Chemiluminescence during thermolysis of fullerene C60 derivatives containing reactive oxygen

Abstract

Chemiluminescence (CL) of fullerenes was first de tected in the ozonolysis of C 60 solutions 1,2 and later in the oxidation of sodium fullerides with a Ce IV complex. 3 In this work, a new type of the CL of fullerenes was observed during the thermolysis of complex C 60 oxides (1) formed by the ozonolysis of C 60 solutions and containing reac tive oxygen (RO) 4 and epoxide, 5 carbonyl, 6,7 and ester groups. 7 Earlier, 8,9 chemiluminescence in the thermoly sis of organic peroxides was reported. Chemiluminescence was measured by a known method. 2 The starting oxide 1 was prepared as a brown precipitate according to a known procedure 7 by the ozonolysis of C 60 solutions in CCl 4 (1.4 mmol of O 3 h -1 , [C 60 ] 0 = 1.6•10 -4 mol L -1 , V = 20 mL). Heating of the suspension of 1 in CCl 4 (20 mL) results in CL with a kinetic peak at the fifth minute (I max = 2.5•10 9 photon s -1 mL -1 ) (Fig. 1). From the excitation of CL to its complete disappearance, the content of RO in the sample (determined by iodometric titration 2 ) decreases from 1.6•10 -4 mol to zero, while the contents of epoxide, carbonyl, and ester groups (deter mined according to a procedure 7 ) do not change notice ably. The energy of activation calculated from the linear plot of logI vs. 1/T is 17.3±1.4 kcal mol -1 . Thus, CL can be attributed to thermal cleavage of the O-O groups bound to the ozonolysis transformed framework of C 60 . 7 The CL spectrum is the same as the known 2 CL spectrum recorded during the ozonolysis of C 60 solutions (see Fig. 1); i.e., in the thermolysis of 1, the emitter of CL is also the >C=O* group bound to the framework of C 60 . The CL excitation scheme can be represented only in the most general form {O-O}[C 60 ] → {*O=C}[C 60 ] → {O=C}[C 60 ] + hν (λ max = 680 nm) ([C 60 ] is the ozonolysis transformed framework of C 60 also including the epoxide, carbonyl, and ester groups), because the nature of RO in oxide 1 has not yet been specified: ozonide, peroxide, or bisperoxide forms are possible. 4

Formation of secondary fullerene ozonides in the ozonolysis of C60 solutions and chemiluminescence upon their hydrolysis

“…5,6 First, they are not retained during several months, as mentioned in Refs 5 and 6, but decompose completely by moisture traces during ~20 h. In addition, they de compose on heating not at 573 K 5,6 but already at 343-353 K. 32 Second, no SFOs are observed by iodo metric titration of the precipitate obtained after CCl 4 re moval by evacuation of a suspension of the solid ozonoly sis products of C 60 . No chemiluminescence is either ob served upon water addition to this precipitate.…”