P. Młynarz et al. / Journal of Molecular Structure 875 (2008) 130–134
131
(m, OCH2CH2OCH3), 70.87 and 70.94 (m, OCH2CH2
OCH3), 127.68 (s, Ar), 128.70 (s, Ar), 128.91 (s, Ar), 129.45
(s, Ar), 134 (d, Ar, J = 8.3 Hz), 137.91 (d, Ar, J = 3.4 Hz).
N
N
O
O
O
PCl3
O
O
OH
+
P
CH3CN; 6h,reflux
H
2.2. ESI-MS studies
O
toluene;
The ESI (electrospray ionization) mass spectra were
recorded on a Waters/Micromass (Manchester, UK) ZQ
mass spectrometer equipped with a Harvard Apparatus
syringe pump. The measurements were performed for two
types of samples: acetonitrile solutions of receptor
(1–5 · 10À3 mol dmÀ1) with a mixture of Li+, Na+, K+,
Rb+ and Cs+ cations (5 · 10À3 mol dmÀ1) and the same
acetoniotrile solutions of the compound with Li+, Na+,
K+, Rb+ and Cs+ cations (5 · 10À3 mol dmÀ1) taken sepa-
rately. The samples were infused into the ESI source using
a Harvard pump at a rate 20 l dm3 minÀ1. The ESI source
potentials were: capillary 3 kV, lens 0.5 kV, extractor 4 kV,
and the cone voltage 30 V. The source temperature was
120 ꢁC and the desolvation temperature was 300 ꢁC. Nitro-
gen was used as a nebulizing and desolvation gas at a flow
rate of 100 and 300 dm3 hÀ1, respectively.
6h; reflux
O
O
H
N
O
O
P
O
O
receptor L
O
O
O
P
N
H
O
Scheme 1. Route of preparation of tetra-2-methoxyethyl phenylene-1,4-
di(benzyloamino-methanephosphonate).
was added. The solution was refluxed for 6 h. The volatile
components were evaporated under reduced pressure yield-
ing product of satisfactory purity. Yield: 85% (colorless
1
oil). 31P NMR: d (ppm): 9.17 (s); H NMR (CDCl3): d
2.3. NMR measurements
(ppm): 6.94 (d, 1H, JH–P = 717 Hz, P–H), 4.27 and 4.19
(m, 2H each, OCH2CH2OCH3), 3.61 (t, 4H, J = 4.5 Hz,
OCH2CH2OCH3), 3.40 (s, 6H, OCH2CH2OCH3); 13C
NMR: d (ppm): 71.46 (d, J = 5.5 Hz, OCH2CH2OCH3),
64.62 (d, J = 5.6 Hz, OCH2CH2OCH3), 58.95 (s,
OCH2CH2OCH3).
NMR spectra were recorded on Bruker Avance
DRX300 and Bruker AMX600 instruments in CDCl3,
MeOD and D2O using a variety of 1D and 2D (HMQC,
COSY, TOCSY, NOESY, ROESY, T1-pseudo 2D) corre-
lation spectra techniques. Chemical shifts are given in rela-
tion to TMS or TSP, 85% phosphoric acid (phosphorus
spectra).
2.1.2. Synthesis of tetra-2-methoxyethyl phenylene-1,4-
di(benzyloaminomethanephosphonate), receptor L
Schiff base was synthesized according to the literature
data [5]. The terephthalaldehyde was dissolved in methanol
and then two equivalents of benzylamine were added. The
mixture was stirred for 4 h at room temperature and the
precipitated compound of satisfactory purity was collected
by filtration. Obtained Schiff base (0.857 g, 0.0027 mol) was
dissolved in toluene and di-2-methoxymethyl phosphite
(1 g, 0.0055 mol) was added. The mixture was refluxed
for 8 h (Scheme 1). Then the volatile components of reac-
tion mixture were evaporated in vacuo and the crude prod-
uct was purified by column chromatography (silica gel, 70–
230 mesh) using hexane/AcOEt/methanol (ratio 4.5:3:1.5)
mixture as eluent.
2.4. Theoretical calculations
PM5 semiempirical calculations were performed using
the WinMopac 2002 program [6–8]. In all cases full geom-
etry optimalization was carried out without any symmetry
constrains.
3. Discussion and results
3.1. Receptor structure by means of theoretical calculations,
NMR and ESI-MS studies
The semiempirical PM5 calculations performed for sin-
gle molecule of receptor carried out in the gas phase show
the presence of free rotations of aminomethylphosphonate
residues, with the differences between each of the found
conformations not exceeding few kJ/mol. In contrary, to
the NMR results (vide supra), theoretical calculations did
not reveal the presence of any intermolecular hydrogen
bonds of the N–H–O type neither for R,R nor S,S
enantiomers.
1
Yield: 21%, oil (colorless). H NMR (D2O): d (ppm):
7.30 (s, 4H, Ar), 7.21–7.03 (m, 10H, Ar), 4.16 and 4,17
(d, 1H each, J = 19.7 Hz, a-CHP) 4.11–4.06 (m, 4H,
OCH2CH2OCH3) 4.05–3.98 and 3.91–3.84 (m, 2H each,
–OHCHCH2OCH3), 3.74 (d, 2H, J = 13.5, PhCH2,), 3.56
(t, 4H, J = 4.2, OCH2CH2OCH3), 3.502 and 3.498 (d, 1H
each, J = 13.5 Hz, PhCH), 3.50–3.44 and 3.44–3.37
(m, 2H each, OCH2HCHOCH3), 3.28 and 3.21 (s, 3H
each, OCH2CH2OCH3) 13C NMR (D2O): d (ppm): 50.34
and 50.23 (m, PhCH2), 57.54 (–a-CHP, J = 156 Hz),
58.06 and 50.03 (s, OCH2CH2OCH3), 65.94 and 66.11
1
The H NMR signals of the receptor are changing with
its concentration, temperature and polarity of the solvent.
This fact may be caused by existence of intra- or