Finding suitable and simple sensors for detecting dangerous chemical compounds in environment and workplace is an important subject in nowdays life. Organic volatile compounds are useful compounds at the same time dangerous which their detection is one of the attractive aims in the field of sensor for scientists. One of important class ofmaterials for sensing is vapochromic inorganic complexes. These complexes facing with vapor of volatile compound such as organic solvents change color. Due to the importance of vapochromic inorganic complexes in the detection of volatile organic compounds, in recent years much attention has been paid to synthesis of this kind of complexes. In this thesis, the vapochromism behavior of a Pd(II) complex with mono-anionic piroxicam ligand ( trans -[Pd(pir)2]) in the presence of the vapors of materials such as water (H2O), phenol (C6H5OH), ethanol (C2H5OH), methanol (CH3OH), acetaldehyde (CH3CHO), formaldehyde (H2CO) and acetone (CH3COCH3) was studied, theoretically using density functional theory (DFT) method. The structure of the complex taken from the X-ray crystallography was used for the calculations. The absorption spectra were calculated using the time-dependent DFT (TD-DFT) method. The B3PW91 functional along with the SDD effective pseudo potential for Pd atom and D95V basis for the other atoms were used in the calculations. Also, the atoms in molecules (AIM) analysis was performed to investigate the strength of the hydrogen bonds between the complex and vapor molecules. It was observed that the hydrogen bonds between the molecules with the S=O and C=O groups of piroxicam ligand are stronger than the other sites in the complex. The analysis of the absorption spectra with natural bonding orbital (NBO) calculations showed that the change in the position of the ? ? ?* of ligand in the structure of complex is responsible for the color change of complex. The theoretical results showed that this change depends on the kind ofvapor and this complex can be used as a sensor for the detection of vapor of materials selected in this work.
