Structural, spectroscopic, nonlinear optical and electronic properties of calcium N-phthaloylglycinate: A combined experimental and theoretical study

Article abstract of DOI:10.1016/j.molstruc.2016.06.084

A calcium complex of N-phthaloylglycine (CaNPG) has been synthesized, and its crystal structure has been characterized by X-ray diffraction method. The FT-IR and fluorescence spectra for CaNPG have been recorded. N-phthaloylglycine ligand coordinates to Ca ion through the carboxylate O atoms as a bidentate ligand, and Ca ion does not play an important role in florescence spectrum. In order to support experimental findings and also investigate molecular surfaces, natural bond orbital (NBO) and nonlinear optical (NLO) optical properties of CaNPG complex, density functional theory calculations have been performed by hybrid B3LYP level. The very small energy gap between α-spin frontier molecular orbitals (FMOs) is demonstrated that CaNPG is a very reactive, chemically soft and optically active complex. The high stabilization energies of hyperconjugative interactions are also demonstrate that the charge mobility in CaNPG is very high. As consistent with above findings, first static hyperpolarizability of CaNPG has been found to be 10 times higher than pNA which is a NLO material.

Full text of DOI:10.1016/j.molstruc.2016.06.084

Accepted Manuscript
Structural, spectroscopic, nonlinear optical and electronic properties of calcium N-
phthaloylglycinate: A combined experimental and theoretical study
Ömer Tamer, Moazzam H. Bhatti, Uzma Yunus, Davut Avcı, Yusuf Atalay,
Muhammad Nadeem, Syed Raza Shah, Madeleine Helliwell
PII:
S0022-2860(16)30671-8
10.1016/j.molstruc.2016.06.084
MOLSTR 22703
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 16 March 2016
Revised Date: 29 June 2016
Accepted Date: 29 June 2016
Please cite this article as: E. Tamer, M.H. Bhatti, U. Yunus, D. Avcı, Y. Atalay, M. Nadeem, S.R.
Shah, M. Helliwell, Structural, spectroscopic, nonlinear optical and electronic properties of calcium
N-phthaloylglycinate: A combined experimental and theoretical study, Journal of Molecular Structure
(2016), doi: 10.1016/j.molstruc.2016.06.084.
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ACCEPTED MANUSCRIPT

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Structural, spectroscopic, nonlinear optical and electronic properties of
Calcium N-phthaloylglycinate: A combined experimental and
theoretical study
Ömer Tamer a,*, Moazzam H. Bhatti b,*, Uzma Yunus b, Davut Avcı a, Yusuf Atalay
a, Muhammad Nadeem b, Syed Raza Shah b, Madeleine Helliwell c
a Sakarya University, Arts and Sciences Faculty, Department of Physics, 54187, Sakarya, Turkey
b Department of Chemistry, Allama Iqbal Open University, Islamabad, Pakistan,
c School of Chemistry, University of Manchester, Manchester M30 9PL, England
Abstract
A calcium complex of N-phthaloylglycine (CaNPG) has been synthesized, and its crystal
structure has been characterized by X-ray diffraction method. The FT-IR and
fluorescence spectra for CaNPG have been recorded. N-phthaloylglycine ligand
coordinates to Ca ion through the carboxylate O atoms as a bidentate ligand, and Ca ion
does not play an important role in florescence spectrum. In order to support experimental
findings and also investigate molecular surfaces, natural bond orbital (NBO) and
nonlinear optical (NLO) optical properties of CaNPG complex, density functional theory
calculations have been performed by hybrid B3LYP level. The very small energy gap
between α-spin frontier molecular orbitals (FMOs) is demonstrated that CaNPG is a very
reactive, chemically soft and optically active complex. The high stabilization energies of
hyperconjugative interactions are also demonstrate that the charge mobility in CaNPG is
very high. As consistent with above findings, first static hyperpolarizability of CaNPG
has been found to be 10 times higher than pNA which is a NLO material.
Keywords: Calcium N-phthaloylglycinate, Nonlinear Optic, Fluorescence, Density Functional
Theory, Natural Bond Orbital
*Corresponding authors.
E-mail addresses: omertamer@sakarya.edu.tr (Ö. Tamer), moazzamhussain_b@yahoo.com (M. H. Bhatti).

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1. Introduction
Phthalimides and its derivatives are one of the important class of organic molecules that
possess diverse structural and biological applications [1,2]. Among phthalimides
derivatives, N-Phthaloylamino acids are used for the synthesis of peptide bonds in solid
phase synthesis [3]. Such phthalimide derivatives undergo photochemical reactions such
as photochemical decomposition and decarboxylation [4]. Among the N-phthaloylamino
acids, N-phthaloylglycine has been most widely studied with reference to cleavage with
various amines, metal complexes with interesting supramolecular structures and adducts
formations with various aromatics amines and hydroxyl aromatic compounds [5-7]. The
heterocyclic derivatives of N-Phthaloylglycine are also reported in literature such as
oxadiazole [8] and benzoxazinone [9]. Previously, we have reported the synthesis,
characterization and crystal structure of 12,4-triazole of N-phthaloylglycine and its Schiff
and Mannich bases [10, 11]. In addition, we have also reported the synthesis and DNA
binding studies of Ni(II), Cu(II) and Zn(II) complexes of N-Phthaloylglycine [12].
Metal organic frameworks (MOFs) offer an opportunity for combining the characteristics
of both organic and inorganic ligands in order to obtain better nonlinear optical materials
for the possible applications in telecommunication, high optical disk data storage, optical
information processing and optical computing. Combining the high optical nonlinearity
and chemical flexibility properties of organic ligands with thermal stability and perfect
transmittance of inorganic materials have been attracted a great deal of attention in the
field of nonlinear optics [13-15]. Additionally, the syntheses and characterizations of new
materials with higher nonlinearities have gathered great interest in these days in order to
satisfy the increasing technological requirements. One of the ways in which an organic
molecule shows a large optical nonlinearity is that the extension of aromatic rings
increasing the number of π electrons as well as their delocalization length [16-17].
Additionally, the substitution of aromatic rings with electron donor and acceptor atom
and/or atom groups has let to remarkable increase in the first order hyperpolarizability
(β).

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It is well known that phthalimide is an aromatic cyclic compound and has strong π-bond
delocalization. Additionally, two carbonyl (C=O) which is known as a powerful electron
withdrawing group have been located on opposite sides of the molecule. Therefore,
phthalimide derivates seems to be appropriate for nonlinear optical applications. It is also
known that the coordination to metal atom enhances the nonlinear optical properties of
organic molecules [18-20]. Considering that above mentioned conditions, the nonlinear
optical properties of CaNPG complex have been investigated by density functional theory
(DFT) calculations.
2. Experimental procedures
2.1. Synthesis of CaNPG complex
N-phthaloylglycine was prepared by the reported method [21]. The title compound was
prepared by treating the N-phthaloylglycine (7.5 mmol, 1.54 g) with calcium oxide (3.75
mmol, 0.21g). The reactants were placed in a beaker with 100 ml of distilled water and
stirred for about 2 hours. The reaction was carried out with the ratio of 2:1 of N-
phthaloylglycine and calcium oxide, respectively (Figure 1). The resulting solution was
filtered and cooled at room temperature. After a few days colorless crystals were formed
(Yield: 73 %), which were washed with distilled water and characterized further.
2.2. Materials and instrumentation
All chemicals used in this work were analytical grade and purchased from Aldrich or
Merck. Melting points were determined on Gallen Kamp, an electro thermal apparatus,
Cat No.MPD350, sanyo, UK and is uncorrected. Infrared spectra were recorded on
Nicolet iS 10 FTIR Spectrophotometer (4000-400 cm-1) in KBr discs. Thermal
gravimetry (TG) was measured DTG-60H Simultaneous DTA-TG Analyzer utilizing a
heating rate of 10°C/min. Fluorescent Emission spectra (DMSO) were recorded on F-
7000 FL Spectrophotometer.

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2.3. Crystal Data
The crystals of title compound were grown by slow evaporation of water at room
temperature. The colorless plate crystals were mounted on a sealed tube and all X-ray
crystallographic data were collected on a Bruker AXS Smart Apex diffractometer.
Correction for semi-empirical from equivalents was applied, and the structure was solved
by direct methods and refined by a full-matrix least squares procedure based on F2 using
the SHELXL-97 Program System [22-25]. All data were collected with graphite-
monochromated MoKα radiation (λ = 0.71073 Å) at 100K.
3. Computational procedure
All of the calculations carried out in this study have been performed by using Gaussian
09 Revisions D.01 program [26] and the obtained theoretical data visualized by means of
GaussView 5 [27]. First of all, [Ca(Gly)2(H2O)2] complex has been optimized in ground
state energy level by using B3LYP level [28,29] of density functional theory (DFT) and
6-311++G(d,p) basis set [30]. Based on the obtained geometry, the vibrational
frequencies for CaNPG complex have been computed by using the same method and
basis set. It is well known that DFT levels predict vibration frequencies larger than
experimental corresponding, so the obtained vibration frequencies were scaled down with
the scaling factor of 0.9614 [31]. The electronic absorption spectrum for CaNPG in gas
phase and ethanol solvent were simulated by using time dependent DFT (TD-DFT) level
[32]. Solvent models allow simulations and calculations of reactions and processes which
take place in solvated phases. For this purpose, conductor-like polarizable continuum
model (CPCM) [33] has been used to calculate solvent (ethanol) effect. NBO analysis
[34] has been performed to investigate the intermolecular charge transfer, rehybridization
and delocalization of electron density. The nonlinear optical properties of CaNPG has
been also investigated by the determining of dipole moment (ꢀ), polarizability (α),
anisotropy of polarizability (∆α) and first hyperpolarizability (β). Finally, Molecular
Electrostatic Potential surface (MEP) [35] has been simulated to demonstrate
polarizability, intramolecular charge transfers and reactive sides of CaNPG.

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4. Result and Discussion
4.1. Structural analysis
A calcium complex of N-phthaloylglycine was prepared and its crystal structure which
reported by Bhatti et al. [36]. In CaNPG complex, the calcium atom was located to the
center of distorted octahedron. In this study, CaNPG complex has been optimized in
ground state energy, and the obtained geometric data have been compared with
experimental ones. The XRD and optimized geometries are presented in Figure 2, and the
obtained bond lengths and bond angles are tabulated in Table 1. C3-O3 and C10-O4 bond
lengths observed at 1.220(2) and 1.210(3) Å have been calculated as 1.209 and 1.208 Å,
respectively. These bond lengths were reported as 1.207 Å [37], 1.201 and 1.207 Å [38]
as consistent with our results. The phthalimide ring C-C bond lengths were observed at
the range of 1.528(3)-1.381(3) Å and calculated at the region of 1.527-1.385 Å. In order
to find the consistency between experimental and theoretical results, we have calculated
the root mean square error (R2) for bond lengths and angles. The R2 values have been
found to be 0.99201 for bond lengths and 0.99128 for bond angles. Considering that the
above R2 values, it can be said that there is a perfect agreement between the results
obtained from XRD and B3LYP methods.
4.2. Infrared spectra
The FT-IR spectrum for N-phthaloylglycine and CaNPG has been recorded in the range
of 4000-400 cm-1. In order to compare FT-IR spectrum, vibrational frequencies have been
also calculated by using B3LYP level and 6-311++G(d,p) basis set. The FT-IR and
theoretical vibration spectra for N-phthaloylglycine and [Ca(Gly)2(H2O)2] are presented
in Figure 3, as compared with each other. The obtained vibration frequencies are also
given in Table 2. The very broad peaks at 3568 cm-1 due to stretching frequency ʋ (OH)
of acid appeared in the spectrum of free N-phthaloylglycine was disappeared in the
spectrum of CaNPG confirmed that, the hydrogen ion of carboxylate group of free N-
phthaloylglycine was substituted by the calcium atom. The presence of broad band at

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3475 cm-1 for CaNPG prove the presence of coordinated water molecules with calcium
[14,15]. B3LYP level calculations demonstrate that this vibration band stems from the
asymmetric H2O stretching vibrations, and has been found at 3556 cm-1. The symmetric
vibration of coordinated H2O ligand has been calculated at 3413 cm-1. The characteristic
stretching vibrations of cyclic carbonyl appeared at 1761 and 1717 cm-1 [39,40]. These
stretching vibrations have been calculated at 1755 and 1703 cm-1, respectively. As readily
seen from Figure 3, the stretching frequency ʋ (CO) of carboxylic group is lowered from
the value found for in free N-phthaloylglycine due to resonance effect [41,42]. The
characteristic asymmetric and symmetric stretching vibrations due to the carboxylate
group appear at 1471 cm-1 and 1396 cm-1 for CaNPG. These vibrations have been found
to be 1511 and 1403 cm-1, respectively. The frequency gap between asymmetric and
symmetric stretching of carboxylate group gives powerful evidences about the
coordination type of the group [43-45]. The frequency gaps found to be 75 cm-1 in FT-IR
and 108 cm-1 in B3LYP level prove carboxylate group coordinates to Ca atom as a
bidentate ligand. The phthalimide C-C ring stretching vibrations observed at the range of
1695-1176 cm-1 in FT-IR have been calculated at the range of 1583-1167 cm-1 by using
B3LYP level. The other vibration bands for [Ca(Gly)2(H2O)2], presented in Table 2, have
been observed and calculated as consistent with previously reported studies [46,47].
4.3. Electronic Properties
The CaNPG complex has two strong fluorescence emissions (blue emission maxima) at
412 and 437 nm upon excitation at 376 nm with greater intensity comparative to their
ligand fluorescence emission i.e N- phthaloylglycine. Fluorescence emissions spectra
depicted in Figure 4 and data is presented in Table 3. Due to the resemblance in the
shapes and positions of fluorescence emission and excitation pattern of complex and
ligand it can be decided that the emissions observed for the complex is neither MLCT
(metal-to-ligand charge transfer) nor LMCT (ligand-to-metal charge transfer) in nature,
and can be assumed as the intra-ligand fluorescent emission. The emission observed in
the compounds assigned to the (π→π* and n→π*) intra-ligand fluorescence. The slight

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difference in the positions of luminescent peaks in the compounds may be due to the
different coordination modes of the ligand.
The conjugated organic molecular systems are generally described by a small energy gap
between the highest occupied molecular orbital (HOMO) and lowest unoccupied
molecular orbital (LUMO), which leads to a significant degree of intra-molecular charge
transfer (ICT) in the system. That is, the charge transfer interaction is simply considered
as transfer of an electron from HOMO of the donor to the LUMO of the acceptor or
transfer of proton from acceptor to donor [48,49]. Additionally, molecular orbitals, their
energies and energy gaps are also used to explain several types of reactions and predict
the most reactive position of conjugated systems [50,51]. Since the Ca atom has doublet
spin, both α- and β-spin molecular orbitals have been considered in B3LYP level
calculations. Both of α- and β-spin frontier molecular orbitals and their energies are
presented in Figure 5. Due to the very small energy gap between HOMO and LUMO, it is
thought that α-spin MOs are more active in electronic transitions than β-spin ones. The
HOMO and LUMO energies have been calculated as -3.3122 and -2.4945 eV,
respectively. The HOMO-LUMO energy gap has been found to be 0.8177 eV. The
energy gap between HOMO and LUMO is commonly used to determine the optical
polarizability, chemical reactivity (ꢀ), kinetic stability, electronegativity (χ) chemical
hardness (η) and softness (s) of a molecule [52]. The ꢀ, χ, η and s parameters have been
calculated as -2.90335, 2.90335, 0.40885 and 2.44588 eV, respectively. From these
obtained values, it is readily said that CaNPG complex characterized as a very soft
system has high charge mobility and its molecular stability is quite low.
4.4. Molecular surfaces
The molecular electrostatic potential (MEP) is related to the total charge distribution of
the investigated molecule and commonly used as a descriptor in understanding sites for
electrophilic and nucleophilic attacks and also hydrogen bonding interactions [53,54]. It
is also useful in understanding the relationships of the molecular structure with its
physiochemical properties [55]. The negative potential regions represented by red color

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are associated with electrophilic reactivity and the positive potential regions represented
by blue color to nucleophilic reactivity as shown in Figure 6. From Figure 6, the negative
electrostatic potential regions are mainly localized over the carbonyl groups (C=O) and
carboxylic group (COO-) indicating a possible site for electrophilic attack. As for the
positive electrostatic potential region, it is located around the H atoms of aqua ligand
indicating a possible site for nucleophilic attack. In the spin density distribution of
CaNPG complex, phthalimide ring carry positive spin density and the spin density is
propagated through the bonds of the ligand as well as C and O atoms whereas Ca atom,
COO- group and aqua ligand have no spin delocalization.
4.5. Natural Bond Orbital analysis
NBO analysis has been used as a powerful method for investigating of the intra- and
inter-molecular hydrogen bonding and interaction among bonding and antibonding
orbitals of molecular systems [56]. It is also used to investigate orbitals population,
orbital energy, hybridization, hyperconjugative interaction, intramolecular charge transfer
interaction and electron density exchange from the occupied lone pair electron within the
molecule. Delocalization of electron density between occupied Lewis-type (bond or lone
pair) NBO orbitals and formally unoccupied (antibond or Rydberg) non-Lewis NBO
orbitals corresponds to a stabilizing donor–acceptor interaction [57]. Some selected
interactions which result in stabilization energies exceeding an arbitrary chosen threshold
are tabulated in Table 4.
According to the NBO analysis, the electronic configuration of Ca ion in CaNPG is
[core]4s(0.75)3d(0.10)4p(0.20). The total electron (19.06042 e) of Ca ion are distributed as
17.99558 core electrons, 1.05439 valence electrons and 0.93958 Rydberg electrons. From
NBO analysis, the natural charge for Ca ion is found to be 0.93958 e. The obtained
natural charge is small than the expected charge (+2) is demonstrate that the charge
transfers from ligands to Ca ion is slightly higher than the reverse ones.

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The larger the E(2) value, the more intense is the interaction between electron donors and
acceptors, i.e. a more donating tendency from electron donors to electron acceptors and a
greater extent of conjugation of the whole system with delocalization of the electron
density between occupied Lewis-type and unoccupied non-Lewis NBO orbitals [58]. The
intramolecular hyperconjugative interactions of π (C4-C9) → π* (C3-O3), LP (1) N1 →
π* (C3-O3) and LP (3) O1 → LP (1) C1 have been calculated with the high stabilization
energies of 10.27, 24.13 and 87.49 kcal/mol, respectively. Compared to ligand-metal
charge transfer (LMCT) and metal-ligand charge transfer (MLCT), ligand-ligand charge
transfer (LLCT) interactions are strongly dominant in CaNPG complex. Additionally, the
most significant interaction observed between lone pair electron orbitals of Ca ion is LP
(1) Ca →LP (2) Ca and has 0.38 kcal/mol interaction energy. Hence, it is demonstrated
that this kind of interaction in CaNPG is found to be negligible level.
4.6. NLO studies
The search for new molecular systems possessing a large value of static first
hyperpolarizability is an important stage for the optimization of new materials which are
found applications in a wide spectrum from optical telecommunications, data storage,
signal processing, logic technologies and sensor protection to modern optical computing
[59]. The computational methods offer a change for the determination of molecular NLO
properties by an inexpensive way to design molecules by analyzing their potential
without synthesis and to calculate high order hyperpolarizability tensors of molecules.
The dipole moment (ꢀ), mean polarizability (α), anisotropy of polarizability (ꢁα) and first
static hyperpolarizability (β) for CaNPG complex have been calculated by using B3LYP
functional which is successfully predicting a wide range of molecular properties.
It is well known that the molecule will have strong second order NLO response is
proportionally increase more delocalized π electrons, bigger change of dipole moment
from ground state to excited state, large transition moment and non-centrosymmetry
structure [60]. Additionally, the larger NLO properties of any molecular systems are
generally characterized by a small HOMO-LUMO energy gap, high second order

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perturbation interaction energies and high dipole moment indicating the high charge
mobility in the system. In Table 5, the ꢀ, α and β parameters have been presented to be
4.2221 Debye, 45.759x10-24 esu and 157.675x10-24, respectively. Particularly, the first
hyperpolarizability is found to be approximately 10 times higher than p-NitroAniline
(pNA) used as
a
prototypical NLO material [61,62]. The obtained first
hyperpolarizability value for CaNPG complex is found to be very high, compared to
previously reported theoretical results for different metal complexes [63,64].
4.7. Thermal Analysis
Thermal decomposition patterns (TG and DTA) of complex shown in Figure 7 and
thermo analytical data are summarized in Table 6. The thermogram of the title compound
indicates four steps decomposition. In the first step two coordinated water molecules are
lost between 150-220°C. The corresponding peak in DTA is observed as an endotherm at
200.59 °C. The second, third and fourth stages in the range of temperature 220-750°C
showing the decomposition of complex. These three stages are in connection with a
weight loss of 81.04% and the calculated weight loss value in these three stages is
80.99%. The total observed weight loss value is 89.24 % with a residue equal 10.76 %
which is corresponding to calcium oxide.
5. Conclusions
The synthesis of a calcium complex of N-phthaloylglycine has been reported. The
structural characterization of CaNPG complex has been performed by the applying of X-
ray diffraction method and density functional theory calculations. The infrared spectra
obtained by FT-IR and B3LYP level of DFT have been used to explain the coordination
environment of Ca ion and the effects of vibration modes on the electric and electronic
properties of CaNPG. The frequency gaps between the symmetric and asymmetric COO-
stretching vibrations have been found to be 75 cm-1 in FT-IR and 108 cm-1 in B3LYP
level, and prove carboxylate group coordinates to Ca atom as a bidentate ligand. The
disappearance of very broad peaks at 3568 cm-1 due to stretching frequency ʋ (OH) of

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acid appeared in the spectrum of free N-phthaloylglycine has been confirmed that the
hydrogen ion of carboxylate group was substituted by the calcium atom. The α- and β-
spin frontier molecular orbitals have been visualized by using B3LYP level. In
particularly, the energy gap between α-spin FMOs is found to be very low. This small
energy gap indicates that CaNPG is an optically soft complex and can be easily polarized
with even a small energy. The resemblance of fluorescence spectra for NPG ligand and
CaNPG complex demonstrate that all of the excitation and emission band stem from the
ligand-ligand electronic transitions. This case is also proved by NBO analysis. The
interaction energies of ligand-metal and metal-ligand orbitals are found to be very small,
whereas those of ligand-ligand orbitals are found to be very high. Summing up, the very
active vibration peak such as C=O, C=N and C=C in vibration spectra, very small energy
gap between HOMO and LUMO, vey high second order interaction energies in NBO
analysis are separately indicators of very high first static hyperpolarizability values. As
would be expected, CaNPG is an optically very active complex. The β parameter for
CaNPG is found approximately 10 times higher than pNA which is a prototypical
nonlinear optical material, hence CaNPG is a perfect candidate to nonlinear optical
materials.

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Table 1. Experimental and theoretical bond lengths (Å) and bond angles (°) for CaNPG
Bond lengths X-Ray
B3LYP
2.3173
2.3221
1.2679
1.2650
1.209
1.208
1.402
1.404
1.442
1.527
1.492
1.385
1.394
1.399
1.399
1.398
1.385
1.492
0.99201
Bond angles
C3-N1-C10
C3-N1-C2
C10-N1-C2
O2-C1-O1
O2-C1-C2
O1-C1-C2
O3-C3-N1
O3-C3-C4
N1-C3-C4
C5-C4-C9
C5-C4-C3
C9-C4-C3
C4-C5-C6
C5-C6-C7
C8-C7-C6
C9-C8-C7
C8-C9-C4
C8-C9-C10
C4-C9-C10
O4-C10-N1
O4-C10-C9
N1-C10-C9
R2
X-Ray
B3LYP
112.318
123.430
123.746
122.312
120.315
117.373
125.151
129.283
105.563
121.501
130.219
108.280
117.440
121.055
121.058
117.430
121.515
130.176
108.308
125.238
129.269
105.489
0.99128
Ca1-O1
Ca1-O2
O1-C1
O2-C1
O3-C3
O4-C10
N1-C3
N1-C10
N1-C2
C1-C2
C3-C4
C4-C5
C4-C9
C5-C6
C6-C7
C7-C8
C8-C9
C9-C10
R2
2.3222(16)
112.22(18)
122.49(17)
125.18(19)
123.62(19)
120.12(19)
116.26(18)
124.0(2)
2.5569(15)
1.256(3)
1.243(3)
1.220(2)
1.210(3)
1.386(3)
1.402(3)
1.445(3)
1.528(3)
1.483(3)
1.382(3)
1.394(3)
1.399(3)
1.400(3)
1.388(3)
1.381(3)
1.489(3)
129.7(2)
106.35(17)
121.97(19)
130.23(19)
107.77(19)
117.2(2)
120.6(2)
121.5(2)
117.7(2)
121.0(2)
130.7(2)
108.30(18)
124.8(2)
129.9(2)
105.34(18)
Bond angles
O1-Ca1-O2
C1-O1-Ca1
50.91(5)
89.41(6)
57.139
90.326

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Table 2. The FT-IR and calculated IR vibration frequencies and intensity
Assigments
FT-IR
λ (cm-1)
3568
3475
3096
3041
2940
1761
1717
1695
1607
1471
1428
1396
-
1310
1286
-
1176
1120
1087
-
B3LYP/6-311++G(d,p)
λ (cm-1)
3556
3413
3076
3062
2960
1755
1703
-
IIR
ν OH
ν OH
ν CH (ring)
ν CH (ring)
ν CH2
ν C=O
ν C=O
ν CC (ring)
ν CC (ring)
νas CO2
β CH
νs CO2
ν CN
ν CC (ring)
β CH2
β CH (ring)
ν CC (ring) + β CH (ring)
β CH (ring)
ν CN
β CC (ring)
R.b.
γ CH (ring)
γ CH2
β CC
128.344
1348.051
9.633
6.478
12.920
86.475
579.229
-
1583
1511
1438
1403
1349
1330
1285
1258
1167
1134
1091
1056
965
16.646
200.807
5.94
213.426
434.048
18.94
69.604
0.214
27.600
6.244
38.994
12.497
13.097
0.994
969
929
-
942
933
831
63.657
1.955
855
γ CH (ring)
γ CH (ring)
τ CC (ring)
γ CC (ring)
γ CH2
748
714
667
634
775
723
684
651
1.755
103.665
0.580
0.016
19.48
545
544
τ CC (ring)
525
515
9.854
ν: stretching, β: in plane bending, γ: out of plane bending, δ:scisso (ring), τ: torsion, r: (ring), R.b.: ring
breathing

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Table 3. Electronic absorption and emission data of NPG and CaNPG complex
Compounds
NPG
EX(nm)
364
EM(nm)
Stoke Shift(nm)
417
438
412
437
53
74
36
61
CaNPG
376

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Table 4. Second order perturbation theory analysis of the Fock matrix in NBO basis for CaNPG
Type
σ
σ
σ
σ
π
π
π
π
LP (1)
LP (1)
LP (3)
LP (3)
LP (1)
LP (1)
LP (1)
LP (1)
LP (2)
Donor
C4-C9
C4-C9
C4-C9
C4-C9
C4-C9
C4-C9
C4-C9
C4-C9
N1
N1
O1
O2
O1
O2
Ca
Ca
O5
Type
σ
σ
σ
σ
π
π
π
Acceptor
C4-C5
C9-C6
C3-C4
C9-C10
C6-C7
C5-C6
C3-O3
C10-O4
C3-O3
C10-O4
C1
C1
Ca
Ca
C1-C2
Ca
E(2) (kcal/mol)
2.24
2.24
0.44
0.45
9.72
9.71
10.27
10.32
24.13
24.42
87.49
88.19
3.40
3.20
0.04
0.38
4.86
π
π
π
LP (1)
LP (1)
LP (2)
LP (2)
σ
LP (2)
LP (4)
Ca

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Table 5. Total static dipol moment (ꢀ, in Debye), the mean polarizability (<α>, in 10-24 esu), the anisotropy of the
polarizability (ꢁα, in 10-24 esu), the mean first-order hyperpolarizability (<β>, in 10-30 esu) for CaNPG
Property
B3LYP/6-311++G(d,p)
ꢀ
4.2221
2.44
ꢀa
α
αb
45.759
22
ꢁα
β
β c
9.763
157.675
15.5
a, b and c Taken from Reference [54,55]

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Table 6: TG-DTA data of complexes
Thermogravimetry
Weight loss (%)
DTA Peak
Temp.(oC)
Decomposition product
H2O
Compound
CaNPG
Number of stages
Temp. range
Found
Calc.
7.65
(oC)
200.59(+)
397.05(-)
532.56(+)
592.56(-)
150-220
220-440
440-565
565-750
8.2
30.24
14.03
36.77
4
81.04
80.99
CaNPG

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Figure 1. Synthesis and characterization of NPG and CaNPG complex.

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Figure 2. a) Experimental b) optimized geometric structures for CaNPG complex

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Figure 3. FT-IR and calculated IR spectra for NPG and CaNPG complex.

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Figure 3. Fluorescence spectrum of NPG and CaNPG in 1.0×10-3 M in DMSO solution at 25.0 ± 0.1 ºC

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Figure 5. The α- and β-spin frontier molecular orbitals and their energies

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Figure 6. The molecular electrostatic potential (MEP) and spin density distribution maps of CaNPG
complex

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Figure 7: TG-DTA curves of CaNPG