Ligational aspects of the hydrazide-based Schiff-base, N-(4″-pyridylcarboxamido)-4-(4′-hexyloxybenzoato)salicylaldimine towards some 3d metal ions and crystal structures of the Schiff-base and Zn(II) complex

Article abstract of DOI:10.1016/j.poly.2008.03.003

A novel hydrazide-based mesogenic (nematic) Schiff-base, N-(4″-pyridylcarboxamido)-4-(4′-hexyloxybenzoato)salicylaldimine, Hpychbsal (abbreviated as H₂L) was prepared and its structure studied by elemental analyses, mass, NMR and IR spectra and single crystal XRD (triclinic space group P over(1, ?) with Z = 4) techniques. The Schiff-base behaves as a uninegative bi/tridentate species in its non-mesogenic complexes of the general formula, [M(HL)₂] [M = Mn, Co, Ni, Cu and Zn] and as a dinegative tridentate species with Zn(II) in the distorted square-pyramidal complex, [ZnL · 2py], for which the crystal structure was solved (triclinic space group P over(1, ?) with Z = 2). The IR and NMR spectral data imply bonding of HL^- and L^2- species through phenolate oxygen and/or amidic oxygen and azomethine nitrogen atoms.

Full text of DOI:10.1016/j.poly.2008.03.003

Polyhedron 27 (2008) 1937–1941
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Ligational aspects of the hydrazide-based Schiff-base,
N-(400-pyridylcarboxamido)-4-(40-hexyloxybenzoato)salicylaldimine towards
some 3d metal ions and crystal structures of the Schiff-base and Zn(II) complex
Angad Kumar Singh a, Sanyucta Kumari a, K. Ravi Kumar b, B. Sridhar b, T.R. Rao a,
*
a Department of Chemistry, Banaras Hindu University, Varanasi 221 005, India
b Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500 007, India
a r t i c l e i n f o
a b s t r a c t
novel hydrazide-based mesogenic (nematic) Schiff-base, N-(400-pyridylcarboxamido)-4-(40-hex-
Article history:
A
Received 24 January 2008
Accepted 4 March 2008
Available online 23 April 2008
yloxybenzoato)salicylaldimine, Hpychbsal (abbreviated as H2L) was prepared and its structure studied
by elemental analyses, mass, NMR and IR spectra and single crystal XRD (triclinic space group P1 with
ꢀ
Z = 4) techniques. The Schiff-base behaves as a uninegative bi/tridentate species in its non-mesogenic
complexes of the general formula, [M(HL)2] [M = Mn, Co, Ni, Cu and Zn] and as a dinegative tridentate
species with Zn(II) in the distorted square-pyramidal complex, [ZnL ꢀ 2py], for which the crystal structure
Keywords:
Hydrazide-based Schiff-base
Square-pyramidal zinc(II) complex
Crystal structure
was solved (triclinic space group P1 with Z = 2). The IR and NMR spectral data imply bonding of HLꢁ and
ꢀ
L2ꢁ species through phenolate oxygen and/or amidic oxygen and azomethine nitrogen atoms.
Ó 2008 Elsevier Ltd. All rights reserved.
NMR spectra
1. Introduction
2.2. Synthesis
The chemistry of hydrazine derivatives has been investigated
intensively in the last decade owing to their coordinative [1–3]
and pharmacological activity [1–3] as well as their use in analytical
chemistry as metal-extracting agents [1–3]. As a part of our investi-
gation [4–6] on structural and spectroscopic studies of 3d metal
complexes of a series of mesogenic organic Schiff-bases, we report
here, the results of our investigations on the synthesis, spectroscopic
studies and crystal structure on the hydrazide-based mesogenic
Schiff-base, N-(400-pyridylcarboxamido)-4-(40-hexyloxybenzoato)-
salicylaldimine (H2L) and the corresponding 3d metal complexes.
The synthesis of N-(400-pyridylcarboxamido)-4-(40-hexyloxy-
benzoato)salicylaldimine, Hpychbsal (abbreviated as H2L) was
achieved by proceeding through three steps, viz., alkylation of 4-
hydroxy benzoic acid, followed by esterification and Schiff-base
formation.
4-Alkoxybenzoic acid and 4-alkoxy benzoate ester of 2,4-dihy-
droxybenzaldehyde (Precursor Chemicals) were prepared as re-
ported earlier [4] by proceeding through two major steps, viz.,
alkylation of 4-hydroxy benzoic acid, followed by esterification.
[M(HL)2] (M = Mn, Co, Ni, Cu and Zn) complexes were prepared
by refluxing together hot dry ethanolic solutions of the ligand, H2L
(0.92 g, 2.0 mmol in 30 mL) and the appropriate metal acetate
(1.0 mmol, in 20 mL) for ꢂ2 h at 70 °C. The reaction mixture was
left over night in the flask closed with guard tube. The solid com-
plex that separated out in each case was filtered under suction
and washed repeatedly with cold ethanol and dried over fused
CaCl2 in a desiccator.
2. Experimental
2.1. Materials
All reagents were purchased from commercial sources and used
as received: 4-hydroxy benzoic acid, 1-bromohexane, 2,4-dihy-
droxybenzaldehyde, N,N0-dicyclohexylcarbodiimide (DCC), N,N-
dimethylaminopyridine (DMAP) and isonicotinic acid hydrazide
are from Sigma–Aldrich, USA; all metal acetates and KOH are from
Merck. The solvents received were dried using standard methods
[7] when required.
2.2.1. Synthesis of N-(400-pyridylcarboxamido)-4-(40-hexyloxybenzo-
ato)salicylaldimine
It was prepared by refluxing absolute ethanolic solutions 4-alk-
oxy benzoate ester of 2,4-dihydroxybenzaldehyde (11.97 g,
35 mmol in 100 mL) and isonicotinic acid hydrazide (4.80 g,
35 mmol in 50 mL) for ꢂ1 h in presence of few drops of acetic acid
and leaving the solution over night. The micro-crystalline product
was filtered off by suction, thoroughly washed with cold ethanol,
* Corresponding author. Tel.: +91 542 2307326; fax: +91 542 2368127.
E-mail address: drtrrao@gmail.com (T.R. Rao).
0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2008.03.003

1938
A.K. Singh et al. / Polyhedron 27 (2008) 1937–1941
recrystallized from a solution of absolute ethanol/chloroform (v/v,
1/1) and dried at room temperature; yield: 12.11 g (75%) as a white
solid; m.p. 220 °C. 1H NMR (300 MHz; DMSO-d6; J (Hz), Me4Si at
C5D5N; Me4Si at 25 °C, ppm) d = 164.330 (–COO), 170.517 (–
0
NCH), 151.468 (–C4), 131.689 (–C6), 114.980 (—C3 ) and 108.218
(–C3), IR (KBr)/cmꢁ1
: 1725vs m(˜C@O), 1605s m(C@N), 1256s
3
25 °C, ppm) d = 0.887 (t, JH–H = 7.2, 3H, –CH3), 1.313–1.773 (m,
mas(C–O)esteric, 1140s m(C–O)phenol, 478s m(Zn–N), 455s m(Zn–O). Anal.
Calc. for C36H35N5O5Zn (683.08): C, 63.30; N, 10.25; N2H4, 4.68; Zn,
9.57. Found: C, 63.29; N 10.21; N2H4, 4.65; Zn, 9.55%.
3
3
8H, –CH2), 4.092 (t, JH–H = 6.6, 2H, –OCH2), 6.864 (1H, d, JH–
3
H = 6.9, –C5H), 6.874 (1H, s, –C3H), 7.117 (2H, d, JH–H = 9.0,
—C3 H), 7.710 (d, JH–H = 9.0, 1H, –C6H), 7.855 (d, JH–H = 5.4, 2H,
—C3 H), 8.064 (d, JH–H = 8.7, 2H, —C2 H), 8.704 (s, 1H, –NCH),
3
3
0
3
00
0
2.3. Physical measurements
3
00
8.800 (d, JH–H = 8.1, 2H, —C2 H), 11.400 (br s, 1H, –NH), and
12.311 (br s, 1H, Ph–OH); 13C{1H} NMR (75.45 MHz; DMSO-d6;
Me4Si at 25 °C, ppm) d = 163.841 (–COO), 163.306 (py-CO),
The 1H and 13C NMR spectra were recorded on a JEOL AL-
300 MHz FTNMR multinuclear spectrometer; C, H, and N contents
were micro analyzed on Elemental Vario EL III Carlo Erba 1108 ana-
lyzer. Infrared spectra were recorded on JASCO FT/IR (model-5300)
spectrophotometer in the 4000–400 cmꢁ1 region. The mass spectra
were recorded on JEOL SX-102 (EI/FAB) mass spectrometers. The
UV–Vis spectra were recorded on Shimadzu spectrophotome-
ter, model, Pharmaspec, UV 1700. Magnetic susceptibility mea-
surements were made at room temperature on a Cahn-Faraday
balance.
0
161.353 (—C4 ), 158.344 (–NCH), 153.136 (–C2), 150.399 (–C4),
00
00
0
148.001 (—C2 ), 139.990 (—C4 ), 132.095 (–C6), 129.812 (—C2 ),
00
0
121.512 (—C3 ), 120.556 (—C1 ), 116.798 (–C1), 114.713 (–C5),
+
0
113.436 (—C3 ) and 109.974 (–C3). m/z (EI): 121 (py-CONH , 100),
205 (C6H13-Ph-CO+, 88), IR (KBr)/cmꢁ1: 3435br m(O–H)phenol, 3279
ms(N–H)amide, 1726vs m(˜C@O), 1626w m(C@N), 1253s mas(C–O)esteric
,
1153s m(C–O)phenol. Anal. Calc. for C26H27N3O5 (461.51): C, 67.66; H,
5.90; N, 9.10. Found C, 67.58; H, 5.88; N, 9.07%.
2.2.2. Synthesis of [Ni(HL)2]
2.4. X-ray crystallographic data collection and refinement of the
structure
The micro-crystalline product was recrystallized from a solu-
tion of absolute ethanol/chloroform (v/v, 1/1) and dried at room
temperature; yield: 0.67 g (68%) as an orange coloured solid;
m.p. 310 °C (decompose). 1H NMR (300 MHz; CDCl3; J(Hz), Me4Si)
X-ray data for compounds H2L [ab83m] and [ZnL ꢀ 2py]
[ab64m] were collected at room temperature using a Bruker Smart
Apex CCD diffractometer with graphite monochromated Mo Ka
radiation (k = 0.71073 Å) with x-scan method. Preliminary lattice
parameters and orientation matrices were obtained from four sets
of frames. Unit cell dimensions were determined from the setting
angles of 9745/8981 reflections in the range of 2.69° < h < 27.85°/
2.25° < h < 27.37°. Integration and scaling of intensity data was
accomplished using SAINT program [8]. The structure was solved
by direct methods using SHELXS97 [9] and refinement was carried
out by full-matrix least-squares technique using SHELXL97 [9].
Anisotropic displacement parameters were included for all non-
hydrogen atoms. In [ZnL ꢀ 2py], the atoms C22, C23 and C24 are
disordered over two positions and their site-occupation factors
were refined to 0.737(6) and 0.263(6). The distance of the disor-
dered side chain atoms were restraint with DFIX command. In
H2L, all N-bound H atoms, O-bound H atoms and H atoms of the
water molecules were located in a difference Fourier map and their
positions and isotropic parameters were refined. All other hydro-
gen atoms were positioned geometrically and treated as riding
atoms, with C–H distances in the range of 0.93–0.97 Å and with
Uiso(H) values of 1.5Ueq(C) for methyl hydrogen and 1.2Ueq(C) for
other hydrogen atoms.
3
d = 0.922 (t, JH–H = 6.0, 3H, –CH3), 1.255–1.852 (m, 8H, –CH2),
3
3
4.053 (t, JH–H = 6.6, 2H, –OCH2), 6.787 (d, JH–H = 6.9, 1H, –C5H),
3
0
6.850 (s, 1H, –C3H), 6.972 (d, JH–H = 8.4, 2H, —C3 H), 7.129 (d,
3
3
3
00
JH–H = 8.5, 1H, –C6H), 8.103 (d, JH–H = 7.8, 2H, —C3 H), 8.164 (d,
3
0
JH–H = 8.0, 2H, —C2 H), 8.770 (s, 1H, –NCH), 8.805 (d, JH–H = 7.9,
2H, —C2 H), 11.399 (br s, 1H, –NH), and (Ph–OH) absent; 13C{1H}
NMR (75.45 MHz; CDCl3; Me4Si at 25 °C, ppm) d = 163.933 (–
COO), 163.504 (py-CO), 164.132 (–NCH), 150.713 (–C4), 132.433
00
0
0
0
(–C6), 132.054 (—C2 ), 120.936 (—C1 ), 114.549 (—C3 ) and 110.791
(–C3). m/z (FAB): 121 (py-CONH+, 100), IR (KBr)/cmꢁ1: 3280br
ms(N–H)amide, 1722vs m(˜C@O), 1612w m(C@N), 1255s mas(C–O)esteric
1150s m(C–O)phenol, 485s m(Ni–N), 450s m(Ni–O). Anal. Calc. for
52H52N6O10Ni (979.70): C, 63.75; N, 8.58; N2H4, 6.53; Ni, 5.99.
,
C
Found: C, 63.72; N 8.51; N2H4, 6.50; Ni, 5.96%.
2.2.3. Synthesis of [Zn(HL)2]
Yield: 0.71 g (72%) as a yellow solid; m.p. 230 °C (decompose);
1H NMR (300 MHz; C5D5N; J (Hz), Me4Si) d = 0.847 (t, JH–H = 6.2,
3
3
3H, –CH3), 1.235–1.718 (m, 8H, –CH2), 3.981 (t, JH–H = 6.5, 2H,
3
–OCH2), 6.774 (d, JH–H = 6.0, 1H, –C5H), 6.850 (s, 1H, –C3H),
3
3
0
7.196 (d, JH–H = 8.0, 2H, —C3 H), 7.438 (d, JH–H = 8.1, 1H, –C6H),
3
7.387 (d, JHꢁH = 8.0, 2H, —C3 H), 7.583 (d, 3JH–H = 8.0, 2H,
00
3
0
00
—C2 H), 8.750 (s, 1H, –NCH), 8.791 (d, JH–H = 7.9, 2H, —C2 H),
11.394 (br s, 1H, –NH), and (Ph–OH) absent; 13C{1H} NMR
(75.45 MHz; C5D5N; Me4Si at 25 °C, ppm) d = 163.930 (–COO),
Table 1
Magnetic and electronic spectral dataa of complexes of H2L
172.415 (py-CO), 168.517 (–NCH), 150.369 (–C4), 132.624 (–C6),
+
0
114.979 (—C3 ) and 108.213 (–C3). m/z (FAB): 121 (py-CONH ,
Complex
Colour
leff
(BM)
d–d
Transition
Assignment
octahedral
100), IR (KBr)/cmꢁ1: 3280 ms(N–H)amide, 1724vs m(˜C@O), 1608w
m(C@N), 1253s mas(C–O)esteric, 1148s m(C–O)phenol, 482s m(Zn–N),
448s m(Zn–O); the IR data for [M(HL)2] (M = Mn, Co and Cu) are
similar. Anal. Calc. for C52H52N6O10Zn(984.30): C, 63.32; N, 8.52;
N2H4, 6.50; Zn, 6.63. Found: C, 63.29; N 8.50; N2H4, 6.47; Zn, 6.60%.
transitions
Ground Excited
state(s) state(s)
(cmꢁ1
)
[Mn(HL)2] yellow
5.14
30120,
24038
6A1g
4Eg(D);
4A1g
[Co(HL)2]
reddish
brown
diamag. 13333,
23310
2B2; 2E
2A1;
square
2A1
pyramidalb
(l.s.) (M–M
bonding)
square
2.2.4. Synthesis of [ZnL ꢀ 2py]
Light-yellow coloured crystalline solid; 1H NMR (300 MHz;
[Ni(HL)2]
[Cu(HL)2]
yellow
diamag. 23474,
25773
1A1g
1A2g
1B1g
;
3
C5D5N; J (Hz), Me4Si) d = 0.845 (t, JH–H = 6.1, 3H, –CH3), 1.230–
planar
octahedral
x2–y2
3
yellowish 3.67
green
15798
xy
1.711 (m, 8H, –CH2), 3.979 (t, JH–H = 6.3, 2H, –OCH2), 6.769 (d,
3JH–H = 6.1, 1H, –C5H), 6.852 (s, 1H, –C3H), 7.211 (d, JH–H = 8.3,
3
3
3
a
0
2H, —C3 H), 7.430 (d, JH–H = 8.0, 1H, –C6H), 7.390 (d, JH–H = 8.3,
Spectra recorded in solutions of DMSO/chloroform (1:1 v/v).
3
b
00
0
The ground state configuration with increasing energy: (xy, (b2)2); (xz, yz, (e))4;
2H, —C3 H), 7.580 (d, JH–H = 7.9, 2H, —C2 H), 8.755 (s, 1H, –NCH),
(z2, (a1)).
8.788 (d, JH–H = 8.2, 2H, —C2 H); 13C{1H} NMR (75.45 MHz;
3
00

A.K. Singh et al. / Polyhedron 27 (2008) 1937–1941
1939
Table 2
izing microscope while none of the corresponding metal com-
plexes were found to show any mesogenic behaviour. The
structures and purity of the parent ligand and of the complexes
were checked and confirmed by elemental analyses and IR, 1H
NMR and EI/FAB mass spectra.
Crystal data and structure refinement parameters of ligand H2L [ab83m] and
[ZnL ꢀ 2py] [ab64m]
Empirical formula
Formula weight
Cell axes (Å)
C26H29N3O6
479.52
C36H35N5O5Zn
683.06
The room temperature magnetic moments and electronic spec-
tral data of the present complexes are included in Table 1. The
overall geometry around the metal ion has been assigned (Table
1) not only on the basis of leff values and the nature of the elec-
tronic spectra, but also on the basis of denticity of the ligand (vide
IR and NMR) and the number of the ligands coordinated to the me-
tal ion (vide elemental analyses). The leff values imply anti-ferro-
magnetic/ferromagnetic type interactions in the Mn(II) and Cu(II)
complexes respectively. The MnII complex provides with extremely
weak bands in the electronic spectrum in an octahedral environ-
ment of the metal ion [10]. The diamagnetic reddish brown com-
plex, [Co(HL)2], may be understood to have a low-spin square-
pyramidal geometry with M–M bonding [11]. The yellow-coloured
complex, [Ni(HL)2], implies square-planar [12] type geometry; it is
a
b
c
11.1888(6)
13.1068(7)
18.2186(10)
10.2286(8)
11.6022(9)
17.0491(13)
Cell angles (°)
a
b
80.904(1)
74.771(1)
73.494(1)
2461.6(2)
triclinic
108.619(1)
90.103(1)
115.916(1)
1700.7(2)
triclinic
c
Cell volume V (Å)3
Crystal system
Crystal size (mm)
Temperature (K)
Wavelength (Å)
Space group
0.19 ꢃ 0.14 ꢃ 0.09
16 ꢃ 10 ꢃ 0.06
273(2)
293(2)
0.71073
0.71073
ꢀ
ꢀ
P1
P1
F(000)
1016
1.294
4
0.093
23929/8669 [0.0229]
712
1.334
2
0.771
16496/5968 [0.0204]
Density (Mg/m3)
No form. Unit Z
Absorption coefficient (mmꢁ1
Reflections collected/unique
[R(int)]
)
1
fairly common practice to assign the first band to the A2g 1A1g
transition and the second major band to the 1B1g 1A1g transition
assuming a square-planar geometry [13].
Completeness to h = 25.00 (%)
Absorption correction
Refinement method
99.7
none
99.7
none
In the IR spectrum of H2L the broad absorptions centered at
3435 and 3279 cmꢁ1 may be assigned to the m(O–H)phenol and
ms(N–H)amide vibration [14]; further, the strong bands occurring at
1726 and 1253 cmꢁ1 may be assigned [14] to m(˜C@O) and m(C–
O) modes of aromatic ester; the band occurring at 1626 cmꢁ1
may be assigned to m(C@N) absorption of the azomethine moiety;
these bands are shifted to lower frequencies in the complexes,
indicating that the nitrogen atom of the azomethine group is coor-
dinated to the metal ion [15]. Coordination through a nitrogen
atom of the ligand is also implied by the appearance of a new band
in the complexes in the region, 468–485 cmꢁ1, assignable to m(M–
N) [16,17]. Coordination through phenolate oxygen to the metal
ion is implied by the shifts of the m(C–O) band in the complexes
[18] and by the appearance of new bands, assignable to m(M–O),
in the 443–455 cmꢁ1 region in the spectra of the complexes.
A comparison of the 1H and 13C{1H} NMR spectral data of the li-
gand with those of the Ni(II) and Zn(II) complexes shows the ab-
sence of the phenolic-OH signal (12.311 ppm) and a significant
shift in the peak position of the –N@CH signal [from 8.704 ppm
of the ligand to 8.770, 8.750, and 8.755 ppm in [Ni(HL)2], [Zn(HL)2]
and [ZnL ꢀ 2py], respectively] and the absence of the –N–H signal at
11.400 ppm exclusively in [ZnL ꢀ 2py], a complex of the di-deproto-
nated ligand, imply bonding through the phenolate oxygen and
azomethine nitrogen atoms. Similar shifts observed in the
13C{1H} NMR spectra were of considerable magnitude in the case
of the carbon atoms directly attached to the bonding atoms and
full-matrix least-
squares on F2
8669/0/665
ꢁ13, 13
full-matrix least-
squares on F2
5968/79/452
ꢁ12, 12
Data/restraints/parameters
H min, max
K min, max
ꢁ15, 15
ꢁ13, 13
L min, max
ꢁ21, 21
ꢁ20, 20
h min, max
1.16, 25.0
1.029
2.02, 25.0
1.044
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R1 = 0.0403,
wR2 = 0.1020
R1 = 0.0502,
wR2 = 0.1107
0.202 and ꢁ0.195
R1 = 0.0353,
wR2 = 0.0948
R1 = 0.0387,
wR2 = 0.0975
0.289 and ꢁ0.194
R indices (all data)
Largest difference peak and
hole (e Åꢁ3
)
3. Results and discussion
3.1. Physical properties and spectral investigation
The white-coloured Schiff-base ligand (H2L) is soluble in hot
chloroform, DMSO, DMF and pyridine but insoluble in water,
methanol, ethanol, and acetonitrile; the orange-coloured Ni(II)
complex, [Ni(HL)2], is soluble in chloroform, and hot DMSO and
DMF; [Zn(HL)2]/[ZnL ꢀ 2py] is only soluble in hot/cold pyridine;
all other complexes are soluble in DMSO, DMF and pyridine. The
Schiff-base showed a nematic meso-phase at 168 °C under a polar-
Fig. 1. Molecular structure and atomic labeling scheme of the H2L [ab83m] of 30% ellipsoid probability.

1940
A.K. Singh et al. / Polyhedron 27 (2008) 1937–1941
Fig. 2. Packing of molecules in the unit cell of H2L [ab83m] showing intermolecular and intramolecular H-bonding.
Fig. 3. Molecular structure and atomic labeling scheme of [ZnL ꢀ 2py] [ab64m] of 30% ellipsoid probability.
[ab83m] and [ZnL ꢀ 2py] [ab64m] are given in Table 2. The asym-
metric unit of H2L contains two crystallographically independent
molecules and two water molecules, while [ZnL ꢀ 2py] comprises
one ligand molecule and two pyridine solvent molecules in the
asymmetric unit. The molecular structure and atomic labeling
scheme of the ligand and the Zn(II) complex are as shown in Figs.
1 and 3 and the packing diagrams of the ligand and the complex
are as shown in Figs. 2 and 4.
The bond distances and angles for the [ZnL ꢀ 2py] complex are
shown in Table 3. As per the crystal structure of the complex, the
ligand coordinates to the Zn(II) ion through phenolate oxygen
(O(2)), amidic oxygen (O(1))and azomethine nitrogens (N(1)); fur-
ther, two pyridine molecules act as solvent molecules, thus, ren-
dering the overall geometry around Zn(II) to distorted square
pyramid. The details of the hydrogen-bonded geometry of H2L
are tabulated in Table 4. The crystal structure of H2L is stabilized
by both intra- and intermolecular N–H. . .O, O–H. . .N and O–
H. . .O hydrogen bond interactions. The two water molecules bridge
Fig. 4. Packing diagram of molecules [ZnL ꢀ 2py] [ab64m] along a-axis in the unit
cell.
Table 3
Bond lengths (Å) and angles (°) involved in the square pyramidal unit of the complex
[ZnL ꢀ 2py] [ab64m]
amidic carbon. Thus, the NMR spectral data imply bi-dentate bond-
ing (˜C@N, and phenolate oxygen) of HLꢁ in [Ni(HL)2] and tri-den-
tate bonding (˜C@N, phenolate oxygen and amidic oxygen) of HLꢁ
and L2ꢁ, respectively in [Zn(HL)2] and [ZnL ꢀ 2py].
N(1)–
Zn(1)
N(4)–
Zn(1)
N(5)–
Zn(1)
O(1)–
Zn(1)
O(2)–
Zn(1)
2.0370(16) N(1)–Zn(1)–
115.83(6) O(1)–Zn(1)–
93.71(6)
88.80(6)
91.50(7)
98.83(7)
163.15(7)
N(5)
N(4)
140.04(7) O(2)–Zn(1)–
N(1)
103.60(7) O(2)–Zn(1)–
N(4)
76.96(6) O(2)–Zn(1)–
N(5)
95.51(6) O(2)–Zn(1)–
O(1)
2.0793(17) N(1)–Zn(1)–
N(4)
2.0737(17) N(5)–Zn(1)–
N(4)
2.0764(14) N(1)–Zn(1)–
O(1)
3.2. Crystal structure and molecular association
Both ligands [H2L] [ab83m] and [ZnL ꢀ 2py] [ab64m] are crystal-
1.9840(14) N(5)–Zn(1)–
O(1)
ꢀ
lized in triclinic space group, viz., P1 with Z = 4 and Z = 2,respec-
tively. The crystal data and structure refinement details for [H2L]

A.K. Singh et al. / Polyhedron 27 (2008) 1937–1941
1941
Table 4
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033, or e-mail:
deposit@ccdc.cam.ac.uk.
Hydrogen bonds geometry (Å,°) for the ligand H2L [ab83m]
D–H. . .A
d(D–
H)
d(H. . .A) d(D. . .A) d(D. . .A) Symmetry
N(2)–
0.92(2) 1.87(2)
0.90(2) 1.91(2)
2.793(2) 178(2)
2.804(2) 173(2)
x + 1, y, z
x + 1, y, z
Acknowledgements
H(2N). . .O(1W)#1
N(5)–
H(5N). . .O(2W)#1
We wish to acknowledge recording of FAB Mass spectra and
elemental analyses at the Central Drug Research Institute, Luc-
know. One of the authors, Prof. T.R. Rao, gratefully acknowledges
the financial grant received from the Council of Scientific and
Industrial Research, New Delhi [Vide Grant No. 01(1834)/03/
EMR-II], the University Grants Commission [Vide Grant No. F.12-
26/2003 (S.R.)] and the Department of Science and Technology,
New Delhi [Vide Grant No. SR/S1/IC-26/2004].
O(2)–H(2O). . .N(3)
O(7)–H(7O). . .N(6)
O(1W)–
H(1W). . .N(4)#2
O(1W)–
H(2W). . .O(6)#3
O(2W)–
H(3W). . .O(1)#4
O(2W)–
0.91(2) 1.80(2)
0.86(2) 1.82(2)
0.89(2) 1.94(2)
2.613(2) 146(2)
2.587(2) 148(2)
2.828(2) 174(2)
x, y, z
x, y, z
ꢁx + 2, ꢁy + 2,
ꢁz
0.86(2) 1.99(2)
0.82(2) 2.17(2)
0.88(2) 1.97(3)
2.846(2) 174(2)
2.986(2) 171(2)
2.846(2) 173(2)
x, y ꢁ 1, z
x ꢁ 1, y, z
ꢁx + 2, ꢁy + 2,
ꢁz
H(4W). . .N(1)#2
References
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bonds, thereby forming an infinite hydrogen bonded network
chain along the crystallographic a axes. Only the non-conventional
interactions, viz., C–H. . .O and C–H. . .N, are observed in the crystal
structure of the [ZnL ꢀ 2py] complex.
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5. Supplementary data
CCDC 672486 and 672487 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or