S. Ghosh, A. Ghosh / Inorganica Chimica Acta 442 (2016) 64–69
65
characterized by UV–Vis spectrophotometric titration of [NiL] with
the respective analyte metal ions. The single crystal X-ray crystal-
lographic analyses of the isolated solid reveal the formation of 2:1
and 1:1 adduct with CeIII(NO3)3 and UVIO2(NO3)2 respectively. It is
to be noted that complex 1 is the first trinuclear Ni2Ln complex
derived from salen type N2O2 Schiff base ligand. The formation of
such trinuclear complex with uranyl is also enlightened from spec-
trophotometric titration but the crystallographic evidence is
unknown till now.
IR (KBr):
m
(C@N) = 1598 cmꢁ1
,
m
(U@O) = 927 cmꢁ1
3).
,
m
(NOꢁ3 )
= 1482 cmꢁ1
(m
1), 1297 cmꢁ1 2), 1029 cmꢁ1
(m
(m
2.5. Physical measurements
Elemental analyses (C, H and N) were carried out using a Perkin-
Elmer 2400 series II CHN analyzer. IR spectra (4000–500 cmꢁ1
)
were recorded by a Perkin-Elmer RXI FT-IR spectrophotometer in
KBr pellets. Electronic spectra were collected from spectroscopic
grade acetonitrile solution of the complexes (500–200 nm) in a
1 cm optical glass cuvette with a Hitachi U-3501 spectrophotome-
ter. The spectrophotometric titration were performed in presence
of a large excess and fixed concentration of a supporting electrolyte
TBAP (100 mM) both in analyte and titrant to maintain the ionic
strength of the solution. The titrations were performed with
2 mL, 5 ꢂ 10ꢁ5 M [NiL] solution as analyte with corresponding
metal nitrates solution (1 mM) as titrant those were added up to
2. Experimental
2.1. Starting materials
2-Hydroxyacetophenone and 1,3-propanediamine were pur-
chased from Spectrochem, India and were of reagent grade. They
were used without further purification. Tetrabutyl ammonium per-
chlorate (TBAP), Ce(NO3)3ꢀ6H2O and UO2(NO3)2ꢀ6H2O was pur-
chased from Aldrich.
Caution! Perchlorate salts of metal complexes with organic
ligands are potentially explosive. Only a small amount of material
should be prepared, and it should be handled with care. All uranyl
compounds are toxic when ingested, and any contact with the skin
should also be avoided because of its mild radioactivity.
0.35 mL (metal concentration varied from 0 to 14.89 ꢂ 10ꢁ5
M
and the [NiL] concentration deviated due to volume correction
from 5 ꢂ 10ꢁ5 M to 4.25 ꢂ 10ꢁ5 (M).
2.6. Crystallographic data collection and refinement
Suitable single crystals of each of the two complexes were
mounted on a Bruker-AXS SMART APEX II diffractometer ready
with a graphite monochromator and Mo Ka (k = 0.71073 Å) radia-
2.2. Synthesis of the Schiff base ligand H2L and ligand complex [NiL]
tion. The crystals were placed at 60 mm from the CCD. 360 frames
were measured with a counting time of 5 s. The structures were
solved using Patterson method by using the SHELXS 97. Subsequent
difference Fourier synthesis and least-square refinement revealed
the positions of the remaining non-hydrogen atoms that were
refined with independent anisotropic displacement parameters.
Hydrogen atoms were placed in idealized positions and their dis-
placement parameters were fixed to be 1.2 times larger than those
of the attached non-hydrogen atom. Successful convergence was
indicated by the maximum shift/error of 0.001 for the last cycle
of the least squares refinement. Absorption corrections were car-
ried out using the SADABS program [10]. All calculations were carried
out using SHELXS 97 [11], SHELXL 97 [12], PLATON 99 [13], ORTEP-32 [14]
and WinGX system ver-1.64 [15]. Data collection with selected
structure refinement parameters and selected bond parameters
for both the complexes are given in Tables 1 and S1, of the support-
ing information respectively.
The Schiff-base ligand (H2L) and its subsequent Ni-derived
‘‘metalloligand” ([NiL]) were synthesized by reported methods
[9]. Briefly, 5 mmol of 1,3-propanediamine (0.42 mL) was mixed
with 10 mmol of 2-hydroxyacetophenone (1.20 mL) in 20 mL
methanol. The resulting solution was refluxed for ca. 2 h, and
allowed to cool. The yellow methanolic solution of H2L was used
for complex formation. A methanolic solution (20 mL) of Ni(ClO4)2-
ꢀ6H2O (1.825 g, 5 mmol) was added to a methanolic solution of H2L
(5 mmol, 10 mL) and triethyl amine (1.38 mL, 10 mmol) were
added to prepare the respective (NiL) crystalline ‘‘metalloligand”
[NiL].
2.3. Synthesis of complex [(NiL)2Ce(NO3)3] (1)
The ‘‘metalloligand” [NiL] (14.7 mg, 0.04 mmol) was dissolved
in acetonitrile (10 mL) and to it a solution of Ce(NO3)3ꢀ6H2O
(8.7 mg, 0.02 mmol in 5 mL of acetonitrile) was added, stirred to
mix and then allowed to stand overnight at room temperature
when reddish X-ray quality single crystals were deposited at the
bottom of the vessel.
3. Results and discussion
3.1. Syntheses and characterizations of the complexes 1 and 2
Yield 0.015 g, 71%, Anal. Calc. for C38H40N7O13Ni2Ce (1060.27):
C, 43.05; H, 3.80; N, 9.25. Found: C, 43.14; H, 3.71; N, 9.18. IR
Recently we successfully synthesized several [(ML)M0Xn] and
[(ML)2M0Xn] type complexes [where, M represent CuII and NiII
and M0 are different s-, p- and d-block elements] [16]. We also
reported such complexes where M = CuII and M0 = f-block metal
ions derived from the same ligand that forms 2:1 adduct with TbIII
and 1:1 adduct with UVIO22+ [6,7]. In the present endeavor we
extend our strategy where M is NiII. Expectedly, at room tempera-
ture (25–30 °C) under specified experimental conditions, we found
that [NiL] formed 2:1 adduct with Ce(NO3)3 and 1:1 adduct with
UO2(NO3)2 (Scheme 1). However it is worth to be mention that
even after changing the molar ratio of the reactants i.e., [NiL]:Ce
(NO3)3 = 1:1 and [NiL]:UO2(NO3)2 = 2:1 only complexes 1 and 2
respectively, were precipitate out from the reaction mixture.
Besides elemental analyses, both the complexes were primarily
characterized by IR spectra. The metalloligand [NiL] is neutral and
does not possess any counter anion (Fig. S1 of the supporting
information), whereas both the complexes contain nitrato
(KBr):
m
(C@N) = 1600 cmꢁ1
3).
, m (m
(NOꢁ3 ) = 1477 cmꢁ1 1), 1318 cmꢁ1
(m
2), 1023 cmꢁ1
(m
2.4. Synthesis of complex [(NiL)UO2(NO3)2] (2)
The ‘‘metalloligand” [NiL] (14.7 mg, 0.04 mmol) was dissolved
in acetonitrile (5 mL) and to it a solution of UO2(NO3)2ꢀ6H2O
(20.0 mg, 0.04 mmol in 5 mL of acetonitrile) was put in, swirled
to mix and then allowed to stand overnight at room temperature
when reddish microcrystalline compound deposited at the bottom
of the vessel. This compound was collected and redissolved in 5 mL
of acetonitrile by warming, and the solution was kept in a long
tube for slow evaporation. X-ray quality light orange single crystals
of complex 2 appeared after about 15 days.
Yield 0.020 g, 66%, Anal. Calc. for C19H20N4O10NiU (761.11): C,
29.98; H, 2.65; N, 7.36. Found: C, 29.90; H, 2.55; N, 7.27.