Copper(II) complexes with box or flower type morphology: Sustainability versus perishability upon catalytic recycling

Article abstract of DOI:10.1016/j.ica.2016.06.012

Graphical abstract Selective oxidation of p-chlorobenzyl alcohol to p-chlorobenzaldehyde is carried out by new copper(II) complexes of a benzimidazolyl schiff base ligand. Efficiency of oxidation depends on the morphology of the complexes; box type morphology sustains catalysis upon recycling to a greater extent in comparison to the flower type.

Full text of DOI:10.1016/j.ica.2016.06.012

Accepted Manuscript
Research paper
Copper(II) complexes with Box or Flower type Morphology: Sustainability
versus Perishability upon catalytic recycling
Ravinder Kumar, Anjana Yadav, Kuldeep Mahiya, Pavan Mathur
PII:
S0020-1693(16)30322-X
http://dx.doi.org/10.1016/j.ica.2016.06.012
ICA 17103
DOI:
Reference:
To appear in:
Inorganica Chimica Acta
Received Date:
Revised Date:
Accepted Date:
25 February 2016
10 May 2016
4 June 2016
Please cite this article as: R. Kumar, A. Yadav, K. Mahiya, P. Mathur, Copper(II) complexes with Box or Flower
type Morphology: Sustainability versus Perishability upon catalytic recycling, Inorganica Chimica Acta (2016),
doi: http://dx.doi.org/10.1016/j.ica.2016.06.012
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Copper(II) complexes with Box or Flower type Morphology: Sustainability
versus Perishability upon catalytic recycling
Ravinder Kumar, Anjana Yadav, Kuldeep Mahiya and Pavan Mathur*
Department of Chemistry, University of Delhi, Delhi-110007, India.
Abstract
Copper(II) complexes derived from a benzimidazolyl schiff base ligand are used
heterogeneously for the selective oxidation of p-chlorobenzyl alcohol to p-chlorobenzaldehyde.
Complex (1) shows rectangular box type morphology while complex (2) shows a flower like
morphology with micropetals. Powder X-ray diffraction pattern upon reuse of catalyst (1) shows
loss of peaks associated with planes 001 and 100 suggesting preferential exposure of these planes
during the catalytic cycle, while the catalyst (2) shows loss in activity with planes associated
with 011 and 021 (axis b & c) implying a non-preferential activity. It is interesting to note that
the box type morphology (1) sustains catalysis upon recycling to a greater extent in comparison
to the flower type (2).
Keywords: Benzimidazolyl schiff base copper(II) complex, rectangular/flower, Morphology,
Heterogeneous Catalysis
Corresponding Author
Tel: +91 1127667725X1381; Fax: +91 1127666605
*
E-mail: pavanmat@yahoo.co.in (P. Mathur)
1

1
. Introduction
Heterogeneous catalysis provides an opportunity to understand the effect of surface shape/size on
the reactivity of the catalyst [1, 2]. Surface chemistry studies have shown that the catalytic
selectivity is mainly dependent on the coordination of the substrate on surface [3] and has been
found to be affected by the exposed crystallographic facets [4, 5]. Morphology of the catalyst
determines the crystal planes that could affect catalysis [6, 7]. The type of morphology like rod,
sphere, flower, cuboid and rectangle are known to affect the catalytic reactions since they expose
different active planes [8-13]. Few studies have been reported wherein changes in size
distribution of the catalyst after recycling have been reported along with catalytic activity [14-
1
5]. Several studies are reported that utilise Cu(II) or Cu(I) halides or insitu generated
phenanthroline copper complexes for the oxidation of benzylic alcohols to aldehydes. Some of
these reports carry out reactions under refluxing condition under molecular oxygen and in
solvent media like H O, benzene, DMF-benzene with yields between 55-95%.[16, 17,18-21].
2
In the present study we have synthesized two new monomeric copper(II) complexes with a
benzimidazolyl schiff base ligand. The single crystal X-ray diffraction (SCXRD) reveals that
copper(II) complex forms a distorted square planer geometry. Both the complexes are employed
for the oxidation of p-chlorobenzyl alcohol to the corresponding aldehyde in dichloromethane
using TBHP as oxidant monitored by UV spectral study. The complexes are insoluble in
dichloromethane and act as catalyst under heterogeneous conditions at room temperature. The
reaction conditions employed are much milder in the present case, and room temperature
reaction is carried out with product yields that are comparable to some of the earlier reports. The
catalyst is recovered and recycled; the changes that occur in the morphology of the catalyst
during reaction are analyzed through scanning electron microscopy (SEM), Powder-XRD, X-ray
photon spectroscopy (XPS).
2. Experimental
2
.1. Materials and Methods
All chemicals o-Phenylenediamine (Thomas Baker, Mumbai), β-Alanine(Merck), 2-Hydroxy-1-
Naphaldehyde (Alfa-Aesar), K CO (Thomas Baker), CuCl .5H 0 (Thomas Baker), KCNS,
2
3
2
2
alcohol(Merck) and 70% Tert.butyl hydroperoxide (Lancaster) were used as obtained. 2-
aminoethylbenzimidazole dihydrochloride (AB.2HCl) was prepared according to the procedure
as reported by Cescon and Day [22].
2

2
.2. Physical Measurements
Elemental analysis of the ligand and their complexes were obtained on VARIO EL III from
USIC, University of Delhi, India. IR spectra were recorded on a Perkin-Elmer FT-IR-2000
-1
spectrometer using KBr discs in the range of 400-4000 cm . UV-Vis spectra were recorded in
DMF with a Shimadzu UV-Vis-1601 spectrometer. Cyclic Voltammetry studies were performed
on BAS CV 50W instrument. The cyclic voltammograms were obtained in DMSO: CH CN
3
containing 0.1 M Tetrabutyl ammoniumperchlorate (TBAP) as a supporting electrolyte. A three-
electrode configuration composed of a Pt disk working electrode, a Pt wire counter electrode,
and an Ag/AgNO reference electrode was used for the measurements. The morphological
3
changes in the copper(II) complexes was studied by scanning electron microscopy (SEM) model
FEI Quanta 200F with oxford –EDS system IE 250 X Max 80 with gold coating in SMITA
research lab IIT Delhi, India. GC-MS spectra were recorded at AIRF, JNU, New Delhi on a
GCMS-QP2010 (plus) Schimadzu instrument. The powder X-ray diffraction patterns were
recorded using High resolution D8 Discover Bruker diffractometer, equipped with point detector
(
scintillation counter), employing monochromatized Cu Kα1 radiation with a scan rate of 1.0
second/step and step size 0.02° at 298 K over the range of 2θ = 5º-35°.
3
. Synthesis and analysis
3
.1. Synthesis of Ligand and its Copper(II) complexes
[
C
20
H
17
N
3
O] (L)
The Schiff base was synthesized as reported earlier [14a]. 2-aminoethyl benzimidazolyl
dihydrochloride (AB.2HCl) was neutralized by adding requisite amount of aqueous K CO . A
stirred methanolic solution of 2-hydroxy-1-naphthaldehyde was added slowly to the above
2
3
solution. After about ½ h a yellow solid separated out. The solid was dried over P
recrystallized from acetonitrile. Melting Point 213°C, m/z 316 (M+1).
2
5
O and finally
3
.2. Synthesis of Copper(II) complexes
Cu(L)Cl].MeOH (1)
To a stirred solution of L (78 mg, 0.25 mmol) in 15 ml methanol CuCl
[
2
.2H O (43 mg 0.25
2
mmol) dissolved in 5 ml methanol was added drop wise with constant stirring and the resulting
reaction mixture was refluxed for 2 hr at room temperature. Thereafter the reaction mixture was
3

concentrated to one half of its volume on a water bath and allowed to stand at room temperature.
A green colored product formed was washed with cold methanol, filtered, air dried. The
compound analyzes for the composition C20
H
16ClCuN O. MeOH, Yield: 76%; m.p.: 215°C.
3
Single crystal suitable for XRD work were obtained by redissolving the compound in 25-30 ml
of hot MeOH and allowed to stand at room temperature. After a few days green colored crystals
separated out. Anal. Found(Calc.) for C21
H
20
N
3
2
O CuCl: C 56.57(56.63), H 4.75(4.53), N
-1
9
7
.48(9.43); Selected IR(KBr, cm ) ν(-C=N-C=C-) 1429, ν(NH)(H-bonded) 3125, ν(C=N) 1603, νC=C benzene
48; UV-Vis λmax/nm (log ε) in DMF: 271(4.3), 283(4.1), 314(4.0), 394(3.8), 634(2.3).
[
Cu(L)SCN] (2)
To a methanolic solution (10 ml) of CuCl
mmol) dissolved in 5 ml methanol was added drop wise until KCl precipitated out. The resulting
brown colored solution of Cu(SCN) solution was treated with the ligand L1 solution in
2
.2H O (43 mg, 0.25 mmol), KCNS (25 mg, 0.25
2
2
methanol. The resulting mixture was warmed at ~80°C for 3 hrs. Thereafter the brown coloured
solution so obtained was filtered and transferred to a 100 mL beaker. The solution was allowed
to stand at room temperature for few days. Brownish green coloured crystals were collected, and
air dried. They analyzed for the composition C21
H16CuN
4
OS. Yield: 72%. m.p.: 187°C
Anal. Found(Calc.) C 57.28(57.85), H 3.58(3.70), N 12.39(12.85), S 8.10(7.35); Selected
-1
IR(KBr, cm ); ν(-C=N-C=C-) 1457, ν(NH)(H-bonded) 3190, ν(C=N) 1603, νC=C benzene 738; UV-Vis
λmax/nm(log ε) in DMF: 270(3.8), 278(3.7), 313(3.5), 391(3.53, 682(1.8).
3
.3. X-ray crystallography
Single crystals of complexes (1) and (2) suitable for X-ray diffraction studies were grown by
slow evaporation in methanol. The intensity data for (1) were collected at 150(2) K on a Bruker
SMART Apex CCD diffractrometer using graphite monochromator (Mo-K
α
radiation, λ =
0
.71073 Å) from IIT Roorkee India. The intensity data for (2) was collected at 298(2) K on an
X’calibur CCD diffractometer with graphite monochromatized Mo/Kα. Radiation (λ=0.71073 Å)
from USIC, University of Delhi, Delhi, India. For (1), a total of 10759 reflections were measured
of which 3060 were unique and 2506 were considered observed (I > 2σ (I)]. For (2), a total of
1
2364 reflections were measured of which 3191 were unique and 2821 were considered
observed (I > 2σ (I)]. The data were corrected for Lorentz and polarization effects. Multi-scan
absorption correction was applied. The structure was solved by direct methods using SHELXS-
4

17
2
9
7 and refined by full-matrix least-squares refinement techniques on F , using SHELXL-97
[
23]. All calculations were done with the help of WINGX programme [24] For the molecular
graphics, the programme Diamond2 [25] and Mercury [26] were used. All non-hydrogen atoms
were refined anisotropically. All hydrogen atoms were fixed geometrically with Uiso values of
1
.2 times the Uiso values of their respective carrier atoms. The final residual index for (1) are; R
.0367, Rw 0.0820 for the observed and R 0.0869, Rw 0.0976 for all reflections using 257
0
parameters and one restraint. The final residual index for (2) are; R 0.0801, Rw 0.1891 for the
observed and R 0.0886, Rw 0.1943 for all reflections using 253 parameters and zero restraints.
Details of the crystallographic data and structure refinement for complexes (1), and (2) are given
in Table 1.
4
. Results and Discussion
4
.1. Molecular Structure Description of [Cu(L)Cl]. MeOH (1) and [Cu(L)NCS] (2)
The crystal structure of copper(II) complexes (1) and (2) shows that the ligand coordinates in a
tridentate mode with imine nitrogen of the benzimidazole ring, deprotonated napthanol oxygen
and the azomethine nitrogen of the ligand. Anionic chloride or thiocyanate also binds to copper
to complete the distorted square plane (Figure 1, Table S1) [27, 28]. It is found that the sum of
o
o
the bond angles about Cu(II) are 375 and 369 for the Cl bound and the NCS bound complexes,
suggesting that the Cu(II) atom sits slightly out of square plane. Moreover The the Cu—Cl bond
is much longer than the remaining three bond lengths of the square plane contributing to the
distortion of the geometry about Cu(II). Selected bond length and angles are given in Table S2.
The hydrogen atom that is attached to the oxygen of methanol present outside the crystal lattice
shows H-bonding with the Cl. The extended self-assembled 2D framework is formed by H-
bonding interaction (Figure S1). Similarly the hydrogen atom attached to benzimidazole nitrogen
shows intermolecular H-bonding with the sulphur of the NCS group forming an extended self-
assembled framework in complex (2) (Figure S2). The π-π stacking interactions are present in
the crystal packing of complex (1) and (2). The crystal packing of (1) and (2) viewed from the b
axis is shown in Figure S3. In complex (1) benzimidazole ring in one layer is stacked over
benzimidazole ring of neighboring molecule (distance between the centroids 3.744 Å) while
naphthol ring is stacked over naphthol ring of the neighboring molecule (distance between the
5

centroids 3.777 Å). Other layers show the same pattern. The interaction between the two layers is
weak because the distance between the centroid of benzimidazole and naphthol ring is 4.619 Å.
On the other hand complex (2) forms a zig-zag structure. Unlike complex (1), the benzimidazole
ring stacks over the naphthol ring while the naphthol ring stacks over the benzimidazole ring of
the neighboring molecule. The subsequent layers are almost equidistant from each other
(
distance between the centroids is 3.908 and 4.094 Å). The zig-zag pattern of stacking may have
some implications in the generation of petals in flower type morphology.
4
4
.2. Characterizations
.2.1. Electronic spectroscopy
The UV spectra of the ligand and complexes show absorption maxima in the range of 270-420
nm in DMF, assigned to intraligand π-π* transition of the benzimidazole moiety. The n-π*
transition is assigned to the azomethine (–N=CH-) and a LMCT from the napthanol oxygen to an
empty d-orbital of metal ion [29]. A broad but a much less intense d-d band due to copper(II) is
observed at 634 nm for complex (1) and 682 nm for complex (2).
4
.2.2. Cyclic Voltammetry
Cyclic voltammograms of both the complex were recorded in mixed CH
3
CN: DMSO (3: 2)
solution at room temperature with tetrabutylammonium perchlorate (TBAP) as supporting
electrolyte. Both the complex shows quasi-reversible peak for the couple Cu(II) ↔ Cu(I)
(
Figure S5 and Figure S6). The E1/2 values are found to be -36.5 mV for complex (1) and +49.6
mV for complex (2) respectively.
. Catalytic Activity study
5
[
Cu(L)Cl].MeOH (1) and [Cu(L)NCS] (2) were used heterogeneously for the oxidation of p-
chloro benzyl alcohol to its respective aldehyde and monitored by UV-spectroscopy Figure 2. In
a typical reaction, benzyl alcohol, catalyst, oxidant in a ratio of 5: 1: 7 respectively were mixed
o
in 15 mL dichloromethane and stirred at 35-40 C on a water bath for a 4 hrs.the reaction mixture
was centrifuged after a 4 hr reaction to isolate the copper(II) catalyst, for further reuse. The clear
filterate of the reaction mixture was checked for any dissolution of the catalyst during reaction,
no d-d band in the visible range of 500-900 nm was observed,suggesting no/minimal dissolution
6

of the copper(II) catalyst. The complexes were reused for the oxidation reaction and a decrease
in the yield of benzaldehyde was observed, as analyzed through GC-MS. Both the complexes are
reused three times and their percentage conversions for the repeat cycle are summarized in Table
1
. The oxidation of p-chlorobenzyl alcohol was monitored spectrophotometrically by measuring
the increase in the characteristic p-chlorobenzaldehyde absorption band at 256 nm as a function
of time [15a].
6
. SEM and PXRD Analysis
In order to observe the impact of surface morphology on catalysis during recycling, the catalyst
was recovered after the oxidation reaction was complete. A gold coated sample of the recovered
catalyst was prepared for SEM measurement. The SEM micrograph shows that the mononuclear
complex (1) before use as catalyst has a rectangular box like morphology where the average
length of boxes lies between 75-140 µm for complex (1) (Figure 3A). Its subsequent reuse in the
catalytic oxidation of p-chlorobenzyl alcohol causes the morphology to change to a more or less
flat 2-dimensinal boxes (wafer type) with length varying from 25-40 µm for complex (1) (Figure
3B).
The thiocyante bound mononuclear complex (2) is found to possess a flower like morphology
[
30] and contains petals. The micro-petals are flat and the length of each petal ranges from 1.3 to
rd
1
.01 µm (Figure 3C). After 3 use the petals shows a shortening in length upto 0.86 µm, while
some petals are found to conjoin together, giving rise to cluster formation (Figure 3D). The
morphology changes for the thiocyante bound monomeric complex are more apparent upon reuse
in comparison to the chloride bound complex, and may explain the sharp drop in percentage
conversion of alcohol to aldehyde that varies from 74% to 48% for complex (2). In comparison
the complex (1) upon reuse shows a change from 68% to 52% for the formation of aldehyde.
The powder XRD pattern of both the complexes also shows changes that occur after successive
use of the catalyst for the oxidation of p-chlorobenzyl alcohol to p-chlorobenzaldehyde. The
monomeric copper (II) complex (1) shows that the parent complex has sharp intense peaks at 2θ
(
hkl) 7.6(001), 8.8(010), 11.5(100), 12.7(110), 14.3(101) 17.8(002), 21.8(020) and 26.8(202).
After reuse major changes occur in the low intensity at peaks 7.6(001) and 11.5(100), each plane
exposing a single axis (a or c). The thiocyante bound complex (2) also shows sharp peak at 2θ
1
0.1(011), 11.3(021), 16.2, 24.4, 25.8(080), 29.2 and 30.6. After reuse major changes occur in
7

the low intensity of peaks at 10.1(011) and 11.3(021), both planes exposing two axis (b & c).
This suggests that the diffraction planes undergoing changes could be involved in the promotion
of catalysis for complex (1) and (2) (Figure 4).
6
.1. d-d band Variation
The d-d band spectral changes were measured by making a 3.8 mmolar solution of the used
complex (1) and measuring its visible spectra (Figure. S7). It is interesting to note that after
repeat cycles there is drop in the d-d band intensity in visible region. The complex shows a drop
in d-d band intensity by 22% upon reuse for complex (1) (Figure S7). A similar loss in d-d band
intensity is also observed for complex (2). The loss in d-d band intensity is an indication of the
formation of copper (I) during catalytic cycle and could be related to loss in catalytic activity.
Formation of Cu(I) species has been observed earlier also [31].
6
.2. X-Ray Photoelectron Spectroscopy
The [Cu(L)NCS] complex shows two main peaks at 935eV and 955eV with a satellite peak at
45eV. These peak positions have been reported to be associated with copper in +2 oxidation
9
state [32] (Figure 5). The XPS of the reused complex shows the presence of a new shoulder,
observed at 933eV (Figure 5 inset) along with peaks at 935eV, 953eV with a satellite peak at
9
42eV [33]. The appearance of a prominent shoulder at 933eV has been reported to be due to
copper in +1 oxidation state [33]. This shows that the reused complex has some proportion of
copper(I) species besides copper(II) complex.
7
. Conclusion
Catalyst (1) shows bigger rectangular boxes (120-150 µm) which change to smaller boxes (30-50
µm) as indicated by SEM after catalysis. Some planes diminish in intensity as observed by
PXRD and could be responsible for the inactivation of the catalyst. Smaller drop in percentage
conversion ≈16% upon reuse, suggesting relatively sustained catalysis upon reuse.
Catalyst (2) shows flower type morphology where the petal size change from 1.01 to 0.86 µm
upon reuse. The interaction of the catalyst with the substrate results in clustering of the petals
that possibly blocks the catalytic cycle step. Sharp change in percentage conversion from 74% to
8

4
8% upon reuse implying that there is an initial higher catalytic activity with flower type
morphology but it perishes quickly and does not sustain a higher velocity of activity upon reuse.
Since the complexes are insoluble in the medium of reaction (dichloromethane) and dissolution
of copper(II) catalyst is minimal, hence the major catalytic reaction proceeds via a heterogeneous
rather than homogeneous pathway. A tentative reaction scheme is depicted in Scheme I.
(II)
Scheme I
Acknowledgment
We gratefully acknowledge financial support from the University of Delhi, Delhi and UGC 20-
6/2010 (i) EU-IV) for providing the SRF to one of the author (Ravinder Kumar).
0
Supplementary Material
CCDC 883788 and 883786 contain the supplementary crystallorgaphic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. H-bonding interactions for both the complexes.
Crystallorgaphic data and selected bond length and angles.
9

REFERENCES
1
. (a) D. Zhang, X. Du, L. Shi, R. Gao, Dalton Trans., 41 (2012) 14455. (b) G. R. Jenness,
J. R. Schmidt, ACS Catal. 3 (2013) 2881.
2
. (a) C. Burda, X. B. Chen, R. Narayanan, M. A. El-Sayed, Chem. Rev., 105 (2005) 1025.
(
b) J. A. van Bokhoven, Chem Cat. Chem., 1 (2009) 363.
3
4
5
. R. A. Van Santen, M. Neurock, S. G. Shetty, Chem. Rev., 110 (2010) 2005.
. F. Zaera, Acc. Chem. Res., 42 (2009) 1152.
. (a) G. A. Somorjai, Chem. Rev., 96 (1996) 1223; (b) C. R. Henry, Surf. Sci. Rep., 31
(
1998) 231. (c) L. Vattuone, L. Savio, M. Rocca, Surf. Sci. Rep., 63 (2008) 101.
6
7
. (a) Y. Li, W. Shen, Chem. Soc. Rev. 43 (2014) 1543 (references there in). (b) X. Du, D.
Zhang, L. Shi, R. Gao, J. Zhang, J. Phys. Chem. C, 116 (2012) 10009.
. (a) Y. Li, Q. Liu, W. Shen, Dalton Trans., 40 (2011) 5811. (b) N. V. Long, C. M. Thi, M.
Nogami, M. Ohtaki, New, J. Chem., 36 (2012) 1320.
8
9
1
. R. Narayanan, M. A. El-Sayed, J. Am. Chem. Soc., 126 (2004) 7194.
. C. I. Carlisle, T. Fujimoto, W. S. Sim, D. A. King, Surf. Sci. 470 (2000) 15.
0. (a) J. M. Hawkins, J. F. Weaver, A. Asthagiri, Phys. Rev. B 79 (2009) 125434. (b) S. P.
Devarajan, J. A. Hinojosa, J. F. Weaver, Surf. Sci. 602 (2008) 3116.
1
1. (a) H. X. Mai, L. D. Sun, Y. W. Zhang, R. Si, W. Feng, H. P. Zhang, H. C. Liu, C. H.
Yan, J. Phys. Chem. B, 109 (2005) 24380. (b) R. Narayanan, M. A. El-Sayed, J. Phys.
Chem. B, 125 (2003) 8340.
1
1
2. (a) K. Zhou, X. Wang, X. Sun, Q. Peng, Y. Li, J. Catal., 229 (2005) 206. (b) S. Kim, S.
U. Son, S. S. Lee, T. Hyeon, Y. K. Chung, Chem. Commun., (2001) 2212.
3. (a) N. Ta, M. L. Zhang, J. Li, H. J. Li, Y. Li, W. Shen, Catal. Today, 148 (2009) 179. (b)
J. Sculz, A. Roucoux, H. Patin, Eur. J. Chem., 6 (2000) 618. (c) F. Gao, D. W.
Goodman, Annu. Rev. Phys. Chem., 63 (2012) 265.
1
0

1
1
4. (a) R. Kumar, K. Mahiya, P. Mathur, Dalton Trans., 42 (2013) 8553-8557. (b) R.
Narayanan, M. A. El-Sayed, J. Phys. Chem. B, 107 (2003) 12416.
5. (a) K. Mahiya, P. Mathur, Inorg. Chim. Act. 399 (2013) 36. (b) N. Tian, Z. Y. Zhou, S.
G. Sun, Y. Ding, Z. L. Wang, Science, 316 (2007) 732.
1
1
6. Liang, L.; Rao, G.; Sun, H.-L.; Zhang, J.-L. Adv. Synth. Catal. 2010, 352, 2371.
7. Lahtinen, P.; Ahmad, J. U.; Lankinen, E.; Pihko, P.; Leskelä, M.; Repo, T. J. Mol.
Catal. A: Chem. 2007, 275, 228.
1
1
2
2
8. Jallabert, C.; Riviere, H. Tetrahedron Lett. 1977, 18, 1215.
9. Jallabert, C.; Riviere, H. Tetrahedron 1980, 36, 1191.
0. Jallabert, C.; Lapinte, C.; Riviere, H. J. Mol. Catal. 1982, 14, 75.
1. Lahtinen, P.; Korpi, H.; Haavisto, E.; Leskelä, M.; Repo, T. J. Comb. Chem. 2004, 6,
9
67.
2
2
2. L. A. Cescon, and A. R. Day, J. Org. Chem, 27 (1962) 581.
3. Oxford Diffraction CrysAlis Software System, Ver. 1.171.32. (Oxford Diffraction Ltd.
Abingdon, UK) 2007.
2
2
2
2
4. G. M. Sheldrick, Acta Crystallogr, A64 (2008) 112. (b) A. L. Spek, J. Appl. Crstallogr,
3
6 (2003) 7.
5. G. Bergerhoff, M. Berndt, K. Brandenburg, J. Res. Natl. Inst. Stand. Technol. 101 (1996)
21.
2
6. C. F. Macrae, P. R. Edgington, P. McCabe, E. Pidcock, G. P. Shields, R. Taylor, M.
Towler, J. V. De Streek, J. Appl. Crystallogr. 39 (2006) 453.
7. (a) M. E Bluhm, M. H. Ciesielski, G. O. Walter, M. Doring, Inorg. Chem., 42 (2003)
8
878. (b) H. Wang, Y. Lang, S. Wang, Act. Cryst. E68 (2012) m540. (c) P. Talukder, A.
Datta, S. Mitra, G. Rosair, M. S. El Fallah, J. Ribas, Dalton Trans. (2004) 4161.
2
8. C. S. Rajarajeswari, R. Loganathan, M, Palaniandavar, E. Suresh, A. Riyasdeend, M. A.,
Akbarshae, Dalton Trans. 42 (2013) 8347.
2
3
9. R. Kumar. K. Mahiya and P. Mathur. Ind. J. Chem. 50A (2011) 775.
0. (a) P. Kumar, M. Gusain, R. Nagarajan, Inorg. Chem. 50 (2011) 3065. (b) G. Tong, J.
Yuan, W. Wu, Q. Hu, H. Qian, L. Li, J. Shen, CrystEngComm. 14 (2012) 2071.
1
1

3
3
1. S. Tehlan, M. S. Hundal, P. Mathur, Inorg. Chem. 43(21) (2004) 6589.
2. (a) U. G. Singh, R. T. Williamsa, K. R. Hallam, G. C. Allen, J. Solid State Chem. 178
(
2005) 3405. (b) H. Ripp, U. Weser, Bioinorg. Chem., 6 (1976) 45.
3
3. L. N. Mazalov, S. V. Trubina, G. K. Parygina, I. M. Oglezneva, E. A. Aseeva, N. V.
Brenner, E. U. Fursova, V. I. Yovcharenko, J. Struct. Chem. 47(3) (2006) 558.
Figures and Table
Figure 1. ORTEP diagram of the [Cu(L)Cl].MeOH (1) and [Cu(L)NCS] (2) drawn in 30%
thermal probability ellipsoids with atomic numbering scheme.
1
2

Figure 2. Time dependent UV-Visible absorbance spectra for the formation of p-Cl-
st
st
Benzaldehyde for every 10 min time interval. Complex (1): 1 run (2): 1 run.
A
C
B
D
Figure 3. Variation in the Morphology of complexes (1) and (2) during catalysis. A and C
rd
represents unused complex; B and D represents complex after 3 use in catalysis.
1
3

Complex (1)
Complex (2)
rd
Figure 4. PXRD pattern of complexes (1) and (2): (A) Unused complex (B) After 3 use
rd
Figure 5. XPS spectra of complex [Cu(L)NCS] (2) unused complex and after 3 use in catalysis
Inset: Blow up of formation of new peak at 933 eV generated after reuse of the catalyst.
Table
Table 1. % conversion of oxidation reaction of p-chlorobenzyl alcohol to the aldehyde of
complexes
1
4

Catalyst
Reusability
Yield (%)
st
1
use
68
52
74
48
[
[
Cu(L)Cl] (1)
rd
3
1
use
use
use
st
rd
Cu(L)NCS] (2)
3
*Based on GC-MS with naphthalene as Internal Standard
1
5

Graphical abstract
Copper(II) complexes with Box or Flower type Morphology: Sustainability
versus Perishability upon catalytic recycling
Ravinder Kumar and Pavan Mathur*
Department of Chemistry, University of Delhi, Delhi-110007, India.
TBHP
[Cu(L)SCN]
[Cu(L)(SCN)] after catalysis
1
6

Synopsis
Selective oxidation of p-chlorobenzyl alcohol to p-chlorobenzaldehyde is carried out by new
copper(II) complexes of a benzimidazolyl schiff base ligand. Efficiency of oxidation depends on
the morphology of the complexes; box type morphology sustains catalysis upon recycling to a
greater extent in comparison to the flower type.
1
7

Highlights
1
2
3
. Monomeric copper(II) complexes of a benzimidazolyl schiff base ligand.
. Oxidation of p-chlorobenzyl alcohol to p-chlorobenzaldehyde, heterogeneously.
. Rectangular box type morphology found for [Cu L Cl] while flower type with micro
petals for [Cu L SCN].
4
. Loss of PXRD peaks associated with certain planes with reuse of catalyst .
. Box type morphology sustains catalysis upon recycling compared to the flower type.
5
1
8