Experimental and theoretical investigations of non-centrosymmetric 8-hydroxyquinolinium dibenzoyl-(l )-tartrate methanol monohydrate single crystal

Accepted Manuscript Title: Experimental and theoretical investigations of non-centrosymmetric 8-hydroxyquinolinium dibenzoyl-(L)-tartrate methanol monohydrate single crystal Author: N. Sudharsana V. Krishnakumar R. Nagalakshmi PII: DOI: Reference:

S0025-5408(14)00570-4 http://dx.doi.org/doi:10.1016/j.materresbull.2014.09.068 MRB 7709

To appear in:

MRB

Received date: Revised date: Accepted date:

5-12-2013 18-3-2014 21-9-2014

Please cite this article as: N.Sudharsana, V.Krishnakumar, R.Nagalakshmi, Experimental and theoretical investigations of non-centrosymmetric 8hydroxyquinolinium dibenzoyl-(L)-tartrate methanol monohydrate single crystal, Materials Research Bulletin http://dx.doi.org/10.1016/j.materresbull.2014.09.068 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Experimental and theoretical investigations of non-centrosymmetric 8hydroxyquinolinium dibenzoyl-(L)-tartrate methanol monohydrate single crystal N.Sudharsana1, V.Krishnakumar2, R.Nagalakshmi1,* 1

Department of Physics, National Institute of Technology, Tiruchirappalli 620015, India 2

Department of Physics, Periyar University, Salem - 636011, India.

Graphical abstract ORTEP diagram of HQDBT.

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Highlights

Single crystal XRD and NMR studies confirm the formation of the title compound.

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SHG efficiency was found to be 0.6 times that of KDP.

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First-order hyperpolarizability (β) was calculated using HF and B3LYP methods.

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Abstract: A novel 8-hydroxyquinolinium dibenzoyl-(L)-tartrate methanol monohydrate crystal have

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been grown by slow evaporation technique. The single crystal X-ray diffraction analysis has been

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done for the title compound and is found to crystallize in orthorhombic space group P212121. The

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optical absorption cut-off wavelength is found to be 440nm. The vibrational analysis have been

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carried out to assess the functional groups present in the title compound. The molecular structure of

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the title compound has been confirmed by nuclear magnetic resonance spectroscopy. Thermogravimetric, differential scanning calorimetric and differential thermal analyses reveal the

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melting point and thermal stability of the title compound. The second harmonic generation efficiency

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is confirmed by Kurtz-Perry powder technique. Further quantum chemical calculations are performed using Gaussian 03 software.

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*Corresponding author: E-mail:[email protected], Phone No: +91431-2503615, Fax:+91-4312500133. Keywords: A. organic compounds, B. crystal Growth, B. optical properties, C. nuclear magnetic resonance (NMR), D. crystal structure

1. Introduction: Materials possessing large second order nonlinear susceptibility are intensively studied for frequency conversion, especially for the second harmonic generation (SHG) in the blue and near ultraviolet region of the spectrum, for applications in spectroscopy and information processing, and in the infrared region, for the realization of devices designed for optical communications [1]. Organic compounds are often formed by weak van der Waal and hydrogen bonds and possess a high degree of delocalization. Hence, they are optically more nonlinear than inorganic materials. Dibenzoyl-L-

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tartaric acid (DBTA) is used as a chiral building blocks, chiral resolution reagents in active pharma

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ingredients, and asymmetric synthesis. Although the carboxylic acid groups of DBTA can donate

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protons for hydrogen bonding, it can also behave as a proton acceptor due to the presence of eight oxygen atoms in the structure. The benzoyl groups can take part in hydrophobic interactions while the

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other part of the molecule contains polar hydrophilic groups [2]. The investigation of organic tartrates

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seems to be fruitful as it is having the ability to coordinate with some organic bases because of its

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chiral structure and noncentrosymmetricity [3]. The multidirectional hydrogen bonded tartrate anions

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provide a conformational rigid environment for the incorporation of cations to form acentric

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crystalline salts, i.e. second harmonic generation materials [4]. The tartaric acid forms a broad family

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of hydrogen-bonded crystals. Several tartrate compounds deserve special attention because of their many interesting physical properties such as dielectric, piezoelectric, ferroelectric and optical second

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harmonic generation. These characteristics of tartrate compounds are exploited for their use in

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transducer and in several linear and non-linear mechanical devices [5, 6]. Quinolines are interesting molecules which have enhanced non centrosymmetry (essential property to exhibit NLO activity) due

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to their lack of rotational symmetry. In the molecular design of new nonlinear optical materials based on quinoline, the pyridine ring can function as an acceptor group and the benzene ring as the donor. The optical nonlinearities of this class of compounds can be improved by increasing the acceptor character of the pyridine ring and/or increasing the donor character of the benzene ring [7]. The 8Hydroxyquinolines (8HOQs) known as oxine has drawn significant attention due to good nonlinear optical property. 8HOQ has been found to be non-carcinogenic and is employed for in vitro assays as

well as genetic toxicity [8]. Their ability to accept proton when added with acids is an essential component for nonlinear optical application. 8HOQ and its derivatives are well known for their antifungal, antibacterial and antiamoebic activities [9]. Amongst the bifunctional molecules, HOQs have been extensively studied from both experimental and theoretical view point. The 8HOQ molecule is planar and belongs to point group Cs [10]. During our continuous search for novel organic asymmetric crystals based on crystal engineering of acid-base complex, we have ended up with the synthesis of the present compound 8hydroxyquinolinium dibenzoyl-(L)-tartrate methanol monohydrate (HOQDBT) which is a charge

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transfer complex. We have synthesized and carried out systematic physical and chemical properties

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for the title compound and reported for the first of its kind. In addition, calculation of first-order

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hyperpolarizability, molecular orbitals and electrostatic potential were performed using Gaussian 03

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software employing to witness its charge distribution and nonlinear optical activity as well.

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2. Experimental Section:

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2.1. Synthesis and crystal growth:

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The title compound 8-hydroxyquinolinium dibenzoyl-(L)-tartrate methanol monohydrate

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was synthesised by reacting equimolar quantities of 8-hydroxyquinoline and dibenzoyl-(L)-tartaric

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acid in methanol solvent at room temperature. The yellow precipitate obtained was purified by repeated recrystallization. The pH value of the solution was found to be 5.51. The transparent light

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green colour crystals of size 10×2×2mm3 were harvested after five days of evaporation at room

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temperature from saturated solution. The photograph of as-grown crystals is shown in Fig.1a.

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2.2. Solubility:

The solubility in methanol was measured as a function of temperature in the range 30-60ᴼC.

The solubility of the compound is moderate in water and yielded needle crystals. Methanol is considered to be the suitable solvent for the growth of the title compound as it yields good crystals. The solubility was measured by adding excess amount of synthesized salt in the solvent at constant temperature (30ᴼC). On attaining the saturation, the equilibrium concentration of the solute was

analysed gravimetrically. The solution was stirred constantly using magnetic stirrer until it becomes fully soluble. The solution was poured into the petridish. The solvent was completely evaporated by drying the solution. The amount of the salt present in the solution was measured by subtracting the empty petridish weight. Following the same procedure, the amount of 8-hydroxyquinoliniumdibenzoyl-(L)-tartrate methanol monohydrate (HOQDBT) salt dissolved in methanol at 40C, 50C and 60C were determined. The solubility curve for HOQDBT is shown in Fig 1b. The solubility almost increases linearly with temperature and the title compound exhibits positive temperature

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coefficient of solubility in methanol.

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2.3. Computational details:

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All the quantum chemical calculations were performed at density functional theory level with the Gaussian 03 program [11]. Atomic positions are taken from the crystallographic information file

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(CIF) for geometry optimization. The optimization was done using Becke, 3-parameter, Lee-Yang-

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Parr exchange-correlation functional (B3LYP) and Hartree-Fock (HF) method employing 6-31G (d,p)

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basis set. An optimization is complete when it has converged i.e., when it has reached a minimum on

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the potential energy surface, thereby predicting the equilibrium structure of the molecule. This

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criterion is very important in geometry optimization [12]. The optimized structure has been further

potential surface.

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used for calculations such as first-order hyperpolarizability (β), molecular orbitals and electrostatic

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The dipole moment (μ), polarizability (α), and the total first-order hyperpolarizability (βtot) in

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terms of x, y, z components are given by the following equations, (1)

α=1/3(αxx+αyy+αzz)

(2)

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μ=(μx2+μy2+μz2)1/2

βtot = (βx2+βy2+βz2)1/2 βtot=[(βxxx+βxyy+βxzz)2+(βyyy+βyzz+βyxx)2+(βzzz+βzxx+βzyy)2]1/2

(3)

The β components are converted to e.s.u. units from Gaussian output file (1 a.u. = 8.3693  10-33 e.s.u), for α components (1a.u. = 0.148210-24 e.s.u.), for HOMO (highest occupied molecular orbital)

and LUMO (Lowest unoccupied molecular orbital) (1 a.u. = 27.2176 eV). The optimized geometric parameters, molecular orbitals and electrostatic potential are viewed using the Gauss-View molecular visualization program [13].

3. Results and Discussion: 3.1. Single crystal X-ray diffraction: The single crystal X-ray diffraction (XRD) measurement was carried out on an Enraf (Bruker) nonius CAD4 diffractometer. The HOQDBT structure was refined by the full-matrix least-squares

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method. The HOQDBT crystal data and structure refinement are summarised in Table.1. The

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HOQDBT crystal belongs to orthorhombic system with unit cell dimensions: a=7.7175(2)Å,

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b=16.7313(7)Å, c=21.1458(5)Å, α=β=γ=90ᴼ, V=2730.43(15) Å3 and crystallizes in noncentrosymmetric space group P212121.

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The asymmetric unit (Fig.2a) contains one monoionized dibenzoyl-(L)-tartaric acid, one

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protonated 8-hydroxyquinoline, one methanol and one water molecule. The O11 atom of methanol

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solvent molecule is bonded to O10 atom of water molecule by intermolecular interactions.

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Interestingly, the water (O10) and methanol (O11) solvent molecules are involved in hydrogen

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bonding. The carboxylic acid group (-COOH) in DBTA molecule transfers its proton to the N atom

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(8-HOQH+) of 8HOQ molecule to form the charge transfer complex. The 8-hydroxyquinoline and dibenzoyl tartaric acid are linked by strong hydrogen bonding. The methanol, water, 8HOQ and

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DBTA molecules lead to several intra- and intermolecular hydrogen bond interactions. The water molecule acts as a hydrogen bond donor to the oxygen atom of ionized carboxylate

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group (COO-) and ester group (-COO) of dibenzoyl-(L)-tartrate anion by the type O10-H10B…O3

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and O10-H10A…O6, respectively. The water molecule acts as a hydrogen bond acceptor with C-H group next to the nitrogen atom of 8-hydroxyquinolinium cation and methanol solvent molecule by the type C26-H26…O10 and O11-H11A...O10, respectively. The carboxylic acid group in dibenzoyl tartrate anion forms hydrogen bond donor with carboxylate ion of adjacent HQDBT anion and hydrogen bond acceptor with hydroxyl group of 8-HOQ cation and methanol by O(2)-H(2A)...O(4), O(9)-H(9A)...O(1) and O(11)-H(11A)...O(1), respectively (see Table 2).

In the HOQDBTA structure, the O atoms of solvents (MeOH and H2O) acts as both donor and acceptor, while 8HOQ donates a hydrogen bond. In DBTA, the one O atom of the carboxylate group accepts a hydrogen bond and other protonated O atom donates. So the carboxylate group which has transfer its proton acts as a hydrogen bond acceptor with water molecule (see Table 2). The methanol and water solvent molecules form hydrogen bond with 8HOQ and DBTA moiety through N1, O6, O3, O1 and C26, in donating and accepting interactions, forming several crosslinks between moieties. Thus giving a stable three dimensional complex structure. The bond distance N1-C26 and C27-N1 for pure 8HOQ was reported as 1.350(17) Å and 1.383(16)

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Å, respectively, whereas in present work, it was found to be 1.332(5) Å and 1.352(4) Å for protonated

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8HOQ (see Table 3) [14]. In carboxylate (-COO-) group, the bond distance is identified to be C4-

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O3=1.210(3) Å and C4-O4=1.293(3) Å, whereas in carboxyl (-COOH) the bond distance is C1O1=1.242(3) Å and C1-O2=1.245(3) Å shows that the dibenzoyl-(L)-tartaric acid is in monoionized

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state and confirms the protonation of 8-hydroxyquinoline.

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The O…N→D…A distance of 2.672(4) Å is a clear indicative of strong intermolecular hydrogen

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bonding. A criterion for hydrogen bonding between oxygen and nitrogen atoms is considered to be

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that the distance O…N should be shorter than the sum 3.07Å, of the van der Waals radii. The X–

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H…Y hydrogen bond angle tends toward 180º and should preferably be above 110º. In the present

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work it is 157.4ᴼ and shows stronger hydrogen bonding between donor N atom of 8hydroxyquinolinium cation and oxygen atom (O11) in methanol [15]. Here the 8-HOQH+ cation is

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connected to DBTA- anion through methanol and water molecule.

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The interatomic bond distances, angles along with computed geometrical parameters (B3LYP and HF methods) are displayed in Table 3. The theoretical optimized geometry of the title compound was

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shown in Fig.2c. Calculated geometric parameters values are slightly smaller or larger than those of experimental values. The theoretical bond length of NH was found to increase by 0.14Å compared to the experimental bond length. This discrepancy is due to the fact that experimental data was collected in crystalline form which includes hydrogen bond and electrostatic forces of interactions among the molecules but theoretical calculation was performed for isolated molecule in gas phase.

3.2. Ultraviolet-Visible (UV-Vis) spectroscopic study: The absorption spectrum was recorded using the instrument Shimadzu UV 1700 pharma spectrophotometer in the range 200-1000 nm. The absorption edge at 440nm is a good indicator of the presence of a chromophores (-COOH and –COO- group) which is responsible for the appearance of green colour HOQDBT crystal. The enhancement of wavelength is accompanied by the presence of auxochromes such as –OH and NH+ in 8-hydroxyquinolinium cation. From the Jiao et al. [16] the maximum absorption of DBTA (colourless) was reported as 230nm and from the Rajasekaran et al.

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[17] the UV cutoff wavelength of 8HOQ was reported below 400nm. When the two compounds

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(containing electron donor and acceptor groups) interact with each other, resulting species (C18H13O8-,

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C9H8NO+, CH4O, H2O) is intensely yellow colour which is due to the formation of a charge transfer complex. But in the HOQDBT complex the energies of the orbitals are such that the HOMO to

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LUMO transition is of much lower energy and falls in the visible region. From the Fig.3a, it can be

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inferred that the crystal is transparent in the Nd:YAG laser fundamental and second harmonic

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wavelength. Hence the grown crystal can be useful for frequency doubling applications.

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The plot of (αhν)2 versus hν are used to evaluate the optical band gap and it is depicted in Fig.3b. The

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optical absorption coefficient (α) was calculated from the transmission (T) using the following

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relation, α = ln(1/T)/d

(4)

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where ‘d’ is the thickness of the crystal in mm. According to the Tauc relation [18] the absorption coefficient (α), for a material is given by the following relation,

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(αhν) = A (hν-Eg)n

(5)

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where A is the band edge constant that depends on the transmission probability. ‘n’ is the index that characterises the optical absorption process, theoretically equal to 1/2,3/2,2 and 3 depending on the transmissions such as direct allowed, direct forbidden, indirect allowed and indirect forbidden transitions, respectively. The extrapolation of the linear portion to zero abscissa gives the band gap. The direct optical band gap of 2.8eV is found to be the predominant transition taking place in the material and can be useful for optical applications.

3.3. Vibrational spectral analysis:

Fourier transform infrared (FTIR) spectrum was recorded in the 4000–400 cm−1 range at room temperature using KBr pellet technique with Spectrum one: FT-IR spectrometer of resolution 1.0cm-1. Raman spectrum (RS) in the 50-4000 cm−1 range was measured with a BRUKER RFS 27: Stand alone FT Raman spectrometer. The Nd:YAG laser was used as an excitation with the resolution 2 cm−1. FTIR and FT-Raman spectrum and their wavenumber assignments are shown in Fig.4 a, b and Table.4, respectively. The formation of the charge transfer complex during the reaction of dibenzoyl-(L)-tartaric

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acid with 8-hydroxyquinoline is strongly evidenced by the presence of the main groups such as

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carboxylic acid (-COOH), carboxylate (-COO-) anion, water, methanol and amine in 8HOQDBT complex. The HOQDBTA molecule includes weak intra- and inter-molecular hydrogen bonding [19].

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Such bonds are characterized by intramolecular O-H...O interactions in DBTA network, O-H...O

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intermolecular interactions between DBTA and 8HOQ which are connected to each other by methanol

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and water solvent molecules. The frequency of such vibrations strongly depends on the length of

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those bonds.

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A carboxylic acid functional group combines the features of alcohols and ketones because it has both the O-H bond and the C=O bond. Therefore carboxylic acids show a very strong and broad

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band covering a wide range between 2800 and 3500 cm-1 for the O-H stretch. At the same time they

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also show the stake-shaped band in the middle of the spectrum around 1710 cm-1 corresponding to the

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C=O stretch. The weaker C-H stretching bands are generally superimposed upon the broad O-H band. In the present case, it was observed in the region 3057-2606cm-1 and 3075-2961cm-1 in the FTIR and

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FT-Raman spectrum, respectively.

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Carboxylic acids have a strong band in the region 1315-1280cm-1. In the present work, C-O

stretching was observed at around 1312cm-1 in both FTIR and FT-Raman spectrum. Generally, the asymmetric C=O stretching is observed at 1740-1680cm-1. The asymmetric C=O stretching was identified at 1731 and 1711cm-1 in both FTIR and FT-Raman spectrum, respectively. The stronger band at 1405cm-1 and weaker band at 1402cm-1 in FTIR and FT-Raman spectrum, respectively was

assigned to OH in-plane deformation of COOH group. Similarly the band in the region 960-875cm-1 was assigned to OH out of plane deformation vibration of COOH group. The carboxylate anion has two strongly coupled C=O bonds with bond strengths intermediate between C=O and C-O. The carboxylate ion gives rise to two bands: a strong asymmetrical stretching band near 1650-1550cm-1 and a weaker, symmetrical stretching band near 1400cm-1. In this study, the band at 1640,1631,1599,1584 and 1564 cm-1 in FTIR and medium strong peak at 1600cm-1 in FTRaman was assigned to asymmetric C=O stretching. The band at 1405 and 1402cm-1 in FTIR and FTRaman spectra was assigned to C-O symmetrical stretching vibration. The O=C-O-C benzoate display

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stretching bands at 1262, 1112cm-1 as a medium strong and 1272cm-1 as a weak in FTIR and FT-

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Raman spectrum, respectively [20,21].

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An interesting feature linked with quinolones is tautomerizm due to weak intramolecular hydrogen bonding between O–H group and pyridine N-atom. Because of tautomerizm, the

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hydroxyquinoline derivatives resemble urea, which is one of the very few organic process in which

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second harmonic generation has actually been observed. Hydroxyl vibrations, which are hydrogen

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bonded to aromatic ring π electron systems absorb at 3670–3580 cm−1 [22]. The O–H stretching band

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is medium to strong intensity in the infrared spectrum, although it may be broad. In Raman spectra the

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band is generally weak [23]. Broad infrared band observed at 3409cm-1 was attributed to stretching

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vibrations of OH group attached to quinoline. Its Raman counterpart is not observed. The free hydroxyl group of phenols absorbs strongly in the 3700-3584cm-1 region. The

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stretching of OH group in methanol is observed at 3583cm-1 [24]. The asymmetric stretching

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vibrations of methyl group is located at 2963cm-1 and symmetric vibrations is observed at 2902cm-1 in FTIR spectrum. The stretching and deformation vibration of water molecule was identified at 3515

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and 1731cm-1, 1712cm-1, respectively in FTIR spectrum. Heteroaromatics containing an N-H group show N-H stretching absorption in the region 3500-3220cm-1. The position of absorption within this general region depends on the degree of hydrogen bonding. The stretching of N-H group occurs as a broad band in the 3057-2954cm-1 region [25-27]. The above analysis confirms the formation of title compound by the identification of the characteristic bands in both FTIR and FT-Raman spectra. 3.4 Thermal Analysis:

The thermogravimetric (TG)/differential thermal analysis (DTA) was carried out in the nitrogen atmosphere at a heating rate of 10ᴼC min-1 from 30 to 950ᴼC using thermal analyzer (TG/DTA6200). The differential scanning calorimetry (DSC) was carried out in the range of 30 to 500C in the argon atmosphere at a heating rate of 10C/min using NETZSCH DSC 204. The TG/DTA and DSC plots are shown in Fig.5a and Fig.5b, respectively. The TG curve of HOQDBT shows three stage decomposition. The first stage decomposition from 30-65ᴼC was due to the volatilization of methanol molecule with the mass loss of 7.64%. The second stage weight loss from 145ᴼC-175ᴼC was due to the dehydration of coordinated water

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molecule which links cation and anion moieties with the mass loss of 67%. The HOQDBT loses 89%

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of its weight from 176-225ᴼC in the third step decomposition owing to the decarboxylation of

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carboxyl group (-COOH) to carbon dioxide (CO2↑ gas) followed by the mass loss of 100%. The DTA shows two endothermic peaks. The first peak at 61ᴼC was due to the melting of the title compound. In

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DSC (see Fig 5b) this peak was observed as just the beginning of melting but exact melting point was

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observed at 87.5ᴼC. The enthalpy change is the area under the peak in DSC curve. The enthalpy of

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melting was found to be 151.4 J/g. The second endothermic peak at 150ᴼC in DTA coincides nearly

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with the DSC peak at 153.1ᴼC. This was due to the desolvation of the title compound.

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3.5. Nuclear magnetic resonance (NMR) analysis: The 1H NMR spectrum was recorded using Bruker AVANCE III 500 MHz (AV 500) multi

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nuclei solution NMR spectrometer and is shown in Fig.6. The assignments of Proton NMR chemical

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shifts in ppm is displayed in Table 5. Methyl (-CH) protons of dibenzoyl-(L)-tartrate have one neighbour, and therefore appear as a strong intense doublet at δ=5.913 and 5.911ppm. The ortho

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position of aromatic protons are observed as a doublet at δ=8.048 and 8.032ppm. The para and meta position of aromatic protons appears as a multiplet at δ=7.4ppm. The broad peak at δ=9.92ppm was due to the charge transfer proton (–NH) which was not present in the parent compound. This shows that –COOH group of DBTA is involved in the hydrogen bonding with –N atom of 8HOQ. Doublet observed at 8.85ppm is assigned to H-2 proton of 8HOQ. The H-4 proton of 8HOQ appears as a doublet at 8.34 and 8.32ppm. Another doublet observed at

7.116 and 7.101ppm was assigned to H-5 proton of 8HOQ. The multiplet observed at δ 7.5ppm was consigned to H-3 and H-6 protons in 8HOQ. The triplet peak at δ=7.74ppm was due to H-7 proton of 8HOQ. Thus it confirms the molecular structure of the title compound.

3.6. First-order hyperpolarizability (β) The first-order hyperpolarizability (β) is the second-order electric susceptibility per unit volume. The molecules exhibiting large hyperpolarizabilities have a strong NLO potential and could be useful for optical devices [28, 29]. For exhibiting larger molecular hyperpolarizabilities, the system must be

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asymmetric and should contain polarizable electron donor and acceptor groups.

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The third rank tensor of first hyperpolarizability is described by a 3×3×3 matrix. The matrix is

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reduced to 10 components due to Kleinman symmetry [30]. Hyperpolarizability calculations were performed using B3LYP and HF methods for urea and HOQDBT geometry and are collected in Table

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6. The βxxx and μx is the largest component parallel to the charge transfer axis under the intermolecular

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interactions. The β value of the urea and title compound calculated by B3LYP method were found to

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be 1.046×10-30 and 4.813×10-30, respectively. The β value of the urea and title compound calculated by

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HF method were found to be 1.49×10-30esu and 5.277×10-30esu, respectively. The β of 8HOQDBT

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performed using B3LYP and HF methods was found to be 4.6 and 3.5times higher than that of urea,

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respectively. The reason for disagreement between the theoretical and experimental results could be due to the fact that quantum chemical calculations are performed by considering the isolated molecule

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in gas phase and without taking into account the interaction between molecule and solvent. But in the

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experimental one, the material is in the crystalline (solid state) which involves electrostatic force of

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attraction and hydrogen bond interaction among the molecules.

3.7. Molecular orbitals: The HOMO is the orbital that acts as an electron donor, since it is the outermost (highest energy) orbital containing electrons. The LUMO is the orbital that acts as the electron acceptor, since

it is the innermost (lowest energy) orbital that has the room to accept electrons. In the Fig.7 the red atomic orbital lobes are positive phases and the green atomic orbitals are negative phases. The HOMO-LUMO gap value of the HOQDBT compound was found to be 2.34eV. The HOMO-LUMO energy gap value is found to be in agreement with the experimental UV-Visible energy gap value (2.8eV). The HOMO→LUMO transition and the small HOMO–LUMO energy gap explains the probable intermolecular charge transfer (ICT) taking place from 8HOQ electron donor group to the DBTA electron acceptor group to form HOQH+.DBTA- charge transfer complex. The HOMO and LUMO plots obtained using B3LYP and HF methods are shown in Figure 7a, b, c and d, respectively.

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The HOMO calculated at B3LYP level contains more –COO- part of dibenzoyl-(L)-tartrate anion and

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less NH+ cation and LUMO consist of more 8HOQH+ cation (8HOQ+) than carboxylate (-COO-) anion group of DBTA-, whereas HOMO calculated using HF method contains benzene ring and C=O

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of DBTA and 8HOQH+ cation in LUMO.

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3.8. Molecular Electrostatic potential surface:

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The electrostatic potential (ESP) plot for HOQDBT is shown in Fig.8. For any two molecules,

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electrons will flow from an electron source to a place of electron deficiency i.e. from nucleophile (less

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electronegativity) to electrophile (more electronegativity). The molecular electrostatic potential is the

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potential energy of a proton at a particular location near a molecule. The more red/blue colour differences indicates that the molecule is said to be more polar. The electrostatic potential is shown by

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colouring the isosurface with contours. The electron–rich regions (negative potentials), electron-poor

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regions (positive potentials) and the neutral regions were represented by red, blue and green colors, respectively. Potential increases in the order red < orange < yellow < green < blue. The colour code of

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these maps is in the range between −0.0882 (deepest red) to 0.0882a.u. (Deepest blue). The positive ESP values (blue color) were traced on NH+ and CH group of 8HOQH+ cation whereas the most negative ESP values (red color) were located on -COO groups of dibenzoyl-(L)-tartrate anion.

3.9. Powder Second Harmonic Generation (SHG):

The study of SHG conversion efficiency was carried out using Kurtz-Perry method [31]. The single crystals of HOQDBT were ground and sieved for five different particle size of below 63, 63-105, 105-120, 120-150 and 150-210 microns and were filled into separate micro capillary tubes of diameter 1.8mm. A Q-switched Nd:YAG laser beam carrying an input beam energy of 8mJ/pulse at the fundamental wavelength of 1064nm was used. The green emission is seen as an output signal was collected by a monochromator to the photomultiplier tube and was converted into an electrical signal. The digital storage oscilloscope displays the output signal. SHG output for various particle sizes is shown in Fig.9. The SHG output for standard KDP was found to be 5mV. It was observed from the

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Fig.9 that the SHG output decreases with increasing particle size. Thus the material is said to exhibit

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non phase-matchable property. The average NLO susceptibility was estimated to be 0.6 times that of

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KDP. The chirality and strong hydrogen bonding character is the origin of SHG process. From the XRD study, it is clear that the moieties are connected through N-H…O and O-H…O hydrogen bonds.

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Therefore the addition of dipole moments in the molecule leads to total macroscopic polarization in

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the crystal [32].

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4. Conclusions:

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The experimental and theoretical investigations were carried out for novel 8-

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hydroxyquinolinium dibenzoyl-(L)-tartrate methanol monohydrate. The single crystal XRD was used to solve the complete structure. Optical assessment showed that the title compound was transparent in

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the region 440-1100 nm. The vibrational and NMR analyses confirmed the formation of title acid-

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base complex. The melting point of the crystal was found to be 87.5ᴼC. The First-order hyperpolarizability (β) was calculated to be higher than that of urea. Molecular orbitals and

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electrostatic potential surface reveals the charge distribution in the molecules. The relative powder SHG efficiency of HOQDBT was estimated to be 0.6times that of standard KDP and it exhibits nonphase matchable property.

Acknowledgements: The author Dr.R.Nagalakshmi is thankful to Council of Scientific and Industrial Research (Sanction No: 03(1158)/10/EMR-II), New Delhi for the financial assistance under major research project and N.Sudharsana is thankful to CSIR for awarding JRF in this project. The authors are grateful to thank Dr.R.Justin Joseyphus and Dr.M.Ashok Department of Physics, National Institute of Technology, Tiruchirappalli, India for thermal (DTA/TG) and UV facilities, respectively. The authors are also thankful to SAIF, IIT Madras for the single crystal XRD, FTIR, FT-Raman and DSC measurements and Prof. P.K. Das, Department of Inorganic and Physical Chemistry, Indian Institute

RI

PT

of Science, Bangalore for the SHG measurements.

SC

Supplementary

CCDC: 954034 contains the supplementary crystallographic data for the compound reported in this

N

U

article.

A

References:

D

Synthetic Met. 127 (2002) 99–104.

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1.S.Debrus, H. Ratajczak, J. Venturini, N. Pincon, J. Baran, J. Baryckid, T. Glowiak, A. Pietraszko,

TE

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Michael Belsley, DmitryIsakov, Physica B 406 (2011) 4019–4026.

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4. M.K. Marchewka, S. Debrus, A. Pietraszko, A.J. Barnes, H. Ratajczak, J. Mol. Struct. 656 (2003) 265–273.

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5. I. Quasim, A. Firdous, B. Want, S.K. Khosa, P.N. Kotru, J. Cryst. Growth 310 (2008) 5357–5363. 6. R.Nagalakshmi, V.Krishnakumar, Hans Hagemann, S. Muthunatesan, J.Mol.Struct. 988 (2011) 1723. 7. V.Krishnakumar, R.Nagalakshmi, P.Janaki, Spectrochim. Acta Part A: Mol.Biomol.Spectrosc. 61 (2005) 1097–1103. 8. R.W.Tennant, B.H. Margolin, M.D.Shelby, et al., Science. 236 (1987) 933-941.

9. R.E. Bambury, Burger’s Medicinal Chemistry, Part II; John Wiley: New York, 1979, pp 41–81. 10. S.Yurdakul, K. Arıcı, J.Mol.Struct. 691 (2004) 45–49. 11.M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomery Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K.

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Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels,

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M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q.

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Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M.

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Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez and J. A. Pople,

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13. A.Frisch, A.B.Nielsen, A.J.Holder, Gaussview user Manual, Gaussian Inc., Pittsburg, 2001.

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14. P.Roychowdhury, Acta cryst. B34 (1978) 1047-1048.

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15. E.Arunan, Pure Appl. Chem. 83 (2011) 1637–1641. 16. F.P. Jiao, X.Q. Chen, Z.D. Fu, Y.H. Hu, Y.H. Wang, J. Mol. Struct. 921 (2009) 328–332.

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17. M.Rajasekaran, P.Anbusrinivasan, S.Mojumdar, J.Therm.Anal.Calorim, 100 (2010) 827-830.

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18. J.Tauc, Amorphous and Liquid Semiconductors, Plenum, New York, 1974, pp.159–220. 19. V. Krishna Kumar, R. Nagalakshmi, Spectrochim. Acta Part A: Mol.Biomol.Spectrosc. 66 (2007)

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924–934.

20. R.M. Silverstein, F.X. Webster, D.J. Kiemle, Spectrometric Identification of Organic Compounds, Wiley, New York, 2005, pp 87-118. 21. N.B.Colthup, L.H. Daly, S.E. Wiberley, Introduction to infrared and Raman spectroscopy, Academic Press, New York, 1964, p 221, 279, 285.

22. G. Socrates, Infrared and Raman Characteristic Group Frequencies, third ed., Wiley, New York, 2001. 23. R.M. Silverstein, G.C. Bassler, T.C. Morrill, Spectrometric Identification of Organic Compounds, fifth ed., John Wiley & Sons, Inc., New York, 1981. 24. Sibel Demir, Muharrem Dincer, Elif Korkusuz, Ismail Yıldırım, J. Mol. Struct. 980 (2010) 1–6. 25. Katalin Nemak, Maria Acs, Zsuzsa M Jaszay, David Kozma. Elemer Fogassy, Tetrahedron 52 (1996) 1637-1642. 26. V. Arjunan, P.S. Balamourougane, M. Kalaivani, Arushma Raj, S. Mohan, Spectrochim.Acta Part

A.Basoglu,

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29. C.E.Powell, J.P.Morrall, S.A.Ward, M.P.Cifuentes, E.G.A.Notaras, M.Samoc, M. G. Humphrey,

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J. Am. Chem. Soc. 26 (2004) 12234-12235.

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30. D.A. Kleinman, Phys. Rev. 126 (1962) 1977-1979.

M

31. S.K.Kurtz, T.T. Perry, J.Appl.Phys. 39 (1968) 3798-3813.

D

32. P.N.Prasad, D.J.Williams, Introduction to nonlinear optical effects in molecules and polymers,

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John Wiley & Sons, Inc., 1991, p 146.

Figure Captions: Fig.1a As-grown HOQDBT single crystal from methanol solvent Fig. 1b The solubility curve for HOQDBT in methanol solvent Fig.2a ORTEP diagram of HOQDBT crystal Fig.2b Crystal packing diagram of HOQDBT crystal viewed along c-axis Fig.2c Optimized structure of HOQDBT based on DFT B3LYP/6-31G (d,p) basis set Fig.3a UV-Vis absorption spectrum b. Plot of (αhν)2 Vs. Energy for HOQDBT crystal Fig.4 FTIR and FT-Raman spectra of HOQDBT

PT

Fig.5a TG/DTA curve for HOQDBT

RI

Fig.5b DSC curve for HOQDBT

SC

Fig.6 1H NMR spectrum of HOQDBT

Fig.7 Frontier molecular orbital a. HOMO b. LUMO orbitals calculated at B3LYP level and c.

U

HOMO d. LUMO calculated at HF level

N

Fig.8 Electrostatic potential surface of HOQDBT molecule. The contour electron density iso value is

A

0.0004

D

M

Fig.9 Particle size vs. SHG intensity curve of HOQDBT

EP

Identification code

TE

Table 1 Crystal data and structure refinement for HOQDBT

Shelxl C28 H27 N O11

Formula weight

553.51g/mol

Temperature

293(2) K

A

CC

Empirical formula

Wavelength

0.71073 Å

Crystal system, space group

Orthorhombic, P212121

Unit cell dimensions

a = 7.7175(2) Å α = 90ᴼ b = 16.7313(7) Å β= 90ᴼ

c = 21.1458(5) Å γ = 90ᴼ 2730.43(15) Å3

Z, Calculated density

4, 1.346 Mg/m3

Absorption coefficient

0.105 mm-1

F(000)

1160

Crystal size

0.30 x 0.30 x 0.25 mm3

Theta range for data collection

2.28 to 24.86ᴼ

Limiting indices

-9<=h<=9, -19<=k<=19, -24<=l<=24

Reflections collected / unique

24419 / 4706 [R(int) = 0.0409]

Completeness to theta = 24.86

99.7 %

Absorption correction

Semi-empirical from equivalents

Max. and min. transmission

0.9865 and 0.9536

Refinement method

Full-matrix least-squares on F2

Data / restraints / parameters

4706 / 5 / 373

RI

SC

U

N 1.049

A

Goodness-of-fit on F^2

M

Final R indices [I>2sigma(I)]

TE

D

R indices (all data) Absolute structure parameter

PT

Volume

R1 = 0.0443, wR2 = 0.1019 R1 = 0.0594, wR2 = 0.1094 0.8(12) 0.0023(5)

Largest diff. peak and hole

0.182 and -0.172 e.A-3

A

CC

EP

Extinction coefficient

PT RI SC U N

A

Table 2 Hydrogen bonds for HOQDBT [Å and ᴼ]

M

__________________________________________________________________________ d(D-H)

d(H...A)

d(D...A)

<(DHA)

0.93

2.45

3.350(5)

162.9

N(1)-H(1A)...O(11)

0.86

1.86

2.672(4)

157.4

O(2)-H(2A)...O(4)#2

0.82

1.70

2.501(2)

166.4

0.82

1.81

2.605(3)

161.8

D

D-H...A

EP

TE

C(26)-H(26)...O(10)#1

A

CC

O(9)-H(9A)...O(1)#3 O(11)-H(11A)...O(1)#1

0.946(19)

2.42(4)

3.060(4)

125(3)

O(11)-H(11A)...O(10)#1

0.946(19)

2.25(3)

3.035(4)

140(4)

O(10)-H(10A)...O(6)

0.953(17)

1.97(2)

2.918(3)

171(4)

O(10)-H(10B)...O(3)#2

0.912(16)

2.153(16) 2.981(3)

151(3)

___________________________________________________________________________ Symmetry transformations used to generate equivalent atoms: #1 -x+2,y-1/2,-z+1/2 #2 x+1,y,z

#3 -x+5/2,-y,z+1/2

TE

EP

CC

A D

PT

RI

SC

U

N

A

M

Table 3 Comparison of Selected experimental and calculated B3LYP and HF geometric parameters of HOQDBT, Bond lengths [Å] and angles [ᴼ]

Expt

Calcd at B3LYP

Calcd at HF

r(C(1)-O(1))

1.242(3)

1.206674

1.18478

r(C(1)-O(2))

1.245(3)

1.3579

1.3266

r(C(1)-C(2))

1.522(3)

1.522947

1.516779

r(C(2)-C(3))

1.504(4)

1.525

1.521

r( C(3)-C(4))

1.519(3)

1.561936

r(C(4)-O(3))

1.210(3)

1.256556

r(C(4)-O(4))

1.290(3)

1.255218

r(C(5)-O(8))

1.194(3)

1.214169

1.189234

r(C(5)-O(7))

1.341(3)

1.350119

1.322566

r(C(5)-C(6))

1.485(4)

r(C(12)-O(6))

1.545064

U

SC

RI

1.2349

1.229622

1.493829

1.205(3)

1.219683

1.194589

1.343(3)

1.336631

1.310348

1.472(4)

1.495600

1.494291

1.332(4)

1.340484

1.318682

r(N(1)-C(27))

1.352(4)

1.368865

1.361112

r(N(1)-H(1A))

0.8600

1.02889

1.005594

r(O(9)-H(9A))

0.8200

0.966307

0.943502

r(O(10)-H(10A))

0.953(17)

0.97125

0.946937

r(O(10)-H(10B))

0.912(16)

0.965279

0.942494

<(O(3)-C(4)-O(4))

126.3(2)

129.9857

129.43

<(O(6)-C(12)-O(5))

123.1(2)

126.01

125.316233

<(O(8)-C(5)-O(7))

123.4(2)

123.98

123.920575

<(O(8)-C(5)-C(6))

124.9(2)

124.07930

123.514028

A

N

1.494258

M

r(C(12)-O(5))

CC

EP

TE

r(C(26)-N(1))

D

r(C(12)-C(13))

A

PT

Parama

119.2(2)

112.2569

112.50081

<(O(6)-C(12)-C(13))

125.4(3)

123.32

123.238709

<(H(10A)-O(10)-H(10B))

109(2)

102.134

105.124920

<(N(1)-C(26)-C(25))

120.0(4)

121.153

121.498002

<(N(1)-C(26)-H(26))

120.0

115.17

115.647085

<(C(26)-N(1)-H(1A))

118.1

116.693

117.664018

<(C(19)-O(9)-H(9A))

109.5

109.9

111.747916

Φ(C(25)-C(26)-N(1)-C(27))

0.8(4)

0.876025

0.538517

Φ(C(26)-N(1)-C(27)-C(23))

0.3(4)

0.470135

0.496952

Φ( C(2)-C(3)-C(4)-O(3))

53.7(3)

68.244327

Φ( O(1)-C(1)-C(2)-C(3))

54.4(3)

39.426923

RI

SC

N A M D TE EP CC A

66.3911

43.144638

r- distance between the atoms, <-angle between the atoms, Φ-dihedral angle

U

a

PT

<(O(3)-C(4)-C(3))

Table 4 FTIR and FT-Raman wavenumbers and their assignments

wavenumber(cm-1)a

wavenumber(cm-1)a

3583(ms)

-

νOH (methanol)

3515 (ms)

-

νssOH(H2O)

3409(br)

-

νOH

3057(ms)

3075(s)

νCH, νNH , νOH

2963,2954(ms)

2961(w)

νCH, νOH, νNH,νasCH3

2912(vw)

-

νCH, νOH

2902(vw)

-

νCH, νOH, νssCH3

2810(vw)

-

2606(vw)

-

1731,1712(ms) (d)

1731,1711(ms)(d)

1640(w)

1639(vw)

SC

RI

PT

FT-Raman

U

Band assignmentsb

FTIR

N

νCH, νOH

νasC=O, δOH(H2O), νringC=C νas C=O(carboxylate), νss C=O(carboxylic), νC-C, νassCOC

1600(s)

νasC=O (carboxylate), νssC-C=C, νC-C

-

νas C=O(carboxylate), νC-N, δOH

-

νC-C

CC

TE

D

M

A

νCH ,νOH,νringC=C

1512(vvw)

1514(vw)

νC-C

1491(vvw)

1478(vw)

νassC-C=C, νC-C

1452(ms)

1453(vw)

νassC-C=C ,νCH, δasC-H(alkane), νC-C

1406(s)

1403,1385(ms)(d)

νssC-O(carboxylate), νC-O, νC-C, βO-H

1600(ms)

EP

1565(w)

A

1520(vvw)

(COOH), δssC-H 1334(w)

1334(w)

νC-C, ρO-H

1312(vw)

νC-N, δCH, νCC, νssOCO, νC-O

1262(ms)

1272

δCH, νO=C-O-C benzoate

1213(w)

-

νC-O, δCH, νCN

1174(w)

-

νC-C, δC-H, ρC-H(alkane)

1134(w)

1142(vw)

δC-H, νC-N

1112(ms)

-

δC-H, νC-N, vO=C-O-C benzoate

1099(sh)

1099(w)

δC-H, νC-C,νC-O

1070(w)

1064(ms)

νC-O

1046(w)

-

νC-C, δC-H, ρ(CH3), νC-O

1023(w)

1023(w)

νC-C, νC-O

1001(w)

1002(s)

νC-C, νC-O(methanol)

890(w)

908(w)

γC-H, γOH

848(w)

850(ms)

γC-H

831(s)

-

U

785(w)

786(vvw)

751(ms)

-

714(vs)

715(ms)

684(w)

D

RI

SC

N

γC-H

M

A

γC-H, ϕCOO-

γC-H, γringC=C γC-H γC-O

617(w)

γC-C

579(w)

583(vw)

γC-C

CC

TE

678(vw)

γringC-H, γCN

-

542(vvw)

γC-C,βCCC

490(s)

490(w)

γC-C

-

349(vvw)

βC-N

-

333(vvw)

γC-N

-

281(w)

γCCC, γCH

625(w)

EP

616(w)

559(w), 543(w), 531(w)

A

PT

1313(w)

-

180(ms)

γCCC, γCH

-

68(s)

Lattice vibrations

a

s,strong;br-broad; ms, medium strong; w,weak; vw, very weak; vvw, very very weak. bν, stretching;

δ, bending; ω, wagging; ρ, rocking; ϕ, scissoring; νas, asymmetric stretching; νss, symmetric stretching;

RI

PT

β, in plane bending; γ, out of plane bending.

SC

Table 5 Proton NMR chemical shifts in ppm and assignments of HOQDBT

Proton chemical shift

H2 HOQ

8.85(d)

U

Assignments

A

M

H4 HOQ

N

H3,H6 HOQ

8.34,8.32(d) 7.116,7.101(d)

H7 HOQ

7.74(t)

N-H HOQ

9.922(br)

ArC-H meta and para

7.4(m)

TE

D

H5 HOQ

EP CC A

7.5(m)

ArC-H ortho DBTA

8.048,8.032(d)

-CH DBTA

5.91(d)

Table 6 Dipole moment µ (D), Polarizability αij (×10-23esu) and First-order hyperpolarizability βijk

µx

6.2323

6.779

µy

3.901

4.2369

µz

0.7789

1.0986

µtotal

7.393D

8.069

αxx

423.899

αyy

-22.122

αzz

365.402

332.414

αxy

49.688

SC

U

N

335.280 -23.486

αxz

15.0866

16.6356

αyz

240.862

223.465

αtotal

3.78

3.182

βxxx

527.567

568.813

βyyy

137.1251

171.551

βzzz

84.9204

116.570

βxyy

145.2728

160.610

βxxy

51.1036

58.129

βxxz

16.0799

-2.313

EP CC A

A

M

TE

51.787

PT

HF/6-31G(d,p)

RI

B3LYP/6-31G(d,p)

D

(×10-30esu) of HOQDBT

-22.3644

-21.3269

βyzz

28.1307

17.6512

βyyz

-34.8997

-33.77

βxyz

58.6725

67.7821

βtotal

4.813

5.277

A

N

U

SC

RI

PT

βxzz

A

CC

EP

TE

D

M

Fig. 1a

PT

Fig. 1b

A

EP

CC

Fig. 2b

TE

D

M

A

N

U

SC

RI

Fig. 2a

Fig. 2c

TE

EP

CC

A D

Fig. 3b

PT

RI

SC

U

N

A

M

Fig. 3a

TE

EP

CC

A Fig. 4

D

PT

RI

SC

U

N

A

M

TE

EP

CC

A D

Fig. 5b

PT

RI

SC

U

N

A

M

Fig. 5a

TE

EP

CC

A D

Fig. 7

PT

RI

SC

U

N

A

M

Fig. 6

TE

EP

CC

A D

Fig. 9

PT

RI

SC

U

N

A

M

Fig. 8