Theoretical study of the ir spectra of 3-chloropyridine and 3-chloropyridine metal complexes

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Abstract

The vibrational spectrum of 3-chloropyridine was calculated on the basis of normal coordinate analysis. Quantum optimized (MNDO) geometry was used for spectral calculations. The refined force field and electro-optical parameters are found to reproduce well experimental IR spectrum of liquid 3-chloropyridine. The coordination effect on the ligand vibrational modes was also investigated. The calculated results indicate the presence of some alterations on the ring force field of the molecule in complex formation.

Introduction

In our previous studies [1] we reported a complete calculation of vibrational spectra (wavenumbers and IR absorption intensities) of free and coordinated 2-chloropyridine and discussed the effect of coordination, through the nitrogen lone pairs to a transition metal, on the vibrational wavenumbers and electro-optical parameters of the molecule. We are now reporting the results of calculation of the IR spectrum of 3-chloropyridine (3Clpy) in valance force field approximation. Coordination effect on the 3-chloropyridine has also been investigated. Our aim is to investigate position of substituent dependent alterations of the force field and electro-optical parameters (EOP) of free and coordinated chloropyridines. We shall be reporting our calculation results on 4-chloropyridine in a future publication.

Section snippets

Methods of calculation

The IR spectral properties of 3Clpy were calculated by using LEV [2] program. The program includes procedures for vibrational frequencies and IR intensities calculation, force field and electro-optical parameters (EOP) refinement, quantum chemistry (semiempirical) molecular geometry optimization and calculation of force constants with respect to the natural internal coordinates and many other features. The methods implemented in the program were described in details in [3]. The experimental

Free 3Clpy

The geometrical parameters and definition of natural vibrational coordinates of 3Clpy molecule are given inTable 1. The numeration of atoms and the direction of bond vectors in 3Clpy molecule are shown inFig. 1.

The result of normal coordinate analysis is given inTable 2. The experimental wavenumbers taken from Green et al. [7] are also tabulated for comparison. The assignments were established by the analysis of experimental spectra. Our theoretical calculation completely agrees with the

Acknowledgements

One of us (SA) thanks The Research Fund of The University of Istanbul through the Project number: 956/090597.

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