.
Angewandte
Communications
DOI: 10.1002/anie.201205439
Multifunctional Organic Materials
A Multifunctional Porous Organic Schottky Barrier Diode**
Sasanka Dalapati, Rajat Saha, Sankar Jana, Astam K. Patra, Asim Bhaumik, Sanjay Kumar, and
Nikhil Guchhait*
For the past two decades scientists have been engaged in
designing and synthesizing porous metal–organic frameworks
(MOFs) capable for gas and solvent adsorption.[1,2] From the
middle of the last decade, researchers have tried to include
many functional properties in a single framework. Thus
multifunctional MOFs[3–5] were developed as materials with
a set of well-defined properties, for example, porosity and
magnetism, porosity and electrical conductivity, or porosity
and optical properties. This synergism, resulting from the
combination of two different functionalities, opens up the way
to new multifunctional materials.
In the last two years, a large number of porous covalent
organic frameworks were reported by different research
groups worldwide and they have shown that in porous organic
materials (POMs) a degree of porosity can be achieved which
is higher than in MOFs.[6–8] In the case of 3D MOFs, several
modifications are needed to achieve higher porosity, such as
generation of unsaturated metal centers (UMCs) and for-
mation of hydrophobic channels. In contrast to 3D MOFs,
adsorption by supramolecular 3D POMs occurs in several
steps because of their structural flexibility.[8–10] Regarding
materials with a similar degree of porosity, the molecular
weight of POMs is lower than that of MOFs and zeolites.
Thus, it can be said that the adsorption properties of porous
organic materials (POMs) are better than those of other
porous materials like MOFs and zeolites because of their high
flexibility, multistep adsorption process, and low molecular
weight.
studies. This material is porous after removal of the dime-
thylformamide (DMF) and the water guest molecules. The
porosity of this material has been studied by N2 adsorption at
77 K. Further, to show the multifunctional character of the
material, we have studied its I-V characteristic and guest-
dependent luminescence property.
Slow Et2O vapor diffusion in DMF solution of ANPPIT
affords yellow rhombic crystal suitable for X-ray diffraction at
room temperature (see the Supporting Information).[16] The
diffraction analysis indicates that the compound crystallizes in
an achiral C2/c space group (see Table S1 in the Supporting
Information). Each asymmetric unit contains half of the
ANPPIT moiety with one DMF and 1.5 water guest mole-
cules. Within the molecular structure, p-nitroaniline (PNA)
units are nearly perpendicular to the basic pyrrolo[3,4-
f]isoindole-1,3,5,7-tetraone moiety (Figure 1), that forms
Figure 1. ORTEP view of ANPPIT without guest molecules (DMF and
water) at a 30% probability.
Recently, some research groups were engaged in estab-
lishing multifunctional properties in POMs.[11–15] Here, we also
synthesized a multifunctional porous organic material, 2,6-
bis-(2-amino-5-nitro-phenyl)-pyrrolo[3,4-f]isoindole-1,3,5,7-
tetraone (ANPPIT, see the Supporting Information), and
characterized this material by single-crystal X-ray diffraction
analysis, NMR and IR spectroscopy, PXRD, and thermal
a 3D architecture by H-bonding and p interactions (Figur-
es S1, S2 and Tables S2, S3 in the Supporting Information).
Each molecular unit is connected to four other units through
À
N1 H2···O4 hydrogen-bonding interactions and thus a 3D
supramolecular architecture is formed (Figure S1). During
the packing process, a 1D channel is generated along the
crystallographic c axis (Figure 2). The diameter of the channel
is 17.3 ꢀ 7.0 ꢁ2. Water and DMF guest molecules persist
within the channels through supramolecular hydrogen-bond-
ing interactions (Figure S3). The guest water molecules are
connected by hydrogen-bonding interactions leading to the
formation of a 1D helical chain (Figure S4).
[*] S. Dalapati, S. Jana, Dr. N. Guchhait
Department of Chemistry, University of Calcutta
92 A.P.C. Road, Kolkata (India)
E-mail: nguchhait@yahoo.com
R. Saha, Dr. S. Kumar
Department of Physics, Jadavpur University, Kolkata (India)
Thermal analysis reveals that at 1208C all DMF and water
guest molecules are removed and the evacuated framework is
stable up to 2308C without any further loss of weight
(Figure S5). The powder X-ray diffraction (PXRD) pattern,
obtained after removal of the guest molecules by heating at
1208C for 3 h, indicates that the evacuated framework
remains crystalline (Figure S6). However, there is a change
in the PXRD patterns of different materials which leads to the
conclusion that a structural transformation occurs upon
removal of the guest molecules followed by the formation
A. K. Patra, Dr. A. Bhaumik
Department of Materials Science, Indian Association for the
Cultivation of Science, Kolkata (India)
[**] N.G. acknowledges the DST (project number SR/S1/PC/26/2008).
S.D. and S.J. acknowledge UGC for a fellowship. A.K.P. and R.S. is
thankful to the CSIR, New Delhi. We thank S.K.’s colleague, Dr. P. P.
Ray, for valuable discussion.
Supporting information for this article is available on the WWW
12534
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2012, 51, 12534 –12537