Exploration of unconventional π-hole and C-H?H-C types of supramolecular interactions in a trinuclear Cd(ii) and a heteronuclear Cd(ii)-Ni(ii) complex and experimental evidence for preferential site selection of the ligand by 3d and 4d metal ions

Article abstract of DOI:10.1039/c6ra04428j

In this present work we report the synthesis and structural characterisation of a trinuclear cadmium(ii) (1) and a di(phenoxido)-bridged dinuclear cadmium(ii)-nickel(ii) (2) complex derived from a bicompartmental (N₂O₄) Schiff base l

Full text of DOI:10.1039/c6ra04428j

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Exploration of unconventional π–hole and C–H···H–C types of
supramolecular interactions in a trinuclear Cd(II) and a heteronuclear
Cd(II)ꢀNi(II) complex and experimental evidence for preferential site selection
of the ligand by 3d and 4d metal ions.
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a
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Saikat Banerjee, Antonio Bauzá, Antonio Frontera,* and Amrita Saha*
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Abstract
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In this present work we report synthesis and structural characterisations of a trinuclear
cadmium (II) (1) and a di(phenoxido)ꢀbridged dinuclear cadmium(II)–nickel(II) (2) complexes
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derived from a bicompartmental (N2O4) Schiff base ligand, H L. It has been observed that, in
2
bicompartmental ligands the relatively small inner core is suitable for 3d metal ions and outer
core can be occupied by different metal centers like 3d, 1s, 2s, 4d and 4f. We have
experimentally established the above fact. In homotrinuclear complex 1 both inner (N2O2) and
outer (O4) core has been occupied by cadmium (II) ions. Complex 1 upon reaction with
NiCl .6H O produces heterodinuclar complex 2. Structural studies reveal that, in complex 1
2
2
terminal Cd units acquire trigonal prismatic geometry whereas the central Cd unit is eight
coordinated. In case of complex 2 both nickel(II) and cadmium(II) ions are hexaꢀcoordinated in
a distorted octahedral environment. Both the complexes are studied using different spectroscopic
techniques. Complexes 1 and 2 exhibit important and relatively unexplored group of
supramolecular interactions like π–hole, C–H···π and C–H···H–C along with other hydrogen
bonding interactions. Theoretical DFT calculations are devoted to analyze these non covalent
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interactions. Several computational tools like MEP surface analysis and NCI analysis are utilized
to explain and illustrate such interactions.
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Introduction
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Schiffꢀbase complexes play an important role in the development of modern coordination
chemistry and have various applications in the field of magnetism, catalysis, medicinal
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ꢀ9
chemistry, gas storage, electron transport processes and sensing. Among the Schiff base
ligands acyclic compartmental ligands which contains two different sites are vastly used to
prepare homo and heteronuclear complexes. Such types of Schiff base ligands are achieved from
the condensation between diamines and salicylaldehyde with an appended alkoxy group at ortho
position to the phenoxido oxygen (salphen) (Scheme 1). The ligands have two different
tetradentate coordination core, inner core consists of two imineꢀN and two phenoxoꢀO atoms and
outer core involves two phenoxoꢀO and two alkoxyꢀO units. In case of homonuclear complexes
10ꢀ12
large number of di, tri, tetra and polynuclear complexes having 3d and 4d metals
are known
1
3ꢀ19
20ꢀ36
37ꢀ38
whereas heteronuclear complexes involves different 3dꢀ1s, 3dꢀ2s,
3dꢀ3d,
3dꢀ4d,
and
3
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3dꢀ4f metal centers.
It has been observed that during formation of homo or heteronuclear complexes
bicompartmental ligands first form an intermediate known as “metalloꢀligand reactant”. This
metalloꢀligand system further react with different metals ions with 1s, 2s, 3d, 4d and 4f
electronic configuations, ammonium ion, dicarboxylic acid and deprotonated diamine. The
mostly used transition metal centre among the divalent first row transition element to prepare
“metalloꢀligand reactant” is Cu(II). In this case the Cu(II) center is coordinated with two imineꢀN
2
2,26,32
24
39ꢀ42
and two phenoxoꢀO atoms. Ni(II),
Mn(II) and Zn(II)
are also used for the same
purpose. In this context Salphen complexes containing zinc(II) need special mention. They have
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been widely used in the field of supramolecular chemistry, catalysis and transmetalation.
Presence of available coordination site and presence of intermolecular Zn···O interactions
between the zinc(II) center of a salphen unit and phenolic oxygen of another are the two most
dominating facts to exhibit such types of behavior. It has been also observed that zinc salphen
moiety incorporated into a crown ether framework exhibit excellent binding affinity toward
5
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cationic guest species.
The structural diversity of such complexes are achieved by interesting non covalent
5
3
interactions like hydrogen bonding, cation–π, anion–π, CH–π and other less recognized forces,
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such as, σ/πꢀhole, and C–H···H–C interactions etc. It is now well established that
supramolecular interactions deal with weak and reversible non covalent interactions which are
the basis of highly specific recognition, transport, and regulation mechanisms. It is vastly used to
understand the progress in many biological functions and drug design. Amongst supramolecular
interactions σ/πꢀholes interactions are very important but comparatively unexplored. In 1973
Birgi and Dunitz in a series of work explain the pathway along which a nucleophile attacks the π
5
5
ꢀhole of a C=O group. It has been observed that in a given group of the periodic table, σ/πꢀhole
interactions become more positive on going from the lower atomic number to the higher atomic
number. A positive πꢀhole interaction is highly directional in nature and observed between a
region with positive electrostatic potential of unpopulated π* orbitals and electron dense region.
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Recently, π ꢀhole interactions has been observed in acyl carbons, SO and SO moieties,
2
3
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RNO molecules, XCN, XZO (X=halogen, Z = pnictogen), etc. It is important to mention
2
2
that the nitro group plays a crucial role to modify the electronic nature of aromatic rings or
aliphatic chains. Therefore, it will participate in πꢀhole interactions and thus plays an important
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role in crystal engineering. Halogen bonding also needs special mention as it is important in the
field of biological systems and in the design of new materials.
In this work bicompartmental ligand, H L(N,N’ꢀbis(3ꢀ methoxysalicylidene)propyleneꢀ
2
1,3ꢀdiamine)upon reaction with Cd(NO ) .4H O produced
a
trinuclear complex
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2
2
[Cd (L) (NO ) ](1). This trinuclear complex upon reaction with NiCl .6H O generate a
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2
3 2
2
2
II
heterodinuclar Ni(II)ꢀCd(II) complex i.e. [{Ni L(CH OH) }CdCl ].H O(2). In complex 1 Cd(II)
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2
2
ions occupy both the coordination positions of the ligand, in complex 2 the inner Cd(II) centreis
easily replaced by the Ni(II) ion. Different spectroscopic studies are used to characterize both the
complexes. In contrast to the propensity of Cu(II) complexes to react with a second metal salt,
1
1
only few products have been obtained from a mononuclear Ni(II) compounds.
Most interesting observation in the supramolecular assembly of complex 1 and 2 is the
existence of remarkable π–hole, C–H···π and C–H···H–C interactions along with other hydrogen
bonding interactions. In complex 1 πꢀhole interaction is established between the O atom of the
nitrato ligand and the C atom of the C=N bond. Molecular electrostatic potential (MEP) surface
analysis and the non covalent interaction (NCI) analysis of compounds 1 and 2 allow an
assessment of different nonbonding interactions and the extent to which these weak interactions
stabilize the complex. Briefly, the systems derived from the bi compartmental ligand, H L
2
exhibit in the solid state selfꢀassemblies that are governed by an intricate combination of weak
interaction. They are thus interesting in the frontier research area of crystal engineering and
supramolecular chemistry. Thus, we have been motivated to explore this area further.
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Experimental section
Materials and synthesis
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All reagent or analytical grade chemicals and solvents were purchased from commercial
sources and used without further purification.
Synthesis of Schiff base ligand (H L = N,N’ ꢀbis(3ꢀ methoxysalicylidene)propyleneꢀ1,3ꢀ
2
diamine)
60
The tetradentate Schiff base ligand (H L) was prepared by the standard method. Briefly, a
2
mixture of oꢀvaniline (8.0 mmol, 1.217 g) and 1,3ꢀdiaminopropane (4.0 mmol, 0.296 g) in 50 mL
methanol was heated to reflux for 2 h. The resulting light yellow colored Schiff base ligand
(H L) was used for further reaction.
2
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Preparation of [Cd (L) (NO ) ] (1)
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3 2
A 10 ml methanolic solution of cadmium nitrate (6.0 mmol, 1.848 g) was added to a
methanolic solution of H L (4.0 mmol) followed by addition of triethylamine (8.0 mmol, ~1.5
2
1
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1
1
00
01
02
03
mL) and the resultant reaction mixture was heated to reflux for 4 h. The solution was then cooled
and filtered. Deep yellow colored crystals resulted from the slow evaporation of methanolic
solution of the complex at room temperature. Yield: 0.1880 g (82%). Anal. Calc. for
ꢀ
C H Cd N O : C 36.87%; H 3.09%; N 7.82%. Found: C 36.35%; H 3.07%; N 7.29%. IR (cm
38
40
3
6
14
1
3
ꢀ1
ꢀ1
1
04
, KBr): υ(C=N) 1625 m; υ(CꢀN) 1225 s; ν(CꢀH) 730 s. UVꢀVis, λmax (nm), (ε (dm mol cm ))
1
1
1
1
1
1
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in DMFꢀCH CN (1:9, v/v): 268 (10420), 353 (4004).
3
1
H NMR (DMSOꢀd , 300 MHz) δ ppm: 1.81 (bs, 2H), 4.12 (bs, 4H), 6.27ꢀ6.9 (m, 4H), 8.17ꢀ
6
8.32 (m, 2H)
1
3
C NMR (DMSOꢀd , 75 MHz) δ ppm: 31.98 (ꢀCH ), 55.6 (ꢀOCH ), 63.9 (ꢀCH ), 113.44(ꢀCH),
6
2
3
2
118.67 (ꢀCH), 128.04 (ꢀCH), 149.73 (ꢀCH), 169.56 (ꢀCH=N).
II
Preparation of [{Ni L(CH OH) }CdCl ].H O (2)
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A 10 ml methanolic solution of nickel chloride (2.0 mmol, 0.4754 g) was added to a methanolic
suspension of complex 1 (1.0 mmol) and the reaction mixture was stirred for 3 h at room
temperature. Then the solution was filtered. Deep green colored crystals resulted from the slow
evaporation of methanolic solution of the complex at room temperature.
1
1
15
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Colour: Deep Green. Yield: 0.0996 g (75%). Anal. Calc. for C H CdCl N NiO7: C
2
1
30
2
2
ꢀ1
37.96%; H 4.55%; N 4.22%. Found: C 37.20%; H 4.15%; N 4.02%. IR (cm , KBr): υ(C=N)
3
ꢀ1
ꢀ1
1
17
1620 m; υ(CꢀN) 1217 s; ν(CꢀH) 737 s. UVꢀVis, λmax (nm), (
ε (dm mol cm )) in DMFꢀCH CN
3
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1
1
1
1
1
1
1
1
1
1
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(1:9, v/v): 287 (28878), 370 (2123), 580 (195).
Physical measurements
Elemental analysis for C, H and N was carried out using a Perkin–Elmer 240C elemental
–
1
analyzer. Infrared spectra (400–4000 cm ) were recorded from KBr pellets on a Nicolet Magna
IR 750 seriesꢀII FTIR spectrophotometer. Absorption spectra were measured using a UVꢀ2450
spectrophotometer (Shimadzu) with a 1ꢀcmꢀpathꢀlength quartz cell. Electron spray ionization
mass (ESIꢀMS positive) spectra were recorded on a MICROMASS QꢀTOF mass spectrometer.
1
Measurements of H NMR spectra were conducted using a Bruker 300 spectrometer in DMSOꢀ
d6. Emission was examined by LS 55 Perkin–Elmer spectrofluorimeter at room temperature (298
K) in DMSOꢀMethanol (1:9, v/v) solution under degassed condition.
1
29
Xꢀray crystallography
1
1
1
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31
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Single crystal Xꢀray data of complexes 1 and 2 were collected on a Bruker SMART APEXꢀ
II CCD diffractometer using graphite monochromated Mo Kα radiation (λ = 0.71073 Å) at room
temperature. Data processing, structure solution, and refinement were performed using Bruker
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ApexꢀII suite program. All available reflections in 2 max
θ
range were harvested and corrected for
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Lorentz and polarization factors with Bruker SAINT plus. Reflections were then corrected for
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absorption, interꢀframe scaling, and other systematic errors with SADABS. The structures were
solved by the direct methods and refined by means of full matrix leastꢀsquare technique based on
2
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F with SHELXꢀ97 software package. All the non hydrogen atoms were refined with
anisotropic thermal parameters. CꢀH hydrogen atoms were inserted at geometrical positions with
U = 1/2U to those they are attached. Crystal data and details of data collection and refinement
iso
eq
for 1 and 2 are summarized in Table 1.
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Theoretical methods
The calculations of the non covalent interactions were carried out using the TURBOMOLE
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1
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1
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version 7.0 using the BP86ꢀD3/def2ꢀTZVP level of theory. To evaluate the interactions in the
solid state, we have used the crystallographic coordinates. This procedure and level of theory
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5
have been successfully used to evaluate similar interactions. The interaction energies were
computed by calculating the difference between the energies of isolated monomers and their
assembly. The interaction energies were corrected for the Basis Set Superposition Error (BSSE)
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using the counterpoise method.
1
1
1
1
1
1
1
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The NCI plot is a visualization index based on the electron density and its derivatives, and
enables identification and visualization of non covalent interactions efficiently. The isosurfaces
correspond to both favorable and unfavorable interactions, as differentiated by the sign of the
second density Hessian eigenvalue and defined by the isosurface color. NCI analysis allows an
assessment of hostꢀguest complementarity and the extent to which weak interactions stabilize a
complex. The information provided by NCI plots is essentially qualitative, i.e. which molecular
+
regions interact. The color scheme is a redꢀyellowꢀgreenꢀblue scale with red for ρ cut (repulsive)
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and blue for ρ (attractive). Yellow and green surfaces correspond to weak repulsive and weak
cut
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attractive interactions, respectively.
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Hirshfeld Surface analysis
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Hirshfeld surface analysis have been done using Crystal Explorer version 3.1. The normalized
vdW
contact distance (dnorm) based on d and d has been determined by the given equation where r
i
e
is the van der Waals (vdW) radius of the appropriate atom internal or external to the surface.
(
ꢀꢁꢂꢃ ꢁꢄ ꢅꢆ)
ꢃ ꢁꢄ ꢅꢆ
(ꢀ ꢂꢃ ꢇꢄ ꢅꢆ)
ꢇ
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dnorm=
+
ꢄꢅꢆ
ꢃ
ꢇ
1
1
1
1
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dnorm becomes negative for shorter contacts than vdW separations and becomes positive for
contacts greater than vdW separations, and is displayed using a red–white–blue color scheme,
where red highlights shorter contacts, white is used for contacts around the vdW separation, and
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9
blue is for longer contacts.
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1
1
1
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Results and Discussion
Syntheses, IR, UV/Vis spectra, photoluminescence properties of the Complexes
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The Schiff base used in this work is a well known symmetrical tetradentate ligand (H L). One
2
of the important aspects of this type of ligand (salphen) is that upon metalation the phenol
oxygen atoms of the ligand become negatively charged phenoxo groups, which have higher
coordination ability to another metal ion. Complex 1 was prepared by the reaction of
Cd(NO ) .4H O with H L in 3:2 molar ratio in methanol in presence of few drops of trimethyl
3
2
2
2
amine. Complex 2 was prepared by mixing complex 1 with NiCl ·4H O in methanol in a 1:1
2
2
molar ratio as shown in Scheme 1. Besides elemental analysis, all of the complexes were initially
–
1
characterized by IR spectroscopy. A strong and sharp band appeared at 1634 and 1619 cm ,
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respectively for complex 1 and 2, due to azomethine υ(C=N). In complex 1, stretching
–1
¯
frequencies at 1385 and 1290 cm were tentatively assigned to ν(NO ). In complex 2, a broad
3
–1
band appeared at 3443 cm , which may be assigned to the O–H stretching of the MeOH or of
the crystallized water molecule. The electronic spectra of complexes 1 and 2 are recorded in
DMFꢀCH CN (1:9 v/v) mixture of solvent. Both the complexes exhibit two sharp absorption
3
bands around 270 nm and 350 nm. These absorption bands can be assigned to n → π* or π → π*
transitions of the Schiffꢀbase ligands. Besides these bands, a broad absorption band is observed
in the visible region for complex 2 at 580 nm which can be assigned to the spinꢀallowed dꢀd
3
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70 1
transition T (F)← A . H NMR spectrum of complex 1 was performed using d ꢀDMSO as
1
g
2g
6
solvent. For complex 1 aromatic protons appeared within 6.27ꢀ6.90 ppm, where as aliphatic
protons appeared around 4.32 ppm and 1.80 ppm respectively. Azomethine CH=N proton
1
3
appeared at 8.3 ppm. In C NMR spectrum of complex 1, the aromatic carbon atoms appeared
within 113ꢀ118 ppm. Whereas, the imine carbon atom (ꢀCH=N) appeared at 169.53 ppm.
Aliphatic carbon atoms and carbon atom of the methoxy group appeared around 31, 63 and 55
ppm respectively. (Figure S3ꢀS6) Fluoresence spectrum of the free ligand complex 1 and 2 were
performed in DMFꢀCH CN (1:9 v/v) mixture of solvent. Free ligand H L upon excitation gives a
3
2
broad fluorescent emission band at 458 nm. Complex 1 upon excitation at 353 nm gives an
intense emission peak was observed at 492 nm.(Figure 3) This type of luminescence may be
attributed to the intraligand (π → π*) transition and the red shift in complex 1 may presumably
71ꢀ76
be due to the metal coordination.
For complex 2, upon excitation at 287 nm and 370 nm
respectively, no significant fluorescent emission band was observed mainly due to presence of
Ni(II) ion in the moiety.
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Description of the crystal structures of [Cd (L) (NO ) ] (1)
3
2
3 2
Compound 1 crystallized from slow diffusion of methanol solvent and it has monoclinic
space group P21/c. The crystal structure of [Cd (L) (NO ) ] (1) is presented in Figure 1. Selected
3
2
3 2
bond lengths and angles for complex 1 are given in table 2. The core structure of 1 contains a
Cd3 unit. The two terminal Cd atoms Cd1 and Cd2 are located in the inner N2O2 cavities of the
two Schiff base ligands and are each bonded to a bidentate nitrate anion, resulting in a trigonal
prismatic geometry. Both Cd1 and Cd2 atoms lie slightly above the N2O2 plane by 0.792 A°.
The central metal atom Cd3 is eight coordinated and is encapsulated in the O8 cavity formed by
four phenolic oxygen atoms (O,O) and four methoxy oxygen atoms (O,O). Thus the bridging
2
ꢀ
phenoxo oxygen atoms of the deprotonated Schiff base ligand L connect each terminal Cd atom
to the central Cd atom forming bis(µꢀphenoxo) bridged Cd(II) ꢀ Cd(II) motifs. The three Cd(II)
ions are nearly linear with a Cd(1)ꢀCd(3)ꢀCd(2) angle of 172.34° and CdꢀCd distances are similar
3.556Å and 3.546 Å for Cd1ꢀCd3 and Cd3ꢀCd2 respectively. The CdꢀN, CdꢀO (phonolic), CdꢀO
(methoxy) bond distances are 2.249 Å, 2.242 Å and 2.63 Å respectively and these values are
1
1
comparable with those found in other Schiff base complexes of Cd. The CdꢀO bond distances
varies in the extensive range which indicate different types of interaction between the Cd(II) ion
and the O atoms within the molecule. Presence of three carbon backbone makes the ligand
flexible and the two N2O2 planes of the Schiff base are crossed with dihedral angles of 66.77°
respectively.
In complex 1 self assembly by week πꢀhole interactions is observed. Cadmium
coordinated nitrate ions interact with imine CꢀH moieties through delocalized πꢀ electron cloud.
As a result one trinuclear unit is interlinked with two neighboring trinuclear units to generate a
two dimensional sheet. Presence of π…π interactions between phenyl rings of same molecule
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(intramolecular) and two adjacent molecules (intermolecular) further stabilizes the structure. The
distance between the centers of two rings is 3.952 Å.
II
Description of the crystal structures of [{Ni L(CH OH) }CdCl ].H O (2)
3
2
2
2
Compound 2 crystallized from slow diffusion of methanol solvent and it has
monoclinic space group P2 /n. A perceptive view and atom numbering scheme of the
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asymmetric unit of [{Ni L(CH OH) }CdCl ].H O (2) is presented in figure 2. Selected bond
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lengths and angles of complex 2 are given in table 3. One molecule of complex 1 upon reaction
with NiCl .6H O generates complex 2. Monomeric unit of Complex 2 consists of one [NiL] unit,
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one cadmium ion, two chloride anions and two methanol molecule. In the structure a
crystallographic two fold axis passes through the cadmium atom. Crystal structure clearly reveals
that the Ni(II) ion has replaced the Cd(II) from the inner core of the Schiff base ligand of
complex 1. Ni(II) ion is present in a hexa coordinated octahedral geometry where the basal
plane is formed by the two imine N atoms N(1) and N(2), and two phenoxido O atoms O(1) and
O(3), of the schiff base. Two methanol molecules coordinated axially to the metal centre (O5,
O6) through the oxygen center to complete the coordination. The Cd(II) molecule is present as a
terminal unit where it is coordinated with two phenolic oxygen atoms (O1,O3), two methoxy
oxygen atoms (O2,O4) of the Schiff base ligand and two chloride ions resulting a highly
distorted octahedral geometry. The bridging phenoxo oxygen atoms of the deprotonated Schiff
2
ꢀ
base ligand L connect terminal Cd atom to the Ni(II) atom forming bis(µꢀphenoxo) bridged
Cd(II) ꢀ Ni(II) motif with metal metal separation of 3.390Å. Terminal Cdꢀphenoxo bond
distances (2.2595Å) are significantly shorter than the Cdꢀmethoxy bond distances (2.5265Å).
Whereas CdꢀCl bond distances (2.4667Å) are shorter than the corresponding Cdꢀmethoxy bond
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distances but longer than the Cdꢀphenoxo bond distances. The small value of the average
deviation of the four oxygen atoms from the least square O4 plane clearly suggests that the four
oxygen atoms of Oꢀphenoxo and Oꢀmethoxy unit exists in almost planer form. The displacement
of Cd(1) from the least square O4 plane is 0.082 Å which suggests that the metal is perfectly
placed inside the O4 compartment. The range of bond angle around the Cd center are 65.39(8)–
159.99(8)°. The Niꢀimine (2.026(3) Å and 2.033(3) Å) and Niꢀphenoxo (2.003(2)Å and
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1.993(2)Å) bond distances which lie in the usual range are shorter than the NiꢀO (methanol)
bond distances (2.142(3)Å and 2.158(3)Å respectively). The small value of the average deviation
of the four oxygen atoms from the least square N2O2 plane clearly suggests that the four oxygen
atoms of Oꢀphenoxo and Oꢀmethoxy unit exists in almost planer form. The displacement of
Ni(1) from the least square N2O2 plane is 0.013 Å which suggests that the metal is perfectly
placed inside the N2O2 compartment. This result clearly suggests that small size of Ni(II) center
has more preference towards the inner core compared to the relatively large Cd(II) ion.
The orientation of ligands around the metal center is such that is no πꢀπ stacking
interaction is observed. But the molecule displays various interesting hydrogen bonding
interactions. The molecule contains water molecule as solvent of crystallization. It exhibits both
intramolecular and intermolecular hydrogen bonding with Niꢀcoordinated methanolic OꢀH and
Cdꢀcoordinated chlorine atoms and thus forming 2D sheet in bc plane.
Computational Study
The theoretical study is devoted to analyze the non covalent interactions that govern the crystal
packing of compounds 1 and 2 focusing our attention to the remarkable π–hole, C–H···π and C–
H···H–C interactions. In 1, the absence of good Hꢀbond donors facilitates the formation of a πꢀ
hole bonding interaction involving the C atom of the C=N bond and the nitrate. This type of
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bonding has attracted attention to the scientific community in the last years and has been
analyzed in the present study along with other interactions. In 2, the conventional Hꢀbonding
interactions are important due to the presence of the coordinated MeOH that is a very good Hꢀ
bond donor.
In Figure 4 we show the representation of an infinite chain found in the solid state of compound
1 where interesting and unconventional interactions are established. Apart from long range van
der Waals interactions between the organic ligands, two additional interactions are present. One
of both is a πꢀhole interaction between the O atom of the nitrato ligand and the C atom of the
C=N bond. The O···C distance is slightly shorter (3.20 Å) than the sum of van der Waals radii
(i.e., 3.22 Å). The importance of πꢀhole interactions in crystal engineering and other fields have
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been recently reviewed. We have computed the MEP surface of a theoretical model that
consists of the Schiffꢀbase ligand used in this work coordinated to a Cd(II) metal center. The
MEP surface of this simple model shows a positive electrostatic potential over the C atom of the
C=N bond, therefore it is well suited for interacting with electron rich molecules, thus explaining
the formation of the πꢀhole interaction in 1. The second interaction that we focus our attention is
established between two aromatic H atoms and the nitrato ligand (Figure 4A). This interaction
can be viewed as C–H···O hydrogen bonding interactions; however the directionality
(perpendicular approach) does not correspond to a hydrogen bond. Certainly, it resembles a Tꢀ
shape stacking interaction, where the πꢀsystem of the nitrate anion is involved. To evaluate the
unconventional interactions observed in 1, we have used two theoretical models that are shown
in Figure 4C, D. In the first theoretical model (Figure 4C), both πꢀhole and C–H···NO3
interactions are evaluated along with other long range van der Waals interactions. The computed
interaction energy is ꢁE = –27.7 kcal/mol confirming the importance of this intricate
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combination of interactions. In the second model the nitrato ligand has been substituted by nitrito
(see small arrow in Figure 4D) and, consequently, the π–hole interaction is not formed. The
interaction energy is reduced to ꢁE = –24.3 kcal/mol. The contribution the π–hole interaction
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can be evaluated by difference, which is ꢁE –ꢁE = –3.4 kcal/mol, confirming its importance in
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the crystal packing of compound 1. In order to characterize the interactions in 1, we have also
computed the NCI plot that is shown in Figure 4E. A small green isosurface can be observed
between one oxygen atom of the nitrito ligand and the C atom of the C=N bond, thus confirming
the existence of the πꢀhole interaction. More extended surfaces can be observed between the
aromatic rings and other aliphatic groups that characterize the long range van der Waals
interactions. Moreover, another isosurface is observed between the nitrato ligand and both C–H
aromatic groups (Figure 4E). This surface is extended all over the nitrato ligand instead of the
formation of two small isosurfaces between the H and O atoms. This indicates that the
interaction cannot be defined as Hꢀbonding and, instead, it is better described as a C–H···π
interaction involving the whole πꢀsystem of the electron rich nitrato ligand.
In Figure 5 we show the representation of selfꢀassembled dimer found in the solid state of
compound 2 that is governed by two symmetrically related O–H···Cl interactions. Moreover the
methyl groups of the MeOH ligands form C–H···π interactions (at 2.61 Å of the closest C atom
of the ring). C–H···H–C interactions are likely present involving the Hꢀatoms of the methyl
groups since they are close to each other. The C–H···H–C interaction has been recently studied
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in depth by Alvarez and coworkers. Although dihydrogen contacts in alkanes are among the
weakest intermolecular interactions (∼−0.4 kcal/mol for methane dimer), these interactions are
cumulative and resulting in larger dimerization energies in some cases (e.g. long open chains).
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For instance the complexation energy computed for the dimer of nꢀhexane is −4.5 kcal/mol. In
addition, the association energies for dimers of some polyhedranes (tetrahedrane, adamantane,
octahedrane, cubane and dodecahedrane) are also strong, reaching −3.0 kcal/mol for
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dodecahedrane. We have computed the molecular electrostatic potential MEP surface of
compound 2 in order to rationalize the formation of the electrostatically driven interactions (see
Figure 5B). It can be observed that the most positive region corresponds to the hydroxyl group of
the MeOH due to the enhancement of the acidity of the H atom upon coordination to Ni(II).
Moreover, the most negative region correspond to the chlorido ligands thus the formation of the
O–H···Cl Hꢀbond is electrostatically very favored.
To evaluate the intricate combination of interactions observed in the selfꢀassembled dimer of 2,
we have used several theoretical models (using the crystallographic coordinates) that are shown
in Figure 5C, D. We have used DFT calculations at the BP86ꢀD3/def2ꢀTZVP level of theory
since it is a good compromise between the accuracy of the method and the size of the system.
The interaction energy of the selfꢀassembled dimer (ꢁE = –35.6 kcal/mol, Figure 5B) is very
1
large basically due to the contribution of both Hꢀbonding interactions. In an effort to estimate the
contribution of the weak C–H···π and C–H···H–C interactions, we have computed an additional
model where the methanol molecules have been replaced by water ligands (see small arrows
Figure 5D). As a result the interaction is reduced to ꢁE = –29.8 kcal/mol that is the contribution
2
of the Hꢀbonding interactions, confirming their strong nature as anticipated by the MEP analysis.
The contribution of the weaker C–H···π and C–H···H–C interactions can be estimated by
difference, which is –5.8 kcal/mol. In order to characterize the interactions shown in Figure 5,
we have computed the non covalent interaction (NCI) plot of this compound. The NCI plot is a
visualization index that enables identification and visualization of non covalent interactions
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efficiently. The NCI analysis allows an assessment of host–guest complementarity and the extent
to which weak interactions stabilize a complex. The information provided is essentially
qualitative, that is, which molecular regions interact. The representation of the NCI plot
computed for compound 2 is shown in Figure 5E. An extended region can be observed between
the aromatic rings and the methyl groups of the methanol ligands, thus characterizing the C–
H···π interaction (the green surface corresponds to weak interaction). Small isosurfaces are also
present between the chlorido and the hydroxyl groups that confirm the existence of both
hydrogen bonding interactions. Finally, a green isosurface is also observed between the methyl
groups that confirm the existence of the C–H···H–C interactions.
Hirshfeld Surface analysis
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Supramolecular interactions are further investigated using Hirshfeld Surface analysis. Complexes
1 and 2 are mapped over dnorm (range of ꢀ0.1 to 1.5Å), shape index (range of ꢀ1.0 – 1.0Å) and
curvedness (range of ꢀ4.0 – 0.4) respectively and presented in figure 6 and figure S7 respectively.
During mapping surfaces are kept transparent for visualization of different supramolecular
interactions. For Complex 1, Hꢀbonding interactions between the O atom of nitrate ion and H
atoms of aromatic ring of oꢀvaniline has been predominantly found as bright red area in the
Hirshfeld surfaces. Other longer and weaker interactions appeared as light colour in the surfaces.
Fingerprint plots consist of all type of intermolecular interactions. So, fingerprint plots need to be
decomposed to have idea of individual contacts. In the decomposed fingerprint plot,
complementary regions are obtained where one molecule acts as a donor (de > di) (bottom left of
fingerprint plot) and the other as an acceptor (de < di) (bottom right of fingerprint plot). For
complex 1, O...H/H...O, N...H/H...N and H…H contacts comprise 29.7%, 2.8% and 46.1% of the
total Hirshfeld surface where O···H interactions comprise around 14.3% of the total Hirshfeld
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surface and the H···O interactions comprise around 15.4% of the total Hirshfeld surface. In the
decomposed fingerprint plot of complex 1, O···H interactions are represented by a spike (d =
i
0.92 Å, d = 1.22 Å) in the bottom left (donor) area where as H···O interactions are represented
e
by a spike (d = 1.21 Å, d = 0.91 Å) in the bottom right (acceptor) region (Figure S8).For
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complex 2, O...H/H...O, Cl...H/H...Cl and H…H contacts comprise 5.4%, 15.9% and 57.8% of
the total Hirshfeld surface where Cl···H interactions comprise around 6.3% of the total Hirshfeld
surface and the H···Cl interactions comprise around 9.6% of the total Hirshfeld surface. In the
decomposed fingerprint plot of complex 2, Cl···H interactions are represented by a spike (d =
i
0.85 Å, d = 1.45 Å) in the bottom left (donor) area where as H···Cl interactions are represented
e
by a spike (d = 1.44 Å, d = 0.86 Å) in the bottom right (acceptor) region (Figure S8).
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Life Time Measurements
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Lifetime data of the complex 1 was studied at 298 K in acetonitrile solution upon excited at 368
nm. The average fluorescence decay life time has been measured for the complex 1 using the
given formula (τ = a τ + a τ , where a and a are relative amplitude of decay process). The
f
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2 2
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average fluorescence lifetime of complex is 0.3244 nSec. (Figure 7, Table S1)
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Concluding remarks
We have synthesized and structurally characterized one trinuclear cadmium (II) (1) and one
di(phenoxido)ꢀbridged dinuclearcadmium(II)–nickel(II) (2) complexes derived from a
bicompartmental (N2O4) Schiff base ligand. Crystal structure of complex 2 has proved
preferential selection of inner core of the N2O4 donor Schiff base ligand by 3d metal ion in
comparison with a 4d metal ion. The supramolecular assemblies observed in the solid state
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architectures of both complexes features have been further investigated theoretically using DFT
calculations. Supramolecular structure of complex 1 exhibits remarkable π–hole and C–H···π
interactions. Moreover, complex 2 exhibits weak C–H···H–C interactions between Hꢀatoms of
closely spaced methyl groups along with other nonꢀcovalent interactions. The theoretical
study,by means of the NCI plot, has confirmed the existence of these interactions which have
been rationalized using MEP surfaces. More importantly, we have calculated the energetic
contribution of each interaction, which can be helpful to develop scoring functions. Hirshfeld
surface mapping and fingerprint plotting have been done to visualize the close contacts
qualitatively.
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Acknowledgment
A. S. gratefully acknowledges the financial support of this work by the DST, India (Sanction No.
SERB/F/1855/2015ꢀ16 date 04/07/2015) and Innovative Research Activity under XII Plan
General Development Assistance, UGC. The authors also acknowledge the use of the DSTꢀ
funded National Single Crystal Xꢀray Diffraction Facility at the Department of Chemistry,
Jadavpur University, Kolkataꢀ700032, India for Xꢀray crystallographic studies. A. F. gratefully
acknowledges the financial support of this work by the DGICYT of Spain (projects CTQ2014ꢀ
57393ꢀC2ꢀ1ꢀP and CONSOLIDER INGENIO 2010 CSD2010ꢀ00065, FEDER funds). A. F.
thanks the CTI (UIB) for free allocation of computer time.
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Appendix A. Supplementary data
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CCDC 1062044ꢀ1062045 contain the supplementary crystallographic data for complexes 2 and 1
respectively. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223ꢀ336ꢀ033; or
email:deposit@ccdc.cam.ac.uk.
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10 Notes & References
a
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Department of Chemistry, Jadavpur University, Kolkata- 700032, India.
E-mail: asaha@chemistry.jdvu.ac.in; amritasahachemju@gmail.com;Tel. +91ꢀ33ꢀ2457294
b
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Departament de Química, Universitat de les Illes Balears, Crta. De Valldemossa km 7.5, 07122
Palma (Baleares), Spain.
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E-mail: toni.frontera@uib.es.
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[1] E. Tsuchida, K. Oyaizu, Coord. Chem. Rev., 2003, 237, 213.
[2] L. Canali and D. C. Sherrington, Chem. Soc. Rev., 1999, 28, 85.
[3] J. Tisato, F. Refosco and F. Bandoli, Coord. Chem. Rev., 1994, 135, 325.
[4] C. Adhikary, S. Koner, Coord. Chem. Rev., 2010, 254, 2933.
[5] K.C. Gupta, A.K. Sutar, Coord. Chem. Rev., 2008, 252, 1420.
[6] K.L. Gurunatha, T.K. Maji, Inorg. Chem., 2009, 48, 10886.
[7] T.K. Maji, G. Mostafa, R. Matsuda, S. Kitagawa, J. Am. Chem. Soc., 2005, 127, 17152.
[8] E.C. Niederhoffer, J.H. Timmons, A.E. Martell, Chem. Rev., 1984, 84, 137.
[9] M.D. Allendorf, C.A. Bauer, R.K. Bhakta, R.J.T. Houk, Chem. Soc. Rev., 2009, 38, 1330.
1
9

RSC Advances
Page 20 of 39
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DOI: 10.1039/C6RA04428J
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
[10] S. Thakurta, C. Rizzoli, R.J. Butcher, C.J. GómezꢀGarcía, E. Garribba, S.Mitra, Inorganica
Chimica Acta, 2010, 363, 1395.
[11] K. Agapiou, M.L. Mejía, X. Yang, B.J. Holliday, Dalton Trans., 2009, 4154.
[12] S. Thakurta, J. Chakraborty, G. Rosair, J. Tercero, M.S. El Fallah, E. Garribba, S. Mitra,
Inorg. Chem., 2008, 47, 6227.
[13] F. Franceschi, E. Solari, R. Scopelliti, C. Floriani, Angew. Chem. Int. Ed., 2000, 39, 1685.
[14] T. Fujinami, R. Kinoshita, H. Kawashima, N. Matsumoto, J.H. Harrowfield, Y.
Kim, J. Incl. Phenom. Macrocycl. Chem., 2011, 71, 463.
[15] D. Cunningham, P. McArdle, M. Mitchell, N.N. Chonchubhair, M. O’Gara, F.
Franceschi, C. Floriani, Inorg. Chem., 2000, 39, 1639.
[16] M. Mousavi, V. Bereau, J.ꢀP. Costes, C. Duhayon, J.ꢀP. Sutter, CrystEngComm., 2011, 13,
5908.
[17] F.Z.C. Fellah, J.ꢀP. Costes, F. Dahan, C. Duhayon, J.ꢀP. Tuchagues, Polyhedron, 2007, 26,
4209.
[18] S. Sarkar, S. Mohanta, RSC Adv., 2011, 1, 640.
[19] S. Hazra, S. Sasmal, M. Nayak, H.A. Sparkes, J.A.K. Howard, S. Mohanta,
CrystEngComm., 2010, 12, 470.
[20] A.D. Khalaji, H. StoekliꢀEvans, Polyhedron, 2009, 28, 3769.
[21] K. Kubono, K. Tani, K. Yokoi, Acta Crystallogr., Sect. E, 2012, 68, m1430.
[22] P. Seth, L. K. Das, M. G. B. Drew, and A. Ghosh, Eur. J. Inorg. Chem., 2012, 2232.
4
4
46
47
[23] B. Gillon, C. Cavata, P. Schweiss, Y. Journaux, O. Kahn, D. Schneider, J. Am. Chem. Soc.,
1989, 111, 7124.
4
48
[24] D.ꢀH. Shi, Z.ꢀL. You, C. Xu, Q. Zhang, H.ꢀL. Zhu, Inorg. Chem. Commun., 2007, 10, 404.
2
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Page 21 of 39
RSC Advances
View Article Online
DOI: 10.1039/C6RA04428J
4
4
4
4
4
4
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4
4
4
4
4
4
4
4
4
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51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
[25] A. Gutierrez, M.F. Perpinan, A.E. Sanchez, M.C. Torralba, M.R. Torres, Inorg. Chim. Acta,
2010, 36, 1837.
[26] S. Oz, J. Titiš, H. Nazir, O. Atakol, R. Bocˇa, I. Svoboda, H. Fuess, Polyhedron, 2013, 59,
1.
[27] R. Ruiz, F. Lloret, M. Julve, J. Faus, M.C. Munoz, X. Solans, Inorg. Chim. Acta, 1993, 213,
261.
[28] S. Oz, R. Kurtaran, C. Arici, U. Ergun, F.N.D. Kaya, K.C. Emregul, O. Atakol, D. Ulku, J.
Therm. Anal. Calorim., 2010, 99, 363.
[29] A. Biswas, M. Ghosh, P. Lemoine, S. Sarkar, S. Hazra, S. Mohanta, Eur. J. Inorg. Chem.,
2010, 3125.
[30] D.G. Branzea, A. Guerri, O. Fabelo, C. RuizꢀPerez, L.ꢀM. Chamoreau, C. Sangregorio, A.
Caneschi, M. Andruh, Cryst. Growth Des., 2008, 8, 941.
[31] M. Nayak, R. Koner, H.ꢀH. Lin, U. Florke, H.ꢀH. Wei, S. Mohanta, Inorg. Chem., 2006, 45,
10764.
[32] P. Chakraborty, S. Mohanta, Polyhedron, 2015, 87, 98.
[33] A. Jana, R. Koner, T. Weyhermueller, P. Lemoine, M. Ghosh, S. Mohanta, Inorg. Chim.
Acta, 2011, 375, 263.
[34] L.K. Das, S.ꢀW. Park, S.J. Cho, A. Ghosh, Dalton Trans., 2012, 41, 11009.
[35] S. Biswas, S. Naiya, C.J. GómezꢀGarcía, A. Ghosh, Dalton Trans., 2012, 41, 462.
[36] A. Chakraborty, B.K. Ghosh, J. RibasꢀArino, J. Ribas, T.K. Maji, Inorg. Chem., 2012, 51,
6440.
[37] J.ꢀP. Sutter, S. Dhers, R. Rajamani, S. Ramasesha, J.ꢀP. Costes, C. Duhayon, L.Vendier,
Inorg. Chem., 2009, 48, 5820.
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93
94
[38] R. Maurice, L. Vendier, J.ꢀP. Costes, Inorg. Chem., 2011, 50, 11075.
[39] H. Wang, D. Zhang, Z.–H. Ni, X.u. Li, L. Tian, J. Jiang, Inorg. Chem., 2009, 48, 5946.
[40] S. Hino, M. Maeda, K. Yamashita, Y. Kataoka, M. Nakano, T. Yamamura, H. Nojiri, M.
Kofu, O. Yamamurod, T. Kajiwara, Dalton Trans., 2013, 42, 2683.
[41] M. Maeda, S. Hino, K. Yamashita, Y. Kataoka, M. Nakano, T. Yamamura, Takashi
Kajiwara, Dalton Trans., 2012, 41, 13640.
[42] X. Yang, R.A. Jones, V.Lynch, M.M. Oye, Archie L. Holmes,
Dalton Trans., 2005, 849.
[43] F. Cimpoesu, F. Dahan, S. Ladeira, M. Ferbinteanu, J.ꢀP. Costes, Inorg. Chem., 2012, 51,
11279.
[44] J.ꢀP. Costes, T. Yamaguchi, M. Kojima, L. Vendier, Inorg. Chem., 2009, 48, 5555.
[45] J.ꢀP. Costes, B. Donnadieu, R. Gheorghe, G. Novitchi, J.ꢀP. Tuchagues, L. Vendier,
Eur. J. Inorg. Chem., 2008, 5235.
[46] S. Dhers, S. Sahoo, J.ꢀP. Costes, C. Duhayon, S. Ramasesha, J.ꢀP. Sutter,
CrystEngComm., 2009, 11, 2078.
[47] A. Jana, S. Majumder, L. Carrella, M. Nayak, T. Weyhermueller, S. Dutta, D. Schollmeyer,
E. Rentschler, R. Koner, S. Mohanta, Inorg. Chem., 2010, 49, 9012.
[48] R. Koner, G.ꢀH. Lee, Y. Wang, H.ꢀH. Wei, S. Mohanta, Eur. J. Inorg. Chem., 2005, 1500.
[49] A.W. Kleij, M. Lutz, A.L. Spek, P.W.N. M. van Leeuwen and J.N.H. Reek, Chem.
Commun., 2005, 3661; b) S.J. Wezenberg, E.C. EscuderoꢀAd´an, J. BenetꢀBuchholz and A.W.
Kleij, Chem.Eur. J., 2009, 15, 5695; c) M. Kuil, I. M. Puijk, A. W. Kleij, D. M. Tooke, A. L.
Spek and J.N.H. Reek, Chem. Asian J., 2009, 4, 50; d) S. Akine, Y. Morita, F. Utsuno, and T.
Nabeshima, Inorg. Chem., 2009, 48, 10670; e) J.K.ꢀH. Hui and Mark J. MacLachlan, Dalton
2
2

Page 23 of 39
RSC Advances
View Article Online
DOI: 10.1039/C6RA04428J
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
95
96
97
98
99
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
Trans., 2010, 39, 7310; f) A.C.W. Leung, J.K.ꢀH. Hui, J. H. Chong and M.J. MacLachlan,
Dalton Trans., 2009, 5199; g) P.D. Frischmann, A.J. Gallant, J.H. Chong, and M.J. MacLachlan,
Inorg. Chem., 2008, 47, 101.
[50] P.G. Cozzi, Angew. Chem., Int. Ed., 2003, 42, 2895; F.H. Zelder and J. Rebek Jr., Chem.
Commun., 2006, 753.
[51] E.C. EscuderoꢀAd´an, J. BenetꢀBuchholz and A.W. Kleij, Inorg. Chem., 2007, 46, 7265.
[52] a) S.J. Wezenberg, A.W. Kleij, Angew. Chem., Int. Ed., 2008, 47, 2354; b) A.W. Kleij,
Chem. Eur. J., 2008, 14, 10520; c) H.L.C. Feltham,; S. Brooker, Coord. Chem. Rev., 2009, 253,
1458; d) A.W. Kleij, Dalton Trans., 2009, 4635; e) S. Akine,; T. Nabeshima, Dalton Trans.,
2009, 10395; f) M. Yamamura, H. Miyazaki, M. Iida, S. Akine, and T. Nabeshima , Inorg.
Chem., 2011, 50, 5315.
[53] a) J. Miao, Y. Nie, C. Hub, Z. Zhang, G. Li, M. Xu and G. Sun, J. Mol. Struct., 2012, 97,
1014; b) C. A. Bessel, R. F. See, D. L. Jameson, M. R. Churchill and K. J. Takeuchi, J. Chem.
Soc., Dalton Trans., 1992, 3223; c) K. F. Bowes, I. P. Clark, J. M. Cole, M. Gourlay, A. M. E.
Griffin, M. F. Mahon, L. Ooi, A. W. Parker, P. R. Raithby, H. A. Sparkes and M. Towrie,
CrystEngComm, 2005, 7, 269; d) J. E. Beves, P. Chwalisz, E. C. Constable, C. E. Housecroft, M.
Neuburger, S. Schaffner and J. A. Zampese, Inorg. Chem. Commun., 2008, 11, 1009; e) S. K.
Dey and G. Das, Cryst. Growth Des., 2010, 10, 754.
[54] a) A. Bauzá, T. J. Mooibroek, A. Frontera, ChemPhysChem., 2015, 16, 2496; b) J.
Echeverría, G. Aullón, D. Danovich, S. Shaik, S. Alvarez, Nat. Chem., 2011, 3, 323; c) D.
Danovich, S. Shaik, F. Neese, J. Echeverría, G. Aullón, S. Alvarez, J. Chem. Theory Comput.,
2013, 9, 1977.
2
3

RSC Advances
Page 24 of 39
View Article Online
DOI: 10.1039/C6RA04428J
5
5
5
5
5
5
5
5
5
5
5
5
5
5
17
18
19
20
21
22
23
24
25
26
27
28
29
30
[55] a) H.B. Burgi, Inorg. Chem., 1973, 12, 2321; b) H.B. Burgi, J.D. Dunitz, E. Shefter, J. Am.
Chem. Soc., 1973, 95, 5065; c) H.B. Burgi, J.D. Dunitz, J.M. Lehn, G. Wipff, Tetrahedron,
1974, 30, 1563.
[56] P. Sjoberg, P. Politzer, J. Phys. Chem., 1990, 94, 3959.
[57] L.M. Azofra, I. Alkorta, S. Scheiner, Theor. Chem. Acc., 2014, 133, 1586.
[58] a) A. Bauzá, R. Ramis, A. Frontera, J. Phys. Chem. A, 2014, 118, 2827; b) A. Bauzá, T. J.
Mooibroek, A. Frontera, Chem. Commun., 2015, 51, 1491.
[59] a) G.S. nchezꢀSanz, C. Trujillo, M. Solimannejad, I. Alkorta, J. Elguero, Phys. Chem. Chem.
Phys., 2013, 15, 14310; b) J.E. Del Bene, I. Alkorta, J. Elguero, J. Phys. Chem. A, 2013, 117,
6893.
[60] a) M.G.B. Drew, R.N. Prasad, R.P. Sharma, Acta Crystallogr. Sect. C, 1985 41 1755; b) K.
Iida, I. Oonishi, A. Nakahara, Y. Komoyama, Bull. Chem. Soc. Jpn., 1970, 43, 2347.
[61] G.M. Sheldrick, SAINT, Version 6.02, SADABS, Version 2.03, Bruker AXS Inc.,
Madison, Wisconsin, 2002.
5
5
5
31
32
33
[62] G.M. Sheldrick, SADABS: Software for Empirical Absorption Correction, University of
Gottingen, Institute fur Anorganische Chemieder Universitat, Gottingen, Germany, 1999ꢀ2003.
[63] G. M. Sheldrick, Acta Cryst., 2008, A64, 112.
5
34
[64] R. Ahlrichs, M. Bär, M. Häser, H. Horn and C. Kölmel, Chem. Phys. Lett., 1989, 162, 165.
5
5
5
5
35
36
37
38
[65] A. Bauzá, A. Terrón, M. BarcelóꢀOliver, A GarcíaꢀRaso and A. Frontera, Inorg. Chim.
Acta., 2015, DOI: 10.1016/j.ica.2015.04.028; b) D. Sadhukhan, M. Maiti, G. Pilet, A. Bauzá, A.
Frontera, S. Mitra, Eur. J. Inorg. Chem., 2015, 11, 1958; c) M. Mirzaei, H. EshtiaghꢀHosseini, Z.
Bolouri, Z. Rahmati, A. Esmaeilzadeh, A. Hassanpoor, A. Bauza, P. Ballester, M. Barcelóꢀ
2
4

Page 25 of 39
RSC Advances
View Article Online
DOI: 10.1039/C6RA04428J
5
5
5
5
39
40
41
42
Oliver, J. T Mague, Behrouz Notash and A. Frontera, Cryst. Growth Des., 2015, 15, 1351; d) P.
Chakraborty, S. Purkait, S. Mondal, A. Bauzá, A. Frontera, C. Massera and D. Das,
CrystEngComm., 2015, 17, 4680.
[66] S. F. Boys and F. Bernardi, Mol. Phys., 1970, 19, 553.
5
5
43
44
[67] J. ContrerasꢀGarcía, E. R. Johnson, S. Keinan, R. Chaudret, JꢀP.Piquemal, D. N. Beratan,
W. Yang, J. Chem. Theory and Comput., 2011 7 (3), 625.
5
5
5
45
46
47
[68] S. K. Wolff, D. J. Grimwood, J. J. McKinnon, D. Jayatilaka, M. A. Spackman, Crystal
Explorer
3.1,
University
of
Western
Australia,
Perth,
Australia,
2007,
http://hirshfeldsurfacenet.blogspot.com.
5
48
[69] J. J. McKinnon, D. Jayatilaka, M. A. Spackman, Chem. Commun., 2007, 3814.
5
5
5
5
5
5
5
5
5
5
5
5
49
50
51
52
53
54
55
56
57
58
59
60
[70] R. Biswas, P. Kar, Y. Song, A. Ghosh, Dalton Trans., 2011, 40, 5324.
[71] B. Dutta, P. Bag, U. Florke, K. Nag, Inorg. Chem., 2005, 44, 147.
[72] S. Banthia, A. Samanta, J. Phys. Chem. B, 2006, 110, 6437.
[73] W. Chen, Q. Peng, Y. Li, Cryst. Growth Des., 2008, 8, 564.
[74] Z. Li, A. Dellali, J. Malik, M. Motevalli, R.M. Nix, T. Olukoya, Y. Peng, H. Ye, W.P.
Gillin, I. Herna´ndez, P.B. Wyatt, Inorg. Chem., 2013, 52, 1379.
[75] S. Majumder, L. Mandal, S. Mohanta, Inorg. Chem., 2012, 51, 8739.
[76] P. Yang, X.X. Wu, J.Z. Huo, B. Ding, Y. Wang, X.G. Wang, CrystEngComm., 2013, 15,
8097.
[77] a) P. Politzer, J. S. Murray, T. Clark, Phys. Chem. Chem. Phys., 2010, 12, 7748; b) L. M.
Azofra, I. Alkorta, S. Scheiner, Theor. Chem. Acc., 2014, 133, 1586; c) A. Bauza, R. Ramis, A.
Frontera, J. Phys. Chem. A, 2014, 118, 2827; c) A. Bauzá, T. J. Mooibroek, A. Frontera, Chem.
2
5

RSC Advances
Page 26 of 39
View Article Online
DOI: 10.1039/C6RA04428J
5
5
5
5
61
62
63
64
Commun., 2015, 51, 1491; d) G. SánchezꢀSanz, C. Trujillo, M. Solimannejad, I. Alkorta, J.
Elguero, Phys. Chem. Chem. Phys., 2013, 15, 14310; e) J. E. Del Bene, I. Alkorta, J. Elguero, J.
Phys. Chem. A, 2013, 117, 6893.
5
5
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Table1 Crystal parameters and selected refinement details for complexes 1 and 2
Compound
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
a (Å)
1
2
C H Cd3N O
C H CdCl N NiO
7
3
8
40
6
14
21 30
2
2
1141.99
296(2)
664.47
273
Monoclinic
Monoclinic
P 21/n
P2 /c
1
20.0254(6)
8.8925(2)
23.9742(6)
90
10.2934
15.9246(5)
15.9021(5)
90
b (Å)
c (Å)
α(°)
β(°)
γ(°)
100.745(1)
90
102.203(2)
90
3
Volume (Å )
4194.37(19)
4
2547.75(15)
4
Z
–
3
Dcalc (g cm )
1.809
1.685
Absorption
1.518
1.821
–
1
coefficient (mm )
F(000)
2264
1304
θ Range for data
collection (°)
Reflections
1.03ꢀ24.55
1.83ꢀ30.23
2
6
58462
43947

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5
5
5
5
5
5
67
68
69
70
71
72
collected
Independent
6990/0.0324
7304/0.0310
5773
reflections / Rint
Observed
5933
reflections [I>2σ(I)]
Data / restraints /
parameters
6990/ 0/553
1.027
7304/1/319
1.043
Goodnessꢀofꢀfit on
2
F
Final
R1 = 0.0238;
wR2 = 0.0622
R1 = 0.0351;
wR2 = 0.0936.
indices[I>2σ(I)]
5
5
5
73
74
75
R indices (all data)
R1 = 0.0320;
wR2 = 0.0736
R1 = 0.0485;
wR2 = 0.1025
1.217/ꢀ0.513
Largest diff. peak / 0.450/ꢀ0.312
–
3
hole (e Å )
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Table2. Selected bond lengths (Å) and bond angles (°) for complex 1
Complex 1
Cd3–O1
Cd3 –O2
Cd3 –O3
Cd3 –O4
Cd1–N1
Cd1 –N2
Cd1 –O2
Cd1 –O3
2.744(3)
2.260(2)
2.243(3)
2.495(3)
2.241(3)
2.257(3)
2.235(2)
2.224(2)
Cd3–O1A
Cd3 –O2A
Cd3 –O3A
Cd3 –O4A
Cd2–N1A
Cd2 –N2A
Cd2 –O2A
Cd2 –O3A
2.762(3)
2.276(2)
2.268(2)
2.521(2)
2.237(3)
2.262(3)
2.216(2)
2.215(2)
2
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Cd1 –O5
2.543(4)
Cd2 –O5A
2.474(3)
Cd3ꢀꢀꢀꢀCd1
3.556
Cd3ꢀꢀꢀꢀCd2
3.546
O1– Cd3–O2
O2– Cd3–O3
O3– Cd3–O4
N1– Cd1–N2
N1– Cd1–O2
N2–Cd1–O3
O2–Cd1–O3
O5–Cd1–O6
Cd3–O2–Cd1
C9ꢀC10ꢀC11
C9AꢀC10AꢀC11A
61.41(7)
73.85(8)
66.23(8)
90.2(1)
83.49(9)
83.0(1)
74.70(8)
51.7(1)
104.54(8)
116.10
O1A– Cd3–O2A
O2A– Cd3–O3A
O3A– Cd3ꢀ O4A
N1A– Cd2–N2A
N1A– Cd2–O2A
N2A–Cd2–O3A
O2A–Cd2–O3A
O5A–Cd2–O6A
Cd3–O2A–Cd2
Cd3–O3A–Cd2
60.34(8)
73.70(8)
65.41(8)
88.4(1)
84.6(1)
82.28(9)
75.91(8)
50.9(1)
104.27(9)
104.59(8)
121.15
5
77
Table 3. Selected bond lengths (Å) and bond angles (°) for complex 2
Complex 2
Ni1–N1
2.026(3)
Ni1–O1
Ni2 –O3
Cd1–O2
Cd1–O4
2.003(2)
1.993(2)
2.528(2)
2.525(3)
Ni1 –N2 2.033(3)
Cd1–O1 2.262(2)
Cd1 –O3 2.257(2)
Ni1–O5
2.158(3)
Cd1–Cl1 2.4811(8)
Cd1–Cl2 2.452(1)
Ni1 –O6 2.142(3)
Ni1ꢀꢀꢀꢀCd1 3.390
2
8

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N1–Ni1–N2
O3– Ni2–N2
N1– Ni1–O3
O1– Cd1–O3
O1– Cd1–O2
C9ꢀC10ꢀC11
98.7(1)
N1– Ni1–O1
90.5(1)
91.1(1)
Cl1– Cd1–O2
O1– Ni1–O3
O3– Cd1–O4
Cl1– Cd1–Cl2
Cl1– Cd1–O4
86.59(6)
79.94(9)
65.45(8)
120.42(3)
88.46(7)
169.5(1)
69.25(8)
65.39(8)
115.8(5)
5
78
5
5
79
80
Scheme 1.The route to the syntheses of complexes 1 and 2
5
5
5
5
5
5
5
81
82
83
84
85
86
87
2
9