Experimental and quantum chemical studies of a new organic proton transfer compound, 1H-imidazole-3-ium-3-hydroxy-2,4,6-trinitrophenolate

Article abstract of DOI:10.1016/j.molstruc.2017.10.024

A new proton transfer compound, 1H-imidazole-3-ium-3-hydroxy-2,4,6-trinitrophenolate (IMHTP), was crystallized by slow evaporation-solution growth technique. ¹H and ¹³C NMR spectral studies confirm the molecular structure of the grown crystal. Single crystal X-ray diffraction study confirms that IMHTP crystallizes in monoclinic system with space group P2₁/c. Thermal curves (TG/DTA) show that the material is thermally stable up to 198 °C. The crystal emits fluorescence at 510 nm, proving its utility in making green light emitting materials in optical applications. The stable molecular structure was optimized by Gaussian 09 program with B3LYP/6-311++G(d,p) level of basis set. The frontier molecular orbital study shows that the charge transfer interaction occurs within the complex. The calculated first-order hyperpolarizability value of IMHTP is 44 times higher than that the reference material, urea. The electrostatic potential map was used to probe into electrophilic and nucleophilic reactive sites present in the molecule.

Full text of DOI:10.1016/j.molstruc.2017.10.024

Accepted Manuscript
Experimental and quantum chemical studies of a new organic proton transfer
compound, 1H-imidazol-3-ium-3-hydroxy-2,4,6-trinitrophenolate
P. Dhamodharan, K. Sathya, M. Dhandapani
PII:
S0022-2860(17)31355-8
10.1016/j.molstruc.2017.10.024
MOLSTR 24395
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 6 July 2017
Revised Date: 5 October 2017
Accepted Date: 6 October 2017
Please cite this article as: P. Dhamodharan, K. Sathya, M. Dhandapani, Experimental and quantum
chemical studies of a new organic proton transfer compound, 1H-imidazol-3-ium-3-hydroxy-2,4,6-
trinitrophenolate, Journal of Molecular Structure (2017), doi: 10.1016/j.molstruc.2017.10.024.
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Graphical Abstract

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Experimental and quantum chemical studies of a new organic proton transfer
compound, 1H-imidazol-3-ium-3-hydroxy-2,4,6-trinitrophenolate
P. Dhamodharan, K. Sathya and M. Dhandapani *
Department of Chemistry, Sri Ramakrishna Mission Vidyalaya College of Arts and Science,
Coimbatore-641 020, Tamil Nadu, India.
*Corresponding Author’s E-mail: srmvdhandapani@gmail.com; Phone: +91 94420 01232.
Keywords:
Proton transfer, Hydrogen bonding, Hyperpolarizability, Optical materials.
Abstract
A
new proton transfer compound, 1H-imidazol-3-ium-3-hydroxy-2, 4,
6
1
trinitrophenolate (IMHTP), was crystallized by slow evaporation-solution growth technique. H
and 13C NMR spectral studies confirm the molecular structure of the grown crystal. Single
crystal X-ray diffraction study confirms that IMHTP crystallizes in monoclinic system with
space group P21/c. Thermal curves (TG/DTA) show that the material is thermally stable up to
198 °C. The crystal emits fluorescence at 510 nm, proving its utility in making green light
emitting materials in optical applications. The stable molecular structure was optimized by
Gaussian 09 program with B3LYP6-311++g(d,p) level of basis set. The frontier molecular
orbital study shows that the charge transfer interaction occurs within the complex. The calculated
first order hyperpolarizability value of IMHTP is 44 times higher than that the reference
material, urea. The electrostatic potential map was used to probe into electrophilic and
nucleophilic reactive sites present in the molecule.

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1. Introduction
Organic materials are attractive due to their electronic and optical properties. The
molecular structure of organic molecules can be easily designed and modified for suitable
applications [1]. The growth of organic crystals has gained much importance for the fabrication
of technologically important devices in electronics and optical applications [2-5]. Organic
molecules are composed of skeletons with hetero atoms such as N, O and S etc other than carbon
hydrogen atoms. The fact behind their use in optical applications is due to the generation of
hydrogen bonding net work in the crystalline state.
Hydrogen bonding plays a vital role in chemical, catalytic and biochemical processes,
chemical engineering, as well as in supramolecular chemistry [6-9]. Hydrogen bonding is the
widely used non-covalent interaction in many organic materials due to their aggregation into
self-assembly. The design and construction of multi-component supramolecular synthons
utilizing hydrogen bonding is one of the rapidly developing areas in supramolecular synthesis
[10-12]. Organic Lewis acid - Lewis base combinations have gained popularity in recent years
because they have the potential to alter and optimize physical properties such as crystalline form,
solubility and stability [13-17]. Heterocyclic compounds containing nitrogen atom in particular
are useful in the construction of optically important crystals. Imidazole is an organic heterocyclic
nitrogenous compound containing two electron rich nitrogen atoms. These electronegative
nitrogen atoms can be centers of hydrogen bonding networks which can stabilize the crystal
system. The alternate nitrogen atoms in imidazole can involve in charge transfer activity for
improving optical property when coupled with suitable acidic components. Imidazole can act a
Lewis base and form a stable complex with styphnic acid. We have already reported the
synthesis and application of a few organic crystals in the combination of styphnic acid and
heterocyclic bases [18-24].
In this present work, we report structural, experimental, quantum chemical analysis and
thermal investigations of a new organic molecular crystal, 1H-imidazol-3-ium-3-hydroxy-2,4,6-
trinitrophenolate involving proton transfer mechanism.

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2. Experimental section
2.1 Synthesis of 1H-imidazol-3-ium-3-hydroxy-2,4,6-trinitrophenolate (IMHTP)
Commercially available 1H-imidazole (sigma Aldrich-analytical grade) and laboratory
synthesized styphnic acid were taken as the starting materials for the synthesis of IMHTP. The
styphnic acid and 1H-imidazole were dissolved separately in equimolar ratio in pure methanol
and mixed thoroughly together. The resulting solution was stirred well for 10 minutes to get a
yellow colour precipitate. The suspended impurities were removed through a Whatmann 41
grade filter paper. Bright yellow coloured crystals were harvested after ten days from the
saturated solution in acetone. The purity of the crystal was improved by repeated
recrystallizations. The reaction scheme for the synthesis is represented below,
2.2 Physico-chemical characterization of IMHTP
Elemental analysis was performed in a flash EA 1112 fully automatic trace element
analyzer. Molecular weight of C9H7N5O8 is 313.20. The experimental and calculated values in
percentage are: Found: C, 34.65; H, 2.21; N, 22.26, Calculated for C, 34.52; H, 2.25; N, 22.36.
The experimental and calculated values are in good agreement with each other and this
observation indicates that the IMHTP is free from impurities. The FT-IR spectrum (Fig. 1) of
IMHTP was recorded in the region 4000-400 cm-1 using a JASCO FT/IR 5300 infrared
spectrometer. The FT-IR wave numbers (cm-1) of selected bands are: υ=3305 (O-H), 3083 (N-
H), 1592 (NO2)asy, 1377 (NO2)sy, 1445 (C=C), 849 (C-H), 1620 (C=N), 1299 (C-N), 1269 (C-O).
The FT-Raman wave numbers (cm-1) are : υ=1579 (NO2)asy, 1318 (NO2)sy, 1450 (C=C), 827 (C-
H), 1624 (C=N), 1334 (C-N), 1296 (C-O). 1H and 13C NMR spectroscopic data were recorded on
a Bruker Avance 400 MHz FT-NMR instrument with tetramethylsilane (TMS) as an internal
1
standard using DMSO-d6 solvent. H NMR chemical shifts δ (in ppm) of various protons are:

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13.1 (s, OH, NH), 8.6 (s, for both H5 & H6), 9.1 (s, H3), 7.7 (s, H2). The chemical shifts (δ ppm)
13
in C NMR are: 156.2 (C1 and C3), 126.1 (C5), 135.8 (C2, C4 and C6), 134.8 (C7), 119.7 (C8
and C9). It is observed that the signal for OH and NH protons submerge and appear as a broad
1
1
hump in the deshielded region in H NMR spectrum [24]. The H and 13C NMR spectra and
theoretical values are given in Fig. 2 and Table 1 respectively.
3. Results and discussion
3.1 Structural determination of IMHTP
The crystallographic data of IMHTP have been collected at 298 K on a Bruker SMART
APEX CCD with area detector system (MoKα = 0.7103 Å). Data reduction, absorption
correction and refinements were carried out by SAINT PLUS, SADABS and SHELXL-97
software, respectively [33-34]. Non-hydrogen atoms were refined with anisotropic thermal
parameters.
The ORTEP diagram of IMHTP is shown in Fig. 3a. The compound IMHTP crystallizes
in monoclinic system with space group P21/c. The lattice parameters are a = 6.0000(12) Å,
b = 13.100(3) Å, c = 15.000(3) Å, α =90°, β = 94.00 (3)° and γ= 90°. The unit cell volume (V)
is= 1176.1(4) Å3 and the number of molecules in unit cell (Z) is 4. The total no of reflections
collected are 6459. The crystallographic parameters IMHTP are shown in the Table 3. The bond
lengths of C1-C2 and C1-C6 are 1.429 and 1.443 Å, respectively which are longer than the
standard aromatic (C-C single bond length (1.40 Å) value. The bond length of C1-O7 in IMHTP
is 1.235 Å which is shorter than that of normal bond length C-O (1.339 Å). The C1-O7 value is
intermediate between the single and double bonds. It is clear that a proton migrates from one of
the hydroxyl groups of styphnic acid to the hetero nitrogen atom of imidazole during the
reaction. The loss of hydroxyl proton at the O7 leads to specific electron delocalization around
C1 atom.
The electron withdrawing nitro group, decreases the electron density of the C atom linked
to it leading an increase in the bond angles of C(1)-C(2)-C(3) and C(1)-C(6)-C(5) with values
126.9 and 122.9°, respectively. The asymmetric unit consists of one imidazolium cation and one
styphnate anion. All the three nitro groups possess planar geometry. It is interesting note that

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only one of the nitro group plane deviates greatly from the normal benzene ring at an angle
67.95° (O2-N1-O1). The other two nitro groups are slightly off-plane with respect to aromatic
benzene ring in styphnate moiety. The deviation angles of O3-N2-O4 and O5-N3-O6 are 1.94
and 6.10°, respectively. Due to the large deviation in (O2-N1-O1) nitro group, the styphnate
anion undergoes different kinds of covalent and non-covalent interactions like hydrogen bond,
van der Waals interactions including bifurcated and trifurcated arrangements. The styphnic acid-
Lewis base combinations are stabilized through numerous hydrogen bonding interactions in the
crystal lattice. Packing view diagram of IMHTP is shown in Fig. 4.
Hydrogen bonding network between the donor and acceptor moieties of IMHTP is shown
in Fig. 4. Supramolecules composed of strong N-H…O and O-H…O hydrogen bonds and weak
C-H…O bonds are known to play a considerable role in determining the packing of organic
crystals [37]. The hydrogen atom (H3) present in C7 is involved in a trifurcated hydrogen bond
with nitro oxygen atoms of styphnic acid through weak C-H…O (C7-H3…O1/O3/O4)
interactions. The other hydrogen atom (H5) of imidazole forms bifurcated hydrogen bonding
with neighbouring deprotonated oxygen atom (O7) and nitro oxygen (O6) of styphnic acid (C8-
H5…O7/O6).
Furthermore, the cationic imidazole moiety makes hydrogen bond with neighbouring
anionic moiety of styphnic acid. The imidazole hydrogen atom (H7A) forms bifurcated
hydrogen bonding with two oxygen atoms of neighbouring styphnate (N5-H7A…O3/O5).
Another strong N-H…O interaction is observed between hydrogen atom (H4) of imidazole and
nitro oxygen atom (O2) of styphnate anion. In the imidazole cation, all the hydrogens involve in
hydrogen bonding with neighbouring anionic moiety. The hydrogen atom (H6) of imidazole
cation forms hydrogen bonding with neighbouring oxygen atom of styphnate anion through weak
C9-H6…O6 interactions. Apart from these interactions, the C-H…O interaction is also observed
between the two styphnate anions through C5-H2…O9 interactions.
3.2 Optical studies
It is a common requirement for any material to be used in optical applications that the
crystal should possess a wide transparency in visible region and the lowest possible cut off
wavelength [26]. The recorded UV-Vis absorption spectrum is shown in Fig. S1. The complex

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shows absorptions at 216, 332 and 401 nm. The absorptions at 216 and 332 nm are due to the n–
π* transitions of the complex. The absorption at 401 nm is due to the π-π* transition. The n–π*
and π-π* transitions of the complex are responsible for charge transfer and aromatic conjugation.
The yellow colour of the crystal is due to the presence of chromophore, nitro (NO2) and
auxochromes hydroxyl group (-OH group) in styphnic acid. The transition is due to promotion of
an electron from the higher energy state of the donor (imidazole) to the lower energy state of the
acceptor (styphnic acid). The UV-Vis and UV-Vis-NIR spectra of IMHTP are shown in Fig. 2b.
The IMHTP crystal is transparent from visible to NIR region an with optical cut-off at 400 nm.
The absence of absorption between 470 and 900 nm shows that the crystal is transparent in this
region attesting its suitability in frequency doubling applications.
3.3 Emission spectral analysis
Photoluminescence studies are useful in understanding the various types of energy
transition states in a molecule [27-30]. The photoluminescence spectrum of IMHTP crystal was
recorded in a Horiba Jobin-Yvon-FL3-22 Flurolog spectroflurometer. Fluorescence is expected
generally in molecules that are aromatic or contain conjugated double bonds with a high degree
of resonance stability [31]. The fluorescence emission spectrum of IMHTP crystal is shown in
Fig. S2. The emission spectrum of the compound was measured in the wavelength range between
400 and 620 nm. The compound shows peak at 500 nm (λex= 440 nm) in the emission spectrum.
The broad peak at 500 nm indicates that IMHTP has a green fluorescence emission property
revealing the use of the material in solid state lighting and display applications [32].
3.4 Thermal analysis
Thermal analysis was carried out to study the thermal stability and melting point of the
grown crystal. Thermal analyses (TG/DTA) were performed by a Mettler Toledo Star SW 8.10
TG/DTA thermal analyzer between 30 and 500 °C under nitrogen atmosphere at a heating rate of
20 °C per minute. The TG/DTA thermogram of the crystal is shown in Fig. S3. From the TG
curve, it is observed that there was no loss of weight around 100 °C. This confirms the absence
of water in any form in the sample. A sharp exothermic peak at 198 °C clearly indicates the
complete decomposition of the crystal. The mass of the IMHTP remains unchanged till 198 °C

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and the sample loses its weight almost completely around 230 °C. TG curve shows a single stage
weight loss which is due to complete degradation of the crystal into fragments and its subsequent
volatilization into various gaseous fractions like CO, CO2, NO2 and, NH3. Absence of either
endothermic or exothermic peaks below 198 °C indicates that there was no phase transition
before the melting point. The sharpness of the exothermic peak infers good degree of
crystallinity of the grown crystal. Therefore, IMHTP crystal is suitable for optical applications
up to 198 °C.
3.5 Optimized geometry
The optimized molecular structure of IMHTP was calculated using
B3LYP-6-311++ G(d,p) basis set and is shown in Fig. 3b. The structural parameters obtained
from the DFT method are presented in Table 2. Theoretically optimized bond lengths and angles
are larger than the experimental ones since the theoretical calculation were done assuming
isolated molecule in gaseous phase.
3.6 Frontier molecular orbital analysis
The FMO analysis furnishes a platform for understanding the phenomenon of charge
transfer through optical molecular excitations [35,36]. The chemical hardness and reactivity of
an optical material can be predicted from HOMO-LUMO energy gap. The calculated energies of
HOMO and LUMO of IMHTP are -6.82eV and -3.15eV, respectively and the energy gap is
found to be 3.66 eV. The ionization energy (I) and electron affinity (A) can be expressed through
HOMO and LUMO orbital energies as I = -EHOMO = 6.824 eV and A = -ELUMO = 3.156 eV. The
global hardness (η) is predicted by the relation η = (I-A)/2 = 1.834 eV. The electron affinity can
be used in combination with ionization energy to give electronic chemical potential ꢀ = - (EHOMO
+ ELUMO)/2 = 4.95 eV. The global electrophilicity index (ω) is given by ω= ꢀ2/2η = 6.69 eV.
The HOMO-LUMO plots of IMHTP are shown in Fig. 5 along with reactants molecules,
imidazole and styphnic acid. In IMHTP, the HOMO electrons are localized on aromatic ring of
styphnate anionic moiety (electron acceptor) and LUMO electrons are localized over upper part
of the aromatic ring and two nitro groups leaving the third one free. Thus, the HOMO-LUMO
transition implies an electron density transfer within the styphnate moiety through conjugated
path. The HOMO-LUMO energy gap of styphnic acid, imidazole and IMHTP are 4.19, 6.05 and

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3.66 eV, respectively. The energy gap in IMHTP is smaller than the reactant molecules which is
a clear evidence for the stability of the product formed. The smaller gap facilitates strong
hydrogen bonding in IMHTP which leads to the larger values of first order hyperpolarizability
[37].
3.7 Molecular electrostatic potential map
In order to predict the nature of reactive sites in IMHTP, molecular electrostatic potential
(MEP) analysis was undertaken. [38]. The MEP map for IMHTP crystal is shown in Fig. 6. The
yellow, blue and green colour indicated as negative, positive and zero electrostatic potential. The
negative region (yellow colour) of the MEP surface covers the styphnate moiety that represents
the electrophilic reactivity sites and positive region (blue colour) spread over imidazole cation
that indicates the nucleophilic reactivity sites. In the reactant molecules, the positive potential is
spread over the N-H group of imidazole and benzene ring of styphnic cid while the negative
potential localized over the nitro groups of styphnic acid and nitrogen atom of the imidazole
molecule. The contour maps and MEP of the reactants, the product confirms the proton transfer
from the proton donor to the acceptor. The MEP of IMHTP confirms the presence of various
types of inter and intramolecular hydrogen bonding interactions [39].
3.8 Mulliken atomic charges
The electronic charge on the individual atoms in a molecule decides the bonding pattern.
The atomic charge values were obtained by the Mulliken population analysis [40]. The structure
of IMHTP with Mulliken atomic charges are shown in Fig. 7. The calculated results show that all
the oxygen atoms of the styphnate and nitrogen atoms of the imidazolium are encompassed by
negative charges. The positive charge is located over the carbon and hydrogen atoms of IMHTP
molecule. Larger magnitude of negative charge is observed for nitrogen atoms of imidazole
(N25 = -0.6809 e and N27 = -0.6407 e) and deprotonated oxygen atom (O29 = -0.5501 e) of the
styphnate moiety. It is also observed that the nitrogen atoms of nitro group of styphnate moiety
have smaller positive charges due to the delocalization of π electrons. The highest positive
charge is identified in hydrogen atom (H2) (0.4042 e) of the unprotonated hydroxyl group of
styphnate. Lesser positive charges are also found in the C7 (0.4091 e) and N27 (0.4348 e) atoms.

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3.9 First order hyperpolarizability
During theoretical evaluation of a compound for nonlinear optical activity, calculation of
first hyperpolarizability values are important. In this context, the dynamic first
hyperpolarizability (β) of the title compound has been calculated using DFT method at the
B3LYP/6-311++G (d,p) level of basis set. It is well known that the higher values of dipole
moment, molecular polarizability and first order hyperpolarizability are important for more
active NLO properties. A substantial delocalization of charges in a particular direction would
bring about high value of hyperpolarizability in that direction. In IMHTP the highest value is
found in βxxx direction. The maximum β value may be due to π-electron cloud movement from
donor to acceptor which makes the molecule highly polarized with possible intramolecular
charge transfer.
The calculated total first-order polarizability (β) and the dipole moment (ꢀ) values of
IMHTP are 5.724 x 10-30 esu and 15.475 debye, respectively. The β value is approximately 44
times greater than that of urea. The hyperpolarizability value of IMHTP molecule plays an
important role not only in the building up of the molecular structure but also in the enhancement
of optical properties. The high β value is consequence of numerous intra and inter-molecular
hydrogen bonds IMHTP. This great magnitude of the first hyperpolarizability suggests IMHTP
can be used in the development of NLO materials. A comparison of first order
hyperpolarizability for the constituents of IMHTP is listed in the Table 4.
3.10 Hirshfeld surface analysis
Hirshfeld surface analysis allows a quick and easy identification of the significant
intermolecular interactions (C-H…π, O-H…O, H…H etc.) map on the molecular surface.
CrystalExplorer, a computer program was used for calculation of Hirshfeld surfaces and 2D
fingerprint plots [41]. The two-dimensional (2D) fingerprint plots obtained from Hirshfeld
analysis provides a good amount of information on pattern of packing and atom-atom contacts.
Fig. 8 represents 2D fingerprint plots and its percentage contributions of IMHTP crystal. The
larger circular depressions (deep red) visible on the side of the 3D Hirshfeld surfaces correspond
to the significant hydrogen bonding contacts. While the red color points indicate the short
contacts of H...H, N…H and H...O interactions. The proportion of O…H/H…O interactions

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covers 52% of the total Hirshfeld surfaces with two distinct spikes in the 2D fingerprint plots
indicating hydrogen bonding interactions are the most significant interactions in the crystal. The
H…H interactions, which are reflected in the middle of scattered points in the 2D fingerprint plot
comprise 7.8% of the total Hirshfeld surfaces. The presence of nitro and hydroxy groups is
responsible for O…O (13.3%) and N…O/O…N (4.2 %), interactions in IMHTP. The
O…C/C…O (5.6 %) and C…C (4.6 %) interactions are also observed in IMHTP. Hirshfeld
surface analysis of IMHTP crystal demonstrated that O…H/H…O interaction is more prominent.
Conclusion
A new proton transfer crystal, 1H-imidazol-3-ium-3-hydroxy-2,4,6 trinitrophenolate
(IMHTP) was synthesized by slow evaporation-solution growth method. The FT-IR and NMR
spectroscopic analysis confirm the formation of the IMHTP. The compound has a green emission
property so that it can be used for solid state lighting and display applications. The IMHTP
crystallizes in monoclinic system with space group P21/c. The asymmetric unit consists of one
imidazolium cation and one styphnate anion. The stability of crystal structure is governed by the
numerous bifurcated and trifurcated strong N-H…O and O-H…O hydrogen bonds and weak
C-H…O bonds networks. The IMHTP is thermally stable up to 198 °C. The optimized stable
molecular structure of IMHTP was calculated using B3LYP-6-311++ G(d,p) basis set. The
HOMO –LUMO energy gap is smaller (3.66 eV) in the product IMHTP, than the reactant
molecules indicating the stability of the product. The contour maps of the reactants and MEP
illustrates the proton transfer from the proton donor to the acceptor. Mulliken charge analysis
indicates that the highest positive charge is found in hydrogen atom (0.4942 e) of the free
hydroxyl group of styphnate while the highest negative is present in the carbon atom (0.4091e)
having O- atom. The calculated total first-order polarizability (β) and the dipole moment (ꢀ)
values are 5.724 x 10-30 esu and 15.475 debye respectively. The β value is approximately 44
times greater than that of the standard reference material, urea. The large transmittance, lower
cut off wavelength, excessive hydrogen bonding, lowest band gap and high β value indicate that
IMHTP material is an excellent candidate for optoelectronic applications.

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Acknowledgements
One of the authors, M. Dhandapani, would like to thank the University Grants
Commission (UGC), New Delhi, India for the financial support (Major Research Project Grant
No. 43-200/2014(SR) to carry out the research work. P. Dhamodharan, thanks the
Dr. R. Nagarajan, School of Chemistry and UGC Networking Centre, Hyderabad, for awarding
visiting research fellowship.
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Table captions
Table 1 Experimental and theoretical, 1H and 13C NMR of chemical shifts for IMHTP [
δ ppm]
Table 2. Comparison of experimental and calculated bond lengths (Å) and bond angles (°)
of IMHTP
Table 3. Crystal data and structure refinement for IMHTP
Table 4. Comparison of first order hyperpolarizability for the constituents of IMHTP

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Table 1 Experimental and theoretical, 1H and 13C NMR of chemical shifts for IMHTP [
B3LYP/6-311g(d,p)
δ ppm]
Atom
positions
H1
Experimental
Gas
DMSO
12.1289
8.9849
Methanol
12.1283
8.9842
Water
12.1296
8.9856
13.1
7.7
12.1240
8.9325
H2
NH
H3
NH
H6
H5
C3
C2
C1
C4
C5
C6
C7
C8
C9
-
18.0692
8.9839
17.2614
8.7591
17.2714
8.7611
17.2521
8.7573
9.1
-
8.4845
9.3017
9.2904
9.3122
8.6
6.9324
7.3237
7.3184
7.3286
8.6
7.7967
7.5928
7.5965
7.5894
156.2
135.5
156.2
135.5
126.1
135.5
134.8
119.7
119.7
159.5190
142.1514
168.8187
141.3290
131.7889
125.3815
141.1361
120.3899
127.6505
159.9056
142.2155
169.7316
142.1117
133.2855
126.9653
140.5094
124.3238
124.5675
159.8942
142.2118
169.7176
142.0960
133.2561
126.9316
140.5093
124.2698
124.6191
159.9163
142.2190
169.7448
142.1266
133.3132
126.9971
140.5098
124.3740
124.5191

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Table 2. Comparison of experimental and calculated bond lengths (Å) and bond angles (°) of
IMHTP
O(9)-C(3)
N(3)-O(6)
N(3)-O(5)
N(3)-C(6)
O(3)-N(2)
C(6)-C(5)
1.322
1.204
1.215
1.452
1.24
1.35
1.266
1.273
1.453
1.3
O(6)-N(3)-O(5)
O(6)-N(3)-C(6)
O(5)-N(3)-C(6)
C(5)-C(6)-C(1)
C(5)-C(6)-N(3)
C(1)-C(6)-N(3)
O(7)-C(1)-C(2)
O(7)-C(1)-C(6)
C(2)-C(1)-C(6)
C(6)-C(5)-C(4)
C(3)-C(2)-C(1)
C(3)-C(2)-N(1)
C(1)-C(2)-N(1)
O(2)-N(1)-O(1)
O(2)-N(1)-C(2)
O(1)-N(1)-C(2)
O(4)-N(2)-O(3)
O(4)-N(2)-C(4)
O(3)-N(2)-C(4)
O(9)-C(3)-C(2)
O(9)-C(3)-C(4)
C(2)-C(3)-C(4)
C(5)-C(4)-N(2)
C(5)-C(4)-C(3)
N(2)-C(4)-C(3)
N(4)-C(8)-C(9)
O(6)-N(3)-O(5)
121.9
120.2
117.9
123
123.2
119.2
117.5
122.3
117.3
120.3
123.1
122
117.1
120
1.358
1.444
1.219
1.235
1.429
1.38
1.372
1.449
1.264
1.279
1.444
1.4
C(6)-C(1)
120.8
127.2
112
O(4)-N(2)
C(1)-O(7)
C(1)-C(2)
114.6
120.8
123.6
118.9
117.4
122.6
120
121.5
126.9
117.3
115.7
123.7
117.7
118.6
120.6
120.3
119.1
119.4
124
C(5)-C(4)
C(2)-C(3)
1.367
1.454
1.211
1.212
1.411
1.421
1.296
1.353
1.317
1.359
1.332
107.5
107.3
107.2
109.6
1.322(3)
1.397
1.445
1.258
1.281
1.424
1.427
1.387
1.366
1.332
1.354
1.396
107.4
106.1
109.3
109.7
1.35
C(2)-N(1)
N(1)-O(2)
N(1)-O(1)
N(2)-C(4)
C(3)-C(4)
117.2
121.2
120
C(8)-N(4)
C(8)-C(9)
118.6
119.4
122.5
118
C(7)-N(4)
C(7)-N(5)
C(9)-N(5)
N(4)-C(7)-N(5)
N(5)-C(9)-C(8)
C(9)-N(5)-C(7)
C(8)-N(4)-C(7)
O(9)-C(3)
116.6
119.4
120
118.3
120.3
121.2
107.2
123.2
120.6
108.4
121.9(3)
RMSD values for Bond lengths and Bond angles are 0.017 Å and 1.556°, respectively.
*Calculated from optimized structure from DFT.

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Table 3. Crystal data and structure refinement for IMHTP
Empirical formula
Formula weight
Temperature
C9 H7 N5 O8
313.20
293(2) K
Wavelength
0.71073 Å
Crystal system
Space group
Monoclinic
P21/c
Unit cell dimensions
a = 6.0000(12) Å
b = 13.100(3) Å
c = 15.000(3) Å
α= 90°.
β= 94.00(3)°.
γ = 90°.
Volume
Z
1176.1(4) Å3
4
Density (calculated)
1.769 Mg/m3
Absorption coefficient
F(000)
0.158 mm-1
528
Crystal size
0.18 x 0.15 x 0.12 mm3
2.07 to 26.31°.
Theta range for data collection
Index ranges
-7<=h<=7, -16<=k<=16, -18<=l<=18
Reflections collected
Independent reflections
Completeness to theta = 26.31°
12093
2368 [R(int) = 0.0268]
98.8 %
Refinement method
Full-matrix least-squares on F2
2368 / 0 / 200
Data / restraints / parameters
2
Goodness-of-fit on F
1.067
Final R indices [I>2sigma (I)]
R indices (all data)
R1 = 0.0718, wR2 = 0.2266
R1 = 0.0759, wR2 = 0.2322
-3
0.615 and -0.710 e.Å
Largest diff. peak and hole

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Table 4. Comparison of first order hyperpolarizability for the constituents of IMHTP
Parameters
b3lyp/6-311g
‘β’ tensor
components
xxx
IMHTP
ꢀx
ꢀy
ꢀz
-15.081
-2.535
-2.366
15.475
-74.070
6.665
-148.651
11.54
2.193
-604.781
-53.293
-51.805
-51.295
-38.224
-11.863
-23.269
5.239
xxy
xyy
yyy
zxx
xyz
zyy
xzz
yzz
ꢀ
αxx
αxy
αyy
αxz
αyz
αzz
α0
0.183
-125.735
116.1523
17.191*10-24 esu
zzz
β total
-0.767
5.724*10-30 esu
α

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Figure captions
Fig. 1. FT-IR and Raman spectra of IMHTP
1
Fig. 2. H and 13C NMR spectra of IMHTP
Fig. 3. (a) ORTEP plot (50% probability level) and (b) Optimized molecular structure of IMHTP
Fig. 4. Packing view and Hydrogen bonding network of IMHTP
Fig. 5. Frontier molecular orbitals of IMHTP
Fig. 6. Molecular electrostatic potential of IMHTP
Fig. 7. Mulliken charge distribution chart of IMHTP
Fig. 8. 2D fingerprint plots and its percentage contributions of IMHTP

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Fig. 1. FT-IR and Raman spectra of IMHTP

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1
Fig. 2. H and 13C NMR spectra of IMHTP

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Fig. 3. (a) ORTEP plot (50% probability level) and (b) Optimized molecular structure of IMHTP

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Fig. 4. Packing view and Hydrogen bonding network of IMHTP

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Fig. 5. Frontier molecular orbitals of IMHTP

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Fig. 6. Molecular electrostatic potential of IMHTP

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Fig. 7. Mulliken charge distribution chart of IMHTP

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Fig. 8. 2D fingerprint plots and its percentage contributions of IMHTP