Synthesis and hypochromic effect of phthalocyanines and metal phthalocyanines

Several series of phthalocyanines (Pcs) and metallophthalocyanines (MPcs) were prepared and characterized by MS, 1H NMR, UV–vis and elemental analysis, which were consistent with the proposed structures. These Pcs and their metal complexes are synthesized using 3-(2-isopropyl-5-methylphenoxyl)phthalonitrile or 4-(2-isopropyl-5-methylphenoxyl)phthalonitrile as the starting material in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU) as the catalyst. An original UV–vis absorption investigation of these compounds is performed. Obvious hypochromic effect of Q-bands was found with the increment of temperature from 293 K to 333 K. B-bands did not show the analogous tendency. The hypochromic effect originates from conversion of Pc framework as a result of thermal vibration, which reduces the localization of π-electron system.