Synthesis, crystal structure, spectroscopic investigations and DFT calculations of the copper(II) complex of 4-(Trifluoromethyl)pyridine-2-carboxylic acid

Accepted Manuscript Synthesis, crystal structure, spectroscopic investigations and DFT calculations of the copper(II) complex of 4-(Trifluoromethyl)pyridine-2-carboxylic acid

Hatice Vural, Metin Orbay PII:

S0022-2860(17)30837-2

DOI:

10.1016/j.molstruc.2017.06.056

Reference:

MOLSTR 23942

To appear in:

Journal of Molecular Structure

Received Date:

14 February 2017

Revised Date:

04 June 2017

Accepted Date:

05 June 2017

Please cite this article as: Hatice Vural, Metin Orbay, Synthesis, crystal structure, spectroscopic investigations and DFT calculations of the copper(II) complex of 4-(Trifluoromethyl)pyridine-2carboxylic acid, Journal of Molecular Structure (2017), doi: 10.1016/j.molstruc.2017.06.056

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ACCEPTED MANUSCRIPT Synthesis, crystal structure, spectroscopic investigations and DFT calculations of the copper(II) complex of 4-(Trifluoromethyl)pyridine-2-carboxylic acid Hatice VURAL1*, Metin ORBAY2 1Department

of Electrical and Electronics Engineering, Faculty of Technology, Amasya University, 05100, Amasya, Turkey 2Department

of Science Education, Faculty of Education, Amasya University, 05100, Amasya,

Turkey ABSTRACT A novel polymeric complex of Cu(II) ion, [Cu(tfpc)2]n [tfpc: 4-(Trifluoromethyl)pyridine2-carboxylate] has been prepared and characterized spectroscopically (by FT-IR) and structurally (by single-crystal XRD). The geometry around the Cu(II) center can be described as square planar made by tfpc ligand having nitrogen and oxygen atoms. Additionally, the Cu(II) complex has a one-dimensional double-bridged polymeric structure in which Cu(II) ions are bridged by two oxygen atoms of adjacent planes. The crystal packing has been stabilized by C–H∙∙O intra and intermolecular hydrogen bonds. The molecular structure of the Cu(II) complex has been optimized using the Density Functional Theory (DFT) B3LYP, B3PW91 and PBEPBE levels with 6-311G +(d, p) basis set. The calculated electronic spectra have been explained using the time dependent DFT (TD-DFT) method by applying the polarized continuum model (PCM). The vibrational spectral data have been calculated and compared with experimental ones. The nonlinear optical (NLO) properties of the title compound have been investigated using the DFT method with three different levels. Natural Bond Orbital (NBO) property of the Cu(II) complex has been performed by the B3LYP density functional and the 6-311G +(d, p) basis set. Keywords: Copper (II) complex; FT-IR, DFT; NLO; NBO *Corresponding author. E-mail address: [email protected] (H.Vural).

ACCEPTED MANUSCRIPT

1. Introduction Pyridine-2-carboxylic acid (picolinic acid) has been extensively studied due to its magnetic, structural, medicinal and biological properties [1-9]. Picolinic acid plays an important role in the absorption of zinc [10] and has neuro-protective, immunological and antiproliferative effects within the body [4, 5]. The multifunctional ligands containing N and O-donors such as picolinic acid are of great interests since they are significant from the industrial point of view; for instance, in nuclear reactor decontamination [11, 12]. Transition metal complexes with picolinic acids can demonstrate fully varying coordination behavior, functioning as one, two or more dentate coordination, counter-ions, bridging ligand [13, 14]. The coordination number and structure of the metal-picolinate complexes are important owing to their varied biological and physicochemical properties such as antimicrobial activities and photo luminescent behavior [15-17]. In recent years, the Density Functional Theory (DFT) method has become a widely used in calculations of molecular properties that include stability structure, charge distribution, and vibrational frequencies. The advancement of ever better exchange-correlation functional has made it possible to calculate many physicochemical properties with accuracies comparable to those of traditionally correlated ab initio methods [18]. As the literature survey reveals neither quantum chemical calculations nor an experimental study of the complex of the copper (II) ion with the 4-(Trifluoromethyl)pyridine-2-carboxylic acid has been reported so far. The aim of our study is to investigate the quantum chemical properties of the title complex, using the DFT method with 6-311G+(d, p) basis set. Therefore, in the present study, we report the synthesis, structural and spectroscopic characterization of Cu(II) complex of 4-(Trifluoromethyl)pyridine-2-carboxylate ligand as well as the computational studies. The optimized geometry, vibrational frequencies, and non-linear

ACCEPTED MANUSCRIPT optical (NLO) parameters were calculated by means of DFT (B3LYP, B3PW91 and PBEPBE) methods with 6-311G +(d, p) basis set. The frontier molecular orbital (HOMO and LUMO) energies and natural bond orbitals (NBO) were investigated by using the DFT/B3LYP employing the 6-311G+(d, p) basis set by applying the polarized continuum model (PCM). 2.

Experimental

2.1 Instrumentation The IR spectrum of the title molecule was recorded in the range of 4000 – 400 cm-1 using a Perkin-Elmer FTIR spectrometer using KBr disc. 2.2. Crystal Structure Determination The diffraction data were measured on a Bruker D8 QUEST image plate detector using Mo Kα radiation (λ = 0.71073 Å, T = 296 K). The structure was solved by direct-methods using SHELXS-97 [19]. Full-matrix least-squares refinement on F2 was carried out using SHELXL-97 [19]. All hydrogen atoms attached to carbon atoms were positioned geometrically and refined by a riding model with Uiso 1.2 times that of attached atoms and remaining hydrogen atoms were located from the Fourier difference map (Table 1). The molecular drawing was obtained using DIAMOND 3.0 (demonstrated version) [20]. 2.3. Synthesis 4-(Trifluoromethyl)pyridine-2-carboxylic acid (Htfpc) was purchased from SigmaAldrich Company with a stated purity 97%. An aqueous solution of Cu(Cl)2 (1 mmol, 0.13g) in water (20 ml) was added to a solution of 4-(Trifluoromethyl)pyridine-2-carboxylic acid (1 mmol, 0.19g) in methanol (20 ml) under stirring at room temperature in a 1:1 M ratio for 1 h. Blue

ACCEPTED MANUSCRIPT crystals of the title compound that are stable in air were obtained by filtration of the result solution. 3.

Computational Details The title compound was subjected to the B3LYP [21], PBEPBE (generalized-gradient-

approximation exchange-correlation functional of Perdew, Burke, and Ernzerhof) [22] and B3PW91 (B3LYP combined with gradient-corrected correlational functional of Perdew and Wang (PW91)) [23, 24] levels of DFT calculations to obtain the optimized geometrical parameters and vibrational frequencies. All calculations were performed using GAUSSIAN 09W [25] software package and GAUSSIAN VIEW 5.0 molecular visualization program [26]. In the compound, the copper (II) ion has one unpaired electron, so unrestricted hybrid functional B3LYP, PBEPBE and B3PW91with 6-311G+ (d, p) basis set were used for an open-shell electronic structure. The vibrational frequencies of the Cu(II) compound were calculated using the DFT method with three different levels. No imaginary frequencies were found, indicating that the stationary points correspond to a true energy minimum. The electronic properties of the title complex were investigated using the TD-DFT /B3LYP method starting from the ground-state geometry optimized. DFT (B3LYP, B3PW91 and, PBEPBE) methods with 6-311G +(d, p) basis set were also used to calculate the polarizability, dipole moment and first hyperpolarizability. The NBO calculation was performed at the B3LYP level by means of the NBO 9.5 program.

ACCEPTED MANUSCRIPT 4. Result and Discussion 4.1.

Description of the crystal structure A Diamond view of [Cu(tfpc)2]n complex with the atom-numbering scheme is presented in

Figure 1. The centrosymmetric one-dimensional double-bridged polymeric structure of the title compound is illustrated in Figure 2. Some important structural parameters are summarized in Table 2. The XRD results show that the Cu(II) ion is coordinated by two planar tfpc ligands’ nitrogen and oxygen atoms in trans position. This arrangement causes the formation of a square planar configuration. In polymeric structure, the each Cu(II) centers is placed in a distorted octahedral environment, in which the axial sites are made up by carbonyl oxygen atoms of two neighboring [Cu(tfpc)2] complexes. The axial Cu-O interactions are made to compare the values with those reported in the literature [27, 28]. In octahedral environment, the axial bond distances (Cu–O= 2.776–2.736 Å) are longer than the basal plane bonds (Cu–O= 1.922-1.961 Å) for polymeric structure due to Jahn-Teller (JT) effect [29-31]. The Cu-O(1.922-1.961 Å) and Cu–N (1.968-1.969 Å) bond lengths are in good agreement with the related square planar Cu(II) complexes reported for [Cu(3Me-pic)2]n [3Me-pic =3-methylpicolinic acid][Cu-O = 1.9397(14) Ǻ; Cu-N = 1.9611(17) Ǻ] [29], [Cu(pic)2]n [pic = pyridine-2-carboxylate][Cu-O = 1.953(9) Ǻ; Cu-N = 1.966(14) Ǻ] [27], Cu(PC)2 .H2O[PC=pyridine-2-carboxylate] [Cu-O = 1.941(2) Ǻ; Cu-N = 1.960(2) Ǻ] [32]. The C1–C7 and C3-C6 bond lengths are substantially longer than aromatic C–C bond lengths [33]. Packing analysis of the molecule indicates that there are intra and intermolecular C–H∙∙∙O hydrogen bonds (see Table 3), linking the molecules of the single unit to form a one-dimensional chain along the a axis (Fig. 2). The face to face π-π stacking interaction of the molecule occurs

ACCEPTED MANUSCRIPT between pyridine rings situating in adjacent mirror planes [defined by C5/C4/C3/C2/C1/N1]. The distance between the ring centroids is 5.109 Ǻ. 4.2 Geometry optimization The geometry of the Cu(II) complex has been optimized in a double state by the DFT method with unrestricted hybrid density functional B3LYP, B3PW91 and PBEPBE/6-311G +(d, p). The calculated geometric parameters of the copper complex for the three different levels have been compared with the experimental ones in Table 2. The B3LYP hybrid functional predicts the Cu-O and Cu-N lengths in good agreement with experimentally values than B3PW91 and PBEPBE levels. The orientation of the pyridine ring in the carboxylate groups is defined by the torsion angle C2-C1-C7-O2 [171.3(19)o] for the X-ray structure. This value has been computed at 179.9o for the three different levels. According to XRD result, the dihedral angle between the least-squares planes of the pyridine rings is 1o, while this angle has been calculated at 0.01o, 0.02o and, 0.02o for the three different levels, respectively. The B3LYP and B3PW91 hybrid schemes show better performance to calculate the bond lengths and angle values than PBEPBE. The optimized parameters are in good agreement with the XRD results.

4.3 FT-IR Spectroscopy Figure 3 illustrates the experimental and calculated infrared spectra of the Cu(II) complex in the frequency range from 4000 to 400 cm-1. These spectra have been calculated by using B3LYP, PBEPBE and B3PW91 levels with 6-311G + (d, p) basis set. The calculated frequencies have been scaled with 0.96 for B3LYP, 0.98 for PBEPBE and, 0.95 for B3PW91 [34-37]. Some selected experimental and computed IR bands of the Cu(II) complex are compared in Table 4.

ACCEPTED MANUSCRIPT The FT-IR spectra of the title compound show a distinct peak in the 3106 cm-1 due to symmetric stretching vibrations of the v(CH). The weak band at 2962 cm-1 belonging to v(CH) asymmetric stretching vibrations of the Cu(II) complex. The DFT calculations reproduce v(CH) stretching vibrations around 3090-3070 cm-1 for B3LYP level, 3066-3045cm-1 for B3PW9 level and 3087-3079cm-1 for PBEPBE level. The experimental symmetric and asymmetric v(CH) stretching peaks for the 4-(Trifluoromethyl)pyridine-2-carboxylic acid were appeared at 3095 cm1

and 2821 cm-1, respectively. Therefore, it can be said that the v(CH) vibrations of the Cu(II)

complex have some red shifts compared to 4-(Trifluoromethyl)pyridine-2-carboxylic acid. According to Table 4, the bands at 1655cm-1 and 1307 cm-1 correspond to the symmetric and asymmetric ν(COO-) stretching vibrations of the title complex and theoretically, these bands are computed at 1678-1281 cm-1 for B3LYP level, 1684-1283cm-1 for B3PW91 level and 16441264cm-1 for PBEPBE level. The appeared band at 1700 cm-1 was assigned to the ν(COO-) stretching vibration of 4-(Trifluoromethyl)pyridine-2-carboxylic acid. The difference between the symmetric and asymmetric ν(COO-) of the Cu(II) complex is 348 cm-1, indicating the presence of monodentate type coordination [38]. These calculated results are in good agreement with FT-IR results. The ν(CN) vibration of the title compound is appeared at 1258 cm-1, while the peak appears at 1330 cm-1 in 4-(Trifluoromethyl)pyridine-2-carboxylic acid. The computed bands at 1251, 1267 and 1289 cm-1 are assigned to v(CN) vibrations for the three different levels, respectively. The experimental ν(CF) vibration is observed at 1111 cm-1 in the FT-IR spectrum. The calculated peaks at 1112, 1114 and 1088 cm-1 are assigned to v(CF) vibrations for B3LYP, B3PW91 and PBEPBE levels, respectively. The calculated results are consistent with experimental data. The band at 1036 cm-1 in IR spectrum is assigned to ring breathing mode of the title complex. The ring breathing mode of the pyridine ring in the Cu(II) complex appears at higher values

ACCEPTED MANUSCRIPT compared to pyridine and substituted pyridines (995 cm−1) [39-44]. The peak at 1008 cm-1 corresponds to ring breathing mode of 4-(Trifluoromethyl)pyridine-2-carboxylic acid, indicating that this ligand is coordinated to Cu(II) ion. The calculated value of the mode for B3LYP level is a good agreement with FT-IR result. The (CH) in-plane bending vibration is observed at 1160 and 1079 cm-1 experimentally, and calculated using DFT methods at 1133 cm-1, 1079 cm-1 for B3LYP, 1133 cm-1, 1072 cm-1 for B3PW91 and 1207 cm-1, 1068 cm-1 for PBEPBE. The out-of-plane (CH) bending vibration of the compound is found at 924 cm-1 experimentally, calculated at 973 cm-1, 961 cm-1 and 949 cm-1 for the three different levels, respectively. Hence, the DFT-calculated frequencies are consistent with experimental values.

4.4 Electronic Properties The Uv-visible spectrum of the Cu(II) complex has been calculated by using the DFT/ B3LYP/6-311G +(d, p). The electronic excitation energies, electronic absorption wavelengths (λ), oscillator strengths have been computed using the TD-DFT with polarized continuum model (PCM). The major contributions for the electronic transitions have been performed using the Swizard program [45]. The spectrum and important transitions have been visualized by means of Chemissian program http//:www.chemissian.com (Fig.4). According to the DFT/ B3LYP 6-311G +(d, p) results, the calculated Uv-vis spectrum contains two important absorption bands to be 333 nm and 309 nm (Fig.4). The band at 333 nm with an oscillator strength of f= 0.0548 corresponds to the transition of HOMO to LUMO with 97% contributions. The peak computed at 309 nm with an oscillator strength of f= 0.0992 is originated from the contribution of HOMO-6 → LUMO (93%). In the molecule, HOMO (98%),

ACCEPTED MANUSCRIPT HOMO-1 (%99), HOMO-2 (%81), HOMO-4 (%99), LUMO (%79) and LUMO+1 (%92) orbitals are localized on tfpc ligand. The HOMO (Highest Occupied Molecular Orbital) and the LUMO (Lowest Unoccupied Molecular Orbital) are called frontier molecular orbitals (FMOs). Since β-MOs play active role in the electronic transitions, only the β spin part is taken into account for FMOs. Figure 4 illustrates the FMOs and energies. The energy gap between FMOs is a critical parameter in determining chemical reactivity of the molecule such as hardness, softness chemical potential, and electronegativity. The ionization potential (IP) and electron affinity (EA) are given by IP = – EHOMO and EA = –ELUMO. As can be seen from Table 5, the ionization potential (IP) and electron affinity (EA) of the compound computed by B3LYP/6-311G+(d, p) method are 7.916 eV and 3.340 eV, respectively. The chemical hardness (η), softness (s) and, electronegativity () are formalized to (IP-EA)/2, 1/2η and, (I+A)/2, respectively. Hard materials have a large energy gap and soft materials have a small energy gap. Therefore, hard molecules are not more polarizable than the soft molecules. The energy gap and η value are calculated as 4.576 eV and 2.288 eV for B3LYP/ 6-311G +(d, p) level. 4.5. Natural Bond Orbital (NBO) Analysis The NBO calculation of the Cu(II) complex has been performed using NBO 5.9 program implemented in the Gaussian 09W package at the B3LYP/6-311G +(d, p) density functional. The result of NBO analysis gives that the electron arrangement of Cu (II) ion is [core] 4s0.30 3d9.31 4p0.29 4d0.01 with + 1.0814 natural charge. It concluded that the tfpc ligands coordinate to the 3d, 4s and 4p orbits of the Cu(II) atom. Charges on all atoms have been calculated from natural population analysis (NPA). The charge on the copper atom is smaller than formal charge +2 indicates that the charge transfer from the tfpc ligands to the Cu (II) ion. The most negative

ACCEPTED MANUSCRIPT charges are ascribed coordinated oxygen atoms (-0.753) in the title complex. The charge on C1 and C6 atoms are +1.0687, indicating that the substituent effect. The total electrons (17.99692 core, 9.90252 valance, and 0.01342 Rydberg electrons) of the Cu (II) ion are 27.91286. The NBO approach is an efficient tool for understanding delocalization of electron density from filled Lewis-type (donor) NBOs to properly empty non-Lewis type (acceptor) NBOs, which corresponds to a stabilizing donor-acceptor interaction [46]. The strength of interaction between Cu(II) ion and active binding sites can be estimated from the stabilization energy (the second order interaction energy) (E2). As shown in Table 6, the second order interaction energies (E(2)) LP(3)O2→LP*(6)Cu1, LP(1)N1→LP*(6)Cu1, LP(1)N1→LP*(5)Cu1 and LP(3)O2→LP*(5)Cu1 are calculated as 23.10, 22.10, 18.73 and 17.71 kcalmol-1, respectively. These results show that tfpc ligands through N and O atoms bind to the Cu(II) ion. In the title complex, the higher interaction

energies

are

electron

donating

from

LP(1)C4→BD*(2)N1-C5

and

LP(1)C1→BD*(2)N1-C5 orbitals lead to stabilization energy of 57.95 kcal/mol and 37.95 kcal/mol, respectively. 4.6 Nonlinear Optics Nonlinear optical (NLO) materials are especially interesting because of their potential applications in the field of optoelectronic such as optical communication, optical computing, optical switching, optical modulation, optical logic, and dynamic image processing [47]. DFT has been frequently used as an effective computational tool to investigate the NLO materials [18]. The molecular electronic dipole moment (μ), the total polarizability ( hyperpolarizability (





) and the first

) of the Cu(II) complex have been calculated by the DFT method with

three different hybrid functional, and the obtained results have been converted into electrostatic units (esu) (α: 1 a.u.=0.148 x10-24 esu and β: 1 a.u.= 8.639 10-33 esu).

ACCEPTED MANUSCRIPT Urea is one of the prototypical molecules used in the study of the NLO properties of molecular systems. In this work, urea was chosen as a reference molecule; because there were not experimental values about the title molecule in the literature. As can be seen from Table 7, the μ and



values are found to be 0.082 Debye and 32.424

respectively. Calculated values of the μ,



and,



×

10-24 esu for DFT/B3LYP level,

with B3PW91 and PBEPBE levels are

considerably different from B3LYP hybrid functional. The calculated



value is equal 0.839

×

10-32 esu for B3LYP. When it is compared to the 4-(Trifluoromethyl)pyridine-2-carboxylic acid, the calculated value of



of the Cu(II) complex is smaller than that of 4-

(Trifluoromethyl)pyridine-2-carboxylic acid (2.11

×

10-30 esu calculated with the B3LYP/6-

311G +(d, p)). The title complex cannot be used as efficient NLO materials due to the presence of inversion symmetry [48]. But, the



value is comparable with urea [49].

5. Conclusions A new polymeric copper(II) complex with 4-(Trifluoromethyl)pyridine-2-carboxylate ligand has been synthesized and characterized by FT-IR and single crystal X-ray diffraction. The geometry optimization and vibrational frequencies of the Cu(II) complex have been evaluated by using DFT method with B3LYP, B3PW91 and PBEPBE levels. The geometric parameters obtained by the three different levels with 6-311G + (d, p) basis set are in well agreement with that from X-Ray data. The calculated infrared intensities of the Cu(II) complex have been compared with the obtained by FT-IR. The theoretical results show good agreement with experimental data. The electronic transition of the molecule in

the gas phase exhibit the

maximum absorption band at 333 nm attributed to HOMO→LUMO (97%) transition. The energy gap and chemical hardness (η) has been calculated by using B3LYP/ 6-311G +(d, p) level, and it

ACCEPTED MANUSCRIPT is shown that the Cu(II) complex is a hard complex. NBO analysis also suggests that the higher interaction energy is electron donating from LP(1)C4→BD*(2)N1-C5 leads to stabilization energy of 57.95 kcal/mol.

Acknowledgement This work was supported by Amasya University Research Fun for financial support through Project number FMB-BAP 16-0170. The authors thank the Amasya University Scientific Research Projects Unit for financial support. The authors acknowledge Scientific and Technological Research Application and Research Center, Sinop University, Turkey, for the use of the Bruker D8 QUEST diffractometer. Appendix A. Supplementary material Crystallographic data (excluding structure factors) for the structure in this paper have been deposited with the Cambridge Crystallographic Data Centre as the supplementary publication no CCDC 1510267 for complex. Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge, CB12 1EZ, UK, fax: +44 1223 366 033, e-mail: [email protected] or on the web www: http:// www.ccdc.cam.ac.uk.

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ACCEPTED MANUSCRIPT Table 1 Crystal data and structure refinement for the Cu(II) complex. formula

C14H6CuF6 N2O4

formula weight (g)

443.76

temperature (K)

293 K

wavelength (Mo Å)

0.7107

crystal system

Triclinic

space group

P1

unit cell dimensions a, b, c (Å)

5(4), 6(5), 12(9)

α,β,γ (˚)

103(2), 94(3), 93(2)

volume (Å3)

349.06

Z

1

calculated density (mg m-3)

2.111

μ (mm-1)

1.67

F(0,0,0)

219

crystal size (mm)

0.15 × 0.11 × 0.09

θ ranges (˚)

3.5-28.4

index ranges

-6≤ h ≤6 -7≤ k ≤7 -14≤ l ≤14

reflections collected

15104

independent reflections

2874[R(int)=0.031]

reflection observed (> 2σ)

2823

absorption correction

Multi-scan

refinement method

full-matrix least-squares on F2

data/restrains/parameters

2874/3/245

goodness-of-fit on F2

1.1

final R indices [I˃2σ(I)]

0.025

R indices (all data)

0.063

largest diff. peak and hole (e Å -3)

0.28 and -0.32

ACCEPTED MANUSCRIPT Table 2 Selected structural parameters by X-ray and theoretical calculations for the Cu(II) compound. Exp.

B3LYP

PBEPBE

B3PW91

N1—Cu1

2.0(11)

1.99

1.97

1.98

N1A—Cu1

2.0(11)

1.99

1.97

1.98

O1—Cu1

1.9(10)

1.93

1.95

1.92

O1A—Cu1

2.0(10)

1.93

1.95

1.92

O1—C7

1.3(6)

1.29

1.30

1.29

N1—C1

1.3(7)

1.32

1.35

1.34

N1—C5

1.3(9)

1.33

1.34

1.33

C1—C2

1.4(9)

1.39

1.39

1.39

C2—C3

1.4(9)

1.39

1.39

1.39

C3—C4

1.4(8)

1.39

1.40

1.39

C4—C5

1.4(7)

1.39

1.39

1.39

C1—C7

1.5(10)

1.52

1.52

1.52

C3—C6

1.5(8)

1.51

1.51

1.51

Bond angles (°) N1-Cu1-N1A

179.4(3)

179.987

179.992

179.990

O1-Cu1-O1A

178.8(7)

179.989

179.998

179.997

O1-Cu1-N1

83(10)

83.687

84.844

83.910

O1A-Cu1-N1

96(10)

96.318

96.157

96.091

O1-Cu1-N1A

96(10)

96.307

96.155

96.089

O1A-Cu1-N1A

85(10)

82.688

83.844

83.910

Bond length (Ǻ)

ACCEPTED MANUSCRIPT Table 3 Hydrogen bonding interactions for the Cu(II) complex. Hydrogen-bond geometry (Å,˚) D—H···A

D—H

H···A

D···A

D—H···A

C4—H4···O1i

0.90

2.37

3(3)

129

C5—H5···O2A

0.91

2.59

3(3)

115

C4A—H10···O1Aii

0.90

2.43

3(3)

126

Symmetry code: (i) -1+x,-1+y, z; (ii) x, 1+-y, z.

ACCEPTED MANUSCRIPT

Table 4 Comparison of the observed and calculated vibrational frequencies of the title complex. B3LYP

B3PW91

PBEPBE

Scaled (cm-1)

Scaled (cm-1)

Scaled (cm-1)

3095

3090

3066

3087

2962

2821

3070

3045

3079

υ(CO)

1655

1700

1678

1684

1644

υ(CO)

1620

1686

1693

1647

υ(CO)

1307

1173

1281

1283

1264

υ(CC)R

1569

1571

1589

1588

1574

1538

1540

1525

1330

1251

1267

1289

1262

1222

1242

1236

1133

1133

1207

1218

1216

1263

1112

1114

1088

Assignments

Exp.

Htfpc[18]

υ(CH)R

3106

υ(CH)R

υ(CC)R υ(CN)R

1258

β(CH)R β(CH)R

1160

υ(CF)

1177

υ(CF)

1111

β(CH)R

1079

1081

1079

1072

1068

Ring breathing

1036

1008

1008

997

996

γ(CH)R

924

924

973

961

949

γ(Ring)

882

875

846

836

894

υs(CF3)

794

860

763

753

735

1148

R:Pyridine ring; υ: stretching; β: in-plane bending; γ: out-of-plane bending.

ACCEPTED MANUSCRIPT

Table 5 The frontier molecular orbital energies and related properties for the Cu(II) complex Parameters (eV) EHOMO ELUMO ΔE = ELUMO-EHOMO I = -EHOMO A = -ELUMO χ = (I+A)/2 η = (I-A)/2 S = 1/2η

B3LYP/6-311G+(d, p) -7.916 -3.340 4.576 7.916 3.340 5.628 2.288 1.144

ACCEPTED MANUSCRIPT Table 6 Second-order perturbation theory analysis of the Fock matrix in NBO basis. Acceptor orbital(j)a

Donor orbital(i)

E(2) (kcalmol-1)b

εj-εi (a.u.)c

Fij(a.u.)d

LP(1) N1

LP*(5)Cu1

18.73

0.19

0.085

LP(1) N1

LP*(6)Cu1

22.10

0.52

0.137

LP(1) N1

LP*(8)Cu1

14.19

1.02

0.160

LP(3) O2

LP*(5)Cu1

17.71

0.22

0.088

LP(3) O2

LP*(6)Cu1

23.10

0.55

0.143

LP(3) O2

LP*(7)Cu1

16.04

0.91

0.161

LP(1) C4

BD*(2)N1-C5

57.95

0.10

0.119

LP(1) C4

BD*(2)C2-C3

32.23

0.14

0.107

LP*(1) C1

BD*(2)N1-C5

37.95

0.11

0.098

LP*(1) C1

BD*(2)C2-C3

32.07

0.14

0.108

LP(2) O2

BD*(2)C7-O1

35.83

0.29

0.130

aBD*,antibonding

orbital; LP,lonepair.

bSecond

order interaction energy (stabilization energy)

cEnergy

difference between donor and acceptor i and j NBO orbitals

dF ij

is Fock matrix element between i and j NBO orbitals

Table 7 Total dipole moment(  ), the mean polarizability ( hyperpolarizability (





) and the mean first

) of the Cu(II) complex.

Property

B3LYP

B3PW91

PBEPBE

x

-0.0002 Debye -0.0082 Debye

-0.0002 Debye -0.0006 Debye

-0.0001 Debye -0.0003 Debye

-0.0001 Debye 0.082 Debye 206.9359826 a.u. 217.6688929 a.u.

-0.0005 Debye 0.0008 Debye 203.258322 a.u. 214.297504 a.u.

-0.0003 Debye 0.0005 Debye 235.163596 a.u. 235.386155 a.u.



231.7590034 a.u. 218.79 a.u.

228.297504 a.u. 215.48 a.u.

267.229853 a.u. 245.93 a.u.



32.424 × 10-24 esu

31.934 × 10-24 esu

36.446 × 10-24 esu

x

0.744 a.u. 0.524 a.u

0.015 a.u. 0.068 a.u

-0.056 a.u. 0.101 a.u

-0.337 a.u. 0.839 × 10-32 esu

-0.104 a.u. 0.108 × 10-32 esu

-0.089 a.u. 0.126 × 10-32 esu

y z



x y z

y z



ACCEPTED MANUSCRIPT

Figure 1 Cu(II) coordination environment in the complex, showing the atom-numbering scheme.

Figure 2 (a) One-dimensional double-bridged polymeric structure of the title complex, (b) packing diagram.

ACCEPTED MANUSCRIPT

Figure 3 Experimental and calculated FT-IR spectra of the [Cu(tfpc)2]n complex.

Oscillator strength

ACCEPTED MANUSCRIPT

TD/CIS spectrum

0.12 0.1 0.08 0.06 0.04 0.02 1

1.5

2

2.5

3 3.5 Wavelength, eV

Energy (eV)

LUMO (-2.100 eV)

HOMO (-7.495 eV)

2 1.5 1 0.5 0 -0.5 -1 -1.5 -2 -2.5 -3 -3.5 -4 -4.5 -5 -5.5 -6 -6.5 -7 -7.5 -8 -8.5 -9 -9.5 -10 -10.5 -11 -11.5 -12

4

4.5

5

5.5

Molecular Orbitals

333 nm

α spin MOs

309 nm

β spin MOs

Figure 4 The energies of the FMOs for the title molecule and the electronic transitions obtained at B3LYP/6-311G+(d, p) level.

ACCEPTED MANUSCRIPT Highlights 

A

novel

polymeric

copper(II)

complex,

[Cu(tfpc)2]n

[tfpc:

4-

(Trifluoromethyl)pyridine-2-carboxylate] was synthesized. 

The geometry of the Cu(II) complex was optimized DFT (B3LYP, B3PW91 and PBEPBE) methods with 6-311G +(d, p) basis set.



Fourier transform infrared (FT-IR) spectrum was collected, and the data was compared with the computed spectra.



Electronic properties of the molecule were investigated.



NBO and NLO analysis for the title compound were carried out.