Journal of Molecular Liquids 197 (2014) 386–394

Contents lists available at ScienceDirect

Journal of Molecular Liquids

j ourna l homepage: www.e lsev ie r .com/ locate /mol l iq

Estimation of ground and excited states dipole moments of α-hydroxyphenyl hydrazone derivatives: Experimental and quantumchemical methods

İsa Sıdır a,⁎, Yadigar Gülseven Sıdır a, Ferhat Demiray b, Halil Berber c

a Bitlis Eren University, Faculty of Arts & Science, Department of Physics, 13000 Bitlis, Turkeyb Abant İzzet Baysal University, Vocational Higher School, Mudurnu, Bolu, Turkeyc Anadolu University, Faculty of Science, Department of Chemistry, 26470 Eskişehir, Turkey

⁎ Corresponding author. Tel.: +90 434 2285170; fax: +E-mail addresses: isidir@beu.edu.tr, isa.sidir@gmail.co

http://dx.doi.org/10.1016/j.molliq.2014.06.0010167-7322/© 2014 Elsevier B.V. All rights reserved.

a b s t r a c t

a r t i c l e i n f o

Article history:Received 21 April 2014Received in revised form 12 May 2014Accepted 2 June 2014Available online 13 June 2014

Keywords:HydrazoneDipole momentSolvatochromic shiftElectric fieldDensity of stateDensity functional theory

The ground state (μg) and excited state (μe) dipole moments of the studied α-hydroxy phenylhydrazones aredetermined by using solvatochromism theory which is based on the variation of Stokes shift with solvent'srelative permittivity and refractive index. Excited state dipole moments are found as larger than the groundstate dipole moment due to substantial redistribution of the π-electron density in more polar excited state.External electric field (EF) effect on HOMO–LUMO gap (HLG) and dipole moment is studied by GGA level oftheory. Density of states (DOS) and HOMO, LUMO plots are also investigated by GGAmethod. Solvent accessiblesurface (SAS) and molecular electrostatic potential (MEP) are visualized as a result of DFT calculations.

© 2014 Elsevier B.V. All rights reserved.

1. Introduction

The hydrazone derivatives are taken into account as promisinggroup in terms of their potential medical applications such as antitu-mor, antileukemic, antipsychotic, antiseptic, antifungal and antibac-terial activities. They have also clinical utility in the treatment ofvarious diseases in human lymph system. Hydrazone derivativescarried nitro group in the ortho-position along with hydrazonebridge seems to be relatively more active in interacting with surfacetumor markers. A group of hydrazones (isonicotinoylhydrazones)have been found effective as antituberculous agents in macrophages.Anticancer activity and exact interaction mechanism with tumor ofthese molecules are still research fields. Biological activity of suchcompounds is especially controlled by electronic properties andhydrophobicity. Therefore, research on solute–solvent specific andnon-specific interactions affords to understand the binding of acompound with target substrate [1–8]. Nevertheless, chemicalprocess of hydrazone compounds in solution is rarely investigated[6,7,9,10].

90 434 2285171.m (İ. Sıdır).

One significant group of hydrazone, phenylhydrazone has attractedattention for researchers due to their successful application in biochem-istry, medicine [11–16] and optical materials [17,18]. Phenylhydrazonealso can be used as fluorescence reagents because of their selectivity formetal ions [19] so, they are good ion detector when they react with ions[20,21].

In thepresentwork,we have determined the ground state and excit-ed state dipole moments of hyd-1, hyd-2 and hyd-3. Solvent effects onabsorption and fluorescence spectra are analyzed. A detailed theoreticalinvestigation has been performed on external electric field (EF) effecton dipole moment and HOMO–LUMO gap (HLG). In order to show theinteraction zone of the molecule with the solvent, solvent accessiblesurfaces are displayed. Density of states (DOS) and HOMO, LUMOplots are investigated by generalized gradient approximation (GGA)method.

2. Materials and methods

2.1. Theoretical background

The electric dipole moment of a polar solute polarizes the solvent sothat the solute itself experiences an electric field, the reaction field,

387İ. Sıdır et al. / Journal of Molecular Liquids 197 (2014) 386–394

which is proportional to the solute dipole moment in the ground andexcited states. Such proportionalities for the difference and sum ofabsorption, eνa , and fluorescence, eν f , maxima (in cm−1) have beendefined by the following equations:

eνa−eν f ¼ mL−M FLippert−Mataga ε;nð Þ þ constant ð1Þ

eνa−eν f ¼ mBFBakhshiev ε;nð Þ þ constant ð2Þ

eνa þ eν f

� �=2 ¼ −mK−C−V FKawski−Chamma−Viallet ε;nð Þ þ constant ð3Þ

where

mL−M¼2 μe−μg

� �2=hca30 ð4Þ

mB¼ 2 μe−μg

� �2=hca30 ð5Þ

mK−C−V¼2 μ2e−μ2

g

� �=hca30: ð6Þ

The symbols h and c are Planck's constant and the velocity oflight in vacuum, respectively. FLippert–Mataga [22], FBakhshiev [23],and FKawski–Chamma–Viallet [24,25] are solvent polarity functions andare given as:

FLippert−Mataga ε;nð Þ ¼ ε−12ε þ 1

− n2−12n2 þ 1

ð7Þ

y

(a)

(b)

(c)

y

y

HC

N

HN

OH

HC

N

HN

OH

Cl

NO2

HC

N

HN

OH

Cl

Fig. 1. B3LYP/6-311 + G(d) optimized molecular structure and direction of gro

FBakhshiev ε;nð Þ ¼ 2n2 þ 1n2 þ 2

ε−1ε þ 2

− n2−1n2 þ 2

" #ð8Þ

FKawski−Chamma−Viallet ε;nð Þ ¼ 2n2 þ 12 n2 þ 2� � ε−1

ε þ 2− n2−1

n2 þ 2

!þ

3 n4−1� �

2 n2 þ 2� �2

24 35: ð9Þ

The other symbols ε and n are dielectric constant and refractiveindex of the solvents, respectively. Employing linear curve fittingroute for eνa−eν f versus FLippert–Mataga, eνa−eν f versus FBakhshievs andeνa þ eν f� �

=2 versus FKawski–Chamma–Viallet gives mL–P, mB and mK–C–V,respectively. If it can be supposed that ground- and excited-statesdipole moments are parallel, then:

μg ¼ mK−C−V−mB

2hca3

2mB

!1=2

; ð10Þ

μe ¼mK−C−V þmB

2hca3

2mB

!1=2

; ð11Þ

μe ¼mK−C−V þmB

mK−C−V−mBμg ; mK−C−V ⟩mBð Þ: ð12Þ

Moreover, the method based on the empirical polarity scale, ETN [26],can be used for estimating dipole variation (Δμ) from solvatochromicshift. The theoretical basis for the correlation of the spectral shift withETN has been developed by Ravi et al. [27]:

eνa−eν f ¼ 11307:6ΔμΔμB

� �2 aBa0

� �3� ENT þ constant ð13Þ

x

x

x

und state dipole moment of (a) hyd-1, (b) hyd-2 and (c) hyd-3 molecules.

300 350 400 4500,0

0,5

1,0

hyd-3

Abs

orba

nce

Wavelength (nm)

DMF DMSO THF Chloroform

300 350 400 4500,0

0,2

0,4

0,6

0,8

1,0hyd-1

Abs

orba

nce

Wavelength (nm)

DMF DMSO THF Chloroform

300 350 400 450 500

0,0

0,2

0,4

0,6

0,8

1,0 hyd-2

Abs

orba

nce

Wavelength (nm)

DMF DMSO THF Chloroform

Fig. 2. Absorbance spectra of the studied α-hydroxy phenyl hydrazone derivatives.

350 400 450 500 5500

100

200

300

400

500

600

700

800

900

hyd-1

Fluo

resc

ence

inte

nsity

(a.u

.)

Wavelength (nm)

DMF DMSO Ethyl acetate THF Chloroform

400 450 500 550 600 650 7000

50

100

150

200

250

300

350

400

450

500

550

hyd-2

Fluo

resc

ence

inte

nsity

(a.u

.)

Wavelength (nm)

DMF DMSO Ethyl acetate THF Chloroform

350 400 450 500 550 6000

100

200

300

400

500

600

700

800

900

1000

hyd-3

Fluo

resc

ence

inte

nsity

(a.u

.)

Wavelength (nm)

DMF DMSO Ethyl acetate THF Chloroform

Fig. 3. Fluorescence spectra of the studied α-hydroxy phenyl hydrazone derivatives.

Table 1Absorption and fluorescence spectral data for the studied hydrazones.

No Solvent hyd-1 hyd-2 hyd-3

Abs. PL Abs. PL Abs. PL

1 n-Hexane 344.5 447 342 – 350.5 4312 1,4-Dioxane 348 406.5 395 471.5 359 417.53 Toluene 346.5 426.5 382.5 448.5 355.5 4384 Diethylether 343.5 428 376.5 456 348.5 4335 Chloroform 345 415 392 504.5 353.5 4576 Ethyl acetate 344 408 392 482 352 4187 THF 348.5 405 397 485.5 352 4218 Dichloromethane 346 407.5 387.5 502.5 352.5 4329 1-Butanol 351 410.5 403.5 500 358 43110 2-Propanol 348 410 404.5 504.5 356.5 42811 Acetone 320 418.5 402 506.5 352 42312 Ethanol 348 414 403 503 356 43013 Methanol 344 413.5 401 492 354 427.514 DMF 340 402 416 529 361 415.515 DMSO 349 408 427 545 367 427.5

PL: Photoluminescence or fluorescence (in nm).Abs.: Absorption (in nm).

388 İ. Sıdır et al. / Journal of Molecular Liquids 197 (2014) 386–394

where ΔμB = 9D and aB = 6.2 Å are the change in dipole moment onexcitation and Onsager radius of reference betaine dye, respectively.Δμ and a0 are the corresponding dipole moment change and Onsagerradius for the solute molecule. The change in dipole moment Δμ, canbe determined as:

μe−μg ¼ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

mENTx81

11307:6x 6:2=a0ð Þ3

sð14Þ

where mENTis the slope obtained from the linear plot of Stokes shift as

indicated in Eq. (15).

νa−ν f ¼ mENTENT þ constant: ð15Þ

2.2. Experimental details

(E)-2-((2-phenylhydrazono)methyl)phenol (hyd-1), (E)-4-chloro-2-((2-(4-nitrophenyl)hydrazono)methyl)phenol (hyd-2) and (E)-4-

Table 2Experimental spectral data for hyd-1.

hyd-1 Solvents νa ν f νa − ν f νa+ν f (νa+ν f )/2

1 n-Hexane 29,028 22,371 6657 51,399 25,699.52 1,4-Dioxane 28,736 24,600 4136 53,336 26,668.03 Toluene 28,860 23,447 5413 52,307 26,153.54 Diethylether 29,112 23,364 5748 52,476 26,238.05 Chloroform 28,986 24,096 4890 53,082 26,541.06 Ethyl acetate 29,070 24,510 4560 53,580 26,790.07 THF 28,694 24,691 4003 53,385 26,692.58 Dichloromethane 28,902 24,540 4362 53,442 26,721.09 1-Butanol 28,490 24,361 4129 52,851 26,425.510 2-Propanol 28,736 24,390 4346 53,126 26,563.011 Acetone 31,250 23,895 7355 55,145 27,572.512 Ethanol 28,736 24,155 4581 52,891 26,445.513 Methanol 29,070 24,184 4886 53,254 26,627.014 DMF 29,412 24,876 4536 54,288 27,144.015 DMSO 28,653 24,510 4143 53,163 26,581.5

Spectral values are in cm−1.

Table 3Experimental spectral data for hyd-2.

hyd-2 Solventsa νa ν f νa − ν f νa+ν f (νa+ν f )/2

1 n-Hexane 25,316 21,209 4107 46,525 23,262.52 1,4-Dioxane 26,144 22,297 3847 48,441 24,220.53 Toluene 26,560 21,930 4630 48,490 24,245.04 Diethylether 25,510 19,822 5688 45,332 22,666.05 Chloroform 25,510 20,747 4763 46,257 23,128.56 Ethyl acetate 25,189 20,597 4592 45,786 22,893.07 THF 25,806 19,900 5906 45,706 22,853.08 Dichloromethane 24,783 20,000 4783 44,783 22,391.59 1-Butanol 24,722 19,822 4900 44,544 22,272.010 2-Propanol 24,876 19,743 5133 44,619 22,309.511 Acetone 24,814 19,881 4933 44,695 22,347.512 Ethanol 24,938 20,325 4613 45,263 22,631.513 Methanol 24,038 18,904 5134 42,942 21,471.014 DMF 23,419 18,349 5070 41,768 20,884.015 DMSO 25,316 21,209 4107 46,525 23,262.5

Spectral values are in cm−1.

389İ. Sıdır et al. / Journal of Molecular Liquids 197 (2014) 386–394

chloro-2-((2-phenylhydrazono)methyl)phenol (hyd-3) molecules(Fig. 1) are synthesized by the method given in the reference [28]. Allof the solvents are of spectroscopic grade commercially available fromSigma-Aldrich. Solvents are checked using steady-state fluorescencefor the lack of fluorescence impurities in the wavelength ranges ofinterest. The concentrations of the solutions are 10−4–10−5 M. Ultravi-olet–visible (UV–vis) absorption spectra are recorded on a Perkin ElmerLambda-35 UV–vis spectrophotometer. Steady-state fluorescencespectra are recorded on a Perkin Elmer LS-55 Fluorescence Spectrometer.The positions of the absorption and fluorescence bands are determined

Table 4Experimental spectral data for hyd-3.

hyd-3 Solventsa νa ν f

1 n-Hexane 28,531 23,22 1,4-Dioxane 27,855 23,93 Toluene 28,129 22,84 Diethylether 28,694 23,05 Chloroform 28,289 21,86 Ethyl acetate 28,409 23,97 THF 28,409 23,78 Dichloromethane 28,369 23,19 1-Butanol 27,933 23,210 2-Propanol 28,050 23,311 Acetone 28,409 23,612 Ethanol 28,090 23,213 Methanol 28,249 23,314 DMF 27,701 24,015 DMSO 27,248 23,3

Spectral values are in cm−1.

by Gaussian curve fit analysis using OriginPro 7.5. Linear correlation anddata fit are also performed by using OriginPro 7.5.

All of the measurements are performed by using 1 cm quartz cell atroom temperature. Dielectric constant, ε and refractive index, n weretaken from the literature [29,30].

2.3. Computational method

We used density functional theory (DFT) implemented with B3LYP/6-311 + G(d) level of theory [31] to investigate SAS and MEP in gas

νa − ν f νa+ν f (νa+ν f )/2

02 5329 51,733 25,866.552 3903 51,807 25,903.531 5298 50,960 25,480.095 5599 51,789 25,894.582 6407 50,171 25,085.523 4486 52,332 26,166.053 4656 52,162 26,081.048 5221 51,517 25,758.502 4731 51,135 25,567.564 4686 51,414 25,707.041 4768 52,050 26,025.056 4834 51,346 25,673.092 4857 51,641 25,820.567 3634 51,768 25,884.092 3856 50,640 25,320.0

hyd-3

hyd-2

hyd-1

Fig. 4. Solvent accessible surfaces (according to atom color) of the studied α-hydroxyphenyl hydrazone derivatives calculated by B3LYP/6-311 + G(d) level of theory.

390 İ. Sıdır et al. / Journal of Molecular Liquids 197 (2014) 386–394

phase. Optimization and then, frequency calculation are performed toconfirm that there is no imaginary frequency in the optimized geometryindicating true energy minima. All calculations were carried out usingGaussian 09 W program [32].

External EF effect on HLG and μg was investigated by using GGAmethod. DOS and HOMO, LUMO plots are also calculated by the samemethod. Geometry optimization and total energy calculations are

Table 5Spectral treatment of the Lippert–Mataga, Bakhshiev, Kawski–Chamma–Viallet and Reichardt

Equation Slope (m) Intercept

hyd-1Lippert–Mataga mL − M =16015 −32.281Bakhshiev mB =6349.6 −624.95Kawski–Chamma–Viallet mK − C − V =13327 36062Reichardt mR =18213 573.63

hyd-2Lippert–Mataga mL − M =3903.3 3915.7Bakhshiev mB =1282 3984.2Kawski–Chamma–Viallet mK − C − V =6527.1 26872Reichardt mR =10811 2538.1

hyd-3Lippert–Mataga mL − M =3270.5 3858.5Bakhshiev mB =1113.2 3910.3Kawski–Chamma–Viallet mK − C − V =3639.1 28289Reichardt mR =5089.9 1656.6

n is number of solvents.

based on the spin polarized DFT in the GGA as implemented in theSIESTA code [33]. We used Perdew–Burke–Ernzerhof [34] GGAfunctional. Electronic wavefunctions were expanded to a double-ζbasis set augmented by polarization orbitals. The interaction betweenthe core and valence electrons was handled by Troullier–Martinsnorm-conserving pseudopotentials [35] in their fully separable form[36]. The geometry optimizations in the conjugate-gradient algorithmwere continued until all force components are less than 0.01 eV/Ǻ.Our GGA calculations show that electronic structure is not spin polar-ized for studied compounds.

2.4. Onsager cavity radius

The value of Onsager cavity radiuses (a0) of hyd-1, hyd-2 and hyd-3derivatives is calculated from the following equation [23],

a0 ¼ 3M4πdNA

� �1=3ð16Þ

where d is the density of solutemolecule,M themolecular weight of thesolute molecule and NA is Avagadro's number. Densities and molecularweights are d = 1.108 (g/cm3) and M = 212.247 (g/mol) for hyd-1, d = 1.414 (g/cm3) and M = 291.69 (g/mol) for hyd-2, and d =1.228 (g/cm3) and M = 246.692 (g/mol) for hyd-3, respectively.Thus, a0 is found to be 4.3214 Å, 4.4295 Å and 4.3905 Å for hyd-1,hyd-2 and hyd-3, respectively.

3. Results and discussions

3.1. Solvent effects on the absorption and fluorescence spectra

Steady state absorption and fluorescence spectra of hyd-1, hyd-2and hyd-3 in different solvents are given in Figs. 2 and 3. Absorption,emission maximum wavelengths and wavenumbers along with Stokesshift values are listed in Tables 1–4, respectively. Stokes shift does notregularly change with the change of solvent polarity for hyd-1, hyd-2and hyd-3. The largest Stokes shifts are observed in acetone, tetrahydro-furan and chloroform for hyd-1, hyd-2 and hyd-3 as 7355, 5906 and6407 cm−1 respectively (see Tables 2–4).

UV–vis spectra of the studied compounds display two bands. Band(A) centered around 300 nm are assigned to π–π* electronic transitionsdue to delocalization in aromatic rings. Band (B) (in the range of320–351 nm for hyd-1, 342–427 nm for hyd-2 and 348.5–367 nmfor hyd-3) also corresponds to π–π* electronic transitions whichare born out from the conjugation between \C_N\N bridge. It isobserved from the absorption spectra that hyd-2 and hyd-3 undergo

correlations of the studied compounds.

Correlation (R2) Solvents used in correlation n

0.9105 9, 10, 12, 13, 14, 15 60.9031 9, 10, 12, 13, 14 50.9317 9, 10, 11, 12, 13 50.9003 2, 5, 6, 7, 11 5

0.9109 Except for 1, 5, 8, 13 110.9058 Except for 1, 5, 8, 13 110.9065 Except for 1, 2, 5, 15 110.9087 2, 3, 5, 6, 7, 8 6

0.9687 2,,6, 7, 9, 10, 11, 12, 13 80.9536 2,,6, 7, 9, 10, 11, 12, 13 80.9030 6, 7, 9, 10, 11, 12, 13, 15 80.9105 9, 10, 12, 14, 15 5

Table 6Solvent parameters and solvent polarity functions.

No Solvent ε n FL − M(ε, n)a FB(ε, n)b FK − C − W(ε, n)c ETNd

1 s-Hexane 1.88 1.3749 −0.0014 −0.0025 0.2538 0.0092 1,4-Dioxane 2.21 1.4224 0.0205 0.0415 0.3692 0.1643 Toluene 2.38 1.4969 0.0132 0.0291 0.4055 0.0994 Diethylether 4.34 1.3520 0.1672 0.3776 0.4284 0.1175 Chloroform 4.81 1.4459 0.1483 0.3709 0.5474 0.2596 Ethyl acetate 6.02 1.3724 0.1996 0.4891 0.5642 0.2287 THF 7.58 1.4072 0.2096 0.5491 0.6143 0.2078 Dichloromethane 8.93 1.4242 0.2171 0.5902 0.5829 0.3089 1-Butanol 17.51 1.3993 0.2635 0.7504 0.7104 0.60210 2-Propanol 19.92 1.3772 0.2762 0.7787 0.7118 0.54011 Acetone 20.56 1.3587 0.2841 0.7894 0.6389 0.35412 Ethanol 24.55 1.3614 0.2887 0.8129 0.7198 0.65413 Methanol 32.66 1.3284 0.3086 0.8546 0.7216 0.76214 DMF 36.71 1.4305 0.2744 0.8356 0.7709 0.40415 DMSO 46.45 1.4793 0.2630 0.8400 0.8010 0.444

a Lippert–Mataga solvent function (Eq. (7)).b Bakhshiev solvent function (Eq. (8)).c Kawski–Chamma–Viallet solvent function (Eq. (9)).d Reichardt solvent parameter values taken from Ref. [29].

Table 7Onsager cavity radius, ground state and excited state dipole moments (in Debye).

Onsager radius ‘a’ (Å) μga μe(L − M)b μe(B)c μe(K − C − V)

d μe(R)e (μe/μg)f

hyd-1 4.3214 3.9330 15.3014 11.0913 11.0913 10.5796 2.8200hyd-2 4.4295 6.8279 12.6523 10.1658 10.1659 12.1421 1.4889hyd-3 4.3905 3.4827 8.7438 6.5521 6.5520 7.0809 1.8812

1 D = 3.33564 × 10−30 C·m = 10−18 esu.cm.a Calculated according to Eq. (10).b Calculated according to L–M correlation, Eq. (4).c Calculated according to B correlation, Eq. (5).d Calculated according to K–C–V correlation, Eq. (6).e Calculated according to R correlation Eq. (14).f Calculated according to Eq. (12).

391İ. Sıdır et al. / Journal of Molecular Liquids 197 (2014) 386–394

bathochromic shift with an increase of solvent polarity, whereasabsorption bands of hyd-1 are not sensitive to solvent polarity change.

Investigated hydrazone derivatives show one emission band underexcitation with 303 nm wavelength for hyd-1, 372 nm for hyd-2 and

O

NN

H

O

N

HN

H

Enol form

O-quinoid form

H

O

NN

H

HKeto form-3

R1

R1

R1

RR2

R2

R2

R

R

Fig. 5. Possible tautomeric resonance s

311 nm for hyd-3, respectively. Emission bands of hyd-1 and hyd-3tend to hypsochromic shift with the increase of solvent polarity, whereashyd-2 suffers bathochromic shift while increasing solvent polarity. Thelarge Stokes shift of the emission bands observed in aprotic solvent can

O

NN

Keto form-1

Keto form-2

O

NH

N

H

O

N

HN

H

Zwitterionic form

H

H

H

R1

R1

R1

2

2

2

tructure of hydrazone derivative.

(a) (b)

(c) (d)

(e) (f)

Fig. 6.Dipolemoment andHOMO–LUMOgap as a function of the external electric field calculated by generalized gradient approximation (GGA) for hyd-1, hyd-2 and hyd-3 (a) and (b) forhyd-1, (c) and (d) for hyd-2, (e) and (f) for hyd-3, respectively.

392 İ. Sıdır et al. / Journal of Molecular Liquids 197 (2014) 386–394

be ascribed as an excited state intramolecular proton transfer. As can beseen from Fig. 4, solvent accessible surfaces (SAS) indicate active interac-tion sites with solvent. Interaction of lone pairs of\OH substituent withthe solvent and formation of intermolecular and intramolecular O\H_Nhydrogen bonding between hydroxyl group and nitrogen atom give riseto charge transfer. Additionally, Cl atoms were located at meta positionin hyd-2 and hyd-3 behavior as mesomerically electron donating intomedium. As can be seen from Table 1, the presence of Cl atom in hyd-3resulted with bigger absorption and fluorescence emission wavelengthsin all of the solvents, except for n-hexane, compared to that of hyd-1.Inductive electron withdrawing NO2 group, located at para position inhyd-2, gives rise to stronger charge transfer and then bathochromicallyshift of absorption and fluorescence bands compared to that of hyd-1and hyd-3 by twisting under excitation. But, NO2 effect is stronger thanthat of Cl.

3.2. Estimation of ground and excited state dipole moments

In order to determine the ground state and excited state dipolemoments of hyd-1, hyd-2 and hyd-3, we firstly apply Eqs. (1)–(3) and(15) based on the solvatochromic shift methods. Slopes (m), interceptsand correlation coefficients obtained from the plot of eνa−eν f andeνa þ eν f� �

=2 versus to solvent polarity function F(ε, n) and solventpolarity parameter ETN by using Lippert–Mataga, Bakhshiev, Kawski–Chamma–Viallet and Reichardt equations are given in Table 5. eνa−eν f

and eνa þ eν f� �

=2 values and solvent functions and parameters are alsogiven in Tables 2–4 and 6, respectively. As can be seen from Table 5,correlation coefficients are larger than 0.9003 in most cases whichindicate a good linearity for these correlations.

Dipole moments of the ground state (μg) are determined from theslopes mK–C–V and mB of the Kawski–Chamma–Viallet and Bakhshiev

2-dyh1-dyh hyd-3 (a)

(b)

(c)

(a)

(b)

(c)

(a)

(b)

(c)

Fig. 7. Density of states (DOS) versus energy and HOMO, LUMO plots calculated by generalized gradient approximation (GGA) for hyd-1, hyd-2 and hyd-3.

Negative Positive

(a)

(b)

(c)

Fig. 8.Molecular electrostatic potential (MEP) of the studiedα-hydroxy phenyl hydrazonederivatives calculated by B3LYP/6-311 + G(d) level of theory.

393İ. Sıdır et al. / Journal of Molecular Liquids 197 (2014) 386–394

correlations by applying Eq. (10). The excited state dipolemoments (μe)are also determined from slopes (mL–M,mB,mK–C–V andmENT

) of Lippert–Mataga, Bakhshiev, Kawski–Chamma–Viallet andReichardt correlationsby applying Eqs. (4)–(6) and (14). All of the results are presented inTable 7.

As presented in Table 7, the ground state dipole moment (μg)ofhyd-2 (6.8279 D) is found as larger than those of hyd-1 (3.9330 D)and hyd-3 (3.4827 D) due to the charge located on NO2 group. Chlorineatom located in para position of hyd-3 gives rise to relatively smallerdipole moment compared to that of hyd-1.

Excited state dipole moment is obtained to be higher than groundstate dipole moment for all of the studied molecules. The differencesbetween ground and excited state dipole moments are in the range of11.3684–6.6466 D for hyd-1, 5.8244–3.3379 D for hyd-2 and 5.2611–3.0693 D for hyd-3 which indicates that studied hydrazone derivativesare significantly more polar in their excited state than in their groundstate. The structure of studied compounds consists of pi-donor-piaromatic system. Solvent–solute interactions are expected to bestronger in the excited statewith the results of redistribution of chargesbetween two electronic states. Excited state dipole moments obtainedby using Lippert–Mataga, Bakhshiev and Kawski–Chamma–Vialletcorrelations show good agreement. It is noticed that Δμ calculatedfrom Lippert–Mataga method is relatively larger compared to valuesobtained by the other methods, since it does not consider polarizabilityeffect of the solute. Discrepancies between ground and excited statedipole moment can be explained as the results of the nature ofemitting state, charge transfer occurring under excitation andsubstituent effect. Direction of ground state dipole moment can beseen in Fig. 1.

The change in dipole moment can be explained in terms ofpossible resonance structures of the compounds (Fig. 5). Theseresonance structures arise out of the delocalization of π-electronswith the interactions by the way of enol-keto tautomerism andformation of ionic structure.

394 İ. Sıdır et al. / Journal of Molecular Liquids 197 (2014) 386–394

3.3. Electric field effect on dipole moment and HOMO–LUMO gap

Electron transport characteristics of a molecule are mainly controlledby the nature of the molecular orbitals. The spatial distribution and theenergy level of molecular orbital give information about the conductivity[37–39]. The variations of HOMO–LUMO gap (HLG) versus the externalelectric field (EF) in the x, y, z-directions are depicted in Fig. 6a, c, and e.HLG does not show significant change with the increase of applyingelectric EF. However, applied EF in the x- and xyz-directions gives riseto exponentially reducing HLG for hyd-1 and hyd-3. For the zero field,the HLG is 2.5002 eV for hyd-1 and 2.4050 eV for hyd-3, as the fieldincreases the gap reduces to 2.2965 eV for hyd-1 and 2.2536 eV forhyd-3 while EF is 0.20 V/Å. This indicates that when the EF increases,HOMO and LUMO energy levels approach to each other. hyd-2moleculesinduced by EF increase its HLG as EF reaches to 0.15 V/Å. Beyond thispoint, increase of EF gives rise to reduce of HLG. For zero field, the HLGof hyd-2 is 2.0801 eV; for 0.15 V/Å HLG increases to 2.3100 eV; and for0.20 V/Å HLG reduces to 2.2478 eV. This behavior can be attributed tothe nature of NO2 group located at para position in hyd-2.

The applied EFs (0.0–0.20 V/Å) induce polarization in the moleculesas a consequence, dipole moments of molecules change linearly andexponentially. Fig. 6b, d, and f shows total molecular dipole momentversus applied EFs in different directions. When Ex, Ey and Ez are applied,dipole moments increase linearly for all of the compounds. When EF isapplied in three directions (Ex,y,z), it is observed that dipole momentexponentially increases for hyd-1 and hyd-3 whereas it decreasesexponentially for hyd-2. For the zerofield, dipolemoments are calculatedas 2.8103 D for hyd-1, 5.4798 D for hyd-2 and 2.9738 D for hyd-3 in xyz-direction. As the field increases to 0.20 V/Å, dipolemoments of hyd-1 andhyd-3 increase to 4.6545 D and 5.9636 D, respectively whereas dipolemoment of hyd-2 reduces to 1.6924 D. Interestingly applied EF in xyz-directions forces to hyd-2 being in uniform charge distribution andresulted as decreasing in polarization. Therefore, hyd-2 exhibits smalldipole moment with the increase of EF.

3.4. Density of states (DOS) and molecular electrostatic potential (MEP)

Density of states versus energy plots for zero EF and HOMO, LUMOplots calculated by GGA method is shown in Fig. 7. Dotted lines in DOSplots indicate Fermi Level (FL). As can be seen from Fig. 7, the HOMOis localized over entire molecule except for nitrophenyl in hyd-2. TheLUMO shows that orbitals migrate to phenol and CHNNH bridge inhyd-1, to chlorophenol and CHNNH bridge in hyd-3 while molecularorbitals are localized on nitrophenyl and CHN group in hyd-2.

The MEP is a plot of electrostatic potential drawn on the basis of theconstant electron density surface. It is a descriptor for determiningnegative and positive regions of a molecule. The negative (red) regionsof MEP were related to electrophilic reactivity and the positive (blue)regions to nucleophilic reactivity (Fig. 8). As can be seen from the MEPsurface, the negative regions are mainly localized around aromaticrings and oxygen atoms. The regions having positive potential areover the nitrogen and hydrogen atoms.

4. Conclusions

In this study, we have determined the ground and excited state di-pole moments of some hydrazone derivatives by using differentsolvatochromic shift methods. The excited state dipole moments arefound as larger than ground state dipole moments. This reveals thathyd-1, hyd-2 and hyd-3 are more polar in the excited state than thosein the ground state. Increasing electric field in xyz-direction appreciablydecreases the dipole moment in hyd-2 which forces the molecule to bein uniform charge distribution due to inductive electron withdrawingeffect of NO2 group. However, with the increase of electric field,HOMO–LUMO gap of hyd-2 increases. Considering the HOMO–LUMOgap and dipole moment changes under applied external electric field,

it canbe said that even thoughhyd-2has small HLG, there is no possibilityof conduction and therefore almost it acts as an insulator, whereas hyd-1and hyd-3 act as conductors. These observations give an insight on thiskind of insulator and conductor which can be a candidate for using thedesign of electronic devices.

Acknowledgment

This study is supported by Bitlis Eren University, Scientific andTechnological Application and Research Center.

References

[1] S. Rollas, S.G. Küçükgüzel, Molecules 12 (8) (2007) 1910–1939.[2] D.S. Kalinowski, D.R. Richardson, Pharmacol. Rev. 57 (4) (2005) 547–583.[3] L.R. Morgan, K. Thangaraj, B. LeBlanc, A. Rodgers, L.T. Wolford, C.L. Hooper, D. Fan,

B.S. Jursic, J. Med. Chem. 46 (21) (2003) 4552–4563.[4] L.R. Morgan, B.S. Jursic, C.L. Hooper, D.M. Neumann, K. Thangaraj, B. LeBlanc, Bioorg.

Med. Chem. Lett. 12 (23) (2002) 3407–3411.[5] S. Sagiraju, B.S. Jursic, Carbohydr. Res. 343 (7) (2008) 1180–1190.[6] Y.J. Alvarado, J. Caldera-Luzardo, G. Ferrer-Amado, V. Manzilla-Labarca, E.

Michelena, J. Solution Chem. 36 (1) (2007) 1–11.[7] F. Hollósy, T. Lóránd, L. Örfi, D. Erös, G. Kéri, M. Idei, J. Liq. Chromatogr. Related

Technol. 25 (7) (2002) 1129–1143.[8] R. Maccari, R. Ottana, M.G. Vigorita, Bioorg. Med. Chem. Lett. 15 (2005) 2509.[9] Y. Alvarado, M. Álverz-Mon, J. Baricelli, J. Caldera-Luzardo, N. Cubillán, G. Ferrer-

Amado, M. Hassanhi, Y. Marrero-Ponce, V. Mancilla, M. Rocafull, M. San Antonio-Sánchez, J. Ojeda-Andara, L. Thomas, J Solution Chem. 39 (2010) 1099–1112.

[10] N.C. Santos, J. Figueira-Coelho, J. Martins-Silva, C. Saldanha, Biochem. Pharmacol. 65(2003) 1035–1041.

[11] M. Shah, P. Patel, H. Parekh, Orient. J. Chem. 18 (2002) 159–167.[12] A. Rajasekaran, S. Murugesan, J. Indian Chem. Soc. 79 (2002) 544–545.[13] S.A. EI Hawash, A.E. Abdel Wahab, M.A. EI Demellawy, Arch. Pharm. 339 (2006)

14–23.[14] N. Fujii, J.P. Mallari, E.J. Hansell, Z. Macky, P. Doyle, M.Y. Zhou, J. Gut, P.J. Rosenthal, J.

H. Mckerrow, R.K. Guy, Bioorg. Med. Chem. Lett. 15 (2005) 121–123.[15] D. Lebrecht, A. Geist, A. Ketelsen, U.-P. Haberstroh, J. Setzer, B. Kratz, Int. J. Cancer

120 (2007) 927–934.[16] S.A.E. I-Hawash, A.E. Abdel Wahab, ChemInform 37 (2006) 19–26.[17] M. Bakir, K. Abdur-Rashid, Transit. Met. Chem 24 (1999) 384–388.[18] S. Vijayakumar, A. Adhikari, B. Kalluraya, K.N. Sharafudeen, K. Chandrasekharan, J.

Appl. Polym. Sci. 119 (2011) 595–601.[19] Na Li, Yu Xiang, Xiaotong Chen, Aijun Tong, Talanta 79 (2009) 327–332.[20] K. Choi, J.-K. Choi, G.-S. Yoo, Arch. Pharm. Res. 17 (1994) 231–235.[21] Xiaotong Chen, Zifan Li, Yu Xiang, Aijun Tong, Tetrahedron Lett. 49 (2008)

4697–4710.[22] J. Tomczak, K. Dobek, J. Lumin. 129 (2009) 884–891.[23] L. Bilot, A. Kawski, Z. Naturforsch. 17a (1962) 621–627.[24] A. Kawski, in: J.F. Rabek (Ed.), Progress in photochemistry and photophysics, vol. 5,

CRC Press, Boca Raton, USA, 1992, pp. 1–47.[25] E. Lippert, Z. Naturforsch. 10a (1955) 541–545.[26] A. Chamma, P. Viallet, C. R. Acad. Sci. Paris, Ser. C 270 (1970) 1901–1904.[27] C. Reichard, Chem. Rev. 94 (1994) 2319–2358.[28] Y. Fenar, Anilin ve Hidrazin Türevi Schiff Bazlarının Sentezi, Yapılarının

Aydınlatılması ve Farklı Çözücülerde Solvatokromik Özelliklerinin UV–vis veFloresans Spektroskopisi ile Tayini, Lisans Tezi Anadolu Üniversitesi, Fen Fakültesi,Kimya Bölümü, Eskişehir, 2011.

[29] C. Reichardt, Solvents and Solvent Effects in Organic Chemistry, VCH, New York, 2005.[30] D.R. Lide (Ed.), Handbook Chemistry and Physics, 76th ed., CRC Press, Boca Raton,

Florida, 1995.[31] A.D. Becke, J. Chem. Phys. 98 (1993) 5648–5653.[32] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, G.

Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg, M. Hada, M. Ehara,K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H.Nakai, T. Vreven, J.A. Montgomery Jr., J.E. Peralta, F. Ogliaro, M. Bearpark, J.J. Heyd,E. Brothers, K.N. Kudin, V.N. Staroverov, R. Kobayashi, J. Normand, K.Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J.M.Millam, M. Klene, J.E. Knox, 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, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth, P. Salvador, J.J.Dannenberg, S. Dapprich, A.D. Daniels, . Farkas, J.B. Foresman, J.V. Ortiz, J.Cioslowski, D.J. Fox, Gaussian 09, Revision A.1, Gaussian, Inc., Wallingford CT, 2009.

[33] J.M. Soler, E. Artacho, J.D. Gale, A. García, J. Junquera, P. Ordejón, D. Sánchez-Portal, J.Phys. Condens. Matter 14 (2002) 2745.

[34] J.P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett. 77 (1996) 3865–3868.[35] N. Troullier, J.L. Martins, Phys. Rev. B 43 (1991) 1993–2006.[36] L. Kleinman, D.M. Bylander, Phys. Rev. Lett. 48 (1982) 1425–1428.[37] J.M. Seminario, L. Yan, J. Quantum Chem. 102 (2005) 711–723.[38] J.M. Seminario, C. De La Cruz, P.A. Derosa, L. Yan, J. Phys. Chem. B 108 (2004)

17879–17885.[39] M. Jothi, P. Kumaradhas, Comput. Theor. Chem. 1000 (2012) 10–18.