Journal of Photochemistry and Photobiology A: Chemistry 150 (2002) 41–48 Photodecomposition of molybdenum(II) and tungsten(II) carbonyl complexes with triazole, benz-imidazole, and oxadiazole acetylinic derivatives Salah A. Naman a , Ayad H. Jassim b,∗ , Mahasin F. Alias a a Chemistry Department, College of Education for Women, University of Baghdad, Baghdad, Iraq b Chemistry Department, College of Science, Saddam University, Baghdad, Iraq Received 2 June 2001; received in revised form 5 January 2002; accepted 31 January 2002 Abstract Photodecomposition of 10 different molybdenum and tungsten mixed carbonyl complexes, [M(CO) 3 (B)(A)]I 2 where B = o-phenanthro- line or bipyridyl, A = 3-(2-propynyl)thio-4,5-diphenyl-4H-1,2,4-triazole (TRZA) or S-propynyl-2-thio benz-imidazole (BIMDA) and 2(2-propynyl-thio(5-phenyl)-1,3,4-oxadiazole (OXA). M(CO) 3 (TRZA)I 2 , [M(CO) 2 (PPh 3 ) X (TRZA)I Y ]I Z where M = Mo, X, Y and Z = 1 and M = W, X and Z = 2, Y = 0, have been performed at 365 nm in oxygen saturated chloroform at 25 ◦ C. The absorbance spectrum of these complexes have been recorded with the time of irradiation in order to examine the kinetics of photodecay. The apparent rate constant (K d ) for the first-order reaction have been calculated and found to be (3.32–4.79) × 10 -5 s -1 . The primary quantum yields (Φ) has also been calculated and were in the range (8.33–12.1) ×10 -4 . The mechanism of the photodecomposition has been suggested according to the kinetic, and photoproduct analysis data, and is similar to reaction of photo-oxidative degradation of polluted molecules in the water. © 2002 Published by Elsevier Science B.V. Keywords: Photodecomposition; Molybdenum; Tungsten; Carbonyl complexes 1. Introduction Metal carbonyl complexes are among the most pho- toreactive transition metal complexes known [1]. Metal carbonyls are numerous [2] and have studied the excited state processes and photoprocess including electronic en- ergy phenomena [1,2]. Transition metal carbonyl complexes have been the object of photochemical investigations in- cluding group VIB metals. At the present time, correlations between electronic structures and reactivity are in primi- tive stages of development, therefore the organization of material is according to the central metal involved [2–4]. It appears that there is no definitive data to show that either photo-oxidation or photoreduction of primary photoprocess upon UV or visible excitation [2,4]. One has to consider reactions involving CO and a ligand. An emerging class of photoreactions of metal carbonyls is the fragmentation reaction of clusters as indicated in Eq. (1), and photo-oxidation of metal carbonyls to fragmentation as in Eq. (2) [5,6]: [M(CO) X ] n hν → M(CO) X + [M(CO) X ] n-1 (1) ∗ Corresponding author. M(CO) n L hν → [O] M X O Y + CO + ligand degradation to stable ions (2) According to the electronic spectra of the excited states of these molecules, it can be seen that these contain a number of transitions in the visible region associated with ligand field, metal ligand charge transfer, ligand metal charge transfer absorptions, the intensity and wavelength depend on the type of metal atom and ligand [7,8]. In this work we used the following mixed ligand carbonyl complexes as examples for studying the photodegradation in the chloroform solvent. Some metal carbonyl complexes may be used for the fol- lowing applications: 1. photochemical conversion and storage of solar energy, as photosensitizer in hydrogen production from water split- ting [9]; 2. photo-oxidation degradation of complexes [5]; 3. photoinitiation of polymerization cross-linking of poly- mers [10,11]; 4. photostabilization of polymers, and photoinduces for polymer degradation [12]; 5. photocatalysts for organic synthesis [13–15a]; 6. gasoline octane number improver [15b]. 1010-6030/02/$ – see front matter © 2002 Published by Elsevier Science B.V. PII:S1010-6030(02)00033-3