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Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 165 (2016) 3346
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Spectrochimica Acta Part A: Molecular and BiomolecularSpectroscopy
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Conformational, electronic, and spectroscopic characterization ofisophthalic acid (monomer and dimer structures) experimentallyand by DFT
F. Bardak a, C. Karaca b, S. Bilgili a, A. Atac a, T. Mavis a, A.M. Asiri c,d, M. Karabacak e,, E. Kose aa Department of Physics, Celal Bayar University, Manisa, Turkeyb Experimental Science Applications and Research Center, Celal Bayar University, Manisa, Turkeyc Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabiad Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabiae Departmant of Mechatronics Engineering, H.F.T. Technology Faculty, Celal Bayar University, Turgutlu, Manisa, Turkey
http://dx.doi.org/10.1016/j.saa.2016.03.0501386-1425/ 2016 Elsevier B.V. All rights reserved.
a b s t r a c ta r t i c l e i n f o
Article history:Received 5 December 2014Received in revised form 28 March 2016Accepted 30 March 2016Available online 5 April 2016
Isophthalic acid (C6H4(CO2H)2) is a noteworthy organic compoundwidely used in coating and synthesis of resinsand the production of commercially important polymers such as drink plastic bottles. The effects of isophthalicacid (IPA) on human health, toxicology, and biodegradability are the main focus of many researchers. Becausestructural and spectroscopic investigation of molecules provides a deep understanding of interactional behaviorsof compounds, this study stands for exploring those features. Therefore, the spectroscopic, structural, electronic,and thermodynamical properties of IPA were thoroughly studied in this work experimentally using UVVis, 1Hand 13C NMR, FT-IR, FT-Raman and theoretically via DFT and TD-DFT calculations. The UVVis absorption spec-trum in water was taken in the region 200400 nm. The NMR chemical shifts (1H and 13C) were recorded inDMSO solution. The infrared and Raman spectra of the solid IPA were recorded in the range of 4000400 cm1
and 350050 cm1, respectively. DFT and TD-DFT calculations were performed at the level of B3LYP/6311++G(d,p) in determination of geometrical structure, electronic structure analysis and normal mode. The13C and 1H nuclear magnetic resonance (NMR) spectra were estimated by using the gauge-invariant atomicorbital (GIAO) method. The scaled quantum mechanics (SQM) method was used to determine the total energydistribution (TED) to assign the vibrational modes accurately. Weak interactions such as hydrogen bondingand Van der Walls were analyzed via reduced density gradient (RDG) analysis in monomeric and dimericforms. Furthermore, the excitation energies, density of state (DOS) diagram, thermodynamical properties,molecular electro-static potential (MEP), and nonlinear optical (NLO) properties were obtained.
2016 Elsevier B.V. All rights reserved.
Keywords:Isophthalic acidDFTNMR and UVVis spectraVibrational spectraDOS and MEP
Isophthalic acid/ortho-phthalic acid (1.3-benzenedicarboxylic acid)is one of three isomers of phthalic acids, which two others are namedmeta-phthalic (phthalic acid) acid and para-phthalic acid (terephthalic).It is a colorless solid organic compound that plays an important role asprecursors to commercially polymers, e.g. the fire-resistant materialNomex. IPA is also used in the production of resins for drink bottleswhen mixed with terephthalic acid. The high performance polymerpolybenzimidazole (PBI), for instance, is manufactured from isophthalicacid .
There are numerous studies on synthesis and production of poly-mers and coordination complexes based on IPA and its isomers. Thefollowing studies summarize the ongoing research on the IPA and IPA
based ligands. The adsorption behavior and structure of phthalic acidand benzoic acid on the gold surface with combination of SERS andDFT calculation methods have been presented by Gao et al. . Hwanget al. has investigated the adsorption of IPA at the hematite/water inter-face using batch adsorption experiments and ATR-FTIR spectroscopy. FT-IR and Raman spectra of dimethylterephthalate as microcrystal-line powder have been reported by semi empirical and ab initio calcula-tions . The molecular conformations, vibrational and electronicanalysis of 2-aminoterephthalic acid derivative terephthalic acid ofisophthalic acid isomer were examined using experimental techniqueand density functional theory calculations . Many functional IPA-based and derivate coordination polymers were synthesized and struc-tural and photoluminescence behaviors were explored because of theirbeing good candidates for the construction of coordination polymers aseries of 1D, 2D and 3D coordination polymers. . Yang et al. reportedthat syntheses and crystal structures of two coordination polymersusing hydroxylation of isophthalic acid in the hydrothermal reaction
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34 F. Bardak et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 165 (2016) 3346
of Cu II-isophthalate system . The synthesis and characterization ofpoly-benzobisthiazoles derived from halogenated phthalic acid andisophthalic acid were studied by Saxena et al. . The complexes ofisophthalic acid also were prepared and identified by elemental analy-sis, IR spectroscopy and X-ray single-crystal diffraction . Solubilitiesof terephthalaldehydic, p-toluic, benzoic, terephthalic, and isophthalicacids inN,N-dimethylformamidewere reported as a function of temper-ature in the temperature range 294.75370.45 K using a laser monitor-ing observation technique . IPA and trimesic acid on Au (111) singlecrystals and on Au(11125 nm) quasi-single crystalline film electrodesin 0.1 M HClO4 were investigated via infrared reflection absorptionspectroscopy (SEIRAS) and scanning tunneling microscopy (STM)with cyclic voltammetry . Hamilton et al. showed that linked bis-isophthalic acid derivatives form ordered molecular structures in thesolid state . They also reported the design and synthesis of a novelisophthalic acid derived organogelator . IPA-based mesogenic di-mers were synthesized and structural effects on mesophase propertieswere examined .
The works above show that the IPA and its isomers are widely usedin the synthesis of new coordination compounds and polymer systems,and the structure of the compound plays a significant role in all process-es. Although there has been some works that describe the crystal struc-tures of phthalic acid, isophthalic acid, terephthalic acid, and biphenyl-3,3,5,5-tetracarboxylic acids presented by several groups , tothe best of our knowledge, there has not been any quantum chemicalcalculations or experimental study to report the conformational, inter-actional, magnetic, and electronic features of IPA. Thus, we broughtwide range of spectroscopic techniques (UVVis, 1H and 13C NMR, FT-IR and Raman spectra) together to describe these characteristics of IPAwith the support from DFT calculations. We used a favorite and cost-effective approach, the gradient corrected density functional theory(DFT)  with the Becke's three-parameter hybrid functional (B3) for the exchange part and the LeeYangParr (LYP) correlationfunction , in Gaussian 09 packet program . Theoretical calcula-tions significantly enrich the accessible knowledge about the moleculesuch as nonlinear optical properties and thermodynamical features atvery large temperature range, and help to visualize and quantify manykey properties like weak interactions and potential energy surfaces.Appropriately chosen methods and basis set combinations give prettywell matching results with experimental observations as shown inthis studywith DFT-B3LYP/6-311G++(d,p) for calculations of geomet-rical and vibrational properties, TD-DFT/B3LYP/6-311G++(d,p) forelectronic properties, and GIAO-B3LYP/6-311G++(d,p) for magneticfeatures, all generating appreciable results.
The rest of the paper is organized as follows; experimental detailsare presented in Experimental details section. The computationalmethod is given in Computational details section. The experimentaland simulation results for monomer and dimer structural, electronicproperties, chemical shifts and vibrational features, thermodynamicproperties for the title molecule considered in this study are presentedand discussed in the section of Results and discussion. We have alsocompared the simulation results with the observed data in the sameSection. Finally, the summary of our main results are given in the lastsection.
2. Experimental details
IPA molecule is supplied from Across Organics Company in solidstate with a purity of 99% and used without any further purification.UVVis (200400 nm) spectrum in water was recorded by usingShimadzu UV-2101 PC, UV\\VIS recording Spectrometer. NMR (1Hand 13C) spectra were obtained in Varian Infinity Plus spectrometer at300 K, in DMSO. The NMR chemical shifts are reported in ppm relativeto tetramethylsilane (TMS). FT-IR (4000400 cm1) spectrum is re-corded in Perkin-Elmer FT-IR System Spectrum BX spectrometer byusing a KBr disc technique with a scanning speed of 10 cm1 min1
and the spectral resolution of 4.0 cm1. FT-Raman (350010 cm1)spectrum of the title molecule is recorded in Bruker RFS 100/S FT-Raman instrument using 1064 nm excitation from an Nd:YAG laserwith a liquid nitrogen co