32
V. Saheb et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 29–36
3.87–38.3 (m, 1H, ACH), 6.8 (d, J = 8.9, 1H, aromatic proton), 6.94
Table 3 (continued)
(dd, 1J = 8.9, 2J = 3.1, 1H, aromatic proton), 7.04 (d, J = 3.0, 1H, aro-
matic proton), 8.45 (s, 1H, C@N), 13.00 (s, 1H, AOH); 13C NMR
(400 MHz, d6-DMSO, 25 °C) dppm.; 22.22, 56.42, 66.56, 67.26,
115.75, 118.02, 119.34, 120.01, 152.31, 155.59, 167.06; Elem. Anal.
Calc: C, 63.16, H, 7.18, N, 6.70; C11H15NO3 (209).
Experiment
B3LYP/DGDZVP
Assignment
1453
1563
1596
1641
2835
2864
2958
3079
1509
1597
1656
1678
3024
3047
3107
3188
SC(HCH)
SC(HOH)
BS(C@C)
BS(C@N)
BS(CAH)
BS(CAH)
BS(CAH)
BS(CAH)
To 0.01 mol (2.09 g) of 5-methoxy-2-[(2-hydroxypropylimi-
no)methyl]phenol ligand (H2L), was added 0.01 mol (3.28 g) di-
oxo-molybdenum(VI) acetylacetonate in 10 mL methanol. The
reaction mixture was stirred under reflux condition for 1 h. After
washing with cold methanol, recrystallization from methanol and
drying in vacuum, the yellow crystals were secured in 78% yield
(2.62 g) and m.p. >250 °C, (Scheme 1).
BS: Bond stretching, SC: scissoring, R: rocking, W: wagging, T: twisting, IB: in-plane
bending, OB: out-of-plane bending.
IR (KBr) 1641 cmꢀ1
(m (mC@C), 910 and
C@N), 1596 cmꢀ1
3500
932 cmꢀ1 Mo@O); 1H NMR (400 MHz, d6-DMSO, 25 °C) dppm. 1.26
(m
(d, J = 6.0, 3H, ACH3), 3.59–3.52 (dd, 1H, ACH2), 4.15 (dd,
1J = 13.4, 2J = 3.7, 1H, ACH2), 3.74 (s, 3H, AOCH3), 4.45–4.41 (m,
1H, ACH), 6.82 (d, J = 8.9, 1H, aromatic proton), 7.13–7.08 (m,
2H, aromatic proton), 8.66 (s, 1H, C@N); 13C NMR (400 MHz, d6-
DMSO, 25 °C) dppm.; 20.30, 56.02, 67.05, 77.55, 116.40, 120.50,
121.01, 122.45, 152.27, 156.44, 162.79.
υexp = 0.95( 0.01) υcalcd + 3.8( 10.0)
3000
R = 1.000
2500
2000
1500
1000
500
0
X-ray diffraction data of the dioxo-molybdenum(VI) complex
Crystal data for the complex, along with other experimental de-
tails, are summarized in Table 1. Single-crystal data collection was
performed at 233 K on a Stoe Mark II-Image Plate Diffraction Sys-
tem [19] equipped with a two-circle goniometer and using graph-
ite-monochromatized MoK
radiation (k = 0.71073 Å). The
a
0
500
1000
1500
2000
2500
3000
3500
Theoretical vibrational frequecies (cm-1)
complex MoO2(L)(H2O) crystallizes in the Triclinic space group P-
1. The structure was solved by Direct methods using the program
SHELXS-97 [20]. The refinement and all further calculations were
carried out using SHELXL-97 [20]. The water H-atoms were located
in a difference electron density map and were refined with dis-
tance restraints: OAH = 0.84(2) Å and Uiso(H) = 1.5Ueq(O). The C-
bound H-atoms were included in calculated positions and treated
as riding atoms: CAH = 0.94, 0.97, 0.98 and 0.99 Å for H-aromatic,
CH3, CH2, and CH H-atoms, with Uiso(H) = k ꢁ Ueq(C), where k = 1.2
for H-aromatic and CH and CH2 H-atoms, and 1.5 for H-methyl. The
non-H atoms were refined anisotropically, using weighted full-ma-
trix least-squares on F2. The molecular structure and crystallo-
graphic numbering scheme are illustrated in the PLATON [21]
drawing, Fig. 1. Fig. 2 shows a view of the crystal packing illustrat-
ing the formation of the infinite one-dimensional hydrogen bonded
polymer.
Fig. 3. A plot of experimental versus theoretical vibrational frequencies at the
B3LYP/DGDZVP level.
Experimental section
Materials and measurements
All of the chemicals and reagents were purchased from Fluka
and Merck chemical companies and were used without further
purification. 1H NMR and 13C NMR spectra were recorded on a Bru-
ker DRX-400 MHz ultrashield spectrometer using d6-DMSO as sol-
vent. FT-IR (KBr pellet, 450–4400 cmꢀ1) spectrum was taken with
Perkin-Elmer Model RX-I FT-IR spectrometer. The electronic spec-
tra were recorded on a Beckman DU-7000 UV–Vis spectrophotom-
eter. Microanalyses (C, H, and N) of the ligand and complex were
carried out on a Heracuse CHN rapid analyzer. Melting points were
determined on a Gallenkamp melting point apparatus.
Theoretical section
The geometry of the complex was optimized at the B3LYP and
PW91PW91 levels of theory with the basis set of DGDZVP [22].
The harmonic vibrational frequencies and their relative intensities
were calculated by B3LYP/DGDZVP method and the results were
compared with experimental FTIR spectra. The GIAO (Gauge
Including Atomic Orbital) method [23,24] was employed to 1H
NMR and 13C NMR chemical shifts at the B3LYP and PW91PW91
levels. Two different basis sets were used: The standard DGDZVP
basis set and a combined basis set in which DGDZVP was employed
for Mo atom and 6 ꢀ 31 + G(2df,p) for other atom. The latter basis
set is called BS2 in the present study. Solvent (DMSO) was consid-
ered as a uniform dielectric constant 46.7 and Polarizable Contin-
uum Model (PCM) [25] was employed to calculate the NMR
chemical shifts. Time-dependent density functional theory (TD-
DFT) was used to compute excitation energies and oscillator
strengths for electronic transitions from ground to excited states
Synthesis
The asymmetric Schiff base 5-methoxy 2-[(2-hydroxypropyli-
mino)methyl]phenol (H2L) was obtained by addition of a solution
of 1-amino-2-propanol 0.01 mol (0.75 g) in 10 mL methanol to a
solution of 5-methoxy salicylaldehide 0.01 mol (1.52 g) in 10 mL
methanol and the reaction mixture heated for 1 h, giving a yellow
precipitate. The crude product was recrystallized from an CHCl3-
hexane (1/4 v/v). Yellow powder, Yield: 81% (1.69 g) and m.p.
58°C, (Scheme 1).
IR (KBr) 3193 cmꢀ1
(m (m (mC@C),
OH), 1645 cmꢀ1 C@N), 1521 cmꢀ1
1153 cmꢀ1 CO phenolic); 1H NMR (400 MHz, d6-DMSO, 25 °C) dppm.
(m
1.12 (d, J = 6.3, 3H, ACH3), 3.47 (dd, 1J = 11.8, 2J = 6.3, 1H, ACH2),
3.57 (dd, 1J = 11.85, 2J = 4.8, 1H, ACH2), 3.41 (s, 3H, AOCH3),