Spectrochimica Acta Part A 53 (1997) 2679 – 2684 UV-visible absorption spectra and luminescence of the pesticide fenarimol M. Conceic ¸a ˜o b , D.A. Mateus a, *, Abı ´lio M. da Silva a , Hugh D. Burrows b a UCEH, Uniersidade do Algare 8000 Faro, Portugal b Departamento de Quı ´mica, Uniersidade de Coimbra, 3049 Coimbra, Portugal Received 28 April 1997; received in revised form 6 June 1997; accepted 26 June 1997 Abstract The UV-visible absorption and emission spectra have been measured of the pesticide fenarimol (( )-2,4-dichloro-  -(pyrimidin-5-yl)-benzhydryl alcohol) in solution. From comparison with the spectra of chlorotoluenes and pyrim- idine, and from the effect of solvent polarity on the absorption spectrum, it is shown that the lowest excited singlet state is localized on the pyrimidine ring, and has n, * character. Higher excited , * states are localized on both chlorotoluene and pyrimidine rings. Fenarimol shows a weak, fluorescence from the n, * state, with a quantum yield which is strongly dependent on solvent. It is shown that this is due to changes in the nonradiative decay rate, particularly in protic solvents, due to increased intersystem crossing. Phosphorescence is observed in low temperature glasses. Although this shows two decay components, it is suggested that only one triplet state is involved, and that this has predominantly , * character. © 1997 Elsevier Science B.V. Keywords: Luminescence; Pesticide fenarimol; UV-visible absorption 1. Introduction The fungicide fenarimol (( )-2,4-dichloro- - (pyrimidin-5-yl)benzhydryl alcohol, I) is exten- sively used for spraying fruit and ornamental plants [1]. However, in spite of its widespread use, spectroscopic data on this compound is rather limited. The compound is photochemically un- stable, and is readily broken down by sunlight [1]. In a previous report [2] we presented some prelim- inary data on the spectral and photophysical prop- erties of this compound, together with tentative assignments of the photogradation products. We suggested that photodegradation probably pro- ceeds through the lowest excited singlet state, and that this has predominantly n, * character. To obtain further information on the excited elec- tronic states of fenarimol we have carried out more detailed spectroscopic and photophysical studies, with particular interest in the effect of solvent. * Corresponding author. Fax: +351 89 818560; e-mail: mcmateus@mozart.si.ualg.pt 1386-1425/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PII S1386-1425(97)00182-0