Solvent effect of 2-(phenylazo)pyridine and their derivatives on absorption and emission spectra
การศึกษาผลของตัวทำละลายที่มีต่อการดูดกลืนแสงและการเปล่งแสงของ 2-(phenylazo)
pyridine และอนุพันธ์
Kanidtha Hansongnern, D. of Chemistry, F. of Sci., PSU.
Sriwipha Onganusorn, Graduate Student, D. of Chemistry, F. of Sci., PSU.
Corresponding e-mail : hkanidth@ratree.psu.ac.th
Grant : TRF and Postgraduate Educaion and Research Program in Chemistry
Presented : The 26th Congress on Science and Technology of Thailand, 18-20 October 2000,
Bangkok
Key words : emission, fluorescence and the lowest singlet excited state
2-(p-dimethylaminophenylazo)pyridine (dmazpy) and 2-(p-diethylaminophenylazo)pyridine (deazpy) which are the derivatives of 2-(phenylazo)pyridine (azpy), are azo compounds. All compounds contain p-electron system. Absorption spectra of azpy in various solvents show intense bands in UV region which are assigned to be p, p* transition. Meanwhile, bands in visible region are as-
signed to be n,p* transition. Because the substitutuents -N(CH3)2 and -N(C2H5)2 at para position are electron donating groups, this give rise to the shift of absorption band in visible region. Only deazpy shows emission spectra in different solvent. It is found that the emission wavelength depends on
solvent polarity. If solvent polarity increases, the emission wavelengths shift to the lower energy.
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