Investigation On The Complex Of The Pyridine And Lodine Applying Ultraviolet-visible Spectrum Method

Infrared spectrum, ultraviolet spectrum, nuclear magnetic resonance spectrum and mass spectroscopy in the molecular spectrum rise to important function towards studying the properties of the complexes. The ultraviolet spectrum is dissimilar with the infrared spectrum, its spectral shape is simple, and absorption peak is broad and zonal. But absorption peaks of the infrared spectrum are more acuater and numbers are more. The infrared spectrum not only can reflect the existence of the function regiment, but also have something to do with structure of the whole molecule. Ultraviolet spectrum mainly reflects the property of the not saturated regiment, it not only can identify the not saturated system, reflect the interaction and the space effect of the electrons in the molecules. But also can measure the content of the not saturated compound, because demand the amount of sample little which is usually milligram class or tiny gram classes, so little composition of measurement, an organic compound in the living creature body is particularly more beneficial. Ultraviolet-visible spectrum is that electrons from lower level transition to higher level come into being spectrum after absorbing ultraviolet-visible light. From the ultraviolet spectrum can acquire the existence of total yoke system in the relevant molecule, the length of the total yoke chain and replacement group upon the influence of the distinctive regiment etc. thus for inorganic compounds and organic compounds carry on qualitative authentication or quantitive measurement to provide a kind of powerful tool. Forming complex be called the charge transfer complex (CTC) when the function of charge transfer occur between molecule and ion possessing configuration of two closed shell. Component that can provide the electrons is entitled donor when form CTC. But accept electron is called acceptor. When donor and acceptor interact and become the complex, according to the molecular orbit theories, absorbing light for occupancy orbit of the donor tallest energy level electrons can jump to move to be empty orbit of the acceptor, so the charge transfer transition also is regarded as the complex or molecular inside redox process. We can make full use of the physical property to be change suddenly to judge the formation of new complex. These physical properties including the melting point, vapor pressure, viscidity, surface tension , dielectric constant, refractive index and conduct electricity rate etc. we can study the structure of complex by various technique such as the nuclear magnetic resonance, X-ray, infrared absorption spectrum, Raman spectrum, magnetic moment and dipole moment measurement etc. The ultraviolet-visible spectrum which studies the complex is a simple but fast method. it is an importance application of the ultraviolet-visible spectrum method to investigate the complex; it can measure the structure of complex. It not only can study the colored complex and also can study colorless complex. And can study a pair of complex, and then study three group complex; since can study the reaction that make single complex and make the dissimilarity coordination number complex at the same time. This thesis applying the ultraviolet-visible spectrum method studies spectrum properties of the charge transfer spectrum of pyridine and iodine and" blue move" spectrum of iodine. The iodine is in" purple" solvent such as heptane, carbon tetrachloride, the biggest absorption waveband is at 520 nm the iodine steam did not change; But in" brown" solvent such as benzene, pyridine, this waveband make ambulation of short-wave, and in the short-wave particularly inthe ultraviolet area, appear the very intensive absorption, this kind of obvious variety illustrate appearing a new absorption peak, as a result indicate that form the new complex. When we complex iodine aqua with pyridine aqua of the different density, the aqua color is changed gradually the golden color into the pale red color with the increment of the density of pyridine, indicating that both took place compound. The peak value of the heptane aqua of the iodine is at 520 nm, joining along with the pyridine, this waveband intensity descends gradually, and drive a new, absorption to compare with the 520 nm waveband, the intensity of light is big and the peak shape is similar to replace, the position of peak is 422nm.This kind of phenomenon was called as "blue move"of the iodine waveband by Mulliken, and explained the substance of "blue move"waveband. The assumption is that an electron in excited state of complex transfer from donor to acceptor iodine molecule, the electronics entered the anti-tie orbit of the iodine and increased the valid size of the iodine molecule, after absorbed the light, rejecting for donor and abnormally big iodine molecule can increase consumedly excited energy which normal kindling need, donor and contact of the iodine molecule near to each other, thus "blue move"should be more obvious. We still made use of the continuous variety method to verify the pyridine and the iodine for 1:1 constitute of complex. The pyridine is the most simplest the donor molecule holding πand n electron, based on spectroscopy and the thermodynamics, because the electricity negative of the nitrogen atom is bigger than the carbon atom, make electronic cloud within total yoke system which incline toward the nitrogen atom. The complex of pyridine and iodine is a nitrogen atom to provide the solitary electron within the pyridine, namely the pyridine is not πdonor, but the n donor. the importance of the complex of the iodine and pyridine lie in that it can be theopposite and stable n-complex when it complex with the iodine. Therefore, many author research its property, particularly its formation constant. We go into three thermodynamics parameters of other in addition to the formation constant k .According to the equation of Scott, applying the least square to processing datum; acquire the precision value of the thermodynamics parameter. By measuring thermodynamics parameter, the further study pyridine and iodine complex, how the nitrogen atom in the pyridine molecule affect this kind of Lewis acidity quality of the iodine molecule. Because the aqua of pyridine below 300nm has the absorption, so the iodine has, this zone is the scope of the absorption spectrum forming the complex. For deducting donor and acceptor itself interference, in order to accurately measure the absorption spectrum of the pyridine and the iodine charge transfer complex, we use the aqua of pyridine of the same density to make reference, measuring the biggest absorption wavelength of complex in 190～350 nm. we may relatively clear know the electronic structure of complex of the pyridine and the iodine and know well by this characteristic peak, along with the increment of the density of pyridine, the charge transfer waveband did not appear, but appear very greatly "empty", at the same time, the vibration structure of the pyridine did not disappear in the around 203 nm. This is probably because: a. the vibration structure of the donor appear in the spectrum is because the donor absorb haven't been offset completely; b. the absorption spectrum of complex appear "empty"possibility because donor in the reference is superfluous. If continue to increase the density of the pyridine "blue move", wave-length moves toward short-wave, and end attain to the most value 373 nm and no longer...