Tayyibe Bardakçı, Mustafa Kumru, and Ahmet Altun İstanbul/Turkey QUANTUM CHEMICAL STUDIES ON THE PREDICTION OF STRUCTURES, CHARGE DISTRIBUTIONS AND VIBRATIONAL SPECTRA OF SOME Ni(II), Zn(II), AND Cd(II) IODIDE COMPLEXES Tayyibe Bardakçı, Mustafa Kumru, and Ahmet Altun İstanbul/Turkey International Symposium on Molecular Spectroscopy 71ST MEETING - JUNE 20-24, 2016 - CHAMPAIGN-URBANA, ILLINOIS

Outline Introduction Computations Results Conclusion Molecular Structures Mulliken, NBO and APT Charge Analysis Vibrational Analysis Conclusion

Introduction In this study;

Why anilines? Introduction Aniline and its derivatives are widely used in: electro-optical and microelectronic devices such as diodes and transistors, intermediate in the production of dyes, pharmaceuticals, ligands in coordination chemistry.

Why transition metal complexes? Introduction Why transition metal complexes? A transition metal complex consists of a transition metal coordinated to one or more ligands. Good in catalysis, materials synthesis, photochemistry, and biological systems. Display diverse chemical, optical and magnetic properties. Effective in combining with other elements. So, their related complexes have a variety of applications such as killing certain types of cancer cells previously immune to other kinds of cancer drugs.

Complex Geometries Introduction The geometry of a transition metal complex is determined by the number of ligands bonded to the metal atom.

Computations Quantum chemical calculations were carried out with Gaussian 03 software package on our linux server cluster. The structures and normal modes were visualized by Gausview. Calculations were performed in the gas phase at B3LYP/def2-TZVP level. Def2-TZVP basis set was downloaded from EMSL Basis Set Library, and used with GEN keyword in Gaussian 03. Effective core potentials (ECP) were used within the def2-TZVP.

Molecular Structures Mulliken, NBO and APT Charge Analysis Vibrational Analysis

Molecular structures of the free ligands Results Molecular structures of the free ligands Mean absolute errors (MAE) and linear correlation coefficient (R2) values: Bond lengths: 0.015 and 0.984 for p-toludine & 0.016 and 0.983 for m-toluidine. Bond angles: 1.164 and 0.926 for p-toluidine & 1.300 and 0.913 for m-toluidine. Optimized molecular geometries of the ligands p-toluidine and m-toluidine, and the related twenty transition metal complexes have been obtained in the gas phase at B3LYP/def2-TZVP level using Gaussian 03 program package.

Molecular structures of the metal iodide complexes of p-toluidine Results Molecular structures of the metal iodide complexes of p-toluidine For the Ni complex, Ni(II) ion in the complex was found monomeric distorted octahedral in the UV-Vis study performed by Altun et al. [22]. On the other hand Engelter et al. [19] states the polymeric octahedral coordination of Ni(II) complexes according to the color and magnetic moments. Being consistent with the Engelter’s results, in our calculations we also predict the structure of Ni complex as distorted polymeric octahedral. The density functional calculations predict the molecular structures of Zn and Cd complexes as distorted tetrahedral, being in agreement with the previous experimental and theoretical study on these complexes Distorted tetrahedral Distorted polymeric octahedral

Some geometry parameters of the metal iodide complexes of p-toluidine Results Some geometry parameters of the metal iodide complexes of p-toluidine B3LYP/def2-TZVP level predicts: C-N bond length in free p-toluidine: 1.397Å H-N-H angle in free p-toluidine: 111.9o

Molecular structures of the metal iodide complexes of m-toluidine Results Molecular structures of the metal iodide complexes of m-toluidine Distorted tetrahedral Distorted polymeric octahedral

Some geometry parameters of the metal iodide complexes of m-toluidine Results Some geometry parameters of the metal iodide complexes of m-toluidine B3LYP/def2-TZVP level predicts: C-N bond length in free m-toluidine: 1.394Å H-N-H angle in free m-toluidine: 112.2o

Charge Distributions Results Mulliken, natural bond orbital (NBO), and atomic polar tensor (APT) charge analyses are performed for all compounds. Mulliken is one of the traditional and most widely used methods. But, it is basis set dependent and thus have weaknesses in predicting inaccurate results at some basis sets. Natural charges provided by the NBO method are based on the investigation of the atomic and molecular orbitals and mostly give good results, having no basis set dependency. APT charges are based on the parametrization of the experimental infrared intensities, and can be directly obtained from default vibrational frequency calculations. If the observed infrared frequencies are consistent with the computed frequencies, mostly APT charge results are also accurate. Computations of atomic charges and spins are important since they are directly related with the molecular structures and properties of the compounds. However accurate calculations on charge distributions are challenging.

Charge distribution of the free ligands Results Charge distribution of the free ligands Nitrogen atom is found to be most negative in all methods, and C4 of p-toluidine and C3 of m-toluidine which are bonded with nitrogen atom found to have positive charges as expected. In free ligands, charge distributions are mostly in agreement with three of the methods, having small differences.

Results Charge distribution of the Ni(II) iodide complexes of p-toluidine and m-toluidine

Results Charge distribution of the Cd(II) iodide complexes of p-toluidine and m-toluidine

Results Charge distribution of the Zn(II) iodide complexes of p-toluidine and m-toluidine In our computations, physically most meaningful results are obtained with APT method. Despite of the shortcomings of Mulliken analysis, results of the Mulliken are also quite well, having accordance with the APT charges. Therefore, for the metal iodide complexes of p-toluidine and m-toluidine NBO charge analysis results are not trustworthy.

Charge Results Results In our previous studies, we have also calculated some metal bromide complexes. Different from the metal bromide complexes, we have obtained inaccurate results for charge distributions of metal iodide complexes in the NBO analysis. The reason for this may be iodine is heavier than bromine, and located in the lower part of the periodic table having large number of core electrons. Since effective core potential (ECP) is used for the iodine containing systems at def2-TZVP level, it may be affected our natural charge distribution results negatively. Bunu sözlü olarak söyle, slayttan çıkar.

VIBRATIONAL FREQUENCIES Results VIBRATIONAL FREQUENCIES As an evidence of complex formation between metal halides and ligands some modes originating from ligand show substantial shifts in the spectra of complexes. Amino group frequencies of the ligands are generally more affected from the coordination, which shows the complex formation occurs via nitrogen atom of the free ligand.

Results Vibrational Frequencies of the Metal Iodide Complexes of P-toluidine Asymmetric and symmetric υNH band of free ligand is lowered in the complexes. CH stretching vibrations are not affected from coordination. Drastic changes are observed in the vibrational bands of in the NH2 wagging and twisting vibrations when compared with free ligand. Although some ligand vibrations (10 of total 45) are also observed below 600 cm-1, metal modes are the remarkable vibrational bands of this region.

Results Vibrational Frequencies of the Metal Iodide Complexes of M-toluidine Asymmetric and symmetric υNH band of free ligand is lowered in the complexes. CH stretching vibrations are not affected from coordination. Drastic changes are observed in the vibrational bands of in the NH2 wagging and twisting vibrations when compared with free ligand. Although some ligand vibrations (10 of total 45) are also observed below 600 cm-1, metal modes are the remarkable vibrational bands of this region.

A systematic DFT study on different transition metal complexes have been performed and molecular structures, charge, spin distributions and vibrational frequencies of these complexes are elucidated. Significant results are summarized below.

1. Molecular Structures Conclusions Zinc and cadmium complexes are found to have distorted tetrahedral structures. Nickel complexes have octahedral coordination around the Ni atom, by sharing two I atoms of the neighboring complexes.

2. Charge Analysis Conclusions NBO results are not reliable for our metal iodide complexes. In terms of having physically most meaningful results, APT method is more trustworthy by showing the most positive charges on metal atoms, and the most negative charges on the nitrogen atoms and halogens. 1- That is, natural charge results fail in heavy atoms at B3LYP/def2-TZVP level. Most probably pseudopotential/ECP which is utilized in this basis set for the heavy atoms caused this unfavourable result. 2- Therefore, it can be said that,

3. Vibrational Analysis Conclusions As an evidence of complex formation between metal (II) halides and the ligands, amino group frequencies shift lower or higher wavenumbers, which show coordination occurs via nitrogen atom of the free ligands. In the vibrational spectra of experimental only studies some assignments were not determined correctly. However, we provide a full vibrational assignment of the title complexes for the first time, by means of density functional calculations.

Density functional theory finds a good compromise in terms of accuracy and the computational cost. However, for the vibrational frequencies the results might be better, especially above 1700 cm-1. The development of the new functionals and basis sets for the transition metal complexes is essential as well as providing background information for different systems with the available functionals and basis sets. The results of the present study will be able to serve as a reference for future theoretical studies, which allows molecular dynamics simulation of transition metal complexes or transition metal based drugs.

Our Related Articles Tayyibe Bardakçı, Mustafa Kumru, Ahmet Altun, “Molecular structures, charge distributions, and vibrational analyses of the tetracoordinate Cu(II), Zn(II), Cd(II), and Hg(II) bromide complexes of p-toluidine investigated by density functional theory in comparison with experiments.”, Journal of Molecular Structure, Vol. 1116, pp. 292-302, 2016. Tayyibe Bardakçı, Ahmet Altun, Kurtuluş Gölcük, Mustafa Kumru “Synthesis, structural, spectral (FT-IR, FT-Ra and UV-Vis), thermal and density functional studies on p-methylaniline complexes of Mn(II), Co(II), and Ni(II) bromides”, Journal of Molecular Structure, Vol. 1100, pp.475-485, 2015. Mustafa Kumru, Tayyibe Bardakçı, Sadık Güner, "DFT calculations and experimental FT-IR, dispersive-Raman and EPR spectral studies of Copper (II) chloride complex with 3-amino-1-methylbenzene", Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Vol. 123, pp.187-193, 2014. Tayyibe Bardakçı, Mustafa Kumru, Sadık Güner, "Molecular structure, vibrational and EPR spectra of Cu(II) chloride complex of 4-amino-1-methylbenzene combined with quantum chemical calculations", Journal of Molecular Structure, Vol. 1054-1055, pp.76-82, 2013.

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