 can be assigned to
O8AHꢃ ꢃ ꢃO1ꢁ and O4AHꢃ ꢃ ꢃO2– intramolecular hydrogen bonds on
the basis of the hydrogen bonds parameters collected in Table 3.
Comparison of the FT-IR spectra of LASðꢁÞ ꢁ BnNH3ðþÞ complex in
chloroform and in the solid state (Fig. 6) shows small changes asso-
ciated only with changes in the hydrogen bond strength. Also the
protonic vibrations within the O8AHꢃ ꢃ ꢃO1– and O4AHꢃ ꢃ ꢃO2–
hydrogen bonds are indicated by broad bands in the same region
in which the respective vibrations in the spectrum of the crystal-
line LASðꢁÞ ꢁ BnNHð3þÞ complex are found. This spectral feature indi-
cates that in the solution the crystal structure of this complex is
practically conserved.
The spectral features of the LASðꢁÞ ꢁ NH4ðþÞ complex in solution
compared with the respective spectrum in the solid indicate
clearly a dissociation of the dimeric form of the LASðꢁÞ ꢁ NH4ðþÞ
complex after dilution. This phenomenon is accompanied by a
change in the coordination geometry of NHþ4 cation. In the spec-
trum of LASðꢁÞ ꢁ NHð4þÞ complex in chloroform (Fig. 7, dashed line)
the bands assigned to the m2 and m4 modes of tetrahedral NHþ4 in
the solid are no longer observed. The respective DFT calculations
The proton transfer from the carboxylic group to the N atom of
amine or ammonia is also indicated in solution in the 1H NMR
spectra by the signals of NHþ3 and NH4þ protons at 7.80 ppm and
Table 6
The most important 1H and 13C NMR chemical shifts d (ppm) of LASðꢁÞ ꢁ BnNH3ðþÞ, and LASðꢁÞ ꢁ NH4ðþÞ complexes in CDCl3 and differences
D (ppm) between shifts and respective
chemical shifts for LASH in CDCl3.
LASðꢁÞ ꢁ BnNHð3þÞ
LASðꢁÞ ꢁ NHð4þÞ
No. atoms
LASH
d
1H
d
13C
d
1H
d
13C
d
1H
d
13C
D1 1H
D1 13C
D2 1H
D2 13C
1
2
3
4
5
6
7
11
12
13
14
15
18
19
22
23
–
–
–
–
7.17
6.63
–
4.08
2.84
–
2.62
3.88
–
3.50
–
3.93
–
6.14br
11.84
6.14br
6.14br
–
173.2
111.0
161.6
124.2
134.5
121.4
144.1
73.0
48.8
214.4
55.0
83.8
86.2
–
–
–
–
7.07
6.51
–
4.31
2.80
–
2.49
4.04
–
3.38
–
3.64
4.21
–
14.43vbr
4.04
4.93
7.80
175.5
115.6
161.7
123.6
133.6
120.2
144.2
71.2
48.9
218.2
56.0
83.1
87.3
70.1
70.6
76.1
43.4
–
–
–
–
–
6.99
6.46
–
4.31
2.74
–
2.45
3.97
–
175.7
115.8
161.5
123.1
131.9
123.1
144.0
71.4
49.0
217.5
55.9
82.7
87.3
69.8
71.4
76.3
–
–
–
–
–
2.3
4.6
0.1
ꢁ0.6
ꢁ0.9
ꢁ1.2
0.1
ꢁ1.8
0.1
3.8
1
ꢁ0.7
1.1
ꢁ0.6
ꢁ2.0
0.1
–
–
–
–
–
2.5
4.8
ꢁ0.1
ꢁ1.1
ꢁ2.6
1.7
ꢁ0.1
ꢁ1.6
0.2
3.1
0.9
ꢁ1.1
1.1
ꢁ0.9
ꢁ1.2
0.3
–
ꢁ0.1
ꢁ0.12
–
0.23
ꢁ0.04
–
ꢁ0.13
0.16
–
ꢁ0.12
ꢁ0.18
ꢁ0.17
–
0.23
ꢁ0.10
–
ꢁ0.17
0.09
–
ꢁ0.11
70.7
72.6
76.0
3.39
–
3.82
–
ꢁ0.29
–
–
2.59
ꢁ2.10
ꢁ1.21
–
ꢁ0.11
35
O(1)H
O(3)H
O(4)H
O(8)H
NHþ3
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
14.50vbr
4.03
4.80
6.94
2.66
ꢁ2.09
ꢁ1.34
–
–
–
–
D1 = d(LASðꢁÞ ꢁ BnNHð3þÞ) ꢁ dLASH; D2 = d(LASðꢁÞ ꢁ NHð4þÞ) – dLASH; br – broad signal; vbr – very broad signal.

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A. Huczynski et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 297–307
306
6.94 ppm. These chemical shifts show that these protonated spe-
cies are coordinated in the pseudo-cyclic structure of lasalocid an-
ion only by a weak hydrogen bond.
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Financial support from budget funds for science in years
2012-2013 – grant ’’Iuventus Plus’’ of the Polish Ministry of
Science and Higher Education–No. 0179/IP3/2011/71, is gratefully
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