ABSTRACT:The reaction of styrene with phenol using photoacid catalyst has been investigated. Upon irradiation with 450 nm light, protonated merocyanine photoacid converts into spiropyran form with releasing proton. The reaction of styrene with phenol has been conducted under irradiation with 450 nm light using merocyanine photoacid catalyst at room temperature in comparison with the results using some selected catalysts including H 2 SO 4 or FeCl 3 at the reaction temperature of 120 o C.Sterically hindered phenols are effective inhibitors of free-radical processes and light stabilizers.

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The development of chemosensors for the recognition and sensing of various metal cations, 1-6 proton, 6-9 and some anions 10-13 has drawn intense attention due to their crucial effects in many environmental, clinical, and biological processes.Molecules that change color or fluorescence properties by changing the structure when metal cations and anions are added can be applied as good chemosensors. The structural interconversions could occur in response to a variety of the stimuli such as light, 14 heat, 15 mechanical forces, 16,17 or pH 6-9 as well as metal cations 1-6 and anions. [10][11][12][13] Fe 3+ is the physiologically most abundant and the most essential metal ion in biological systems. 3,18 It is very crucial in many biochemical processes, such as oxygen transport, cellular metabolism, cofactor in enzymatic reactions, and transcriptional regulation. Both its deficiency and excess can induce biological disorders, such as Alzheimer's disease, Parkinson's disease, anemia, diabetes, damage of liver and kidney, and heart failure.CN − is widely used in synthetic fibers, plastics, herbicides, photographic applications, and the gold-extraction process. [19][20][21] It is also widely found in nature such as plants and fruit seeds. However, CN − is extremely toxic to living organisms including humans and causes vomiting, convulsion, loss of consciousness, and eventual death.pH monitoring is very important in biological, medical, chemical, industrial, and environmental areas. [6][7][8][9] The development of colorimetric and fluorescent chemosensors for the sensitive and accurate detection of Fe 3+ , CN − , and pH is a challenging task.Fluorescent chemosensors are especially attractive because fluorescence is a simple, convenient, fast, and highly sensitive analytical tool. 1,2,4,11,12,18,20 A fluorescent chemosensor is composed of a fluorescent dye and a receptor. Recognition by a receptor moiety is converted to a change of fluorescence from a fluorescent dye.Among a number of organic dyes, rhodamine (Rh) dyes have attracted a great interest in recent years, due to their photostability, strong absorption, and fluorescence in the visible region. 3,18,21,22 The structure of rhodamine is converted from the spirolactam ring-closed (c-Rh) form to ring-opened form (o-Rh) by the addition of metal cations. Rhodamine with spirolactam ring (c-Rh) is colorless and nonfluorescent, while its ring-opened amide form (o-Rh) displays a pink color and strong orange fluorescence. Rhodamine derivatives have been extensively studied as colorimetric and fluorescent chemosensors capable of visually detecting various metal cations, utilizing significant changes in color and/or fluorescence in the presence of specific metal ion.Due to their remarkable stimuli-responsive nature, spiropyrans have also been extensively studied for use in chemosensors. 7,8 Spiropyran is a typical photochromic compound reversibly interconverting between the ring-closed colorless spiropyran (SP) form and the ring-open colored merocyanine (MC) form. Under UV ligh...